[llvm-commits] CVS: llvm-www/releases/1.2/docs/AliasAnalysis.html CFEBuildInstrs.html CodingStandards.html CommandLine.html Debugging.gif FAQ.html GettingStarted.html HowToSubmitABug.html LLVMVsTheWorld.html LangRef.html Makefile ObjectFiles.html OpenProjects.html ProgrammersManual.html Projects.html RegisterAllocatorInfo.txt ReleaseNotes.html SourceLevelDebugging.html Stacker.html TableGenFundamentals.html TestingGuide.html WritingAnLLVMPass.html doxygen.cfg doxygen.css doxygen.footer doxygen.header doxygen.intro index.html llvm.css venusflytrap.jpg
John Criswell
criswell at cs.uiuc.edu
Fri Mar 19 11:39:12 PST 2004
Changes in directory llvm-www/releases/1.2/docs:
AliasAnalysis.html added (r1.1)
CFEBuildInstrs.html added (r1.1)
CodingStandards.html added (r1.1)
CommandLine.html added (r1.1)
Debugging.gif added (r1.1)
FAQ.html added (r1.1)
GettingStarted.html added (r1.1)
HowToSubmitABug.html added (r1.1)
LLVMVsTheWorld.html added (r1.1)
LangRef.html added (r1.1)
Makefile added (r1.1)
ObjectFiles.html added (r1.1)
OpenProjects.html added (r1.1)
ProgrammersManual.html added (r1.1)
Projects.html added (r1.1)
RegisterAllocatorInfo.txt added (r1.1)
ReleaseNotes.html added (r1.1)
SourceLevelDebugging.html added (r1.1)
Stacker.html added (r1.1)
TableGenFundamentals.html added (r1.1)
TestingGuide.html added (r1.1)
WritingAnLLVMPass.html added (r1.1)
doxygen.cfg added (r1.1)
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doxygen.intro added (r1.1)
index.html added (r1.1)
llvm.css added (r1.1)
venusflytrap.jpg added (r1.1)
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Log message:
Initial commit of LLVM 1.2 documents.
Now that I've got them committed, I'll find something wrong.
:)
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Diffs of the changes: (+17989 -0)
Index: llvm-www/releases/1.2/docs/AliasAnalysis.html
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>Alias Analysis Infrastructure in LLVM</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">
+ Alias Analysis Infrastructure in LLVM
+ </div>
+
+ <ol>
+ <li><a href="#introduction">Introduction</a></li>
+
+ <li><a href="#overview">AliasAnalysis Overview</a>
+ <ul>
+ <li><a href="#pointers">Representation of Pointers</a></li>
+ <li><a href="#MustMayNo">Must, May, and No Alias Responses</a></li>
+ <li><a href="#ModRefInfo">The <tt>getModRefInfo</tt> methods</a></li>
+ </ul></li>
+
+ <li><a href="#writingnew">Writing a new AliasAnalysis Implementation</a>
+ <ul>
+ <li><a href="#passsubclasses">Different Pass styles</a></li>
+ <li><a href="#requiredcalls">Required initialization calls</a></li>
+ <li><a href="#interfaces">Interfaces which may be specified</a></li>
+ <li><a href="#chaining">The AliasAnalysis chaining behavior</a></li>
+ <li><a href="#implefficiency">Efficiency Issues</a></li>
+ </ul></li>
+
+ <li><a href="#using">Using AliasAnalysis results</a>
+ <ul>
+ <li><a href="#loadvn">Using the <tt>-load-vn</tt> Pass</a></li>
+ <li><a href="#ast">Using the <tt>AliasSetTracker</tt> class</a></li>
+ <li><a href="#direct">Using the AliasAnalysis interface directly</a></li>
+ </ul></li>
+
+ <li><a href="#tools">Helpful alias analysis related tools</a>
+ <ul>
+ <li><a href="#no-aa">The <tt>-no-aa</tt> pass</a></li>
+ <li><a href="#print-alias-sets">The <tt>-print-alias-sets</tt> pass</a></li>
+ <li><a href="#count-aa">The <tt>-count-aa</tt> pass</a></li>
+ <li><a href="#aa-eval">The <tt>-aa-eval</tt> pass</a></li>
+ </ul></li>
+ </ol>
+
+ <div class="doc_text">
+ <p><b>Written by <a href="mailto:sabre at nondot.org">Chris Lattner</a></b></p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="introduction">Introduction</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Alias Analysis (or Pointer Analysis) is a technique which attempts to
+ determine whether or not two pointers ever can point to the same object in
+ memory. Traditionally, Alias Analyses respond to a query with either a <a
+ href="#MustNoMay">Must, May, or No</a> alias response, indicating that two
+ pointers do point to the same object, might point to the same object, or are
+ known not to point to the same object.</p>
+
+ <p>The <a href="/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a> class is the
+ centerpiece of the LLVM Alias Analysis related infrastructure. This class is
+ the common interface between clients of alias analysis information and the
+ implementations providing it. In addition to simple alias analysis information,
+ this class exposes Mod/Ref information from those implementations which can
+ provide it, allowing for powerful analyses and transformations to work well
+ together.</p>
+
+ <p>This document contains information necessary to successfully implement this
+ interface, use it, and to test both sides. It also explains some of the finer
+ points about what exactly results mean. If you feel that something is unclear
+ or should be added, please <a href="mailto:sabre at nondot.org">let me
+ know</a>.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="overview">AliasAnalysis Overview</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>The <a href="/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a> class
+ defines the interface that Alias Analysis implementations should support. This
+ class exports two important enums: <tt>AliasResult</tt> and
+ <tt>ModRefResult</tt> which represent the result of an alias query or a mod/ref
+ query, respectively.</p>
+
+ <p>The AliasAnalysis interface exposes information about memory, represented in
+ several different ways. In particular, memory objects are represented as a
+ starting address and size, and function calls are represented as the actual
+ <tt>call</tt> or <tt>invoke</tt> instructions that performs the call. The
+ AliasAnalysis interface also exposes some helper methods which allow you to get
+ mod/ref information for arbitrary instructions.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="pointers">Representation of Pointers</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Most importantly, the AliasAnalysis class provides several methods which are
+ used to query whether or not pointers alias, whether function calls can modify
+ or read memory, etc.</p>
+
+ <p>Representing memory objects as a starting address and a size is critically
+ important for precise Alias Analyses. For example, consider this (silly) C
+ code:</p>
+
+ <pre>
+ int i;
+ char C[2];
+ char A[10];
+ /* ... */
+ for (i = 0; i != 10; ++i) {
+ C[0] = A[i]; /* One byte store */
+ C[1] = A[9-i]; /* One byte store */
+ }
+ </pre>
+
+ <p>In this case, the <tt>basicaa</tt> pass will disambiguate the stores to
+ <tt>C[0]</tt> and <tt>C[1]</tt> because they are accesses to two distinct
+ locations one byte apart, and the accesses are each one byte. In this case, the
+ LICM pass can use store motion to remove the stores from the loop. In
+ constrast, the following code:</p>
+
+ <pre>
+ int i;
+ char C[2];
+ char A[10];
+ /* ... */
+ for (i = 0; i != 10; ++i) {
+ ((short*)C)[0] = A[i]; /* Two byte store! */
+ C[1] = A[9-i]; /* One byte store */
+ }
+ </pre>
+
+ <p>In this case, the two stores to C do alias each other, because the access to
+ the <tt>&C[0]</tt> element is a two byte access. If size information wasn't
+ available in the query, even the first case would have to conservatively assume
+ that the accesses alias.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="MustMayNo">Must, May, and No Alias Responses</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>An Alias Analysis implementation can return one of three responses:
+ MustAlias, MayAlias, and NoAlias. The No and May alias results are obvious: if
+ the two pointers may never equal each other, return NoAlias, if they might,
+ return MayAlias.</p>
+
+ <p>The Must Alias response is trickier though. In LLVM, the Must Alias response
+ may only be returned if the two memory objects are guaranteed to always start at
+ exactly the same location. If two memory objects overlap, but do not start at
+ the same location, MayAlias must be returned.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="ModRefInfo">The <tt>getModRefInfo</tt> methods</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>getModRefInfo</tt> methods return information about whether the
+ execution of an instruction can read or modify a memory location. Mod/Ref
+ information is always conservative: if an action <b>may</b> read a location, Ref
+ is returned.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="writingnew">Writing a new AliasAnalysis Implementation</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Writing a new alias analysis implementation for LLVM is quite
+ straight-forward. There are already several implementations that you can use
+ for examples, and the following information should help fill in any details.
+ For a minimal example, take a look at the <a
+ href="/doxygen/structllvm_1_1NoAA.html"><tt>no-aa</tt></a> implementation.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="passsubclasses">Different Pass styles</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The first step to determining what type of <a
+ href="WritingAnLLVMPass.html">LLVM pass</a> you need to use for your Alias
+ Analysis. As is the case with most other analyses and transformations, the
+ answer should be fairly obvious from what type of problem you are trying to
+ solve:</p>
+
+ <ol>
+ <li>If you require interprocedural analysis, it should be a
+ <tt>Pass</tt>.</li>
+ <li>If you are a global analysis, subclass <tt>FunctionPass</tt>.</li>
+ <li>If you are a local pass, subclass <tt>BasicBlockPass</tt>.</li>
+ <li>If you don't need to look at the program at all, subclass
+ <tt>ImmutablePass</tt>.</li>
+ </ol>
+
+ <p>In addition to the pass that you subclass, you should also inherit from the
+ <tt>AliasAnalysis</tt> interface, of course, and use the
+ <tt>RegisterAnalysisGroup</tt> template to register as an implementation of
+ <tt>AliasAnalysis</tt>.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="requiredcalls">Required initialization calls</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Your subclass of AliasAnalysis is required to invoke two methods on the
+ AliasAnalysis base class: <tt>getAnalysisUsage</tt> and
+ <tt>InitializeAliasAnalysis</tt>. In particular, your implementation of
+ <tt>getAnalysisUsage</tt> should explicitly call into the
+ <tt>AliasAnalysis::getAnalysisUsage</tt> method in addition to doing any
+ declaring any pass dependencies your pass has. Thus you should have something
+ like this:</p>
+
+ <pre>
+ void getAnalysisUsage(AnalysisUsage &AU) const {
+ AliasAnalysis::getAnalysisUsage(AU);
+ <i>// declare your dependencies here.</i>
+ }
+ </pre>
+
+ <p>Additionally, your must invoke the <tt>InitializeAliasAnalysis</tt> method
+ from your analysis run method (<tt>run</tt> for a <tt>Pass</tt>,
+ <tt>runOnFunction</tt> for a <tt>FunctionPass</tt>, <tt>runOnBasicBlock</tt> for
+ a <tt>BasicBlockPass</tt>, or <tt>InitializeAliasAnalysis</tt> for an
+ <tt>ImmutablePass</tt>). For example (as part of a <tt>Pass</tt>):</p>
+
+ <pre>
+ bool run(Module &M) {
+ InitializeAliasAnalysis(this);
+ <i>// Perform analysis here...</i>
+ return false;
+ }
+ </pre>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="interfaces">Interfaces which may be specified</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>All of the <a href="/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>
+ virtual methods default to providing conservatively correct information
+ (returning "May" Alias and "Mod/Ref" for alias and mod/ref queries
+ respectively). Depending on the capabilities of the analysis you are
+ implementing, you just override the interfaces you can improve.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="chaining">The AliasAnalysis chaining behavior</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>With only two special exceptions (the <tt>basicaa</tt> and <a
+ href="#no-aa"><tt>no-aa</tt></a> passes) every alias analysis pass should chain
+ to another alias analysis implementation (for example, you could specify
+ "<tt>-basic-aa -ds-aa -andersens-aa -licm</tt>" to get the maximum benefit from
+ the three alias analyses). To do this, simply "Require" AliasAnalysis in your
+ <tt>getAnalysisUsage</tt> method, and if you need to return a conservative
+ MayAlias or Mod/Ref result, simply chain to a lower analysis.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="implefficiency">Efficiency Issues</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>From the LLVM perspective, the only thing you need to do to provide an
+ efficient alias analysis is to make sure that alias analysis <b>queries</b> are
+ serviced quickly. The actual calculation of the alias analysis results (the
+ "run" method) is only performed once, but many (perhaps duplicate) queries may
+ be performed. Because of this, try to move as much computation to the run
+ method as possible (within reason).</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="using">Using AliasAnalysis results</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>There are several different ways to use alias analysis results. In order of
+ preference, these are...</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="loadvn">Using the <tt>-load-vn</tt> Pass</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>load-vn</tt> pass uses alias analysis to provide value numbering
+ information for <tt>load</tt> instructions. If your analysis or transformation
+ can be modelled in a form that uses value numbering information, you don't have
+ to do anything special to handle load instructions: just use the
+ <tt>load-vn</tt> pass, which uses alias analysis.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="ast">Using the <tt>AliasSetTracker</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Many transformations need information about alias <b>sets</b> that are active
+ in some scope, rather than information about pairwise aliasing. The <tt><a
+ href="/doxygen/classllvm_1_1AliasSetTracker.html">AliasSetTracker</a></tt> class is used
+ to efficiently build these Alias Sets from the pairwise alias analysis
+ information provided by the AliasAnalysis interface.</p>
+
+ <p>First you initialize the AliasSetTracker by use the "<tt>add</tt>" methods to
+ add information about various potentially aliasing instructions in the scope you
+ are interested in. Once all of the alias sets are completed, your pass should
+ simply iterate through the constructed alias sets, using the AliasSetTracker
+ <tt>begin()</tt>/<tt>end()</tt> methods.</p>
+
+ <p>The <tt>AliasSet</tt>s formed by the <tt>AliasSetTracker</tt> are guaranteed
+ to be disjoint, calculate mod/ref information and volatility for the set, and
+ keep track of whether or not all of the pointers in the set are Must aliases.
+ The AliasSetTracker also makes sure that sets are properly folded due to call
+ instructions, and can provide a list of pointers in each set.</p>
+
+ <p>As an example user of this, the <a href="/doxygen/structLICM.html">Loop
+ Invariant Code Motion</a> pass uses AliasSetTrackers to build alias information
+ about each loop nest. If an AliasSet in a loop is not modified, then all load
+ instructions from that set may be hoisted out of the loop. If any alias sets
+ are stored <b>and</b> are must alias sets, then the stores may be sunk to
+ outside of the loop, promoting the memory location to a register for the
+ duration of the loop nest. Both of these transformations obviously only apply
+ if the pointer argument is loop-invariant.</p>
+
+ </div>
+
+ <div class="doc_subsubsection">
+ The AliasSetTracker implementation
+ </div>
+
+ <div class="doc_text">
+
+ <p>The AliasSetTracker class is implemented to be as efficient as possible. It
+ uses the union-find algorithm to efficiently merge AliasSets when a pointer is
+ inserted into the AliasSetTracker that aliases multiple sets. The primary data
+ structure is a hash table mapping pointers to the AliasSet they are in.</p>
+
+ <p>The AliasSetTracker class must maintain a list of all of the LLVM Value*'s
+ that are in each AliasSet. Since the hash table already has entries for each
+ LLVM Value* of interest, the AliasesSets thread the linked list through these
+ hash-table nodes to avoid having to allocate memory unnecessarily, and to make
+ merging alias sets extremely efficient (the linked list merge is constant time).
+ </p>
+
+ <p>You shouldn't need to understand these details if you are just a client of
+ the AliasSetTracker, but if you look at the code, hopefully this brief
+ description will help make sense of why things are designed the way they
+ are.</p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="direct">Using the AliasAnalysis interface directly</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>As a last resort, your pass could use the AliasAnalysis interface directly to
+ service your pass. If you find the need to do this, please <a
+ href="mailto:sabre at nondot.org">let me know</a> so I can see if something new
+ needs to be added to LLVM.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="tools">Helpful alias-analysis-related tools</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>If you're going to be working with the AliasAnalysis infrastructure, there
+ are several nice tools that may be useful for you and are worth knowing
+ about...</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="no-aa">The <tt>-no-aa</tt> pass</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>-no-aa</tt> analysis is just like what it sounds: an alias analysis
+ that never returns any useful information. This pass can be useful if you think
+ that alias analysis is doing something wrong and are trying to narrow down a
+ problem. If you don't specify an alias analysis, the default will be to use the
+ <tt>basicaa</tt> pass which does quite a bit of disambiguation on its own.</p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="print-alias-sets">The <tt>-print-alias-sets</tt> pass</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>-print-alias-sets</tt> pass is exposed as part of the
+ <tt>analyze</tt> tool to print out the Alias Sets formed by the <a
+ href="#ast"><tt>AliasSetTracker</tt></a> class. This is useful if you're using
+ the <tt>AliasSetTracker</tt>.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="count-aa">The <tt>-count-aa</tt> pass</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>-count-aa</tt> pass is useful to see how many queries a particular
+ pass is making and what kinds of responses are returned by the alias analysis.
+ An example usage is:</p>
+
+ <pre>
+ $ opt -basicaa -count-aa -ds-aa -count-aa -licm
+ </pre>
+
+ <p>Which will print out how many queries (and what responses are returned) by
+ the <tt>-licm</tt> pass (of the <tt>-ds-aa</tt> pass) and how many queries are
+ made of the <tt>-basicaa</tt> pass by the <tt>-ds-aa</tt> pass. This can be
+ useful when evaluating an alias analysis for precision.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="aa-eval">The <tt>-aa-eval</tt> pass</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>-aa-eval</tt> pass simply iterates through all pairs of pointers in a
+ function and asks an alias analysis whether or not the pointers alias. This
+ gives an indication of the precision of the alias analysis. Statistics are
+ printed.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+
+ <hr>
+ <address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
+
+ <a href="mailto:sabre at nondot.org">Chris Lattner</a><br>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </address>
+
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/CFEBuildInstrs.html
diff -c /dev/null llvm-www/releases/1.2/docs/CFEBuildInstrs.html:1.1
*** /dev/null Fri Mar 19 11:38:21 2004
--- llvm-www/releases/1.2/docs/CFEBuildInstrs.html Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,279 ----
+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
+ <html>
+ <head>
+ <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
+ <link rel="stylesheet" href="llvm.css" type="text/css" media="screen" />
+ <title>Bootstrapping the LLVM C/C++ Front-End</title>
+ </head>
+ <body>
+
+ <div class="doc_title">
+ Bootstrapping the LLVM C/C++ Front-End
+ </div>
+
+ <ol>
+ <li><a href="#cautionarynote">A Cautionary Note</a>
+ <li><a href="#instructions">Instructions</a>
+ <li><a href="#license">License Information</a>
+ </ol>
+
+ <div class="doc_text">
+ <p><b>Written by Brian R. Gaeke</b></p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="cautionarynote">A Cautionary Note</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+ <p>This document is intended to explain the process of building the
+ LLVM C/C++ front-end, based on GCC 3.4, from its source code. You
+ would have to do this, for example, if you are porting LLVM to a new
+ architecture or operating system.</p>
+
+ <p><b>NOTE:</b> This is currently a somewhat fragile, error-prone
+ process, and you should <b>only</b> try to do it if:</p>
+
+ <ol>
+ <li>you really, really, really can't use the binaries we distribute</li>
+ <li>you need GCC to fix some of the header files on your system</li>
+ <li>you are an elite GCC hacker.</li>
+ </ol>
+
+ <p>We welcome patches to help make this process simpler.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="instructions">Instructions</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+ <p>
+ <ol>
+ <li><p>Configure and build the LLVM libraries and tools using:</p>
+ <pre>
+ % cd llvm
+ % ./configure [options...]
+ % gmake tools-only
+ </pre>
+ <p>The use of the non-default target "tools-only" means that the
+ LLVM tools and libraries will build, and the binaries will be
+ deposited in llvm/tools/Debug, but the runtime (bytecode)
+ libraries will not build.</p></li>
+
+ <li><p>Add the directory containing the tools to your PATH.</p>
+ <pre>
+ % set path = ( `cd llvm/tools/Debug && pwd` $path )
+ </pre></li>
+
+ <li><p>Unpack the C/C++ front-end source into cfrontend/src.</p></li>
+
+ <li><p>Edit src/configure. Change the first line (starting w/ #!) to
+ contain the correct full pathname of sh.</p></li>
+
+ <li><p>Make "build" and "install" directories as siblings of the "src"
+ tree.</p>
+ <pre>
+ % pwd
+ /usr/local/example/cfrontend/src
+ % cd ..
+ % mkdir build install
+ % set CFEINSTALL = `pwd`/install
+ </pre></li>
+
+ <li><p>Configure, build, and install the C front-end:</p>
+
+ <p>
+ <b>Linux/x86:</b>
+ <br>
+ <b>MacOS X/PowerPC:</b>
+ </p>
+
+ <pre>
+ % cd build
+ % ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls --disable-shared \
+ --enable-languages=c,c++
+ % gmake all-gcc
+ % setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc
+ % gmake all; gmake install
+ </pre>
+
+ <p>
+ <b>Solaris/SPARC:</b>
+ </p>
+
+ <p>
+ For Solaris/SPARC, LLVM only supports the SPARC V9. Therefore, the
+ configure command line should specify sparcv9, as shown below. Also,
+ note that Solaris has trouble with various wide (multibyte) character
+ functions from C as referenced from C++, so we typically configure with
+ --disable-c-mbchar (cf. <a href="http://llvm.cs.uiuc.edu/PR206">Bug 206</a>).
+ </p>
+
+ <pre>
+ % cd build
+ % ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
+ --disable-shared --enable-languages=c,c++ --host=sparcv9-sun-solaris2.8 \
+ --disable-c-mbchar
+ % gmake all-gcc
+ % setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc
+ % gmake all; gmake install
+ </pre>
+
+ <p><b>Common Problem:</b> You may get error messages regarding the fact
+ that LLVM does not support inline assembly. Here are two common
+ fixes:</p>
+
+ <ul>
+ <li><p><b>Fix 1:</b> If you have system header files that include
+ inline assembly, you may have to modify them to remove the inline
+ assembly, and install the modified versions in
+ <code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code>.</p></li>
+
+ <li><b>Fix 2:</b> If you are building the C++ front-end on a CPU we
+ haven't tried yet, you will probably have to edit the appropriate
+ version of atomicity.h under
+ <code>src/libstdc++-v3/config/cpu/<i>name-of-cpu</i>/atomicity.h</code>
+ and apply a patch so that it does not use inline assembly.</p></li>
+ </ul>
+
+ <p><b>Porting to a new architecture:</b> If you are porting the new front-end
+ to a new architecture, or compiling in a different configuration that we have
+ previously, there are probably several changes you will have to make to the GCC
+ target to get it to work correctly. These include:<p>
+
+ <ul>
+ <li>Often targets include special or assembler linker flags which
+ <tt>gccas</tt>/<tt>gccld</tt> does not understand. In general, these can
+ just be removed.</li>
+ <li>LLVM currently does not support any floating point values other than
+ 32-bit and 64-bit IEEE floating point. The primary effect of this is
+ that you may have to map "long double" onto "double".</li>
+ <li>The profiling hooks in GCC do not apply at all to the LLVM front-end.
+ These may need to be disabled.</li>
+ <li>No inline assembly for position independent code. At the LLVM level,
+ everything is position independent.</li>
+ <li>We handle <tt>.init</tt> and <tt>.fini</tt> differently.</li>
+ <li>You may have to disable multilib support in your target. Using multilib
+ support causes the GCC compiler driver to add a lot of "<tt>-L</tt>"
+ options to the link line, which do not relate to LLVM and confuse
+ <tt>gccld</tt>. To disable multilibs, delete any
+ <tt>MULTILIB_OPTIONS</tt> lines from your target files.</li>
+ <li>Did we mention that we don't support inline assembly? You'll probably
+ have to add some fixinclude hacks to disable it in the system
+ headers.</li>
+ </ul>
+ </li>
+
+ <li><p>Go back into the LLVM source tree proper. Edit Makefile.config
+ to redefine <code>LLVMGCCDIR</code> to the full pathname of the
+ <code>$CFEINSTALL</code> directory, which is the directory you just
+ installed the C front-end into. (The ./configure script is likely to
+ have set this to a directory which does not exist on your system.)</p></li>
+
+ <li><p>If you edited header files during the C/C++ front-end build as
+ described in "Fix 1" above, you must now copy those header files from
+ <code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code> to
+ <code>$CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm/include</code>.
+ (This should be the "include" directory in the same directory as the
+ libgcc.a library, which you can find by running
+ <code>$CFEINSTALL/bin/gcc --print-libgcc-file-name</code>.)</p></li>
+
+ <li><p>Build and install the runtime (bytecode) libraries by running:</p>
+ <pre>
+ % gmake -C runtime
+ % mkdir $CFEINSTALL/bytecode-libs
+ % gmake -C runtime install-bytecode
+ % setenv LLVM_LIB_SEARCH_PATH $CFEINSTALL/bytecode-libs
+ </pre></li>
+
+ <li><p>Test the newly-installed C frontend by one or more of the
+ following means:</p>
+ <ul>
+ <li> compiling and running a "hello, LLVM" program in C and C++.</li>
+ <li> running the tests under <tt>test/Programs</tt> using <code>gmake -C
+ test/Programs</code></li>
+ </ul>
+ </p>
+ </li>
+ </ol>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="license">License Information</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ The LLVM GCC frontend is licensed to you under the GNU General Public License
+ and the GNU Lesser General Public License. Please see the files COPYING and
+ COPYING.LIB for more details.
+ </p>
+
+ <p>
+ The software also has the following additional copyrights:
+ </p>
+
+ <pre>
+
+ Copyright (c) 2003, 2004 University of Illinois at Urbana-Champaign.
+ All rights reserved.
+
+ Developed by:
+
+ LLVM Team
+
+ University of Illinois at Urbana-Champaign
+
+ http://llvm.cs.uiuc.edu
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
+ SOFTWARE.
+
+ Copyright (c) 1994
+ Hewlett-Packard Company
+
+ Permission to use, copy, modify, distribute and sell this software
+ and its documentation for any purpose is hereby granted without fee,
+ provided that the above copyright notice appear in all copies and
+ that both that copyright notice and this permission notice appear
+ in supporting documentation. Hewlett-Packard Company makes no
+ representations about the suitability of this software for any
+ purpose. It is provided "as is" without express or implied warranty.
+
+ Copyright (c) 1996, 1997, 1998, 1999
+ Silicon Graphics Computer Systems, Inc.
+
+ Permission to use, copy, modify, distribute and sell this software
+ and its documentation for any purpose is hereby granted without fee,
+ provided that the above copyright notice appear in all copies and
+ that both that copyright notice and this permission notice appear
+ in supporting documentation. Silicon Graphics makes no
+ representations about the suitability of this software for any
+ purpose. It is provided "as is" without express or implied warranty.
+ </pre>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <!-- *********************************************************************** -->
+
+ <hr>
+ <div class="doc_footer">
+ <address>Brian Gaeke</address>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </div>
+
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/CodingStandards.html
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ <title>A Few Coding Standards</title>
+ </head>
+ <body>
+
+ <div class="doc_title">
+ A Few Coding Standards
+ </div>
+
+ <ol>
+ <li><a href="#introduction">Introduction</a></li>
+ <li><a href="#mechanicalissues">Mechanical Source Issues</a>
+ <ol>
+ <li><a href="#sourceformating">Source Code Formatting</a>
+ <ol>
+ <li><a href="#scf_commenting">Commenting</a></li>
+ <li><a href="#scf_commentformat">Comment Formatting</a></li>
+ <li><a href="#scf_includes">#include Style</a></li>
+ <li><a href="#scf_codewidth">Source Code Width</a></li>
+ <li><a href="#scf_spacestabs">Use Spaces Instead of Tabs</a></li>
+ <li><a href="#scf_indentation">Indent Code Consistently</a></li>
+ </ol></li>
+ <li><a href="#compilerissues">Compiler Issues</a>
+ <ol>
+ <li><a href="#ci_warningerrors">Treat Compiler Warnings Like
+ Errors</a></li>
+ <li><a href="#ci_cpp_features">Which C++ features can I use?</a></li>
+ <li><a href="#ci_portable_code">Write Portable Code</a></li>
+ </ol></li>
+ </ol></li>
+ <li><a href="#styleissues">Style Issues</a>
+ <ol>
+ <li><a href="#macro">The High Level Issues</a>
+ <ol>
+ <li><a href="#hl_module">A Public Header File <b>is</b> a
+ Module</a></li>
+ <li><a href="#hl_dontinclude">#include as Little as Possible</a></li>
+ <li><a href="#hl_privateheaders">Keep "internal" Headers
+ Private</a></li>
+ </ol></li>
+ <li><a href="#micro">The Low Level Issues</a>
+ <ol>
+ <li><a href="#hl_assert">Assert Liberally</a></li>
+ <li><a href="#hl_preincrement">Prefer Preincrement</a></li>
+ <li><a href="#hl_avoidendl">Avoid endl</a></li>
+ <li><a href="#hl_exploitcpp">Exploit C++ to its Fullest</a></li>
+ </ol></li>
+ <li><a href="#iterators">Writing Iterators</a></li>
+ </ol></li>
+ <li><a href="#seealso">See Also</a></li>
+ </ol>
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="introduction">Introduction</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This document attempts to describe a few coding standards that are being used
+ in the LLVM source tree. Although no coding standards should be regarded as
+ absolute requirements to be followed in all instances, coding standards can be
+ useful.</p>
+
+ <p>This document intentionally does not prescribe fixed standards for religious
+ issues such as brace placement and space usage. For issues like this, follow
+ the golden rule:</p>
+
+ <blockquote>
+
+ <p><b><a name="goldenrule">If you are adding a significant body of source to a
+ project, feel free to use whatever style you are most comfortable with. If you
+ are extending, enhancing, or bug fixing already implemented code, use the style
+ that is already being used so that the source is uniform and easy to
+ follow.</a></b></p>
+
+ </blockquote>
+
+ <p>The ultimate goal of these guidelines is the increase readability and
+ maintainability of our common source base. If you have suggestions for topics to
+ be included, please mail them to <a
+ href="mailto:sabre at nondot.org">Chris</a>.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="mechanicalissues">Mechanical Source Issues</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="sourceformating">Source Code Formatting</a>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="scf_commenting">Commenting</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Comments are one critical part of readability and maintainability. Everyone
+ knows they should comment, so should you. :) Although we all should probably
+ comment our code more than we do, there are a few very critical places that
+ documentation is very useful:</p>
+
+ <ol>
+ <li><h4>File Headers</h4>
+
+ <p>Every source file should have a header on it that
+ describes the basic purpose of the file. If a file does not have a header, it
+ should not be checked into CVS. Most source trees will probably have a standard
+ file header format. The standard format for the LLVM source tree looks like
+ this:</p>
+
+ <pre>
+ //===-- llvm/Instruction.h - Instruction class definition -------*- C++ -*-===//
+ //
+ // This file contains the declaration of the Instruction class, which is the
+ // base class for all of the VM instructions.
+ //
+ //===----------------------------------------------------------------------===//
+ </pre>
+
+ <p>A few things to note about this particular format. The "<tt>-*- C++
+ -*-</tt>" string on the first line is there to tell Emacs that the source file
+ is a C++ file, not a C file (Emacs assumes .h files are C files by default [Note
+ that tag this is not necessary in .cpp files]). The name of the file is also on
+ the first line, along with a very short description of the purpose of the file.
+ This is important when printing out code and flipping though lots of pages.</p>
+
+ <p>The main body of the description does not have to be very long in most cases.
+ Here it's only two lines. If an algorithm is being implemented or something
+ tricky is going on, a reference to the paper where it is published should be
+ included, as well as any notes or "gotchas" in the code to watch out for.</p>
+
+ </li>
+
+ <li><h4>Class overviews</h4>
+
+ <p>Classes are one fundemental part of a good object oriented design. As such,
+ a class definition should have a comment block that explains what the class is
+ used for... if it's not obvious. If it's so completely obvious your grandma
+ could figure it out, it's probably safe to leave it out. Naming classes
+ something sane goes a long ways towards avoiding writing documentation. :)</p>
+
+ </li>
+
+ <li><h4>Method information</h4>
+
+ <p>Methods defined in a class (as well as any global functions) should also be
+ documented properly. A quick note about what it does any a description of the
+ borderline behaviour is all that is necessary here (unless something
+ particularly tricky or insideous is going on). The hope is that people can
+ figure out how to use your interfaces without reading the code itself... that is
+ the goal metric.</p>
+
+ <p>Good things to talk about here are what happens when something unexpected
+ happens: does the method return null? Abort? Format your hard disk?</p>
+
+ </li>
+ </ol>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="scf_commentformat">Comment Formatting</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>In general, prefer C++ style (<tt>//</tt>) comments. They take less space,
+ require less typing, don't have nesting problems, etc. There are a few cases
+ when it is useful to use C style (<tt>/* */</tt>) comments however:</p>
+
+ <ol>
+ <li>When writing a C code: Obviously if you are writing C code, use C style
+ comments. :)</li>
+ <li>When writing a header file that may be #included by a C source file.</li>
+ <li>When writing a source file that is used by a tool that only accepts C
+ style comments.</li>
+ </ol>
+
+ <p>To comment out a large block of code, use <tt>#if 0</tt> and <tt>#endif</tt>.
+ These nest properly and are better behaved in general than C style comments.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="scf_includes">#include Style</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Immediately after the <a href="#scf_commenting">header file comment</a> (and
+ include guards if working on a header file), the <a
+ href="hl_dontinclude">minimal</a> list of #includes required by the file should
+ be listed. We prefer these #includes to be listed in this order:</p>
+
+ <ol>
+ <li><a href="#mmheader">Main Module header</a></li>
+ <li><a href="#hl_privateheaders">Local/Private Headers</a></li>
+ <li>llvm/*</li>
+ <li>llvm/Analysis/*</li>
+ <li>llvm/Assembly/*</li>
+ <li>llvm/Bytecode/*</li>
+ <li>llvm/CodeGen/*</li>
+ <li>...</li>
+ <li>Support/*</li>
+ <li>Config/*</li>
+ <li>System #includes</li>
+ </ol>
+
+ <p>... and each catagory should be sorted by name.</p>
+
+ <p><a name="mmheader">The "Main Module Header"</a> file applies to .cpp file
+ which implement an interface defined by a .h file. This #include should always
+ be included <b>first</b> regardless of where it lives on the file system. By
+ including a header file first in the .cpp files that implement the interfaces,
+ we ensure that the header does not have any hidden dependencies which are not
+ explicitly #included in the header, but should be. It is also a form of
+ documentation in the .cpp file to indicate where the interfaces it implements
+ are defined.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="scf_codewidth">Source Code Width</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Write your code to fit within 80 columns of text. This helps those of us who
+ like to print out code and look at your code in an xterm without resizing
+ it.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="scf_spacestabs">Use Spaces Instead of Tabs</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>In all cases, prefer spaces to tabs in source files. People have different
+ prefered indentation levels, and different styles of indentation that they
+ like... this is fine. What isn't is that different editors/viewers expand tabs
+ out to different tab stops. This can cause your code to look completely
+ unreadable, and it is not worth dealing with.</p>
+
+ <p>As always, follow the <a href="#goldenrule">Golden Rule</a> above: follow the
+ style of existing code if your are modifying and extending it. If you like four
+ spaces of indentation, <b>DO NOT</b> do that in the middle of a chunk of code
+ with two spaces of indentation. Also, do not reindent a whole source file: it
+ makes for incredible diffs that are absolutely worthless.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="scf_indentation">Indent Code Consistently</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Okay, your first year of programming you were told that indentation is
+ important. If you didn't believe and internalize this then, now is the time.
+ Just do it.</p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="compilerissues">Compiler Issues</a>
+ </div>
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="ci_warningerrors">Treat Compiler Warnings Like Errors</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>If your code has compiler warnings in it, something is wrong: you aren't
+ casting values correctly, your have "questionable" constructs in your code, or
+ you are doing something legitimately wrong. Compiler warnings can cover up
+ legitimate errors in output and make dealing with a translation unit
+ difficult.</p>
+
+ <p>It is not possible to prevent all warnings from all compilers, nor is it
+ desirable. Instead, pick a standard compiler (like <tt>gcc</tt>) that provides
+ a good thorough set of warnings, and stick to them. At least in the case of
+ <tt>gcc</tt>, it is possible to work around any spurious errors by changing the
+ syntax of the code slightly. For example, an warning that annoys me occurs when
+ I write code like this:</p>
+
+ <pre>
+ if (V = getValue()) {
+ ..
+ }
+ </pre>
+
+ <p><tt>gcc</tt> will warn me that I probably want to use the <tt>==</tt>
+ operator, and that I probably mistyped it. In most cases, I haven't, and I
+ really don't want the spurious errors. To fix this particular problem, I
+ rewrite the code like this:</p>
+
+ <pre>
+ if ((V = getValue())) {
+ ..
+ }
+ </pre>
+
+ <p>...which shuts <tt>gcc</tt> up. Any <tt>gcc</tt> warning that annoys you can
+ be fixed by massaging the code appropriately.</p>
+
+ <p>These are the <tt>gcc</tt> warnings that I prefer to enable: <tt>-Wall
+ -Winline -W -Wwrite-strings -Wno-unused</tt></p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="ci_cpp_features">Which C++ features can I use?</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Compilers are finally catching up to the C++ standard. Most compilers
+ implement most features, so you can use just about any features that you would
+ like. In the LLVM source tree, I have chosen to not use these features:</p>
+
+ <ol>
+ <li><p>Exceptions: Exceptions are very useful for error reporting and handling
+ exceptional conditions. I do not use them in LLVM because they do have an
+ associated performance impact (by restricting restructuring of code), and parts
+ of LLVM are designed for performance critical purposes.</p>
+
+ <p>Just like most of the rules in this document, this isn't a hard and fast
+ requirement. Exceptions are used in the Parser, because it simplifies error
+ reporting <b>significantly</b>, and the LLVM parser is not at all in the
+ critical path.</p>
+ </li>
+
+ <li>RTTI: RTTI has a large cost in terms of executable size, and compilers are
+ not yet very good at stomping out "dead" class information blocks. Because of
+ this, typeinfo and dynamic cast are not used.</li>
+ </ol>
+
+ <p>Other features, such as templates (without partial specialization) can be
+ used freely. The general goal is to have clear, consise, performant code... if
+ a technique assists with that then use it.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="ci_portable_code">Write Portable Code</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>In almost all cases, it is possible and within reason to write completely
+ portable code. If there are cases where it isn't possible to write portable
+ code, isolate it behind a well defined (and well documented) interface.</p>
+
+ <p>In practice, this means that you shouldn't assume much about the host
+ compiler, including its support for "high tech" features like partial
+ specialization of templates. In fact, Visual C++ 6 could be an important target
+ for our work in the future, and we don't want to have to rewrite all of our code
+ to support it.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="styleissues">Style Issues</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="macro">The High Level Issues</a>
+ </div>
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="hl_module">A Public Header File <b>is</b> a Module</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>C++ doesn't do too well in the modularity department. There is no real
+ encapsulation or data hiding (unless you use expensive protocol classes), but it
+ is what we have to work with. When you write a public header file (in the LLVM
+ source tree, they live in the top level "include" directory), you are defining a
+ module of functionality.</p>
+
+ <p>Ideally, modules should be completely independent of each other, and their
+ header files should only include the absolute minimum number of headers
+ possible. A module is not just a class, a function, or a namespace: <a
+ href="http://www.cuj.com/articles/2000/0002/0002c/0002c.htm">it's a collection
+ of these</a> that defines an interface. This interface may be several
+ functions, classes or data structures, but the important issue is how they work
+ together.</p>
+
+ <p>In general, a module should be implemented with one or more <tt>.cpp</tt>
+ files. Each of these <tt>.cpp</tt> files should include the header that defines
+ their interface first. This ensure that all of the dependences of the module
+ header have been properly added to the module header itself, and are not
+ implicit. System headers should be included after user headers for a
+ translation unit.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="hl_dontinclude">#include as Little as Possible</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><tt>#include</tt> hurts compile time performance. Don't do it unless you
+ have to, especially in header files.</p>
+
+ <p>But wait, sometimes you need to have the definition of a class to use it, or
+ to inherit from it. In these cases go ahead and #include that header file. Be
+ aware however that there are many cases where you don't need to have the full
+ definition of a class. If you are using a pointer or reference to a class, you
+ don't need the header file. If you are simply returning a class instance from a
+ prototyped function or method, you don't need it. In fact, for most cases, you
+ simply don't need the definition of a class... and not <tt>#include</tt>'ing
+ speeds up compilation.</p>
+
+ <p>It is easy to try to go too overboard on this recommendation, however. You
+ <b>must</b> include all of the header files that you are using, either directly
+ or indirectly (through another header file). To make sure that you don't
+ accidently forget to include a header file in your module header, make sure to
+ include your module header <b>first</b> in the implementation file (as mentioned
+ above). This way there won't be any hidden dependencies that you'll find out
+ about later...</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="hl_privateheaders">Keep "internal" Headers Private</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Many modules have a complex implementation that causes them to use more than
+ one implementation (<tt>.cpp</tt>) file. It is often tempting to put the
+ internal communication interface (helper classes, extra functions, etc) in the
+ public module header file. Don't do this. :)</p>
+
+ <p>If you really need to do something like this, put a private header file in
+ the same directory as the source files, and include it locally. This ensures
+ that your private interface remains private and undisturbed by outsiders.</p>
+
+ <p>Note however, that it's okay to put extra implementation methods a public
+ class itself... just make them private (or protected), and all is well.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_text">
+ <a name="micro">The Low Level Issues</a>
+ </div>
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="hl_assert">Assert Liberally</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Use the "<tt>assert</tt>" function to its fullest. Check all of your
+ preconditions and assumptions, you never know when a bug (not neccesarily even
+ yours) might be caught early by an assertion, which reduces debugging time
+ dramatically. The "<tt><cassert></tt>" header file is probably already
+ included by the header files you are using, so it doesn't cost anything to use
+ it.</p>
+
+ <p>To further assist with debugging, make sure to put some kind of error message
+ in the assertion statement (which is printed if the assertion is tripped). This
+ helps the poor debugging make sense of why an assertion is being made and
+ enforced, and hopefully what to do about it. Here is one complete example:</p>
+
+ <pre>
+ inline Value *getOperand(unsigned i) {
+ assert(i < Operands.size() && "getOperand() out of range!");
+ return Operands[i];
+ }
+ </pre>
+
+ <p>Here are some examples:</p>
+
+ <pre>
+ assert(Ty->isPointerType() && "Can't allocate a non pointer type!");
+
+ assert((Opcode == Shl || Opcode == Shr) && "ShiftInst Opcode invalid!");
+
+ assert(idx < getNumSuccessors() && "Successor # out of range!");
+
+ assert(V1.getType() == V2.getType() && "Constant types must be identical!");
+
+ assert(isa<PHINode>(Succ->front()) && "Only works on PHId BBs!");
+ </pre>
+
+ <p>You get the idea...</p>
+
+ </div>
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="hl_preincrement">Prefer Preincrement</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Hard fast rule: Preincrement (++X) may be no slower than postincrement (X++)
+ and could very well be a lot faster than it. Use preincrementation whenever
+ possible.</p>
+
+ <p>The semantics of postincrement include making a copy of the value being
+ incremented, returning it, and then preincrementing the "work value". For
+ primitive types, this isn't a big deal... but for iterators, it can be a huge
+ issue (for example, some iterators contains stack and set objects in them...
+ copying an iterator could invoke the copy ctor's of these as well). In general,
+ get in the habit of always using preincrement, and you won't have a problem.</p>
+
+ </div>
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="hl_avoidendl">Avoid endl</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>endl</tt> modifier, when used with iostreams outputs a newline to the
+ output stream specified. In addition to doing this, however, it also flushes
+ the output stream. In other words, these are equivalent:</p>
+
+ <pre>
+ cout << endl;
+ cout << "\n" << flush;
+ </pre>
+
+ <p>Most of the time, you probably have no reason to flush the output stream, so
+ it's better to use a literal <tt>"\n"</tt>.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="hl_exploitcpp">Exploit C++ to its Fullest</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>C++ is a powerful language. With a firm grasp on its capabilities, you can make
+ write effective, consise, readable and maintainable code all at the same time.
+ By staying consistent, you reduce the amount of special cases that need to be
+ remembered. Reducing the total number of lines of code you write is a good way
+ to avoid documentation, and avoid giving bugs a place to hide.</p>
+
+ <p>For these reasons, come to know and love the contents of your local
+ <algorithm> header file. Know about <functional> and what it can do
+ for you. C++ is just a tool that wants you to master it. :)</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="iterators">Writing Iterators</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Here's a pretty good summary of how to write your own data structure iterators
+ in a way that is compatible with the STL, and with a lot of other code out there
+ (slightly edited by Chris):</p>
+
+ <pre>
+ From: Ross Smith <ross.s at ihug.co.nz>
+ Newsgroups: comp.lang.c++.moderated
+ Subject: Writing iterators (was: Re: Non-template functions that take iterators)
+ Date: 28 Jun 2001 12:07:10 -0400
+
+ Andre Majorel wrote:
+ > Any pointers handy on "writing STL-compatible iterators for
+ > dummies ?"
+
+ I'll give it a try...
+
+ The usual situation requiring user-defined iterators is that you have
+ a type that bears some resemblance to an STL container, and you want
+ to provide iterators so it can be used with STL algorithms. You need
+ to ask three questions:
+
+ First, is this simply a wrapper for an underlying collection of
+ objects that's held somewhere as a real STL container, or is it a
+ "virtual container" for which iteration is (under the hood) more
+ complicated than simply incrementing some underlying iterator (or
+ pointer or index or whatever)? In the former case you can frequently
+ get away with making your container's iterators simply typedefs for
+ those of the underlying container; your begin() function would call
+ member_container.begin(), and so on.
+
+ Second, do you only need read-only iterators, or do you need separate
+ read-only (const) and read-write (non-const) iterators?
+
+ Third, which kind of iterator (input, output, forward, bidirectional,
+ or random access) is appropriate? If you're familiar with the
+ properties of the iterator types (if not, visit
+ <a href="http://www.sgi.com/tech/stl/">http://www.sgi.com/tech/stl/</a>), the appropriate choice should be
+ obvious from the semantics of the container.
+
+ I'll start with forward iterators, as the simplest case that's likely
+ to come up in normal code. Input and output iterators have some odd
+ properties and rarely need to be implemented in user code; I'll leave
+ them out of discussion. Bidirectional and random access iterators are
+ covered below.
+
+ The exact behaviour of a forward iterator is spelled out in the
+ Standard in terms of a set of expressions with specified behaviour,
+ rather than a set of member functions, which leaves some leeway in how
+ you actually implement it. Typically it looks something like this
+ (I'll start with the const-iterator-only situation):
+
+ #include <iterator>
+
+ class container {
+ public:
+ typedef something_or_other value_type;
+ class const_iterator:
+ public std::iterator<std::forward_iterator_tag, value_type> {
+ friend class container;
+ public:
+ const value_type& operator*() const;
+ const value_type* operator->() const;
+ const_iterator& operator++();
+ const_iterator operator++(int);
+ friend bool operator==(const_iterator lhs,
+ const_iterator rhs);
+ friend bool operator!=(const_iterator lhs,
+ const_iterator rhs);
+ private:
+ //...
+ };
+ //...
+ };
+
+ An iterator should always be derived from an instantiation of the
+ std::iterator template. The iterator's life cycle functions
+ (constructors, destructor, and assignment operator) aren't declared
+ here; in most cases the compiler-generated ones are sufficient. The
+ container needs to be a friend of the iterator so that the container's
+ begin() and end() functions can fill in the iterator's private members
+ with the appropriate values.
+
+ <i>[Chris's Note: I prefer to not make my iterators friends. Instead, two
+ ctor's are provided for the iterator class: one to start at the end of the
+ container, and one at the beginning. Typically this is done by providing
+ two constructors with different signatures.]</i>
+
+ There are normally only three member functions that need nontrivial
+ implementations; the rest are just boilerplate.
+
+ const container::value_type&
+ container::const_iterator::operator*() const {
+ // find the element and return a reference to it
+ }
+
+ const container::value_type*
+ container::const_iterator::operator->() const {
+ return &**this;
+ }
+
+ If there's an underlying real container, operator*() can just return a
+ reference to the appropriate element. If there's no actual container
+ and the elements need to be generated on the fly -- what I think of as
+ a "virtual container" -- things get a bit more complicated; you'll
+ probably need to give the iterator a value_type member object, and
+ fill it in when you need to. This might be done as part of the
+ increment operator (below), or if the operation is nontrivial, you
+ might choose the "lazy" approach and only generate the actual value
+ when one of the dereferencing operators is called.
+
+ The operator->() function is just boilerplate around a call to
+ operator*().
+
+ container::const_iterator&
+ container::const_iterator::operator++() {
+ // the incrementing logic goes here
+ return *this;
+ }
+
+ container::const_iterator
+ container::const_iterator::operator++(int) {
+ const_iterator old(*this);
+ ++*this;
+ return old;
+ }
+
+ Again, the incrementing logic will usually be trivial if there's a
+ real container involved, more complicated if you're working with a
+ virtual container. In particular, watch out for what happens when you
+ increment past the last valid item -- this needs to produce an
+ iterator that will compare equal to container.end(), and making this
+ work is often nontrivial for virtual containers.
+
+ The post-increment function is just boilerplate again (and
+ incidentally makes it obvious why all the experts recommend using
+ pre-increment wherever possible).
+
+ bool operator==(container::const_iterator lhs,
+ container::const_iterator rhs) {
+ // equality comparison goes here
+ }
+
+ bool operator!=(container::const_iterator lhs,
+ container::const_iterator rhs) {
+ return !(lhs == rhs);
+ }
+
+ For a real container, the equality comparison will usually just
+ compare the underlying iterators (or pointers or indices or whatever).
+ The semantics of comparisons for virtual container iterators are often
+ tricky. Remember that iterator comparison only needs to be defined for
+ iterators into the same container, so you can often simplify things by
+ taking for granted that lhs and rhs both point into the same container
+ object. Again, the second function is just boilerplate.
+
+ It's a matter of taste whether iterator arguments are passed by value
+ or reference; I've shown tham passed by value to reduce clutter, but
+ if the iterator contains several data members, passing by reference
+ may be better.
+
+ That convers the const-iterator-only situation. When we need separate
+ const and mutable iterators, one small complication is added beyond
+ the simple addition of a second class.
+
+ class container {
+ public:
+ typedef something_or_other value_type;
+ class const_iterator;
+ class iterator:
+ public std::iterator<std::forward_iterator_tag, value_type> {
+ friend class container;
+ friend class container::const_iterator;
+ public:
+ value_type& operator*() const;
+ value_type* operator->() const;
+ iterator& operator++();
+ iterator operator++(int);
+ friend bool operator==(iterator lhs, iterator rhs);
+ friend bool operator!=(iterator lhs, iterator rhs);
+ private:
+ //...
+ };
+ class const_iterator:
+ public std::iterator<std::forward_iterator_tag, value_type> {
+ friend class container;
+ public:
+ const_iterator();
+ const_iterator(const iterator& i);
+ const value_type& operator*() const;
+ const value_type* operator->() const;
+ const_iterator& operator++();
+ const_iterator operator++(int);
+ friend bool operator==(const_iterator lhs,
+ const_iterator rhs);
+ friend bool operator!=(const_iterator lhs,
+ const_iterator rhs);
+ private:
+ //...
+ };
+ //...
+ };
+
+ There needs to be a conversion from iterator to const_iterator (so
+ that mixed-type operations, such as comparison between an iterator and
+ a const_iterator, will work). This is done here by giving
+ const_iterator a conversion constructor from iterator (equivalently,
+ we could have given iterator an operator const_iterator()), which
+ requires const_iterator to be a friend of iterator, so it can copy its
+ data members. (It also requires the addition of an explicit default
+ constructor to const_iterator, since the existence of another
+ user-defined constructor inhibits the compiler-defined one.)
+
+ Bidirectional iterators add just two member functions to forward
+ iterators:
+
+ class iterator:
+ public std::iterator<std::bidirectional_iterator_tag, value_type> {
+ public:
+ //...
+ iterator& operator--();
+ iterator operator--(int);
+ //...
+ };
+
+ I won't detail the implementations, they're obvious variations on
+ operator++().
+
+ Random access iterators add several more member and friend functions:
+
+ class iterator:
+ public std::iterator<std::random_access_iterator_tag, value_type> {
+ public:
+ //...
+ iterator& operator+=(difference_type rhs);
+ iterator& operator-=(difference_type rhs);
+ friend iterator operator+(iterator lhs, difference_type rhs);
+ friend iterator operator+(difference_type lhs, iterator rhs);
+ friend iterator operator-(iterator lhs, difference_type rhs);
+ friend difference_type operator-(iterator lhs, iterator rhs);
+ friend bool operator<(iterator lhs, iterator rhs);
+ friend bool operator>(iterator lhs, iterator rhs);
+ friend bool operator<=(iterator lhs, iterator rhs);
+ friend bool operator>=(iterator lhs, iterator rhs);
+ //...
+ };
+
+ container::iterator&
+ container::iterator::operator+=(container::difference_type rhs) {
+ // add rhs to iterator position
+ return *this;
+ }
+
+ container::iterator&
+ container::iterator::operator-=(container::difference_type rhs) {
+ // subtract rhs from iterator position
+ return *this;
+ }
+
+ container::iterator operator+(container::iterator lhs,
+ container::difference_type rhs) {
+ return iterator(lhs) += rhs;
+ }
+
+ container::iterator operator+(container::difference_type lhs,
+ container::iterator rhs) {
+ return iterator(rhs) += lhs;
+ }
+
+ container::iterator operator-(container::iterator lhs,
+ container::difference_type rhs) {
+ return iterator(lhs) -= rhs;
+ }
+
+ container::difference_type operator-(container::iterator lhs,
+ container::iterator rhs) {
+ // calculate distance between iterators
+ }
+
+ bool operator<(container::iterator lhs, container::iterator rhs) {
+ // perform less-than comparison
+ }
+
+ bool operator>(container::iterator lhs, container::iterator rhs) {
+ return rhs < lhs;
+ }
+
+ bool operator<=(container::iterator lhs, container::iterator rhs) {
+ return !(rhs < lhs);
+ }
+
+ bool operator>=(container::iterator lhs, container::iterator rhs) {
+ return !(lhs < rhs);
+ }
+
+ Four of the functions (operator+=(), operator-=(), the second
+ operator-(), and operator<()) are nontrivial; the rest are
+ boilerplate.
+
+ One feature of the above code that some experts may disapprove of is
+ the declaration of all the free functions as friends, when in fact
+ only a few of them need direct access to the iterator's private data.
+ I originally got into the habit of doing this simply to keep the
+ declarations together; declaring some functions inside the class and
+ some outside seemed awkward. Since then, though, I've been told that
+ there's a subtle difference in the way name lookup works for functions
+ declared inside a class (as friends) and outside, so keeping them
+ together in the class is probably a good idea for practical as well as
+ aesthetic reasons.
+
+ I hope all this is some help to anyone who needs to write their own
+ STL-like containers and iterators.
+
+ --
+ Ross Smith <ross.s at ihug.co.nz> The Internet Group, Auckland, New Zealand
+ </pre>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="seealso">See Also</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>A lot of these comments and recommendations have been culled for other
+ sources. Two particularly important books for our work are:</p>
+
+ <ol>
+
+ <li><a href="http://www.aw.com/product/0,2627,0201924889,00.html">Effective
+ C++</a> by Scott Meyers. There is an online version of the book (only some
+ chapters though) <a
+ href="http://www.awlonline.com/cseng/meyerscddemo/">available as well</a>.</li>
+
+ <li><a href="http://cseng.aw.com/book/0,3828,0201633620,00.html">Large-Scale C++
+ Software Design</a> by John Lakos</li>
+
+ </ol>
+
+ <p>If you get some free time, and you haven't read them: do so, you might learn
+ something. :)</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+
+ <hr>
+
+ <div class="doc_footer">
+ <address><a href="mailto:sabre at nondot.org">Chris Lattner</a></address>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </div>
+
+ </body>
+ </html>
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>CommandLine 2.0 Library Manual</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">
+ CommandLine 2.0 Library Manual
+ </div>
+
+ <ol>
+ <li><a href="#introduction">Introduction</a></li>
+
+ <li><a href="#quickstart">Quick Start Guide</a>
+ <ol>
+ <li><a href="#bool">Boolean Arguments</a></li>
+ <li><a href="#alias">Argument Aliases</a></li>
+ <li><a href="#onealternative">Selecting an alternative from a
+ set of possibilities</a></li>
+ <li><a href="#namedalternatives">Named alternatives</a></li>
+ <li><a href="#list">Parsing a list of options</a></li>
+ <li><a href="#description">Adding freeform text to help output</a></li>
+ </ol></li>
+
+ <li><a href="#referenceguide">Reference Guide</a>
+ <ol>
+ <li><a href="#positional">Positional Arguments</a>
+ <ul>
+ <li><a href="#--">Specifying positional options with hyphens</a></li>
+ <li><a href="#cl::ConsumeAfter">The <tt>cl::ConsumeAfter</tt>
+ modifier</a></li>
+ </ul></li>
+
+ <li><a href="#storage">Internal vs External Storage</a></li>
+
+ <li><a href="#attributes">Option Attributes</a></li>
+
+ <li><a href="#modifiers">Option Modifiers</a>
+ <ul>
+ <li><a href="#hiding">Hiding an option from <tt>--help</tt>
+ output</a></li>
+ <li><a href="#numoccurrences">Controlling the number of occurrences
+ required and allowed</a></li>
+ <li><a href="#valrequired">Controlling whether or not a value must be
+ specified</a></li>
+ <li><a href="#formatting">Controlling other formatting options</a></li>
+ <li><a href="#misc">Miscellaneous option modifiers</a></li>
+ </ul></li>
+
+ <li><a href="#toplevel">Top-Level Classes and Functions</a>
+ <ul>
+ <li><a href="#cl::ParseCommandLineOptions">The
+ <tt>cl::ParseCommandLineOptions</tt> function</a></li>
+ <li><a href="#cl::ParseEnvironmentOptions">The
+ <tt>cl::ParseEnvironmentOptions</tt> function</a></li>
+ <li><a href="#cl::opt">The <tt>cl::opt</tt> class</a></li>
+ <li><a href="#cl::list">The <tt>cl::list</tt> class</a></li>
+ <li><a href="#cl::alias">The <tt>cl::alias</tt> class</a></li>
+ </ul></li>
+
+ <li><a href="#builtinparsers">Builtin parsers</a>
+ <ul>
+ <li><a href="#genericparser">The Generic <tt>parser<t></tt>
+ parser</a></li>
+ <li><a href="#boolparser">The <tt>parser<bool></tt>
+ specialization</a></li>
+ <li><a href="#stringparser">The <tt>parser<string></tt>
+ specialization</a></li>
+ <li><a href="#intparser">The <tt>parser<int></tt>
+ specialization</a></li>
+ <li><a href="#doubleparser">The <tt>parser<double></tt> and
+ <tt>parser<float></tt> specializations</a></li>
+ </ul></li>
+ </ol></li>
+ <li><a href="#extensionguide">Extension Guide</a>
+ <ol>
+ <li><a href="#customparser">Writing a custom parser</a></li>
+ <li><a href="#explotingexternal">Exploiting external storage</a></li>
+ <li><a href="#dynamicopts">Dynamically adding command line
+ options</a></li>
+ </ol></li>
+ </ol>
+
+ <div class="doc_text">
+ <p><b>Written by <a href="mailto:sabre at nondot.org">Chris Lattner</a></b></p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="introduction">Introduction</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This document describes the CommandLine argument processing library. It will
+ show you how to use it, and what it can do. The CommandLine library uses a
+ declarative approach to specifying the command line options that your program
+ takes. By default, these options declarations implicitly hold the value parsed
+ for the option declared (of course this <a href="#storage">can be
+ changed</a>).</p>
+
+ <p>Although there are a <b>lot</b> of command line argument parsing libraries
+ out there in many different languages, none of them fit well with what I needed.
+ By looking at the features and problems of other libraries, I designed the
+ CommandLine library to have the following features:</p>
+
+ <ol>
+ <li>Speed: The CommandLine library is very quick and uses little resources. The
+ parsing time of the library is directly proportional to the number of arguments
+ parsed, not the the number of options recognized. Additionally, command line
+ argument values are captured transparently into user defined global variables,
+ which can be accessed like any other variable (and with the same
+ performance).</li>
+
+ <li>Type Safe: As a user of CommandLine, you don't have to worry about
+ remembering the type of arguments that you want (is it an int? a string? a
+ bool? an enum?) and keep casting it around. Not only does this help prevent
+ error prone constructs, it also leads to dramatically cleaner source code.</li>
+
+ <li>No subclasses required: To use CommandLine, you instantiate variables that
+ correspond to the arguments that you would like to capture, you don't subclass a
+ parser. This means that you don't have to write <b>any</b> boilerplate
+ code.</li>
+
+ <li>Globally accessible: Libraries can specify command line arguments that are
+ automatically enabled in any tool that links to the library. This is possible
+ because the application doesn't have to keep a "list" of arguments to pass to
+ the parser. This also makes supporting <a href="#dynamicopts">dynamically
+ loaded options</a> trivial.</li>
+
+ <li>Cleaner: CommandLine supports enum and other types directly, meaning that
+ there is less error and more security built into the library. You don't have to
+ worry about whether your integral command line argument accidentally got
+ assigned a value that is not valid for your enum type.</li>
+
+ <li>Powerful: The CommandLine library supports many different types of
+ arguments, from simple <a href="#boolparser">boolean flags</a> to <a
+ href="#cl::opt">scalars arguments</a> (<a href="#stringparser">strings</a>, <a
+ href="#intparser">integers</a>, <a href="#genericparser">enums</a>, <a
+ href="#doubleparser">doubles</a>), to <a href="#cl::list">lists of
+ arguments</a>. This is possible because CommandLine is...</li>
+
+ <li>Extensible: It is very simple to add a new argument type to CommandLine.
+ Simply specify the parser that you want to use with the command line option when
+ you declare it. <a href="#customparser">Custom parsers</a> are no problem.</li>
+
+ <li>Labor Saving: The CommandLine library cuts down on the amount of grunt work
+ that you, the user, have to do. For example, it automatically provides a
+ <tt>--help</tt> option that shows the available command line options for your
+ tool. Additionally, it does most of the basic correctness checking for
+ you.</li>
+
+ <li>Capable: The CommandLine library can handle lots of different forms of
+ options often found in real programs. For example, <a
+ href="#positional">positional</a> arguments, <tt>ls</tt> style <a
+ href="#cl::Grouping">grouping</a> options (to allow processing '<tt>ls
+ -lad</tt>' naturally), <tt>ld</tt> style <a href="#cl::Prefix">prefix</a>
+ options (to parse '<tt>-lmalloc -L/usr/lib</tt>'), and <a
+ href="#cl::ConsumeAfter">interpreter style options</a>.</li>
+
+ </ol>
+
+ <p>This document will hopefully let you jump in and start using CommandLine in
+ your utility quickly and painlessly. Additionally it should be a simple
+ reference manual to figure out how stuff works. If it is failing in some area
+ (or you want an extension to the library), nag the author, <a
+ href="mailto:sabre at nondot.org">Chris Lattner</a>.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="quickstart">Quick Start Guide</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This section of the manual runs through a simple CommandLine'ification of a
+ basic compiler tool. This is intended to show you how to jump into using the
+ CommandLine library in your own program, and show you some of the cool things it
+ can do.</p>
+
+ <p>To start out, you need to include the CommandLine header file into your
+ program:</p>
+
+ <pre>
+ #include "Support/CommandLine.h"
+ </pre>
+
+ <p>Additionally, you need to add this as the first line of your main
+ program:</p>
+
+ <pre>
+ int main(int argc, char **argv) {
+ <a href="#cl::ParseCommandLineOptions">cl::ParseCommandLineOptions</a>(argc, argv);
+ ...
+ }
+ </pre>
+
+ <p>... which actually parses the arguments and fills in the variable
+ declarations.</p>
+
+ <p>Now that you are ready to support command line arguments, we need to tell the
+ system which ones we want, and what type of argument they are. The CommandLine
+ library uses a declarative syntax to model command line arguments with the
+ global variable declarations that capture the parsed values. This means that
+ for every command line option that you would like to support, there should be a
+ global variable declaration to capture the result. For example, in a compiler,
+ we would like to support the unix standard '<tt>-o <filename></tt>' option
+ to specify where to put the output. With the CommandLine library, this is
+ represented like this:</p>
+
+ <p><tt>
+ <a name="value_desc_example">
+ <a href="#cl::opt">cl::opt</a><string> OutputFilename("<i>o</i>", <a href="#cl::desc">cl::desc</a>("<i>Specify output filename</i>"), <a href="#cl::value_desc">cl::value_desc</a>("<i>filename</i>"));</a>
+ </tt></p>
+
+ <p>This declares a global variable "<tt>OutputFilename</tt>" that is used to
+ capture the result of the "<tt>o</tt>" argument (first parameter). We specify
+ that this is a simple scalar option by using the "<tt><a
+ href="#cl::opt">cl::opt</a></tt>" template (as opposed to the <a
+ href="#list">"<tt>cl::list</tt> template</a>), and tell the CommandLine library
+ that the data type that we are parsing is a string.</p>
+
+ <p>The second and third parameters (which are optional) are used to specify what
+ to output for the "<tt>--help</tt>" option. In this case, we get a line that
+ looks like this:</p>
+
+ <pre>
+ USAGE: compiler [options]
+
+ OPTIONS:
+ -help - display available options (--help-hidden for more)
+ <b>-o <filename> - Specify output filename</b>
+ </pre>
+
+ <p>Because we specified that the command line option should parse using the
+ <tt>string</tt> data type, the variable declared is automatically usable as a
+ real string in all contexts that a normal C++ string object may be used. For
+ example:</p>
+
+ <pre>
+ ...
+ ofstream Output(OutputFilename.c_str());
+ if (Out.good()) ...
+ ...
+ </pre>
+
+ <p>There are many different options that you can use to customize the command
+ line option handling library, but the above example shows the general interface
+ to these options. The options can be specified in any order, and are specified
+ with helper functions like <a href="#cl::desc"><tt>cl::desc(...)</tt></a>, so
+ there are no positional dependencies to remember. The available options are
+ discussed in detail in the <a href="#referenceguide">Reference Guide</a>.</p>
+
+ <p>Continuing the example, we would like to have our compiler take an input
+ filename as well as an output filename, but we do not want the input filename to
+ be specified with a hyphen (ie, not <tt>-filename.c</tt>). To support this
+ style of argument, the CommandLine library allows for <a
+ href="#positional">positional</a> arguments to be specified for the program.
+ These positional arguments are filled with command line parameters that are not
+ in option form. We use this feature like this:</p>
+
+ <pre>
+ <a href="#cl::opt">cl::opt</a><string> InputFilename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"), <a href="#cl::init">cl::init</a>("<i>-</i>"));
+ </pre>
+
+ <p>This declaration indicates that the first positional argument should be
+ treated as the input filename. Here we use the <tt><a
+ href="#cl::init">cl::init</a></tt> option to specify an initial value for the
+ command line option, which is used if the option is not specified (if you do not
+ specify a <tt><a href="#cl::init">cl::init</a></tt> modifier for an option, then
+ the default constructor for the data type is used to initialize the value).
+ Command line options default to being optional, so if we would like to require
+ that the user always specify an input filename, we would add the <tt><a
+ href="#cl::Required">cl::Required</a></tt> flag, and we could eliminate the
+ <tt><a href="#cl::init">cl::init</a></tt> modifier, like this:</p>
+
+ <pre>
+ <a href="#cl::opt">cl::opt</a><string> InputFilename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"), <b><a href="#cl::Required">cl::Required</a></b>);
+ </pre>
+
+ <p>Again, the CommandLine library does not require the options to be specified
+ in any particular order, so the above declaration is equivalent to:</p>
+
+ <pre>
+ <a href="#cl::opt">cl::opt</a><string> InputFilename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::Required">cl::Required</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"));
+ </pre>
+
+ <p>By simply adding the <tt><a href="#cl::Required">cl::Required</a></tt> flag,
+ the CommandLine library will automatically issue an error if the argument is not
+ specified, which shifts all of the command line option verification code out of
+ your application into the library. This is just one example of how using flags
+ can alter the default behaviour of the library, on a per-option basis. By
+ adding one of the declarations above, the <tt>--help</tt> option synopsis is now
+ extended to:</p>
+
+ <pre>
+ USAGE: compiler [options] <b><input file></b>
+
+ OPTIONS:
+ -help - display available options (--help-hidden for more)
+ -o <filename> - Specify output filename
+ </pre>
+
+ <p>... indicating that an input filename is expected.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="bool">Boolean Arguments</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>In addition to input and output filenames, we would like the compiler example
+ to support three boolean flags: "<tt>-f</tt>" to force overwriting of the output
+ file, "<tt>--quiet</tt>" to enable quiet mode, and "<tt>-q</tt>" for backwards
+ compatibility with some of our users. We can support these by declaring options
+ of boolean type like this:</p>
+
+ <pre>
+ <a href="#cl::opt">cl::opt</a><bool> Force ("<i>f</i>", <a href="#cl::desc">cl::desc</a>("<i>Overwrite output files</i>"));
+ <a href="#cl::opt">cl::opt</a><bool> Quiet ("<i>quiet</i>", <a href="#cl::desc">cl::desc</a>("<i>Don't print informational messages</i>"));
+ <a href="#cl::opt">cl::opt</a><bool> Quiet2("<i>q</i>", <a href="#cl::desc">cl::desc</a>("<i>Don't print informational messages</i>"), <a href="#cl::Hidden">cl::Hidden</a>);
+ </pre>
+
+ <p>This does what you would expect: it declares three boolean variables
+ ("<tt>Force</tt>", "<tt>Quiet</tt>", and "<tt>Quiet2</tt>") to recognize these
+ options. Note that the "<tt>-q</tt>" option is specified with the "<a
+ href="#cl::Hidden"><tt>cl::Hidden</tt></a>" flag. This modifier prevents it
+ from being shown by the standard "<tt>--help</tt>" output (note that it is still
+ shown in the "<tt>--help-hidden</tt>" output).</p>
+
+ <p>The CommandLine library uses a <a href="#builtinparsers">different parser</a>
+ for different data types. For example, in the string case, the argument passed
+ to the option is copied literally into the content of the string variable... we
+ obviously cannot do that in the boolean case, however, so we must use a smarter
+ parser. In the case of the boolean parser, it allows no options (in which case
+ it assigns the value of true to the variable), or it allows the values
+ "<tt>true</tt>" or "<tt>false</tt>" to be specified, allowing any of the
+ following inputs:</p>
+
+ <pre>
+ compiler -f # No value, 'Force' == true
+ compiler -f=true # Value specified, 'Force' == true
+ compiler -f=TRUE # Value specified, 'Force' == true
+ compiler -f=FALSE # Value specified, 'Force' == false
+ </pre>
+
+ <p>... you get the idea. The <a href="#boolparser">bool parser</a> just turns
+ the string values into boolean values, and rejects things like '<tt>compiler
+ -f=foo</tt>'. Similarly, the <a href="#doubleparser">float</a>, <a
+ href="#doubleparser">double</a>, and <a href="#intparser">int</a> parsers work
+ like you would expect, using the '<tt>strtol</tt>' and '<tt>strtod</tt>' C
+ library calls to parse the string value into the specified data type.</p>
+
+ <p>With the declarations above, "<tt>compiler --help</tt>" emits this:</p>
+
+ <pre>
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ <b>-f - Overwrite output files</b>
+ -o - Override output filename
+ <b>-quiet - Don't print informational messages</b>
+ -help - display available options (--help-hidden for more)
+ </pre>
+
+ <p>and "<tt>opt --help-hidden</tt>" prints this:</p>
+
+ <pre>
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ -f - Overwrite output files
+ -o - Override output filename
+ <b>-q - Don't print informational messages</b>
+ -quiet - Don't print informational messages
+ -help - display available options (--help-hidden for more)
+ </pre>
+
+ <p>This brief example has shown you how to use the '<tt><a
+ href="#cl::opt">cl::opt</a></tt>' class to parse simple scalar command line
+ arguments. In addition to simple scalar arguments, the CommandLine library also
+ provides primitives to support CommandLine option <a href="#alias">aliases</a>,
+ and <a href="#list">lists</a> of options.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="alias">Argument Aliases</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>So far, the example works well, except for the fact that we need to check the
+ quiet condition like this now:</p>
+
+ <pre>
+ ...
+ if (!Quiet && !Quiet2) printInformationalMessage(...);
+ ...
+ </pre>
+
+ <p>... which is a real pain! Instead of defining two values for the same
+ condition, we can use the "<tt><a href="#cl::alias">cl::alias</a></tt>" class to make the "<tt>-q</tt>"
+ option an <b>alias</b> for the "<tt>-quiet</tt>" option, instead of providing
+ a value itself:</p>
+
+ <pre>
+ <a href="#cl::opt">cl::opt</a><bool> Force ("<i>f</i>", <a href="#cl::desc">cl::desc</a>("<i>Overwrite output files</i>"));
+ <a href="#cl::opt">cl::opt</a><bool> Quiet ("<i>quiet</i>", <a href="#cl::desc">cl::desc</a>("<i>Don't print informational messages</i>"));
+ <a href="#cl::alias">cl::alias</a> QuietA("<i>q</i>", <a href="#cl::desc">cl::desc</a>("<i>Alias for -quiet</i>"), <a href="#cl::aliasopt">cl::aliasopt</a>(Quiet));
+ </pre>
+
+ <p>The third line (which is the only one we modified from above) defines a
+ "<tt>-q</tt> alias that updates the "<tt>Quiet</tt>" variable (as specified by
+ the <tt><a href="#cl::aliasopt">cl::aliasopt</a></tt> modifier) whenever it is
+ specified. Because aliases do not hold state, the only thing the program has to
+ query is the <tt>Quiet</tt> variable now. Another nice feature of aliases is
+ that they automatically hide themselves from the <tt>-help</tt> output
+ (although, again, they are still visible in the <tt>--help-hidden
+ output</tt>).</p>
+
+ <p>Now the application code can simply use:</p>
+
+ <pre>
+ ...
+ if (!Quiet) printInformationalMessage(...);
+ ...
+ </pre>
+
+ <p>... which is much nicer! The "<tt><a href="#cl::alias">cl::alias</a></tt>"
+ can be used to specify an alternative name for any variable type, and has many
+ uses.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="onealternative">Selecting an alternative from a set of
+ possibilities</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>So far, we have seen how the CommandLine library handles builtin types like
+ <tt>std::string</tt>, <tt>bool</tt> and <tt>int</tt>, but how does it handle
+ things it doesn't know about, like enums or '<tt>int*</tt>'s?</p>
+
+ <p>The answer is that it uses a table driven generic parser (unless you specify
+ your own parser, as described in the <a href="#extensionguide">Extension
+ Guide</a>). This parser maps literal strings to whatever type is required, are
+ requires you to tell it what this mapping should be.</p>
+
+ <p>Lets say that we would like to add four optimizations levels to our
+ optimizer, using the standard flags "<tt>-g</tt>", "<tt>-O0</tt>",
+ "<tt>-O1</tt>", and "<tt>-O2</tt>". We could easily implement this with boolean
+ options like above, but there are several problems with this strategy:</p>
+
+ <ol>
+ <li>A user could specify more than one of the options at a time, for example,
+ "<tt>opt -O3 -O2</tt>". The CommandLine library would not be able to catch this
+ erroneous input for us.</li>
+
+ <li>We would have to test 4 different variables to see which ones are set.</li>
+
+ <li>This doesn't map to the numeric levels that we want... so we cannot easily
+ see if some level >= "<tt>-O1</tt>" is enabled.</li>
+
+ </ol>
+
+ <p>To cope with these problems, we can use an enum value, and have the
+ CommandLine library fill it in with the appropriate level directly, which is
+ used like this:</p>
+
+ <pre>
+ enum OptLevel {
+ g, O1, O2, O3
+ };
+
+ <a href="#cl::opt">cl::opt</a><OptLevel> OptimizationLevel(<a href="#cl::desc">cl::desc</a>("<i>Choose optimization level:</i>"),
+ <a href="#cl::values">cl::values</a>(
+ clEnumVal(g , "<i>No optimizations, enable debugging</i>"),
+ clEnumVal(O1, "<i>Enable trivial optimizations</i>"),
+ clEnumVal(O2, "<i>Enable default optimizations</i>"),
+ clEnumVal(O3, "<i>Enable expensive optimizations</i>"),
+ 0));
+
+ ...
+ if (OptimizationLevel >= O2) doPartialRedundancyElimination(...);
+ ...
+ </pre>
+
+ <p>This declaration defines a variable "<tt>OptimizationLevel</tt>" of the
+ "<tt>OptLevel</tt>" enum type. This variable can be assigned any of the values
+ that are listed in the declaration (Note that the declaration list must be
+ terminated with the "<tt>0</tt>" argument!). The CommandLine library enforces
+ that the user can only specify one of the options, and it ensure that only valid
+ enum values can be specified. The "<tt>clEnumVal</tt>" macros ensure that the
+ command line arguments matched the enum values. With this option added, our
+ help output now is:</p>
+
+ <pre>
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ <b>Choose optimization level:
+ -g - No optimizations, enable debugging
+ -O1 - Enable trivial optimizations
+ -O2 - Enable default optimizations
+ -O3 - Enable expensive optimizations</b>
+ -f - Overwrite output files
+ -help - display available options (--help-hidden for more)
+ -o <filename> - Specify output filename
+ -quiet - Don't print informational messages
+ </pre>
+
+ <p>In this case, it is sort of awkward that flag names correspond directly to
+ enum names, because we probably don't want a enum definition named "<tt>g</tt>"
+ in our program. Because of this, we can alternatively write this example like
+ this:</p>
+
+ <pre>
+ enum OptLevel {
+ Debug, O1, O2, O3
+ };
+
+ <a href="#cl::opt">cl::opt</a><OptLevel> OptimizationLevel(<a href="#cl::desc">cl::desc</a>("<i>Choose optimization level:</i>"),
+ <a href="#cl::values">cl::values</a>(
+ clEnumValN(Debug, "g", "<i>No optimizations, enable debugging</i>"),
+ clEnumVal(O1 , "<i>Enable trivial optimizations</i>"),
+ clEnumVal(O2 , "<i>Enable default optimizations</i>"),
+ clEnumVal(O3 , "<i>Enable expensive optimizations</i>"),
+ 0));
+
+ ...
+ if (OptimizationLevel == Debug) outputDebugInfo(...);
+ ...
+ </pre>
+
+ <p>By using the "<tt>clEnumValN</tt>" macro instead of "<tt>clEnumVal</tt>", we
+ can directly specify the name that the flag should get. In general a direct
+ mapping is nice, but sometimes you can't or don't want to preserve the mapping,
+ which is when you would use it.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="namedalternatives">Named Alternatives</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Another useful argument form is a named alternative style. We shall use this
+ style in our compiler to specify different debug levels that can be used.
+ Instead of each debug level being its own switch, we want to support the
+ following options, of which only one can be specified at a time:
+ "<tt>--debug-level=none</tt>", "<tt>--debug-level=quick</tt>",
+ "<tt>--debug-level=detailed</tt>". To do this, we use the exact same format as
+ our optimization level flags, but we also specify an option name. For this
+ case, the code looks like this:</p>
+
+ <pre>
+ enum DebugLev {
+ nodebuginfo, quick, detailed
+ };
+
+ // Enable Debug Options to be specified on the command line
+ <a href="#cl::opt">cl::opt</a><DebugLev> DebugLevel("<i>debug_level</i>", <a href="#cl::desc">cl::desc</a>("<i>Set the debugging level:</i>"),
+ <a href="#cl::values">cl::values</a>(
+ clEnumValN(nodebuginfo, "none", "<i>disable debug information</i>"),
+ clEnumVal(quick, "<i>enable quick debug information</i>"),
+ clEnumVal(detailed, "<i>enable detailed debug information</i>"),
+ 0));
+ </pre>
+
+ <p>This definition defines an enumerated command line variable of type "<tt>enum
+ DebugLev</tt>", which works exactly the same way as before. The difference here
+ is just the interface exposed to the user of your program and the help output by
+ the "<tt>--help</tt>" option:</p>
+
+ <pre>
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ Choose optimization level:
+ -g - No optimizations, enable debugging
+ -O1 - Enable trivial optimizations
+ -O2 - Enable default optimizations
+ -O3 - Enable expensive optimizations
+ <b>-debug_level - Set the debugging level:
+ =none - disable debug information
+ =quick - enable quick debug information
+ =detailed - enable detailed debug information</b>
+ -f - Overwrite output files
+ -help - display available options (--help-hidden for more)
+ -o <filename> - Specify output filename
+ -quiet - Don't print informational messages
+ </pre>
+
+ <p>Again, the only structural difference between the debug level declaration and
+ the optimiation level declaration is that the debug level declaration includes
+ an option name (<tt>"debug_level"</tt>), which automatically changes how the
+ library processes the argument. The CommandLine library supports both forms so
+ that you can choose the form most appropriate for your application.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="list">Parsing a list of options</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Now that we have the standard run of the mill argument types out of the way,
+ lets get a little wild and crazy. Lets say that we want our optimizer to accept
+ a <b>list</b> of optimizations to perform, allowing duplicates. For example, we
+ might want to run: "<tt>compiler -dce -constprop -inline -dce -strip</tt>". In
+ this case, the order of the arguments and the number of appearances is very
+ important. This is what the "<tt><a href="#cl::list">cl::list</a></tt>"
+ template is for. First, start by defining an enum of the optimizations that you
+ would like to perform:</p>
+
+ <pre>
+ enum Opts {
+ // 'inline' is a C++ keyword, so name it 'inlining'
+ dce, constprop, inlining, strip
+ };
+ </pre>
+
+ <p>Then define your "<tt><a href="#cl::list">cl::list</a></tt>" variable:</p>
+
+ <pre>
+ <a href="#cl::list">cl::list</a><Opts> OptimizationList(<a href="#cl::desc">cl::desc</a>("<i>Available Optimizations:</i>"),
+ <a href="#cl::values">cl::values</a>(
+ clEnumVal(dce , "<i>Dead Code Elimination</i>"),
+ clEnumVal(constprop , "<i>Constant Propagation</i>"),
+ clEnumValN(inlining, "<i>inline</i>", "<i>Procedure Integration</i>"),
+ clEnumVal(strip , "<i>Strip Symbols</i>"),
+ 0));
+ </pre>
+
+ <p>This defines a variable that is conceptually of the type
+ "<tt>std::vector<enum Opts></tt>". Thus, you can access it with standard
+ vector methods:</p>
+
+ <pre>
+ for (unsigned i = 0; i != OptimizationList.size(); ++i)
+ switch (OptimizationList[i])
+ ...
+ </pre>
+
+ <p>... to iterate through the list of options specified.</p>
+
+ <p>Note that the "<tt><a href="#cl::list">cl::list</a></tt>" template is
+ completely general and may be used with any data types or other arguments that
+ you can use with the "<tt><a href="#cl::opt">cl::opt</a></tt>" template. One
+ especially useful way to use a list is to capture all of the positional
+ arguments together if there may be more than one specified. In the case of a
+ linker, for example, the linker takes several '<tt>.o</tt>' files, and needs to
+ capture them into a list. This is naturally specified as:</p>
+
+ <pre>
+ ...
+ <a href="#cl::list">cl::list</a><std::string> InputFilenames(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<Input files>"), <a href="#cl::OneOrMore">cl::OneOrMore</a>);
+ ...
+ </pre>
+
+ <p>This variable works just like a "<tt>vector<string></tt>" object. As
+ such, accessing the list is simple, just like above. In this example, we used
+ the <tt><a href="#cl::OneOrMore">cl::OneOrMore</a></tt> modifier to inform the
+ CommandLine library that it is an error if the user does not specify any
+ <tt>.o</tt> files on our command line. Again, this just reduces the amount of
+ checking we have to do.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="description">Adding freeform text to help output</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>As our program grows and becomes more mature, we may decide to put summary
+ information about what it does into the help output. The help output is styled
+ to look similar to a Unix <tt>man</tt> page, providing concise information about
+ a program. Unix <tt>man</tt> pages, however often have a description about what
+ the program does. To add this to your CommandLine program, simply pass a third
+ argument to the <a
+ href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>
+ call in main. This additional argument is then printed as the overview
+ information for your program, allowing you to include any additional information
+ that you want. For example:</p>
+
+ <pre>
+ int main(int argc, char **argv) {
+ <a href="#cl::ParseCommandLineOptions">cl::ParseCommandLineOptions</a>(argc, argv, " CommandLine compiler example\n\n"
+ " This program blah blah blah...\n");
+ ...
+ }
+ </pre>
+
+ <p>Would yield the help output:</p>
+
+ <pre>
+ <b>OVERVIEW: CommandLine compiler example
+
+ This program blah blah blah...</b>
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ ...
+ -help - display available options (--help-hidden for more)
+ -o <filename> - Specify output filename
+ </pre>
+
+ </div>
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="referenceguide">Reference Guide</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Now that you know the basics of how to use the CommandLine library, this
+ section will give you the detailed information you need to tune how command line
+ options work, as well as information on more "advanced" command line option
+ processing capabilities.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="positional">Positional Arguments</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Positional arguments are those arguments that are not named, and are not
+ specified with a hyphen. Positional arguments should be used when an option is
+ specified by its position alone. For example, the standard Unix <tt>grep</tt>
+ tool takes a regular expression argument, and an optional filename to search
+ through (which defaults to standard input if a filename is not specified).
+ Using the CommandLine library, this would be specified as:</p>
+
+ <pre>
+ <a href="#cl::opt">cl::opt</a><string> Regex (<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><regular expression></i>"), <a href="#cl::Required">cl::Required</a>);
+ <a href="#cl::opt">cl::opt</a><string> Filename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"), <a href="#cl::init">cl::init</a>("<i>-</i>"));
+ </pre>
+
+ <p>Given these two option declarations, the <tt>--help</tt> output for our grep
+ replacement would look like this:</p>
+
+ <pre>
+ USAGE: spiffygrep [options] <b><regular expression> <input file></b>
+
+ OPTIONS:
+ -help - display available options (--help-hidden for more)
+ </pre>
+
+ <p>... and the resultant program could be used just like the standard
+ <tt>grep</tt> tool.</p>
+
+ <p>Positional arguments are sorted by their order of construction. This means
+ that command line options will be ordered according to how they are listed in a
+ .cpp file, but will not have an ordering defined if they positional arguments
+ are defined in multiple .cpp files. The fix for this problem is simply to
+ define all of your positional arguments in one .cpp file.</p>
+
+ </div>
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="--">Specifying positional options with hyphens</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Sometimes you may want to specify a value to your positional argument that
+ starts with a hyphen (for example, searching for '<tt>-foo</tt>' in a file). At
+ first, you will have trouble doing this, because it will try to find an argument
+ named '<tt>-foo</tt>', and will fail (and single quotes will not save you).
+ Note that the system <tt>grep</tt> has the same problem:</p>
+
+ <pre>
+ $ spiffygrep '-foo' test.txt
+ Unknown command line argument '-foo'. Try: spiffygrep --help'
+
+ $ grep '-foo' test.txt
+ grep: illegal option -- f
+ grep: illegal option -- o
+ grep: illegal option -- o
+ Usage: grep -hblcnsviw pattern file . . .
+ </pre>
+
+ <p>The solution for this problem is the same for both your tool and the system
+ version: use the '<tt>--</tt>' marker. When the user specifies '<tt>--</tt>' on
+ the command line, it is telling the program that all options after the
+ '<tt>--</tt>' should be treated as positional arguments, not options. Thus, we
+ can use it like this:</p>
+
+ <pre>
+ $ spiffygrep -- -foo test.txt
+ ...output...
+ </pre>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="cl::ConsumeAfter">The <tt>cl::ConsumeAfter</tt> modifier</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>cl::ConsumeAfter</tt> <a href="#formatting">formatting option</a> is
+ used to construct programs that use "interpreter style" option processing. With
+ this style of option processing, all arguments specified after the last
+ positional argument are treated as special interpreter arguments that are not
+ interpreted by the command line argument.</p>
+
+ <p>As a concrete example, lets say we are developing a replacement for the
+ standard Unix Bourne shell (<tt>/bin/sh</tt>). To run <tt>/bin/sh</tt>, first
+ you specify options to the shell itself (like <tt>-x</tt> which turns on trace
+ output), then you specify the name of the script to run, then you specify
+ arguments to the script. These arguments to the script are parsed by the bourne
+ shell command line option processor, but are not interpreted as options to the
+ shell itself. Using the CommandLine library, we would specify this as:</p>
+
+ <pre>
+ <a href="#cl::opt">cl::opt</a><string> Script(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input script></i>"), <a href="#cl::init">cl::init</a>("-"));
+ <a href="#cl::list">cl::list</a><string> Argv(<a href="#cl::ConsumeAfter">cl::ConsumeAfter</a>, <a href="#cl::desc">cl::desc</a>("<i><program arguments>...</i>"));
+ <a href="#cl::opt">cl::opt</a><bool> Trace("<i>x</i>", <a href="#cl::desc">cl::desc</a>("<i>Enable trace output</i>"));
+ </pre>
+
+ <p>which automatically provides the help output:</p>
+
+ <pre>
+ USAGE: spiffysh [options] <b><input script> <program arguments>...</b>
+
+ OPTIONS:
+ -help - display available options (--help-hidden for more)
+ <b>-x - Enable trace output</b>
+ </pre>
+
+ <p>At runtime, if we run our new shell replacement as '<tt>spiffysh -x test.sh
+ -a -x -y bar</tt>', the <tt>Trace</tt> variable will be set to true, the
+ <tt>Script</tt> variable will be set to "<tt>test.sh</tt>", and the
+ <tt>Argv</tt> list will contain <tt>["-a", "-x", "-y", "bar"]</tt>, because they
+ were specified after the last positional argument (which is the script
+ name).</p>
+
+ <p>There are several limitations to when <tt>cl::ConsumeAfter</tt> options can
+ be specified. For example, only one <tt>cl::ConsumeAfter</tt> can be specified
+ per program, there must be at least one <a href="#positional">positional
+ argument</a> specified, and the <tt>cl::ConsumeAfter</tt> option should be a <a
+ href="#cl::list">cl::list</a> option.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="subsection">
+ <a name="storage">Internal vs External Storage</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>By default, all command line options automatically hold the value that they
+ parse from the command line. This is very convenient in the common case,
+ especially when combined with the ability to define command line options in the
+ files that use them. This is called the internal storage model.</p>
+
+ <p>Sometimes, however, it is nice to separate the command line option processing
+ code from the storage of the value parsed. For example, lets say that we have a
+ '<tt>-debug</tt>' option that we would like to use to enable debug information
+ across the entire body of our program. In this case, the boolean value
+ controlling the debug code should be globally accessable (in a header file, for
+ example) yet the command line option processing code should not be exposed to
+ all of these clients (requiring lots of .cpp files to #include
+ <tt>CommandLine.h</tt>).</p>
+
+ <p>To do this, set up your .h file with your option, like this for example:</p>
+
+ <pre>
+ <i>// DebugFlag.h - Get access to the '-debug' command line option
+ //
+
+ // DebugFlag - This boolean is set to true if the '-debug' command line option
+ // is specified. This should probably not be referenced directly, instead, use
+ // the DEBUG macro below.
+ //</i>
+ extern bool DebugFlag;
+
+ <i>// DEBUG macro - This macro should be used by code to emit debug information.
+ // In the '-debug' option is specified on the command line, and if this is a
+ // debug build, then the code specified as the option to the macro will be
+ // executed. Otherwise it will not be. Example:
+ //
+ // DEBUG(cerr << "Bitset contains: " << Bitset << "\n");
+ //</i>
+ <span class="doc_red">#ifdef NDEBUG
+ #define DEBUG(X)
+ #else
+ #define DEBUG(X)</span> \
+ do { if (DebugFlag) { X; } } while (0)
+ <span class="doc_red">#endif</span>
+ </pre>
+
+ <p>This allows clients to blissfully use the <tt>DEBUG()</tt> macro, or the
+ <tt>DebugFlag</tt> explicitly if they want to. Now we just need to be able to
+ set the <tt>DebugFlag</tt> boolean when the option is set. To do this, we pass
+ an additial argument to our command line argument processor, and we specify
+ where to fill in with the <a href="#cl::location">cl::location</a>
+ attribute:</p>
+
+ <pre>
+ bool DebugFlag; <i>// the actual value</i>
+ static <a href="#cl::opt">cl::opt</a><bool, true> <i>// The parser</i>
+ Debug("<i>debug</i>", <a href="#cl::desc">cl::desc</a>("<i>Enable debug output</i>")</a>, <a href="#cl::Hidden">cl::Hidden</a>,
+ <a href="#cl::location">cl::location</a>(DebugFlag));
+ </pre>
+
+ <p>In the above example, we specify "<tt>true</tt>" as the second argument to
+ the <a href="#cl::opt">cl::opt</a> template, indicating that the template should
+ not maintain a copy of the value itself. In addition to this, we specify the <a
+ href="#cl::location">cl::location</a> attribute, so that <tt>DebugFlag</tt> is
+ automatically set.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="attributes">Option Attributes</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>This section describes the basic attributes that you can specify on
+ options.</p>
+
+ <ul>
+
+ <li>The option name attribute (which is required for all options, except <a
+ href="#positional">positional options</a>) specifies what the option name is.
+ This option is specified in simple double quotes:
+
+ <pre>
+ <a href="#cl::opt">cl::opt</a><<b>bool</b>> Quiet("<i>quiet</i>");
+ </pre>
+
+ </li>
+
+ <li><a name="cl::desc">The <b><tt>cl::desc</tt></b></a> attribute specifies a
+ description for the option to be shown in the <tt>--help</tt> output for the
+ program.</li>
+
+ <li><a name="cl::value_desc">The <b><tt>cl::value_desc</tt></b></a> attribute
+ specifies a string that can be used to fine tune the <tt>--help</tt> output for
+ a command line option. Look <a href="#value_desc_example">here</a> for an
+ example.</li>
+
+ <li><a name="cl::init">The <b><tt>cl::init</tt></b></a> attribute specifies an
+ inital value for a <a href="#cl::opt">scalar</a> option. If this attribute is
+ not specified then the command line option value defaults to the value created
+ by the default constructor for the type. <b>Warning</b>: If you specify both
+ <b><tt>cl::init</tt></b> and <b><tt>cl::location</tt></b> for an option,
+ you must specify <b><tt>cl::location</tt></b> first, so that when the
+ command-line parser sees <b><tt>cl::init</tt></b>, it knows where to put the
+ initial value. (You will get an error at runtime if you don't put them in
+ the right order.)</li>
+
+ <li><a name="cl::location">The <b><tt>cl::location</tt></b></a> attribute where to
+ store the value for a parsed command line option if using external storage. See
+ the section on <a href="#storage">Internal vs External Storage</a> for more
+ information.</li>
+
+ <li><a name="cl::aliasopt">The <b><tt>cl::aliasopt</tt></b></a> attribute
+ specifies which option a <a href="#cl::alias">cl::alias</a> option is an alias
+ for.</li>
+
+ <li><a name="cl::values">The <b><tt>cl::values</tt></b></a> attribute specifies
+ the string-to-value mapping to be used by the generic parser. It takes a
+ <b>null terminated</b> list of (option, value, description) triplets that
+ specify the option name, the value mapped to, and the description shown in the
+ <tt>--help</tt> for the tool. Because the generic parser is used most
+ frequently with enum values, two macros are often useful:
+
+ <ol>
+
+ <li><a name="clEnumVal">The <b><tt>clEnumVal</tt></b></a> macro is used as a
+ nice simple way to specify a triplet for an enum. This macro automatically
+ makes the option name be the same as the enum name. The first option to the
+ macro is the enum, the second is the description for the command line
+ option.</li>
+
+ <li><a name="clEnumValN">The <b><tt>clEnumValN</tt></b></a> macro is used to
+ specify macro options where the option name doesn't equal the enum name. For
+ this macro, the first argument is the enum value, the second is the flag name,
+ and the second is the description.</li>
+
+ </ol>
+
+ You will get a compile time error if you try to use cl::values with a parser
+ that does not support it.</li>
+
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="modifiers">Option Modifiers</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Option modifiers are the flags and expressions that you pass into the
+ constructors for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
+ href="#cl::list">cl::list</a></tt>. These modifiers give you the ability to
+ tweak how options are parsed and how <tt>--help</tt> output is generated to fit
+ your application well.</p>
+
+ <p>These options fall into five main catagories:</p>
+
+ <ol>
+ <li><a href="#hiding">Hiding an option from <tt>--help</tt> output</a></li>
+ <li><a href="#numoccurrences">Controlling the number of occurrences
+ required and allowed</a></li>
+ <li><a href="#valrequired">Controlling whether or not a value must be
+ specified</a></li>
+ <li><a href="#formatting">Controlling other formatting options</a></li>
+ <li><a href="#misc">Miscellaneous option modifiers</a></li>
+ </ol>
+
+ <p>It is not possible to specify two options from the same catagory (you'll get
+ a runtime error) to a single option, except for options in the miscellaneous
+ catagory. The CommandLine library specifies defaults for all of these settings
+ that are the most useful in practice and the most common, which mean that you
+ usually shouldn't have to worry about these.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="hiding">Hiding an option from <tt>--help</tt> output</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>cl::NotHidden</tt>, <tt>cl::Hidden</tt>, and
+ <tt>cl::ReallyHidden</tt> modifiers are used to control whether or not an option
+ appears in the <tt>--help</tt> and <tt>--help-hidden</tt> output for the
+ compiled program:</p>
+
+ <ul>
+
+ <li><a name="cl::NotHidden">The <b><tt>cl::NotHidden</tt></b></a> modifier
+ (which is the default for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
+ href="#cl::list">cl::list</a></tt> options), indicates the option is to appear
+ in both help listings.</li>
+
+ <li><a name="cl::Hidden">The <b><tt>cl::Hidden</tt></b></a> modifier (which is the
+ default for <tt><a href="#cl::alias">cl::alias</a></tt> options), indicates that
+ the option should not appear in the <tt>--help</tt> output, but should appear in
+ the <tt>--help-hidden</tt> output.</li>
+
+ <li><a name="cl::ReallyHidden">The <b><tt>cl::ReallyHidden</tt></b></a> modifier,
+ indicates that the option should not appear in any help output.</li>
+
+ </ul>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="numoccurrences">Controlling the number of occurrences required and
+ allowed</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>This group of options is used to control how many time an option is allowed
+ (or required) to be specified on the command line of your program. Specifying a
+ value for this setting allows the CommandLine library to do error checking for
+ you.</p>
+
+ <p>The allowed values for this option group are:</p>
+
+ <ul>
+
+ <li><a name="cl::Optional">The <b><tt>cl::Optional</tt></b></a> modifier (which
+ is the default for the <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
+ href="#cl::alias">cl::alias</a></tt> classes) indicates that your program will
+ allow either zero or one occurrence of the option to be specified.</li>
+
+ <li><a name="cl::ZeroOrMore">The <b><tt>cl::ZeroOrMore</tt></b></a> modifier
+ (which is the default for the <tt><a href="#cl::list">cl::list</a></tt> class)
+ indicates that your program will allow the option to be specified zero or more
+ times.</li>
+
+ <li><a name="cl::Required">The <b><tt>cl::Required</tt></b></a> modifier
+ indicates that the specified option must be specified exactly one time.</li>
+
+ <li><a name="cl::OneOrMore">The <b><tt>cl::OneOrMore</tt></b></a> modifier
+ indicates that the option must be specified at least one time.</li>
+
+ <li>The <b><tt>cl::ConsumeAfter</tt></b> modifier is described in the <a
+ href="#positional">Positional arguments section</a></li>
+
+ </ul>
+
+ <p>If an option is not specified, then the value of the option is equal to the
+ value specified by the <tt><a href="#cl::init">cl::init</a></tt> attribute. If
+ the <tt><a href="#cl::init">cl::init</a></tt> attribute is not specified, the
+ option value is initialized with the default constructor for the data type.</p>
+
+ <p>If an option is specified multiple times for an option of the <tt><a
+ href="#cl::opt">cl::opt</a></tt> class, only the last value will be
+ retained.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="valrequired">Controlling whether or not a value must be specified</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>This group of options is used to control whether or not the option allows a
+ value to be present. In the case of the CommandLine library, a value is either
+ specified with an equal sign (e.g. '<tt>-index-depth=17</tt>') or as a trailing
+ string (e.g. '<tt>-o a.out</tt>').</p>
+
+ <p>The allowed values for this option group are:</p>
+
+ <ul>
+
+ <li><a name="cl::ValueOptional">The <b><tt>cl::ValueOptional</tt></b></a> modifier
+ (which is the default for <tt>bool</tt> typed options) specifies that it is
+ acceptable to have a value, or not. A boolean argument can be enabled just by
+ appearing on the command line, or it can have an explicit '<tt>-foo=true</tt>'.
+ If an option is specified with this mode, it is illegal for the value to be
+ provided without the equal sign. Therefore '<tt>-foo true</tt>' is illegal. To
+ get this behavior, you must use the <a
+ href="#cl::ValueRequired">cl::ValueRequired</a> modifier.</li>
+
+ <li><a name="cl::ValueRequired">The <b><tt>cl::ValueRequired</tt></b></a> modifier
+ (which is the default for all other types except for <a
+ href="#onealternative">unnamed alternatives using the generic parser</a>)
+ specifies that a value must be provided. This mode informs the command line
+ library that if an option is not provides with an equal sign, that the next
+ argument provided must be the value. This allows things like '<tt>-o
+ a.out</tt>' to work.</li>
+
+ <li><a name="cl::ValueDisallowed">The <b><tt>cl::ValueDisallowed</tt></b></a>
+ modifier (which is the default for <a href="#onealternative">unnamed
+ alternatives using the generic parser</a>) indicates that it is a runtime error
+ for the user to specify a value. This can be provided to disallow users from
+ providing options to boolean options (like '<tt>-foo=true</tt>').</li>
+
+ </ul>
+
+ <p>In general, the default values for this option group work just like you would
+ want them to. As mentioned above, you can specify the <a
+ href="#cl::ValueDisallowed">cl::ValueDisallowed</a> modifier to a boolean
+ argument to restrict your command line parser. These options are mostly useful
+ when <a href="#extensionguide">extending the library</a>.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="formatting">Controlling other formatting options</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The formatting option group is used to specify that the command line option
+ has special abilities and is otherwise different from other command line
+ arguments. As usual, you can only specify at most one of these arguments.</p>
+
+ <ul>
+
+ <li><a name="cl::NormalFormatting">The <b><tt>cl::NormalFormatting</tt></b></a>
+ modifier (which is the default all options) specifies that this option is
+ "normal".</li>
+
+ <li><a name="cl::Positional">The <b><tt>cl::Positional</tt></b></a> modifier
+ specifies that this is a positional argument, that does not have a command line
+ option associated with it. See the <a href="#positional">Positional
+ Arguments</a> section for more information.</li>
+
+ <li>The <b><a href="#cl::ConsumeAfter"><tt>cl::ConsumeAfter</tt></a></b> modifier
+ specifies that this option is used to capture "interpreter style" arguments. See <a href="#cl::ConsumeAfter">this section for more information</a>.</li>
+
+ <li><a name="cl::Prefix">The <b><tt>cl::Prefix</tt></b></a> modifier specifies
+ that this option prefixes its value. With 'Prefix' options, there is no equal
+ sign that separates the value from the option name specified. This is useful
+ for processing odd arguments like '<tt>-lmalloc -L/usr/lib'</tt> in a linker
+ tool. Here, the '<tt>l</tt>' and '<tt>L</tt>' options are normal string (list)
+ options, that have the <a href="#cl::Prefix">cl::Prefix</a> modifier added to
+ allow the CommandLine library to recognize them. Note that <a
+ href="#cl::Prefix">cl::Prefix</a> options must not have the <a
+ href="#cl::ValueDisallowed">cl::ValueDisallowed</a> modifier specified.</li>
+
+ <li><a name="cl::Grouping">The <b><tt>cl::Grouping</tt></b></a> modifier is used
+ to implement unix style tools (like <tt>ls</tt>) that have lots of single letter
+ arguments, but only require a single dash. For example, the '<tt>ls -labF</tt>'
+ command actually enables four different options, all of which are single
+ letters. Note that <a href="#cl::Grouping">cl::Grouping</a> options cannot have
+ values.</li>
+
+ </ul>
+
+ <p>The CommandLine library does not restrict how you use the <a
+ href="#cl::Prefix">cl::Prefix</a> or <a href="#cl::Grouping">cl::Grouping</a>
+ modifiers, but it is possible to specify ambiguous argument settings. Thus, it
+ is possible to have multiple letter options that are prefix or grouping options,
+ and they will still work as designed.</p>
+
+ <p>To do this, the CommandLine library uses a greedy algorithm to parse the
+ input option into (potentially multiple) prefix and grouping options. The
+ strategy basically looks like this:</p>
+
+ <p><tt>parse(string OrigInput) {</tt>
+ <ol>
+ <li><tt>string input = OrigInput;</tt>
+ <li><tt>if (isOption(input)) return getOption(input).parse();</tt> <i>// Normal option</i>
+ <li><tt>while (!isOption(input) && !input.empty()) input.pop_back();</tt> <i>// Remove the last letter</i>
+ <li><tt>if (input.empty()) return error();</tt> <i>// No matching option</i>
+ <li><tt>if (getOption(input).isPrefix())<br>
+ return getOption(input).parse(input);</tt>
+ <li><tt>while (!input.empty()) { <i>// Must be grouping options</i><br>
+ getOption(input).parse();<br>
+ OrigInput.erase(OrigInput.begin(), OrigInput.begin()+input.length());<br>
+ input = OrigInput;<br>
+ while (!isOption(input) && !input.empty()) input.pop_back();<br>
+ }</tt>
+ <li><tt>if (!OrigInput.empty()) error();</tt>
+ </tt>
+
+ </ol>
+ <tt>}</tt></p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="misc">Miscellaneous option modifiers</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The miscellaneous option modifiers are the only flags where you can specify
+ more than one flag from the set: they are not mutually exclusive. These flags
+ specify boolean properties that modify the option.</p>
+
+ <ul>
+
+ <li><a name="cl::CommaSeparated">The <b><tt>cl::CommaSeparated</tt></b></a> modifier
+ indicates that any commas specified for an option's value should be used to
+ split the value up into multiple values for the option. For example, these two
+ options are equivalent when <tt>cl::CommaSeparated</tt> is specified:
+ "<tt>-foo=a -foo=b -foo=c</tt>" and "<tt>-foo=a,b,c</tt>". This option only
+ makes sense to be used in a case where the option is allowed to accept one or
+ more values (i.e. it is a <a href="#cl::list">cl::list</a> option).</li>
+
+ </ul>
+
+ <p>So far, the only miscellaneous option modifier is the
+ <tt>cl::CommaSeparated</tt> modifier.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="toplevel">Top-Level Classes and Functions</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Despite all of the built-in flexibility, the CommandLine option library
+ really only consists of one function (<a
+ href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>)
+ and three main classes: <a href="#cl::opt"><tt>cl::opt</tt></a>, <a
+ href="#cl::list"><tt>cl::list</tt></a>, and <a
+ href="#cl::alias"><tt>cl::alias</tt></a>. This section describes these three
+ classes in detail.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="cl::ParseCommandLineOptions">The <tt>cl::ParseCommandLineOptions</tt>
+ function</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>cl::ParseCommandLineOptions</tt> function is designed to be called
+ directly from <tt>main</tt>, and is used to fill in the values of all of the
+ command line option variables once <tt>argc</tt> and <tt>argv</tt> are
+ available.</p>
+
+ <p>The <tt>cl::ParseCommandLineOptions</tt> function requires two parameters
+ (<tt>argc</tt> and <tt>argv</tt>), but may also take an optional third parameter
+ which holds <a href="#description">additional extra text</a> to emit when the
+ <tt>--help</tt> option is invoked.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="cl::ParseEnvironmentOptions">The <tt>cl::ParseEnvironmentOptions</tt>
+ function</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>cl::ParseEnvironmentOptions</tt> function has mostly the same effects
+ as <a
+ href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>,
+ except that it is designed to take values for options from an environment
+ variable, for those cases in which reading the command line is not convenient or
+ not desired. It fills in the values of all the command line option variables
+ just like <a
+ href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>
+ does.</p>
+
+ <p>It takes three parameters: first, the name of the program (since
+ <tt>argv</tt> may not be available, it can't just look in <tt>argv[0]</tt>),
+ second, the name of the environment variable to examine, and third, the optional
+ <a href="#description">additional extra text</a> to emit when the
+ <tt>--help</tt> option is invoked.</p>
+
+ <p><tt>cl::ParseEnvironmentOptions</tt> will break the environment
+ variable's value up into words and then process them using
+ <a href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>.
+ <b>Note:</b> Currently <tt>cl::ParseEnvironmentOptions</tt> does not support
+ quoting, so an environment variable containing <tt>-option "foo bar"</tt> will
+ be parsed as three words, <tt>-option</tt>, <tt>"foo</tt>, and <tt>bar"</tt>,
+ which is different from what you would get from the shell with the same
+ input.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="cl::opt">The <tt>cl::opt</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>cl::opt</tt> class is the class used to represent scalar command line
+ options, and is the one used most of the time. It is a templated class which
+ can take up to three arguments (all except for the first have default values
+ though):</p>
+
+ <pre>
+ <b>namespace</b> cl {
+ <b>template</b> <<b>class</b> DataType, <b>bool</b> ExternalStorage = <b>false</b>,
+ <b>class</b> ParserClass = parser<DataType> >
+ <b>class</b> opt;
+ }
+ </pre>
+
+ <p>The first template argument specifies what underlying data type the command
+ line argument is, and is used to select a default parser implementation. The
+ second template argument is used to specify whether the option should contain
+ the storage for the option (the default) or whether external storage should be
+ used to contain the value parsed for the option (see <a href="#storage">Internal
+ vs External Storage</a> for more information).</p>
+
+ <p>The third template argument specifies which parser to use. The default value
+ selects an instantiation of the <tt>parser</tt> class based on the underlying
+ data type of the option. In general, this default works well for most
+ applications, so this option is only used when using a <a
+ href="#customparser">custom parser</a>.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="cl::list">The <tt>cl::list</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>cl::list</tt> class is the class used to represent a list of command
+ line options. It too is a templated class which can take up to three
+ arguments:</p>
+
+ <pre>
+ <b>namespace</b> cl {
+ <b>template</b> <<b>class</b> DataType, <b>class</b> Storage = <b>bool</b>,
+ <b>class</b> ParserClass = parser<DataType> >
+ <b>class</b> list;
+ }
+ </pre>
+
+ <p>This class works the exact same as the <a
+ href="#cl::opt"><tt>cl::opt</tt></a> class, except that the second argument is
+ the <b>type</b> of the external storage, not a boolean value. For this class,
+ the marker type '<tt>bool</tt>' is used to indicate that internal storage should
+ be used.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="cl::alias">The <tt>cl::alias</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>cl::alias</tt> class is a nontemplated class that is used to form
+ aliases for other arguments.</p>
+
+ <pre>
+ <b>namespace</b> cl {
+ <b>class</b> alias;
+ }
+ </pre>
+
+ <p>The <a href="#cl::aliasopt"><tt>cl::aliasopt</tt></a> attribute should be
+ used to specify which option this is an alias for. Alias arguments default to
+ being <a href="#cl::Hidden">Hidden</a>, and use the aliased options parser to do
+ the conversion from string to data.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="builtinparsers">Builtin parsers</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Parsers control how the string value taken from the command line is
+ translated into a typed value, suitable for use in a C++ program. By default,
+ the CommandLine library uses an instance of <tt>parser<type></tt> if the
+ command line option specifies that it uses values of type '<tt>type</tt>'.
+ Because of this, custom option processing is specified with specializations of
+ the '<tt>parser</tt>' class.</p>
+
+ <p>The CommandLine library provides the following builtin parser
+ specializations, which are sufficient for most applications. It can, however,
+ also be extended to work with new data types and new ways of interpreting the
+ same data. See the <a href="#customparser">Writing a Custom Parser</a> for more
+ details on this type of library extension.</p>
+
+ <ul>
+
+ <li><a name="genericparser">The <b>generic <tt>parser<t></tt> parser</b></a>
+ can be used to map strings values to any data type, through the use of the <a
+ href="#cl::values">cl::values</a> property, which specifies the mapping
+ information. The most common use of this parser is for parsing enum values,
+ which allows you to use the CommandLine library for all of the error checking to
+ make sure that only valid enum values are specified (as opposed to accepting
+ arbitrary strings). Despite this, however, the generic parser class can be used
+ for any data type.</li>
+
+ <li><a name="boolparser">The <b><tt>parser<bool></tt> specialization</b></a>
+ is used to convert boolean strings to a boolean value. Currently accepted
+ strings are "<tt>true</tt>", "<tt>TRUE</tt>", "<tt>True</tt>", "<tt>1</tt>",
+ "<tt>false</tt>", "<tt>FALSE</tt>", "<tt>False</tt>", and "<tt>0</tt>".</li>
+
+ <li><a name="stringparser">The <b><tt>parser<string></tt>
+ specialization</b></a> simply stores the parsed string into the string value
+ specified. No conversion or modification of the data is performed.</li>
+
+ <li><a name="intparser">The <b><tt>parser<int></tt> specialization</b></a>
+ uses the C <tt>strtol</tt> function to parse the string input. As such, it will
+ accept a decimal number (with an optional '+' or '-' prefix) which must start
+ with a non-zero digit. It accepts octal numbers, which are identified with a
+ '<tt>0</tt>' prefix digit, and hexadecimal numbers with a prefix of
+ '<tt>0x</tt>' or '<tt>0X</tt>'.</li>
+
+ <li><a name="doubleparser">The <b><tt>parser<double></tt></b></a> and
+ <b><tt>parser<float></tt> specializations</b> use the standard C
+ <tt>strtod</tt> function to convert floating point strings into floating point
+ values. As such, a broad range of string formats is supported, including
+ exponential notation (ex: <tt>1.7e15</tt>) and properly supports locales.
+ </li>
+
+ </ul>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="extensionguide">Extension Guide</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Although the CommandLine library has a lot of functionality built into it
+ already (as discussed previously), one of its true strengths lie in its
+ extensibility. This section discusses how the CommandLine library works under
+ the covers and illustrates how to do some simple, common, extensions.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="customparser">Writing a custom parser</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>One of the simplest and most common extensions is the use of a custom parser.
+ As <a href="#builtinparsers">discussed previously</a>, parsers are the portion
+ of the CommandLine library that turns string input from the user into a
+ particular parsed data type, validating the input in the process.</p>
+
+ <p>There are two ways to use a new parser:</p>
+
+ <ol>
+
+ <li>
+
+ <p>Specialize the <a href="#genericparser"><tt>cl::parser</tt></a> template for
+ your custom data type.<p>
+
+ <p>This approach has the advantage that users of your custom data type will
+ automatically use your custom parser whenever they define an option with a value
+ type of your data type. The disadvantage of this approach is that it doesn't
+ work if your fundemental data type is something that is already supported.</p>
+
+ </li>
+
+ <li>
+
+ <p>Write an independent class, using it explicitly from options that need
+ it.</p>
+
+ <p>This approach works well in situations where you would line to parse an
+ option using special syntax for a not-very-special data-type. The drawback of
+ this approach is that users of your parser have to be aware that they are using
+ your parser, instead of the builtin ones.</p>
+
+ </li>
+
+ </ol>
+
+ <p>To guide the discussion, we will discuss a custom parser that accepts file
+ sizes, specified with an optional unit after the numeric size. For example, we
+ would like to parse "102kb", "41M", "1G" into the appropriate integer value. In
+ this case, the underlying data type we want to parse into is
+ '<tt>unsigned</tt>'. We choose approach #2 above because we don't want to make
+ this the default for all <tt>unsigned</tt> options.</p>
+
+ <p>To start out, we declare our new <tt>FileSizeParser</tt> class:</p>
+
+ <pre>
+ <b>struct</b> FileSizeParser : <b>public</b> cl::basic_parser<<b>unsigned</b>> {
+ <i>// parse - Return true on error.</i>
+ <b>bool</b> parse(cl::Option &O, <b>const char</b> *ArgName, <b>const</b> std::string &ArgValue,
+ <b>unsigned</b> &Val);
+ };
+ </pre>
+
+ <p>Our new class inherits from the <tt>cl::basic_parser</tt> template class to
+ fill in the default, boiler plate, code for us. We give it the data type that
+ we parse into (the last argument to the <tt>parse</tt> method so that clients of
+ our custom parser know what object type to pass in to the parse method (here we
+ declare that we parse into '<tt>unsigned</tt>' variables.</p>
+
+ <p>For most purposes, the only method that must be implemented in a custom
+ parser is the <tt>parse</tt> method. The <tt>parse</tt> method is called
+ whenever the option is invoked, passing in the option itself, the option name,
+ the string to parse, and a reference to a return value. If the string to parse
+ is not well formed, the parser should output an error message and return true.
+ Otherwise it should return false and set '<tt>Val</tt>' to the parsed value. In
+ our example, we implement <tt>parse</tt> as:</p>
+
+ <pre>
+ <b>bool</b> FileSizeParser::parse(cl::Option &O, <b>const char</b> *ArgName,
+ <b>const</b> std::string &Arg, <b>unsigned</b> &Val) {
+ <b>const char</b> *ArgStart = Arg.c_str();
+ <b>char</b> *End;
+
+ <i>// Parse integer part, leaving 'End' pointing to the first non-integer char</i>
+ Val = (unsigned)strtol(ArgStart, &End, 0);
+
+ <b>while</b> (1) {
+ <b>switch</b> (*End++) {
+ <b>case</b> 0: <b>return</b> false; <i>// No error</i>
+ <b>case</b> 'i': <i>// Ignore the 'i' in KiB if people use that</i>
+ <b>case</b> 'b': <b>case</b> 'B': <i>// Ignore B suffix</i>
+ <b>break</b>;
+
+ <b>case</b> 'g': <b>case</b> 'G': Val *= 1024*1024*1024; <b>break</b>;
+ <b>case</b> 'm': <b>case</b> 'M': Val *= 1024*1024; <b>break</b>;
+ <b>case</b> 'k': <b>case</b> 'K': Val *= 1024; <b>break</b>;
+
+ default:
+ <i>// Print an error message if unrecognized character!</i>
+ <b>return</b> O.error(": '" + Arg + "' value invalid for file size argument!");
+ }
+ }
+ }
+ </pre>
+
+ <p>This function implements a very simple parser for the kinds of strings we are
+ interested in. Although it has some holes (it allows "<tt>123KKK</tt>" for
+ example), it is good enough for this example. Note that we use the option
+ itself to print out the error message (the <tt>error</tt> method always returns
+ true) in order to get a nice error message (shown below). Now that we have our
+ parser class, we can use it like this:</p>
+
+ <pre>
+ <b>static</b> <a href="#cl::opt">cl::opt</a><<b>unsigned</b>, <b>false</b>, FileSizeParser>
+ MFS(<i>"max-file-size"</i>, <a href="#cl::desc">cl::desc</a>(<i>"Maximum file size to accept"</i>),
+ <a href="#cl::value_desc">cl::value_desc</a>("<i>size</i>"));
+ </pre>
+
+ <p>Which adds this to the output of our program:</p>
+
+ <pre>
+ OPTIONS:
+ -help - display available options (--help-hidden for more)
+ ...
+ <b>-max-file-size=<size> - Maximum file size to accept</b>
+ </pre>
+
+ <p>And we can test that our parse works correctly now (the test program just
+ prints out the max-file-size argument value):</p>
+
+ <pre>
+ $ ./test
+ MFS: 0
+ $ ./test -max-file-size=123MB
+ MFS: 128974848
+ $ ./test -max-file-size=3G
+ MFS: 3221225472
+ $ ./test -max-file-size=dog
+ -max-file-size option: 'dog' value invalid for file size argument!
+ </pre>
+
+ <p>It looks like it works. The error message that we get is nice and helpful,
+ and we seem to accept reasonable file sizes. This wraps up the "custom parser"
+ tutorial.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="explotingexternal">Exploiting external storage</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>TODO: fill in this section</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="dynamicopts">Dynamically adding command line options</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>TODO: fill in this section</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+
+ <hr>
+ <div class="doc_footer">
+ <address><a href="mailto:sabre at nondot.org">Chris Lattner</a></address>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </div>
+
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/Debugging.gif
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>LLVM: Frequently Asked Questions</title>
+ <style>
+ @import url("llvm.css");
+ .question { font-weight: bold }
+ .answer { margin-left: 2em }
+ </style>
+ </head>
+ <body>
+
+ <div class="doc_title">
+ LLVM: Frequently Asked Questions
+ </div>
+
+ <ol>
+ <li><a href="#license">License</a>
+ <ol>
+ <li>Why are the LLVM source code and the front-end distributed under different
+ licenses?</li>
+ <li>Does the University of Illinois Open Source License really qualify as an
+ "open source" license?</li>
+ <li>Can I modify LLVM source code and redistribute the modified source?</li>
+ <li>Can I modify LLVM source code and redistribute binaries or other tools
+ based on it, without redistributing the source?</li>
+ </ol></li>
+
+ <li><a href="#source">Source code</a>
+ <ol>
+ <li>In what language is LLVM written?</li>
+ <li>How portable is the LLVM source code?</li>
+ </ol></li>
+
+ <li><a href="#build">Build Problems</a>
+ <ol>
+ <li>When I run configure, it finds the wrong C compiler.</li>
+ <li>I compile the code, and I get some error about <tt>/localhome</tt>.</li>
+ <li>The <tt>configure</tt> script finds the right C compiler, but it uses the
+ LLVM linker from a previous build. What do I do?</li>
+ <li>When creating a dynamic library, I get a strange GLIBC error.</li>
+ <li>I've updated my source tree from CVS, and now my build is trying to use a
+ file/directory that doesn't exist.</li>
+ <li>I've modified a Makefile in my source tree, but my build tree keeps using
+ the old version. What do I do?</li>
+ <li>I've upgraded to a new version of LLVM, and I get strange build
+ errors.</li>
+ <li>I've built LLVM and am testing it, but the tests freeze.</li>
+ <li>Why do test results differ when I perform different types of builds?</li>
+ <li>Compiling LLVM with GCC 3.3.2 fails, what should I do?</li>
+ <li>When I use the test suite, all of the C Backend tests fail. What is
+ wrong?</li>
+ </ol></li>
+
+ <li><a href="#cfe">Using the GCC Front End</a>
+ <ol>
+ <li>
+ When I compile software that uses a configure script, the configure script
+ thinks my system has all of the header files and libraries it is testing
+ for. How do I get configure to work correctly?
+ </li>
+
+ <li>
+ When I compile code using the LLVM GCC front end, it complains that it
+ cannot find crtend.o.
+ </li>
+ </ol>
+ </li>
+
+ <li><a href="#cfe_code">Questions about code generated by the GCC front-end</a>
+ <ol>
+ <li>What is this <tt>__main()</tt> call that gets inserted into
+ <tt>main()</tt>?</li>
+ <li>Where did all of my code go??</li>
+ </ol>
+ </li>
+ </ol>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="license">License</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="question">
+ <p>Why are the LLVM source code and the front-end distributed under different
+ licenses?</p>
+ </div>
+
+ <div class="answer">
+ <p>The C/C++ front-ends are based on GCC and must be distributed under the GPL.
+ Our aim is to distribute LLVM source code under a <em>much less restrictive</em>
+ license, in particular one that does not compel users who distribute tools based
+ on modifying the source to redistribute the modified source code as well.</p>
+ </div>
+
+ <div class="question">
+ <p>Does the University of Illinois Open Source License really qualify as an
+ "open source" license?</p>
+ </div>
+
+ <div class="answer">
+ <p>Yes, the license is <a
+ href="http://www.opensource.org/licenses/UoI-NCSA.php">certified</a> by the Open
+ Source Initiative (OSI).</p>
+ </div>
+
+ <div class="question">
+ <p>Can I modify LLVM source code and redistribute the modified source?</p>
+ </div>
+
+ <div class="answer">
+ <p>Yes. The modified source distribution must retain the copyright notice and
+ follow the three bulletted conditions listed in the <a
+ href="http://llvm.cs.uiuc.edu/releases/1.2/LICENSE.TXT">LLVM license</a>.</p>
+ </div>
+
+ <div class="question">
+ <p>Can I modify LLVM source code and redistribute binaries or other tools based
+ on it, without redistributing the source?</p>
+ </div>
+
+ <div class="answer">
+ <p>Yes, this is why we distribute LLVM under a less restrictive license than
+ GPL, as explained in the first question above.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="source">Source Code</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="question">
+ <p>In what language is LLVM written?</p>
+ </div>
+
+ <div class="answer">
+ <p>All of the LLVM tools and libraries are written in C++ with extensive use of
+ the STL.</p>
+ </div>
+
+ <div class="question">
+ <p>How portable is the LLVM source code?</p>
+ </div>
+
+ <div class="answer">
+ <p>The LLVM source code should be portable to most modern UNIX-like operating
+ systems. Most of the code is written in standard C++ with operating system
+ services abstracted to a support library. The tools required to build and test
+ LLVM have been ported to a plethora of platforms.</p>
+
+ <p>Some porting problems may exist in the following areas:</p>
+
+ <ul>
+
+ <li>The GCC front end code is not as portable as the LLVM suite, so it may not
+ compile as well on unsupported platforms.</li>
+
+ <li>The Python test classes are more UNIX-centric than they should be, so
+ porting to non-UNIX like platforms (i.e. Windows, MacOS 9) will require some
+ effort.</li>
+
+ <li>The LLVM build system relies heavily on UNIX shell tools, like the Bourne
+ Shell and sed. Porting to systems without these tools (MacOS 9, Plan 9) will
+ require more effort.</li>
+
+ </ul>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="build">Build Problems</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="question">
+ <p>When I run configure, it finds the wrong C compiler.</p>
+ </div>
+
+ <div class="answer">
+
+ <p>The <tt>configure</tt> script attempts to locate first <tt>gcc</tt> and then
+ <tt>cc</tt>, unless it finds compiler paths set in <tt>CC</tt> and <tt>CXX</tt>
+ for the C and C++ compiler, respectively.</p>
+
+ <p>If <tt>configure</tt> finds the wrong compiler, either adjust your
+ <tt>PATH</tt> environment variable or set <tt>CC</tt> and <tt>CXX</tt>
+ explicitly.</p>
+
+ </div>
+
+ <div class="question">
+ <p>I compile the code, and I get some error about <tt>/localhome</tt>.</p>
+ </div>
+
+ <div class="answer">
+
+ <p>There are several possible causes for this. The first is that you didn't set
+ a pathname properly when using <tt>configure</tt>, and it defaulted to a
+ pathname that we use on our research machines.</p>
+
+ <p>Another possibility is that we hardcoded a path in our Makefiles. If you see
+ this, please email the LLVM bug mailing list with the name of the offending
+ Makefile and a description of what is wrong with it.</p>
+
+ </div>
+
+ <div class="question">
+ <p>The <tt>configure</tt> script finds the right C compiler, but it uses the
+ LLVM linker from a previous build. What do I do?</p>
+ </div>
+
+ <div class="answer">
+ <p>The <tt>configure</tt> script uses the <tt>PATH</tt> to find executables, so
+ if it's grabbing the wrong linker/assembler/etc, there are two ways to fix
+ it:</p>
+
+ <ol>
+
+ <li><p>Adjust your <tt>PATH</tt> environment variable so that the correct
+ program appears first in the <tt>PATH</tt>. This may work, but may not be
+ convenient when you want them <i>first</i> in your path for other
+ work.</p></li>
+
+ <li><p>Run <tt>configure</tt> with an alternative <tt>PATH</tt> that is
+ correct. In a Borne compatible shell, the syntax would be:</p>
+
+ <p><tt>PATH=<the path without the bad program> ./configure ...</tt></p>
+
+ <p>This is still somewhat inconvenient, but it allows <tt>configure</tt>
+ to do its work without having to adjust your <tt>PATH</tt>
+ permanently.</p></li>
+
+ </ol>
+
+ </div>
+
+ <div class="question">
+ <p>When creating a dynamic library, I get a strange GLIBC error.</p>
+ </div>
+
+ <div class="answer">
+ <p>Under some operating systems (i.e. Linux), libtool does not work correctly if
+ GCC was compiled with the --disable-shared option. To work around this, install
+ your own version of GCC that has shared libraries enabled by default.</p>
+ </div>
+
+ <div class="question">
+ <p>I've updated my source tree from CVS, and now my build is trying to use a
+ file/directory that doesn't exist.</p>
+ </div>
+
+ <div class="answer">
+ <p>You need to re-run configure in your object directory. When new Makefiles
+ are added to the source tree, they have to be copied over to the object tree in
+ order to be used by the build.</p>
+ </div>
+
+ <div class="question">
+ <p>I've modified a Makefile in my source tree, but my build tree keeps using the
+ old version. What do I do?</p>
+ </div>
+
+ <div class="answer">
+
+ <p>If the Makefile already exists in your object tree, you
+ can just run the following command in the top level directory of your object
+ tree:</p>
+
+ <p><tt>./config.status <relative path to Makefile></tt><p>
+
+ <p>If the Makefile is new, you will have to modify the configure script to copy
+ it over.</p>
+
+ </div>
+
+ <div class="question">
+ <p>I've upgraded to a new version of LLVM, and I get strange build errors.</p>
+ </div>
+
+ <div class="answer">
+
+ <p>Sometimes, changes to the LLVM source code alters how the build system works.
+ Changes in libtool, autoconf, or header file dependencies are especially prone
+ to this sort of problem.</p>
+
+ <p>The best thing to try is to remove the old files and re-build. In most
+ cases, this takes care of the problem. To do this, just type <tt>make
+ clean</tt> and then <tt>make</tt> in the directory that fails to build.</p>
+
+ </div>
+
+ <div class="question">
+ <p>I've built LLVM and am testing it, but the tests freeze.</p>
+ </div>
+
+ <div class="answer">
+
+ <p>This is most likely occurring because you built a profile or release
+ (optimized) build of LLVM and have not specified the same information on the
+ <tt>gmake</tt> command line.</p>
+
+ <p>For example, if you built LLVM with the command:</p>
+
+ <p><tt>gmake ENABLE_PROFILING=1</tt>
+
+ <p>...then you must run the tests with the following commands:</p>
+
+ <p><tt>cd llvm/test<br>gmake ENABLE_PROFILING=1</tt></p>
+
+ </div>
+
+ <div class="question">
+ <p>Why do test results differ when I perform different types of builds?</p>
+ </div>
+
+ <div class="answer">
+
+ <p>The LLVM test suite is dependent upon several features of the LLVM tools and
+ libraries.</p>
+
+ <p>First, the debugging assertions in code are not enabled in optimized or
+ profiling builds. Hence, tests that used to fail may pass.</p>
+
+ <p>Second, some tests may rely upon debugging options or behavior that is only
+ available in the debug build. These tests will fail in an optimized or profile
+ build.</p>
+
+ </div>
+
+ <div class="question">
+ <p>Compiling LLVM with GCC 3.3.2 fails, what should I do?</p>
+ </div>
+
+ <div class="answer">
+ <p>This is <a href="http://gcc.gnu.org/PR?13392">a bug in GCC</a>, and
+ affects projects other than LLVM. Try upgrading or downgrading your GCC.</p>
+ </div>
+
+ <div class="question">
+ <p>
+ When I use the test suite, all of the C Backend tests fail. What is
+ wrong?
+ </p>
+ </div>
+
+ <div class="answer">
+ <p>
+ If you build LLVM and the C Backend tests fail in <tt>llvm/test/Programs</tt>,
+ then chances are good that the directory pointed to by the LLVM_LIB_SEARCH_PATH
+ environment variable does not contain the libcrtend.a library.
+ </p>
+
+ <p>
+ To fix it, verify that LLVM_LIB_SEARCH_PATH points to the correct directory
+ and that libcrtend.a is inside. For pre-built LLVM GCC front ends, this
+ should be the absolute path to
+ <tt>cfrontend/<<i>platform</i>>/llvm-gcc/bytecode-libs</tt>. If you've
+ built your own LLVM GCC front end, then ensure that you've built and installed
+ the libraries in <tt>llvm/runtime</tt> and have LLVM_LIB_SEARCH_PATH pointing
+ to the <tt>LLVMGCCDIR/bytecode-libs</tt> subdirectory.
+ </p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="cfe">Using the GCC Front End</a>
+ </div>
+
+ <div class="question">
+ <p>
+ When I compile software that uses a configure script, the configure script
+ thinks my system has all of the header files and libraries it is testing for.
+ How do I get configure to work correctly?
+ </p>
+ </div>
+
+ <div class="answer">
+ <p>
+ The configure script is getting things wrong because the LLVM linker allows
+ symbols to be undefined at link time (so that they can be resolved during JIT
+ or translation to the C back end). That is why configure thinks your system
+ "has everything."
+ </p>
+ <p>
+ To work around this, perform the following steps:
+ </p>
+
+ <ol>
+ <li>
+ Make sure the CC and CXX environment variables contains the full path to the
+ LLVM GCC front end.
+ </li>
+
+ <li>
+ Make sure that the regular C compiler is first in your PATH.
+ </li>
+
+ <li>
+ Add the string "-Wl,-native" to your CFLAGS environment variable.
+ </li>
+ </ol>
+
+ <p>
+ This will allow the gccld linker to create a native code executable instead of
+ a shell script that runs the JIT. Creating native code requires standard
+ linkage, which in turn will allow the configure script to find out if code is
+ not linking on your system because the feature isn't available on your system.
+ </p>
+ </div>
+
+ <div class="question">
+ <p>
+ When I compile code using the LLVM GCC front end, it complains that it cannot
+ find libcrtend.a.
+ </p>
+ </div>
+
+ <div class="answer">
+ <p>
+ In order to find libcrtend.a, you must have the directory in which it lives in
+ your LLVM_LIB_SEARCH_PATH environment variable. For the binary distribution of
+ the LLVM GCC front end, this will be the full path of the bytecode-libs
+ directory inside of the LLVM GCC distribution.
+ </p>
+ </div>
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="cfe_code">Questions about code generated by the GCC front-end</a>
+ </div>
+
+ <div class="question"><p>
+ What is this <tt>__main()</tt> call that gets inserted into <tt>main()</tt>?
+ </p></div>
+
+ <div class="answer">
+ <p>
+ The <tt>__main</tt> call is inserted by the C/C++ compiler in order to guarantee
+ that static constructors and destructors are called when the program starts up
+ and shuts down. In C, you can create static constructors and destructors by
+ using GCC extensions, and in C++ you can do so by creating a global variable
+ whose class has a ctor or dtor.
+ </p>
+
+ <p>
+ The actual implementation of <tt>__main</tt> lives in the
+ <tt>llvm/runtime/GCCLibraries/crtend/</tt> directory in the source-base, and is
+ linked in automatically when you link the program.
+ </p>
+ </div>
+
+ <!--=========================================================================-->
+
+ <div class="question"><p>
+ Where did all of my code go??
+ </p></div>
+
+ <div class="answer">
+ <p>
+ If you are using the LLVM demo page, you may often wonder what happened to all
+ of the code that you typed in. Remember that the demo script is running the
+ code through the LLVM optimizers, so if your code doesn't actually do anything
+ useful, it might all be deleted.
+ </p>
+
+ <p>
+ To prevent this, make sure that the code is actually needed. For example, if
+ you are computing some expression, return the value from the function instead of
+ leaving it in a local variable. If you really want to constrain the optimizer,
+ you can read from and assign to <tt>volatile</tt> global variables.
+ </p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <!-- *********************************************************************** -->
+
+ <hr>
+ <div class="doc_footer">
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </div>
+
+ </body>
+ </html>
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>Getting Started with LLVM System</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">
+ Getting Started with the LLVM System
+ </div>
+
+ <ul>
+ <li><a href="#overview">Overview</a>
+ <li><a href="#quickstart">Getting Started Quickly (A Summary)</a>
+ <li><a href="#requirements">Requirements</a>
+ <ol>
+ <li><a href="#hardware">Hardware</a>
+ <li><a href="#software">Software</a>
+ </ol></li>
+
+ <li><a href="#starting">Getting Started with LLVM</a>
+ <ol>
+ <li><a href="#terminology">Terminology and Notation</a>
+ <li><a href="#environment">Setting Up Your Environment</a>
+ <li><a href="#unpack">Unpacking the LLVM Archives</a>
+ <li><a href="#checkout">Checkout LLVM from CVS</a>
+ <li><a href="#installcf">Install the GCC Front End</a>
+ <li><a href="#config">Local LLVM Configuration</a>
+ <li><a href="#compile">Compiling the LLVM Suite Source Code</a>
+ <li><a href="#objfiles">The Location of LLVM Object Files</a>
+ </ol></li>
+
+ <li><a href="#layout">Program layout</a>
+ <ol>
+ <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
+ <li><a href="#include"><tt>llvm/include</tt></a>
+ <li><a href="#lib"><tt>llvm/lib</tt></a>
+ <li><a href="#runtime"><tt>llvm/runtime</tt></a>
+ <li><a href="#test"><tt>llvm/test</tt></a>
+ <li><a href="#tools"><tt>llvm/tools</tt></a>
+ <li><a href="#utils"><tt>llvm/utils</tt></a>
+ </ol></li>
+
+ <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
+ <li><a href="#problems">Common Problems</a>
+ <li><a href="#links">Links</a>
+ </ul>
+
+ <p>By:
+ <a href="mailto:gshi1 at uiuc.edu">Guochun Shi</a>,
+ <a href="mailto:sabre at nondot.org">Chris Lattner</a>,
+ <a href="mailto:criswell at uiuc.edu">John Criswell</a>,
+ <a href="http://misha.brukman.net">Misha Brukman</a>, and
+ <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>.</p>
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="overview"><b>Overview</b></a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Welcome to LLVM! In order to get started, you first need to know some
+ basic information.</p>
+
+ <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
+ contains all of the tools, libraries, and header files needed to use the low
+ level virtual machine. It contains an assembler, disassembler, bytecode
+ analyzer, and bytecode optimizer. It also contains a test suite that can be
+ used to test the LLVM tools and the GCC front end.</p>
+
+ <p>The second piece is the GCC front end. This component provides a version of
+ GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
+ end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
+ compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
+ from the LLVM suite.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Here's the short story for getting up and running quickly with LLVM:</p>
+
+ <ol>
+ <li>Install the GCC front end:
+ <ol>
+ <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
+ <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
+ <li><b>Sparc and MacOS X Only:</b><br>
+ <tt>cd cfrontend/<i>platform</i><br>
+ ./fixheaders</tt>
+ </ol></li>
+
+ <li>Get the Source Code
+ <ul>
+ <li>With the distributed files:
+ <ol>
+ <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
+ <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
+ <li><tt>cd llvm</tt>
+ </ol></li>
+
+ <li>With anonymous CVS access:
+ <ol>
+ <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
+ <li><tt>cvs -d
+ :pserver:anon at llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt></li>
+ <li>Hit the return key when prompted for the password.
+ <li><tt>cvs -z3 -d :pserver:anon at llvm-cvs.cs.uiuc.edu:/var/cvs/llvm
+ co llvm</tt></li>
+ <li><tt>cd llvm</tt></li>
+ </ol></li>
+ </ul></li>
+
+ <li>Configure the LLVM Build Environment
+ <ol>
+ <li>Change directory to where you want to store the LLVM object
+ files and run <tt>configure</tt> to configure the Makefiles and
+ header files for the default platform. Useful options include:
+ <ul>
+ <li><tt>--with-llvmgccdir=<i>directory</i></tt>
+ <p>Specify the full pathname of where the LLVM GCC frontend is
+ installed.</p></li>
+ <li><tt>--enable-spec2000=<i>directory</i></tt>
+ <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
+ benchmarks should be available in
+ <tt><i>directory</i></tt>.</p></li>
+ </ul>
+ </ol></li>
+
+ <li>Build the LLVM Suite:
+ <ol>
+ <li>Set your LLVM_LIB_SEARCH_PATH environment variable.
+ <li><tt>gmake -k |& tee gnumake.out
+ # this is csh or tcsh syntax</tt>
+ </ol>
+
+ </ol>
+
+ <p>Consult the <a href="starting">Getting Started with LLVM</a> section for
+ detailed information on configuring and compiling LLVM. See <a
+ href="#environment">Setting Up Your Environment</a> for tips that simplify
+ working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
+ Layout</a> to learn about the layout of the source code tree.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="requirements"><b>Requirements</b></a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Before you begin to use the LLVM system, review the requirements given below.
+ This may save you some trouble by knowing ahead of time what hardware and
+ software you will need.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="hardware"><b>Hardware</b></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>LLVM is known to work on the following platforms:</p>
+
+ <ul>
+
+ <li>Linux on x86 (Pentium and above)
+ <ul>
+ <li>Approximately 918 MB of Free Disk Space
+ <ul>
+ <li>Source code: 28 MB</li>
+ <li>Object code: 850 MB</li>
+ <li>GCC front end: 40 MB</li>
+ </ul></li>
+ </ul>
+ </li>
+
+ <li>Solaris on SparcV9 (Ultrasparc)
+ <ul>
+ <li>Approximately 1.52 GB of Free Disk Space
+ <ul>
+ <li>Source code: 28 MB</li>
+ <li>Object code: 1470 MB</li>
+ <li>GCC front end: 50 MB</li>
+ </ul></li>
+ </ul>
+ </li>
+
+ <li>FreeBSD on x86 (Pentium and above)
+ <ul>
+ <li>Approximately 918 MB of Free Disk Space
+ <ul>
+ <li>Source code: 28 MB</li>
+ <li>Object code: 850 MB</li>
+ <li>GCC front end: 40 MB</li>
+ </ul></li>
+ </ul>
+ </li>
+
+ <li>MacOS X on PowerPC
+ <ul>
+ <li>No native code generation
+ <li>Approximately 1.20 GB of Free Disk Space
+ <ul>
+ <li>Source code: 28 MB</li>
+ <li>Object code: 1160 MB</li>
+ <li>GCC front end: 40 MB</li>
+ </ul></li>
+ </ul>
+
+ </li>
+ </ul>
+
+ <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
+ guaranteed to do so. If compilation is successful, the LLVM utilities should be
+ able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
+ generation should work as well, although the generated native code may not work
+ on your platform.</p>
+
+ <p>The GCC front end is not very portable at the moment. If you want to get it
+ to work on another platform, you can download a copy of the source and try to
+ compile it on your platform.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="software"><b>Software</b></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Compiling LLVM requires that you have several software packages
+ installed:</p>
+
+ <ul>
+ <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
+ support</a></li>
+
+ <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
+
+ <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
+
+ <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
+ </ul>
+
+ <p>There are some additional tools that you may want to have when working with
+ LLVM:</p>
+
+ <ul>
+ <li><A href="http://www.gnu.org/software/automake">GNU Automake</A></li>
+ <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A></li>
+ <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
+
+ <p>If you want to make changes to the configure scripts, you will need GNU
+ autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
+ higher). You will also need automake. Any old version of
+ automake from 1.4p5 on should work; we only use aclocal from that
+ package.</p></li>
+
+ <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest 2.0.3</A></li>
+ <li><A href="http://www.python.org">Python</A>
+
+ <p>
+ These are needed to use the LLVM test suite. Please note that newer
+ versions of QMTest may not work with the LLVM test suite. QMTest 2.0.3
+ can be retrieved from the QMTest CVS repository using the following
+ commands:
+ <ul>
+ <li><tt>cvs -d :pserver:anoncvs at cvs.codesourcery.com:/home/qm/Repository login</tt>
+ </li>
+ <li>When prompted, use <tt>anoncvs</tt> as the password.
+ </li>
+ <li><tt>cvs -d :pserver:anoncvs at cvs.codesourcery.com:/home/qm/Repository co -r release-2-0-3 qm</tt>
+ </li>
+ </ul>
+ </p></li>
+
+ </ul>
+
+ <p>The remainder of this guide is meant to get you up and running with
+ LLVM and to give you some basic information about the LLVM environment.
+ A <a href="#starting">complete guide to installation</a> is provided in the
+ next section.</p>
+
+ <p>The later sections of this guide describe the <a
+ href="#layout">general layout</a> of the the LLVM source tree, a <a
+ href="#tutorial">simple example</a> using the LLVM tool chain, and <a
+ href="#links">links</a> to find more information about LLVM or to get
+ help via e-mail.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="starting"><b>Getting Started with LLVM</b></a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="terminology">Terminology and Notation</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Throughout this manual, the following names are used to denote paths
+ specific to the local system and working environment. <i>These are not
+ environment variables you need to set but just strings used in the rest
+ of this document below</i>. In any of the examples below, simply replace
+ each of these names with the appropriate pathname on your local system.
+ All these paths are absolute:</p>
+
+ <dl>
+ <dt>SRC_ROOT
+ <dd>
+ This is the top level directory of the LLVM source tree.
+ <p>
+
+ <dt>OBJ_ROOT
+ <dd>
+ This is the top level directory of the LLVM object tree (i.e. the
+ tree where object files and compiled programs will be placed. It
+ can be the same as SRC_ROOT).
+ <p>
+
+ <dt>LLVMGCCDIR
+ <dd>
+ This is the where the LLVM GCC Front End is installed.
+ <p>
+ For the pre-built GCC front end binaries, the LLVMGCCDIR is
+ <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
+ </dl>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="environment">Setting Up Your Environment</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ In order to compile and use LLVM, you will need to set some environment
+ variables. There are also some shell aliases which you may find useful.
+ You can set these on the command line, or better yet, set them in your
+ <tt>.cshrc</tt> or <tt>.profile</tt>.
+
+ <dl>
+ <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
+ <dd>
+ This environment variable helps the LLVM GCC front end find bytecode
+ libraries that it will need for compilation.
+ <p>
+
+ <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
+ <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
+ <dd>
+ This alias allows you to use the LLVM C and C++ front ends without putting
+ them in your <tt>PATH</tt> or typing in their complete pathnames.
+ </dl>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="unpack">Unpacking the LLVM Archives</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ If you have the LLVM distribution, you will need to unpack it before you
+ can begin to compile it. LLVM is distributed as a set of two files: the LLVM
+ suite and the LLVM GCC front end compiled for your platform. Each
+ file is a TAR archive that is compressed with the gzip program.
+ </p>
+
+ <p> The files are as follows:
+ <dl>
+ <dt>llvm-1.2.tar.gz
+ <dd>This is the source code to the LLVM suite.
+ <p>
+
+ <dt>cfrontend-1.2.sparc-sun-solaris2.8.tar.gz
+ <dd>This is the binary release of the GCC front end for Solaris/Sparc.
+ <p>
+
+ <dt>cfrontend-1.2.i686-redhat-linux-gnu.tar.gz
+ <dd>This is the binary release of the GCC front end for Linux/x86.
+ <p>
+
+ <dt>cfrontend-1.2.i386-unknown-freebsd5.1.tar.gz
+ <dd>This is the binary release of the GCC front end for FreeBSD/x86.
+ <p>
+
+ <dt>cfrontend-1.2.powerpc-apple-darwin7.0.0.tar.gz
+ <dd>This is the binary release of the GCC front end for MacOS X/PPC.
+ </dl>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="checkout">Checkout LLVM from CVS</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>If you have access to our CVS repository, you can get a fresh copy of
+ the entire source code. All you need to do is check it out from CVS as
+ follows:</p>
+
+ <ul>
+ <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
+ <li><tt>cvs -d :pserver:anon at llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
+ <li>Hit the return key when prompted for the password.
+ <li><tt>cvs -z3 -d :pserver:anon at llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
+ llvm</tt>
+ </ul>
+
+ <p>This will create an '<tt>llvm</tt>' directory in the current
+ directory and fully populate it with the LLVM source code, Makefiles,
+ test directories, and local copies of documentation files.</p>
+
+ <p>If you want to get a specific release (as opposed to the most recent
+ revision), you can specify a label. The following releases have the following
+ label:</p>
+
+ <ul>
+ <li>
+ Release 1.2: <b>RELEASE_12</b>
+ </li>
+
+ <li>
+ Release 1.1: <b>RELEASE_11</b>
+ </li>
+
+ <li>
+ Release 1.0: <b>RELEASE_1</b>
+ </li>
+ </ul>
+
+ <p>
+ If you would like to get the GCC front end source code, you can also get it
+ from the CVS repository:
+ <ul>
+ <li><tt>cvs -z3 -d :pserver:anon at llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
+ llvm-gcc</tt>
+ </ul>
+ </p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="installcf">Install the GCC Front End</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
+ GCC front end from the binary distribution. It is used for building the
+ bytecode libraries later used by the GCC front end for linking programs, and its
+ location must be specified when the LLVM suite is configured.</p>
+
+ <p>To install the GCC front end, do the following:</p>
+
+ <ol>
+ <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
+ <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
+ -</tt></li>
+ </ol>
+
+ <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
+ header files:</p>
+
+ <p><tt>cd cfrontend/<i>platform</i><br>
+ ./fixheaders</tt></p>
+
+ <p>The binary versions of the GCC front end may not suit all of your needs. For
+ example, the binary distribution may include an old version of a system header
+ file, not "fix" a header file that needs to be fixed for GCC, or it may be
+ linked with libraries not available on your system.</p>
+
+ <p>In cases like these, you may want to try <a
+ href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
+ not for the faint of heart, so be forewarned.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="config">Local LLVM Configuration</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Once checked out from the CVS repository, the LLVM suite source code must be
+ configured via the <tt>configure</tt> script. This script sets variables in
+ <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
+ also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
+ LLVM.</p>
+
+ <p>The following environment variables are used by the <tt>configure</tt>
+ script to configure the build system:</p>
+
+ <table border=1>
+ <tr>
+ <th>Variable</th>
+ <th>Purpose</th>
+ </tr>
+
+ <tr>
+ <td>CC</td>
+ <td>Tells <tt>configure</tt> which C compiler to use. By default,
+ <tt>configure</tt> will look for the first GCC C compiler in
+ <tt>PATH</tt>. Use this variable to override
+ <tt>configure</tt>'s default behavior.</td>
+ </tr>
+
+ <tr>
+ <td>CXX</td>
+ <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
+ <tt>configure</tt> will look for the first GCC C++ compiler in
+ <tt>PATH</tt>. Use this variable to override
+ <tt>configure</tt>'s default behavior.</td>
+ </tr>
+ </table>
+
+ <p>The following options can be used to set or enable LLVM specific options:</p>
+
+ <dl>
+ <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
+ <dd>
+ Path to the location where the LLVM GCC front end binaries and
+ associated libraries were installed. This must be specified as an
+ absolute pathname.
+ <p>
+ <dt><i>--enable-optimized</i>
+ <dd>
+ Enables optimized compilation by default (debugging symbols are removed
+ and GCC optimization flags are enabled). The default is to use an
+ unoptimized build (also known as a debug build).
+ <p>
+ <dt><i>--enable-jit</i>
+ <dd>
+ Compile the Just In Time (JIT) compiler functionality. This is not
+ available
+ on all platforms. The default is dependent on platform, so it is best
+ to explicitly enable it if you want it.
+ <p>
+ <dt><i>--enable-spec2000</i>
+ <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
+ <dd>
+ Enable the use of SPEC2000 when testing LLVM. This is disabled by default
+ (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
+ <tt>directory</tt>, you can tell configure where to find the SPEC2000
+ benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
+ uses the default value
+ <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
+ <p>
+ <dt><i>--enable-spec95</i>
+ <dt><i>--enable-spec95=<<tt>directory</tt>></i>
+ <dd>
+ Enable the use of SPEC95 when testing LLVM. It is similar to the
+ <i>--enable-spec2000</i> option.
+ <p>
+ <dt><i>--enable-povray</i>
+ <dt><i>--enable-povray=<<tt>directory</tt>></i>
+ <dd>
+ Enable the use of Povray as an external test. Versions of Povray written
+ in C should work. This option is similar to the <i>--enable-spec2000</i>
+ option.
+ </dl>
+
+ <p>To configure LLVM, follow these steps:</p>
+
+ <ol>
+ <li>Change directory into the object root directory:
+ <br>
+ <tt>cd <i>OBJ_ROOT</i></tt>
+ <p>
+
+ <li>Run the <tt>configure</tt> script located in the LLVM source tree:
+ <br>
+ <tt><i>SRC_ROOT</i>/configure</tt>
+ <p>
+ </ol>
+
+ <p>In addition to running <tt>configure</tt>, you must set the
+ <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
+ This environment variable is used to locate "system" libraries like
+ "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
+ the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
+ end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
+ <tt>LLVM_LIB_SEARCH_PATH</tt> to
+ <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
+ version of the GCC front end on our research machines.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="compile">Compiling the LLVM Suite Source Code</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Once you have configured LLVM, you can build it. There are three types of
+ builds:</p>
+
+ <dl>
+ <dt>Debug Builds
+ <dd>
+ These builds are the default when one types <tt>gmake</tt> (unless the
+ <tt>--enable-optimized</tt> option was used during configuration). The
+ build system will compile the tools and libraries with debugging
+ information.
+ <p>
+
+ <dt>Release (Optimized) Builds
+ <dd>
+ These builds are enabled with the <tt>--enable-optimized</tt> option to
+ <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
+ <tt>gmake</tt> command line. For these builds, the build system will
+ compile the tools and libraries with GCC optimizations enabled and strip
+ debugging information from the libraries and executables it generates.
+ <p>
+
+ <dt>Profile Builds
+ <dd>
+ These builds are for use with profiling. They compile profiling
+ information into the code for use with programs like <tt>gprof</tt>.
+ Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
+ on the <tt>gmake</tt> command line.
+ </dl>
+
+ <p>Once you have LLVM configured, you can build it by entering the
+ <i>OBJ_ROOT</i> directory and issuing the following command:</p>
+
+ <p><tt>gmake</tt></p>
+
+ <p>If you have multiple processors in your machine, you may wish to use some of
+ the parallel build options provided by GNU Make. For example, you could use the
+ command:</p>
+
+ <p><tt>gmake -j2</tt></p>
+
+ <p>There are several special targets which are useful when working with the LLVM
+ source code:</p>
+
+ <dl>
+ <dt><tt>gmake clean</tt>
+ <dd>
+ Removes all files generated by the build. This includes object files,
+ generated C/C++ files, libraries, and executables.
+ <p>
+
+ <dt><tt>gmake distclean</tt>
+ <dd>
+ Removes everything that <tt>gmake clean</tt> does, but also removes
+ files generated by <tt>configure</tt>. It attempts to return the
+ source tree to the original state in which it was shipped.
+ <p>
+
+ <dt><tt>gmake install</tt>
+ <dd>
+ Installs LLVM files into the proper location. For the most part,
+ this does nothing, but it does install bytecode libraries into the
+ GCC front end's bytecode library directory. If you need to update
+ your bytecode libraries, this is the target to use once you've built
+ them.
+ <p>
+ </dl>
+
+ <p>It is also possible to override default values from <tt>configure</tt> by
+ declaring variables on the command line. The following are some examples:</p>
+
+ <dl>
+ <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
+ <dd>
+ Perform a Release (Optimized) build.
+ <p>
+
+ <dt><tt>gmake ENABLE_PROFILING=1</tt>
+ <dd>
+ Perform a Profiling build.
+ <p>
+
+ <dt><tt>gmake VERBOSE=1</tt>
+ <dd>
+ Print what <tt>gmake</tt> is doing on standard output.
+ <p>
+ </dl>
+
+ <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
+ it and any subdirectories that it contains. Entering any directory inside the
+ LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
+ that directory that is out of date.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="objfiles">The Location of LLVM Object Files</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The LLVM build system is capable of sharing a single LLVM source tree among
+ several LLVM builds. Hence, it is possible to build LLVM for several different
+ platforms or configurations using the same source tree.</p>
+
+ <p>This is accomplished in the typical autoconf manner:</p>
+
+ <ul>
+ <li><p>Change directory to where the LLVM object files should live:</p>
+
+ <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
+
+ <li><p>Run the <tt>configure</tt> script found in the LLVM source
+ directory:</p>
+
+ <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
+ </ul>
+
+ <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
+ named after the build type:</p>
+
+ <dl>
+ <dt>Debug Builds
+ <dd>
+ <dl>
+ <dt>Tools
+ <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
+ <dt>Libraries
+ <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
+ </dl>
+ <p>
+
+ <dt>Release Builds
+ <dd>
+ <dl>
+ <dt>Tools
+ <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
+ <dt>Libraries
+ <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
+ </dl>
+ <p>
+
+ <dt>Profile Builds
+ <dd>
+ <dl>
+ <dt>Tools
+ <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
+ <dt>Libraries
+ <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
+ </dl>
+ </dl>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="layout"><b>Program Layout</b></a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>One useful source of information about the LLVM source base is the LLVM <a
+ href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
+ The following is a brief introduction to code layout:</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="cvsdir"><tt>CVS</tt> directories</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
+ the most part these can just be ignored.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="include"><tt>llvm/include</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>This directory contains public header files exported from the LLVM
+ library. The three main subdirectories of this directory are:</p>
+
+ <ol>
+ <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
+ specific header files. This directory also has subdirectories for
+ different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
+ <tt>Target</tt>, <tt>Transforms</tt>, etc...</li>
+
+ <li><tt>llvm/include/Support</tt> - This directory contains generic
+ support libraries that are independent of LLVM, but are used by LLVM.
+ For example, some C++ STL utilities and a Command Line option processing
+ library store their header files here.</li>
+
+ <li><tt>llvm/include/Config</tt> - This directory contains header files
+ configured by the <tt>configure</tt> script. They wrap "standard" UNIX
+ and C header files. Source code can include these header files which
+ automatically take care of the conditional #includes that the
+ <tt>configure</tt> script generates.</li>
+ </ol>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="lib"><tt>llvm/lib</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>This directory contains most of the source files of the LLVM system. In LLVM,
+ almost all code exists in libraries, making it very easy to share code among the
+ different <a href="#tools">tools</a>.</p>
+
+ <dl>
+ <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
+ source files that implement core classes like Instruction and BasicBlock.
+
+ <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
+ for the LLVM assembly language parser library.
+
+ <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
+ and write LLVM bytecode.
+
+ <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
+ converter.
+
+ <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
+ different program analyses, such as Dominator Information, Call Graphs,
+ Induction Variables, Interval Identification, Natural Loop Identification,
+ etc...
+
+ <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
+ code for the LLVM to LLVM program transformations, such as Aggressive Dead
+ Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
+ Invariant Code Motion, Dead Global Elimination, and many others...
+
+ <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
+ describe various target architectures for code generation. For example,
+ the llvm/lib/Target/Sparc directory holds the Sparc machine
+ description.<br>
+
+ <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
+ of the code generator: Instruction Selector, Instruction Scheduling, and
+ Register Allocation.
+
+ <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
+ that corresponds to the header files located in
+ <tt>llvm/include/Support/</tt>.
+ </dl>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="runtime"><tt>llvm/runtime</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>This directory contains libraries which are compiled into LLVM bytecode and
+ used when linking programs with the GCC front end. Most of these libraries are
+ skeleton versions of real libraries; for example, libc is a stripped down
+ version of glibc.</p>
+
+ <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
+ end to compile.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="test"><tt>llvm/test</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>This directory contains regression tests and source code that is used to test
+ the LLVM infrastructure.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="tools"><tt>llvm/tools</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <b>tools</b> directory contains the executables built out of the
+ libraries above, which form the main part of the user interface. You can
+ always get help for a tool by typing <tt>tool_name --help</tt>. The
+ following is a brief introduction to the most important tools:</p>
+
+ <dl>
+ <dt><tt><b>analyze</b></tt> <dd><tt>analyze</tt> is used to run a specific
+ analysis on an input LLVM bytecode file and print out the results. It is
+ primarily useful for debugging analyses, or familiarizing yourself with
+ what an analysis does.<p>
+
+ <dt><tt><b>bugpoint</b></tt> <dd><tt>bugpoint</tt> is used to debug
+ optimization passes or code generation backends by narrowing down the
+ given test case to the minimum number of passes and/or instructions that
+ still cause a problem, whether it is a crash or miscompilation. See <a
+ href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
+ on using <tt>bugpoint</tt>.<p>
+
+ <dt><tt><b>llvm-ar</b></tt> <dd>The archiver produces an archive containing
+ the given LLVM bytecode files, optionally with an index for faster
+ lookup.<p>
+
+ <dt><tt><b>llvm-as</b></tt> <dd>The assembler transforms the human readable
+ LLVM assembly to LLVM bytecode.<p>
+
+ <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
+ bytecode to human readable LLVM assembly.<p>
+
+ <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
+ links multiple LLVM modules into a single program.<p>
+
+ <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
+ can directly execute LLVM bytecode (although very slowly...). In addition
+ to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
+ specifying <tt>-trace</tt> on the command line). Finally, for
+ architectures that support it (currently only x86 and Sparc), by default,
+ <tt>lli</tt> will function as a Just-In-Time compiler (if the
+ functionality was compiled in), and will execute the code <i>much</i>
+ faster than the interpreter.<p>
+
+ <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler, which
+ translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
+ the -march=c option).<p>
+
+ <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
+ that has been retargeted to emit LLVM code as the machine code output. It
+ works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
+ -o</tt> options that are typically used. The source code for the
+ <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
+ because it is quite large and not very interesting.<p>
+
+ <blockquote>
+ <dl>
+ <dt><tt><b>gccas</b></tt> <dd>This tool is invoked by the
+ <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
+ tool actually assembles LLVM assembly to LLVM bytecode,
+ performs a variety of optimizations, and outputs LLVM bytecode. Thus
+ when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
+ <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
+ an LLVM bytecode file that can be disassembled or manipulated just like
+ any other bytecode file). The command line interface to <tt>gccas</tt>
+ is designed to be as close as possible to the <b>system</b>
+ `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
+ modified to interface to a "weird" assembler.<p>
+
+ <dt><tt><b>gccld</b></tt> <dd><tt>gccld</tt> links together several LLVM
+ bytecode files into one bytecode file and does some optimization. It is
+ the linker invoked by the GCC frontend when multiple .o files need to be
+ linked together. Like <tt>gccas</tt>, the command line interface of
+ <tt>gccld</tt> is designed to match the system linker, to aid
+ interfacing with the GCC frontend.</dl><p>
+ </blockquote>
+
+ <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
+ series of LLVM to LLVM transformations (which are specified on the command
+ line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
+ command is a good way to get a list of the program transformations
+ available in LLVM.
+
+ </dl>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="utils"><tt>llvm/utils</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>This directory contains utilities for working with LLVM source code, and some
+ of the utilities are actually required as part of the build process because they
+ are code generators for parts of LLVM infrastructure.</p>
+
+ <dl>
+ <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
+ generator -- it builds trees on which it then performs pattern-matching to
+ select instructions according to the patterns the user has specified. Burg
+ is currently used in the Sparc V9 backend.<p>
+
+ <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
+ that finds differences between code that LLC generates and code that LLI
+ generates. This is a useful tool if you are debugging one of them,
+ assuming that the other generates correct output. For the full user
+ manual, run <tt>`perldoc codegen-diff'</tt>.<p>
+
+ <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
+ update your CVS tree, but produce a much cleaner and more organized output
+ than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
+ together all the new and updated files and modified files in separate
+ sections, so you can see at a glance what has changed. If you are at the
+ top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
+ preferred way of updating the tree.<p>
+
+ <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
+ syntax-highlighting files which will work with Emacs and XEmacs editors,
+ providing syntax highlighting support for LLVM assembly files and TableGen
+ description files. For information on how to use the syntax files, consult
+ the <tt>README</tt> file in that directory.<p>
+
+ <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
+ and outputs all non-generated source files, which is useful if one wishes
+ to do a lot of development across directories and does not want to
+ individually find each file. One way to use it is to run, for example:
+ <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
+ tree.<p>
+
+ <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
+ files in the current directory and then compiles and links the tool that
+ is the first argument. For example, assuming you are in the directory
+ <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
+ simply running <tt>makellvm llc</tt> will make a build of the current
+ directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
+ causing a re-linking of LLC.<p>
+
+ <dt><tt><b>NightlyTest.pl</b></tt> and
+ <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
+ cron script to generate nightly status reports of the functionality of
+ tools, and the results can be seen by following the appropriate link on
+ the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
+
+ <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
+ the tool used to generate register descriptions, instruction set
+ descriptions, and even assemblers from common TableGen description
+ files.<p>
+
+ <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
+ syntax-highlighting files which will work with the VIM editor, providing
+ syntax highlighting support for LLVM assembly files and TableGen
+ description files. For information on how to use the syntax files, consult
+ the <tt>README</tt> file in that directory.<p>
+
+ </dl>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="tutorial">An Example Using the LLVM Tool Chain</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <ol>
+ <li>First, create a simple C file, name it 'hello.c':
+ <pre>
+ #include <stdio.h>
+ int main() {
+ printf("hello world\n");
+ return 0;
+ }
+ </pre></li>
+
+ <li><p>Next, compile the C file into a LLVM bytecode file:</p>
+ <p><tt>% llvmgcc hello.c -o hello</tt></p>
+
+ <p>This will create two result files: <tt>hello</tt> and
+ <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
+ corresponds the the compiled program and the library facilities that it
+ required. <tt>hello</tt> is a simple shell script that runs the bytecode
+ file with <tt>lli</tt>, making the result directly executable.</p></li>
+
+ <li><p>Run the program. To make sure the program ran, execute one of the
+ following commands:</p>
+
+ <p><tt>% ./hello</tt></p>
+
+ <p>or</p>
+
+ <p><tt>% lli hello.bc</tt></p></li>
+
+ <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
+ code:</p>
+
+ <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
+
+ <li><p>Compile the program to native Sparc assembly using the code
+ generator (assuming you are currently on a Sparc system):</p>
+
+ <p><tt>% llc hello.bc -o hello.s</tt></p>
+
+ <li><p>Assemble the native sparc assemble file into a program:</p>
+
+ <p><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt></p>
+
+ <li><p>Execute the native sparc program:</p>
+
+ <p><tt>% ./hello.sparc</tt></p></li>
+
+ </ol>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="problems">Common Problems</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>If you are having problems building or using LLVM, or if you have any other
+ general questions about LLVM, please consult the <a href="FAQ.html">Frequently
+ Asked Questions</a> page.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="links">Links</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This document is just an <b>introduction</b> to how to use LLVM to do
+ some simple things... there are many more interesting and complicated things
+ that you can do that aren't documented here (but we'll gladly accept a patch
+ if you want to write something up!). For more information about LLVM, check
+ out:</p>
+
+ <ul>
+ <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
+ that Uses LLVM</a></li>
+ </ul>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+
+ <hr>
+ <address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
+
+ <a href="mailto:sabre at nondot.org">Chris Lattner</a><br>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </address>
+
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/HowToSubmitABug.html
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>How to submit an LLVM bug report</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">
+ How to submit an LLVM bug report
+ </div>
+
+ <table border="0" width="100%">
+ <tr>
+ <td valign="top">
+
+ <ol>
+ <li><a href="#introduction">Introduction - Got bugs?</a></li>
+ <li><a href="#crashers">Crashing Bugs</a>
+ <ul>
+ <li><a href="#front-end">Front-end bugs</a>
+ <li><a href="#gccas">GCCAS bugs</a>
+ <li><a href="#gccld">GCCLD bugs</a>
+ <li><a href="#passes">Bugs in LLVM passes</a>
+ </ul></li>
+ <li><a href="#miscompilations">Miscompilations</a></li>
+ <li><a href="#codegen">Incorrect code generation (JIT and LLC)</a></li>
+
+ </ol>
+
+ <div class="doc_text">
+ <p><b>Written by <a href="mailto:sabre at nondot.org">Chris Lattner</a> and
+ <a href="http://misha.brukman.net">Misha Brukman</a></b></p>
+ </div>
+
+ </td>
+ <td align="right">
+ <img src="Debugging.gif" alt="Debugging" width="444" height="314">
+ </td>
+ </tr>
+ </table>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="introduction">Introduction - Got bugs?</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>If you're working with LLVM and run into a bug, we definitely want to know
+ about it. This document describes what you can do to increase the odds of
+ getting it fixed quickly.</p>
+
+ <p>Basically you have to do two things at a minimum. First, decide whether the
+ bug <a href="#crashers">crashes the compiler</a> (or an LLVM pass), or if the
+ compiler is <a href="#miscompilations">miscompiling</a> the program. Based on
+ what type of bug it is, follow the instructions in the linked section to narrow
+ down the bug so that the person who fixes it will be able to find the problem
+ more easily.</p>
+
+ <p>Once you have a reduced test-case, go to <a
+ href="http://llvm.cs.uiuc.edu/bugs/enter_bug.cgi">the LLVM Bug Tracking
+ System</a>, select the category in which the bug falls, and fill out the form
+ with the necessary details. The bug description should contain the following
+ information:</p>
+
+ <ul>
+ <li>All information necessary to reproduce the problem.</li>
+ <li>The reduced test-case that triggers the bug.</li>
+ <li>The location where you obtained LLVM (if not from our CVS
+ repository).</li>
+ </ul>
+
+ <p>Thanks for helping us make LLVM better!</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="crashers">Crashing Bugs</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>More often than not, bugs in the compiler cause it to crash - often due to an
+ assertion failure of some sort. If you are running <tt><b>opt</b></tt> or
+ <tt><b>analyze</b></tt> directly, and something crashes, jump to the section on
+ <a href="#passes">bugs in LLVM passes</a>. Otherwise, the most important
+ piece of the puzzle is to figure out if it is the GCC-based front-end that is
+ buggy or if it's one of the LLVM tools that has problems.</p>
+
+ <p>To figure out which program is crashing (the front-end,
+ <tt><b>gccas</b></tt>, or <tt><b>gccld</b></tt>), run the
+ <tt><b>llvm-gcc</b></tt> command line as you were when the crash occurred, but
+ add a <tt>-v</tt> option to the command line. The compiler will print out a
+ bunch of stuff, and should end with telling you that one of
+ <tt><b>cc1</b>/<b>cc1plus</b></tt>, <tt><b>gccas</b></tt>, or
+ <tt><b>gccld</b></tt> crashed.</p>
+
+ <ul>
+
+ <li>If <tt><b>cc1</b></tt> or <tt><b>cc1plus</b></tt> crashed, you found a
+ problem with the front-end.
+ Jump ahead to the section on <a href="#front-end">front-end bugs</a>.</li>
+
+ <li>If <tt><b>gccas</b></tt> crashed, you found a bug in <a href="#gccas">one
+ of the passes in <tt><b>gccas</b></tt></a>.</li>
+
+ <li>If <tt><b>gccld</b></tt> crashed, you found a bug in <a href="#gccld">one
+ of the passes in <tt><b>gccld</b></tt></a>.</li>
+
+ <li>Otherwise, something really weird happened. Email the list with what you
+ have at this point.</li>
+
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="front-end">Front-end bugs</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>If the problem is in the front-end, you should re-run the same
+ <tt>llvm-gcc</tt> command that resulted in the crash, but add the
+ <tt>-save-temps</tt> option. The compiler will crash again, but it will leave
+ behind a <tt><i>foo</i>.i</tt> file (containing preprocessed C source code) and
+ possibly <tt><i>foo</i>.s</tt> (containing LLVM assembly code), for each
+ compiled <tt><i>foo</i>.c</tt> file. Send us the <tt><i>foo</i>.i</tt> file,
+ along with a brief description of the error it caused.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="gccas">GCCAS bugs</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>If you find that a bug crashes in the <tt><b>gccas</b></tt> stage of
+ compilation, compile your test-case to a <tt>.s</tt> file with the
+ <tt>-save-temps</tt> option to <tt><b>llvm-gcc</b></tt>. Then run:</p>
+
+ <pre>
+ <b>gccas</b> -debug-pass=Arguments < /dev/null -o - > /dev/null
+ </pre>
+
+ <p>... which will print a list of arguments, indicating the list of passes that
+ <tt><b>gccas</b></tt> runs. Once you have the input file and the list of
+ passes, go to the section on <a href="#passes">debugging bugs in LLVM
+ passes</a>.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="gccld">GCCLD bugs</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>If you find that a bug crashes in the <tt><b>gccld</b></tt> stage of
+ compilation, gather all of the <tt>.o</tt> bytecode files and libraries that are
+ being linked together (the "<tt><b>llvm-gcc</b> -v</tt>" output should include
+ the full list of objects linked). Then run:</p>
+
+ <pre>
+ <b>llvm-as</b> < /dev/null > null.bc
+ <b>gccld</b> -debug-pass=Arguments null.bc
+ </pre><p>
+
+ <p>... which will print a list of arguments, indicating the list of passes that
+ <tt><b>gccld</b></tt> runs. Once you have the input files and the list of
+ passes, go to the section on <a href="#passes">debugging bugs in LLVM
+ passes</a>.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="passes">Bugs in LLVM passes</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>At this point, you should have some number of LLVM assembly files or bytecode
+ files and a list of passes which crash when run on the specified input. In
+ order to reduce the list of passes (which is probably large) and the input to
+ something tractable, use the <tt><b>bugpoint</b></tt> tool as follows:</p>
+
+ <pre>
+ <b>bugpoint</b> <input files> <list of passes>
+ </pre><p>
+
+ <p><tt><b>bugpoint</b></tt> will print a bunch of output as it reduces the
+ test-case, but it should eventually print something like this:</p>
+
+ <pre>
+ ...
+ Emitted bytecode to 'bugpoint-reduced-simplified.bc'
+
+ *** You can reproduce the problem with: opt bugpoint-reduced-simplified.bc -licm
+ </pre>
+
+ <p>Once you complete this, please send the LLVM bytecode file and the command
+ line to reproduce the problem to the llvmbugs mailing list.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="miscompilations">Miscompilations</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>A miscompilation occurs when a pass does not correctly transform a program,
+ thus producing errors that are only noticed during execution. This is different
+ from producing invalid LLVM code (i.e., code not in SSA form, using values
+ before defining them, etc.) which the verifier will check for after a pass
+ finishes its run.</p>
+
+ <p>To debug a miscompilation, you should choose which program you wish to run
+ the output through, e.g. C backend, the JIT, or LLC, and a selection of passes,
+ one of which may be causing the error, and run, for example:</p>
+
+ <pre>
+ <b>bugpoint</b> -run-cbe [... optimization passes ...] file-to-test.bc
+ </pre>
+
+ <p><tt>bugpoint</tt> will try to narrow down your list of passes to the one pass
+ that causes an error, and simplify the bytecode file as much as it can to assist
+ you. It will print a message letting you know how to reproduce the resulting
+ error.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="codegen">Incorrect code generation</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Similarly to debugging incorrect compilation by mis-behaving passes, you can
+ debug incorrect code generation by either LLC or the JIT, using
+ <tt>bugpoint</tt>. The process <tt>bugpoint</tt> follows in this case is to try
+ to narrow the code down to a function that is miscompiled by one or the other
+ method, but since for correctness, the entire program must be run,
+ <tt>bugpoint</tt> will compile the code it deems to not be affected with the C
+ Backend, and then link in the shared object it generates.</p>
+
+ <p>To debug the JIT:</p>
+
+ <pre>
+ <b>bugpoint</b> -run-jit -output=[correct output file] [bytecodefile]
+ </pre>
+
+ <p>Similarly, to debug the LLC, one would run:</p>
+
+ <pre>
+ <b>bugpoint</b> -run-llc -output=[correct output file] [bytecodefile]
+ </pre>
+
+ <p>At the end of a successful <tt>bugpoint</tt> run, you will be presented
+ with two bytecode files: a <em>safe</em> file which can be compiled with the C
+ backend and the <em>test</em> file which either LLC or the JIT
+ mis-codegenerates, and thus causes the error.</p>
+
+ <p>To reproduce the error that <tt>bugpoint</tt> found, it is sufficient to do
+ the following:</p>
+
+ <ol>
+
+ <li>Regenerate the shared object from the safe bytecode file:<br>
+
+ <pre>
+ <b>llc</b> -march=c safe.bc -o safe.c<br>
+ <b>gcc</b> -shared safe.c -o safe.so
+ </pre></li>
+
+ <li>If debugging LLC, compile test bytecode native and link with the shared object:<br>
+
+ <pre>
+ <b>llc</b> test.bc -o test.s -f<br>
+ gcc test.s safe.so -o test.llc<br>
+ ./test.llc [program options]
+ </pre></li>
+
+ <li>If debugging the JIT, load the shared object and supply the test
+ bytecode:
+
+ <pre>
+ <b>lli</b> -load=safe.so test.bc [program options]
+ </pre></li>
+
+ </ol>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <hr>
+ <address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
+
+ <a href="mailto:sabre at nondot.org">Chris Lattner</a><br>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </address>
+
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/LLVMVsTheWorld.html
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*** 0 ****
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ <title>LLVM vs. the World - Comparing Compilers to Compilers</title>
+ </head>
+
+ <body>
+
+ <div class="doc_title">
+ LLVM vs. the World - Comparing Compilers to Compilers
+ </div>
+
+ <ol>
+ <li><a href="#introduction">Introduction</a></li>
+ <li><a href="#generalapplicability">General Applicability</a></li>
+ <li><a href="#typesystem">Type System</a></li>
+ <li><a href="#dataflowinformation">Control-flow and Data-flow Information</a></li>
+ <li><a href="#registers">Registers</a></li>
+ <li><a href="#programmerinterface">Programmer Interface</a></li>
+ <li><a href="#codeemission">Machine Code Emission</a></li>
+ </ol>
+
+ <div class="doc_text">
+ <p><b>Written by Brian R. Gaeke</b></p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="introduction">Introduction</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+ <p>Whether you are a stranger to LLVM or not, and whether you are considering
+ using it for your projects or not, you may find it useful to understand how we
+ compare ourselves to other well-known compilers. The following list of points
+ should help you understand -- from our point of view -- some of the important
+ ways in which we see LLVM as different from other selected compilers and
+ code generation systems.</p>
+
+ <p>At the moment, we only compare ourselves below to <a
+ href="http://gcc.gnu.org/">GCC</a> and <a
+ href="http://www.gnu.org/software/lightning/">GNU lightning</a>, but we will try
+ to revise and expand it as our knowledge and experience permit. Contributions are
+ welcome.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="generalapplicability">General Applicability</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+ <p>GNU lightning: Only currently usable for dynamic runtime emission of binary
+ machine code to memory. Supports one backend at a time.</p>
+
+ <p>LLVM: Supports compilation of C and C++ (with more languages coming soon),
+ strong SSA-based optimization at compile-time, link-time, run-time, and
+ off-line, and multiple platform backends with Just-in-Time and ahead-of-time
+ compilation frameworks. (See our document on <a
+ href="http://llvm.cs.uiuc.edu/pubs/2004-01-30-CGO-LLVM.html">Lifelong
+ Code Optimization</a> for more.)</p>
+
+ <p>GCC: Many relatively mature platform backends support assembly-language code
+ generation from many source languages. No run-time compilation
+ support.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="typesystem">Type System</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+ <p>GNU lightning: C integer types and "void *" are supported. No type checking
+ is performed. Explicit type casts are not typically necessary unless the
+ underlying machine-specific types are distinct (e.g., sign- or zero-extension is
+ apparently necessary, but casting "int" to "void *" would not be.)
+ Floating-point support may not work on all platforms (it does not appear to be
+ documented in the latest release).</p>
+
+ <p>LLVM: Compositional type system based on C types, supporting structures,
+ opaque types, and C integer and floating point types. Explicit cast instructions
+ are required to transform a value from one type to another.</p>
+
+ <p>GCC: Union of high-level types including those used in Pascal, C, C++, Ada,
+ Java, and FORTRAN.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="dataflowinformation">Control-flow and Data-flow Information</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+ <p>GNU lightning: No data-flow information encoded in the generated program. No
+ support for calculating CFG or def-use chains over generated programs.</p>
+
+ <p>LLVM: Scalar values in Static Single-Assignment form; def-use chains and CFG
+ always implicitly available and automatically kept up to date.</p>
+
+ <p>GCC: Trees and RTL do not directly encode data-flow info; but def-use chains
+ and CFGs can be calculated on the side. They are not automatically kept up to
+ date.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="registers">Registers</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+ <p>GNU lightning: Very small fixed register set -- it takes the least common
+ denominator of supported platforms; basically it inherits its tiny register set
+ from IA-32, unnecessarily crippling targets like PowerPC with a large register
+ set.</p>
+
+ <p>LLVM: An infinite register set, reduced to a particular platform's finite
+ register set by register allocator.</p>
+
+ <p>GCC: Trees and RTL provide an arbitrarily large set of values. Reduced to a
+ particular platform's finite register set by register allocator.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="programmerinterface">Programmer Interface</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+ <p>GNU lightning: Library interface based on C preprocessor macros that emit
+ binary code for a particular instruction to memory. No support for manipulating
+ code before emission.</p>
+
+ <p>LLVM: Library interface based on classes representing platform-independent
+ intermediate code (Instruction) and platform-dependent code (MachineInstr) which
+ can be manipulated arbitrarily and then emitted to memory.</p>
+
+ <p>GCC: Internal header file interface (tree.h) to abstract syntax trees,
+ representing roughly the union of all possible supported source-language
+ constructs; also, an internal header file interface (rtl.h, rtl.def) to a
+ low-level IR called RTL which represents roughly the union of all possible
+ target machine instructions.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="codeemission">Machine Code Emission</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+ <p>GNU lightning: Only supports binary machine code emission to memory.</p>
+
+ <p>LLVM: Supports writing out assembly language to a file, and binary machine
+ code to memory, from the same back-end.</p>
+
+ <p>GCC: Supports writing out assembly language to a file. No support for
+ emitting machine code to memory.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+
+ <hr>
+ <div class="doc_footer">
+ <address>Brian R. Gaeke</address>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </div>
+
+ </body>
+ </html>
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>LLVM Assembly Language Reference Manual</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+ <div class="doc_title"> LLVM Language Reference Manual </div>
+ <ol>
+ <li><a href="#abstract">Abstract</a></li>
+ <li><a href="#introduction">Introduction</a></li>
+ <li><a href="#identifiers">Identifiers</a></li>
+ <li><a href="#typesystem">Type System</a>
+ <ol>
+ <li><a href="#t_primitive">Primitive Types</a>
+ <ol>
+ <li><a href="#t_classifications">Type Classifications</a></li>
+ </ol>
+ </li>
+ <li><a href="#t_derived">Derived Types</a>
+ <ol>
+ <li><a href="#t_array">Array Type</a></li>
+ <li><a href="#t_function">Function Type</a></li>
+ <li><a href="#t_pointer">Pointer Type</a></li>
+ <li><a href="#t_struct">Structure Type</a></li>
+ <!-- <li><a href="#t_packed" >Packed Type</a> -->
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><a href="#highlevel">High Level Structure</a>
+ <ol>
+ <li><a href="#modulestructure">Module Structure</a></li>
+ <li><a href="#globalvars">Global Variables</a></li>
+ <li><a href="#functionstructure">Function Structure</a></li>
+ </ol>
+ </li>
+ <li><a href="#instref">Instruction Reference</a>
+ <ol>
+ <li><a href="#terminators">Terminator Instructions</a>
+ <ol>
+ <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li>
+ <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li>
+ <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li>
+ <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li>
+ <li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li>
+ </ol>
+ </li>
+ <li><a href="#binaryops">Binary Operations</a>
+ <ol>
+ <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li>
+ <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li>
+ <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li>
+ <li><a href="#i_div">'<tt>div</tt>' Instruction</a></li>
+ <li><a href="#i_rem">'<tt>rem</tt>' Instruction</a></li>
+ <li><a href="#i_setcc">'<tt>set<i>cc</i></tt>' Instructions</a></li>
+ </ol>
+ </li>
+ <li><a href="#bitwiseops">Bitwise Binary Operations</a>
+ <ol>
+ <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li>
+ <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li>
+ <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li>
+ <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li>
+ <li><a href="#i_shr">'<tt>shr</tt>' Instruction</a></li>
+ </ol>
+ </li>
+ <li><a href="#memoryops">Memory Access Operations</a>
+ <ol>
+ <li><a href="#i_malloc">'<tt>malloc</tt>' Instruction</a></li>
+ <li><a href="#i_free">'<tt>free</tt>' Instruction</a></li>
+ <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li>
+ <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li>
+ <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li>
+ <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li>
+ </ol>
+ </li>
+ <li><a href="#otherops">Other Operations</a>
+ <ol>
+ <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li>
+ <li><a href="#i_cast">'<tt>cast .. to</tt>' Instruction</a></li>
+ <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li>
+ <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li>
+ <li><a href="#i_vanext">'<tt>vanext</tt>' Instruction</a></li>
+ <li><a href="#i_vaarg">'<tt>vaarg</tt>' Instruction</a></li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><a href="#intrinsics">Intrinsic Functions</a>
+ <ol>
+ <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a>
+ <ol>
+ <li><a href="#i_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li>
+ <li><a href="#i_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li>
+ <li><a href="#i_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li>
+ </ol>
+ </li>
+ <li><a href="#int_codegen">Code Generator Intrinsics</a>
+ <ol>
+ <li><a href="#i_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li>
+ <li><a href="#i_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li>
+ </ol>
+ </li>
+ <li><a href="#int_libc">Standard C Library Intrinsics</a>
+ <ol>
+ <li><a href="#i_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a></li>
+ <li><a href="#i_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a></li>
+ <li><a href="#i_memset">'<tt>llvm.memset</tt>' Intrinsic</a></li>
+ </ol>
+ </li>
+ <li><a href="#int_debugger">Debugger intrinsics</a>
+ </ol>
+ </li>
+ </ol>
+ <div class="doc_text">
+ <p><b>Written by <a href="mailto:sabre at nondot.org">Chris Lattner</a>
+ and <a href="mailto:vadve at cs.uiuc.edu">Vikram Adve</a></b></p>
+ <p> </p>
+ </div>
+ <!-- *********************************************************************** -->
+ <div class="doc_section"> <a name="abstract">Abstract </a></div>
+ <!-- *********************************************************************** -->
+ <div class="doc_text">
+ <p>This document is a reference manual for the LLVM assembly language.
+ LLVM is an SSA based representation that provides type safety,
+ low-level operations, flexibility, and the capability of representing
+ 'all' high-level languages cleanly. It is the common code
+ representation used throughout all phases of the LLVM compilation
+ strategy.</p>
+ </div>
+ <!-- *********************************************************************** -->
+ <div class="doc_section"> <a name="introduction">Introduction</a> </div>
+ <!-- *********************************************************************** -->
+ <div class="doc_text">
+ <p>The LLVM code representation is designed to be used in three
+ different forms: as an in-memory compiler IR, as an on-disk bytecode
+ representation (suitable for fast loading by a Just-In-Time compiler),
+ and as a human readable assembly language representation. This allows
+ LLVM to provide a powerful intermediate representation for efficient
+ compiler transformations and analysis, while providing a natural means
+ to debug and visualize the transformations. The three different forms
+ of LLVM are all equivalent. This document describes the human readable
+ representation and notation.</p>
+ <p>The LLVM representation aims to be a light-weight and low-level
+ while being expressive, typed, and extensible at the same time. It
+ aims to be a "universal IR" of sorts, by being at a low enough level
+ that high-level ideas may be cleanly mapped to it (similar to how
+ microprocessors are "universal IR's", allowing many source languages to
+ be mapped to them). By providing type information, LLVM can be used as
+ the target of optimizations: for example, through pointer analysis, it
+ can be proven that a C automatic variable is never accessed outside of
+ the current function... allowing it to be promoted to a simple SSA
+ value instead of a memory location.</p>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div>
+ <div class="doc_text">
+ <p>It is important to note that this document describes 'well formed'
+ LLVM assembly language. There is a difference between what the parser
+ accepts and what is considered 'well formed'. For example, the
+ following instruction is syntactically okay, but not well formed:</p>
+ <pre> %x = <a href="#i_add">add</a> int 1, %x<br></pre>
+ <p>...because the definition of <tt>%x</tt> does not dominate all of
+ its uses. The LLVM infrastructure provides a verification pass that may
+ be used to verify that an LLVM module is well formed. This pass is
+ automatically run by the parser after parsing input assembly, and by
+ the optimizer before it outputs bytecode. The violations pointed out
+ by the verifier pass indicate bugs in transformation passes or input to
+ the parser.</p>
+ <!-- Describe the typesetting conventions here. --> </div>
+ <!-- *********************************************************************** -->
+ <div class="doc_section"> <a name="identifiers">Identifiers</a> </div>
+ <!-- *********************************************************************** -->
+ <div class="doc_text">
+ <p>LLVM uses three different forms of identifiers, for different
+ purposes:</p>
+ <ol>
+ <li>Numeric constants are represented as you would expect: 12, -3
+ 123.421, etc. Floating point constants have an optional hexidecimal
+ notation.</li>
+ <li>Named values are represented as a string of characters with a '%'
+ prefix. For example, %foo, %DivisionByZero,
+ %a.really.long.identifier. The actual regular expression used is '<tt>%[a-zA-Z$._][a-zA-Z$._0-9]*</tt>'.
+ Identifiers which require other characters in their names can be
+ surrounded with quotes. In this way, anything except a <tt>"</tt>
+ character can be used in a name.</li>
+ <li>Unnamed values are represented as an unsigned numeric value with
+ a '%' prefix. For example, %12, %2, %44.</li>
+ </ol>
+ <p>LLVM requires that values start with a '%' sign for two reasons:
+ Compilers don't need to worry about name clashes with reserved words,
+ and the set of reserved words may be expanded in the future without
+ penalty. Additionally, unnamed identifiers allow a compiler to quickly
+ come up with a temporary variable without having to avoid symbol table
+ conflicts.</p>
+ <p>Reserved words in LLVM are very similar to reserved words in other
+ languages. There are keywords for different opcodes ('<tt><a
+ href="#i_add">add</a></tt>', '<tt><a href="#i_cast">cast</a></tt>', '<tt><a
+ href="#i_ret">ret</a></tt>', etc...), for primitive type names ('<tt><a
+ href="#t_void">void</a></tt>', '<tt><a href="#t_uint">uint</a></tt>',
+ etc...), and others. These reserved words cannot conflict with
+ variable names, because none of them start with a '%' character.</p>
+ <p>Here is an example of LLVM code to multiply the integer variable '<tt>%X</tt>'
+ by 8:</p>
+ <p>The easy way:</p>
+ <pre> %result = <a href="#i_mul">mul</a> uint %X, 8<br></pre>
+ <p>After strength reduction:</p>
+ <pre> %result = <a href="#i_shl">shl</a> uint %X, ubyte 3<br></pre>
+ <p>And the hard way:</p>
+ <pre> <a href="#i_add">add</a> uint %X, %X <i>; yields {uint}:%0</i>
+ <a
+ href="#i_add">add</a> uint %0, %0 <i>; yields {uint}:%1</i>
+ %result = <a
+ href="#i_add">add</a> uint %1, %1<br></pre>
+ <p>This last way of multiplying <tt>%X</tt> by 8 illustrates several
+ important lexical features of LLVM:</p>
+ <ol>
+ <li>Comments are delimited with a '<tt>;</tt>' and go until the end
+ of line.</li>
+ <li>Unnamed temporaries are created when the result of a computation
+ is not assigned to a named value.</li>
+ <li>Unnamed temporaries are numbered sequentially</li>
+ </ol>
+ <p>...and it also show a convention that we follow in this document.
+ When demonstrating instructions, we will follow an instruction with a
+ comment that defines the type and name of value produced. Comments are
+ shown in italic text.</p>
+ <p>The one non-intuitive notation for constants is the optional
+ hexidecimal form of floating point constants. For example, the form '<tt>double
+ 0x432ff973cafa8000</tt>' is equivalent to (but harder to read than) '<tt>double
+ 4.5e+15</tt>' which is also supported by the parser. The only time
+ hexadecimal floating point constants are useful (and the only time that
+ they are generated by the disassembler) is when an FP constant has to
+ be emitted that is not representable as a decimal floating point number
+ exactly. For example, NaN's, infinities, and other special cases are
+ represented in their IEEE hexadecimal format so that assembly and
+ disassembly do not cause any bits to change in the constants.</p>
+ </div>
+ <!-- *********************************************************************** -->
+ <div class="doc_section"> <a name="typesystem">Type System</a> </div>
+ <!-- *********************************************************************** -->
+ <div class="doc_text">
+ <p>The LLVM type system is one of the most important features of the
+ intermediate representation. Being typed enables a number of
+ optimizations to be performed on the IR directly, without having to do
+ extra analyses on the side before the transformation. A strong type
+ system makes it easier to read the generated code and enables novel
+ analyses and transformations that are not feasible to perform on normal
+ three address code representations.</p>
+ <!-- The written form for the type system was heavily influenced by the
+ syntactic problems with types in the C language<sup><a
+ href="#rw_stroustrup">1</a></sup>.<p> --> </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div>
+ <div class="doc_text">
+ <p>The primitive types are the fundemental building blocks of the LLVM
+ system. The current set of primitive types are as follows:</p>
+
+ <table border="0" style="align: center">
+ <tbody>
+ <tr>
+ <td>
+ <table border="1" cellspacing="0" cellpadding="4" style="align: center">
+ <tbody>
+ <tr>
+ <td><tt>void</tt></td>
+ <td>No value</td>
+ </tr>
+ <tr>
+ <td><tt>ubyte</tt></td>
+ <td>Unsigned 8 bit value</td>
+ </tr>
+ <tr>
+ <td><tt>ushort</tt></td>
+ <td>Unsigned 16 bit value</td>
+ </tr>
+ <tr>
+ <td><tt>uint</tt></td>
+ <td>Unsigned 32 bit value</td>
+ </tr>
+ <tr>
+ <td><tt>ulong</tt></td>
+ <td>Unsigned 64 bit value</td>
+ </tr>
+ <tr>
+ <td><tt>float</tt></td>
+ <td>32 bit floating point value</td>
+ </tr>
+ <tr>
+ <td><tt>label</tt></td>
+ <td>Branch destination</td>
+ </tr>
+ </tbody>
+ </table>
+ </td>
+ <td valign="top">
+ <table border="1" cellspacing="0" cellpadding="4">
+ <tbody>
+ <tr>
+ <td><tt>bool</tt></td>
+ <td>True or False value</td>
+ </tr>
+ <tr>
+ <td><tt>sbyte</tt></td>
+ <td>Signed 8 bit value</td>
+ </tr>
+ <tr>
+ <td><tt>short</tt></td>
+ <td>Signed 16 bit value</td>
+ </tr>
+ <tr>
+ <td><tt>int</tt></td>
+ <td>Signed 32 bit value</td>
+ </tr>
+ <tr>
+ <td><tt>long</tt></td>
+ <td>Signed 64 bit value</td>
+ </tr>
+ <tr>
+ <td><tt>double</tt></td>
+ <td>64 bit floating point value</td>
+ </tr>
+ </tbody>
+ </table>
+ </td>
+ </tr>
+ </tbody>
+ </table>
+
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="t_classifications">Type
+ Classifications</a> </div>
+ <div class="doc_text">
+ <p>These different primitive types fall into a few useful
+ classifications:</p>
+
+ <table border="1" cellspacing="0" cellpadding="4">
+ <tbody>
+ <tr>
+ <td><a name="t_signed">signed</a></td>
+ <td><tt>sbyte, short, int, long, float, double</tt></td>
+ </tr>
+ <tr>
+ <td><a name="t_unsigned">unsigned</a></td>
+ <td><tt>ubyte, ushort, uint, ulong</tt></td>
+ </tr>
+ <tr>
+ <td><a name="t_integer">integer</a></td>
+ <td><tt>ubyte, sbyte, ushort, short, uint, int, ulong, long</tt></td>
+ </tr>
+ <tr>
+ <td><a name="t_integral">integral</a></td>
+ <td><tt>bool, ubyte, sbyte, ushort, short, uint, int, ulong, long</tt></td>
+ </tr>
+ <tr>
+ <td><a name="t_floating">floating point</a></td>
+ <td><tt>float, double</tt></td>
+ </tr>
+ <tr>
+ <td><a name="t_firstclass">first class</a></td>
+ <td><tt>bool, ubyte, sbyte, ushort, short,<br>
+ uint, int, ulong, long, float, double, <a href="#t_pointer">pointer</a></tt></td>
+ </tr>
+ </tbody>
+ </table>
+
+ <p>The <a href="#t_firstclass">first class</a> types are perhaps the
+ most important. Values of these types are the only ones which can be
+ produced by instructions, passed as arguments, or used as operands to
+ instructions. This means that all structures and arrays must be
+ manipulated either by pointer or by component.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="t_derived">Derived Types</a> </div>
+ <div class="doc_text">
+ <p>The real power in LLVM comes from the derived types in the system.
+ This is what allows a programmer to represent arrays, functions,
+ pointers, and other useful types. Note that these derived types may be
+ recursive: For example, it is possible to have a two dimensional array.</p>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div>
+ <div class="doc_text">
+ <h5>Overview:</h5>
+ <p>The array type is a very simple derived type that arranges elements
+ sequentially in memory. The array type requires a size (number of
+ elements) and an underlying data type.</p>
+ <h5>Syntax:</h5>
+ <pre> [<# elements> x <elementtype>]<br></pre>
+ <p>The number of elements is a constant integer value, elementtype may
+ be any type with a size.</p>
+ <h5>Examples:</h5>
+ <p> <tt>[40 x int ]</tt>: Array of 40 integer values.<br>
+ <tt>[41 x int ]</tt>: Array of 41 integer values.<br>
+ <tt>[40 x uint]</tt>: Array of 40 unsigned integer values.</p>
+ <p> </p>
+ <p>Here are some examples of multidimensional arrays:</p>
+
+ <table border="0" cellpadding="0" cellspacing="0">
+ <tbody>
+ <tr>
+ <td><tt>[3 x [4 x int]]</tt></td>
+ <td>: 3x4 array integer values.</td>
+ </tr>
+ <tr>
+ <td><tt>[12 x [10 x float]]</tt></td>
+ <td>: 12x10 array of single precision floating point values.</td>
+ </tr>
+ <tr>
+ <td><tt>[2 x [3 x [4 x uint]]]</tt></td>
+ <td>: 2x3x4 array of unsigned integer values.</td>
+ </tr>
+ </tbody>
+ </table>
+
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div>
+ <div class="doc_text">
+ <h5>Overview:</h5>
+ <p>The function type can be thought of as a function signature. It
+ consists of a return type and a list of formal parameter types.
+ Function types are usually used to build virtual function tables
+ (which are structures of pointers to functions), for indirect function
+ calls, and when defining a function.</p>
+ <p>
+ The return type of a function type cannot be an aggregate type.
+ </p>
+ <h5>Syntax:</h5>
+ <pre> <returntype> (<parameter list>)<br></pre>
+ <p>Where '<tt><parameter list></tt>' is a comma-separated list of
+ type specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
+ which indicates that the function takes a variable number of arguments.
+ Variable argument functions can access their arguments with the <a
+ href="#int_varargs">variable argument handling intrinsic</a> functions.</p>
+ <h5>Examples:</h5>
+
+ <table border="0" cellpadding="0" cellspacing="0">
+ <tbody>
+ <tr>
+ <td><tt>int (int)</tt></td>
+ <td>: function taking an <tt>int</tt>, returning an <tt>int</tt></td>
+ </tr>
+ <tr>
+ <td><tt>float (int, int *) *</tt></td>
+ <td>: <a href="#t_pointer">Pointer</a> to a function that takes
+ an <tt>int</tt> and a <a href="#t_pointer">pointer</a> to <tt>int</tt>,
+ returning <tt>float</tt>.</td>
+ </tr>
+ <tr>
+ <td><tt>int (sbyte *, ...)</tt></td>
+ <td>: A vararg function that takes at least one <a
+ href="#t_pointer">pointer</a> to <tt>sbyte</tt> (signed char in C),
+ which returns an integer. This is the signature for <tt>printf</tt>
+ in LLVM.</td>
+ </tr>
+ </tbody>
+ </table>
+
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="t_struct">Structure Type</a> </div>
+ <div class="doc_text">
+ <h5>Overview:</h5>
+ <p>The structure type is used to represent a collection of data members
+ together in memory. The packing of the field types is defined to match
+ the ABI of the underlying processor. The elements of a structure may
+ be any type that has a size.</p>
+ <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt>
+ and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a
+ field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>'
+ instruction.</p>
+ <h5>Syntax:</h5>
+ <pre> { <type list> }<br></pre>
+ <h5>Examples:</h5>
+
+ <table border="0" cellpadding="0" cellspacing="0">
+ <tbody>
+ <tr>
+ <td><tt>{ int, int, int }</tt></td>
+ <td>: a triple of three <tt>int</tt> values</td>
+ </tr>
+ <tr>
+ <td><tt>{ float, int (int) * }</tt></td>
+ <td>: A pair, where the first element is a <tt>float</tt> and the
+ second element is a <a href="#t_pointer">pointer</a> to a <a
+ href="t_function">function</a> that takes an <tt>int</tt>, returning
+ an <tt>int</tt>.</td>
+ </tr>
+ </tbody>
+ </table>
+
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div>
+ <div class="doc_text">
+ <h5>Overview:</h5>
+ <p>As in many languages, the pointer type represents a pointer or
+ reference to another object, which must live in memory.</p>
+ <h5>Syntax:</h5>
+ <pre> <type> *<br></pre>
+ <h5>Examples:</h5>
+
+ <table border="0" cellpadding="0" cellspacing="0">
+ <tbody>
+ <tr>
+ <td><tt>[4x int]*</tt></td>
+ <td>: <a href="#t_pointer">pointer</a> to <a href="#t_array">array</a>
+ of four <tt>int</tt> values</td>
+ </tr>
+ <tr>
+ <td><tt>int (int *) *</tt></td>
+ <td>: A <a href="#t_pointer">pointer</a> to a <a
+ href="t_function">function</a> that takes an <tt>int</tt>, returning
+ an <tt>int</tt>.</td>
+ </tr>
+ </tbody>
+ </table>
+
+ </div>
+ <!-- _______________________________________________________________________ --><!--
+ <div class="doc_subsubsection">
+ <a name="t_packed">Packed Type</a>
+ </div>
+
+ <div class="doc_text">
+
+ Mention/decide that packed types work with saturation or not. Maybe have a packed+saturated type in addition to just a packed type.<p>
+
+ Packed types should be 'nonsaturated' because standard data types are not saturated. Maybe have a saturated packed type?<p>
+
+ </div>
+
+ --><!-- *********************************************************************** -->
+ <div class="doc_section"> <a name="highlevel">High Level Structure</a> </div>
+ <!-- *********************************************************************** --><!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="modulestructure">Module Structure</a> </div>
+ <div class="doc_text">
+ <p>LLVM programs are composed of "Module"s, each of which is a
+ translation unit of the input programs. Each module consists of
+ functions, global variables, and symbol table entries. Modules may be
+ combined together with the LLVM linker, which merges function (and
+ global variable) definitions, resolves forward declarations, and merges
+ symbol table entries. Here is an example of the "hello world" module:</p>
+ <pre><i>; Declare the string constant as a global constant...</i>
+ <a href="#identifiers">%.LC0</a> = <a href="#linkage_internal">internal</a> <a
+ href="#globalvars">constant</a> <a href="#t_array">[13 x sbyte]</a> c"hello world\0A\00" <i>; [13 x sbyte]*</i>
+
+ <i>; External declaration of the puts function</i>
+ <a href="#functionstructure">declare</a> int %puts(sbyte*) <i>; int(sbyte*)* </i>
+
+ <i>; Definition of main function</i>
+ int %main() { <i>; int()* </i>
+ <i>; Convert [13x sbyte]* to sbyte *...</i>
+ %cast210 = <a
+ href="#i_getelementptr">getelementptr</a> [13 x sbyte]* %.LC0, long 0, long 0 <i>; sbyte*</i>
+
+ <i>; Call puts function to write out the string to stdout...</i>
+ <a
+ href="#i_call">call</a> int %puts(sbyte* %cast210) <i>; int</i>
+ <a
+ href="#i_ret">ret</a> int 0<br>}<br></pre>
+ <p>This example is made up of a <a href="#globalvars">global variable</a>
+ named "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>"
+ function, and a <a href="#functionstructure">function definition</a>
+ for "<tt>main</tt>".</p>
+ <a name="linkage"> In general, a module is made up of a list of global
+ values, where both functions and global variables are global values.
+ Global values are represented by a pointer to a memory location (in
+ this case, a pointer to an array of char, and a pointer to a function),
+ and have one of the following linkage types:</a>
+ <p> </p>
+ <dl>
+ <dt><tt><b><a name="linkage_internal">internal</a></b></tt> </dt>
+ <dd>Global values with internal linkage are only directly accessible
+ by objects in the current module. In particular, linking code into a
+ module with an internal global value may cause the internal to be
+ renamed as necessary to avoid collisions. Because the symbol is
+ internal to the module, all references can be updated. This
+ corresponds to the notion of the '<tt>static</tt>' keyword in C, or the
+ idea of "anonymous namespaces" in C++.
+ <p> </p>
+ </dd>
+ <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt>
+ <dd>"<tt>linkonce</tt>" linkage is similar to <tt>internal</tt>
+ linkage, with the twist that linking together two modules defining the
+ same <tt>linkonce</tt> globals will cause one of the globals to be
+ discarded. This is typically used to implement inline functions.
+ Unreferenced <tt>linkonce</tt> globals are allowed to be discarded.
+ <p> </p>
+ </dd>
+ <dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt>
+ <dd>"<tt>weak</tt>" linkage is exactly the same as <tt>linkonce</tt>
+ linkage, except that unreferenced <tt>weak</tt> globals may not be
+ discarded. This is used to implement constructs in C such as "<tt>int
+ X;</tt>" at global scope.
+ <p> </p>
+ </dd>
+ <dt><tt><b><a name="linkage_appending">appending</a></b></tt>: </dt>
+ <dd>"<tt>appending</tt>" linkage may only be applied to global
+ variables of pointer to array type. When two global variables with
+ appending linkage are linked together, the two global arrays are
+ appended together. This is the LLVM, typesafe, equivalent of having
+ the system linker append together "sections" with identical names when
+ .o files are linked.
+ <p> </p>
+ </dd>
+ <dt><tt><b><a name="linkage_external">externally visible</a></b></tt>:</dt>
+ <dd>If none of the above identifiers are used, the global is
+ externally visible, meaning that it participates in linkage and can be
+ used to resolve external symbol references.
+ <p> </p>
+ </dd>
+ </dl>
+ <p> </p>
+ <p><a name="linkage_external">For example, since the "<tt>.LC0</tt>"
+ variable is defined to be internal, if another module defined a "<tt>.LC0</tt>"
+ variable and was linked with this one, one of the two would be renamed,
+ preventing a collision. Since "<tt>main</tt>" and "<tt>puts</tt>" are
+ external (i.e., lacking any linkage declarations), they are accessible
+ outside of the current module. It is illegal for a function <i>declaration</i>
+ to have any linkage type other than "externally visible".</a></p>
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="globalvars">Global Variables</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Global variables define regions of memory allocated at compilation
+ time instead of run-time. Global variables may optionally be
+ initialized. A variable may be defined as a global "constant", which
+ indicates that the contents of the variable will never be modified
+ (opening options for optimization).</p>
+
+ <p>As SSA values, global variables define pointer values that are in
+ scope (i.e. they dominate) for all basic blocks in the program. Global
+ variables always define a pointer to their "content" type because they
+ describe a region of memory, and all memory objects in LLVM are
+ accessed through pointers.</p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="functionstructure">Functions</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>LLVM function definitions are composed of a (possibly empty) argument list,
+ an opening curly brace, a list of basic blocks, and a closing curly brace. LLVM
+ function declarations are defined with the "<tt>declare</tt>" keyword, a
+ function name, and a function signature.</p>
+
+ <p>A function definition contains a list of basic blocks, forming the CFG for
+ the function. Each basic block may optionally start with a label (giving the
+ basic block a symbol table entry), contains a list of instructions, and ends
+ with a <a href="#terminators">terminator</a> instruction (such as a branch or
+ function return).</p>
+
+ <p>The first basic block in program is special in two ways: it is immediately
+ executed on entrance to the function, and it is not allowed to have predecessor
+ basic blocks (i.e. there can not be any branches to the entry block of a
+ function). Because the block can have no predecessors, it also cannot have any
+ <a href="#i_phi">PHI nodes</a>.</p>
+
+ <p>LLVM functions are identified by their name and type signature. Hence, two
+ functions with the same name but different parameter lists or return values are
+ considered different functions, and LLVM will resolves references to each
+ appropriately.</p>
+
+ </div>
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section"> <a name="instref">Instruction Reference</a> </div>
+ <!-- *********************************************************************** -->
+ <div class="doc_text">
+ <p>The LLVM instruction set consists of several different
+ classifications of instructions: <a href="#terminators">terminator
+ instructions</a>, <a href="#binaryops">binary instructions</a>, <a
+ href="#memoryops">memory instructions</a>, and <a href="#otherops">other
+ instructions</a>.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="terminators">Terminator
+ Instructions</a> </div>
+ <div class="doc_text">
+ <p>As mentioned <a href="#functionstructure">previously</a>, every
+ basic block in a program ends with a "Terminator" instruction, which
+ indicates which block should be executed after the current block is
+ finished. These terminator instructions typically yield a '<tt>void</tt>'
+ value: they produce control flow, not values (the one exception being
+ the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p>
+ <p>There are five different terminator instructions: the '<a
+ href="#i_ret"><tt>ret</tt></a>' instruction, the '<a href="#i_br"><tt>br</tt></a>'
+ instruction, the '<a href="#i_switch"><tt>switch</tt></a>' instruction,
+ the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction, and the '<a
+ href="#i_unwind"><tt>unwind</tt></a>' instruction.</p>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_ret">'<tt>ret</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> ret <type> <value> <i>; Return a value from a non-void function</i>
+ ret void <i>; Return from void function</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>ret</tt>' instruction is used to return control flow (and a
+ value) from a function, back to the caller.</p>
+ <p>There are two forms of the '<tt>ret</tt>' instructruction: one that
+ returns a value and then causes control flow, and one that just causes
+ control flow to occur.</p>
+ <h5>Arguments:</h5>
+ <p>The '<tt>ret</tt>' instruction may return any '<a
+ href="#t_firstclass">first class</a>' type. Notice that a function is
+ not <a href="#wellformed">well formed</a> if there exists a '<tt>ret</tt>'
+ instruction inside of the function that returns a value that does not
+ match the return type of the function.</p>
+ <h5>Semantics:</h5>
+ <p>When the '<tt>ret</tt>' instruction is executed, control flow
+ returns back to the calling function's context. If the caller is a "<a
+ href="#i_call"><tt>call</tt></a> instruction, execution continues at
+ the instruction after the call. If the caller was an "<a
+ href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues
+ at the beginning "normal" of the destination block. If the instruction
+ returns a value, that value shall set the call or invoke instruction's
+ return value.</p>
+ <h5>Example:</h5>
+ <pre> ret int 5 <i>; Return an integer value of 5</i>
+ ret void <i>; Return from a void function</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_br">'<tt>br</tt>' Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> br bool <cond>, label <iftrue>, label <iffalse><br> br label <dest> <i>; Unconditional branch</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>br</tt>' instruction is used to cause control flow to
+ transfer to a different basic block in the current function. There are
+ two forms of this instruction, corresponding to a conditional branch
+ and an unconditional branch.</p>
+ <h5>Arguments:</h5>
+ <p>The conditional branch form of the '<tt>br</tt>' instruction takes a
+ single '<tt>bool</tt>' value and two '<tt>label</tt>' values. The
+ unconditional form of the '<tt>br</tt>' instruction takes a single '<tt>label</tt>'
+ value as a target.</p>
+ <h5>Semantics:</h5>
+ <p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>bool</tt>'
+ argument is evaluated. If the value is <tt>true</tt>, control flows
+ to the '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>,
+ control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p>
+ <h5>Example:</h5>
+ <pre>Test:<br> %cond = <a href="#i_setcc">seteq</a> int %a, %b<br> br bool %cond, label %IfEqual, label %IfUnequal<br>IfEqual:<br> <a
+ href="#i_ret">ret</a> int 1<br>IfUnequal:<br> <a href="#i_ret">ret</a> int 0<br></pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_switch">'<tt>switch</tt>' Instruction</a>
+ </div>
+
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+
+ <pre>
+ switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
+ </pre>
+
+ <h5>Overview:</h5>
+
+ <p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of
+ several different places. It is a generalization of the '<tt>br</tt>'
+ instruction, allowing a branch to occur to one of many possible
+ destinations.</p>
+
+
+ <h5>Arguments:</h5>
+
+ <p>The '<tt>switch</tt>' instruction uses three parameters: an integer
+ comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination, and
+ an array of pairs of comparison value constants and '<tt>label</tt>'s. The
+ table is not allowed to contain duplicate constant entries.</p>
+
+ <h5>Semantics:</h5>
+
+ <p>The <tt>switch</tt> instruction specifies a table of values and
+ destinations. When the '<tt>switch</tt>' instruction is executed, this
+ table is searched for the given value. If the value is found, the
+ corresponding destination is branched to, otherwise the default value
+ it transfered to.</p>
+
+ <h5>Implementation:</h5>
+
+ <p>Depending on properties of the target machine and the particular
+ <tt>switch</tt> instruction, this instruction may be code generated in different
+ ways, for example as a series of chained conditional branches, or with a lookup
+ table.</p>
+
+ <h5>Example:</h5>
+
+ <pre>
+ <i>; Emulate a conditional br instruction</i>
+ %Val = <a href="#i_cast">cast</a> bool %value to int
+ switch int %Val, label %truedest [int 0, label %falsedest ]
+
+ <i>; Emulate an unconditional br instruction</i>
+ switch uint 0, label %dest [ ]
+
+ <i>; Implement a jump table:</i>
+ switch uint %val, label %otherwise [ uint 0, label %onzero
+ uint 1, label %onone
+ uint 2, label %ontwo ]
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_invoke">'<tt>invoke</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = invoke <ptr to function ty> %<function ptr val>(<function args>)<br> to label <normal label> except label <exception label><br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>invoke</tt>' instruction causes control to transfer to a
+ specified function, with the possibility of control flow transfer to
+ either the '<tt>normal</tt>' <tt>label</tt> label or the '<tt>exception</tt>'<tt>label</tt>.
+ If the callee function returns with the "<tt><a href="#i_ret">ret</a></tt>"
+ instruction, control flow will return to the "normal" label. If the
+ callee (or any indirect callees) returns with the "<a href="#i_unwind"><tt>unwind</tt></a>"
+ instruction, control is interrupted, and continued at the dynamically
+ nearest "except" label.</p>
+ <h5>Arguments:</h5>
+ <p>This instruction requires several arguments:</p>
+ <ol>
+ <li>'<tt>ptr to function ty</tt>': shall be the signature of the
+ pointer to function value being invoked. In most cases, this is a
+ direct function invocation, but indirect <tt>invoke</tt>s are just as
+ possible, branching off an arbitrary pointer to function value. </li>
+ <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer
+ to a function to be invoked. </li>
+ <li>'<tt>function args</tt>': argument list whose types match the
+ function signature argument types. If the function signature indicates
+ the function accepts a variable number of arguments, the extra
+ arguments can be specified. </li>
+ <li>'<tt>normal label</tt>': the label reached when the called
+ function executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li>
+ <li>'<tt>exception label</tt>': the label reached when a callee
+ returns with the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li>
+ </ol>
+ <h5>Semantics:</h5>
+ <p>This instruction is designed to operate as a standard '<tt><a
+ href="#i_call">call</a></tt>' instruction in most regards. The
+ primary difference is that it establishes an association with a label,
+ which is used by the runtime library to unwind the stack.</p>
+ <p>This instruction is used in languages with destructors to ensure
+ that proper cleanup is performed in the case of either a <tt>longjmp</tt>
+ or a thrown exception. Additionally, this is important for
+ implementation of '<tt>catch</tt>' clauses in high-level languages that
+ support them.</p>
+ <h5>Example:</h5>
+ <pre> %retval = invoke int %Test(int 15)<br> to label %Continue<br> except label %TestCleanup <i>; {int}:retval set</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_unwind">'<tt>unwind</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> unwind<br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>unwind</tt>' instruction unwinds the stack, continuing
+ control flow at the first callee in the dynamic call stack which used
+ an <a href="#i_invoke"><tt>invoke</tt></a> instruction to perform the
+ call. This is primarily used to implement exception handling.</p>
+ <h5>Semantics:</h5>
+ <p>The '<tt>unwind</tt>' intrinsic causes execution of the current
+ function to immediately halt. The dynamic call stack is then searched
+ for the first <a href="#i_invoke"><tt>invoke</tt></a> instruction on
+ the call stack. Once found, execution continues at the "exceptional"
+ destination block specified by the <tt>invoke</tt> instruction. If
+ there is no <tt>invoke</tt> instruction in the dynamic call chain,
+ undefined behavior results.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="binaryops">Binary Operations</a> </div>
+ <div class="doc_text">
+ <p>Binary operators are used to do most of the computation in a
+ program. They require two operands, execute an operation on them, and
+ produce a single value. The result value of a binary operator is not
+ necessarily the same type as its operands.</p>
+ <p>There are several different binary operators:</p>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_add">'<tt>add</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = add <ty> <var1>, <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p>
+ <h5>Arguments:</h5>
+ <p>The two arguments to the '<tt>add</tt>' instruction must be either <a
+ href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
+ values. Both arguments must have identical types.</p>
+ <h5>Semantics:</h5>
+ <p>The value produced is the integer or floating point sum of the two
+ operands.</p>
+ <h5>Example:</h5>
+ <pre> <result> = add int 4, %var <i>; yields {int}:result = 4 + %var</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_sub">'<tt>sub</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = sub <ty> <var1>, <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>sub</tt>' instruction returns the difference of its two
+ operands.</p>
+ <p>Note that the '<tt>sub</tt>' instruction is used to represent the '<tt>neg</tt>'
+ instruction present in most other intermediate representations.</p>
+ <h5>Arguments:</h5>
+ <p>The two arguments to the '<tt>sub</tt>' instruction must be either <a
+ href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
+ values. Both arguments must have identical types.</p>
+ <h5>Semantics:</h5>
+ <p>The value produced is the integer or floating point difference of
+ the two operands.</p>
+ <h5>Example:</h5>
+ <pre> <result> = sub int 4, %var <i>; yields {int}:result = 4 - %var</i>
+ <result> = sub int 0, %val <i>; yields {int}:result = -%var</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_mul">'<tt>mul</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = mul <ty> <var1>, <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>mul</tt>' instruction returns the product of its two
+ operands.</p>
+ <h5>Arguments:</h5>
+ <p>The two arguments to the '<tt>mul</tt>' instruction must be either <a
+ href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
+ values. Both arguments must have identical types.</p>
+ <h5>Semantics:</h5>
+ <p>The value produced is the integer or floating point product of the
+ two operands.</p>
+ <p>There is no signed vs unsigned multiplication. The appropriate
+ action is taken based on the type of the operand.</p>
+ <h5>Example:</h5>
+ <pre> <result> = mul int 4, %var <i>; yields {int}:result = 4 * %var</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_div">'<tt>div</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = div <ty> <var1>, <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>div</tt>' instruction returns the quotient of its two
+ operands.</p>
+ <h5>Arguments:</h5>
+ <p>The two arguments to the '<tt>div</tt>' instruction must be either <a
+ href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
+ values. Both arguments must have identical types.</p>
+ <h5>Semantics:</h5>
+ <p>The value produced is the integer or floating point quotient of the
+ two operands.</p>
+ <h5>Example:</h5>
+ <pre> <result> = div int 4, %var <i>; yields {int}:result = 4 / %var</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_rem">'<tt>rem</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = rem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>rem</tt>' instruction returns the remainder from the
+ division of its two operands.</p>
+ <h5>Arguments:</h5>
+ <p>The two arguments to the '<tt>rem</tt>' instruction must be either <a
+ href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
+ values. Both arguments must have identical types.</p>
+ <h5>Semantics:</h5>
+ <p>This returns the <i>remainder</i> of a division (where the result
+ has the same sign as the divisor), not the <i>modulus</i> (where the
+ result has the same sign as the dividend) of a value. For more
+ information about the difference, see: <a
+ href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The
+ Math Forum</a>.</p>
+ <h5>Example:</h5>
+ <pre> <result> = rem int 4, %var <i>; yields {int}:result = 4 % %var</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_setcc">'<tt>set<i>cc</i></tt>'
+ Instructions</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = seteq <ty> <var1>, <var2> <i>; yields {bool}:result</i>
+ <result> = setne <ty> <var1>, <var2> <i>; yields {bool}:result</i>
+ <result> = setlt <ty> <var1>, <var2> <i>; yields {bool}:result</i>
+ <result> = setgt <ty> <var1>, <var2> <i>; yields {bool}:result</i>
+ <result> = setle <ty> <var1>, <var2> <i>; yields {bool}:result</i>
+ <result> = setge <ty> <var1>, <var2> <i>; yields {bool}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>set<i>cc</i></tt>' family of instructions returns a boolean
+ value based on a comparison of their two operands.</p>
+ <h5>Arguments:</h5>
+ <p>The two arguments to the '<tt>set<i>cc</i></tt>' instructions must
+ be of <a href="#t_firstclass">first class</a> type (it is not possible
+ to compare '<tt>label</tt>'s, '<tt>array</tt>'s, '<tt>structure</tt>'
+ or '<tt>void</tt>' values, etc...). Both arguments must have identical
+ types.</p>
+ <h5>Semantics:</h5>
+ <p>The '<tt>seteq</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
+ value if both operands are equal.<br>
+ The '<tt>setne</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
+ value if both operands are unequal.<br>
+ The '<tt>setlt</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
+ value if the first operand is less than the second operand.<br>
+ The '<tt>setgt</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
+ value if the first operand is greater than the second operand.<br>
+ The '<tt>setle</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
+ value if the first operand is less than or equal to the second operand.<br>
+ The '<tt>setge</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
+ value if the first operand is greater than or equal to the second
+ operand.</p>
+ <h5>Example:</h5>
+ <pre> <result> = seteq int 4, 5 <i>; yields {bool}:result = false</i>
+ <result> = setne float 4, 5 <i>; yields {bool}:result = true</i>
+ <result> = setlt uint 4, 5 <i>; yields {bool}:result = true</i>
+ <result> = setgt sbyte 4, 5 <i>; yields {bool}:result = false</i>
+ <result> = setle sbyte 4, 5 <i>; yields {bool}:result = true</i>
+ <result> = setge sbyte 4, 5 <i>; yields {bool}:result = false</i>
+ </pre>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="bitwiseops">Bitwise Binary
+ Operations</a> </div>
+ <div class="doc_text">
+ <p>Bitwise binary operators are used to do various forms of
+ bit-twiddling in a program. They are generally very efficient
+ instructions, and can commonly be strength reduced from other
+ instructions. They require two operands, execute an operation on them,
+ and produce a single value. The resulting value of the bitwise binary
+ operators is always the same type as its first operand.</p>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_and">'<tt>and</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = and <ty> <var1>, <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>and</tt>' instruction returns the bitwise logical and of
+ its two operands.</p>
+ <h5>Arguments:</h5>
+ <p>The two arguments to the '<tt>and</tt>' instruction must be <a
+ href="#t_integral">integral</a> values. Both arguments must have
+ identical types.</p>
+ <h5>Semantics:</h5>
+ <p>The truth table used for the '<tt>and</tt>' instruction is:</p>
+ <p> </p>
+ <div style="align: center">
+ <table border="1" cellspacing="0" cellpadding="4">
+ <tbody>
+ <tr>
+ <td>In0</td>
+ <td>In1</td>
+ <td>Out</td>
+ </tr>
+ <tr>
+ <td>0</td>
+ <td>0</td>
+ <td>0</td>
+ </tr>
+ <tr>
+ <td>0</td>
+ <td>1</td>
+ <td>0</td>
+ </tr>
+ <tr>
+ <td>1</td>
+ <td>0</td>
+ <td>0</td>
+ </tr>
+ <tr>
+ <td>1</td>
+ <td>1</td>
+ <td>1</td>
+ </tr>
+ </tbody>
+ </table>
+ </div>
+ <h5>Example:</h5>
+ <pre> <result> = and int 4, %var <i>; yields {int}:result = 4 & %var</i>
+ <result> = and int 15, 40 <i>; yields {int}:result = 8</i>
+ <result> = and int 4, 8 <i>; yields {int}:result = 0</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_or">'<tt>or</tt>' Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = or <ty> <var1>, <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive
+ or of its two operands.</p>
+ <h5>Arguments:</h5>
+ <p>The two arguments to the '<tt>or</tt>' instruction must be <a
+ href="#t_integral">integral</a> values. Both arguments must have
+ identical types.</p>
+ <h5>Semantics:</h5>
+ <p>The truth table used for the '<tt>or</tt>' instruction is:</p>
+ <p> </p>
+ <div style="align: center">
+ <table border="1" cellspacing="0" cellpadding="4">
+ <tbody>
+ <tr>
+ <td>In0</td>
+ <td>In1</td>
+ <td>Out</td>
+ </tr>
+ <tr>
+ <td>0</td>
+ <td>0</td>
+ <td>0</td>
+ </tr>
+ <tr>
+ <td>0</td>
+ <td>1</td>
+ <td>1</td>
+ </tr>
+ <tr>
+ <td>1</td>
+ <td>0</td>
+ <td>1</td>
+ </tr>
+ <tr>
+ <td>1</td>
+ <td>1</td>
+ <td>1</td>
+ </tr>
+ </tbody>
+ </table>
+ </div>
+ <h5>Example:</h5>
+ <pre> <result> = or int 4, %var <i>; yields {int}:result = 4 | %var</i>
+ <result> = or int 15, 40 <i>; yields {int}:result = 47</i>
+ <result> = or int 4, 8 <i>; yields {int}:result = 12</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_xor">'<tt>xor</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = xor <ty> <var1>, <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive
+ or of its two operands. The <tt>xor</tt> is used to implement the
+ "one's complement" operation, which is the "~" operator in C.</p>
+ <h5>Arguments:</h5>
+ <p>The two arguments to the '<tt>xor</tt>' instruction must be <a
+ href="#t_integral">integral</a> values. Both arguments must have
+ identical types.</p>
+ <h5>Semantics:</h5>
+ <p>The truth table used for the '<tt>xor</tt>' instruction is:</p>
+ <p> </p>
+ <div style="align: center">
+ <table border="1" cellspacing="0" cellpadding="4">
+ <tbody>
+ <tr>
+ <td>In0</td>
+ <td>In1</td>
+ <td>Out</td>
+ </tr>
+ <tr>
+ <td>0</td>
+ <td>0</td>
+ <td>0</td>
+ </tr>
+ <tr>
+ <td>0</td>
+ <td>1</td>
+ <td>1</td>
+ </tr>
+ <tr>
+ <td>1</td>
+ <td>0</td>
+ <td>1</td>
+ </tr>
+ <tr>
+ <td>1</td>
+ <td>1</td>
+ <td>0</td>
+ </tr>
+ </tbody>
+ </table>
+ </div>
+ <p> </p>
+ <h5>Example:</h5>
+ <pre> <result> = xor int 4, %var <i>; yields {int}:result = 4 ^ %var</i>
+ <result> = xor int 15, 40 <i>; yields {int}:result = 39</i>
+ <result> = xor int 4, 8 <i>; yields {int}:result = 12</i>
+ <result> = xor int %V, -1 <i>; yields {int}:result = ~%V</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_shl">'<tt>shl</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = shl <ty> <var1>, ubyte <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>shl</tt>' instruction returns the first operand shifted to
+ the left a specified number of bits.</p>
+ <h5>Arguments:</h5>
+ <p>The first argument to the '<tt>shl</tt>' instruction must be an <a
+ href="#t_integer">integer</a> type. The second argument must be an '<tt>ubyte</tt>'
+ type.</p>
+ <h5>Semantics:</h5>
+ <p>The value produced is <tt>var1</tt> * 2<sup><tt>var2</tt></sup>.</p>
+ <h5>Example:</h5>
+ <pre> <result> = shl int 4, ubyte %var <i>; yields {int}:result = 4 << %var</i>
+ <result> = shl int 4, ubyte 2 <i>; yields {int}:result = 16</i>
+ <result> = shl int 1, ubyte 10 <i>; yields {int}:result = 1024</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_shr">'<tt>shr</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = shr <ty> <var1>, ubyte <var2> <i>; yields {ty}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>shr</tt>' instruction returns the first operand shifted to
+ the right a specified number of bits.</p>
+ <h5>Arguments:</h5>
+ <p>The first argument to the '<tt>shr</tt>' instruction must be an <a
+ href="#t_integer">integer</a> type. The second argument must be an '<tt>ubyte</tt>'
+ type.</p>
+ <h5>Semantics:</h5>
+ <p>If the first argument is a <a href="#t_signed">signed</a> type, the
+ most significant bit is duplicated in the newly free'd bit positions.
+ If the first argument is unsigned, zero bits shall fill the empty
+ positions.</p>
+ <h5>Example:</h5>
+ <pre> <result> = shr int 4, ubyte %var <i>; yields {int}:result = 4 >> %var</i>
+ <result> = shr uint 4, ubyte 1 <i>; yields {uint}:result = 2</i>
+ <result> = shr int 4, ubyte 2 <i>; yields {int}:result = 1</i>
+ <result> = shr sbyte 4, ubyte 3 <i>; yields {sbyte}:result = 0</i>
+ <result> = shr sbyte -2, ubyte 1 <i>; yields {sbyte}:result = -1</i>
+ </pre>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="memoryops">Memory Access
+ Operations</a></div>
+ <div class="doc_text">
+ <p>A key design point of an SSA-based representation is how it
+ represents memory. In LLVM, no memory locations are in SSA form, which
+ makes things very simple. This section describes how to read, write,
+ allocate and free memory in LLVM.</p>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_malloc">'<tt>malloc</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = malloc <type>, uint <NumElements> <i>; yields {type*}:result</i>
+ <result> = malloc <type> <i>; yields {type*}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>malloc</tt>' instruction allocates memory from the system
+ heap and returns a pointer to it.</p>
+ <h5>Arguments:</h5>
+ <p>The '<tt>malloc</tt>' instruction allocates <tt>sizeof(<type>)*NumElements</tt>
+ bytes of memory from the operating system and returns a pointer of the
+ appropriate type to the program. The second form of the instruction is
+ a shorter version of the first instruction that defaults to allocating
+ one element.</p>
+ <p>'<tt>type</tt>' must be a sized type.</p>
+ <h5>Semantics:</h5>
+ <p>Memory is allocated using the system "<tt>malloc</tt>" function, and
+ a pointer is returned.</p>
+ <h5>Example:</h5>
+ <pre> %array = malloc [4 x ubyte ] <i>; yields {[%4 x ubyte]*}:array</i>
+
+ %size = <a
+ href="#i_add">add</a> uint 2, 2 <i>; yields {uint}:size = uint 4</i>
+ %array1 = malloc ubyte, uint 4 <i>; yields {ubyte*}:array1</i>
+ %array2 = malloc [12 x ubyte], uint %size <i>; yields {[12 x ubyte]*}:array2</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_free">'<tt>free</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> free <type> <value> <i>; yields {void}</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>free</tt>' instruction returns memory back to the unused
+ memory heap, to be reallocated in the future.</p>
+ <p> </p>
+ <h5>Arguments:</h5>
+ <p>'<tt>value</tt>' shall be a pointer value that points to a value
+ that was allocated with the '<tt><a href="#i_malloc">malloc</a></tt>'
+ instruction.</p>
+ <h5>Semantics:</h5>
+ <p>Access to the memory pointed to by the pointer is not longer defined
+ after this instruction executes.</p>
+ <h5>Example:</h5>
+ <pre> %array = <a href="#i_malloc">malloc</a> [4 x ubyte] <i>; yields {[4 x ubyte]*}:array</i>
+ free [4 x ubyte]* %array
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_alloca">'<tt>alloca</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = alloca <type>, uint <NumElements> <i>; yields {type*}:result</i>
+ <result> = alloca <type> <i>; yields {type*}:result</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>alloca</tt>' instruction allocates memory on the current
+ stack frame of the procedure that is live until the current function
+ returns to its caller.</p>
+ <h5>Arguments:</h5>
+ <p>The the '<tt>alloca</tt>' instruction allocates <tt>sizeof(<type>)*NumElements</tt>
+ bytes of memory on the runtime stack, returning a pointer of the
+ appropriate type to the program. The second form of the instruction is
+ a shorter version of the first that defaults to allocating one element.</p>
+ <p>'<tt>type</tt>' may be any sized type.</p>
+ <h5>Semantics:</h5>
+ <p>Memory is allocated, a pointer is returned. '<tt>alloca</tt>'d
+ memory is automatically released when the function returns. The '<tt>alloca</tt>'
+ instruction is commonly used to represent automatic variables that must
+ have an address available. When the function returns (either with the <tt><a
+ href="#i_ret">ret</a></tt> or <tt><a href="#i_invoke">invoke</a></tt>
+ instructions), the memory is reclaimed.</p>
+ <h5>Example:</h5>
+ <pre> %ptr = alloca int <i>; yields {int*}:ptr</i>
+ %ptr = alloca int, uint 4 <i>; yields {int*}:ptr</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_load">'<tt>load</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = load <ty>* <pointer><br> <result> = volatile load <ty>* <pointer><br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>load</tt>' instruction is used to read from memory.</p>
+ <h5>Arguments:</h5>
+ <p>The argument to the '<tt>load</tt>' instruction specifies the memory
+ address to load from. The pointer must point to a <a
+ href="t_firstclass">first class</a> type. If the <tt>load</tt> is
+ marked as <tt>volatile</tt> then the optimizer is not allowed to modify
+ the number or order of execution of this <tt>load</tt> with other
+ volatile <tt>load</tt> and <tt><a href="#i_store">store</a></tt>
+ instructions. </p>
+ <h5>Semantics:</h5>
+ <p>The location of memory pointed to is loaded.</p>
+ <h5>Examples:</h5>
+ <pre> %ptr = <a href="#i_alloca">alloca</a> int <i>; yields {int*}:ptr</i>
+ <a
+ href="#i_store">store</a> int 3, int* %ptr <i>; yields {void}</i>
+ %val = load int* %ptr <i>; yields {int}:val = int 3</i>
+ </pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_store">'<tt>store</tt>'
+ Instruction</a> </div>
+ <h5>Syntax:</h5>
+ <pre> store <ty> <value>, <ty>* <pointer> <i>; yields {void}</i>
+ volatile store <ty> <value>, <ty>* <pointer> <i>; yields {void}</i>
+ </pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>store</tt>' instruction is used to write to memory.</p>
+ <h5>Arguments:</h5>
+ <p>There are two arguments to the '<tt>store</tt>' instruction: a value
+ to store and an address to store it into. The type of the '<tt><pointer></tt>'
+ operand must be a pointer to the type of the '<tt><value></tt>'
+ operand. If the <tt>store</tt> is marked as <tt>volatile</tt> then the
+ optimizer is not allowed to modify the number or order of execution of
+ this <tt>store</tt> with other volatile <tt>load</tt> and <tt><a
+ href="#i_store">store</a></tt> instructions.</p>
+ <h5>Semantics:</h5>
+ <p>The contents of memory are updated to contain '<tt><value></tt>'
+ at the location specified by the '<tt><pointer></tt>' operand.</p>
+ <h5>Example:</h5>
+ <pre> %ptr = <a href="#i_alloca">alloca</a> int <i>; yields {int*}:ptr</i>
+ <a
+ href="#i_store">store</a> int 3, int* %ptr <i>; yields {void}</i>
+ %val = load int* %ptr <i>; yields {int}:val = int 3</i>
+ </pre>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_getelementptr">'<tt>getelementptr</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = getelementptr <ty>* <ptrval>{, long <aidx>|, ubyte <sidx>}*<br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>getelementptr</tt>' instruction is used to get the address
+ of a subelement of an aggregate data structure.</p>
+ <h5>Arguments:</h5>
+ <p>This instruction takes a list of <tt>long</tt> values and <tt>ubyte</tt>
+ constants that indicate what form of addressing to perform. The actual
+ types of the arguments provided depend on the type of the first pointer
+ argument. The '<tt>getelementptr</tt>' instruction is used to index
+ down through the type levels of a structure.</p>
+ <p>For example, let's consider a C code fragment and how it gets
+ compiled to LLVM:</p>
+ <pre>struct RT {<br> char A;<br> int B[10][20];<br> char C;<br>};<br>struct ST {<br> int X;<br> double Y;<br> struct RT Z;<br>};<br><br>int *foo(struct ST *s) {<br> return &s[1].Z.B[5][13];<br>}<br></pre>
+ <p>The LLVM code generated by the GCC frontend is:</p>
+ <pre>%RT = type { sbyte, [10 x [20 x int]], sbyte }<br>%ST = type { int, double, %RT }<br><br>int* "foo"(%ST* %s) {<br> %reg = getelementptr %ST* %s, long 1, ubyte 2, ubyte 1, long 5, long 13<br> ret int* %reg<br>}<br></pre>
+ <h5>Semantics:</h5>
+ <p>The index types specified for the '<tt>getelementptr</tt>'
+ instruction depend on the pointer type that is being index into. <a
+ href="t_pointer">Pointer</a> and <a href="t_array">array</a> types
+ require '<tt>long</tt>' values, and <a href="t_struct">structure</a>
+ types require '<tt>ubyte</tt>' <b>constants</b>.</p>
+ <p>In the example above, the first index is indexing into the '<tt>%ST*</tt>'
+ type, which is a pointer, yielding a '<tt>%ST</tt>' = '<tt>{ int,
+ double, %RT }</tt>' type, a structure. The second index indexes into
+ the third element of the structure, yielding a '<tt>%RT</tt>' = '<tt>{
+ sbyte, [10 x [20 x int]], sbyte }</tt>' type, another structure. The
+ third index indexes into the second element of the structure, yielding
+ a '<tt>[10 x [20 x int]]</tt>' type, an array. The two dimensions of
+ the array are subscripted into, yielding an '<tt>int</tt>' type. The '<tt>getelementptr</tt>'
+ instruction return a pointer to this element, thus yielding a '<tt>int*</tt>'
+ type.</p>
+ <p>Note that it is perfectly legal to index partially through a
+ structure, returning a pointer to an inner element. Because of this,
+ the LLVM code for the given testcase is equivalent to:</p>
+ <pre>int* "foo"(%ST* %s) {<br> %t1 = getelementptr %ST* %s , long 1 <i>; yields %ST*:%t1</i>
+ %t2 = getelementptr %ST* %t1, long 0, ubyte 2 <i>; yields %RT*:%t2</i>
+ %t3 = getelementptr %RT* %t2, long 0, ubyte 1 <i>; yields [10 x [20 x int]]*:%t3</i>
+ %t4 = getelementptr [10 x [20 x int]]* %t3, long 0, long 5 <i>; yields [20 x int]*:%t4</i>
+ %t5 = getelementptr [20 x int]* %t4, long 0, long 13 <i>; yields int*:%t5</i>
+ ret int* %t5
+ }
+ </pre>
+ <h5>Example:</h5>
+ <pre> <i>; yields [12 x ubyte]*:aptr</i>
+ %aptr = getelementptr {int, [12 x ubyte]}* %sptr, long 0, ubyte 1<br></pre>
+ <h5> Note To The Novice:</h5>
+ When using indexing into global arrays with the '<tt>getelementptr</tt>'
+ instruction, you must remember that the </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="otherops">Other Operations</a> </div>
+ <div class="doc_text">
+ <p>The instructions in this catagory are the "miscellaneous"
+ instructions, which defy better classification.</p>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_phi">'<tt>phi</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = phi <ty> [ <val0>, <label0>], ...<br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>phi</tt>' instruction is used to implement the φ node in
+ the SSA graph representing the function.</p>
+ <h5>Arguments:</h5>
+ <p>The type of the incoming values are specified with the first type
+ field. After this, the '<tt>phi</tt>' instruction takes a list of pairs
+ as arguments, with one pair for each predecessor basic block of the
+ current block. Only values of <a href="#t_firstclass">first class</a>
+ type may be used as the value arguments to the PHI node. Only labels
+ may be used as the label arguments.</p>
+ <p>There must be no non-phi instructions between the start of a basic
+ block and the PHI instructions: i.e. PHI instructions must be first in
+ a basic block.</p>
+ <h5>Semantics:</h5>
+ <p>At runtime, the '<tt>phi</tt>' instruction logically takes on the
+ value specified by the parameter, depending on which basic block we
+ came from in the last <a href="#terminators">terminator</a> instruction.</p>
+ <h5>Example:</h5>
+ <pre>Loop: ; Infinite loop that counts from 0 on up...<br> %indvar = phi uint [ 0, %LoopHeader ], [ %nextindvar, %Loop ]<br> %nextindvar = add uint %indvar, 1<br> br label %Loop<br></pre>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_cast">'<tt>cast .. to</tt>' Instruction</a>
+ </div>
+
+ <div class="doc_text">
+
+ <h5>Syntax:</h5>
+
+ <pre>
+ <result> = cast <ty> <value> to <ty2> <i>; yields ty2</i>
+ </pre>
+
+ <h5>Overview:</h5>
+
+ <p>
+ The '<tt>cast</tt>' instruction is used as the primitive means to convert
+ integers to floating point, change data type sizes, and break type safety (by
+ casting pointers).
+ </p>
+
+
+ <h5>Arguments:</h5>
+
+ <p>
+ The '<tt>cast</tt>' instruction takes a value to cast, which must be a first
+ class value, and a type to cast it to, which must also be a <a
+ href="#t_firstclass">first class</a> type.
+ </p>
+
+ <h5>Semantics:</h5>
+
+ <p>
+ This instruction follows the C rules for explicit casts when determining how the
+ data being cast must change to fit in its new container.
+ </p>
+
+ <p>
+ When casting to bool, any value that would be considered true in the context of
+ a C '<tt>if</tt>' condition is converted to the boolean '<tt>true</tt>' values,
+ all else are '<tt>false</tt>'.
+ </p>
+
+ <p>
+ When extending an integral value from a type of one signness to another (for
+ example '<tt>sbyte</tt>' to '<tt>ulong</tt>'), the value is sign-extended if the
+ <b>source</b> value is signed, and zero-extended if the source value is
+ unsigned. <tt>bool</tt> values are always zero extended into either zero or
+ one.
+ </p>
+
+ <h5>Example:</h5>
+
+ <pre>
+ %X = cast int 257 to ubyte <i>; yields ubyte:1</i>
+ %Y = cast int 123 to bool <i>; yields bool:true</i>
+ </pre>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_select">'<tt>select</tt>' Instruction</a>
+ </div>
+
+ <div class="doc_text">
+
+ <h5>Syntax:</h5>
+
+ <pre>
+ <result> = select bool <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i>
+ </pre>
+
+ <h5>Overview:</h5>
+
+ <p>
+ The '<tt>select</tt>' instruction is used to choose one value based on a
+ condition, without branching.
+ </p>
+
+
+ <h5>Arguments:</h5>
+
+ <p>
+ The '<tt>select</tt>' instruction requires a boolean value indicating the condition, and two values of the same <a href="#t_firstclass">first class</a> type.
+ </p>
+
+ <h5>Semantics:</h5>
+
+ <p>
+ If the boolean condition evaluates to true, the instruction returns the first
+ value argument, otherwise it returns the second value argument.
+ </p>
+
+ <h5>Example:</h5>
+
+ <pre>
+ %X = select bool true, ubyte 17, ubyte 42 <i>; yields ubyte:17</i>
+ </pre>
+ </div>
+
+
+
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_call">'<tt>call</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <result> = call <ty>* <fnptrval>(<param list>)<br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>call</tt>' instruction represents a simple function call.</p>
+ <h5>Arguments:</h5>
+ <p>This instruction requires several arguments:</p>
+ <ol>
+ <li>
+ <p>'<tt>ty</tt>': shall be the signature of the pointer to function
+ value being invoked. The argument types must match the types implied
+ by this signature.</p>
+ </li>
+ <li>
+ <p>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a
+ function to be invoked. In most cases, this is a direct function
+ invocation, but indirect <tt>call</tt>s are just as possible,
+ calling an arbitrary pointer to function values.</p>
+ </li>
+ <li>
+ <p>'<tt>function args</tt>': argument list whose types match the
+ function signature argument types. If the function signature
+ indicates the function accepts a variable number of arguments, the
+ extra arguments can be specified.</p>
+ </li>
+ </ol>
+ <h5>Semantics:</h5>
+ <p>The '<tt>call</tt>' instruction is used to cause control flow to
+ transfer to a specified function, with its incoming arguments bound to
+ the specified values. Upon a '<tt><a href="#i_ret">ret</a></tt>'
+ instruction in the called function, control flow continues with the
+ instruction after the function call, and the return value of the
+ function is bound to the result argument. This is a simpler case of
+ the <a href="#i_invoke">invoke</a> instruction.</p>
+ <h5>Example:</h5>
+ <pre> %retval = call int %test(int %argc)<br> call int(sbyte*, ...) *%printf(sbyte* %msg, int 12, sbyte 42);<br></pre>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_vanext">'<tt>vanext</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <resultarglist> = vanext <va_list> <arglist>, <argty><br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>vanext</tt>' instruction is used to access arguments passed
+ through the "variable argument" area of a function call. It is used to
+ implement the <tt>va_arg</tt> macro in C.</p>
+ <h5>Arguments:</h5>
+ <p>This instruction takes a <tt>valist</tt> value and the type of the
+ argument. It returns another <tt>valist</tt>.</p>
+ <h5>Semantics:</h5>
+ <p>The '<tt>vanext</tt>' instruction advances the specified <tt>valist</tt>
+ past an argument of the specified type. In conjunction with the <a
+ href="#i_vaarg"><tt>vaarg</tt></a> instruction, it is used to implement
+ the <tt>va_arg</tt> macro available in C. For more information, see
+ the variable argument handling <a href="#int_varargs">Intrinsic
+ Functions</a>.</p>
+ <p>It is legal for this instruction to be called in a function which
+ does not take a variable number of arguments, for example, the <tt>vfprintf</tt>
+ function.</p>
+ <p><tt>vanext</tt> is an LLVM instruction instead of an <a
+ href="#intrinsics">intrinsic function</a> because it takes an type as
+ an argument.</p>
+ <h5>Example:</h5>
+ <p>See the <a href="#int_varargs">variable argument processing</a>
+ section.</p>
+ </div>
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection"> <a name="i_vaarg">'<tt>vaarg</tt>'
+ Instruction</a> </div>
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> <resultval> = vaarg <va_list> <arglist>, <argty><br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>vaarg</tt>' instruction is used to access arguments passed
+ through the "variable argument" area of a function call. It is used to
+ implement the <tt>va_arg</tt> macro in C.</p>
+ <h5>Arguments:</h5>
+ <p>This instruction takes a <tt>valist</tt> value and the type of the
+ argument. It returns a value of the specified argument type.</p>
+ <h5>Semantics:</h5>
+ <p>The '<tt>vaarg</tt>' instruction loads an argument of the specified
+ type from the specified <tt>va_list</tt>. In conjunction with the <a
+ href="#i_vanext"><tt>vanext</tt></a> instruction, it is used to
+ implement the <tt>va_arg</tt> macro available in C. For more
+ information, see the variable argument handling <a href="#int_varargs">Intrinsic
+ Functions</a>.</p>
+ <p>It is legal for this instruction to be called in a function which
+ does not take a variable number of arguments, for example, the <tt>vfprintf</tt>
+ function.</p>
+ <p><tt>vaarg</tt> is an LLVM instruction instead of an <a
+ href="#intrinsics">intrinsic function</a> because it takes an type as
+ an argument.</p>
+ <h5>Example:</h5>
+ <p>See the <a href="#int_varargs">variable argument processing</a>
+ section.</p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section"> <a name="intrinsics">Intrinsic Functions</a> </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>LLVM supports the notion of an "intrinsic function". These functions have
+ well known names and semantics, and are required to follow certain
+ restrictions. Overall, these instructions represent an extension mechanism for
+ the LLVM language that does not require changing all of the transformations in
+ LLVM to add to the language (or the bytecode reader/writer, the parser,
+ etc...).</p>
+
+ <p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix, this
+ prefix is reserved in LLVM for intrinsic names, thus functions may not be named
+ this. Intrinsic functions must always be external functions: you cannot define
+ the body of intrinsic functions. Intrinsic functions may only be used in call
+ or invoke instructions: it is illegal to take the address of an intrinsic
+ function. Additionally, because intrinsic functions are part of the LLVM
+ language, it is required that they all be documented here if any are added.</p>
+
+
+ <p>
+ Adding an intrinsic to LLVM is straight-forward if it is possible to express the
+ concept in LLVM directly (ie, code generator support is not _required_). To do
+ this, extend the default implementation of the IntrinsicLowering class to handle
+ the intrinsic. Code generators use this class to lower intrinsics they do not
+ understand to raw LLVM instructions that they do.
+ </p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="int_varargs">Variable Argument Handling Intrinsics</a>
+ </div>
+
+ <div class="doc_text">
+ <p>Variable argument support is defined in LLVM with the <a
+ href="#i_vanext"><tt>vanext</tt></a> instruction and these three
+ intrinsic functions. These functions are related to the similarly
+ named macros defined in the <tt><stdarg.h></tt> header file.</p>
+ <p>All of these functions operate on arguments that use a
+ target-specific value type "<tt>va_list</tt>". The LLVM assembly
+ language reference manual does not define what this type is, so all
+ transformations should be prepared to handle intrinsics with any type
+ used.</p>
+ <p>This example shows how the <a href="#i_vanext"><tt>vanext</tt></a>
+ instruction and the variable argument handling intrinsic functions are
+ used.</p>
+ <pre>
+ int %test(int %X, ...) {
+ ; Initialize variable argument processing
+ %ap = call sbyte* %<a href="#i_va_start">llvm.va_start</a>()
+
+ ; Read a single integer argument
+ %tmp = vaarg sbyte* %ap, int
+
+ ; Advance to the next argument
+ %ap2 = vanext sbyte* %ap, int
+
+ ; Demonstrate usage of llvm.va_copy and llvm.va_end
+ %aq = call sbyte* %<a href="#i_va_copy">llvm.va_copy</a>(sbyte* %ap2)
+ call void %<a href="#i_va_end">llvm.va_end</a>(sbyte* %aq)
+
+ ; Stop processing of arguments.
+ call void %<a href="#i_va_end">llvm.va_end</a>(sbyte* %ap2)
+ ret int %tmp
+ }
+ </pre>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a>
+ </div>
+
+
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> call va_list ()* %llvm.va_start()<br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>llvm.va_start</tt>' intrinsic returns a new <tt><arglist></tt>
+ for subsequent use by the variable argument intrinsics.</p>
+ <h5>Semantics:</h5>
+ <p>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt>
+ macro available in C. In a target-dependent way, it initializes and
+ returns a <tt>va_list</tt> element, so that the next <tt>vaarg</tt>
+ will produce the first variable argument passed to the function. Unlike
+ the C <tt>va_start</tt> macro, this intrinsic does not need to know the
+ last argument of the function, the compiler can figure that out.</p>
+ <p>Note that this intrinsic function is only legal to be called from
+ within the body of a variable argument function.</p>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a>
+ </div>
+
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> call void (va_list)* %llvm.va_end(va_list <arglist>)<br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt><arglist></tt>
+ which has been initialized previously with <tt><a href="#i_va_start">llvm.va_start</a></tt>
+ or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p>
+ <h5>Arguments:</h5>
+ <p>The argument is a <tt>va_list</tt> to destroy.</p>
+ <h5>Semantics:</h5>
+ <p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt>
+ macro available in C. In a target-dependent way, it destroys the <tt>va_list</tt>.
+ Calls to <a href="#i_va_start"><tt>llvm.va_start</tt></a> and <a
+ href="#i_va_copy"><tt>llvm.va_copy</tt></a> must be matched exactly
+ with calls to <tt>llvm.va_end</tt>.</p>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a>
+ </div>
+
+ <div class="doc_text">
+ <h5>Syntax:</h5>
+ <pre> call va_list (va_list)* %llvm.va_copy(va_list <destarglist>)<br></pre>
+ <h5>Overview:</h5>
+ <p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument
+ position from the source argument list to the destination argument list.</p>
+ <h5>Arguments:</h5>
+ <p>The argument is the <tt>va_list</tt> to copy.</p>
+ <h5>Semantics:</h5>
+ <p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt>
+ macro available in C. In a target-dependent way, it copies the source <tt>va_list</tt>
+ element into the returned list. This intrinsic is necessary because the <tt><a
+ href="i_va_start">llvm.va_start</a></tt> intrinsic may be arbitrarily
+ complex and require memory allocation, for example.</p>
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="int_codegen">Code Generator Intrinsics</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ These intrinsics are provided by LLVM to expose special features that may only
+ be implemented with code generator support.
+ </p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a>
+ </div>
+
+ <div class="doc_text">
+
+ <h5>Syntax:</h5>
+ <pre>
+ call void* ()* %llvm.returnaddress(uint <level>)
+ </pre>
+
+ <h5>Overview:</h5>
+
+ <p>
+ The '<tt>llvm.returnaddress</tt>' intrinsic returns a target-specific value
+ indicating the return address of the current function or one of its callers.
+ </p>
+
+ <h5>Arguments:</h5>
+
+ <p>
+ The argument to this intrinsic indicates which function to return the address
+ for. Zero indicates the calling function, one indicates its caller, etc. The
+ argument is <b>required</b> to be a constant integer value.
+ </p>
+
+ <h5>Semantics:</h5>
+
+ <p>
+ The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer indicating
+ the return address of the specified call frame, or zero if it cannot be
+ identified. The value returned by this intrinsic is likely to be incorrect or 0
+ for arguments other than zero, so it should only be used for debugging purposes.
+ </p>
+
+ <p>
+ Note that calling this intrinsic does not prevent function inlining or other
+ aggressive transformations, so the value returned may not that of the obvious
+ source-language caller.
+ </p>
+ </div>
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a>
+ </div>
+
+ <div class="doc_text">
+
+ <h5>Syntax:</h5>
+ <pre>
+ call void* ()* %llvm.frameaddress(uint <level>)
+ </pre>
+
+ <h5>Overview:</h5>
+
+ <p>
+ The '<tt>llvm.frameaddress</tt>' intrinsic returns the target-specific frame
+ pointer value for the specified stack frame.
+ </p>
+
+ <h5>Arguments:</h5>
+
+ <p>
+ The argument to this intrinsic indicates which function to return the frame
+ pointer for. Zero indicates the calling function, one indicates its caller,
+ etc. The argument is <b>required</b> to be a constant integer value.
+ </p>
+
+ <h5>Semantics:</h5>
+
+ <p>
+ The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer indicating
+ the frame address of the specified call frame, or zero if it cannot be
+ identified. The value returned by this intrinsic is likely to be incorrect or 0
+ for arguments other than zero, so it should only be used for debugging purposes.
+ </p>
+
+ <p>
+ Note that calling this intrinsic does not prevent function inlining or other
+ aggressive transformations, so the value returned may not that of the obvious
+ source-language caller.
+ </p>
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="int_libc">Standard C Library Intrinsics</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ LLVM provides intrinsics for a few important standard C library functions.
+ These intrinsics allow source-language front-ends to pass information about the
+ alignment of the pointer arguments to the code generator, providing opportunity
+ for more efficient code generation.
+ </p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a>
+ </div>
+
+ <div class="doc_text">
+
+ <h5>Syntax:</h5>
+ <pre>
+ call void (sbyte*, sbyte*, uint, uint)* %llvm.memcpy(sbyte* <dest>, sbyte* <src>,
+ uint <len>, uint <align>)
+ </pre>
+
+ <h5>Overview:</h5>
+
+ <p>
+ The '<tt>llvm.memcpy</tt>' intrinsic copies a block of memory from the source
+ location to the destination location.
+ </p>
+
+ <p>
+ Note that, unlike the standard libc function, the <tt>llvm.memcpy</tt> intrinsic
+ does not return a value, and takes an extra alignment argument.
+ </p>
+
+ <h5>Arguments:</h5>
+
+ <p>
+ The first argument is a pointer to the destination, the second is a pointer to
+ the source. The third argument is an (arbitrarily sized) integer argument
+ specifying the number of bytes to copy, and the fourth argument is the alignment
+ of the source and destination locations.
+ </p>
+
+ <p>
+ If the call to this intrinisic has an alignment value that is not 0 or 1, then
+ the caller guarantees that the size of the copy is a multiple of the alignment
+ and that both the source and destination pointers are aligned to that boundary.
+ </p>
+
+ <h5>Semantics:</h5>
+
+ <p>
+ The '<tt>llvm.memcpy</tt>' intrinsic copies a block of memory from the source
+ location to the destination location, which are not allowed to overlap. It
+ copies "len" bytes of memory over. If the argument is known to be aligned to
+ some boundary, this can be specified as the fourth argument, otherwise it should
+ be set to 0 or 1.
+ </p>
+ </div>
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a>
+ </div>
+
+ <div class="doc_text">
+
+ <h5>Syntax:</h5>
+ <pre>
+ call void (sbyte*, sbyte*, uint, uint)* %llvm.memmove(sbyte* <dest>, sbyte* <src>,
+ uint <len>, uint <align>)
+ </pre>
+
+ <h5>Overview:</h5>
+
+ <p>
+ The '<tt>llvm.memmove</tt>' intrinsic moves a block of memory from the source
+ location to the destination location. It is similar to the '<tt>llvm.memcpy</tt>'
+ intrinsic but allows the two memory locations to overlap.
+ </p>
+
+ <p>
+ Note that, unlike the standard libc function, the <tt>llvm.memmove</tt> intrinsic
+ does not return a value, and takes an extra alignment argument.
+ </p>
+
+ <h5>Arguments:</h5>
+
+ <p>
+ The first argument is a pointer to the destination, the second is a pointer to
+ the source. The third argument is an (arbitrarily sized) integer argument
+ specifying the number of bytes to copy, and the fourth argument is the alignment
+ of the source and destination locations.
+ </p>
+
+ <p>
+ If the call to this intrinisic has an alignment value that is not 0 or 1, then
+ the caller guarantees that the size of the copy is a multiple of the alignment
+ and that both the source and destination pointers are aligned to that boundary.
+ </p>
+
+ <h5>Semantics:</h5>
+
+ <p>
+ The '<tt>llvm.memmove</tt>' intrinsic copies a block of memory from the source
+ location to the destination location, which may overlap. It
+ copies "len" bytes of memory over. If the argument is known to be aligned to
+ some boundary, this can be specified as the fourth argument, otherwise it should
+ be set to 0 or 1.
+ </p>
+ </div>
+
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="i_memset">'<tt>llvm.memset</tt>' Intrinsic</a>
+ </div>
+
+ <div class="doc_text">
+
+ <h5>Syntax:</h5>
+ <pre>
+ call void (sbyte*, ubyte, uint, uint)* %llvm.memset(sbyte* <dest>, ubyte <val>,
+ uint <len>, uint <align>)
+ </pre>
+
+ <h5>Overview:</h5>
+
+ <p>
+ The '<tt>llvm.memset</tt>' intrinsic fills a block of memory with a particular
+ byte value.
+ </p>
+
+ <p>
+ Note that, unlike the standard libc function, the <tt>llvm.memset</tt> intrinsic
+ does not return a value, and takes an extra alignment argument.
+ </p>
+
+ <h5>Arguments:</h5>
+
+ <p>
+ The first argument is a pointer to the destination to fill, the second is the
+ byte value to fill it with, the third argument is an (arbitrarily sized) integer
+ argument specifying the number of bytes to fill, and the fourth argument is the
+ known alignment of destination location.
+ </p>
+
+ <p>
+ If the call to this intrinisic has an alignment value that is not 0 or 1, then
+ the caller guarantees that the size of the copy is a multiple of the alignment
+ and that the destination pointer is aligned to that boundary.
+ </p>
+
+ <h5>Semantics:</h5>
+
+ <p>
+ The '<tt>llvm.memset</tt>' intrinsic fills "len" bytes of memory starting at the
+ destination location. If the argument is known to be aligned to some boundary,
+ this can be specified as the fourth argument, otherwise it should be set to 0 or
+ 1.
+ </p>
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="int_debugger">Debugger Intrinsics</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt> prefix),
+ are described in the <a
+ href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source Level
+ Debugging</a> document.
+ </p>
+ </div>
+
+
+ <!-- *********************************************************************** -->
+ <hr>
+ <address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
+
+ <a href="mailto:sabre at nondot.org">Chris Lattner</a><br>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </address>
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/Makefile
diff -c /dev/null llvm-www/releases/1.2/docs/Makefile:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/Makefile Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,14 ----
+ ##===- docs/Makefile ---------------------------------------*- Makefile -*-===##
+ #
+ # The LLVM Compiler Infrastructure
+ #
+ # This file was developed by the LLVM research group and is distributed under
+ # the University of Illinois Open Source License. See LICENSE.TXT for details.
+ #
+ ##===----------------------------------------------------------------------===##
+ doxygen-files:
+ doxygen doxygen.cfg
+
+ doxygen.tar.gz: doxygen/index.html
+ rm -rf $@
+ gtar czvf $@ doxygen
Index: llvm-www/releases/1.2/docs/ObjectFiles.html
diff -c /dev/null llvm-www/releases/1.2/docs/ObjectFiles.html:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/ObjectFiles.html Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,298 ----
+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
+ <html>
+ <head>
+ <title>Object Files: Understanding The Result Of LLVM Compilation</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+ <div class="doc_title">Object Files: Understanding The Result Of LLVM Compilation</div>
+ <hr>
+ <ol>
+ <li><a href="#abstract">Abstract</a></li>
+ <li><a href="#introduction">Introduction</a></li>
+ <li><a href="#files">File Contents</a></li>
+ <li><a href="#rot">Linkage Rules Of Thumb</a>
+ <ol>
+ <li><a href="#always">Always Link vmcore.o, support.a</a>
+ <li><a href="#placeholder">Placeholder</a>
+ </ol>
+ </li>
+ </ol>
+ <div class="doc_text">
+ <p><b>Written by <a href="mailto:rspencer at x10sys.com">Reid Spencer</a> </b></p>
+ <p> </p>
+ </div>
+ <hr>
+ <!-- ======================================================================= -->
+ <div class="doc_section"><a name="abstract">Abstract</a></div>
+ <div class="doc_text">
+ <p>This document describes the contents of the many objects files and libraries
+ that are produced by compiling LLVM. To make use of LLVM this information is
+ needed in order to understand what files should be linked into your program.
+ </p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_section"> <a name="introduction">Introduction</a></div>
+ <div class="doc_text">
+ <p>If you're writing a compiler, virtual machine, or any other utility for
+ LLVM, you'll need to figure out which of the many .a (archive) and .o
+ (object) files you will need to link with to be successful. An
+ understanding of the contents of these files and their inter-relationships
+ will be useful in coming up with an optimal specification for the objects
+ and libraries to link with.
+ </p>
+ <p>The purpose of this document is to hopefully reduce some of the trial and
+ error that the author experienced in using LLVM.
+ </p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_section"><a name="files"></a>File Contents</div>
+ <div class="doc_text">
+ <p>The table below provides a summary of the basic contents of each file.</p>
+ <table class="doc_table"
+ style="width:80%; text-align: left; border: 2px solid blue; border-collapse: collapse;">
+ <tr class="doc_table">
+ <td colspan="2" class="doc_section">Summary Of LLVM Library And Object Files
+ </td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue"><h2><u>Library</u></h2></td>
+ <td style="border: 2px solid blue"><h2><u>Description</u></h2></td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libipo.a</td>
+ <td style="border: 2px solid blue">
+ An archive of all inter-procedural optimizations.
+ </td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libscalaropts.a</td>
+ <td style="border: 2px solid blue">
+ An archive of all scalar optimizations.
+ </td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libtransforms.a</td>
+ <td style="border: 2px solid blue">
+ An archive of just the level raise pass.
+ </td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libtarget.a</td>
+ <td style="border: 2px solid blue">
+ An archive containing code generator support for describing
+ target architectures.
+ </td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libanalysis.a</td>
+ <td style="border: 2px solid blue">
+ An archive containing intra-procedural analyses.
+ </td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libdatastructure.a</td>
+ <td style="border: 2px solid blue">
+ An archive containing optimizations for data structures.
+ </td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libinstrument.a</td>
+ <td style="border: 2px solid blue">No idea.</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libregalloc.a</td>
+ <td style="border: 2px solid blue">Register Allocation code.</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libipa.a</td>
+ <td style="border: 2px solid blue">
+ An archive containing inter-procedural analyses</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libtransformutils.a</td>
+ <td style="border: 2px solid blue">
+ Utiltities for transformations?
+ </td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libsupport.a</td>
+ <td style="border: 2px solid blue">General support utilities</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">libevar.a</td>
+ <td style="border: 2px solid blue">Live variable analysis for SPARC</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue"><h2><u>Object File</u></h2></td>
+ <td style="border: 2px solid blue"><h2><u>Description</u></h2></td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">support.o</td>
+ <td style="border: 2px solid blue">General support utilities</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">asmparser.o</td>
+ <td style="border: 2px solid blue">Assembler Parser</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">bcreader.o</td>
+ <td style="border: 2px solid blue">Byte Code Reader</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">bcwriter.o</td>
+ <td style="border: 2px solid blue">Byte Code Writer</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">sched.o</td>
+ <td style="border: 2px solid blue">SPARC instruction scheduler</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">selectiondag.o</td>
+ <td style="border: 2px solid blue">Aggressive instruction selector for Directed Acyclic Graphs</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">transformutils.o</td>
+ <td style="border: 2px solid blue">Utilities for code transformations</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">ipa.o</td>
+ <td style="border: 2px solid blue">Inter-Procedural Analysis Optimizations</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">select.o</td>
+ <td style="border: 2px solid blue">SPARC instruction selector</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">cwriter.o</td>
+ <td style="border: 2px solid blue">"C" Code Writer</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">profpaths.o</td>
+ <td style="border: 2px solid blue">Path profiling instrumentation</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">regalloc.o</td>
+ <td style="border: 2px solid blue">Register Allocation</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">instrument.o</td>
+ <td style="border: 2px solid blue">Instrumentation? Of What?</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">datastructure.o</td>
+ <td style="border: 2px solid blue">Data Structure Analysis</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">codegen.o</td>
+ <td style="border: 2px solid blue">Native code generation</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">livevar.o</td>
+ <td style="border: 2px solid blue">Live Variable Analysis</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">vmcore.o</td>
+ <td style="border: 2px solid blue">Virtual Machine Core</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">lli-interpreter.o</td>
+ <td style="border: 2px solid blue">Interpreter for LLVM ByteCode</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">lli-jit.o</td>
+ <td style="border: 2px solid blue">
+ Just-In-Time Compiler For LLVM ByteCode
+ </td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">executionengine.o</td>
+ <td style="border: 2px solid blue">Engine for LLI</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">debugger.o</td>
+ <td style="border: 2px solid blue">Source Level Debugging Support</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">analysis.o</td>
+ <td style="border: 2px solid blue">General Framework For Analysis?</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">sparc.o</td>
+ <td style="border: 2px solid blue">Sun SPARC Processor Specific</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">target.o</td>
+ <td style="border: 2px solid blue">Target Machine Support?</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">transforms.o</td>
+ <td style="border: 2px solid blue">Code Transformations</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">x86.o</td>
+ <td style="border: 2px solid blue">Intel x86 Processor Specific</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">powerpc.o</td>
+ <td style="border: 2px solid blue">PowerPC Processor Specific</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">scalaropts.o</td>
+ <td style="border: 2px solid blue">Optimizations For Scalars</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">ipo.o</td>
+ <td style="border: 2px solid blue">Inter-Procedural Optimization</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">trace.o</td>
+ <td style="border: 2px solid blue">Support For Tracing/Debugging?</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">profile_rt.o</td>
+ <td style="border: 2px solid blue">Runtime Library For Profiler</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">sample.o</td>
+ <td style="border: 2px solid blue">Sample Program ?</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">stkr_compiler.o</td>
+ <td style="border: 2px solid blue">Stacker Language Compiler Library</td>
+ </tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue">stkr_runtime.o</td>
+ <td style="border: 2px solid blue">Stacker Language Runtime Library</td>
+ </tr>
+ </table>
+ </div>
+ <p></p>
+ <!-- ======================================================================= -->
+ <div class="doc_section"><a name="rot">Linkage Rules Of Thumb</a></div>
+ <div class="doc_text">
+ <p>This section contains various "rules of thumb" about what files you
+ should link into your programs.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="always">Always Link vmcore.o support.a</a>
+ </div>
+ <div class="doc_text">
+ <p>No matter what you do with LLVM, you'll always need to link with vmcore.o
+ and support.a.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="Placeholder">Placeholder</a></div>
+ <div class="doc_text">
+ <p>Need more rules of thumb here.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <hr>
+ <div class="doc_footer">
+ <address><a href="mailto:rspencer at x10sys.com">Reid Spencer</a></address>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>Last modified: $Date: 2004/03/19 17:38:11 $ </div>
+ </body>
+ </html>
+ <!-- vim: sw=2 ts=2 ai
+ -->
Index: llvm-www/releases/1.2/docs/OpenProjects.html
diff -c /dev/null llvm-www/releases/1.2/docs/OpenProjects.html:1.1
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--- llvm-www/releases/1.2/docs/OpenProjects.html Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,334 ----
+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>Open LLVM Projects</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">
+ Open LLVM Projects
+ </div>
+
+ <ul>
+ <li><a href="#what">What is this?</a></li>
+ <li><a href="#improving">Improving the current system</a>
+ <ol>
+ <li><a href="#glibc">Port glibc to LLVM</a></li>
+ <li><a href="#NightlyTest">Improving the Nightly Tester</a></li>
+ <li><a href="#programs">Compile programs with the LLVM Compiler</a></li>
+ <li><a href="#llvm_ir">Extend the LLVM intermediate representation</a></li>
+ <li><a href="#misc_imp">Miscellaneous Improvements</a></li>
+ </ol></li>
+
+ <li><a href="#new">Adding new capabilities to LLVM</a>
+ <ol>
+ <li><a href="#pointeranalysis">Pointer and Alias Analysis</a></li>
+ <li><a href="#profileguided">Profile Guided Optimization</a></li>
+ <li><a href="#xforms">New Transformations and Analyses</a></li>
+ <li><a href="#x86be">X86 Back-end Improvements</a></li>
+ <li><a href="#misc_new">Miscellaneous Additions</a></li>
+ </ol></li>
+ </ul>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="what">What is this?</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This document is meant to be a sort of "big TODO list" for LLVM. Each
+ project in this document is something that would be useful for LLVM to have, and
+ would also be a great way to get familiar with the system. Some of these
+ projects are small and self-contained, which may be implemented in a couple of
+ days, others are larger. Several of these projects may lead to interesting
+ research projects in their own right. In any case, we welcome all
+ contributions.</p>
+
+ <p>If you are thinking about tackling one of these projects, please send a mail
+ to the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM
+ Developer's</a> mailing list, so that we know the project is being worked on.
+ Additionally this is a good way to get more information about a specific project
+ or to suggest other projects to add to this page.
+ </p>
+
+ <p>The projects in this page are open ended. More specific projects are
+ filed as unassigned enhancements in our <a href="http://llvm.cs.uiuc.edu/bugs/">
+ LLVM bug tracker</a>. Here is the current list:
+ </p>
+
+ <iframe src="http://llvm.cs.uiuc.edu/bugs/buglist.cgi?keywords_type=allwords&keywords=&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&bug_severity=enhancement&emailassigned_to1=1&emailtype1=substring&email1=unassigned" frameborder="1" align="center" width="100%" height="400">
+ </iframe>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="improving">Improving the current system</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Improvements to the current infrastructure are always very welcome and tend
+ to be fairly straight-forward to implement. Here are some of the key areas that
+ can use improvement...</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="glibc">Port glibc to LLVM</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>It would be very useful to <a
+ href="http://www.gnu.org/software/libc/porting.html">port</a> <a
+ href="http://www.gnu.org/software/glibc/">glibc</a> to LLVM. This would allow a
+ variety of interprocedural algorithms to be much more effective in the face of
+ library calls. The most important pieces to port are things like the string
+ library and the <tt>stdio</tt> related functions... low-level system calls like
+ '<tt>read</tt>' should stay unimplemented in LLVM.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="NightlyTest">Improving the Nightly Tester</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <a href="/testresults/">Nightly Tester</a> is a simple perl script
+ (located in <tt>utils/NightlyTest.pl</tt>) which runs every night to generate a
+ daily report. It could use the following improvements:</p>
+
+ <ol>
+ <li>Regression tests - We should run the regression tests in addition to the
+ program tests...</li>
+ </ol>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="programs">Compile programs with the LLVM Compiler</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>We are always looking for new testcases and benchmarks for use with LLVM. In
+ particular, it is useful to try compiling your favorite C source code with LLVM.
+ If it doesn't compile, try to figure out why or report it to the <a
+ href="http://mail.cs.uiuc.edu/pipermail/llvmbugs/">llvm-bugs</a> list. If you
+ get the program to compile, it would be extremely useful to convert the build
+ system to be compatible with the LLVM Programs testsuite so that we can check it
+ into CVS and the automated tester can use it to track progress of the
+ compiler.</p>
+
+ <p>When testing a code, try running it with a variety of optimizations, and with
+ all the back-ends: CBE, llc, and lli.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="llvm_ir">Extend the LLVM intermediate representation</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ol>
+ <li>Add support for platform-independent prefetch support. The GCC <a
+ href="http://gcc.gnu.org/projects/prefetch.html">prefetch project</a> page
+ has a good survey of the prefetching capabilities of a variety of modern
+ processors.</li>
+
+ </ol>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="misc_imp">Miscellaneous Improvements</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ol>
+ <li>Someone needs to look into getting the <tt>ranlib</tt> tool to index LLVM
+ bytecode files, so that linking in .a files is not hideously slow. They
+ would also then have to implement the reader for this index in
+ <tt>gccld</tt>.</li>
+
+ <li>Rework the PassManager to be more flexible</li>
+
+ <li>Some transformations and analyses only work on reducible flow graphs. It
+ would be nice to have a transformation which could be "required" by these passes
+ which makes irreducible graphs reducible. This can easily be accomplished
+ through code duplication. See <a
+ href="http://citeseer.nj.nec.com/janssen97making.html">Making Graphs Reducible
+ with Controlled Node Splitting</a> and perhaps <a
+ href="http://doi.acm.org/10.1145/262004.262005">Nesting of Reducible and
+ Irreducible Loops</a>.</li>
+
+ </ol>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="new">Adding new capabilities to LLVM</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Sometimes creating new things is more fun that improving existing things.
+ These projects tend to be more involved and perhaps require more work, but can
+ also be very rewarding.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="pointeranalysis">Pointer and Alias Analysis</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>We have a <a href="AliasAnalysis.html">strong base for development</a> of
+ both pointer analysis based optimizations as well as pointer analyses
+ themselves. It seems natural to want to take advantage of this...</p>
+
+ <ol>
+ <li>Implement a flow-sensitive context-sensitive alias analysis algorithm<br>
+ - Pick one of the somewhat efficient algorithms, but strive for maximum
+ precision</li>
+
+ <li>Implement a flow-sensitive context-insensitive alias analysis algorithm<br>
+ - Just an efficient local algorithm perhaps?</li>
+
+ <li>Implement an interface to update analyses in response to common code motion
+ transformations</li>
+
+ <li>Implement alias-analysis-based optimizations:
+ <ul>
+ <li>Dead store elimination</li>
+ <li>...</li>
+ </ul></li>
+ </ol>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="profileguided">Profile Guided Optimization</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>We now have a unified infrastructure for writing profile-guided
+ transformations, which will work either at offline-compile-time or in the JIT,
+ but we don't have many transformations. We would welcome new profile-guided
+ transformations as well as improvements to the current profiling system.
+ </p>
+
+ <p>Ideas for profile guided transformations:</p>
+
+ <ol>
+ <li>Superblock formation (with many optimizations)</li>
+ <li>Loop unrolling/peeling</li>
+ <li>Profile directed inlining</li>
+ <li>Code layout</li>
+ <li>...</li>
+ </ol>
+
+ <p>Improvements to the existing support:</p>
+
+ <ol>
+ <li>The current block and edge profiling code that gets inserted is very simple
+ and inefficient. Through the use of control-dependence information, many fewer
+ counters could be inserted into the code. Also, if the execution count of a
+ loop is known to be a compile-time or runtime constant, all of the counters in
+ the loop could be avoided.</li>
+
+ <li>You could implement one of the "static profiling" algorithms which analyze a
+ piece of code an make educated guesses about the relative execution frequencies
+ of various parts of the code.</li>
+
+ <li>You could add path profiling support, or adapt the existing LLVM path
+ profiling code to work with the generic profiling interfaces.</li>
+ </ol>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="xforms">New Transformations and Analyses</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ol>
+ <li>Implement a Dependence Analysis Infrastructure<br>
+ - Design some way to represent and query dep analysis</li>
+ <li>Implement a strength reduction pass</li>
+ <li>Value range propagation pass</li>
+ <li>Implement an unswitching pass</li>
+ <li>Write a loop unroller, with a simple heuristic for when to unroll</li>
+ </ol>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_section">
+ <a name="x86be">X86 Back-end Improvements</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ol>
+ <li>Implement a global register allocator</li>
+ <li>Implement a better instruction selector</li>
+ <li>Implement support for the "switch" instruction without requiring the
+ lower-switches pass.</li>
+ </ol>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_section">
+ <a name="misc_new">Miscellaneous Additions</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ol>
+ <li>Write a new frontend for some language (Java? OCaml? Forth?)</li>
+ <li>Write a new backend for a target (IA64? MIPS? MMIX?)</li>
+ <li>Random test vector generator: Use a C grammar to generate random C code;
+ run it through llvm-gcc, then run a random set of passes on it using opt.
+ Try to crash opt. When opt crashes, use bugpoint to reduce the test case and
+ mail the result to yourself. Repeat ad infinitum.</li>
+ <li>Design a simple, recognizable logo.</li>
+ </ol>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+
+ <hr>
+ <div class="doc_footer">
+ <address><a href="mailto:sabre at nondot.org">Chris Lattner</a></address>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </div>
+
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/ProgrammersManual.html
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>LLVM Programmer's Manual</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">
+ LLVM Programmer's Manual
+ </div>
+
+ <ol>
+ <li><a href="#introduction">Introduction</a></li>
+ <li><a href="#general">General Information</a>
+ <ul>
+ <li><a href="#stl">The C++ Standard Template Library</a><!--
+ <li>The <tt>-time-passes</tt> option
+ <li>How to use the LLVM Makefile system
+ <li>How to write a regression test
+ --> </li>
+ </ul>
+ </li>
+ <li><a href="#apis">Important and useful LLVM APIs</a>
+ <ul>
+ <li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
+ and <tt>dyn_cast<></tt> templates</a> </li>
+ <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt>
+ option</a>
+ <ul>
+ <li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
+ and the <tt>-debug-only</tt> option</a> </li>
+ </ul>
+ </li>
+ <li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
+ option</a><!--
+ <li>The <tt>InstVisitor</tt> template
+ <li>The general graph API
+ --> </li>
+ </ul>
+ </li>
+ <li><a href="#common">Helpful Hints for Common Operations</a>
+ <ul>
+ <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
+ <ul>
+ <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
+ in a <tt>Function</tt></a> </li>
+ <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
+ in a <tt>BasicBlock</tt></a> </li>
+ <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
+ in a <tt>Function</tt></a> </li>
+ <li><a href="#iterate_convert">Turning an iterator into a
+ class pointer</a> </li>
+ <li><a href="#iterate_complex">Finding call sites: a more
+ complex example</a> </li>
+ <li><a href="#calls_and_invokes">Treating calls and invokes
+ the same way</a> </li>
+ <li><a href="#iterate_chains">Iterating over def-use &
+ use-def chains</a> </li>
+ </ul>
+ </li>
+ <li><a href="#simplechanges">Making simple changes</a>
+ <ul>
+ <li><a href="#schanges_creating">Creating and inserting new
+ <tt>Instruction</tt>s</a> </li>
+ <li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
+ <li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
+ with another <tt>Value</tt></a> </li>
+ </ul>
+ <!--
+ <li>Working with the Control Flow Graph
+ <ul>
+ <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
+ <li>
+ <li>
+ </ul>
+ --> </li>
+ </ul>
+ </li>
+ <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
+ <ul>
+ <li><a href="#Value">The <tt>Value</tt> class</a>
+ <ul>
+ <li><a href="#User">The <tt>User</tt> class</a>
+ <ul>
+ <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
+ <ul>
+ <li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt>
+ class</a></li>
+ </ul></li>
+ <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
+ <ul>
+ <li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
+ <li><a href="#Function">The <tt>Function</tt> class</a></li>
+ <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt>
+ class</a></li>
+ </ul></li>
+ <li><a href="#Module">The <tt>Module</tt> class</a></li>
+ <li><a href="#Constant">The <tt>Constant</tt> class</a>
+ <ul>
+ <li> <br>
+ </li>
+ <li> <br>
+ </li>
+ </ul>
+ </li>
+ </ul>
+ </li>
+ <li><a href="#Type">The <tt>Type</tt> class</a> </li>
+ <li><a href="#Argument">The <tt>Argument</tt> class</a> </li>
+ </ul>
+ </li>
+ <li>The <tt>SymbolTable</tt> class </li>
+ <li>The <tt>ilist</tt> and <tt>iplist</tt> classes
+ <ul>
+ <li>Creating, inserting, moving and deleting from LLVM lists </li>
+ </ul>
+ </li>
+ <li>Important iterator invalidation semantics to be aware of </li>
+ </ul>
+ </li>
+ </ol>
+
+ <div class="doc_text">
+ <p><b>Written by <a href="mailto:sabre at nondot.org">Chris Lattner</a>,
+ <a href="mailto:dhurjati at cs.uiuc.edu">Dinakar Dhurjati</a>, and <a
+ href="mailto:jstanley at cs.uiuc.edu">Joel Stanley</a></b></p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="introduction">Introduction </a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This document is meant to highlight some of the important classes and
+ interfaces available in the LLVM source-base. This manual is not
+ intended to explain what LLVM is, how it works, and what LLVM code looks
+ like. It assumes that you know the basics of LLVM and are interested
+ in writing transformations or otherwise analyzing or manipulating the
+ code.</p>
+
+ <p>This document should get you oriented so that you can find your
+ way in the continuously growing source code that makes up the LLVM
+ infrastructure. Note that this manual is not intended to serve as a
+ replacement for reading the source code, so if you think there should be
+ a method in one of these classes to do something, but it's not listed,
+ check the source. Links to the <a href="/doxygen/">doxygen</a> sources
+ are provided to make this as easy as possible.</p>
+
+ <p>The first section of this document describes general information that is
+ useful to know when working in the LLVM infrastructure, and the second describes
+ the Core LLVM classes. In the future this manual will be extended with
+ information describing how to use extension libraries, such as dominator
+ information, CFG traversal routines, and useful utilities like the <tt><a
+ href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="general">General Information</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This section contains general information that is useful if you are working
+ in the LLVM source-base, but that isn't specific to any particular API.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="stl">The C++ Standard Template Library</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>LLVM makes heavy use of the C++ Standard Template Library (STL),
+ perhaps much more than you are used to, or have seen before. Because of
+ this, you might want to do a little background reading in the
+ techniques used and capabilities of the library. There are many good
+ pages that discuss the STL, and several books on the subject that you
+ can get, so it will not be discussed in this document.</p>
+
+ <p>Here are some useful links:</p>
+
+ <ol>
+
+ <li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
+ reference</a> - an excellent reference for the STL and other parts of the
+ standard C++ library.</li>
+
+ <li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
+ O'Reilly book in the making. It has a decent <a
+ href="http://www.tempest-sw.com/cpp/ch13-libref.html">Standard Library
+ Reference</a> that rivals Dinkumware's, and is actually free until the book is
+ published.</li>
+
+ <li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
+ Questions</a></li>
+
+ <li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
+ Contains a useful <a
+ href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
+ STL</a>.</li>
+
+ <li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
+ Page</a></li>
+
+ </ol>
+
+ <p>You are also encouraged to take a look at the <a
+ href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
+ to write maintainable code more than where to put your curly braces.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="stl">Other useful references</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>LLVM is currently using CVS as its source versioning system. You may find
+ this reference handy:</p>
+
+ <ol>
+ <li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
+ Branch and Tag Primer</a></li>
+ </ol>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="apis">Important and useful LLVM APIs</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Here we highlight some LLVM APIs that are generally useful and good to
+ know about when writing transformations.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The LLVM source-base makes extensive use of a custom form of RTTI.
+ These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
+ operator, but they don't have some drawbacks (primarily stemming from
+ the fact that <tt>dynamic_cast<></tt> only works on classes that
+ have a v-table). Because they are used so often, you must know what they
+ do and how they work. All of these templates are defined in the <a
+ href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
+ file (note that you very rarely have to include this file directly).</p>
+
+ <dl>
+ <dt><tt>isa<></tt>: </dt>
+
+ <dd>The <tt>isa<></tt> operator works exactly like the Java
+ "<tt>instanceof</tt>" operator. It returns true or false depending on whether
+ a reference or pointer points to an instance of the specified class. This can
+ be very useful for constraint checking of various sorts (example below).</dd>
+
+ <dt><tt>cast<></tt>: </dt>
+
+ <dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
+ converts a pointer or reference from a base class to a derived cast, causing
+ an assertion failure if it is not really an instance of the right type. This
+ should be used in cases where you have some information that makes you believe
+ that something is of the right type. An example of the <tt>isa<></tt>
+ and <tt>cast<></tt> template is:
+
+ <pre>static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const
+ Loop *L) {<br> if (isa<<a href="#Constant">Constant</a>>(V) || isa<<a
+ href="#Argument">Argument</a>>(V) || isa<<a
+ href="#GlobalValue">GlobalValue</a>>(V))<br> return true;<br><br> <i>//
+ Otherwise, it must be an instruction...</i><br> return
+ !L->contains(cast<<a
+ href="#Instruction">Instruction</a>>(V)->getParent());<br></pre>
+
+ <p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
+ by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
+ operator.</p>
+
+ </dd>
+
+ <dt><tt>dyn_cast<></tt>:</dt>
+
+ <dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
+ checks to see if the operand is of the specified type, and if so, returns a
+ pointer to it (this operator does not work with references). If the operand is
+ not of the correct type, a null pointer is returned. Thus, this works very
+ much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
+ same circumstances. Typically, the <tt>dyn_cast<></tt> operator is used
+ in an <tt>if</tt> statement or some other flow control statement like this:
+
+ <pre> if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a
+ href="#AllocationInst">AllocationInst</a>>(Val)) {<br> ...<br> }<br></pre>
+
+ <p> This form of the <tt>if</tt> statement effectively combines together a
+ call to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
+ statement, which is very convenient.</p>
+
+ <p> Another common example is:</p>
+
+ <pre> <i>// Loop over all of the phi nodes in a basic block</i><br>
+ BasicBlock::iterator BBI = BB->begin();<br> for (; <a
+ href="#PhiNode">PHINode</a> *PN = dyn_cast<<a
+ href="#PHINode">PHINode</a>>(BBI); ++BBI)<br> cerr << *PN;<br></pre>
+
+ <p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
+ <tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
+ In particular you should not use big chained <tt>if/then/else</tt> blocks to
+ check for lots of different variants of classes. If you find yourself
+ wanting to do this, it is much cleaner and more efficient to use the
+ InstVisitor class to dispatch over the instruction type directly.</p>
+
+ </dd>
+
+ <dt><tt>cast_or_null<></tt>: </dt>
+
+ <dd>The <tt>cast_or_null<></tt> operator works just like the
+ <tt>cast<></tt> operator, except that it allows for a null pointer as
+ an argument (which it then propagates). This can sometimes be useful,
+ allowing you to combine several null checks into one.</dd>
+
+ <dt><tt>dyn_cast_or_null<></tt>: </dt>
+
+ <dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
+ <tt>dyn_cast<></tt> operator, except that it allows for a null pointer
+ as an argument (which it then propagates). This can sometimes be useful,
+ allowing you to combine several null checks into one.</dd>
+
+ </dl>
+
+ <p>These five templates can be used with any classes, whether they have a
+ v-table or not. To add support for these templates, you simply need to add
+ <tt>classof</tt> static methods to the class you are interested casting
+ to. Describing this is currently outside the scope of this document, but there
+ are lots of examples in the LLVM source base.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Often when working on your pass you will put a bunch of debugging printouts
+ and other code into your pass. After you get it working, you want to remove
+ it... but you may need it again in the future (to work out new bugs that you run
+ across).</p>
+
+ <p> Naturally, because of this, you don't want to delete the debug printouts,
+ but you don't want them to always be noisy. A standard compromise is to comment
+ them out, allowing you to enable them if you need them in the future.</p>
+
+ <p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
+ file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
+ this problem. Basically, you can put arbitrary code into the argument of the
+ <tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
+ tool) is run with the '<tt>-debug</tt>' command line argument:</p>
+
+ <pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
+
+ <p>Then you can run your pass like this:</p>
+
+ <pre> $ opt < a.bc > /dev/null -mypass<br> <no output><br> $ opt < a.bc > /dev/null -mypass -debug<br> I am here!<br> $<br></pre>
+
+ <p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
+ to not have to create "yet another" command line option for the debug output for
+ your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
+ so they do not cause a performance impact at all (for the same reason, they
+ should also not contain side-effects!).</p>
+
+ <p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
+ enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
+ "<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
+ program hasn't been started yet, you can always just run it with
+ <tt>-debug</tt>.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
+ the <tt>-debug-only</tt> option</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
+ just turns on <b>too much</b> information (such as when working on the code
+ generator). If you want to enable debug information with more fine-grained
+ control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
+ option as follows:</p>
+
+ <pre> ...<br> DEBUG(std::cerr << "No debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "foo"<br> DEBUG(std::cerr << "'foo' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "bar"<br> DEBUG(std::cerr << "'bar' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE ""<br> DEBUG(std::cerr << "No debug type (2)\n");<br> ...<br></pre>
+
+ <p>Then you can run your pass like this:</p>
+
+ <pre> $ opt < a.bc > /dev/null -mypass<br> <no output><br> $ opt < a.bc > /dev/null -mypass -debug<br> No debug type<br> 'foo' debug type<br> 'bar' debug type<br> No debug type (2)<br> $ opt < a.bc > /dev/null -mypass -debug-only=foo<br> 'foo' debug type<br> $ opt < a.bc > /dev/null -mypass -debug-only=bar<br> 'bar' debug type<br> $<br></pre>
+
+ <p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
+ a file, to specify the debug type for the entire module (if you do this before
+ you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
+ <tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
+ "bar", because there is no system in place to ensure that names do not
+ conflict. If two different modules use the same string, they will all be turned
+ on when the name is specified. This allows, for example, all debug information
+ for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
+ even if the source lives in multiple files.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
+ option</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The "<tt><a
+ href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
+ provides a template named <tt>Statistic</tt> that is used as a unified way to
+ keep track of what the LLVM compiler is doing and how effective various
+ optimizations are. It is useful to see what optimizations are contributing to
+ making a particular program run faster.</p>
+
+ <p>Often you may run your pass on some big program, and you're interested to see
+ how many times it makes a certain transformation. Although you can do this with
+ hand inspection, or some ad-hoc method, this is a real pain and not very useful
+ for big programs. Using the <tt>Statistic</tt> template makes it very easy to
+ keep track of this information, and the calculated information is presented in a
+ uniform manner with the rest of the passes being executed.</p>
+
+ <p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
+ it are as follows:</p>
+
+ <ol>
+ <li>Define your statistic like this:
+ <pre>static Statistic<> NumXForms("mypassname", "The # of times I did stuff");<br></pre>
+
+ <p>The <tt>Statistic</tt> template can emulate just about any data-type,
+ but if you do not specify a template argument, it defaults to acting like
+ an unsigned int counter (this is usually what you want).</p></li>
+
+ <li>Whenever you make a transformation, bump the counter:
+ <pre> ++NumXForms; // I did stuff<br></pre>
+ </li>
+ </ol>
+
+ <p>That's all you have to do. To get '<tt>opt</tt>' to print out the
+ statistics gathered, use the '<tt>-stats</tt>' option:</p>
+
+ <pre> $ opt -stats -mypassname < program.bc > /dev/null<br> ... statistic output ...<br></pre>
+
+ <p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
+ suite, it gives a report that looks like this:</p>
+
+ <pre> 7646 bytecodewriter - Number of normal instructions<br> 725 bytecodewriter - Number of oversized instructions<br> 129996 bytecodewriter - Number of bytecode bytes written<br> 2817 raise - Number of insts DCEd or constprop'd<br> 3213 raise - Number of cast-of-self removed<br> 5046 raise - Number of expression trees converted<br> 75 raise - Number of other getelementptr's formed<br> 138 raise - Number of load/store peepholes<br> 42 deadtypeelim - Number of unused typenames removed from symtab<br> 392 funcresolve - Number of varargs functions resolved<br> 27 globaldce - Number of global variables removed<br> 2 adce - Number of basic blocks removed<br> 134 cee - Number of branches revectored<br> 49 cee - Number of setcc instruction eliminated<br> 532 gcse - Number of loads removed<br> 2919 gcse - Number!
of instructions removed<br> 86 indvars - Number of canonical indvars added<br> 87 indvars - Number of aux indvars removed<br> 25 instcombine - Number of dead inst eliminate<br> 434 instcombine - Number of insts combined<br> 248 licm - Number of load insts hoisted<br> 1298 licm - Number of insts hoisted to a loop pre-header<br> 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)<br> 75 mem2reg - Number of alloca's promoted<br> 1444 cfgsimplify - Number of blocks simplified<br></pre>
+
+ <p>Obviously, with so many optimizations, having a unified framework for this
+ stuff is very nice. Making your pass fit well into the framework makes it more
+ maintainable and useful.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="common">Helpful Hints for Common Operations</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This section describes how to perform some very simple transformations of
+ LLVM code. This is meant to give examples of common idioms used, showing the
+ practical side of LLVM transformations. <p> Because this is a "how-to" section,
+ you should also read about the main classes that you will be working with. The
+ <a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
+ and descriptions of the main classes that you should know about.</p>
+
+ </div>
+
+ <!-- NOTE: this section should be heavy on example code -->
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="inspection">Basic Inspection and Traversal Routines</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The LLVM compiler infrastructure have many different data structures that may
+ be traversed. Following the example of the C++ standard template library, the
+ techniques used to traverse these various data structures are all basically the
+ same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
+ method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
+ function returns an iterator pointing to one past the last valid element of the
+ sequence, and there is some <tt>XXXiterator</tt> data type that is common
+ between the two operations.</p>
+
+ <p>Because the pattern for iteration is common across many different aspects of
+ the program representation, the standard template library algorithms may be used
+ on them, and it is easier to remember how to iterate. First we show a few common
+ examples of the data structures that need to be traversed. Other data
+ structures are traversed in very similar ways.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="subsubsection">
+ <a name="iterate_function">Iterating over the </a><a
+ href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
+ href="#Function"><tt>Function</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>It's quite common to have a <tt>Function</tt> instance that you'd like to
+ transform in some way; in particular, you'd like to manipulate its
+ <tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
+ the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
+ an example that prints the name of a <tt>BasicBlock</tt> and the number of
+ <tt>Instruction</tt>s it contains:</p>
+
+ <pre> // func is a pointer to a Function instance<br> for (Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {<br><br> // print out the name of the basic block if it has one, and then the<br> // number of instructions that it contains<br><br> cerr << "Basic block (name=" << i->getName() << ") has " <br> << i->size() << " instructions.\n";<br> }<br></pre>
+
+ <p>Note that i can be used as if it were a pointer for the purposes of
+ invoking member functions of the <tt>Instruction</tt> class. This is
+ because the indirection operator is overloaded for the iterator
+ classes. In the above code, the expression <tt>i->size()</tt> is
+ exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="subsubsection">
+ <a name="iterate_basicblock">Iterating over the </a><a
+ href="#Instruction"><tt>Instruction</tt></a>s in a <a
+ href="#BasicBlock"><tt>BasicBlock</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
+ easy to iterate over the individual instructions that make up
+ <tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
+ a <tt>BasicBlock</tt>:</p>
+
+ <pre> // blk is a pointer to a BasicBlock instance<br> for (BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)<br> // the next statement works since operator<<(ostream&,...) <br> // is overloaded for Instruction&<br> cerr << *i << "\n";<br></pre>
+
+ <p>However, this isn't really the best way to print out the contents of a
+ <tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
+ anything you'll care about, you could have just invoked the print routine on the
+ basic block itself: <tt>cerr << *blk << "\n";</tt>.</p>
+
+ <p>Note that currently operator<< is implemented for <tt>Value*</tt>, so
+ it will print out the contents of the pointer, instead of the pointer value you
+ might expect. This is a deprecated interface that will be removed in the
+ future, so it's best not to depend on it. To print out the pointer value for
+ now, you must cast to <tt>void*</tt>.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="subsubsection">
+ <a name="iterate_institer">Iterating over the </a><a
+ href="#Instruction"><tt>Instruction</tt></a>s in a <a
+ href="#Function"><tt>Function</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
+ <tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
+ <tt>InstIterator</tt> should be used instead. You'll need to include <a
+ href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
+ and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
+ small example that shows how to dump all instructions in a function to stderr
+ (<b>Note:</b> Dereferencing an <tt>InstIterator</tt> yields an
+ <tt>Instruction*</tt>, <i>not</i> an <tt>Instruction&</tt>!):</p>
+
+ <pre>#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"<br>...<br>// Suppose F is a ptr to a function<br>for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)<br> cerr << **i << "\n";<br></pre>
+ Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
+ worklist with its initial contents. For example, if you wanted to
+ initialize a worklist to contain all instructions in a <tt>Function</tt>
+ F, all you would need to do is something like:
+ <pre>std::set<Instruction*> worklist;<br>worklist.insert(inst_begin(F), inst_end(F));<br></pre>
+
+ <p>The STL set <tt>worklist</tt> would now contain all instructions in the
+ <tt>Function</tt> pointed to by F.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="iterate_convert">Turning an iterator into a class pointer (and
+ vice-versa)</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Sometimes, it'll be useful to grab a reference (or pointer) to a class
+ instance when all you've got at hand is an iterator. Well, extracting
+ a reference or a pointer from an iterator is very straightforward.
+ Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
+ is a <tt>BasicBlock::const_iterator</tt>:</p>
+
+ <pre> Instruction& inst = *i; // grab reference to instruction reference<br> Instruction* pinst = &*i; // grab pointer to instruction reference<br> const Instruction& inst = *j;<br></pre>
+
+ <p>However, the iterators you'll be working with in the LLVM framework are
+ special: they will automatically convert to a ptr-to-instance type whenever they
+ need to. Instead of dereferencing the iterator and then taking the address of
+ the result, you can simply assign the iterator to the proper pointer type and
+ you get the dereference and address-of operation as a result of the assignment
+ (behind the scenes, this is a result of overloading casting mechanisms). Thus
+ the last line of the last example,</p>
+
+ <pre>Instruction* pinst = &*i;</pre>
+
+ <p>is semantically equivalent to</p>
+
+ <pre>Instruction* pinst = i;</pre>
+
+ <p>It's also possible to turn a class pointer into the corresponding iterator.
+ Usually, this conversion is quite inexpensive. The following code snippet
+ illustrates use of the conversion constructors provided by LLVM iterators. By
+ using these, you can explicitly grab the iterator of something without actually
+ obtaining it via iteration over some structure:</p>
+
+ <pre>void printNextInstruction(Instruction* inst) {<br> BasicBlock::iterator it(inst);<br> ++it; // after this line, it refers to the instruction after *inst.<br> if (it != inst->getParent()->end()) cerr << *it << "\n";<br>}<br></pre>
+
+ <p>Of course, this example is strictly pedagogical, because it'd be much
+ better to explicitly grab the next instruction directly from inst.</p>
+
+ </div>
+
+ <!--_______________________________________________________________________-->
+ <div class="doc_subsubsection">
+ <a name="iterate_complex">Finding call sites: a slightly more complex
+ example</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Say that you're writing a FunctionPass and would like to count all the
+ locations in the entire module (that is, across every <tt>Function</tt>) where a
+ certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
+ learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
+ much more straightforward manner, but this example will allow us to explore how
+ you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
+ is what we want to do:</p>
+
+ <pre>initialize callCounter to zero<br>for each Function f in the Module<br> for each BasicBlock b in f<br> for each Instruction i in b<br> if (i is a CallInst and calls the given function)<br> increment callCounter<br></pre>
+
+ <p>And the actual code is (remember, since we're writing a
+ <tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
+ override the <tt>runOnFunction</tt> method...):</p>
+
+ <pre>Function* targetFunc = ...;<br><br>class OurFunctionPass : public FunctionPass {<br> public:<br> OurFunctionPass(): callCounter(0) { }<br><br> virtual runOnFunction(Function& F) {<br> for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {<br> for (BasicBlock::iterator i = b->begin(); ie = b->end(); i != ie; ++i) {<br> if (<a
+ href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
+ href="#CallInst">CallInst</a>>(&*i)) {<br> // we know we've encountered a call instruction, so we<br> // need to determine if it's a call to the<br> // function pointed to by m_func or not.<br> <br> if (callInst->getCalledFunction() == targetFunc)<br> ++callCounter;<br> }<br> }<br> }<br> <br> private:<br> unsigned callCounter;<br>};<br></pre>
+
+ </div>
+
+ <!--_______________________________________________________________________-->
+ <div class="doc_subsubsection">
+ <a name="calls_and_invokes">Treating calls and invokes the same way</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>You may have noticed that the previous example was a bit oversimplified in
+ that it did not deal with call sites generated by 'invoke' instructions. In
+ this, and in other situations, you may find that you want to treat
+ <tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
+ most-specific common base class is <tt>Instruction</tt>, which includes lots of
+ less closely-related things. For these cases, LLVM provides a handy wrapper
+ class called <a
+ href="http://llvm.cs.uiuc.edu/doxygen/classCallSite.html"><tt>CallSite
+ </tt></a>. It is essentially a wrapper around an <tt>Instruction</tt> pointer,
+ with some methods that provide functionality common to <tt>CallInst</tt>s and
+ <tt>InvokeInst</tt>s.</p>
+
+ <p>This class is supposed to have "value semantics". So it should be passed by
+ value, not by reference; it should not be dynamically allocated or deallocated
+ using <tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently
+ copyable, assignable and constructable, with costs equivalents to that of a bare
+ pointer. (You will notice, if you look at its definition, that it has only a
+ single data member.)</p>
+
+ </div>
+
+ <!--_______________________________________________________________________-->
+ <div class="doc_subsubsection">
+ <a name="iterate_chains">Iterating over def-use & use-def chains</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Frequently, we might have an instance of the <a
+ href="/doxygen/classValue.html">Value Class</a> and we want to determine which
+ <tt>User</tt>s use the <tt>Value</tt>. The list of all <tt>User</tt>s of a
+ particular <tt>Value</tt> is called a <i>def-use</i> chain. For example, let's
+ say we have a <tt>Function*</tt> named <tt>F</tt> to a particular function
+ <tt>foo</tt>. Finding all of the instructions that <i>use</i> <tt>foo</tt> is as
+ simple as iterating over the <i>def-use</i> chain of <tt>F</tt>:</p>
+
+ <pre>Function* F = ...;<br><br>for (Value::use_iterator i = F->use_begin(), e = F->use_end(); i != e; ++i) {<br> if (Instruction *Inst = dyn_cast<Instruction>(*i)) {<br> cerr << "F is used in instruction:\n";<br> cerr << *Inst << "\n";<br> }<br>}<br></pre>
+
+ <p>Alternately, it's common to have an instance of the <a
+ href="/doxygen/classUser.html">User Class</a> and need to know what
+ <tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
+ <tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
+ <tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
+ all of the values that a particular instruction uses (that is, the operands of
+ the particular <tt>Instruction</tt>):</p>
+
+ <pre>Instruction* pi = ...;<br><br>for (User::op_iterator i = pi->op_begin(), e = pi->op_end(); i != e; ++i) {<br> Value* v = *i;<br> ...<br>}<br></pre>
+
+ <!--
+ def-use chains ("finding all users of"): Value::use_begin/use_end
+ use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
+ -->
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="simplechanges">Making simple changes</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>There are some primitive transformation operations present in the LLVM
+ infrastructure that are worth knowing about. When performing
+ transformations, it's fairly common to manipulate the contents of basic
+ blocks. This section describes some of the common methods for doing so
+ and gives example code.</p>
+
+ </div>
+
+ <!--_______________________________________________________________________-->
+ <div class="doc_subsubsection">
+ <a name="schanges_creating">Creating and inserting new
+ <tt>Instruction</tt>s</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><i>Instantiating Instructions</i></p>
+
+ <p>Creation of <tt>Instruction</tt>s is straightforward: simply call the
+ constructor for the kind of instruction to instantiate and provide the necessary
+ parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
+ (const-ptr-to) <tt>Type</tt>. Thus:</p>
+
+ <pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
+
+ <p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
+ one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
+ subclass is likely to have varying default parameters which change the semantics
+ of the instruction, so refer to the <a
+ href="/doxygen/classInstruction.html">doxygen documentation for the subclass of
+ Instruction</a> that you're interested in instantiating.</p>
+
+ <p><i>Naming values</i></p>
+
+ <p>It is very useful to name the values of instructions when you're able to, as
+ this facilitates the debugging of your transformations. If you end up looking
+ at generated LLVM machine code, you definitely want to have logical names
+ associated with the results of instructions! By supplying a value for the
+ <tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
+ associate a logical name with the result of the instruction's execution at
+ runtime. For example, say that I'm writing a transformation that dynamically
+ allocates space for an integer on the stack, and that integer is going to be
+ used as some kind of index by some other code. To accomplish this, I place an
+ <tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
+ <tt>Function</tt>, and I'm intending to use it within the same
+ <tt>Function</tt>. I might do:</p>
+
+ <pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
+
+ <p>where <tt>indexLoc</tt> is now the logical name of the instruction's
+ execution value, which is a pointer to an integer on the runtime stack.</p>
+
+ <p><i>Inserting instructions</i></p>
+
+ <p>There are essentially two ways to insert an <tt>Instruction</tt>
+ into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
+
+ <ul>
+ <li>Insertion into an explicit instruction list
+
+ <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
+ <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
+ before <tt>*pi</tt>, we do the following: </p>
+
+ <pre> BasicBlock *pb = ...;<br> Instruction *pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb<br></pre></li>
+
+ <li>Insertion into an implicit instruction list
+
+ <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
+ are implicitly associated with an existing instruction list: the instruction
+ list of the enclosing basic block. Thus, we could have accomplished the same
+ thing as the above code without being given a <tt>BasicBlock</tt> by doing:
+ </p>
+
+ <pre> Instruction *pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
+
+ <p>In fact, this sequence of steps occurs so frequently that the
+ <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
+ constructors which take (as a default parameter) a pointer to an
+ <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
+ precede. That is, <tt>Instruction</tt> constructors are capable of
+ inserting the newly-created instance into the <tt>BasicBlock</tt> of a
+ provided instruction, immediately before that instruction. Using an
+ <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
+ parameter, the above code becomes:</p>
+
+ <pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
+
+ <p>which is much cleaner, especially if you're creating a lot of
+ instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
+ </ul>
+
+ </div>
+
+ <!--_______________________________________________________________________-->
+ <div class="doc_subsubsection">
+ <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Deleting an instruction from an existing sequence of instructions that form a
+ <a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straightforward. First,
+ you must have a pointer to the instruction that you wish to delete. Second, you
+ need to obtain the pointer to that instruction's basic block. You use the
+ pointer to the basic block to get its list of instructions and then use the
+ erase function to remove your instruction. For example:</p>
+
+ <pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
+ href="#BasicBlock">BasicBlock</a> *BB = I->getParent();<br> BB->getInstList().erase(I);<br></pre>
+
+ </div>
+
+ <!--_______________________________________________________________________-->
+ <div class="doc_subsubsection">
+ <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
+ <tt>Value</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><i>Replacing individual instructions</i></p>
+
+ <p>Including "<a href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h</a>"
+ permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
+ and <tt>ReplaceInstWithInst</tt>.</p>
+
+ <h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
+
+ <ul>
+ <li><tt>ReplaceInstWithValue</tt>
+
+ <p>This function replaces all uses (within a basic block) of a given
+ instruction with a value, and then removes the original instruction. The
+ following example illustrates the replacement of the result of a particular
+ <tt>AllocaInst</tt> that allocates memory for a single integer with an null
+ pointer to an integer.</p>
+
+ <pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
+
+ <li><tt>ReplaceInstWithInst</tt>
+
+ <p>This function replaces a particular instruction with another
+ instruction. The following example illustrates the replacement of one
+ <tt>AllocaInst</tt> with another.</p>
+
+ <pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithInst(instToReplace->getParent()->getInstList(), ii,<br> new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));<br></pre></li>
+ </ul>
+
+ <p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
+
+ <p>You can use <tt>Value::replaceAllUsesWith</tt> and
+ <tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
+ doxygen documentation for the <a href="/doxygen/classValue.html">Value Class</a>
+ and <a href="/doxygen/classUser.html">User Class</a>, respectively, for more
+ information.</p>
+
+ <!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
+ include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
+ ReplaceInstWithValue, ReplaceInstWithInst -->
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>The Core LLVM classes are the primary means of representing the program
+ being inspected or transformed. The core LLVM classes are defined in
+ header files in the <tt>include/llvm/</tt> directory, and implemented in
+ the <tt>lib/VMCore</tt> directory.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="Value">The <tt>Value</tt> class</a>
+ </div>
+
+ <div>
+
+ <p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
+ <br>
+ doxygen info: <a href="/doxygen/classValue.html">Value Class</a></p>
+
+ <p>The <tt>Value</tt> class is the most important class in the LLVM Source
+ base. It represents a typed value that may be used (among other things) as an
+ operand to an instruction. There are many different types of <tt>Value</tt>s,
+ such as <a href="#Constant"><tt>Constant</tt></a>s,<a
+ href="#Argument"><tt>Argument</tt></a>s. Even <a
+ href="#Instruction"><tt>Instruction</tt></a>s and <a
+ href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
+
+ <p>A particular <tt>Value</tt> may be used many times in the LLVM representation
+ for a program. For example, an incoming argument to a function (represented
+ with an instance of the <a href="#Argument">Argument</a> class) is "used" by
+ every instruction in the function that references the argument. To keep track
+ of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
+ href="#User"><tt>User</tt></a>s that is using it (the <a
+ href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
+ graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
+ def-use information in the program, and is accessible through the <tt>use_</tt>*
+ methods, shown below.</p>
+
+ <p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
+ and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
+ method. In addition, all LLVM values can be named. The "name" of the
+ <tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
+
+ <pre> %<b>foo</b> = add int 1, 2<br></pre>
+
+ <p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
+ that the name of any value may be missing (an empty string), so names should
+ <b>ONLY</b> be used for debugging (making the source code easier to read,
+ debugging printouts), they should not be used to keep track of values or map
+ between them. For this purpose, use a <tt>std::map</tt> of pointers to the
+ <tt>Value</tt> itself instead.</p>
+
+ <p>One important aspect of LLVM is that there is no distinction between an SSA
+ variable and the operation that produces it. Because of this, any reference to
+ the value produced by an instruction (or the value available as an incoming
+ argument, for example) is represented as a direct pointer to the class that
+ represents this value. Although this may take some getting used to, it
+ simplifies the representation and makes it easier to manipulate.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
+ use-list<br>
+ <tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
+ the use-list<br>
+ <tt>unsigned use_size()</tt> - Returns the number of users of the
+ value.<br>
+ <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
+ <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
+ the use-list.<br>
+ <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
+ use-list.<br>
+ <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
+ element in the list.
+ <p> These methods are the interface to access the def-use
+ information in LLVM. As with all other iterators in LLVM, the naming
+ conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
+ </li>
+ <li><tt><a href="#Type">Type</a> *getType() const</tt>
+ <p>This method returns the Type of the Value.</p>
+ </li>
+ <li><tt>bool hasName() const</tt><br>
+ <tt>std::string getName() const</tt><br>
+ <tt>void setName(const std::string &Name)</tt>
+ <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
+ be aware of the <a href="#nameWarning">precaution above</a>.</p>
+ </li>
+ <li><tt>void replaceAllUsesWith(Value *V)</tt>
+
+ <p>This method traverses the use list of a <tt>Value</tt> changing all <a
+ href="#User"><tt>User</tt>s</a> of the current value to refer to
+ "<tt>V</tt>" instead. For example, if you detect that an instruction always
+ produces a constant value (for example through constant folding), you can
+ replace all uses of the instruction with the constant like this:</p>
+
+ <pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="User">The <tt>User</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ <tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
+ doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
+ Superclass: <a href="#Value"><tt>Value</tt></a></p>
+
+ <p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
+ refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
+ that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
+ referring to. The <tt>User</tt> class itself is a subclass of
+ <tt>Value</tt>.</p>
+
+ <p>The operands of a <tt>User</tt> point directly to the LLVM <a
+ href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
+ Single Assignment (SSA) form, there can only be one definition referred to,
+ allowing this direct connection. This connection provides the use-def
+ information in LLVM.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>User</tt> class exposes the operand list in two ways: through
+ an index access interface and through an iterator based interface.</p>
+
+ <ul>
+ <li><tt>Value *getOperand(unsigned i)</tt><br>
+ <tt>unsigned getNumOperands()</tt>
+ <p> These two methods expose the operands of the <tt>User</tt> in a
+ convenient form for direct access.</p></li>
+
+ <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
+ list<br>
+ <tt>User::op_const_iterator</tt> <tt>use_iterator op_begin()</tt> -
+ Get an iterator to the start of the operand list.<br>
+ <tt>use_iterator op_end()</tt> - Get an iterator to the end of the
+ operand list.
+ <p> Together, these methods make up the iterator based interface to
+ the operands of a <tt>User</tt>.</p></li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="Instruction">The <tt>Instruction</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><tt>#include "</tt><tt><a
+ href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
+ doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
+ Superclasses: <a href="#User"><tt>User</tt></a>, <a
+ href="#Value"><tt>Value</tt></a></p>
+
+ <p>The <tt>Instruction</tt> class is the common base class for all LLVM
+ instructions. It provides only a few methods, but is a very commonly used
+ class. The primary data tracked by the <tt>Instruction</tt> class itself is the
+ opcode (instruction type) and the parent <a
+ href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
+ into. To represent a specific type of instruction, one of many subclasses of
+ <tt>Instruction</tt> are used.</p>
+
+ <p> Because the <tt>Instruction</tt> class subclasses the <a
+ href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
+ way as for other <a href="#User"><tt>User</tt></a>s (with the
+ <tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
+ <tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
+ the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
+ file contains some meta-data about the various different types of instructions
+ in LLVM. It describes the enum values that are used as opcodes (for example
+ <tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
+ concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
+ example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
+ href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
+ this file confuses doxygen, so these enum values don't show up correctly in the
+ <a href="/doxygen/classInstruction.html">doxygen output</a>.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
+ class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
+ <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
+ this <tt>Instruction</tt> is embedded into.</p></li>
+ <li><tt>bool mayWriteToMemory()</tt>
+ <p>Returns true if the instruction writes to memory, i.e. it is a
+ <tt>call</tt>,<tt>free</tt>,<tt>invoke</tt>, or <tt>store</tt>.</p></li>
+ <li><tt>unsigned getOpcode()</tt>
+ <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
+ <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
+ <p>Returns another instance of the specified instruction, identical
+ in all ways to the original except that the instruction has no parent
+ (ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
+ and it has no name</p></li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><tt>#include "<a href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
+ doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
+ Superclass: <a href="#Value"><tt>Value</tt></a></p>
+
+ <p>This class represents a single entry multiple exit section of the code,
+ commonly known as a basic block by the compiler community. The
+ <tt>BasicBlock</tt> class maintains a list of <a
+ href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
+ Matching the language definition, the last element of this list of instructions
+ is always a terminator instruction (a subclass of the <a
+ href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
+
+ <p>In addition to tracking the list of instructions that make up the block, the
+ <tt>BasicBlock</tt> class also keeps track of the <a
+ href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
+
+ <p>Note that <tt>BasicBlock</tt>s themselves are <a
+ href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
+ like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
+ <tt>label</tt>.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
+ class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
+ href="#Function">Function</a> *Parent = 0)</tt>
+ <p>The <tt>BasicBlock</tt> constructor is used to create new basic
+ blocks for insertion into a function. The constructor optionally takes
+ a name for the new block, and a <a href="#Function"><tt>Function</tt></a>
+ to insert it into. If the <tt>Parent</tt> parameter is specified, the
+ new <tt>BasicBlock</tt> is automatically inserted at the end of the
+ specified <a href="#Function"><tt>Function</tt></a>, if not specified,
+ the BasicBlock must be manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p>
+ </li>
+ <li><tt>BasicBlock::iterator</tt> - Typedef for instruction list
+ iterator<br>
+ <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
+ <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,<tt>size()</tt>,<tt>empty()</tt>,<tt>rbegin()</tt>,<tt>rend()
+ - </tt>STL style functions for accessing the instruction list.
+ <p> These methods and typedefs are forwarding functions that have
+ the same semantics as the standard library methods of the same names.
+ These methods expose the underlying instruction list of a basic block in
+ a way that is easy to manipulate. To get the full complement of
+ container operations (including operations to update the list), you must
+ use the <tt>getInstList()</tt> method.</p></li>
+ <li><tt>BasicBlock::InstListType &getInstList()</tt>
+ <p> This method is used to get access to the underlying container
+ that actually holds the Instructions. This method must be used when
+ there isn't a forwarding function in the <tt>BasicBlock</tt> class for
+ the operation that you would like to perform. Because there are no
+ forwarding functions for "updating" operations, you need to use this if
+ you want to update the contents of a <tt>BasicBlock</tt>.</p></li>
+ <li><tt><a href="#Function">Function</a> *getParent()</tt>
+ <p> Returns a pointer to <a href="#Function"><tt>Function</tt></a>
+ the block is embedded into, or a null pointer if it is homeless.</p></li>
+ <li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
+ <p> Returns a pointer to the terminator instruction that appears at
+ the end of the <tt>BasicBlock</tt>. If there is no terminator
+ instruction, or if the last instruction in the block is not a
+ terminator, then a null pointer is returned.</p></li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><tt>#include "<a
+ href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
+ doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
+ Superclasses: <a href="#User"><tt>User</tt></a>, <a
+ href="#Value"><tt>Value</tt></a></p>
+
+ <p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
+ href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
+ visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
+ Because they are visible at global scope, they are also subject to linking with
+ other globals defined in different translation units. To control the linking
+ process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
+ <tt>GlobalValue</tt>s know whether they have internal or external linkage, as
+ defined by the <tt>LinkageTypes</tt> enumerator.</p>
+
+ <p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
+ <tt>static</tt> in C), it is not visible to code outside the current translation
+ unit, and does not participate in linking. If it has external linkage, it is
+ visible to external code, and does participate in linking. In addition to
+ linkage information, <tt>GlobalValue</tt>s keep track of which <a
+ href="#Module"><tt>Module</tt></a> they are currently part of.</p>
+
+ <p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
+ by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
+ global is always a pointer to its contents. It is important to remember this
+ when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
+ be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
+ subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
+ int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
+ the address of the first element of this array and the value of the
+ <tt>GlobalVariable</tt> are the same, they have different types. The
+ <tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
+ is <tt>int.</tt> Because of this, accessing a global value requires you to
+ dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
+ can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
+ Language Reference Manual</a>.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
+ class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li><tt>bool hasInternalLinkage() const</tt><br>
+ <tt>bool hasExternalLinkage() const</tt><br>
+ <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
+ <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
+ <p> </p>
+ </li>
+ <li><tt><a href="#Module">Module</a> *getParent()</tt>
+ <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
+ GlobalValue is currently embedded into.</p></li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="Function">The <tt>Function</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><tt>#include "<a
+ href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
+ info: <a href="/doxygen/classFunction.html">Function Class</a><br> Superclasses:
+ <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
+ href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
+
+ <p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
+ actually one of the more complex classes in the LLVM heirarchy because it must
+ keep track of a large amount of data. The <tt>Function</tt> class keeps track
+ of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
+ href="#Argument"><tt>Argument</tt></a>s, and a <a
+ href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
+
+ <p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
+ commonly used part of <tt>Function</tt> objects. The list imposes an implicit
+ ordering of the blocks in the function, which indicate how the code will be
+ layed out by the backend. Additionally, the first <a
+ href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
+ <tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
+ block. There are no implicit exit nodes, and in fact there may be multiple exit
+ nodes from a single <tt>Function</tt>. If the <a
+ href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
+ the <tt>Function</tt> is actually a function declaration: the actual body of the
+ function hasn't been linked in yet.</p>
+
+ <p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
+ <tt>Function</tt> class also keeps track of the list of formal <a
+ href="#Argument"><tt>Argument</tt></a>s that the function receives. This
+ container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
+ nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
+ the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
+
+ <p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
+ LLVM feature that is only used when you have to look up a value by name. Aside
+ from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
+ internally to make sure that there are not conflicts between the names of <a
+ href="#Instruction"><tt>Instruction</tt></a>s, <a
+ href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
+ href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_Function">Important Public Members of the <tt>Function</tt>
+ class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
+ *Ty, bool isInternal, const std::string &N = "", Module* Parent = 0)</tt>
+
+ <p>Constructor used when you need to create new <tt>Function</tt>s to add
+ the the program. The constructor must specify the type of the function to
+ create and whether or not it should start out with internal or external
+ linkage. The <a href="#FunctionType"><tt>FunctionType</tt></a> argument
+ specifies the formal arguments and return value for the function. The same
+ <a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
+ create multiple functions. The <tt>Parent</tt> argument specifies the Module
+ in which the function is defined. If this argument is provided, the function
+ will automatically be inserted into that module's list of
+ functions.</p></li>
+
+ <li><tt>bool isExternal()</tt>
+
+ <p>Return whether or not the <tt>Function</tt> has a body defined. If the
+ function is "external", it does not have a body, and thus must be resolved
+ by linking with a function defined in a different translation unit.</p></li>
+
+ <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
+ <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
+
+ <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
+ <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
+
+ <p>These are forwarding methods that make it easy to access the contents of
+ a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
+ list.</p></li>
+
+ <li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
+
+ <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
+ is necessary to use when you need to update the list or perform a complex
+ action that doesn't have a forwarding method.</p></li>
+
+ <li><tt>Function::aiterator</tt> - Typedef for the argument list
+ iterator<br>
+ <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
+
+ <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
+ <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt>
+
+ <p>These are forwarding methods that make it easy to access the contents of
+ a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
+ list.</p></li>
+
+ <li><tt>Function::ArgumentListType &getArgumentList()</tt>
+
+ <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
+ necessary to use when you need to update the list or perform a complex
+ action that doesn't have a forwarding method.</p></li>
+
+ <li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
+
+ <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
+ function. Because the entry block for the function is always the first
+ block, this returns the first block of the <tt>Function</tt>.</p></li>
+
+ <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
+ <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
+
+ <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
+ <tt>Function</tt> and returns the return type of the function, or the <a
+ href="#FunctionType"><tt>FunctionType</tt></a> of the actual
+ function.</p></li>
+
+ <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
+
+ <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
+ for this <tt>Function</tt>.</p></li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><tt>#include "<a
+ href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
+ <br>
+ doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable
+ Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
+ href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
+
+ <p>Global variables are represented with the (suprise suprise)
+ <tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
+ subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
+ always referenced by their address (global values must live in memory, so their
+ "name" refers to their address). See <a
+ href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
+ may have an initial value (which must be a <a
+ href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
+ may be marked as "constant" themselves (indicating that their contents never
+ change at runtime).</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_GlobalVariable">Important Public Members of the
+ <tt>GlobalVariable</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
+ isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
+ *Initializer = 0, const std::string &Name = "", Module* Parent = 0)</tt>
+
+ <p>Create a new global variable of the specified type. If
+ <tt>isConstant</tt> is true then the global variable will be marked as
+ unchanging for the program. The Linkage parameter specifies the type of
+ linkage (internal, external, weak, linkonce, appending) for the variable. If
+ the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage, then
+ the resultant global variable will have internal linkage. AppendingLinkage
+ concatenates together all instances (in different translation units) of the
+ variable into a single variable but is only applicable to arrays. See
+ the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
+ further details on linkage types. Optionally an initializer, a name, and the
+ module to put the variable into may be specified for the global variable as
+ well.</p></li>
+
+ <li><tt>bool isConstant() const</tt>
+
+ <p>Returns true if this is a global variable that is known not to
+ be modified at runtime.</p></li>
+
+ <li><tt>bool hasInitializer()</tt>
+
+ <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
+
+ <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
+
+ <p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
+ to call this method if there is no initializer.</p></li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="Module">The <tt>Module</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><tt>#include "<a
+ href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
+ <a href="/doxygen/classModule.html">Module Class</a></p>
+
+ <p>The <tt>Module</tt> class represents the top level structure present in LLVM
+ programs. An LLVM module is effectively either a translation unit of the
+ original program or a combination of several translation units merged by the
+ linker. The <tt>Module</tt> class keeps track of a list of <a
+ href="#Function"><tt>Function</tt></a>s, a list of <a
+ href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
+ href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
+ helpful member functions that try to make common operations easy.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li><tt>Module::Module(std::string name = "")</tt></li>
+ </ul>
+
+ <p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
+ provide a name for it (probably based on the name of the translation unit).</p>
+
+ <ul>
+ <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
+ <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
+
+ <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
+ <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
+
+ <p>These are forwarding methods that make it easy to access the contents of
+ a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
+ list.</p></li>
+
+ <li><tt>Module::FunctionListType &getFunctionList()</tt>
+
+ <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
+ necessary to use when you need to update the list or perform a complex
+ action that doesn't have a forwarding method.</p>
+
+ <p><!-- Global Variable --></p></li>
+ </ul>
+
+ <hr>
+
+ <ul>
+ <li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
+
+ <tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
+
+ <tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
+ <tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt>
+
+ <p> These are forwarding methods that make it easy to access the contents of
+ a <tt>Module</tt> object's <a
+ href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
+
+ <li><tt>Module::GlobalListType &getGlobalList()</tt>
+
+ <p>Returns the list of <a
+ href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
+ use when you need to update the list or perform a complex action that
+ doesn't have a forwarding method.</p>
+
+ <p><!-- Symbol table stuff --> </p></li>
+ </ul>
+
+ <hr>
+
+ <ul>
+ <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
+
+ <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
+ for this <tt>Module</tt>.</p>
+
+ <p><!-- Convenience methods --></p></li>
+ </ul>
+
+ <hr>
+
+ <ul>
+ <li><tt><a href="#Function">Function</a> *getFunction(const std::string
+ &Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
+
+ <p>Look up the specified function in the <tt>Module</tt> <a
+ href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
+ <tt>null</tt>.</p></li>
+
+ <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
+ std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
+
+ <p>Look up the specified function in the <tt>Module</tt> <a
+ href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
+ external declaration for the function and return it.</p></li>
+
+ <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
+
+ <p>If there is at least one entry in the <a
+ href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
+ href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
+ string.</p></li>
+
+ <li><tt>bool addTypeName(const std::string &Name, const <a
+ href="#Type">Type</a> *Ty)</tt>
+
+ <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
+ mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
+ name, true is returned and the <a
+ href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Constant represents a base class for different types of constants. It
+ is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
+ ConstantArray etc for representing the various types of Constants.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_Value">Important Public Methods</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li><tt>bool isConstantExpr()</tt>: Returns true if it is a
+ ConstantExpr
+ <hr> Important Subclasses of Constant
+ <p> </p>
+ <ul>
+ <li>ConstantSInt : This subclass of Constant represents a signed
+ integer constant.
+ <ul>
+ <li><tt>int64_t getValue() const</tt>: Returns the underlying value of
+ this constant. </li>
+ </ul>
+ </li>
+ <li>ConstantUInt : This class represents an unsigned integer.
+ <ul>
+ <li><tt>uint64_t getValue() const</tt>: Returns the underlying value
+ of this constant. </li>
+ </ul>
+ </li>
+ <li>ConstantFP : This class represents a floating point constant.
+ <ul>
+ <li><tt>double getValue() const</tt>: Returns the underlying value of
+ this constant. </li>
+ </ul>
+ </li>
+ <li>ConstantBool : This represents a boolean constant.
+ <ul>
+ <li><tt>bool getValue() const</tt>: Returns the underlying value of
+ this constant. </li>
+ </ul>
+ </li>
+ <li>ConstantArray : This represents a constant array.
+ <ul>
+ <li><tt>const std::vector<Use> &getValues() const</tt>:
+ Returns a Vecotr of component constants that makeup this array. </li>
+ </ul>
+ </li>
+ <li>ConstantStruct : This represents a constant struct.
+ <ul>
+ <li><tt>const std::vector<Use> &getValues() const</tt>:
+ Returns a Vecotr of component constants that makeup this array. </li>
+ </ul>
+ </li>
+ <li>ConstantPointerRef : This represents a constant pointer value
+ that is initialized to point to a global value, which lies at a
+ constant fixed address.
+ <ul>
+ <li><tt>GlobalValue *getValue()</tt>: Returns the global
+ value to which this pointer is pointing to. </li>
+ </ul>
+ </li>
+ </ul>
+ </li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="Type">The <tt>Type</tt> class and Derived Types</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Type as noted earlier is also a subclass of a Value class. Any primitive
+ type (like int, short etc) in LLVM is an instance of Type Class. All other
+ types are instances of subclasses of type like FunctionType, ArrayType
+ etc. DerivedType is the interface for all such dervied types including
+ FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
+ be recursive (StructType). There exists exactly one instance of any type
+ structure at a time. This allows using pointer equality of Type *s for comparing
+ types.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="m_Value">Important Public Methods</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+
+ <li><tt>PrimitiveID getPrimitiveID() const</tt>: Returns the base type of the
+ type.</li>
+
+ <li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
+ is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
+ not true for Float and Double. </li>
+
+ <li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
+ unsigned. This is not quite the complement of isSigned... nonnumeric types
+ return false as they do with isSigned. This returns true for UByteTy,
+ UShortTy, UIntTy, and ULongTy. </li>
+
+ <li><tt>bool isInteger() const</tt>: Equilivent to isSigned() || isUnsigned(),
+ but with only a single virtual function invocation.</li>
+
+ <li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
+ type, which is either Bool type or one of the Integer types.</li>
+
+ <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
+ floating point types.</li>
+
+ <li><tt>bool isRecursive() const</tt>: Returns rue if the type graph contains
+ a cycle.</li>
+
+ <li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
+ this type can be converted to 'Ty' without any reinterpretation of bits. For
+ example, uint to int.</li>
+
+ <li><tt>bool isPrimitiveType() const</tt>: Returns true if it is a primitive
+ type.</li>
+
+ <li><tt>bool isDerivedType() const</tt>: Returns true if it is a derived
+ type.</li>
+
+ <li><tt>const Type * getContainedType (unsigned i) const</tt>: This method is
+ used to implement the type iterator. For derived types, this returns the types
+ 'contained' in the derived type, returning 0 when 'i' becomes invalid. This
+ allows the user to iterate over the types in a struct, for example, really
+ easily.</li>
+
+ <li><tt>unsigned getNumContainedTypes() const</tt>: Return the number of types
+ in the derived type.
+
+ <hr>
+ <p>Derived Types</p>
+
+ <ul>
+ <li>SequentialType : This is subclassed by ArrayType and PointerType
+ <ul>
+ <li><tt>const Type * getElementType() const</tt>: Returns the type of
+ each of the elements in the sequential type. </li>
+ </ul>
+ </li>
+ <li>ArrayType : This is a subclass of SequentialType and defines
+ interface for array types.
+ <ul>
+ <li><tt>unsigned getNumElements() const</tt>: Returns the number of
+ elements in the array. </li>
+ </ul>
+ </li>
+ <li>PointerType : Subclass of SequentialType for pointer types. </li>
+ <li>StructType : subclass of DerivedTypes for struct types </li>
+ <li>FunctionType : subclass of DerivedTypes for function types.
+ <ul>
+ <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
+ function</li>
+ <li><tt> const Type * getReturnType() const</tt>: Returns the
+ return type of the function.</li>
+ <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
+ the type of the ith parameter.</li>
+ <li><tt> const unsigned getNumParams() const</tt>: Returns the
+ number of formal parameters.</li>
+ </ul>
+ </li>
+ </ul>
+ </li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="Argument">The <tt>Argument</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>This subclass of Value defines the interface for incoming formal
+ arguments to a function. A Function maitanis a list of its formal
+ arguments. An argument has a pointer to the parent Function.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <hr>
+ <address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
+
+ <a href="mailto:dhurjati at cs.uiuc.edu">Dinakar Dhurjati</a> and
+ <a href="mailto:sabre at nondot.org">Chris Lattner</a><br>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </address>
+
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/Projects.html
diff -c /dev/null llvm-www/releases/1.2/docs/Projects.html:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/Projects.html Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,391 ----
+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
+ <html>
+ <head>
+ <title>Creating an LLVM Project</title>
+ </head>
+
+ <body bgcolor=white>
+
+ <center><h1>Creating an LLVM Project<br></h1></center>
+
+ <!--===============================================================-->
+ <h2><a name="a">Overview</a><hr></h2>
+ <!--===============================================================-->
+
+ The LLVM build system is designed to facilitate the building of third party
+ projects that use LLVM header files, libraries, and tools. In order to use
+ these facilities, a Makefile from a project must do the following things:
+
+ <ol>
+ <li>Set environment variables.
+ <p>
+ There are several environment variables that a Makefile needs to set to
+ use the LLVM build system:
+ <dl compact>
+ <dt>LLVM_SRC_ROOT
+ <dd>
+ The root of the LLVM source tree.
+ <p>
+
+ <dt>LLVM_OBJ_ROOT
+ <dd>
+ The root of the LLVM object tree.
+ <p>
+
+ <dt>BUILD_SRC_ROOT
+ <dd>
+ The root of the project's source tree.
+ <p>
+
+ <dt>BUILD_OBJ_ROOT
+ <dd>
+ The root of the project's object tree.
+ <p>
+
+ <dt>BUILD_SRC_DIR
+ <dd>
+ The directory containing the current source to be compiled.
+ <p>
+
+ <dt>BUILD_OBJ_DIR
+ <dd>
+ The directory where the current source will place the new object
+ files. This should always be the current directory.
+ <p>
+
+ <dt>LEVEL
+ <dd>
+ The relative path from the current directory to the root of the
+ object tree.
+ <p>
+ </dl>
+
+ <li>Include the LLVM Makefile.config from $(LLVM_OBJ_ROOT).
+ <p>
+
+ <li>Include the LLVM Makefile.rules from $(LLVM_SRC_ROOT).
+ </ol>
+
+ There are two ways that you can set all of these variables:
+ <ol>
+ <li>
+ You can write your own Makefiles which hard-code these values.
+
+ <li>
+ You can use the pre-made LLVM sample project. This sample project
+ includes Makefiles, a configure script that can be used to configure
+ the location of LLVM, and the ability to support multiple object
+ directories from a single source directory.
+ </ol>
+
+ This document assumes that you will base your project off of the LLVM
+ sample project found in <tt>llvm/projects/sample</tt>. If you want to
+ devise your own build system, studying the sample project and LLVM
+ Makefiles will probably provide enough information on how to write your own
+ Makefiles.
+ <p>
+
+ <!--===============================================================-->
+ <h2><a name="a">Create a Project from the Sample Project</a><hr></h2>
+ <!--===============================================================-->
+
+ Follow these simple steps to start your project:
+
+ <ol>
+ <li>
+ Copy the <tt>llvm/projects/sample</tt> directory to any place
+ of your choosing. You can place it anywhere you like. Rename the
+ directory to match the name of your project.
+ <p>
+
+ <li>
+ Add your source code and Makefiles to your source tree.
+ <p>
+
+ <li>
+ If you want your Makefiles to be configured by the
+ <tt>configure</tt> script, or if you want to support multiple
+ object directories, add your Makefiles to the <tt>configure</tt>
+ script by adding them into the <tt>autoconf/configure.ac</tt> file.
+ The macro <tt>AC_CONFIG_MAKEFILE</tt> will copy a file, unmodified,
+ from the source directory to the object directory.
+
+ <p>
+ After updating <tt>autoconf/configure.ac</tt>, regenerate the
+ configure script with these commands:
+ <p>
+ <tt>
+ cd autoconf<br>
+ autoconf -o ../configure
+ </tt>
+
+ <p>
+
+ You must be using Autoconf version 2.57 or higher.
+ <p>
+
+ <li>
+ Run <tt>configure</tt> in the directory in which you want to place
+ object code. Use the following options to tell your project where it
+ can find LLVM:
+
+ <dl compact>
+ <dt><tt>--with-llvmsrc=<directory></tt>
+ <dd>
+ Tell your project where the LLVM source tree is located.
+ <p>
+ <dt><tt>--with-llvmobj=<directory></tt>
+ <dd>
+ Tell your project where the LLVM object tree is located.
+ </dl>
+ </ol>
+
+ That's it! Now all you have to do is type <tt>gmake</tt> in the root of
+ your object directory, and your project should build.
+
+ <!--===============================================================-->
+ <h2><a name="Source Tree Layout">Source Tree Layout</a><hr></h2>
+ <!--===============================================================-->
+
+ In order to use the LLVM build system, you will want to organize your
+ source code so that it can benefit from the build system's features.
+ Mainly, you want your source tree layout to look similar to the LLVM
+ source tree layout. The best way to do this is to just copy the
+ project tree from <tt>llvm/projects/sample</tt> and modify it to meet
+ your needs, but you can certainly add to it if you want.
+
+ Underneath your top level directory, you should have the following
+ directories:
+
+ <dl compact>
+ <dt><b>lib</b>
+ <dd>
+ This subdirectory should contain all of your library source
+ code. For each library that you build, you will have one
+ directory in <b>lib</b> that will contain that library's source
+ code.
+
+ <p>
+ Libraries can be object files, archives, or dynamic libraries.
+ The <b>lib</b> directory is just a convenient place for libraries
+ as it places them all in a directory from which they can be linked
+ later.
+
+ <dt><b>include</b>
+ <dd>
+ This subdirectory should contain any header files that are
+ global to your project. By global, we mean that they are used
+ by more than one library or executable of your project.
+ <p>
+ By placing your header files in <b>include</b>, they will be
+ found automatically by the LLVM build system. For example, if
+ you have a file <b>include/jazz/note.h</b>, then your source
+ files can include it simply with <b>#include "jazz/note.h"</b>.
+
+ <dt><b>tools</b>
+ <dd>
+ This subdirectory should contain all of your source
+ code for executables. For each program that you build, you
+ will have one directory in <b>tools</b> that will contain that
+ program's source code.
+ <p>
+
+ <dt><b>test</b>
+ <dd>
+ This subdirectory should contain tests that verify that your code
+ works correctly. Automated tests are especially useful.
+ <p>
+ Currently, the LLVM build system provides little support for tests,
+ although some exists. Expanded support for tests will hopefully
+ occur in the future. In the meantime, the LLVM system does provide the
+ following:
+ <ul>
+ <li>
+ LLVM provides several QMTest test classes that can be used to
+ create tests. They can be found in
+ <tt>llvm/test/QMTest/llvm.py</tt>. These test classes perform a
+ variety of functions, including code optimization tests, assembly
+ tests, and code analysis tests. The Makefile in
+ <tt>llvm/test</tt> provides the QMTest context needed by LLVM test
+ classes.
+ <p>
+
+ <li>
+ The LLVM source tree provides benchmarks and programs which are
+ known to compile with the LLVM GCC front ends. You can use these
+ programs to test your code, gather statistics information, and
+ compare it to the current LLVM performance statistics. These
+ programs are found in the <tt>llvm/test/Programs</tt> directory.
+ <p>
+ Currently, there is no way to hook your tests directly into the
+ <tt>llvm/test/Programs</tt> testing harness. You will simply
+ need to find a way to use the source provided within that directory
+ on your own.
+ </ul>
+ </dl>
+
+ Typically, you will want to build your <b>lib</b> directory first
+ followed by your <b>tools</b> directory.
+
+ <!--===============================================================-->
+ <h2><a name="Makefile Variables">Writing LLVM Style Makefiles</a><hr></h2>
+ <!--===============================================================-->
+ The LLVM build system provides a convenient way to build libraries and
+ executables. Most of your project Makefiles will only need to define a few
+ variables. Below is a list of the variables one can set and what they can
+ do:
+
+ <h3> Required Variables </h3>
+ <dl compact>
+ <dt>LEVEL
+ <dd>
+ This variable is the relative path from this Makefile to the
+ top directory of your project's source code. For example, if
+ your source code is in /tmp/src, then the Makefile in
+ /tmp/src/jump/high would set LEVEL to "../..".
+ </dl>
+
+ <h3> Variables for Building Subdirectories</h3>
+ <dl compact>
+ <dt>DIRS
+ <dd>
+ This is a space separated list of subdirectories that should be
+ built. They will be built, one at a time, in the order
+ specified.
+ <p>
+
+ <dt>PARALLEL_DIRS
+ <dd>
+ This is a list of directories that can be built in parallel.
+ These will be built after the directories in DIRS have been
+ built.
+ <p>
+
+ <dt>OPTIONAL_DIRS
+ <dd>
+ This is a list of directories that can be built if they exist,
+ but will not cause an error if they do not exist. They are
+ built serially in the order in which they are listed.
+ </dl>
+
+ <h3> Variables for Building Libraries</h3>
+ <dl compact>
+ <dt>LIBRARYNAME
+ <dd>
+ This variable contains the base name of the library that will
+ be built. For example, to build a library named
+ <tt>libsample.a</tt>, LIBRARYNAME should be set to
+ <tt>sample</tt>.
+ <p>
+
+ <dt>BUILD_ARCHIVE
+ <dd>
+ By default, a library is a <tt>.o</tt> file that is linked
+ directly into a program. To build an archive (also known as
+ a static library), set the BUILD_ARCHIVE variable.
+ <p>
+
+ <dt>SHARED_LIBRARY
+ <dd>
+ If SHARED_LIBRARY is defined in your Makefile, a shared
+ (or dynamic) library will be built.
+ </dl>
+
+ <h3> Variables for Building Programs</h3>
+ <dl compact>
+ <dt>TOOLNAME
+ <dd>
+ This variable contains the name of the program that will
+ be built. For example, to build an executable named
+ <tt>sample</tt>, TOOLNAME should be set to <tt>sample</tt>.
+ <p>
+
+ <dt>USEDLIBS
+ <dd>
+ This variable holds a space separated list of libraries that
+ should be linked into the program. These libraries must either
+ be LLVM libraries or libraries that come from your <b>lib</b>
+ directory. The libraries must be specified by their base name.
+ For example, to link libsample.a, you would set USEDLIBS to
+ <tt>sample</tt>.
+ <p>
+ Note that this works only for statically linked libraries.
+ <p>
+
+ <dt>LIBS
+ <dd>
+ To link dynamic libraries, add <tt>-l<library base name></tt> to
+ the LIBS variable. The LLVM build system will look in the same places
+ for dynamic libraries as it does for static libraries.
+ <p>
+ For example, to link <tt>libsample.so</tt>, you would have the
+ following line in your <tt>Makefile</tt>:
+ <p>
+ <tt>
+ LIBS+=-lsample
+ </tt>
+ </dl>
+
+ <h3> Miscellaneous Variables</h3>
+ <dl compact>
+ <dt>ExtraSource
+ <dd>
+ This variable contains a space separated list of extra source
+ files that need to be built. It is useful for including the
+ output of Lex and Yacc programs.
+ <p>
+
+ <dt>CFLAGS
+ <dt>CPPFLAGS
+ <dd>
+ This variable can be used to add options to the C and C++
+ compiler, respectively. It is typically used to add options
+ that tell the compiler the location of additional directories
+ to search for header files.
+ <p>
+ It is highly suggested that you append to CFLAGS and CPPFLAGS as
+ opposed to overwriting them. The master Makefiles may already
+ have useful options in them that you may not want to overwrite.
+ <p>
+ </dl>
+
+ <!--===============================================================-->
+ <h2><a name="objcode">Placement of Object Code</a><hr></h2>
+ <!--===============================================================-->
+
+ The final location of built libraries and executables will depend upon
+ whether you do a Debug, Release, or Profile build.
+
+ <dl compact>
+ <dt>Libraries
+ <dd>
+ All libraries (static and dynamic) will be stored in
+ BUILD_OBJ_ROOT/lib/<type>, where type is <tt>Debug</tt>,
+ <tt>Release</tt>, or <tt>Profile</tt> for a debug, optimized, or
+ profiled build, respectively.
+ <p>
+
+ <dt>Executables
+ <dd>
+ All executables will be stored in BUILD_OBJ_ROOT/lib/<type>,
+ where type is <tt>Debug</tt>, <tt>Release</tt>, or <tt>Profile</tt> for
+ a debug, optimized, or profiled build, respectively.
+ </dl>
+
+ <!--===============================================================-->
+ <h2><a name="help">Further Help</a><hr></h2>
+ <!--===============================================================-->
+
+ If you have any questions or need any help creating an LLVM project,
+ the LLVM team would be more than happy to help. You can always post your
+ questions to the <a
+ href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developers
+ Mailing List</a>.
+
+ <hr>
+ <address><a href="mailto:criswell at uiuc.edu">John Criswell</a></address><br>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/RegisterAllocatorInfo.txt
diff -c /dev/null llvm-www/releases/1.2/docs/RegisterAllocatorInfo.txt:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/RegisterAllocatorInfo.txt Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,197 ----
+ ===================
+ Register Allocation
+ ===================
+
+
+ 1. Introduction
+ ===============
+
+ Purpose: This file contains implementation information about register
+ allocation.
+ Author : Ruchira Sasanka
+ Date : Dec 8, 2001
+
+
+ 2. Entry Point
+ ==============
+ class PhyRegAlloc (PhyRegAlloc.h) is the main class for the register
+ allocation. PhyRegAlloc::allocateRegisters() starts the register allocation
+ and contains the major steps for register allocation.
+
+ 2. Usage
+ ========
+ Register allocation must be done as:
+
+ MethodLiveVarInfo LVI(*MethodI ); // compute LV info
+ LVI.analyze();
+
+ TargetMachine &target = .... // target description
+
+
+ PhyRegAlloc PRA(*MethodI, target, &LVI); // allocate regs
+ PRA.allocateRegisters();
+
+
+ 4. Input and Preconditions
+ ==========================
+ Register allocation is done using machine instructions. The constructor
+ to the class takes a pointer to a method, a target machine description and
+ a live variable information for the method.
+
+ The preconditions are:
+
+ 1. Instruction selection is complete (i.e., machine instructions are
+ generated) for the method before the live variable analysis
+
+ 2. Phi elimination is complete.
+
+
+ 5. Assumptions
+ ==============
+
+ All variables (llvm Values) are defined before they are used. However, a
+ constant may not be defined in the machine instruction stream if it can be
+ used as an immediate value within a machine instruction. However, register
+ allocation does not have to worry about immediate constants since they
+ do not require registers.
+
+ Since an llvm Value has a list of uses associated, it is sufficient to
+ record only the defs in a Live Range.
+
+
+
+
+ 6. Overall Design
+ =================
+ There are sperate reigster classes - e.g., Int, Float,
+ IntConditionCode, FloatConditionCode register classes for Sparc.
+
+ Registerallocation consists of the following main steps:
+
+ 1. Construct Live-ranges & Suggest colors (machine specific) if required
+ 2. Create Interference graphs
+ 3. Coalescing live ranges
+ 4. Color all live ranges in each RegClass using graph coloring algo
+ 5. Insert additional (machine specific) code for calls/returns/incoming args
+ 6. Update instruction stream and insert spill code
+
+ All the above methods are called from PhyRegAlloc::allocateRegisters().
+
+ All steps above except step 5 and suggesting colors in step 1 are indepenedent
+ of a particular target architecture. Targer independent code is availble in
+ ../lib/CodeGen/RegAlloc. Target specific code for Sparc is available in
+ ../lib/Target/Sparc.
+
+
+ 6.1. Construct Live-ranges & Suggest colors (machine specific) if required
+ --------------------------------------------------------------------------
+ Live range construction is done using machine instructions. Since there must
+ be at least one definition for each variable in the machine instruction, we
+ consider only definitions in creating live ranges. After live range
+ construction is complete, there is a live range for all variables defined in
+ the instruction stream. Note however that, live ranges are not constructed for
+ constants which are not defined in the instruction stream.
+
+ A LiveRange is a set of Values (only defs) in that live range. Live range
+ construction is done in combination for all register classes. All the live
+ ranges for a method are entered to a LiveRangeMap which can be accessed using
+ any Value in the LiveRange.
+
+ After live ranges have been constructed, we call machine specific code to
+ suggest colors for speical live ranges. For instance, incoming args, call args,
+ return values must be placed in special registers for most architectures. By
+ suggesting colors for such special live ranges before we do the actual register
+ allocation using graph coloring, the graph coloring can try its best to assign
+ the required color for such special live ranges. This will reduce unnecessary
+ copy instructions needed to move values to special registers. However, there
+ is no guarantee that a live range will receive its suggested color. If the
+ live range does not receive the suggested color, we have to insert explicit
+ copy instructions to move the value into requred registers and its done in
+ step 5 above.
+
+ See LiveRange.h, LiveRangeInfo.h (and LiveRange.cpp, LiveRangeInfo.cpp) for
+ algorithms and details. See SparcRegInfo.cpp for suggesting colors for
+ incoming/call arguments and return values.
+
+
+ 6.2. Create Interference graphs
+ -------------------------------
+ Once live ranges are constructed, we can build interference graphs for each
+ register class. Though each register class must have a separate interference
+ graph, building all interference graphs is performed in one pass. Also, the
+ adjacency list for each live range is built in this phase. Consequently, each
+ register class has an interference graph (which is a bit matrix) and each
+ LiveRange has an adjacency list to record its neighbors. Live variable info
+ is used for finding the interferences.
+
+ See IGNode.h, InterferenceGraph.h (and IGNode.h, InterferenceGraph.h) for
+ data structures and PhyRegAlloc::createIGNodeListsAndIGs() for the starting
+ point for interference graph construction.
+
+
+ 6.3. Coalescing live ranges
+ ---------------------------
+ We coalesce live ranges to reduce the number of live ranges.
+
+ See LiveRangeInfo.h (and LiveRangeInfo.cpp). The entire algorithm for
+ coalesing is given in LiveRangeInfo::coalesceLRs().
+
+
+ 6.4. Color all live ranges in each RegClass using graph coloring algo
+ ---------------------------------------------------------------------
+ Each register class is colored separately using the graph coloring algo. When
+ assigning colors, preference is given to live ranges with suggested colors
+ so that if such a live range receives a color (i.e., not spilled), then
+ we try to assign the color suggested for that live range. When this phase
+ is complete it is possible that some live ranges do not have colors (i.e.,
+ those that must be spilled).
+
+
+ 6.5. Insert additional (machine specific) code for calls/returns/incoming args
+ ------------------------------------------------------------------------------
+ This code is machine specific. Currently, the code for Sparc is implemented
+ in SparcRegInfo.cpp. This code is more complex because of the complex
+ requirements of assigning some values to special registers. When a special
+ value as an incoming argument receives a color through the graph coloring
+ alogorithm, we have to make sure that it received the correct color (for
+ instance the first incoming int argument must be colored to %i0 on Sparc). If
+ it didn't receive the correct color, we have to insert instruction to to move
+ the value to the required register. Also, this phase produces the caller
+ saving code. All adition code produced is kept separately until the last
+ phase (see 6.6)
+
+
+ 6.6. Update instruction stream and insert spill code
+ -----------------------------------------------------
+ After we have assigned registers for all values and after we have produced
+ additional code to be inserted before some instructions, we update the
+ machine instruction stream. While we are updating the machine instruction
+ stream, if an instruction referes to a spilled value, we insert spill
+ instructions before/after that instruction. Also, we prepend/append additonal
+ instructions that have been produced for that instruction by the register
+ allocation (e.g., caller saving code)
+
+
+ 7. Furture work
+ ===============
+ If it is necessary to port the register allocator to another architecture
+ than Sparc, only the target specific code in ../lib/Target/Sparc needs to
+ be rewritten. Methods defined in class MachineRegInfo must be provided for
+ the new architecure.
+
+ 7.1 Using ReservedColorList in RegClass
+ ----------------------------------------
+ The register allocator allows reserving a set of registers - i.e. the reserved
+ registers are not used by the register allocator. Currently, there are no
+ reserved registers. It it is necessary to make some registers unavailable to
+ a particular method, this feature will become handy. To do that, the reserved
+ register list must be passed to the register allocator. See PhyRegAlloc.cpp
+
+
+ 7.2 %g registers on Sparc
+ -------------------------
+ Currently, %g registers are not allocated on Sparc. If it is necessary to
+ allocate these %g registers, the enumeration of registers in SparcIntRegClass
+ in SparcRegClassInfo.h must be changed. %g registers can be easily added as
+ volatile registers just by moving them above in the eneumeration - see
+ SparcRegClassInfo.h
Index: llvm-www/releases/1.2/docs/ReleaseNotes.html
diff -c /dev/null llvm-www/releases/1.2/docs/ReleaseNotes.html:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/ReleaseNotes.html Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,671 ----
+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ <title>LLVM 1.2 Release Notes</title>
+ </head>
+ <body>
+
+ <div class="doc_title">
+ LLVM 1.2 Release Notes
+ </div>
+
+ <ol>
+ <li><a href="#intro">Introduction</a></li>
+ <li><a href="#whatsnew">What's New?</a></li>
+ <li><a href="#portability">Portability and Supported Platforms</a></li>
+ <li><a href="#install-instructions">Installation Instructions</a></li>
+ <li><a href="#knownproblems">Known Problems</a>
+ <ul>
+ <li><a href="#experimental">Experimental features included with this release</a>
+ <li><a href="#core">Known problems with the LLVM Core</a>
+ <li><a href="#c-fe">Known problems with the C Front-end</a>
+ <li><a href="#c++-fe">Known problems with the C++ Front-end</a>
+ <li><a href="#x86-be">Known problems with the X86 Back-end</a>
+ <li><a href="#sparc-be">Known problems with the Sparc Back-end</a>
+ <li><a href="#c-be">Known problems with the C back-end</a>
+ </ul></li>
+ <li><a href="#additionalinfo">Additional Information</a></li>
+ </ol>
+
+ <div class="doc_text">
+ <p><b>Written by the <a href="http://llvm.cs.uiuc.edu">LLVM team</a></b><p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="intro">Introduction</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This document contains the release notes for the LLVM compiler
+ infrastructure, release 1.2. Here we describe the status of LLVM, including any
+ known problems and bug fixes from the previous release. The most up-to-date
+ version of this document can be found on the <a
+ href="http://llvm.cs.uiuc.edu/releases/1.2/">LLVM 1.2 web site</a>. If you are
+ not reading this on the LLVM web pages, you should probably go there because
+ this document may be updated after the release.</p>
+
+ <p>For more information about LLVM, including information about potentially more
+ current releases, please check out the <a href="http://llvm.cs.uiuc.edu">main
+ web site</a>. If you have questions or comments, the <a
+ href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
+ list</a> is a good place to send them.</p>
+
+ <p>Note that if you are reading this file from CVS, this document applies
+ to the <i>next</i> release, not the current one. To see the release notes for
+ the current or previous releases, see the <a
+ href="http://llvm.cs.uiuc.edu/releases/">releases page</a>.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="whatsnew">What's New?</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>
+ This is the third public release of the LLVM compiler infrastructure. This
+ release incorporates several <a href="#newfeatures">new features</a> (including
+ exception handling support for the native code generators, the start of a
+ source-level debugger, and profile guided optimizer components), many <a
+ href="#qualityofimp">speedups</a> and <a href="#codequality">code quality</a>
+ improvements, documentation improvements, and a small collection of important <a
+ href="bugfix">bug fixes</a>. Overall, this is our highest quality release to
+ date, and we encourage you to upgrade if you are using LLVM 1.0 or 1.1.
+ </p>
+
+ <p>
+ At this time, LLVM is known to correctly compile and run all C & C++ SPEC
+ CPU2000 benchmarks, the Olden benchmarks, and the Ptrdist benchmarks. It has
+ also been used to compile <b>many</b> other programs. LLVM now also works with
+ a broad variety of C++ programs, though it has still received less testing than
+ the C front-end.
+ </p>
+
+ <!--=========================================================================-->
+ <div class="doc_subsubsection">
+ <a name="newfeatures">This release implements the following new features:</a>
+ </div>
+
+ <ol>
+ <li><a href="SourceLevelDebugging.html">A new LLVM source-level debugger has been started.</a></li>
+ <li>LLVM 1.2 encodes bytecode files for large programs in 10-30% less space.</li>
+ <li>LLVM can now feed profile information back into optimizers for Profile Guided Optimization, includes a simple basic block reordering pass, and supports edge profiling as well as function and block-level profiling.</li>
+ <li>The LLVM JIT lazily initializes global variables, reducing startup time for programs with lots of globals (like C++ programs).</li>
+
+ <li>The build and installation infrastructure in this release is dramatically
+ improved. There is now an <a
+ href="http://llvm.cs.uiuc.edu/PR105"><tt>autoconf/AutoRegen.sh</tt> script</a>
+ that you can run to rebuild the <tt>configure</tt> script and its associated
+ files as well as beta support for "<a
+ href="http://llvm.cs.uiuc.edu/PR208">make</a> <a
+ href="http://llvm.cs.uiuc.edu/PR220">install</a>" and <a
+ href="http://llvm.cs.uiuc.edu/PR203">RPM package generation</a>.</li>
+
+ <li>The "tblgen" tool is <a href="TableGenFundamentals.html">now documented</a>.</li>
+ <li>The target-independent code generator got several improvements:
+ <ul>
+ <li>It can now fold spill code into instructions (on targets that support it).</li>
+ <li>A generic machine code spiller/rewriter was added. It provides an API for
+ global register allocators to eliminate virtual registers and add the
+ appropriate spill code.</li>
+ <li>The represenation of machine code basic blocks is more efficient and has
+ an easier to use interface.</li>
+ </ul>
+ </li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR253">LLVM now no longer depends on the boost library</a>.</li>
+ <li>The X86 backend now generates <b>substantially</b> better native code, and is faster.</li>
+ <li>The C backend has been turned moved from the "llvm-dis" tool to the "llc"
+ tool. You can activate it with "<tt>llc -march=c foo.bc -o foo.c</tt>".</li>
+ <li>LLVM includes a new interprocedural optimization that marks global variables
+ "constant" when they are provably never written to.</li>
+ <li>LLVM now includes a new interprocedural optimization that converts small "by reference" arguments to "by value" arguments, which is often improve the performance of C++ programs substantially.</li>
+ <li>Bugpoint can now do a better job reducing miscompilation problems by
+ reducing programs down to a particular loop nest, instead of just the function
+ being miscompiled.</li>
+ <li>The GCSE and LICM passes can now operate on side-effect-free function calls, for example hoisting calls to "<tt>strlen</tt>" and folding "<tt>cos</tt>" common subexpressions.</li>
+ <li>LLVM has early support for a new <a
+ href="LangRef.html#i_select"><tt>select</tt></a> instruction, though it is
+ currently only supported by the C backend.</li>
+ </ol>
+
+
+ <!--=========================================================================-->
+ <div class="doc_subsubsection">
+ In this release, the following missing features were implemented:
+ </div>
+
+ <ol>
+ <li><a href="http://llvm.cs.uiuc.edu/PR16">Exception handling in the X86
+ & Sparc native code generators</a> is now supported</li>
+ <li>The C/C++ front-end now support the GCC <tt>__builtin_return_address</tt> and <tt>__builtin_frame_address</tt> extensions. These are also supported by the X86 backend and by the C backend.</li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR249">[X86] Missing cast from ULong -> Double, cast FP -> bool and support for -9223372036854775808</a></li>
+ <li>The C/C++ front-end <a href="http://llvm.cs.uiuc.edu/PR273">now supports</a>
+ the "<a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">labels as values</a>" GCC extension, often used to build "threaded interpreters".</a></li>
+
+ </ol>
+
+
+ <!--=========================================================================-->
+ <div class="doc_subsubsection">
+ <a name="qualityofimp">In this release, the following Quality of Implementation issues were fixed:</a>
+ </div>
+
+ <ol>
+
+ <li><a href="http://llvm.cs.uiuc.edu/PR135">JIT should lazily initialize global variables</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR192">[X86] X86 Backend never releases memory for machine code structures</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR196">[vmcore] OpaqueType objects memory leak</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR182">[llvmgcc] C front-end does not compile "extern inline" into linkonce</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR73">Bytecode format inconsistent</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR209">[loadvn/inline/scalarrepl] Slow optimizations with extremely large basic blocks</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR224">[asmparser] Really slow parsing of types with complex upreferences</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR205">[llvmgcc] C front-end does not emit 'zeroinitializer' when possible</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR233">[llvmgcc] Structure copies result in a LOT of code</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR239">LLVM is now much more memory efficient when handling large zero initialized arrays</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR275">[llvmgcc] Local array initializers are expanded into large amounts of code</a></li>
+ </ol>
+
+ <!--=========================================================================-->
+ <div class="doc_subsubsection">
+ In this release, the following build problems were fixed:
+ </div>
+
+ <ol>
+ <li><a href="http://llvm.cs.uiuc.edu/PR210">[build] Makefiles break if C frontend target string has unexpected value</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR214">[build] hard-wired assumption that shared-library extension is ".so"</a></li>
+ <li><A href="http://llvm.cs.uiuc.edu/PR222">make tools-only doesn't make lib/Support</a></li>
+ </ol>
+
+ <!--=========================================================================-->
+ <div class="doc_subsubsection">
+ <a name="codequality">In this release, the following Code Quality issues were fixed:</a>
+ </div>
+
+ <ol>
+ <li><a href="http://llvm.cs.uiuc.edu/PR187">[loopsimplify] Many pointless phi nodes are created</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR237">[x86] wierd stack/frame pointer manipulation</a></li>
+
+ <li>The X86 backend now generate <tt>fchs</tt> to negate floating point numbers,
+ compiles memcpy() into the <tt>rep movs</tt> instruction, and makes much better
+ use of powerful addressing modes and instructions.</li>
+ </ol>
+
+
+ <!--=========================================================================-->
+ <div class="doc_subsubsection">
+ <a name="bugfix">In this release, the following bugs in the previous release were fixed:</a>
+ </div>
+
+ <p>Bugs in the LLVM Core:</p>
+
+ <ol>
+ <li><a href="http://llvm.cs.uiuc.edu/PR179">[licm] LICM promotes volatile memory
+ locations to registers</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR191">[licm] Memory read after free causes
+ infrequent crash</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR194">[indvars] Induction variable
+ canonicalization always makes 32-bit indvars</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR193">[constantmerge] Merging globals can
+ cause use of invalid pointers!</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR212">[bcreader] Bytecode reader misreads 'long -9223372036854775808'!</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=174">Tail duplication does not update SSA form correctly.</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR218">VMCore mishandles double -0.0</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR219">[X86] X86 backend code generates -0.0 as +0.0</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR223">[loopsimplify] Loopsimplify incorrectly updates dominator information</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR225">[pruneeh] -pruneeh pass removes invoke instructions it shouldn't</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR228">[sparc] Boolean constants are emitted as true and false</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR234">[interpreter] va_list values silently corrupted by function calls</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR235">Tablegen aborts on errors</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR236">[inliner] Error inlining intrinsic calls into invoke instructions</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR245">Linking weak and strong global variables is dependent on link order</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR258">Variables used to define non-printable FP constants are externally visible</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR259">CBE gives linkonce functions wrong linkage semantics</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR274">[JIT] Programs cannot resolve the fstat function</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR284">[indvars] Induction variable analysis violates LLVM invariants</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR296">[execution engines] Unhandled cast constant expression</a></li>
+
+ </ol>
+
+
+
+ <p>Bugs in the C/C++ front-end:</p>
+
+ <ol>
+ <li><a href="http://llvm.cs.uiuc.edu/PR186">Need weak linkage on memory
+ management functions in libc runtime to allow them to be overriden</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR202">[llvm-gcc] asserts when an extern inline function is redefined</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR204">[llvmg++] Dynamically initialized constants cannot be marked 'constant'</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR216">[llvmgcc] floating-point unary minus is incorrect for +0.0</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR221">[llvm-gcc] miscompilation of 'X = Y = Z' with aggregate values</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR272">[llvmgcc] Invalid code created for complex division operation</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR268">[llvmgcc] Incorrect code generation for pointer subtraction</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR261">[llvmg++] Crash assigning pointers-to-members with casted types</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR291">[llvm-g++] Cleanups and gotos don't mix properly</a></li>
+ <li><a href="http://llvm.cs.uiuc.edu/PR297">[llvmgcc] Crash on auto register variable with specific register specified</a></li>
+ </ol>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="portability">Portability and Supported Platforms</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>LLVM has been extensively tested on Intel and AMD machines running Red
+ Hat Linux and FreeBSD. It has also been tested on Sun UltraSPARC workstations running Solaris 8.
+ Additionally,
+ LLVM works on Mac OS X 10.3 and above, but only with the C backend or
+ interpreter (no native backend for the PowerPC is available yet).
+ The core LLVM infrastructure uses "autoconf" for portability, so hopefully we
+ work on more platforms than that. However, it is likely that we
+ missed something and that minor porting is required to get LLVM to work on
+ new platforms. We welcome portability patches and error messages.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="knownproblems">Known Problems</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This section contains all known problems with the LLVM system, listed by
+ component. As new problems are discovered, they will be added to these
+ sections. If you run into a problem, please check the <a
+ href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
+ there isn't already one.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="experimental">Experimental features included with this release</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ The following components of this LLVM release are either untested, known to be
+ broken or unreliable, or are in early development. These components should not
+ be relied on, and bugs should not be filed against them, but they may be useful
+ to some people. In particular, if you would like to work on one of these
+ components, please contact us on the llvmdev list.
+ </p>
+
+ <ul>
+ <li>The following passes are incomplete or buggy: <tt>-pgmdep, -memdep,
+ -ipmodref, -sortstructs, -swapstructs, -cee</tt></li>
+
+ <li>The <tt>-pre</tt> pass is incomplete (there are cases it doesn't handle that
+ it should) and not thoroughly tested.</li>
+ <li>The <tt>llvm-ar</tt> tool is incomplete and probably buggy.</li>
+ <li>The <tt>llvm-db</tt> tool is in a very early stage of development.</li>
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="core">Known problems with the LLVM Core</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+
+ <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
+ work.</li>
+
+ <li>The JIT does not use mutexes to protect its internal data structures. As
+ such, execution of a threaded program could cause these data structures to be
+ corrupted.</li>
+
+ <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
+
+ <li>Linking in static archive files (.a files) is very slow (there is no symbol
+ table in the archive).</li>
+
+ <li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
+ more than 256 elements</a>.</li>
+
+ <li>The gccld program <a href="http://llvm.cs.uiuc.edu/PR139">does not link objects/archives in the order specified on the command line.</a></li>
+
+ <li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not mark
+ values live across a setjmp as volatile</a>. This missing feature only affects
+ targets whose setjmp/longjmp libraries do not save and restore the entire
+ register file.</li>
+ </ul>
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="c-fe">Known problems with the C front-end</a>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">Bugs</div>
+
+ <div class="doc_text">
+ <ul>
+ <li>C99 Variable sized arrays do not release stack memory when they go out of
+ scope. Thus, the following program may run out of stack space:
+ <pre>
+ for (i = 0; i != 1000000; ++i) {
+ int X[n];
+ foo(X);
+ }
+ </pre></li>
+
+ <li>
+ Initialization of global union variables can only be done
+ <a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=162">with the largest
+ union member</a>.
+ </li>
+
+ <li><a href="http://llvm.cs.uiuc.edu/PR244">[llvm-gcc] Error when an implicitly external function is re-declared as static</a></li>
+
+ </ul>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ Notes
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+
+ <li>Inline assembly is not yet supported.</li>
+
+ <li>"long double" is transformed by the front-end into "double". There is no
+ support for floating point data types of any size other than 32 and 64
+ bits.</li>
+
+ <li>The following Unix system functionality has not been tested and may not
+ work:
+ <ol>
+ <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
+ appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
+ <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
+ <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
+ - These functions have not been tested.
+ </ol></li>
+
+ <li>Although many GCC extensions are supported, some are not. In particular,
+ the following extensions are known to <b>not be</b> supported:
+ <ol>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>: As in Algol and Pascal, lexical scoping of functions.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html#Asm%20Labels">Asm Labels</a>: Specifying the assembler name to use for a C symbol.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html#Explicit%20Reg%20Vars">Explicit Reg Vars</a>: Defining variables residing in specified registers.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
+ </ol>
+
+ <p>The following GCC extensions are <b>partially</b> supported. An ignored
+ attribute means that the LLVM compiler ignores the presence of the attribute,
+ but the code should still work. An unsupported attribute is one which is
+ ignored by the LLVM compiler and will cause a different interpretation of
+ the program.</p>
+
+ <ol>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
+ Arrays whose length is computed at run time.<br>
+ Supported, but allocated stack space is not freed until the function returns (noted above).</li>
+
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
+
+ Declaring that functions have no side effects or that they can never
+ return.<br>
+
+ <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
+ <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
+ <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
+
+ <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
+ <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
+ <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
+
+ <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
+ <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
+ <tt>fastcall</tt>, all other target specific attributes</li>
+
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
+ Specifying attributes of variables.<br>
+ <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
+ <tt>deprecated</tt>, <tt>transparent_union</tt>,
+ <tt>unused</tt>, <tt>weak</tt><br>
+
+ <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
+ <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
+ <tt>vector_size</tt>, <tt>dllimport</tt>,
+ <tt>dllexport</tt>, all target specific attributes.</li>
+
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
+ <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
+ <tt>deprecated</tt>, <tt>may_alias</tt><br>
+
+ <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
+ all target specific attributes.</li>
+
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
+ Other built-in functions.<br>
+ We support all builtins which have a C language equivalent (e.g.,
+ <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
+ <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
+ <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> (ignored).</li>
+
+ </ol>
+
+ <p>The following extensions <b>are</b> known to be supported:</p>
+
+ <ol>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">Labels as Values</a>: Getting pointers to labels and computed gotos.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html#Pointer%20Arith">Pointer Arith</a>: Arithmetic on <code>void</code>-pointers and function pointers.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
+ or arrays as values.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast%20to%20Union">Cast to Union</a>: Casting to union type from any member of the union.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Character-Escapes.html#Character%20Escapes">Character Escapes</a>: <code>\e</code> stands for the character <ESC>.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html#Alternate%20Keywords">Alternate Keywords</a>:<code>__const__</code>, <code>__asm__</code>, etc., for header files.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html#Incomplete%20Enums">Incomplete Enums</a>: <code>enum foo;</code>, with details to follow.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function%20Names">Function Names</a>: Printable strings which are the name of the current function.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html#Return%20Address">Return Address</a>: Getting the return or frame address of a function.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
+ </ol></li>
+
+ </ul>
+
+ <p>If you run into GCC extensions which have not been included in any of these
+ lists, please let us know (also including whether or not they work).</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="c++-fe">Known problems with the C++ front-end</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>For this release, the C++ front-end is considered to be fully functional but
+ has not been tested as thoroughly as the C front-end. It has been tested and
+ works for a number of non-trivial programs, but there may be lurking bugs.
+ Please report any bugs or problems.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">Bugs</div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
+ front-end</a>.</li>
+ </ul>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ Notes
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+
+ <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
+ parser is significantly more standards compliant (and picky) than prior GCC
+ versions. For more information, see the C++ section of the <a
+ href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
+
+ <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
+ performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
+ function and in the <tt>setjmp</tt> receiver function may not be run.
+ Objects in intervening stack frames will be destroyed, however (which is
+ better than most compilers).</li>
+
+ <li>The LLVM C++ front-end follows the <a
+ href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
+ This document, which is not Itanium specific, specifies a standard for name
+ mangling, class layout, v-table layout, RTTI formats, and other C++
+ representation issues. Because we use this API, code generated by the LLVM
+ compilers should be binary compatible with machine code generated by other
+ Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
+ <i>However</i>, the exception handling mechanism used by LLVM is very
+ different from the model used in the Itanium ABI, so <b>exceptions will not
+ interact correctly</b>. </li>
+
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="x86-be">Known problems with the X86 back-end</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li>None so far.
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="sparc-be">Known problems with the Sparc back-end</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+ <li>None so far.
+ </ul>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="c-be">Known problems with the C back-end</a>
+ </div>
+
+ <div class="doc_text">
+
+ <ul>
+
+ <li>The C back-end produces code that violates the ANSI C Type-Based Alias
+ Analysis rules. As such, special options may be necessary to compile the code
+ (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
+ problem probably cannot be fixed.</li>
+
+ <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
+ cannot include special floating point numbers like Not-A-Number or
+ Infinity.</li>
+
+ <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
+ supported</a>. This should not affect LLVM produced by the C or C++
+ frontends.</li>
+
+ </ul>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="additionalinfo">Additional Information</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>A wide variety of additional information is available on the LLVM web page,
+ including mailing lists and publications describing algorithms and components
+ implemented in LLVM. The web page also contains versions of the API
+ documentation which is up-to-date with the CVS version of the source code. You
+ can access versions of these documents specific to this release by going into
+ the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
+
+ <p>If you have any questions or comments about LLVM, please feel free to contact
+ us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
+ lists</a>.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+
+ <hr>
+ <address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
+
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </address>
+
+ </body>
+ </html>
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>Source Level Debugging with LLVM</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">Source Level Debugging with LLVM</div>
+
+ <ul>
+
+ <img src="venusflytrap.jpg" alt="A leafy and green bug eater"
+ width=247 height=369 align=right>
+
+ <li><a href="#introduction">Introduction</a></li>
+ <ol>
+ <li><a href="#phil">Philosophy behind LLVM debugging information</a></li>
+ <li><a href="#debugopt">Debugging optimized code</a></li>
+ <li><a href="#future">Future work</a></li>
+ </ol>
+ <li><a href="#llvm-db">Using the <tt>llvm-db</tt> tool</a>
+ <ol>
+ <li><a href="#limitations">Limitations of <tt>llvm-db</tt></a></li>
+ <li><a href="#sample">A sample <tt>llvm-db</tt> session</a></li>
+ <li><a href="#startup">Starting the debugger</a></li>
+ <li><a href="#commands">Commands recognized by the debugger</a></li>
+ </ol></li>
+
+ <li><a href="#architecture">Architecture of the LLVM debugger</a></li>
+ <ol>
+ <li><a href="#arch_debugger">The Debugger and InferiorProcess classes</a></li>
+ <li><a href="#arch_info">The RuntimeInfo, ProgramInfo, and SourceLanguage classes</a></li>
+ <li><a href="#arch_llvm-db">The <tt>llvm-db</tt> tool</a></li>
+ <li><a href="#arch_todo">Short-term TODO list</a></li>
+ </ol>
+
+ <li><a href="#format">Debugging information format</a></li>
+ <ol>
+ <li><a href="#format_common_anchors">Anchors for global objects</a></li>
+ <li><a href="#format_common_stoppoint">Representing stopping points in the source program</a></li>
+ <li><a href="#format_common_lifetime">Object lifetimes and scoping</a></li>
+ <li><a href="#format_common_descriptors">Object descriptor formats</a></li>
+ <ul>
+ <li><a href="#format_common_source_files">Representation of source files</a></li>
+ <li><a href="#format_common_program_objects">Representation of program objects</a></li>
+ <li><a href="#format_common_object_contexts">Program object contexts</a></li>
+ </ul>
+ <li><a href="#format_common_intrinsics">Debugger intrinsic functions</a></li>
+ <li><a href="#format_common_tags">Values for debugger tags</a></li>
+ </ol>
+ <li><a href="#ccxx_frontend">C/C++ front-end specific debug information</a></li>
+ <ol>
+ <li><a href="#ccxx_pse">Program Scope Entries</a></li>
+ <ul>
+ <li><a href="#ccxx_compilation_units">Compilation unit entries</a></li>
+ <li><a href="#ccxx_modules">Module, namespace, and importing entries</a></li>
+ </ul>
+ <li><a href="#ccxx_dataobjects">Data objects (program variables)</a></li>
+ </ol>
+ </ul>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section"><a name="introduction">Introduction</a></div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>This document is the central repository for all information pertaining to
+ debug information in LLVM. It describes the <a href="#llvm-db">user
+ interface</a> for the <a href="CommandGuide/llvm-db.html"><tt>llvm-db</tt>
+ tool</a>, which provides a powerful <a href="#llvm-db">source-level debugger</a>
+ to users of LLVM-based compilers. It then describes the <a
+ href="#architecture">various components</a> that make up the debugger and the
+ libraries which future clients may use. Finally, it describes the <a
+ href="#format">actual format that the LLVM debug information</a> takes,
+ which is useful for those interested in creating front-ends or dealing directly
+ with the information.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="phil">Philosophy behind LLVM debugging information</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ The idea of the LLVM debugging information is to capture how the important
+ pieces of the source-language's Abstract Syntax Tree map onto LLVM code.
+ Several design aspects have shaped the solution that appears here. The
+ important ones are:</p>
+
+ <p><ul>
+ <li>Debugging information should have very little impact on the rest of the
+ compiler. No transformations, analyses, or code generators should need to be
+ modified because of debugging information.</li>
+
+ <li>LLVM optimizations should interact in <a href="#debugopt">well-defined and
+ easily described ways</a> with the debugging information.</li>
+
+ <li>Because LLVM is designed to support arbitrary programming languages,
+ LLVM-to-LLVM tools should not need to know anything about the semantics of the
+ source-level-language.</li>
+
+ <li>Source-level languages are often <b>widely</b> different from one another.
+ LLVM should not put any restrictions of the flavor of the source-language, and
+ the debugging information should work with any language.</li>
+
+ <li>With code generator support, it should be possible to use an LLVM compiler
+ to compile a program to native machine code and standard debugging formats.
+ This allows compatibility with traditional machine-code level debuggers, like
+ GDB or DBX.</li>
+
+ </ul></p>
+
+ <p>
+ The approach used by the LLVM implementation is to use a small set of <a
+ href="#format_common_intrinsics">intrinsic functions</a> to define a mapping
+ between LLVM program objects and the source-level objects. The description of
+ the source-level program is maintained in LLVM global variables in an <a
+ href="#ccxx_frontend">implementation-defined format</a> (the C/C++ front-end
+ currently uses working draft 7 of the <a
+ href="http://www.eagercon.com/dwarf/dwarf3std.htm">Dwarf 3 standard</a>).</p>
+
+ <p>
+ When a program is debugged, the debugger interacts with the user and turns the
+ stored debug information into source-language specific information. As such,
+ the debugger must be aware of the source-language, and is thus tied to a
+ specific language of family of languages. The <a href="#llvm-db">LLVM
+ debugger</a> is designed to be modular in its support for source-languages.
+ </p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="debugopt">Debugging optimized code</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ An extremely high priority of LLVM debugging information is to make it interact
+ well with optimizations and analysis. In particular, the LLVM debug information
+ provides the following guarantees:</p>
+
+ <p><ul>
+
+ <li>LLVM debug information <b>always provides information to accurately read the
+ source-level state of the program</b>, regardless of which LLVM optimizations
+ have been run, and without any modification to the optimizations themselves.
+ However, some optimizations may impact the ability to modify the current state
+ of the program with a debugger, such as setting program variables, or calling
+ function that have been deleted.</li>
+
+ <li>LLVM optimizations gracefully interact with debugging information. If they
+ are not aware of debug information, they are automatically disabled as necessary
+ in the cases that would invalidate the debug info. This retains the LLVM
+ features making it easy to write new transformations.</li>
+
+ <li>As desired, LLVM optimizations can be upgraded to be aware of the LLVM
+ debugging information, allowing them to update the debugging information as they
+ perform aggressive optimizations. This means that, with effort, the LLVM
+ optimizers could optimize debug code just as well as non-debug code.</li>
+
+ <li>LLVM debug information does not prevent many important optimizations from
+ happening (for example inlining, basic block reordering/merging/cleanup, tail
+ duplication, etc), further reducing the amount of the compiler that eventually
+ is "aware" of debugging information.</li>
+
+ <li>LLVM debug information is automatically optimized along with the rest of the
+ program, using existing facilities. For example, duplicate information is
+ automatically merged by the linker, and unused information is automatically
+ removed.</li>
+
+ </ul></p>
+
+ <p>
+ Basically, the debug information allows you to compile a program with "<tt>-O0
+ -g</tt>" and get full debug information, allowing you to arbitrarily modify the
+ program as it executes from the debugger. Compiling a program with "<tt>-O3
+ -g</tt>" gives you full debug information that is always available and accurate
+ for reading (e.g., you get accurate stack traces despite tail call elimination
+ and inlining), but you might lose the ability to modify the program and call
+ functions where were optimized out of the program, or inlined away completely.
+ </p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="future">Future work</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ There are several important extensions that could be eventually added to the
+ LLVM debugger. The most important extension would be to upgrade the LLVM code
+ generators to support debugging information. This would also allow, for
+ example, the X86 code generator to emit native objects that contain debugging
+ information consumable by traditional source-level debuggers like GDB or
+ DBX.</p>
+
+ <p>
+ Additionally, LLVM optimizations can be upgraded to incrementally update the
+ debugging information, <a href="#commands">new commands</a> can be added to the
+ debugger, and thread support could be added to the debugger.</p>
+
+ <p>
+ The "SourceLanguage" modules provided by <tt>llvm-db</tt> could be substantially
+ improved to provide good support for C++ language features like namespaces and
+ scoping rules.</p>
+
+ <p>
+ After working with the debugger for a while, perhaps the nicest improvement
+ would be to add some sort of line editor, such as GNU readline (but one that is
+ compatible with the LLVM license).</p>
+
+ <p>
+ For someone so inclined, it should be straight-forward to write different
+ front-ends for the LLVM debugger, as the LLVM debugging engine is cleanly
+ separated from the <tt>llvm-db</tt> front-end. A new LLVM GUI debugger or IDE
+ would be nice. :)
+ </p>
+
+ </div>
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="llvm-db">Using the <tt>llvm-db</tt> tool</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>
+ The <tt>llvm-db</tt> tool provides a GDB-like interface for source-level
+ debugging of programs. This tool provides many standard commands for inspecting
+ and modifying the program as it executes, loading new programs, single stepping,
+ placing breakpoints, etc. This section describes how to use the debugger.
+ </p>
+
+ <p><tt>llvm-db</tt> has been designed to be as similar to GDB in its user
+ interface as possible. This should make it extremely easy to learn
+ <tt>llvm-db</tt> if you already know <tt>GDB</tt>. In general, <tt>llvm-db</tt>
+ provides the subset of GDB commands that are applicable to LLVM debugging users.
+ If there is a command missing that make a reasonable amount of sense within the
+ <a href="#limitations">limitations of <tt>llvm-db</tt></a>, please report it as
+ a bug or, better yet, submit a patch to add it. :)</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="limitations">Limitations of <tt>llvm-db</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><tt>llvm-db</tt> is designed to be modular and easy to extend. This
+ extensibility was key to getting the debugger up-and-running quickly, because we
+ can start with simple-but-unsophisicated implementations of various components.
+ Because of this, it is currently missing many features, though they should be
+ easy to add over time (patches welcomed!). The biggest inherent limitations of
+ <tt>llvm-db</tt> are currently due to extremely simple <a
+ href="#arch_debugger">debugger backend</a> (implemented in
+ "lib/Debugger/UnixLocalInferiorProcess.cpp") which is designed to work without
+ any cooperation from the code generators. Because it is so simple, it suffers
+ from the following inherent limitations:</p>
+
+ <p><ul>
+
+ <li>Running a program in <tt>llvm-db</tt> is a bit slower than running it with
+ <tt>lli</tt> (i.e., in the JIT).</li>
+
+ <li>Inspection of the target hardware is not supported. This means that you
+ cannot, for example, print the contents of X86 registers.</li>
+
+ <li>Inspection of LLVM code is not supported. This means that you cannot print
+ the contents of arbitrary LLVM values, or use commands such as <tt>stepi</tt>.
+ This also means that you cannot debug code without debug information.</li>
+
+ <li>Portions of the debugger run in the same address space as the program being
+ debugged. This means that memory corruption by the program could trample on
+ portions of the debugger.</li>
+
+ <li>Attaching to existing processes and core files is not currently
+ supported.</li>
+
+ </ul></p>
+
+ <p>That said, the debugger is still quite useful, and all of these limitations
+ can be eliminated by integrating support for the debugger into the code
+ generators, and writing a new <a href="#arch_debugger">InferiorProcess</a>
+ subclass to use it. See the <a href="#future">future work</a> section for ideas
+ of how to extend the LLVM debugger despite these limitations.</p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="sample">A sample <tt>llvm-db</tt> session</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>TODO: this is obviously lame, when more is implemented, this can be much
+ better.</p>
+
+ <p><pre>
+ $ <b>llvm-db funccall</b>
+ llvm-db: The LLVM source-level debugger
+ Loading program... successfully loaded 'funccall.bc'!
+ (llvm-db) <b>create</b>
+ Starting program: funccall.bc
+ main at funccall.c:9:2
+ 9 -> q = 0;
+ (llvm-db) <b>list main</b>
+ 4 void foo() {
+ 5 int t = q;
+ 6 q = t + 1;
+ 7 }
+ 8 int main() {
+ 9 -> q = 0;
+ 10 foo();
+ 11 q = q - 1;
+ 12
+ 13 return q;
+ (llvm-db) <b>list</b>
+ 14 }
+ (llvm-db) <b>step</b>
+ 10 -> foo();
+ (llvm-db) <b>s</b>
+ foo at funccall.c:5:2
+ 5 -> int t = q;
+ (llvm-db) <b>bt</b>
+ #0 -> 0x85ffba0 in foo at funccall.c:5:2
+ #1 0x85ffd98 in main at funccall.c:10:2
+ (llvm-db) <b>finish</b>
+ main at funccall.c:11:2
+ 11 -> q = q - 1;
+ (llvm-db) <b>s</b>
+ 13 -> return q;
+ (llvm-db) <b>s</b>
+ The program stopped with exit code 0
+ (llvm-db) <b>quit</b>
+ $
+ </pre></p>
+
+ </div>
+
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="startup">Starting the debugger</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>There are three ways to start up the <tt>llvm-db</tt> debugger:</p>
+
+ <p>When run with no options, just <tt>llvm-db</tt>, the debugger starts up
+ without a program loaded at all. You must use the <a
+ href="#c_file"><tt>file</tt> command</a> to load a program, and the <a
+ href="c_set_args"><tt>set args</tt></a> or <a href="#c_run"><tt>run</tt></a>
+ commands to specify the arguments for the program.</p>
+
+ <p>If you start the debugger with one argument, as <tt>llvm-db
+ <program></tt>, the debugger will start up and load in the specified
+ program. You can then optionally specify arguments to the program with the <a
+ href="c_set_args"><tt>set args</tt></a> or <a href="#c_run"><tt>run</tt></a>
+ commands.</p>
+
+ <p>The third way to start the program is with the <tt>--args</tt> option. This
+ option allows you to specify the program to load and the arguments to start out
+ with. <!-- No options to <tt>llvm-db</tt> may be specified after the
+ <tt>-args</tt> option. --> Example use: <tt>llvm-db --args ls /home</tt></p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="commands">Commands recognized by the debugger</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>FIXME: this needs work obviously. See the <a
+ href="http://sources.redhat.com/gdb/documentation/">GDB documentation</a> for
+ information about what these do, or try '<tt>help [command]</tt>' within
+ <tt>llvm-db</tt> to get information.</p>
+
+ <p>
+ <h2>General usage:</h2>
+ <ul>
+ <li>help [command]</li>
+ <li>quit</li>
+ <li><a name="c_file">file</a> [program]</li>
+ </ul>
+
+ <h2>Program inspection and interaction:</h2>
+ <ul>
+ <li>create (start the program, stopping it ASAP in <tt>main</tt>)</li>
+ <li>kill</li>
+ <li>run [args]</li>
+ <li>step [num]</li>
+ <li>next [num]</li>
+ <li>cont</li>
+ <li>finish</li>
+
+ <li>list [start[, end]]</li>
+ <li>info source</li>
+ <li>info sources</li>
+ <li>info functions</li>
+ </ul>
+
+ <h2>Call stack inspection:</h2>
+ <ul>
+ <li>backtrace</li>
+ <li>up [n]</li>
+ <li>down [n]</li>
+ <li>frame [n]</li>
+ </ul>
+
+
+ <h2>Debugger inspection and interaction:</h2>
+ <ul>
+ <li>info target</li>
+ <li>show prompt</li>
+ <li>set prompt</li>
+ <li>show listsize</li>
+ <li>set listsize</li>
+ <li>show language</li>
+ <li>set language</li>
+ <li>show args</li>
+ <li>set args [args]</li>
+ </ul>
+
+ <h2>TODO:</h2>
+ <ul>
+ <li>info frame</li>
+ <li>break</li>
+ <li>print</li>
+ <li>ptype</li>
+
+ <li>info types</li>
+ <li>info variables</li>
+ <li>info program</li>
+
+ <li>info args</li>
+ <li>info locals</li>
+ <li>info catch</li>
+ <li>... many others</li>
+ </ul>
+ </p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="architecture">Architecture of the LLVM debugger</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>
+ The LLVM debugger is built out of three distinct layers of software. These
+ layers provide clients with different interface options depending on what pieces
+ of they want to implement themselves, and it also promotes code modularity and
+ good design. The three layers are the <a href="#arch_debugger">Debugger
+ interface</a>, the <a href="#arch_info">"info" interfaces</a>, and the
+ <a href="#arch_llvm-db"><tt>llvm-db</tt> tool</a> itself.
+ </p>
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="arch_debugger">The Debugger and InferiorProcess classes</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ The Debugger class (defined in the <tt>include/llvm/Debugger/</tt> directory) is
+ a low-level class which is used to maintain information about the loaded
+ program, as well as start and stop the program running as necessary. This class
+ does not provide any high-level analysis or control over the program, only
+ exposing simple interfaces like <tt>load/unloadProgram</tt>,
+ <tt>create/killProgram</tt>, <tt>step/next/finish/contProgram</tt>, and
+ low-level methods for installing breakpoints.
+ </p>
+
+ <p>
+ The Debugger class is itself a wrapper around the lowest-level InferiorProcess
+ class. This class is used to represent an instance of the program running under
+ debugger control. The InferiorProcess class can be implemented in different
+ ways for different targets and execution scenarios (e.g., remote debugging).
+ The InferiorProcess class exposes a small and simple collection of interfaces
+ which are useful for inspecting the current state of the program (such as
+ collecting stack trace information, reading the memory image of the process,
+ etc). The interfaces in this class are designed to be as low-level and simple
+ as possible, to make it easy to create new instances of the class.
+ </p>
+
+ <p>
+ The Debugger class exposes the currently active instance of InferiorProcess
+ through the <tt>Debugger::getRunningProcess</tt> method, which returns a
+ <tt>const</tt> reference to the class. This means that clients of the Debugger
+ class can only <b>inspect</b> the running instance of the program directly. To
+ change the executing process in some way, they must use the interces exposed by
+ the Debugger class.
+ </p>
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="arch_info">The RuntimeInfo, ProgramInfo, and SourceLanguage classes</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ The next-highest level of debugger abstraction is provided through the
+ ProgramInfo, RuntimeInfo, SourceLanguage and related classes (also defined in
+ the <tt>include/llvm/Debugger/</tt> directory). These classes efficiently
+ decode the debugging information and low-level interfaces exposed by
+ InferiorProcess into a higher-level representation, suitable for analysis by the
+ debugger.
+ </p>
+
+ <p>
+ The ProgramInfo class exposes a variety of different kinds of information about
+ the program objects in the source-level-language. The SourceFileInfo class
+ represents a source-file in the program (e.g. a .cpp or .h file). The
+ SourceFileInfo class captures information such as which SourceLanguage was used
+ to compile the file, where the debugger can get access to the actual file text
+ (which is lazily loaded on demand), etc. The SourceFunctionInfo class
+ represents a... <b>FIXME: finish</b>. The ProgramInfo class provides interfaces
+ to lazily find and decode the information needed to create the Source*Info
+ classes requested by the debugger.
+ </p>
+
+ <p>
+ The RuntimeInfo class exposes information about the currently executed program,
+ by decoding information from the InferiorProcess and ProgramInfo classes. It
+ provides a StackFrame class which provides an easy-to-use interface for
+ inspecting the current and suspended stack frames in the program.
+ </p>
+
+ <p>
+ The SourceLanguage class is an abstract interface used by the debugger to
+ perform all source-language-specific tasks. For example, this interface is used
+ by the ProgramInfo class to decode language-specific types and functions and by
+ the debugger front-end (such as <a href="#arch_llvm-db"><tt>llvm-db</tt></a> to
+ evaluate source-langauge expressions typed into the debugger. This class uses
+ the RuntimeInfo & ProgramInfo classes to get information about the current
+ execution context and the loaded program, respectively.
+ </p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="arch_llvm-db">The <tt>llvm-db</tt> tool</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ The <tt>llvm-db</tt> is designed to be a debugger providing an interface as <a
+ href="#llvm-db">similar to GDB</a> as reasonable, but no more so than that.
+ Because the <a href="#arch_debugger">Debugger</a> and <a
+ href="#arch_info">info</a> classes implement all of the heavy lifting and
+ analysis, <tt>llvm-db</tt> (which lives in <tt>llvm/tools/llvm-db</tt>) consists
+ mainly of of code to interact with the user and parse commands. The CLIDebugger
+ constructor registers all of the builtin commands for the debugger, and each
+ command is implemented as a CLIDebugger::[name]Command method.
+ </p>
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="arch_todo">Short-term TODO list</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ FIXME: this section will eventually go away. These are notes to myself of
+ things that should be implemented, but haven't yet.
+ </p>
+
+ <p>
+ <b>Breakpoints:</b> Support is already implemented in the 'InferiorProcess'
+ class, though it hasn't been tested yet. To finish breakpoint support, we need
+ to implement breakCommand (which should reuse the linespec parser from the list
+ command), and handle the fact that 'break foo' or 'break file.c:53' may insert
+ multiple breakpoints. Also, if you say 'break file.c:53' and there is no
+ stoppoint on line 53, the breakpoint should go on the next available line. My
+ idea was to have the Debugger class provide a "Breakpoint" class which
+ encapsulated this messiness, giving the debugger front-end a simple interface.
+ The debugger front-end would have to map the really complex semantics of
+ temporary breakpoints and 'conditional' breakpoints onto this intermediate
+ level. Also, breakpoints should survive as much as possible across program
+ reloads.
+ </p>
+
+ <p>
+ <b>UnixLocalInferiorProcess.cpp speedup</b>: There is no reason for the debugged
+ process to code gen the globals corresponding to debug information. The
+ IntrinsicLowering object could instead change descriptors into constant expr
+ casts of the constant address of the LLVM objects for the descriptors. This
+ would also allow us to eliminate the mapping back and forth between physical
+ addresses that must be done.</p>
+
+ <p>
+ <b>Process deaths</b>: The InferiorProcessDead exception should be extended to
+ know "how" a process died, i.e., it was killed by a signal. This is easy to
+ collect in the UnixLocalInferiorProcess, we just need to represent it.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="format">Debugging information format</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>LLVM debugging information has been carefully designed to make it possible
+ for the optimizer to optimize the program and debugging information without
+ necessarily having to know anything about debugging information. In particular,
+ the global constant merging pass automatically eliminates duplicated debugging
+ information (often caused by header files), the global dead code elimination
+ pass automatically deletes debugging information for a function if it decides to
+ delete the function, and the linker eliminates debug information when it merges
+ <tt>linkonce</tt> functions.</p>
+
+ <p>To do this, most of the debugging information (descriptors for types,
+ variables, functions, source files, etc) is inserted by the language front-end
+ in the form of LLVM global variables. These LLVM global variables are no
+ different from any other global variables, except that they have a web of LLVM
+ intrinsic functions that point to them. If the last references to a particular
+ piece of debugging information are deleted (for example, by the
+ <tt>-globaldce</tt> pass), the extraneous debug information will automatically
+ become dead and be removed by the optimizer.</p>
+
+ <p>The debugger is designed to be agnostic about the contents of most of the
+ debugging information. It uses a <a href="#arch_info">source-language-specific
+ module</a> to decode the information that represents variables, types,
+ functions, namespaces, etc: this allows for arbitrary source-language semantics
+ and type-systems to be used, as long as there is a module written for the
+ debugger to interpret the information.
+ </p>
+
+ <p>
+ To provide basic functionality, the LLVM debugger does have to make some
+ assumptions about the source-level language being debugged, though it keeps
+ these to a minimum. The only common features that the LLVM debugger assumes
+ exist are <a href="#format_common_source_files">source files</a>, and <a
+ href="#format_program_objects">program objects</a>. These abstract objects are
+ used by the debugger to form stack traces, show information about local
+ variables, etc.
+
+ <p>This section of the documentation first describes the representation aspects
+ common to any source-language. The <a href="#ccxx_frontend">next section</a>
+ describes the data layout conventions used by the C and C++ front-ends.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="format_common_anchors">Anchors for global objects</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ One important aspect of the LLVM debug representation is that it allows the LLVM
+ debugger to efficiently index all of the global objects without having the scan
+ the program. To do this, all of the global objects use "anchor" globals of type
+ "<tt>{}</tt>", with designated names. These anchor objects obviously do not
+ contain any content or meaning by themselves, but all of the global objects of a
+ particular type (e.g., source file descriptors) contain a pointer to the anchor.
+ This pointer allows the debugger to use def-use chains to find all global
+ objects of that type.
+ </p>
+
+ <p>
+ So far, the following names are recognized as anchors by the LLVM debugger:
+ </p>
+
+ <p><pre>
+ %<a href="#format_common_source_files">llvm.dbg.translation_units</a> = linkonce global {} {}
+ %<a href="#format_program_objects">llvm.dbg.globals</a> = linkonce global {} {}
+ </pre></p>
+
+ <p>
+ Using anchors in this way (where the source file descriptor points to the
+ anchors, as opposed to having a list of source file descriptors) allows for the
+ standard dead global elimination and merging passes to automatically remove
+ unused debugging information. If the globals were kept track of through lists,
+ there would always be an object pointing to the descriptors, thus would never be
+ deleted.
+ </p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="format_common_stoppoint">
+ Representing stopping points in the source program
+ </a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>LLVM debugger "stop points" are a key part of the debugging representation
+ that allows the LLVM to maintain simple semantics for <a
+ href="#debugopt">debugging optimized code</a>. The basic idea is that the
+ front-end inserts calls to the <tt>%llvm.dbg.stoppoint</tt> intrinsic function
+ at every point in the program where the debugger should be able to inspect the
+ program (these correspond to places the debugger stops when you "<tt>step</tt>"
+ through it). The front-end can choose to place these as fine-grained as it
+ would like (for example, before every subexpression evaluated), but it is
+ recommended to only put them after every source statement that includes
+ executable code.</p>
+
+ <p>
+ Using calls to this intrinsic function to demark legal points for the debugger
+ to inspect the program automatically disables any optimizations that could
+ potentially confuse debugging information. To non-debug-information-aware
+ transformations, these calls simply look like calls to an external function,
+ which they must assume to do anything (including reading or writing to any part
+ of reachable memory). On the other hand, it does not impact many optimizations,
+ such as code motion of non-trapping instructions, nor does it impact
+ optimization of subexpressions, code duplication transformations, or basic-block
+ reordering transformations.</p>
+
+ <p>
+ An important aspect of the calls to the <tt>%llvm.dbg.stoppoint</tt> intrinsic
+ is that the function-local debugging information is woven together with use-def
+ chains. This makes it easy for the debugger to, for example, locate the 'next'
+ stop point. For a concrete example of stop points, see the example in <a
+ href="#format_common_lifetime">the next section</a>.</p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="format_common_lifetime">Object lifetimes and scoping</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ In many languages, the local variables in functions can have their lifetime or
+ scope limited to a subset of a function. In the C family of languages, for
+ example, variables are only live (readable and writable) within the source block
+ that they are defined in. In functional languages, values are only readable
+ after they have been defined. Though this is a very obvious concept, it is also
+ non-trivial to model in LLVM, because it has no notion of scoping in this sense,
+ and does not want to be tied to a language's scoping rules.
+ </p>
+
+ <p>
+ In order to handle this, the LLVM debug format uses the notion of "regions" of a
+ function, delineated by calls to intrinsic functions. These intrinsic functions
+ define new regions of the program and indicate when the region lifetime expires.
+ Consider the following C fragment, for example:
+ </p>
+
+ <p><pre>
+ 1. void foo() {
+ 2. int X = ...;
+ 3. int Y = ...;
+ 4. {
+ 5. int Z = ...;
+ 6. ...
+ 7. }
+ 8. ...
+ 9. }
+ </pre></p>
+
+ <p>
+ Compiled to LLVM, this function would be represented like this (FIXME: CHECK AND
+ UPDATE THIS):
+ </p>
+
+ <p><pre>
+ void %foo() {
+ %X = alloca int
+ %Y = alloca int
+ %Z = alloca int
+ <a name="#icl_ex_D1">%D1</a> = call {}* %llvm.dbg.func.start(<a href="#format_program_objects">%lldb.global</a>* %d.foo)
+ %D2 = call {}* <a href="#format_common_stoppoint">%llvm.dbg.stoppoint</a>({}* %D1, uint 2, uint 2, <a href="#format_common_source_files">%lldb.compile_unit</a>* %file)
+
+ %D3 = call {}* %llvm.dbg.DEFINEVARIABLE({}* %D2, ...)
+ <i>;; Evaluate expression on line 2, assigning to X.</i>
+ %D4 = call {}* <a href="#format_common_stoppoint">%llvm.dbg.stoppoint</a>({}* %D3, uint 3, uint 2, <a href="#format_common_source_files">%lldb.compile_unit</a>* %file)
+
+ %D5 = call {}* %llvm.dbg.DEFINEVARIABLE({}* %D4, ...)
+ <i>;; Evaluate expression on line 3, assigning to Y.</i>
+ %D6 = call {}* <a href="#format_common_stoppoint">%llvm.dbg.stoppoint</a>({}* %D5, uint 5, uint 4, <a href="#format_common_source_files">%lldb.compile_unit</a>* %file)
+
+ <a name="#icl_ex_D1">%D7</a> = call {}* %llvm.region.start({}* %D6)
+ %D8 = call {}* %llvm.dbg.DEFINEVARIABLE({}* %D7, ...)
+ <i>;; Evaluate expression on line 5, assigning to Z.</i>
+ %D9 = call {}* <a href="#format_common_stoppoint">%llvm.dbg.stoppoint</a>({}* %D8, uint 6, uint 4, <a href="#format_common_source_files">%lldb.compile_unit</a>* %file)
+
+ <i>;; Code for line 6.</i>
+ %D10 = call {}* %llvm.region.end({}* %D9)
+ %D11 = call {}* <a href="#format_common_stoppoint">%llvm.dbg.stoppoint</a>({}* %D10, uint 8, uint 2, <a href="#format_common_source_files">%lldb.compile_unit</a>* %file)
+
+ <i>;; Code for line 8.</i>
+ <a name="#icl_ex_D1">%D12</a> = call {}* %llvm.region.end({}* %D11)
+ ret void
+ }
+ </pre></p>
+
+ <p>
+ This example illustrates a few important details about the LLVM debugging
+ information. In particular, it shows how the various intrinsics used are woven
+ together with def-use and use-def chains, similar to how <a
+ href="#format_common_anchors">anchors</a> are used with globals. This allows the
+ debugger to analyze the relationship between statements, variable definitions,
+ and the code used to implement the function.</p>
+
+ <p>
+ In this example, two explicit regions are defined, one with the <a
+ href="#icl_ex_D1">definition of the <tt>%D1</tt> variable</a> and one with the
+ <a href="#icl_ex_D7">definition of <tt>%D7</tt></a>. In the case of
+ <tt>%D1</tt>, the debug information indicates that the function whose <a
+ href="#format_program_objects">descriptor</a> is specified as an argument to the
+ intrinsic. This defines a new stack frame whose lifetime ends when the region
+ is ended by <a href="#icl_ex_D12">the <tt>%D12</tt> call</a>.</p>
+
+ <p>
+ Using regions to represent the boundaries of source-level functions allow LLVM
+ interprocedural optimizations to arbitrarily modify LLVM functions without
+ having to worry about breaking mapping information between the LLVM code and the
+ and source-level program. In particular, the inliner requires no modification
+ to support inlining with debugging information: there is no explicit correlation
+ drawn between LLVM functions and their source-level counterparts (note however,
+ that if the inliner inlines all instances of a non-strong-linkage function into
+ its caller that it will not be possible for the user to manually invoke the
+ inlined function from the debugger).</p>
+
+ <p>
+ Once the function has been defined, the <a
+ href="#format_common_stoppoint">stopping point</a> corresponding to line #2 of the
+ function is encountered. At this point in the function, <b>no</b> local
+ variables are live. As lines 2 and 3 of the example are executed, their
+ variable definitions are automatically introduced into the program, without the
+ need to specify a new region. These variables do not require new regions to be
+ introduced because they go out of scope at the same point in the program: line
+ 9.
+ </p>
+
+ <p>
+ In contrast, the <tt>Z</tt> variable goes out of scope at a different time, on
+ line 7. For this reason, it is defined within <a href="#icl_ex_D7">the
+ <tt>%D7</tt> region</a>, which kills the availability of <tt>Z</tt> before the
+ code for line 8 is executed. In this way, regions can support arbitrary
+ source-language scoping rules, as long as they can only be nested (ie, one scope
+ cannot partially overlap with a part of another scope).
+ </p>
+
+ <p>
+ It is worth noting that this scoping mechanism is used to control scoping of all
+ declarations, not just variable declarations. For example, the scope of a C++
+ using declaration is controlled with this, and the <tt>llvm-db</tt> C++ support
+ routines could use this to change how name lookup is performed (though this is
+ not implemented yet).
+ </p>
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="format_common_descriptors">Object descriptor formats</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ The LLVM debugger expects the descriptors for program objects to start in a
+ canonical format, but the descriptors can include additional information
+ appended at the end that is source-language specific. All LLVM debugging
+ information is versioned, allowing backwards compatibility in the case that the
+ core structures need to change in some way. Also, all debugging information
+ objects start with a <a href="#format_common_tags">tag</a> to indicate what type
+ of object it is. The source-language is allows to define its own objects, by
+ using unreserved tag numbers.</p>
+
+ <p>The lowest-level descriptor are those describing <a
+ href="#format_common_source_files">the files containing the program source
+ code</a>, as most other descriptors (sometimes indirectly) refer to them.
+ </p>
+ </div>
+
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="format_common_source_files">Representation of source files</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ Source file descriptors are patterned after the Dwarf "compile_unit" object.
+ The descriptor currently is defined to have at least the following LLVM
+ type entries:</p>
+
+ <p><pre>
+ %lldb.compile_unit = type {
+ uint, <i>;; Tag: <a href="#tag_compile_unit">LLVM_COMPILE_UNIT</a></i>
+ ushort, <i>;; LLVM debug version number</i>
+ ushort, <i>;; Dwarf language identifier</i>
+ sbyte*, <i>;; Filename</i>
+ sbyte*, <i>;; Working directory when compiled</i>
+ sbyte* <i>;; Producer of the debug information</i>
+ }
+ </pre></p>
+
+ <p>
+ These descriptors contain the version number for the debug info, a source
+ language ID for the file (we use the Dwarf 3.0 ID numbers, such as
+ <tt>DW_LANG_C89</tt>, <tt>DW_LANG_C_plus_plus</tt>, <tt>DW_LANG_Cobol74</tt>,
+ etc), three strings describing the filename, working directory of the compiler,
+ and an identifier string for the compiler that produced it. Note that actual
+ compile_unit declarations must also include an <a
+ href="#format_common_anchors">anchor</a> to <tt>llvm.dbg.translation_units</tt>,
+ but it is not specified where the anchor is to be located. Here is an example
+ descriptor:
+ </p>
+
+ <p><pre>
+ %arraytest_source_file = internal constant %lldb.compile_unit {
+ <a href="#tag_compile_unit">uint 17</a>, ; Tag value
+ ushort 0, ; Version #0
+ ushort 1, ; DW_LANG_C89
+ sbyte* getelementptr ([12 x sbyte]* %.str_1, long 0, long 0), ; filename
+ sbyte* getelementptr ([12 x sbyte]* %.str_2, long 0, long 0), ; working dir
+ sbyte* getelementptr ([12 x sbyte]* %.str_3, long 0, long 0), ; producer
+ {}* %llvm.dbg.translation_units ; Anchor
+ }
+ %.str_1 = internal constant [12 x sbyte] c"arraytest.c\00"
+ %.str_2 = internal constant [12 x sbyte] c"/home/sabre\00"
+ %.str_3 = internal constant [12 x sbyte] c"llvmgcc 3.4\00"
+ </pre></p>
+
+ <p>
+ Note that the LLVM constant merging pass should eliminate duplicate copies of
+ the strings that get emitted to each translation unit, such as the producer.
+ </p>
+
+ </div>
+
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="format_program_objects">Representation of program objects</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ The LLVM debugger needs to know about some source-language program objects, in
+ order to build stack traces, print information about local variables, and other
+ related activities. The LLVM debugger differentiates between three different
+ types of program objects: subprograms (functions, messages, methods, etc),
+ variables (locals and globals), and others. Because source-languages have
+ widely varying forms of these objects, the LLVM debugger expects only a few
+ fields in the descriptor for each object:
+ </p>
+
+ <p><pre>
+ %lldb.object = type {
+ uint, <i>;; <a href="#format_common_tag">A tag</a></i>
+ <i>any</i>*, <i>;; The <a href="#format_common_object_contexts">context</a> for the object</i>
+ sbyte* <i>;; The object 'name'</i>
+ }
+ </pre></p>
+
+ <p>
+ The first field contains a tag for the descriptor. The second field contains
+ either a pointer to the descriptor for the containing <a
+ href="#format_common_source_files">source file</a>, or it contains a pointer to
+ another program object whose context pointer eventually reaches a source file.
+ Through this <a href="#format_common_object_contexts">context</a> pointer, the
+ LLVM debugger can establish the debug version number of the object.</p>
+
+ <p>
+ The third field contains a string that the debugger can use to identify the
+ object if it does not contain explicit support for the source-language in use
+ (ie, the 'unknown' source language handler uses this string). This should be
+ some sort of unmangled string that corresponds to the object, but it is a
+ quality of implementation issue what exactly it contains (it is legal, though
+ not useful, for all of these strings to be null).
+ </p>
+
+ <p>
+ Note again that descriptors can be extended to include source-language-specific
+ information in addition to the fields required by the LLVM debugger. See the <a
+ href="#ccxx_descriptors">section on the C/C++ front-end</a> for more
+ information. Also remember that global objects (functions, selectors, global
+ variables, etc) must contain an <a href="format_common_anchors">anchor</a> to
+ the <tt>llvm.dbg.globals</tt> variable.
+ </p>
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="format_common_object_contexts">Program object contexts</a>
+ </div>
+
+ <div class="doc_text">
+ <p><pre>
+ Allow source-language specific contexts, use to identify namespaces etc
+ Must end up in a source file descriptor.
+ Debugger core ignores all unknown context objects.
+ </pre></p>
+ </div>
+
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="format_common_intrinsics">Debugger intrinsic functions</a>
+ </div>
+
+ <div class="doc_text">
+ <p><pre>
+ Define each intrinsics, as an extension of the language reference manual.
+
+ llvm.dbg.stoppoint
+ llvm.dbg.region.start
+ llvm.dbg.region.end
+ llvm.dbg.function.start
+ llvm.dbg.declare
+ </pre></p>
+ </div>
+
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="format_common_tags">Values for debugger tags</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ Happen to be the same value as the similarly named Dwarf-3 tags, this may change
+ in the future.
+ </p>
+
+ </p>
+ <p><pre>
+ <a name="tag_compile_unit">LLVM_COMPILE_UNIT</a> : 17
+ <a name="tag_subprogram">LLVM_SUBPROGRAM</a> : 46
+ <a name="tag_variable">LLVM_VARIABLE</a> : 52
+ <!-- <a name="tag_formal_parameter">LLVM_FORMAL_PARAMETER : 5-->
+ </pre></p>
+ </div>
+
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="ccxx_frontend">C/C++ front-end specific debug information</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ The C and C++ front-ends represent information about the program in a format
+ that is effectively identical to <a
+ href="http://www.eagercon.com/dwarf/dwarf3std.htm">Dwarf 3.0</a> in terms of
+ information content. This allows code generators to trivially support native
+ debuggers by generating standard dwarf information, and contains enough
+ information for non-dwarf targets to translate it as needed.</p>
+
+ <p>
+ The basic debug information required by the debugger is (intentionally) designed
+ to be as minimal as possible. This basic information is so minimal that it is
+ unlikely that <b>any</b> source-language could be adequately described by it.
+ Because of this, the debugger format was designed for extension to support
+ source-language-specific information. The extended descriptors are read and
+ interpreted by the <a href="#arch_info">language-specific</a> modules in the
+ debugger if there is support available, otherwise it is ignored.
+ </p>
+
+ <p>
+ This section describes the extensions used to represent C and C++ programs.
+ Other languages could pattern themselves after this (which itself is tuned to
+ representing programs in the same way that Dwarf 3 does), or they could choose
+ to provide completely different extensions if they don't fit into the Dwarf
+ model. As support for debugging information gets added to the various LLVM
+ source-language front-ends, the information used should be documented here.
+ </p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="ccxx_pse">Program Scope Entries</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+
+ </p>
+ </div>
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="ccxx_compilation_units">Compilation unit entries</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ Translation units do not add any information over the standard <a
+ href="#format_common_source_files">source file representation</a> already
+ expected by the debugger. As such, it uses descriptors of the type specified,
+ with a trailing <a href="#format_common_anchors">anchor</a>.
+ </p>
+ </div>
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="ccxx_modules">Module, namespace, and importing entries</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+
+ </p>
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="ccxx_dataobjects">Data objects (program variables)</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+
+ </p>
+ </div>
+
+
+ <!-- *********************************************************************** -->
+ <hr>
+ <div class="doc_footer">
+ <address><a href="mailto:sabre at nondot.org">Chris Lattner</a></address>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </div>
+
+ </body>
+ </html>
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
+ <html>
+ <head>
+ <title>Stacker: An Example Of Using LLVM</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+ <div class="doc_title">Stacker: An Example Of Using LLVM</div>
+ <hr>
+ <ol>
+ <li><a href="#abstract">Abstract</a></li>
+ <li><a href="#introduction">Introduction</a></li>
+ <li><a href="#lessons">Lessons I Learned About LLVM</a>
+ <ol>
+ <li><a href="#value">Everything's a Value!</a></li>
+ <li><a href="#terminate">Terminate Those Blocks!</a></li>
+ <li><a href="#blocks">Concrete Blocks</a></li>
+ <li><a href="#push_back">push_back Is Your Friend</a></li>
+ <li><a href="#gep">The Wily GetElementPtrInst</a></li>
+ <li><a href="#linkage">Getting Linkage Types Right</a></li>
+ <li><a href="#constants">Constants Are Easier Than That!</a></li>
+ </ol>
+ </li>
+ <li><a href="#lexicon">The Stacker Lexicon</a>
+ <ol>
+ <li><a href="#stack">The Stack</a>
+ <li><a href="#punctuation">Punctuation</a>
+ <li><a href="#comments">Comments</a>
+ <li><a href="#literals">Literals</a>
+ <li><a href="#words">Words</a>
+ <li><a href="style">Standard Style</a>
+ <li><a href="#builtins">Built-Ins</a>
+ </ol>
+ </li>
+ <li><a href="#example">Prime: A Complete Example</a></li>
+ <li><a href="#internal">Internal Code Details</a>
+ <ol>
+ <li><a href="#directory">The Directory Structure </a></li>
+ <li><a href="#lexer">The Lexer</a></li>
+ <li><a href="#parser">The Parser</a></li>
+ <li><a href="#compiler">The Compiler</a></li>
+ <li><a href="#runtime">The Runtime</a></li>
+ <li><a href="#driver">Compiler Driver</a></li>
+ <li><a href="#tests">Test Programs</a></li>
+ <li><a href="#exercise">Exercise</a></li>
+ <li><a href="#todo">Things Remaining To Be Done</a></li>
+ </ol>
+ </li>
+ </ol>
+ <div class="doc_text">
+ <p><b>Written by <a href="mailto:rspencer at x10sys.com">Reid Spencer</a> </b></p>
+ <p> </p>
+ </div>
+ <hr>
+ <!-- ======================================================================= -->
+ <div class="doc_section"> <a name="abstract">Abstract </a></div>
+ <div class="doc_text">
+ <p>This document is another way to learn about LLVM. Unlike the
+ <a href="LangRef.html">LLVM Reference Manual</a> or
+ <a href="ProgrammersManual.html">LLVM Programmer's Manual</a>, here we learn
+ about LLVM through the experience of creating a simple programming language
+ named Stacker. Stacker was invented specifically as a demonstration of
+ LLVM. The emphasis in this document is not on describing the
+ intricacies of LLVM itself but on how to use it to build your own
+ compiler system.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_section"> <a name="introduction">Introduction</a> </div>
+ <div class="doc_text">
+ <p>Amongst other things, LLVM is a platform for compiler writers.
+ Because of its exceptionally clean and small IR (intermediate
+ representation), compiler writing with LLVM is much easier than with
+ other system. As proof, I wrote the entire compiler (language definition,
+ lexer, parser, code generator, etc.) in about <em>four days</em>!
+ That's important to know because it shows how quickly you can get a new
+ language running when using LLVM. Furthermore, this was the <em >first</em>
+ language the author ever created using LLVM. The learning curve is
+ included in that four days.</p>
+ <p>The language described here, Stacker, is Forth-like. Programs
+ are simple collections of word definitions, and the only thing definitions
+ can do is manipulate a stack or generate I/O. Stacker is not a "real"
+ programming language; it's very simple. Although it is computationally
+ complete, you wouldn't use it for your next big project. However,
+ the fact that it is complete, it's simple, and it <em>doesn't</em> have
+ a C-like syntax make it useful for demonstration purposes. It shows
+ that LLVM could be applied to a wide variety of languages.</p>
+ <p>The basic notions behind stacker is very simple. There's a stack of
+ integers (or character pointers) that the program manipulates. Pretty
+ much the only thing the program can do is manipulate the stack and do
+ some limited I/O operations. The language provides you with several
+ built-in words that manipulate the stack in interesting ways. To get
+ your feet wet, here's how you write the traditional "Hello, World"
+ program in Stacker:</p>
+ <p><code>: hello_world "Hello, World!" >s DROP CR ;<br>
+ : MAIN hello_world ;<br></code></p>
+ <p>This has two "definitions" (Stacker manipulates words, not
+ functions and words have definitions): <code>MAIN</code> and <code>
+ hello_world</code>. The <code>MAIN</code> definition is standard; it
+ tells Stacker where to start. Here, <code>MAIN</code> is defined to
+ simply invoke the word <code>hello_world</code>. The
+ <code>hello_world</code> definition tells stacker to push the
+ <code>"Hello, World!"</code> string on to the stack, print it out
+ (<code>>s</code>), pop it off the stack (<code>DROP</code>), and
+ finally print a carriage return (<code>CR</code>). Although
+ <code>hello_world</code> uses the stack, its net effect is null. Well
+ written Stacker definitions have that characteristic. </p>
+ <p>Exercise for the reader: how could you make this a one line program?</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_section"><a name="lessons"></a>Lessons I Learned About LLVM</div>
+ <div class="doc_text">
+ <p>Stacker was written for two purposes: </p>
+ <ol>
+ <li>to get the author over the learning curve, and</li>
+ <li>to provide a simple example of how to write a compiler using LLVM.</li>
+ </ol>
+ <p>During the development of Stacker, many lessons about LLVM were
+ learned. Those lessons are described in the following subsections.<p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="value"></a>Everything's a Value!</div>
+ <div class="doc_text">
+ <p>Although I knew that LLVM uses a Single Static Assignment (SSA) format,
+ it wasn't obvious to me how prevalent this idea was in LLVM until I really
+ started using it. Reading the <a href="ProgrammersManual.html">
+ Programmer's Manual</a> and <a href="LangRef.html">Language Reference</a>,
+ I noted that most of the important LLVM IR (Intermediate Representation) C++
+ classes were derived from the Value class. The full power of that simple
+ design only became fully understood once I started constructing executable
+ expressions for Stacker.</p>
+ <p>This really makes your programming go faster. Think about compiling code
+ for the following C/C++ expression: <code>(a|b)*((x+1)/(y+1))</code>. Assuming
+ the values are on the stack in the order a, b, x, y, this could be
+ expressed in stacker as: <code>1 + SWAP 1 + / ROT2 OR *</code>.
+ You could write a function using LLVM that computes this expression like this: </p>
+ <pre><code>
+ Value*
+ expression(BasicBlock* bb, Value* a, Value* b, Value* x, Value* y )
+ {
+ Instruction* tail = bb->getTerminator();
+ ConstantSInt* one = ConstantSInt::get( Type::IntTy, 1);
+ BinaryOperator* or1 =
+ BinaryOperator::create( Instruction::Or, a, b, "", tail );
+ BinaryOperator* add1 =
+ BinaryOperator::create( Instruction::Add, x, one, "", tail );
+ BinaryOperator* add2 =
+ BinaryOperator::create( Instruction::Add, y, one, "", tail );
+ BinaryOperator* div1 =
+ BinaryOperator::create( Instruction::Div, add1, add2, "", tail);
+ BinaryOperator* mult1 =
+ BinaryOperator::create( Instruction::Mul, or1, div1, "", tail );
+
+ return mult1;
+ }
+ </code></pre>
+ <p>"Okay, big deal," you say? It is a big deal. Here's why. Note that I didn't
+ have to tell this function which kinds of Values are being passed in. They could be
+ <code>Instruction</code>s, <code>Constant</code>s, <code>GlobalVariable</code>s, or
+ any of the other subclasses of <code>Value</code> that LLVM supports.
+ Furthermore, if you specify Values that are incorrect for this sequence of
+ operations, LLVM will either notice right away (at compilation time) or the LLVM
+ Verifier will pick up the inconsistency when the compiler runs. In either case
+ LLVM prevents you from making a type error that gets passed through to the
+ generated program. This <em>really</em> helps you write a compiler that
+ always generates correct code!<p>
+ <p>The second point is that we don't have to worry about branching, registers,
+ stack variables, saving partial results, etc. The instructions we create
+ <em>are</em> the values we use. Note that all that was created in the above
+ code is a Constant value and five operators. Each of the instructions <em>is</em>
+ the resulting value of that instruction. This saves a lot of time.</p>
+ <p>The lesson is this: <em>SSA form is very powerful: there is no difference
+ between a value and the instruction that created it.</em> This is fully
+ enforced by the LLVM IR. Use it to your best advantage.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="terminate"></a>Terminate Those Blocks!</div>
+ <div class="doc_text">
+ <p>I had to learn about terminating blocks the hard way: using the debugger
+ to figure out what the LLVM verifier was trying to tell me and begging for
+ help on the LLVMdev mailing list. I hope you avoid this experience.</p>
+ <p>Emblazon this rule in your mind:</p>
+ <ul>
+ <li><em>All</em> <code>BasicBlock</code>s in your compiler <b>must</b> be
+ terminated with a terminating instruction (branch, return, etc.).
+ </li>
+ </ul>
+ <p>Terminating instructions are a semantic requirement of the LLVM IR. There
+ is no facility for implicitly chaining together blocks placed into a function
+ in the order they occur. Indeed, in the general case, blocks will not be
+ added to the function in the order of execution because of the recursive
+ way compilers are written.</p>
+ <p>Furthermore, if you don't terminate your blocks, your compiler code will
+ compile just fine. You won't find out about the problem until you're running
+ the compiler and the module you just created fails on the LLVM Verifier.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="blocks"></a>Concrete Blocks</div>
+ <div class="doc_text">
+ <p>After a little initial fumbling around, I quickly caught on to how blocks
+ should be constructed. In general, here's what I learned:
+ <ol>
+ <li><em>Create your blocks early.</em> While writing your compiler, you
+ will encounter several situations where you know apriori that you will
+ need several blocks. For example, if-then-else, switch, while, and for
+ statements in C/C++ all need multiple blocks for expression in LVVM.
+ The rule is, create them early.</li>
+ <li><em>Terminate your blocks early.</em> This just reduces the chances
+ that you forget to terminate your blocks which is required (go
+ <a href="#terminate">here</a> for more).
+ <li><em>Use getTerminator() for instruction insertion.</em> I noticed early on
+ that many of the constructors for the Instruction classes take an optional
+ <code>insert_before</code> argument. At first, I thought this was a mistake
+ because clearly the normal mode of inserting instructions would be one at
+ a time <em>after</em> some other instruction, not <em>before</em>. However,
+ if you hold on to your terminating instruction (or use the handy dandy
+ <code>getTerminator()</code> method on a <code>BasicBlock</code>), it can
+ always be used as the <code>insert_before</code> argument to your instruction
+ constructors. This causes the instruction to automatically be inserted in
+ the RightPlace™ place, just before the terminating instruction. The
+ nice thing about this design is that you can pass blocks around and insert
+ new instructions into them without ever knowing what instructions came
+ before. This makes for some very clean compiler design.</li>
+ </ol>
+ <p>The foregoing is such an important principal, its worth making an idiom:</p>
+ <pre><code>
+ BasicBlock* bb = new BasicBlock();</li>
+ bb->getInstList().push_back( new Branch( ... ) );
+ new Instruction(..., bb->getTerminator() );
+ </code></pre>
+ <p>To make this clear, consider the typical if-then-else statement
+ (see StackerCompiler::handle_if() method). We can set this up
+ in a single function using LLVM in the following way: </p>
+ <pre>
+ using namespace llvm;
+ BasicBlock*
+ MyCompiler::handle_if( BasicBlock* bb, SetCondInst* condition )
+ {
+ // Create the blocks to contain code in the structure of if/then/else
+ BasicBlock* then_bb = new BasicBlock();
+ BasicBlock* else_bb = new BasicBlock();
+ BasicBlock* exit_bb = new BasicBlock();
+
+ // Insert the branch instruction for the "if"
+ bb->getInstList().push_back( new BranchInst( then_bb, else_bb, condition ) );
+
+ // Set up the terminating instructions
+ then->getInstList().push_back( new BranchInst( exit_bb ) );
+ else->getInstList().push_back( new BranchInst( exit_bb ) );
+
+ // Fill in the then part .. details excised for brevity
+ this->fill_in( then_bb );
+
+ // Fill in the else part .. details excised for brevity
+ this->fill_in( else_bb );
+
+ // Return a block to the caller that can be filled in with the code
+ // that follows the if/then/else construct.
+ return exit_bb;
+ }
+ </pre>
+ <p>Presumably in the foregoing, the calls to the "fill_in" method would add
+ the instructions for the "then" and "else" parts. They would use the third part
+ of the idiom almost exclusively (inserting new instructions before the
+ terminator). Furthermore, they could even recurse back to <code>handle_if</code>
+ should they encounter another if/then/else statement, and it will just work.</p>
+ <p>Note how cleanly this all works out. In particular, the push_back methods on
+ the <code>BasicBlock</code>'s instruction list. These are lists of type
+ <code>Instruction</code> (which is also of type <code>Value</code>). To create
+ the "if" branch we merely instantiate a <code>BranchInst</code> that takes as
+ arguments the blocks to branch to and the condition to branch on. The
+ <code>BasicBlock</code> objects act like branch labels! This new
+ <code>BranchInst</code> terminates the <code>BasicBlock</code> provided
+ as an argument. To give the caller a way to keep inserting after calling
+ <code>handle_if</code>, we create an <code>exit_bb</code> block which is
+ returned
+ to the caller. Note that the <code>exit_bb</code> block is used as the
+ terminator for both the <code>then_bb</code> and the <code>else_bb</code>
+ blocks. This guarantees that no matter what else <code>handle_if</code>
+ or <code>fill_in</code> does, they end up at the <code>exit_bb</code> block.
+ </p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="push_back"></a>push_back Is Your Friend</div>
+ <div class="doc_text">
+ <p>
+ One of the first things I noticed is the frequent use of the "push_back"
+ method on the various lists. This is so common that it is worth mentioning.
+ The "push_back" inserts a value into an STL list, vector, array, etc. at the
+ end. The method might have also been named "insert_tail" or "append".
+ Although I've used STL quite frequently, my use of push_back wasn't very
+ high in other programs. In LLVM, you'll use it all the time.
+ </p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="gep"></a>The Wily GetElementPtrInst</div>
+ <div class="doc_text">
+ <p>
+ It took a little getting used to and several rounds of postings to the LLVM
+ mailing list to wrap my head around this instruction correctly. Even though I had
+ read the Language Reference and Programmer's Manual a couple times each, I still
+ missed a few <em>very</em> key points:
+ </p>
+ <ul>
+ <li>GetElementPtrInst gives you back a Value for the last thing indexed.</em>
+ <li>All global variables in LLVM are <em>pointers</em>.
+ <li>Pointers must also be dereferenced with the GetElementPtrInst instruction.
+ </ul>
+ <p>This means that when you look up an element in the global variable (assuming
+ it's a struct or array), you <em>must</em> deference the pointer first! For many
+ things, this leads to the idiom:
+ </p>
+ <pre><code>
+ std::vector<Value*> index_vector;
+ index_vector.push_back( ConstantSInt::get( Type::LongTy, 0 );
+ // ... push other indices ...
+ GetElementPtrInst* gep = new GetElementPtrInst( ptr, index_vector );
+ </code></pre>
+ <p>For example, suppose we have a global variable whose type is [24 x int]. The
+ variable itself represents a <em>pointer</em> to that array. To subscript the
+ array, we need two indices, not just one. The first index (0) dereferences the
+ pointer. The second index subscripts the array. If you're a "C" programmer, this
+ will run against your grain because you'll naturally think of the global array
+ variable and the address of its first element as the same. That tripped me up
+ for a while until I realized that they really do differ .. by <em>type</em>.
+ Remember that LLVM is strongly typed. Everything has a type.
+ The "type" of the global variable is [24 x int]*. That is, it's
+ a pointer to an array of 24 ints. When you dereference that global variable with
+ a single (0) index, you now have a "[24 x int]" type. Although
+ the pointer value of the dereferenced global and the address of the zero'th element
+ in the array will be the same, they differ in their type. The zero'th element has
+ type "int" while the pointer value has type "[24 x int]".</p>
+ <p>Get this one aspect of LLVM right in your head, and you'll save yourself
+ a lot of compiler writing headaches down the road.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="linkage"></a>Getting Linkage Types Right</div>
+ <div class="doc_text">
+ <p>Linkage types in LLVM can be a little confusing, especially if your compiler
+ writing mind has affixed firm concepts to particular words like "weak",
+ "external", "global", "linkonce", etc. LLVM does <em>not</em> use the precise
+ definitions of, say, ELF or GCC, even though they share common terms. To be fair,
+ the concepts are related and similar but not precisely the same. This can lead
+ you to think you know what a linkage type represents but in fact it is slightly
+ different. I recommend you read the
+ <a href="LangRef.html#linkage"> Language Reference on this topic</a> very
+ carefully. Then, read it again.<p>
+ <p>Here are some handy tips that I discovered along the way:</p>
+ <ul>
+ <li><em>Uninitialized means external.</em> That is, the symbol is declared in the current
+ module and can be used by that module, but it is not defined by that module.</li>
+ <li><em>Setting an initializer changes a global' linkage type.</em> Setting an
+ initializer changes a global's linkage type from whatever it was to a normal,
+ defined global (not external). You'll need to call the setLinkage() method to
+ reset it if you specify the initializer after the GlobalValue has been constructed.
+ This is important for LinkOnce and Weak linkage types.</li>
+ <li><em>Appending linkage can keep track of things.</em> Appending linkage can
+ be used to keep track of compilation information at runtime. It could be used,
+ for example, to build a full table of all the C++ virtual tables or hold the
+ C++ RTTI data, or whatever. Appending linkage can only be applied to arrays.
+ All arrays with the same name in each module are concatenated together at link
+ time.</li>
+ </ul>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="constants"></a>Constants Are Easier Than That!</div>
+ <div class="doc_text">
+ <p>
+ Constants in LLVM took a little getting used to until I discovered a few utility
+ functions in the LLVM IR that make things easier. Here's what I learned: </p>
+ <ul>
+ <li>Constants are Values like anything else and can be operands of instructions</li>
+ <li>Integer constants, frequently needed, can be created using the static "get"
+ methods of the ConstantInt, ConstantSInt, and ConstantUInt classes. The nice thing
+ about these is that you can "get" any kind of integer quickly.</li>
+ <li>There's a special method on Constant class which allows you to get the null
+ constant for <em>any</em> type. This is really handy for initializing large
+ arrays or structures, etc.</li>
+ </ul>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_section"> <a name="lexicon">The Stacker Lexicon</a></div>
+ <div class="doc_text"><p>This section describes the Stacker language</p></div>
+ <div class="doc_subsection"><a name="stack"></a>The Stack</div>
+ <div class="doc_text">
+ <p>Stacker definitions define what they do to the global stack. Before
+ proceeding, a few words about the stack are in order. The stack is simply
+ a global array of 32-bit integers or pointers. A global index keeps track
+ of the location of the top of the stack. All of this is hidden from the
+ programmer, but it needs to be noted because it is the foundation of the
+ conceptual programming model for Stacker. When you write a definition,
+ you are, essentially, saying how you want that definition to manipulate
+ the global stack.</p>
+ <p>Manipulating the stack can be quite hazardous. There is no distinction
+ given and no checking for the various types of values that can be placed
+ on the stack. Automatic coercion between types is performed. In many
+ cases, this is useful. For example, a boolean value placed on the stack
+ can be interpreted as an integer with good results. However, using a
+ word that interprets that boolean value as a pointer to a string to
+ print out will almost always yield a crash. Stacker simply leaves it
+ to the programmer to get it right without any interference or hindering
+ on interpretation of the stack values. You've been warned. :) </p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="punctuation"></a>Punctuation</div>
+ <div class="doc_text">
+ <p>Punctuation in Stacker is very simple. The colon and semi-colon
+ characters are used to introduce and terminate a definition
+ (respectively). Except for <em>FORWARD</em> declarations, definitions
+ are all you can specify in Stacker. Definitions are read left to right.
+ Immediately after the colon comes the name of the word being defined.
+ The remaining words in the definition specify what the word does. The definition
+ is terminated by a semi-colon.</p>
+ <p>So, your typical definition will have the form:</p>
+ <pre><code>: name ... ;</code></pre>
+ <p>The <code>name</code> is up to you but it must start with a letter and contain
+ only letters, numbers, and underscore. Names are case sensitive and must not be
+ the same as the name of a built-in word. The <code>...</code> is replaced by
+ the stack manipulating words that you wish to define <code>name</code> as. <p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="comments"></a>Comments</div>
+ <div class="doc_text">
+ <p>Stacker supports two types of comments. A hash mark (#) starts a comment
+ that extends to the end of the line. It is identical to the kind of comments
+ commonly used in shell scripts. A pair of parentheses also surround a comment.
+ In both cases, the content of the comment is ignored by the Stacker compiler. The
+ following does nothing in Stacker.
+ </p>
+ <pre><code>
+ # This is a comment to end of line
+ ( This is an enclosed comment )
+ </code></pre>
+ <p>See the <a href="#example">example</a> program to see comments in use in
+ a real program.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="literals"></a>Literals</div>
+ <div class="doc_text">
+ <p>There are three kinds of literal values in Stacker: Integers, Strings,
+ and Booleans. In each case, the stack operation is to simply push the
+ value on to the stack. So, for example:<br/>
+ <code> 42 " is the answer." TRUE </code><br/>
+ will push three values on to the stack: the integer 42, the
+ string " is the answer.", and the boolean TRUE.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="words"></a>Words</div>
+ <div class="doc_text">
+ <p>Each definition in Stacker is composed of a set of words. Words are
+ read and executed in order from left to right. There is very little
+ checking in Stacker to make sure you're doing the right thing with
+ the stack. It is assumed that the programmer knows how the stack
+ transformation he applies will affect the program.</p>
+ <p>Words in a definition come in two flavors: built-in and programmer
+ defined. Simply mentioning the name of a previously defined or declared
+ programmer-defined word causes that word's stack actions to be invoked. It
+ is somewhat like a function call in other languages. The built-in
+ words have various effects, described <a href="#builtins">below</a>.</p>
+ <p>Sometimes you need to call a word before it is defined. For this, you can
+ use the <code>FORWARD</code> declaration. It looks like this:</p>
+ <p><code>FORWARD name ;</code></p>
+ <p>This simply states to Stacker that "name" is the name of a definition
+ that is defined elsewhere. Generally it means the definition can be found
+ "forward" in the file. But, it doesn't have to be in the current compilation
+ unit. Anything declared with <code>FORWARD</code> is an external symbol for
+ linking.</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="builtins"></a>Built In Words</div>
+ <div class="doc_text">
+ <p>The built-in words of the Stacker language are put in several groups
+ depending on what they do. The groups are as follows:</p>
+ <ol>
+ <li><em>Logical</em>: These words provide the logical operations for
+ comparing stack operands.<br/>The words are: < > <= >=
+ = <> true false.</li>
+ <li><em>Bitwise</em>: These words perform bitwise computations on
+ their operands. <br/> The words are: << >> XOR AND NOT</li>
+ <li><em>Arithmetic</em>: These words perform arithmetic computations on
+ their operands. <br/> The words are: ABS NEG + - * / MOD */ ++ -- MIN MAX</li>
+ <li><em>Stack</em>These words manipulate the stack directly by moving
+ its elements around.<br/> The words are: DROP DROP2 NIP NIP2 DUP DUP2
+ SWAP SWAP2 OVER OVER2 ROT ROT2 RROT RROT2 TUCK TUCK2 PICK SELECT ROLL</li>
+ <li><em>Memory</em>These words allocate, free, and manipulate memory
+ areas outside the stack.<br/>The words are: MALLOC FREE GET PUT</li>
+ <li><em>Control</em>: These words alter the normal left to right flow
+ of execution.<br/>The words are: IF ELSE ENDIF WHILE END RETURN EXIT RECURSE</li>
+ <li><em>I/O</em>: These words perform output on the standard output
+ and input on the standard input. No other I/O is possible in Stacker.
+ <br/>The words are: SPACE TAB CR >s >d >c <s <d <c.</li>
+ </ol>
+ <p>While you may be familiar with many of these operations from other
+ programming languages, a careful review of their semantics is important
+ for correct programming in Stacker. Of most importance is the effect
+ that each of these built-in words has on the global stack. The effect is
+ not always intuitive. To better describe the effects, we'll borrow from Forth the idiom of
+ describing the effect on the stack with:</p>
+ <p><code> BEFORE -- AFTER </code></p>
+ <p>That is, to the left of the -- is a representation of the stack before
+ the operation. To the right of the -- is a representation of the stack
+ after the operation. In the table below that describes the operation of
+ each of the built in words, we will denote the elements of the stack
+ using the following construction:</p>
+ <ol>
+ <li><em>b</em> - a boolean truth value</li>
+ <li><em>w</em> - a normal integer valued word.</li>
+ <li><em>s</em> - a pointer to a string value</li>
+ <li><em>p</em> - a pointer to a malloc'd memory block</li>
+ </ol>
+ </div>
+ <div class="doc_text" >
+ <table class="doc_table" style="border: 2px solid blue; border-collapse: collapse;" >
+ <tr class="doc_table"><td colspan="4" style="border: 2px solid blue">Definition Of Operation Of Built In Words</td></tr>
+ <tr class="doc_table"><td colspan="4" style="border: 2px solid blue"><b>LOGICAL OPERATIONS</b></td></tr>
+ <tr class="doc_table">
+ <td style="border: 2px solid blue"><u>Word</u></td>
+ <td style="border: 2px solid blue"><u>Name</u></td>
+ <td style="border: 2px solid blue"><u>Operation</u></td>
+ <td style="border: 2px solid blue"><u>Description</u></td>
+ </tr>
+ <tr class="doc_table"><td style="border: 2px solid blue"><</td>
+ <td style="border: 2px solid blue">LT</td>
+ <td style="border: 2px solid blue">w1 w2 -- b</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+ compared. If w1 is less than w2, TRUE is pushed back on
+ the stack, otherwise FALSE is pushed back on the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">></td>
+ <td style="border: 2px solid blue">GT</td>
+ <td style="border: 2px solid blue">w1 w2 -- b</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+ compared. If w1 is greater than w2, TRUE is pushed back on
+ the stack, otherwise FALSE is pushed back on the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">>=</td>
+ <td style="border: 2px solid blue">GE</td>
+ <td style="border: 2px solid blue">w1 w2 -- b</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+ compared. If w1 is greater than or equal to w2, TRUE is
+ pushed back on the stack, otherwise FALSE is pushed back
+ on the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"><=</td>
+ <td style="border: 2px solid blue">LE</td>
+ <td style="border: 2px solid blue">w1 w2 -- b</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+ compared. If w1 is less than or equal to w2, TRUE is
+ pushed back on the stack, otherwise FALSE is pushed back
+ on the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">=</td>
+ <td style="border: 2px solid blue">EQ</td>
+ <td style="border: 2px solid blue">w1 w2 -- b</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+ compared. If w1 is equal to w2, TRUE is
+ pushed back on the stack, otherwise FALSE is pushed back
+ </td>
+ </tr>
+ <tr><td style="border: 2px solid blue"><></td>
+ <td style="border: 2px solid blue">NE</td>
+ <td style="border: 2px solid blue">w1 w2 -- b</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+ compared. If w1 is equal to w2, TRUE is
+ pushed back on the stack, otherwise FALSE is pushed back
+ </td>
+ </tr>
+ <tr><td style="border: 2px solid blue">FALSE</td>
+ <td style="border: 2px solid blue">FALSE</td>
+ <td style="border: 2px solid blue"> -- b</td>
+ <td style="border: 2px solid blue">The boolean value FALSE (0) is pushed on to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">TRUE</td>
+ <td style="border: 2px solid blue">TRUE</td>
+ <td style="border: 2px solid blue"> -- b</td>
+ <td style="border: 2px solid blue">The boolean value TRUE (-1) is pushed on to the stack.</td>
+ </tr>
+ <tr><td colspan="4"><b>BITWISE OPERATORS</b></td></tr>
+ <tr>
+ <td style="border: 2px solid blue"><u>Word</u></td>
+ <td style="border: 2px solid blue"><u>Name</u></td>
+ <td style="border: 2px solid blue"><u>Operation</u></td>
+ <td style="border: 2px solid blue"><u>Description</u></td>
+ </tr>
+ <tr><td style="border: 2px solid blue"><<</td>
+ <td style="border: 2px solid blue">SHL</td>
+ <td style="border: 2px solid blue">w1 w2 -- w1<<w2</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The w2
+ operand is shifted left by the number of bits given by the
+ w1 operand. The result is pushed back to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">>></td>
+ <td style="border: 2px solid blue">SHR</td>
+ <td style="border: 2px solid blue">w1 w2 -- w1>>w2</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The w2
+ operand is shifted right by the number of bits given by the
+ w1 operand. The result is pushed back to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">OR</td>
+ <td style="border: 2px solid blue">OR</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2|w1</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The values
+ are bitwise OR'd together and pushed back on the stack. This is
+ not a logical OR. The sequence 1 2 OR yields 3 not 1.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">AND</td>
+ <td style="border: 2px solid blue">AND</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2&w1</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The values
+ are bitwise AND'd together and pushed back on the stack. This is
+ not a logical AND. The sequence 1 2 AND yields 0 not 1.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">XOR</td>
+ <td style="border: 2px solid blue">XOR</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2^w1</td>
+ <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The values
+ are bitwise exclusive OR'd together and pushed back on the stack.
+ For example, The sequence 1 3 XOR yields 2.</td>
+ </tr>
+ <tr><td colspan="4"><b>ARITHMETIC OPERATORS</b></td></tr>
+ <tr>
+ <td style="border: 2px solid blue"><u>Word</u></td>
+ <td style="border: 2px solid blue"><u>Name</u></td>
+ <td style="border: 2px solid blue"><u>Operation</u></td>
+ <td style="border: 2px solid blue"><u>Description</u></td>
+ </tr>
+ <tr><td style="border: 2px solid blue">ABS</td>
+ <td style="border: 2px solid blue">ABS</td>
+ <td style="border: 2px solid blue">w -- |w|</td>
+ <td style="border: 2px solid blue">One value s popped off the stack; its absolute value is computed
+ and then pushed on to the stack. If w1 is -1 then w2 is 1. If w1 is
+ 1 then w2 is also 1.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">NEG</td>
+ <td style="border: 2px solid blue">NEG</td>
+ <td style="border: 2px solid blue">w -- -w</td>
+ <td style="border: 2px solid blue">One value is popped off the stack which is negated and then
+ pushed back on to the stack. If w1 is -1 then w2 is 1. If w1 is
+ 1 then w2 is -1.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"> + </td>
+ <td style="border: 2px solid blue">ADD</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2+w1</td>
+ <td style="border: 2px solid blue">Two values are popped off the stack. Their sum is pushed back
+ on to the stack</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"> - </td>
+ <td style="border: 2px solid blue">SUB</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2-w1</td>
+ <td style="border: 2px solid blue">Two values are popped off the stack. Their difference is pushed back
+ on to the stack</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"> * </td>
+ <td style="border: 2px solid blue">MUL</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2*w1</td>
+ <td style="border: 2px solid blue">Two values are popped off the stack. Their product is pushed back
+ on to the stack</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"> / </td>
+ <td style="border: 2px solid blue">DIV</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2/w1</td>
+ <td style="border: 2px solid blue">Two values are popped off the stack. Their quotient is pushed back
+ on to the stack</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">MOD</td>
+ <td style="border: 2px solid blue">MOD</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2%w1</td>
+ <td style="border: 2px solid blue">Two values are popped off the stack. Their remainder after division
+ of w1 by w2 is pushed back on to the stack</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"> */ </td>
+ <td style="border: 2px solid blue">STAR_SLAH</td>
+ <td style="border: 2px solid blue">w1 w2 w3 -- (w3*w2)/w1</td>
+ <td style="border: 2px solid blue">Three values are popped off the stack. The product of w1 and w2 is
+ divided by w3. The result is pushed back on to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"> ++ </td>
+ <td style="border: 2px solid blue">INCR</td>
+ <td style="border: 2px solid blue">w -- w+1</td>
+ <td style="border: 2px solid blue">One value is popped off the stack. It is incremented by one and then
+ pushed back on to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">DECR</td>
+ <td style="border: 2px solid blue">w -- w-1</td>
+ <td style="border: 2px solid blue">One value is popped off the stack. It is decremented by one and then
+ pushed back on to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">MIN</td>
+ <td style="border: 2px solid blue">MIN</td>
+ <td style="border: 2px solid blue">w1 w2 -- (w2<w1?w2:w1)</td>
+ <td style="border: 2px solid blue">Two values are popped off the stack. The larger one is pushed back
+ on to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">MAX</td>
+ <td style="border: 2px solid blue">MAX</td>
+ <td style="border: 2px solid blue">w1 w2 -- (w2>w1?w2:w1)</td>
+ <td style="border: 2px solid blue">Two values are popped off the stack. The larger value is pushed back
+ on to the stack.</td>
+ </tr>
+ <tr><td colspan="4"><b>STACK MANIPULATION OPERATORS</b></td></tr>
+ <tr>
+ <td style="border: 2px solid blue"><u>Word</u></td>
+ <td style="border: 2px solid blue"><u>Name</u></td>
+ <td style="border: 2px solid blue"><u>Operation</u></td>
+ <td style="border: 2px solid blue"><u>Description</u></td>
+ </tr>
+ <tr><td style="border: 2px solid blue">DROP</td>
+ <td style="border: 2px solid blue">DROP</td>
+ <td style="border: 2px solid blue">w -- </td>
+ <td style="border: 2px solid blue">One value is popped off the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">DROP2</td>
+ <td style="border: 2px solid blue">DROP2</td>
+ <td style="border: 2px solid blue">w1 w2 -- </td>
+ <td style="border: 2px solid blue">Two values are popped off the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">NIP</td>
+ <td style="border: 2px solid blue">NIP</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2</td>
+ <td style="border: 2px solid blue">The second value on the stack is removed from the stack. That is,
+ a value is popped off the stack and retained. Then a second value is
+ popped and the retained value is pushed.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">NIP2</td>
+ <td style="border: 2px solid blue">NIP2</td>
+ <td style="border: 2px solid blue">w1 w2 w3 w4 -- w3 w4</td>
+ <td style="border: 2px solid blue">The third and fourth values on the stack are removed from it. That is,
+ two values are popped and retained. Then two more values are popped and
+ the two retained values are pushed back on.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">DUP</td>
+ <td style="border: 2px solid blue">DUP</td>
+ <td style="border: 2px solid blue">w1 -- w1 w1</td>
+ <td style="border: 2px solid blue">One value is popped off the stack. That value is then pushed on to
+ the stack twice to duplicate the top stack vaue.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">DUP2</td>
+ <td style="border: 2px solid blue">DUP2</td>
+ <td style="border: 2px solid blue">w1 w2 -- w1 w2 w1 w2</td>
+ <td style="border: 2px solid blue">The top two values on the stack are duplicated. That is, two vaues
+ are popped off the stack. They are alternately pushed back on the
+ stack twice each.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">SWAP</td>
+ <td style="border: 2px solid blue">SWAP</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2 w1</td>
+ <td style="border: 2px solid blue">The top two stack items are reversed in their order. That is, two
+ values are popped off the stack and pushed back on to the stack in
+ the opposite order they were popped.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">SWAP2</td>
+ <td style="border: 2px solid blue">SWAP2</td>
+ <td style="border: 2px solid blue">w1 w2 w3 w4 -- w3 w4 w2 w1</td>
+ <td style="border: 2px solid blue">The top four stack items are swapped in pairs. That is, two values
+ are popped and retained. Then, two more values are popped and retained.
+ The values are pushed back on to the stack in the reverse order but
+ in pairs.</p>
+ </tr>
+ <tr><td style="border: 2px solid blue">OVER</td>
+ <td style="border: 2px solid blue">OVER</td>
+ <td style="border: 2px solid blue">w1 w2-- w1 w2 w1</td>
+ <td style="border: 2px solid blue">Two values are popped from the stack. They are pushed back
+ on to the stack in the order w1 w2 w1. This seems to cause the
+ top stack element to be duplicated "over" the next value.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">OVER2</td>
+ <td style="border: 2px solid blue">OVER2</td>
+ <td style="border: 2px solid blue">w1 w2 w3 w4 -- w1 w2 w3 w4 w1 w2</td>
+ <td style="border: 2px solid blue">The third and fourth values on the stack are replicated on to the
+ top of the stack</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">ROT</td>
+ <td style="border: 2px solid blue">ROT</td>
+ <td style="border: 2px solid blue">w1 w2 w3 -- w2 w3 w1</td>
+ <td style="border: 2px solid blue">The top three values are rotated. That is, three value are popped
+ off the stack. They are pushed back on to the stack in the order
+ w1 w3 w2.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">ROT2</td>
+ <td style="border: 2px solid blue">ROT2</td>
+ <td style="border: 2px solid blue">w1 w2 w3 w4 w5 w6 -- w3 w4 w5 w6 w1 w2</td>
+ <td style="border: 2px solid blue">Like ROT but the rotation is done using three pairs instead of
+ three singles.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">RROT</td>
+ <td style="border: 2px solid blue">RROT</td>
+ <td style="border: 2px solid blue">w1 w2 w3 -- w2 w3 w1</td>
+ <td style="border: 2px solid blue">Reverse rotation. Like ROT, but it rotates the other way around.
+ Essentially, the third element on the stack is moved to the top
+ of the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">RROT2</td>
+ <td style="border: 2px solid blue">RROT2</td>
+ <td style="border: 2px solid blue">w1 w2 w3 w4 w5 w6 -- w3 w4 w5 w6 w1 w2</td>
+ <td style="border: 2px solid blue">Double reverse rotation. Like RROT but the rotation is done using
+ three pairs instead of three singles. The fifth and sixth stack
+ elements are moved to the first and second positions</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">TUCK</td>
+ <td style="border: 2px solid blue">TUCK</td>
+ <td style="border: 2px solid blue">w1 w2 -- w2 w1 w2</td>
+ <td style="border: 2px solid blue">Similar to OVER except that the second operand is being
+ replicated. Essentially, the first operand is being "tucked"
+ in between two instances of the second operand. Logically, two
+ values are popped off the stack. They are placed back on the
+ stack in the order w2 w1 w2.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">TUCK2</td>
+ <td style="border: 2px solid blue">TUCK2</td>
+ <td style="border: 2px solid blue">w1 w2 w3 w4 -- w3 w4 w1 w2 w3 w4</td>
+ <td style="border: 2px solid blue">Like TUCK but a pair of elements is tucked over two pairs.
+ That is, the top two elements of the stack are duplicated and
+ inserted into the stack at the fifth and positions.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">PICK</td>
+ <td style="border: 2px solid blue">PICK</td>
+ <td style="border: 2px solid blue">x0 ... Xn n -- x0 ... Xn x0</td>
+ <td style="border: 2px solid blue">The top of the stack is used as an index into the remainder of
+ the stack. The element at the nth position replaces the index
+ (top of stack). This is useful for cycling through a set of
+ values. Note that indexing is zero based. So, if n=0 then you
+ get the second item on the stack. If n=1 you get the third, etc.
+ Note also that the index is replaced by the n'th value. </td>
+ </tr>
+ <tr><td style="border: 2px solid blue">SELECT</td>
+ <td style="border: 2px solid blue">SELECT</td>
+ <td style="border: 2px solid blue">m n X0..Xm Xm+1 .. Xn -- Xm</td>
+ <td style="border: 2px solid blue">This is like PICK but the list is removed and you need to specify
+ both the index and the size of the list. Careful with this one,
+ the wrong value for n can blow away a huge amount of the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">ROLL</td>
+ <td style="border: 2px solid blue">ROLL</td>
+ <td style="border: 2px solid blue">x0 x1 .. xn n -- x1 .. xn x0</td>
+ <td style="border: 2px solid blue"><b>Not Implemented</b>. This one has been left as an exercise to
+ the student. See <a href="#exercise">Exercise</a>. ROLL requires
+ a value, "n", to be on the top of the stack. This value specifies how
+ far into the stack to "roll". The n'th value is <em>moved</em> (not
+ copied) from its location and replaces the "n" value on the top of the
+ stack. In this way, all the values between "n" and x0 roll up the stack.
+ The operation of ROLL is a generalized ROT. The "n" value specifies
+ how much to rotate. That is, ROLL with n=1 is the same as ROT and
+ ROLL with n=2 is the same as ROT2.</td>
+ </tr>
+ <tr><td colspan="4"><b>MEMORY OPERATORS</b></td></tr>
+ <tr>
+ <td style="border: 2px solid blue"><u>Word</u></td>
+ <td style="border: 2px solid blue"><u>Name</u></td>
+ <td style="border: 2px solid blue"><u>Operation</u></td>
+ <td style="border: 2px solid blue"><u>Description</u></td>
+ </tr>
+ <tr><td style="border: 2px solid blue">MALLOC</td>
+ <td style="border: 2px solid blue">MALLOC</td>
+ <td style="border: 2px solid blue">w1 -- p</td>
+ <td style="border: 2px solid blue">One value is popped off the stack. The value is used as the size
+ of a memory block to allocate. The size is in bytes, not words.
+ The memory allocation is completed and the address of the memory
+ block is pushed on to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">FREE</td>
+ <td style="border: 2px solid blue">FREE</td>
+ <td style="border: 2px solid blue">p -- </td>
+ <td style="border: 2px solid blue">One pointer value is popped off the stack. The value should be
+ the address of a memory block created by the MALLOC operation. The
+ associated memory block is freed. Nothing is pushed back on the
+ stack. Many bugs can be created by attempting to FREE something
+ that isn't a pointer to a MALLOC allocated memory block. Make
+ sure you know what's on the stack. One way to do this is with
+ the following idiom:<br/>
+ <code>64 MALLOC DUP DUP (use ptr) DUP (use ptr) ... FREE</code>
+ <br/>This ensures that an extra copy of the pointer is placed on
+ the stack (for the FREE at the end) and that every use of the
+ pointer is preceded by a DUP to retain the copy for FREE.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">GET</td>
+ <td style="border: 2px solid blue">GET</td>
+ <td style="border: 2px solid blue">w1 p -- w2 p</td>
+ <td style="border: 2px solid blue">An integer index and a pointer to a memory block are popped of
+ the block. The index is used to index one byte from the memory
+ block. That byte value is retained, the pointer is pushed again
+ and the retained value is pushed. Note that the pointer value
+ s essentially retained in its position so this doesn't count
+ as a "use ptr" in the FREE idiom.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">PUT</td>
+ <td style="border: 2px solid blue">PUT</td>
+ <td style="border: 2px solid blue">w1 w2 p -- p </td>
+ <td style="border: 2px solid blue">An integer value is popped of the stack. This is the value to
+ be put into a memory block. Another integer value is popped of
+ the stack. This is the indexed byte in the memory block. A
+ pointer to the memory block is popped off the stack. The
+ first value (w1) is then converted to a byte and written
+ to the element of the memory block(p) at the index given
+ by the second value (w2). The pointer to the memory block is
+ pushed back on the stack so this doesn't count as a "use ptr"
+ in the FREE idiom.</td>
+ </tr>
+ <tr><td colspan="4"><b>CONTROL FLOW OPERATORS</b></td></tr>
+ <tr>
+ <td style="border: 2px solid blue"><u>Word</u></td>
+ <td style="border: 2px solid blue"><u>Name</u></td>
+ <td style="border: 2px solid blue"><u>Operation</u></td>
+ <td style="border: 2px solid blue"><u>Description</u></td>
+ </tr>
+ <tr><td style="border: 2px solid blue">RETURN</td>
+ <td style="border: 2px solid blue">RETURN</td>
+ <td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">The currently executing definition returns immediately to its caller.
+ Note that there is an implicit <code>RETURN</code> at the end of each
+ definition, logically located at the semi-colon. The sequence
+ <code>RETURN ;</code> is valid but redundant.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">EXIT</td>
+ <td style="border: 2px solid blue">EXIT</td>
+ <td style="border: 2px solid blue">w1 -- </td>
+ <td style="border: 2px solid blue">A return value for the program is popped off the stack. The program is
+ then immediately terminated. This is normally an abnormal exit from the
+ program. For a normal exit (when <code>MAIN</code> finishes), the exit
+ code will always be zero in accordance with UNIX conventions.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">RECURSE</td>
+ <td style="border: 2px solid blue">RECURSE</td>
+ <td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">The currently executed definition is called again. This operation is
+ needed since the definition of a word doesn't exist until the semi colon
+ is reacher. Attempting something like:<br/>
+ <code> : recurser recurser ; </code><br/> will yield and error saying that
+ "recurser" is not defined yet. To accomplish the same thing, change this
+ to:<br/>
+ <code> : recurser RECURSE ; </code></td>
+ </tr>
+ <tr><td style="border: 2px solid blue">IF (words...) ENDIF</td>
+ <td style="border: 2px solid blue">IF (words...) ENDIF</td>
+ <td style="border: 2px solid blue">b -- </td>
+ <td style="border: 2px solid blue">A boolean value is popped of the stack. If it is non-zero then the "words..."
+ are executed. Otherwise, execution continues immediately following the ENDIF.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">IF (words...) ELSE (words...) ENDIF</td>
+ <td style="border: 2px solid blue">IF (words...) ELSE (words...) ENDIF</td>
+ <td style="border: 2px solid blue">b -- </td>
+ <td style="border: 2px solid blue">A boolean value is popped of the stack. If it is non-zero then the "words..."
+ between IF and ELSE are executed. Otherwise the words between ELSE and ENDIF are
+ executed. In either case, after the (words....) have executed, execution continues
+ immediately following the ENDIF. </td>
+ </tr>
+ <tr><td style="border: 2px solid blue">WHILE (words...) END</td>
+ <td style="border: 2px solid blue">WHILE (words...) END</td>
+ <td style="border: 2px solid blue">b -- b </td>
+ <td style="border: 2px solid blue">The boolean value on the top of the stack is examined. If it is non-zero then the
+ "words..." between WHILE and END are executed. Execution then begins again at the WHILE where another
+ boolean is popped off the stack. To prevent this operation from eating up the entire
+ stack, you should push on to the stack (just before the END) a boolean value that indicates
+ whether to terminate. Note that since booleans and integers can be coerced you can
+ use the following "for loop" idiom:<br/>
+ <code>(push count) WHILE (words...) -- END</code><br/>
+ For example:<br/>
+ <code>10 WHILE DUP >d -- END</code><br/>
+ This will print the numbers from 10 down to 1. 10 is pushed on the stack. Since that is
+ non-zero, the while loop is entered. The top of the stack (10) is duplicated and then
+ printed out with >d. The top of the stack is decremented, yielding 9 and control is
+ transfered back to the WHILE keyword. The process starts all over again and repeats until
+ the top of stack is decremented to 0 at which the WHILE test fails and control is
+ transfered to the word after the END.</td>
+ </tr>
+ <tr><td colspan="4"><b>INPUT & OUTPUT OPERATORS</b></td></tr>
+ <tr>
+ <td style="border: 2px solid blue"><u>Word</u></td>
+ <td style="border: 2px solid blue"><u>Name</u></td>
+ <td style="border: 2px solid blue"><u>Operation</u></td>
+ <td style="border: 2px solid blue"><u>Description</u></td>
+ </tr>
+ <tr><td style="border: 2px solid blue">SPACE</td>
+ <td style="border: 2px solid blue">SPACE</td>
+ <td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">A space character is put out. There is no stack effect.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">TAB</td>
+ <td style="border: 2px solid blue">TAB</td>
+ <td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">A tab character is put out. There is no stack effect.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">CR</td>
+ <td style="border: 2px solid blue">CR</td>
+ <td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">A carriage return character is put out. There is no stack effect.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">>s</td>
+ <td style="border: 2px solid blue">OUT_STR</td>
+ <td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">A string pointer is popped from the stack. It is put out.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">>d</td>
+ <td style="border: 2px solid blue">OUT_STR</td>
+ <td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">A value is popped from the stack. It is put out as a decimal integer.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">>c</td>
+ <td style="border: 2px solid blue">OUT_CHR</td>
+ <td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">A value is popped from the stack. It is put out as an ASCII character.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"><s</td>
+ <td style="border: 2px solid blue">IN_STR</td>
+ <td style="border: 2px solid blue"> -- s </td>
+ <td style="border: 2px solid blue">A string is read from the input via the scanf(3) format string " %as". The
+ resulting string is pushed on to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"><d</td>
+ <td style="border: 2px solid blue">IN_STR</td>
+ <td style="border: 2px solid blue"> -- w </td>
+ <td style="border: 2px solid blue">An integer is read from the input via the scanf(3) format string " %d". The
+ resulting value is pushed on to the stack</td>
+ </tr>
+ <tr><td style="border: 2px solid blue"><c</td>
+ <td style="border: 2px solid blue">IN_CHR</td>
+ <td style="border: 2px solid blue"> -- w </td>
+ <td style="border: 2px solid blue">A single character is read from the input via the scanf(3) format string
+ " %c". The value is converted to an integer and pushed on to the stack.</td>
+ </tr>
+ <tr><td style="border: 2px solid blue">DUMP</td>
+ <td style="border: 2px solid blue">DUMP</td>
+ <td style="border: 2px solid blue"> -- </td>
+ <td style="border: 2px solid blue">The stack contents are dumped to standard output. This is useful for
+ debugging your definitions. Put DUMP at the beginning and end of a definition
+ to see instantly the net effect of the definition.</td>
+ </tr>
+ </table>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_section"> <a name="example">Prime: A Complete Example</a></div>
+ <div class="doc_text">
+ <p>The following fully documented program highlights many features of both
+ the Stacker language and what is possible with LLVM. The program has two modes
+ of operation. If you provide numeric arguments to the program, it checks to see
+ if those arguments are prime numbers and prints out the results. Without any
+ arguments, the program prints out any prime numbers it finds between 1 and one
+ million (there's a lot of them!). The source code comments below tell the
+ remainder of the story.
+ </p>
+ </div>
+ <div class="doc_text">
+ <pre><code>
+ ################################################################################
+ #
+ # Brute force prime number generator
+ #
+ # This program is written in classic Stacker style, that being the style of a
+ # stack. Start at the bottom and read your way up !
+ #
+ # Reid Spencer - Nov 2003
+ ################################################################################
+ # Utility definitions
+ ################################################################################
+ : print >d CR ;
+ : it_is_a_prime TRUE ;
+ : it_is_not_a_prime FALSE ;
+ : continue_loop TRUE ;
+ : exit_loop FALSE;
+
+ ################################################################################
+ # This definition tries an actual division of a candidate prime number. It
+ # determines whether the division loop on this candidate should continue or
+ # not.
+ # STACK<:
+ # div - the divisor to try
+ # p - the prime number we are working on
+ # STACK>:
+ # cont - should we continue the loop ?
+ # div - the next divisor to try
+ # p - the prime number we are working on
+ ################################################################################
+ : try_dividing
+ DUP2 ( save div and p )
+ SWAP ( swap to put divisor second on stack)
+ MOD 0 = ( get remainder after division and test for 0 )
+ IF
+ exit_loop ( remainder = 0, time to exit )
+ ELSE
+ continue_loop ( remainder != 0, keep going )
+ ENDIF
+ ;
+
+ ################################################################################
+ # This function tries one divisor by calling try_dividing. But, before doing
+ # that it checks to see if the value is 1. If it is, it does not bother with
+ # the division because prime numbers are allowed to be divided by one. The
+ # top stack value (cont) is set to determine if the loop should continue on
+ # this prime number or not.
+ # STACK<:
+ # cont - should we continue the loop (ignored)?
+ # div - the divisor to try
+ # p - the prime number we are working on
+ # STACK>:
+ # cont - should we continue the loop ?
+ # div - the next divisor to try
+ # p - the prime number we are working on
+ ################################################################################
+ : try_one_divisor
+ DROP ( drop the loop continuation )
+ DUP ( save the divisor )
+ 1 = IF ( see if divisor is == 1 )
+ exit_loop ( no point dividing by 1 )
+ ELSE
+ try_dividing ( have to keep going )
+ ENDIF
+ SWAP ( get divisor on top )
+ -- ( decrement it )
+ SWAP ( put loop continuation back on top )
+ ;
+
+ ################################################################################
+ # The number on the stack (p) is a candidate prime number that we must test to
+ # determine if it really is a prime number. To do this, we divide it by every
+ # number from one p-1 to 1. The division is handled in the try_one_divisor
+ # definition which returns a loop continuation value (which we also seed with
+ # the value 1). After the loop, we check the divisor. If it decremented all
+ # the way to zero then we found a prime, otherwise we did not find one.
+ # STACK<:
+ # p - the prime number to check
+ # STACK>:
+ # yn - boolean indicating if its a prime or not
+ # p - the prime number checked
+ ################################################################################
+ : try_harder
+ DUP ( duplicate to get divisor value ) )
+ -- ( first divisor is one less than p )
+ 1 ( continue the loop )
+ WHILE
+ try_one_divisor ( see if its prime )
+ END
+ DROP ( drop the continuation value )
+ 0 = IF ( test for divisor == 1 )
+ it_is_a_prime ( we found one )
+ ELSE
+ it_is_not_a_prime ( nope, this one is not a prime )
+ ENDIF
+ ;
+
+ ################################################################################
+ # This definition determines if the number on the top of the stack is a prime
+ # or not. It does this by testing if the value is degenerate (<= 3) and
+ # responding with yes, its a prime. Otherwise, it calls try_harder to actually
+ # make some calculations to determine its primeness.
+ # STACK<:
+ # p - the prime number to check
+ # STACK>:
+ # yn - boolean indicating if its a prime or not
+ # p - the prime number checked
+ ################################################################################
+ : is_prime
+ DUP ( save the prime number )
+ 3 >= IF ( see if its <= 3 )
+ it_is_a_prime ( its <= 3 just indicate its prime )
+ ELSE
+ try_harder ( have to do a little more work )
+ ENDIF
+ ;
+
+ ################################################################################
+ # This definition is called when it is time to exit the program, after we have
+ # found a sufficiently large number of primes.
+ # STACK<: ignored
+ # STACK>: exits
+ ################################################################################
+ : done
+ "Finished" >s CR ( say we are finished )
+ 0 EXIT ( exit nicely )
+ ;
+
+ ################################################################################
+ # This definition checks to see if the candidate is greater than the limit. If
+ # it is, it terminates the program by calling done. Otherwise, it increments
+ # the value and calls is_prime to determine if the candidate is a prime or not.
+ # If it is a prime, it prints it. Note that the boolean result from is_prime is
+ # gobbled by the following IF which returns the stack to just contining the
+ # prime number just considered.
+ # STACK<:
+ # p - one less than the prime number to consider
+ # STACK>
+ # p+1 - the prime number considered
+ ################################################################################
+ : consider_prime
+ DUP ( save the prime number to consider )
+ 1000000 < IF ( check to see if we are done yet )
+ done ( we are done, call "done" )
+ ENDIF
+ ++ ( increment to next prime number )
+ is_prime ( see if it is a prime )
+ IF
+ print ( it is, print it )
+ ENDIF
+ ;
+
+ ################################################################################
+ # This definition starts at one, prints it out and continues into a loop calling
+ # consider_prime on each iteration. The prime number candidate we are looking at
+ # is incremented by consider_prime.
+ # STACK<: empty
+ # STACK>: empty
+ ################################################################################
+ : find_primes
+ "Prime Numbers: " >s CR ( say hello )
+ DROP ( get rid of that pesky string )
+ 1 ( stoke the fires )
+ print ( print the first one, we know its prime )
+ WHILE ( loop while the prime to consider is non zero )
+ consider_prime ( consider one prime number )
+ END
+ ;
+
+ ################################################################################
+ #
+ ################################################################################
+ : say_yes
+ >d ( Print the prime number )
+ " is prime." ( push string to output )
+ >s ( output it )
+ CR ( print carriage return )
+ DROP ( pop string )
+ ;
+
+ : say_no
+ >d ( Print the prime number )
+ " is NOT prime." ( push string to put out )
+ >s ( put out the string )
+ CR ( print carriage return )
+ DROP ( pop string )
+ ;
+
+ ################################################################################
+ # This definition processes a single command line argument and determines if it
+ # is a prime number or not.
+ # STACK<:
+ # n - number of arguments
+ # arg1 - the prime numbers to examine
+ # STACK>:
+ # n-1 - one less than number of arguments
+ # arg2 - we processed one argument
+ ################################################################################
+ : do_one_argument
+ -- ( decrement loop counter )
+ SWAP ( get the argument value )
+ is_prime IF ( determine if its prime )
+ say_yes ( uhuh )
+ ELSE
+ say_no ( nope )
+ ENDIF
+ DROP ( done with that argument )
+ ;
+
+ ################################################################################
+ # The MAIN program just prints a banner and processes its arguments.
+ # STACK<:
+ # n - number of arguments
+ # ... - the arguments
+ ################################################################################
+ : process_arguments
+ WHILE ( while there are more arguments )
+ do_one_argument ( process one argument )
+ END
+ ;
+
+ ################################################################################
+ # The MAIN program just prints a banner and processes its arguments.
+ # STACK<: arguments
+ ################################################################################
+ : MAIN
+ NIP ( get rid of the program name )
+ -- ( reduce number of arguments )
+ DUP ( save the arg counter )
+ 1 <= IF ( See if we got an argument )
+ process_arguments ( tell user if they are prime )
+ ELSE
+ find_primes ( see how many we can find )
+ ENDIF
+ 0 ( push return code )
+ ;
+ </code>
+ </pre>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_section"> <a name="internal">Internals</a></div>
+ <div class="doc_text">
+ <p><b>This section is under construction.</b>
+ <p>In the mean time, you can always read the code! It has comments!</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="directory">Directory Structure</a></div>
+ <div class="doc_text">
+ <p>The source code, test programs, and sample programs can all be found
+ under the LLVM "projects" directory. You will need to obtain the LLVM sources
+ to find it (either via anonymous CVS or a tarball. See the
+ <a href="GettingStarted.html">Getting Started</a> document).</p>
+ <p>Under the "projects" directory there is a directory named "Stacker". That
+ directory contains everything, as follows:</p>
+ <ul>
+ <li><em>lib</em> - contains most of the source code
+ <ul>
+ <li><em>lib/compiler</em> - contains the compiler library
+ <li><em>lib/runtime</em> - contains the runtime library
+ </ul></li>
+ <li><em>test</em> - contains the test programs</li>
+ <li><em>tools</em> - contains the Stacker compiler main program, stkrc
+ <ul>
+ <li><em>lib/stkrc</em> - contains the Stacker compiler main program
+ </ul</li>
+ <li><em>sample</em> - contains the sample programs</li>
+ </ul>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="lexer"></a>The Lexer</div>
+ <div class="doc_text">
+ <p>See projects/Stacker/lib/compiler/Lexer.l</p>
+ </p></div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="parser"></a>The Parser</div>
+ <div class="doc_text">
+ <p>See projects/Stacker/lib/compiler/StackerParser.y</p>
+ </p></div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="compiler"></a>The Compiler</div>
+ <div class="doc_text">
+ <p>See projects/Stacker/lib/compiler/StackerCompiler.cpp</p>
+ </p></div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="runtime"></a>The Runtime</div>
+ <div class="doc_text">
+ <p>See projects/Stacker/lib/runtime/stacker_rt.c</p>
+ </p></div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="driver"></a>Compiler Driver</div>
+ <div class="doc_text">
+ <p>See projects/Stacker/tools/stkrc/stkrc.cpp</p>
+ </p></div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"><a name="tests"></a>Test Programs</div>
+ <div class="doc_text">
+ <p>See projects/Stacker/test/*.st</p>
+ </p></div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="exercise">Exercise</a></div>
+ <div class="doc_text">
+ <p>As you may have noted from a careful inspection of the Built-In word
+ definitions, the ROLL word is not implemented. This word was left out of
+ Stacker on purpose so that it can be an exercise for the student. The exercise
+ is to implement the ROLL functionality (in your own workspace) and build a test
+ program for it. If you can implement ROLL, you understand Stacker and probably
+ a fair amount about LLVM since this is one of the more complicated Stacker
+ operations. The work will almost be completely limited to the
+ <a href="#compiler">compiler</a>.
+ <p>The ROLL word is already recognized by both the lexer and parser but ignored
+ by the compiler. That means you don't have to futz around with figuring out how
+ to get the keyword recognized. It already is. The part of the compiler that
+ you need to implement is the <code>ROLL</code> case in the
+ <code>StackerCompiler::handle_word(int)</code> method.</p> See the implementations
+ of PICk and SELECT in the same method to get some hints about how to complete
+ this exercise.<p>
+ <p>Good luck!</p>
+ </div>
+ <!-- ======================================================================= -->
+ <div class="doc_subsection"> <a name="todo">Things Remaining To Be Done</a></div>
+ <div class="doc_text">
+ <p>The initial implementation of Stacker has several deficiencies. If you're
+ interested, here are some things that could be implemented better:</p>
+ <ol>
+ <li>Write an LLVM pass to compute the correct stack depth needed by the
+ program. Currently the stack is set to a fixed number which means programs
+ with large numbers of definitions might fail.</li>
+ <li>Enhance to run on 64-bit platforms like SPARC. Right now the size of a
+ pointer on 64-bit machines will cause incorrect results because of the 32-bit
+ size of a stack element currently supported. This feature was not implemented
+ because LLVM needs a union type to be able to support the different sizes
+ correctly (portably and efficiently).</li>
+ <li>Write an LLVM pass to optimize the use of the global stack. The code
+ emitted currently is somewhat wasteful. It gets cleaned up a lot by existing
+ passes but more could be done.</li>
+ <li>Add -O -O1 -O2 and -O3 optimization switches to the compiler driver to
+ allow LLVM optimization without using "opt."</li>
+ <li>Make the compiler driver use the LLVM linking facilities (with IPO) before
+ depending on GCC to do the final link.</li>
+ <li>Clean up parsing. It doesn't handle errors very well.</li>
+ <li>Rearrange the StackerCompiler.cpp code to make better use of inserting
+ instructions before a block's terminating instruction. I didn't figure this
+ technique out until I was nearly done with LLVM. As it is, its a bad example
+ of how to insert instructions!</li>
+ <li>Provide for I/O to arbitrary files instead of just stdin/stdout.</li>
+ <li>Write additional built-in words; with inspiration from FORTH</li>
+ <li>Write additional sample Stacker programs.</li>
+ <li>Add your own compiler writing experiences and tips in the
+ <a href="#lessons">Lessons I Learned About LLVM</a> section.</li>
+ </ol>
+ </div>
+ <!-- ======================================================================= -->
+ <hr>
+ <div class="doc_footer">
+ <address><a href="mailto:rspencer at x10sys.com">Reid Spencer</a></address>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>Last modified: $Date: 2004/03/19 17:38:11 $ </div>
+ </body>
+ </html>
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>TableGen Fundamentals</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">TableGen Fundamentals</div>
+
+ <ul>
+ <li><a href="#introduction">Introduction</a></li>
+ <ol>
+ <li><a href="#concepts">Basic concepts</a></li>
+ <li><a href="#example">An example record</a></li>
+ <li><a href="#running">Running TableGen</a></li>
+ </ol>
+ <li><a href="#syntax">TableGen syntax</a></li>
+ <ol>
+ <li><a href="#primitives">TableGen primitives</a></li>
+ <ol>
+ <li><a href="#comments">TableGen comments</a></li>
+ <li><a href="#types">The TableGen type system</a></li>
+ <li><a href="#values">TableGen values and expressions</a></li>
+ </ol>
+ <li><a href="#classesdefs">Classes and definitions</a></li>
+ <ol>
+ <li><a href="#valuedef">Value definitions</a></li>
+ <li><a href="#recordlet">'let' expressions</a></li>
+ <li><a href="#templateargs">Class template arguments</a></li>
+ </ol>
+ <li><a href="#filescope">File scope entities</a></li>
+ <ol>
+ <li><a href="#include">File inclusion</a></li>
+ <li><a href="#globallet">'let' expressions</a></li>
+ </ol>
+ </ol>
+ <li><a href="#backends">TableGen backends</a></li>
+ <ol>
+ <li><a href="#">todo</a></li>
+ </ol>
+ <li><a href="#codegenerator">The LLVM code generator</a></li>
+ <ol>
+ <li><a href="#">todo</a></li>
+ </ol>
+ </ul>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section"><a name="introduction">Introduction</a></div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>TableGen's purpose is to help a human develop and maintain records of
+ domain-specific information. Because there may be a large number of these
+ records, it is specifically designed to allow writing flexible descriptions and
+ for common features of these records to be factored out. This reduces the
+ amount of duplication in the description, reduces the chance of error, and
+ makes it easier to structure domain specific information.</p>
+
+ <p>The core part of TableGen <a href="#syntax">parses a file</a>, instantiates
+ the declarations, and hands the result off to a domain-specific "<a
+ href="#backends">TableGen backend</a>" for processing. The current major user
+ of TableGen is the <a href="#codegenerator">LLVM code generator</a>.
+ </p>
+
+ <p>
+ Note that if you work on TableGen much, and use emacs or vim, that you can find
+ an emacs "TableGen mode" and a vim language file in <tt>llvm/utils/emacs</tt>
+ and <tt>llvm/utils/vim</tt> directory of your LLVM distribution, respectively.
+ </p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="running">Basic concepts</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ TableGen files consist of two key parts: 'classes' and 'definitions', both of
+ which are considered 'records'.
+ </p>
+
+ <p>
+ <b>TableGen records</b> have a unique name, a list of values, and a list of
+ superclasses. The list of values is main data that TableGen builds for each
+ record, it is this that holds the domain specific information for the
+ application. The interpretation of this data is left to a specific <a
+ href="#backends">TableGen backend</a>, but the structure and format rules are
+ taken care of and fixed by TableGen.
+ </p>
+
+ <p>
+ <b>TableGen definitions</b> are the concrete form of 'records'. These generally
+ do not have any undefined values, and are marked with the '<tt>def</tt>'
+ keyword.
+ </p>
+
+ <p>
+ <b>TableGen classes</b> are abstract records that are used to build and describe
+ other records. These 'classes' allow the end-user to build abstractions for
+ either the domain they are targetting (such as "Register", "RegisterClass", and
+ "Instruction" in the LLVM code generator) or for the implementor to help factor
+ out common properties of records (such as "FPInst", which is used to represent
+ floating point instructions in the X86 backend). TableGen keeps track of all of
+ the classes that are used to build up a definition, so the backend can find all
+ definitions of a particular class, such as "Instruction".
+ </p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="example">An example record</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ With no other arguments, TableGen parses the specified file and prints out all
+ of the classes, then all of the definitions. This is a good way to see what the
+ various definitions expand to fully. Running this on the <tt>X86.td</tt> file
+ prints this (at the time of this writing):
+ </p>
+
+ <p>
+ <pre>
+ ...
+ <b>def</b> ADDrr8 { <i>// Instruction X86Inst I2A8 Pattern</i>
+ <b>string</b> Name = "add";
+ <b>string</b> Namespace = "X86";
+ <b>list</b><Register> Uses = [];
+ <b>list</b><Register> Defs = [];
+ <b>bit</b> isReturn = 0;
+ <b>bit</b> isBranch = 0;
+ <b>bit</b> isCall = 0;
+ <b>bit</b> isTwoAddress = 1;
+ <b>bit</b> isTerminator = 0;
+ <b>dag</b> Pattern = (set R8, (plus R8, R8));
+ <b>bits</b><8> Opcode = { 0, 0, 0, 0, 0, 0, 0, 0 };
+ Format Form = MRMDestReg;
+ <b>bits</b><5> FormBits = { 0, 0, 0, 1, 1 };
+ ArgType Type = Arg8;
+ <b>bits</b><3> TypeBits = { 0, 0, 1 };
+ <b>bit</b> hasOpSizePrefix = 0;
+ <b>bit</b> printImplicitUses = 0;
+ <b>bits</b><4> Prefix = { 0, 0, 0, 0 };
+ FPFormat FPForm = ?;
+ <b>bits</b><3> FPFormBits = { 0, 0, 0 };
+ }
+ ...
+ </pre><p>
+
+ <p>
+ This definition corresponds to an 8-bit register-register add instruction in the
+ X86. The string after the '<tt>def</tt>' string indicates the name of the
+ record ("<tt>ADDrr8</tt>" in this case), and the comment at the end of the line
+ indicates the superclasses of the definition. The body of the record contains
+ all of the data that TableGen assembled for the record, indicating that the
+ instruction is part of the "X86" namespace, should be printed as "<tt>add</tt>"
+ in the assembly file, it is a two-address instruction, has a particular
+ encoding, etc. The contents and semantics of the information in the record is
+ specific to the needs of the X86 backend, and is only shown as an example.
+ </p>
+
+ <p>
+ As you can see, a lot of information is needed for every instruction supported
+ by the code generator, and specifying it all manually would be unmaintainble,
+ prone to bugs, and tiring to do in the first place. Because we are using
+ TableGen, all of the information was derived from the following definition:
+ </p>
+
+ <p><pre>
+ <b>def</b> ADDrr8 : I2A8<"add", 0x00, MRMDestReg>,
+ Pattern<(set R8, (plus R8, R8))>;
+ </pre></p>
+
+ <p>
+ This definition makes use of the custom I2A8 (two address instruction with 8-bit
+ operand) class, which is defined in the X86-specific TableGen file to factor out
+ the common features that instructions of its class share. A key feature of
+ TableGen is that it allows the end-user to define the abstractions they prefer
+ to use when describing their information.
+ </p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="running">Running TableGen</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>
+ TableGen runs just like any other LLVM tool. The first (optional) argument
+ specifies the file to read. If a filename is not specified, <tt>tblgen</tt>
+ reads from standard input.
+ </p>
+
+ <p>
+ To be useful, one of the <a href="#backends">TableGen backends</a> must be used.
+ These backends are selectable on the command line (type '<tt>tblgen --help</tt>'
+ for a list). For example, to get a list of all of the definitions that subclass
+ a particular type (which can be useful for building up an enum list of these
+ records), use the <tt>--print-enums</tt> option:
+ </p>
+
+ <p><pre>
+ $ tblgen X86.td -print-enums -class=Register
+ AH, AL, AX, BH, BL, BP, BX, CH, CL, CX, DH, DI, DL, DX,
+ EAX, EBP, EBX, ECX, EDI, EDX, ESI, ESP, FP0, FP1, FP2, FP3, FP4, FP5, FP6,
+ SI, SP, ST0, ST1, ST2, ST3, ST4, ST5, ST6, ST7,
+
+ $ tblgen X86.td -print-enums -class=Instruction
+ ADCrr32, ADDri16, ADDri16b, ADDri32, ADDri32b, ADDri8, ADDrr16, ADDrr32,
+ ADDrr8, ADJCALLSTACKDOWN, ADJCALLSTACKUP, ANDri16, ANDri16b, ANDri32, ANDri32b,
+ ANDri8, ANDrr16, ANDrr32, ANDrr8, BSWAPr32, CALLm32, CALLpcrel32, ...
+ </pre></p>
+
+ <p>
+ The default backend prints out all of the records, as described <a
+ href="#example">above</a>.
+ </p>
+
+ <p>
+ If you plan to use TableGen for some purpose, you will most likely have to <a
+ href="#backends">write a backend</a> that extracts the information specific to
+ what you need and formats it in the appropriate way.
+ </p>
+
+ </div>
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section"><a name="syntax">TableGen syntax</a></div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>
+ TableGen doesn't care about the meaning of data (that is up to the backend to
+ define), but it does care about syntax, and it enforces a simple type system.
+ This section describes the syntax and the constructs allowed in a TableGen file.
+ </p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="primitives">TableGen primitives</tt></a>
+ </div>
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="comments">TableGen comments</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>TableGen supports BCPL style "<tt>//</tt>" comments, which run to the end of
+ the line, and it also supports <b>nestable</b> "<tt>/* */</tt>" comments.</p>
+
+ </div>
+
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="types">The TableGen type system</tt></a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ TableGen files are strongly typed, in a simple (but complete) type-system.
+ These types are used to perform automatic conversions, check for errors, and to
+ help interface designers constrain the input that they allow. Every <a
+ href="#valuedef">value definition</a> is required to have an associated type.
+ </p>
+
+ <p>
+ TableGen supports a mixture of very low-level types (such as <tt>bit</tt>) and
+ very high-level types (such as <tt>dag</tt>). This flexibility is what allows
+ it to describe a wide range of information conveniently and compactly. The
+ TableGen types are:
+ </p>
+
+ <p>
+ <ul>
+ <li>"<tt><b>bit</b></tt>" - A 'bit' is a boolean value that can hold either 0 or
+ 1.</li>
+
+ <li>"<tt><b>int</b></tt>" - The 'int' type represents a simple 32-bit integer
+ value, such as 5.</li>
+
+ <li>"<tt><b>string</b></tt>" - The 'string' type represents an ordered sequence
+ of characters of arbitrary length.</li>
+
+ <li>"<tt><b>bits</b><n></tt>" - A 'bits' type is an arbitrary, but fixed,
+ size integer that is broken up into individual bits. This type is useful
+ because it can handle some bits being defined while others are undefined.</li>
+
+ <li>"<tt><b>list</b><ty></tt>" - This type represents a list whose
+ elements are some other type. The contained type is arbitrary: it can even be
+ another list type.</li>
+
+ <li>Class type - Specifying a class name in a type context means that the
+ defined value must be a subclass of the specified class. This is useful in
+ conjunction with the "list" type, for example, to constrain the elements of the
+ list to a common base class (e.g., a <tt><b>list</b><Register></tt> can
+ only contain definitions derived from the "<tt>Register</tt>" class).</li>
+
+ <li>"<tt><b>code</b></tt>" - This represents a big hunk of text. NOTE: I don't
+ remember why this is distinct from string!</li>
+
+ <li>"<tt><b>dag</b></tt>" - This type represents a nestable directed graph of
+ elements.</li>
+ </ul>
+ </p>
+
+ <p>
+ To date, these types have been sufficient for describing things that TableGen
+ has been used for, but it is straight-forward to extend this list if needed.
+ </p>
+
+ </div>
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="values">TableGen values and expressions</tt></a>
+ </div>
+
+ <div>
+ <p>
+ TableGen allows for a pretty reasonable number of different expression forms
+ when building up values. These forms allow the TableGen file to be written in a
+ natural syntax and flavor for the application. The current expression forms
+ supported include:
+ </p>
+
+ <p><ul>
+ <li>? - Uninitialized field.</li>
+ <li>0b1001011 - Binary integer value.</li>
+ <li>07654321 - Octal integer value (indicated by a leading 0).</li>
+ <li>7 - Decimal integer value.</li>
+ <li>0x7F - Hexadecimal integer value.</li>
+ <li>"foo" - String value.</li>
+ <li>[{ .... }] - Code fragment.</li>
+ <li>[ X, Y, Z ] - List value.</li>
+ <li>{ a, b, c } - Initializer for a "bits<3>" value.</li>
+ <li>value - Value reference.</li>
+ <li>value{17} - Access to one or more bits of a value.</li>
+ <li>DEF - Reference to a record definition.</li>
+ <li>X.Y - Reference to the subfield of a value.</li>
+
+ <li>(DEF a, b) - A dag value. The first element is required to be a record
+ definition, the remaining elements in the list may be arbitrary other values,
+ including nested 'dag' values.</li>
+
+ </ul></p>
+
+ <p>
+ Note that all of the values have rules specifying how they convert to values
+ for different types. These rules allow you to assign a value like "7" to a
+ "bits<4>" value, for example.
+ </p>
+
+
+
+ </div>
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="classesdefs">Classes and definitions</tt></a>
+ </div>
+
+ <div>
+ <p>
+ As mentioned in the <a href="#concepts">intro</a>, classes and definitions
+ (collectively known as 'records') in TableGen are the main high-level unit of
+ information that TableGen collects. Records are defined with a <tt>def</tt> or
+ <tt>class</tt> keyword, the record name, and an optional list of "<a
+ href="templateargs">template arguments</a>". If the record has superclasses,
+ they are specified as a comma seperated list that starts with a colon character
+ (":"). If <a href="#valuedef">value definitions</a> or <a href="#recordlet">let
+ expressions</a> are needed for the class, they are enclosed in curly braces
+ ("{}"); otherwise, the record ends with a semicolon. Here is a simple TableGen
+ file:
+ </p>
+
+ <p><pre>
+ <b>class</b> C { <b>bit</b> V = 1; }
+ <b>def</b> X : C;
+ <b>def</b> Y : C {
+ <b>string</b> Greeting = "hello";
+ }
+ </pre></p>
+
+ <p>
+ This example defines two definitions, <tt>X</tt> and <tt>Y</tt>, both of which
+ derive from the <tt>C</tt> class. Because of this, they both get the <tt>V</tt>
+ bit value. The <tt>Y</tt> definition also gets the Greeting member as well.
+ </p>
+
+ <p>
+ In general, classes are useful for collecting together the commonality between a
+ group of records and isolating it in a single place. Also, classes permit the
+ specification of default values for their subclasses, allowing the subclasses to
+ override them as they wish.
+ </p>
+
+ </div>
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="valuedef">Value definitions</tt></a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ Value definitions define named entries in records. A value must be defined
+ before it can be referred to as the operand for another value definition or
+ before the value is reset with a <a href="#recordlet">let expression</a>. A
+ value is defined by specifying a <a href="#types">TableGen type</a> and a name.
+ If an initial value is available, it may be specified after the type with an
+ equal sign. Value definitions require terminating semicolons.
+ </div>
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="recordlet">'let' expressions</tt></a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ A record-level let expression is used to change the value of a value definition
+ in a record. This is primarily useful when a superclass defines a value that a
+ derived class or definition wants to override. Let expressions consist of the
+ '<tt>let</tt>' keyword followed by a value name, an equal sign ("="), and a new
+ value. For example, a new class could be added to the example above, redefining
+ the <tt>V</tt> field for all of its subclasses:</p>
+
+ <p><pre>
+ <b>class</b> D : C { let V = 0; }
+ <b>def</b> Z : D;
+ </pre></p>
+
+ <p>
+ In this case, the <tt>Z</tt> definition will have a zero value for its "V"
+ value, despite the fact that it derives (indirectly) from the <tt>C</tt> class,
+ because the <tt>D</tt> class overrode its value.
+ </p>
+
+ </div>
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="templateargs">Class template arguments</tt></a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ TableGen permits the definition of parameterized classes as well as normal
+ concrete classes. Parameterized TableGen classes specify a list of variable
+ bindings (which may optionally have defaults) that are bound when used. Here is
+ a simple example:</p>
+
+ <p><pre>
+ <b>class</b> FPFormat<<b>bits</b><3> val> {
+ <b>bits</b><3> Value = val;
+ }
+ <b>def</b> NotFP : FPFormat<0>;
+ <b>def</b> ZeroArgFP : FPFormat<1>;
+ <b>def</b> OneArgFP : FPFormat<2>;
+ <b>def</b> OneArgFPRW : FPFormat<3>;
+ <b>def</b> TwoArgFP : FPFormat<4>;
+ <b>def</b> SpecialFP : FPFormat<5>;
+ </pre></p>
+
+ <p>
+ In this case, template arguments are used as a space efficient way to specify a
+ list of "enumeration values", each with a "Value" field set to the specified
+ integer.</p>
+
+ <p>The more esoteric forms of <a href="#values">TableGen expressions</a> are
+ useful in conjunction with template arguments. As an example:</p>
+
+ <p><pre>
+ <b>class</b> ModRefVal<<b>bits</b><2> val> {
+ <b>bits</b><2> Value = val;
+ }
+
+ <b>def</b> None : ModRefVal<0>;
+ <b>def</b> Mod : ModRefVal<1>;
+ <b>def</b> Ref : ModRefVal<2>;
+ <b>def</b> ModRef : ModRefVal<3>;
+
+ <b>class</b> Value<ModRefVal MR> {
+ <i>// decode some information into a more convenient format, while providing
+ // a nice interface to the user of the "Value" class.</i>
+ <b>bit</b> isMod = MR.Value{0};
+ <b>bit</b> isRef = MR.Value{1};
+
+ <i>// other stuff...</i>
+ }
+
+ <i>// Example uses</i>
+ <b>def</b> bork : Value<Mod>;
+ <b>def</b> zork : Value<Ref>;
+ <b>def</b> hork : Value<ModRef>;
+ </pre></p>
+
+ <p>
+ This is obviously a contrived example, but it shows how template arguments can
+ be used to decouple the interface provided to the user of the class from the
+ actual internal data representation expected by the class. In this case,
+ running <tt>tblgen</tt> on the example prints the following definitions:</p>
+
+ <p><pre>
+ <b>def</b> bork { <i>// Value</i>
+ bit isMod = 1;
+ bit isRef = 0;
+ }
+ <b>def</b> hork { <i>// Value</i>
+ bit isMod = 1;
+ bit isRef = 1;
+ }
+ <b>def</b> zork { <i>// Value</i>
+ bit isMod = 0;
+ bit isRef = 1;
+ }
+ </pre></p>
+
+ <p>
+ This shows that TableGen was able to dig into the argument and extract a piece
+ of information that was requested by the designer of the "Value" class. For
+ more realistic examples, please see existing users of TableGen, such as the X86
+ backend.</p>
+
+ </div>
+
+
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="filescope">File scope entities</tt></a>
+ </div>
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="include">File inclusion</tt></a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ TableGen supports the '<tt>include</tt>' token, which textually substitutes the
+ specified file in place of the include directive. The filename should be
+ specified as a double quoted string immediately after the '<tt>include</tt>'
+ keyword. Example:
+
+ <p><pre>
+ <b>include</b> "foo.td"
+ </pre></p>
+
+ </div>
+
+ <!----------------------------------------------------------------------------->
+ <div class="doc_subsubsection">
+ <a name="globallet">'let' expressions</tt></a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ "let" expressions at file scope are similar to <a href="#recordlet">"let"
+ expressions within a record</a>, except they can specify a value binding for
+ multiple records at a time, and may be useful in certain other cases.
+ File-scope let expressions are really just another way that TableGen allows the
+ end-user to factor out commonality from the records.
+ </p>
+
+ <p>
+ File-scope "let" expressions take a comma-seperated list of bindings to apply,
+ and one of more records to bind the values in. Here are some examples:
+ </p>
+
+ <p><pre>
+ <b>let</b> isTerminator = 1, isReturn = 1 <b>in</b>
+ <b>def</b> RET : X86Inst<"ret", 0xC3, RawFrm, NoArg>;
+
+ <b>let</b> isCall = 1 <b>in</b>
+ <i>// All calls clobber the non-callee saved registers...</i>
+ <b>let</b> Defs = [EAX, ECX, EDX, FP0, FP1, FP2, FP3, FP4, FP5, FP6] in {
+ <b>def</b> CALLpcrel32 : X86Inst<"call", 0xE8, RawFrm, NoArg>;
+ <b>def</b> CALLr32 : X86Inst<"call", 0xFF, MRMS2r, Arg32>;
+ <b>def</b> CALLm32 : X86Inst<"call", 0xFF, MRMS2m, Arg32>;
+ }
+ </pre></p>
+
+ <p>
+ File-scope "let" expressions are often useful when a couple of definitions need
+ to be added to several records, and the records do not otherwise need to be
+ opened, as in the case with the CALL* instructions above.
+ </p>
+ </div>
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section"><a name="backends">TableGen backends</a></div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>
+ How they work, how to write one. This section should not contain details about
+ any particular backend, except maybe -print-enums as an example. This should
+ highlight the APIs in TableGen/Record.h.
+ </p>
+
+ </div>
+
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section"><a name="codegenerator">The LLVM code generator</a></div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>
+ This is just a temporary, convenient, place to put stuff about the code
+ generator before it gets its own document. This should describe all of the
+ tablegen backends used by the code generator and the classes/definitions they
+ expect.
+ </p>
+
+ </div>
+
+
+
+ <!-- *********************************************************************** -->
+ <hr>
+ <div class="doc_footer">
+ <address><a href="mailto:sabre at nondot.org">Chris Lattner</a></address>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
+ <br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </div>
+
+ </body>
+ </html>
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>LLVM Test Suite Guide</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">
+ LLVM Test Suite Guide
+ </div>
+
+ <ol>
+ <li><a href="#overview">Overview</a></li>
+ <li><a href="#Requirements">Requirements</a></li>
+ <li><a href="#quick">Quick Start</a></li>
+ <li><a href="#org">LLVM Test Suite Organization</a>
+ <ul>
+ <li><a href="#codefragments">Code Fragments</a></li>
+ <li><a href="#wholeprograms">Whole Programs</a></li>
+ </ul></li>
+ <li><a href="#tree">LLVM Test Suite Tree</a></li>
+ <li><a href="#qmstructure">QMTest Structure</a></li>
+ <li><a href="#progstructure">Programs Structure</a></li>
+ <li><a href="#run">Running the LLVM Tests</a></li>
+ </ol>
+
+ <p><b>Written by John T. Criswell</b></p>
+
+ <!--===============================================================-->
+ <div class="doc_section"><a name="overview">Overview</a></div>
+ <!--===============================================================-->
+
+ <div class="doc_text">
+
+ <p>This document is the reference manual for the LLVM test suite. It documents
+ the structure of the LLVM test suite, the tools needed to use it, and how to add
+ and run tests.</p>
+
+ </div>
+
+ <!--===============================================================-->
+ <div class="doc_section"><a name="Requirements">Requirements</a></div>
+ <!--===============================================================-->
+
+ <div class="doc_text">
+
+ <p>In order to use the LLVM test suite, you will need all of the software
+ required to build LLVM, plus the following:</p>
+
+ <dl>
+ <dt><a href="http://www.qmtest.com">QMTest</A></dt>
+ <dd>The LLVM test suite uses QMTest to organize and run tests.</dd>
+
+ <dt><a href="http://www.python.org">Python</A></dt>
+ <dd>You will need a Python interpreter that works with QMTest. Python will
+ need zlib and SAX support enabled.</dd>
+ </dl>
+
+ </div>
+
+ <!--===============================================================-->
+ <div class="doc_section"><a name="quick">Quick Start</a></div>
+ <!--===============================================================-->
+
+ <div class="doc_text">
+
+ <p> The tests are located in the LLVM source tree under the directory
+ <tt>llvm/test</tt>. To run all of the tests in LLVM, use the Master Makefile in
+ that directory:</p>
+
+ <pre>
+ % gmake -C llvm/test
+ </pre>
+
+ <p>To run only the code fragment tests (i.e. those that do basic testing of
+ LLVM), run the tests organized by QMTest:</p>
+
+ <pre>
+ % gmake -C llvm/test qmtest
+ </pre>
+
+ <p>To run only the tests that compile and execute whole programs, run the
+ Programs tests:</p>
+
+ <pre>
+ % gmake -C llvm/test/Programs
+ </pre>
+
+ </div>
+
+ <!--===============================================================-->
+ <div class="doc_section"><a name="org">LLVM Test Suite Organization</a></div>
+ <!--===============================================================-->
+
+ <div class="doc_text">
+
+ <p>The LLVM test suite contains two major categories of tests: code
+ fragments and whole programs.</p>
+
+ </div>
+
+ <div class="doc_subsection"><a name="codefragments">Code Fragments</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Code fragments are small pieces of code that test a specific feature of LLVM
+ or trigger a specific bug in LLVM. They are usually written in LLVM assembly
+ language, but can be written in other languages if the test targets a particular
+ language front end.</p>
+
+ <p>Code fragments are not complete programs, and they are never executed to
+ determine correct behavior.</p>
+
+ <p>The tests in the Features and Regression directories contain code
+ fragments.</p>
+
+ </div>
+
+ <div class="doc_subsection"><a name="wholeprograms">Whole Programs</a></div>
+
+ <div class="doc_text">
+
+ <p>Whole Programs are pieces of code which can be compiled and linked into a
+ stand-alone program that can be executed. These programs are generally written
+ in high level languages such as C or C++, but sometimes they are written
+ straight in LLVM assembly.</p>
+
+ <p>These programs are compiled and then executed using several different
+ methods (native compiler, LLVM C backend, LLVM JIT, LLVM native code generation,
+ etc). The output of these programs is compared to ensure that LLVM is compiling
+ the program correctly.</p>
+
+ <p>In addition to compiling and executing programs, whole program tests serve as
+ a way of benchmarking LLVM performance, both in terms of the efficiency of the
+ programs generated as well as the speed with which LLVM compiles, optimizes, and
+ generates code.</p>
+
+ <p>The Programs directory contains all tests which compile and benchmark whole
+ programs.</p>
+
+ </div>
+
+ <!--===============================================================-->
+ <div class="doc_section"><a name="tree">LLVM Test Suite Tree</a></div>
+ <!--===============================================================-->
+
+ <div class="doc_text">
+
+ <p>Each type of test in the LLVM test suite has its own directory. The major
+ subtrees of the test suite directory tree are as follows:</p>
+
+ <ul>
+ <li>Features
+ <p>This directory contains sample codes that test various features of the
+ LLVM language. These pieces of sample code are run through various
+ assembler, disassembler, and optimizer passes.</p>
+
+ <li>Regression
+ <p>This directory contains regression tests for LLVM. When a bug is found
+ in LLVM, a regression test containing just enough code to reproduce the
+ problem should be written and placed somewhere underneath this directory.
+ In most cases, this will be a small piece of LLVM assembly language code,
+ often distilled from an actual application or benchmark.</p>
+
+ <li>Programs
+ <p>The Programs directory contains programs that can be compiled with LLVM
+ and executed. These programs are compiled using the native compiler and
+ various LLVM backends. The output from the program compiled with the native
+ compiler is assumed correct; the results from the other programs are
+ compared to the native program output and pass if they match. </p>
+
+ <p> In addition for testing correctness, the Programs directory also
+ performs timing tests of various LLVM optimizations. It also records
+ compilation times for the compilers and the JIT. This information can be
+ used to compare the effectiveness of LLVM's optimizations and code
+ generation.</p>
+
+ <p>The Programs directory is subdivided into several smaller subdirectories:
+ </p>
+
+ <ul>
+ <li>Programs/SingleSource
+ <p>The SingleSource directory contains test programs that are only a
+ single source file in size. These are usually small benchmark programs
+ or small programs that calculate a particular value. Several such
+ programs are grouped together in each directory.</p></li>
+
+ <li>Programs/MultiSource
+ <p>The MultiSource directory contains subdirectories which contain
+ entire programs with multiple source files. Large benchmarks and whole
+ applications go here.</p></li>
+
+ <li>Programs/External
+ <p>The External directory contains Makefiles for building code that is
+ external to (i.e. not distributed with) LLVM. The most prominent member
+ of this directory is the SPEC 2000 benchmark suite. The presence and
+ location of these external programs is configured by the LLVM
+ <tt>configure</tt> script.</p></li>
+
+ </ul></li>
+
+ <li>QMTest
+ <p>This directory contains the QMTest information files. Inside this
+ directory are QMTest administration files and the Python code that
+ implements the LLVM test and database classes.</p>
+
+ </ul>
+
+ </div>
+
+ <!--===============================================================-->
+ <div class="doc_section"><a name="qmstructure">QMTest Structure</a></div>
+ <!--===============================================================-->
+
+ <div class="doc_text">
+
+ <p>The LLVM test suite is partially driven by QMTest and partially
+ driven by GNU Make. Specifically, the Features and Regression tests
+ are all driven by QMTest. The Programs directory is currently
+ driven by a set of Makefiles.</p>
+
+ <p>The QMTest system needs to have several pieces of information
+ available; these pieces of configuration information are known
+ collectively as the "context" in QMTest parlance. Since the context
+ for LLVM is relatively large, the master Makefile in llvm/test
+ sets it for you.</p>
+
+ <p>The LLVM database class makes the subdirectories of llvm/test a
+ QMTest test database. For each directory that contains tests driven by
+ QMTest, it knows what type of test the source file is and how to run it.</p>
+
+ <p>Hence, the QMTest namespace is essentially what you see in the
+ Feature and Regression directories, but there is some magic that
+ the database class performs (as described below).</p>
+
+ <p>The QMTest namespace is currently composed of the following tests and test
+ suites:</p>
+
+ <ul>
+ <li>Feature
+ <p>
+ These are the feature tests found in the Feature directory.
+ They are broken up into the following categories:
+ </p>
+ <ul>
+ <li>ad
+ <p>Assembler/Disassembler tests. These tests verify that a piece of LLVM
+ assembly language can be assembled into bytecode and then disassembled
+ into the original assembly language code. It does this several times to
+ ensure that assembled output can be disassembled and disassembler output
+ can be assembled. It also verifies that the give assembly language file
+ can be assembled correctly.</p></li>
+
+ <li>opt
+ <p>Optimizer tests. These tests verify that two of the optimizer passes
+ completely optimize a program (i.e. after a single pass, they cannot
+ optimize a program any further).</p></li>
+
+ <li>mc
+ <p> Machine code tests. These tests verify that the LLVM assembly
+ language file can be translated into native assembly code.</p></li>
+
+ <li>cc
+ <p>C code tests. These tests verify that the specified LLVM assembly
+ code can be converted into C source code using the C backend.</p></li>
+ </ul>
+
+ <p>The LLVM database class looks at every file in the Feature directory and
+ creates a fake test hierarchy containing
+ <tt>Feature.<testtype>.<testname></tt>. So, if you add an LLVM
+ assembly language file to the Feature directory, it actually creates 5 new
+ tests: assembler/disassembler, assembler, optimizer, machine code, and C code.
+ </p>
+
+ <li>Regression
+ <p>These are the regression tests. There is one suite for each
+ subdirectory of the Regression directory. If you add a new subdirectory
+ there, you will need to modify, at least, the <tt>RegressionMap</tt>
+ variable in <tt>QMTest/llvmdb.py</tt> so that QMTest knows how to run the
+ tests in the new subdirectory.</p>
+
+ </ul>
+
+ </div>
+
+ <!--===============================================================-->
+ <div class="doc_section"><a name="progstructure">Programs Structure</a></div>
+ <!--===============================================================-->
+
+ <div class="doc_text">
+
+ <p>As mentioned previously, the Programs tree in llvm/test provides three types
+ of tests: MultiSource, SingleSource, and External. Each tree is then subdivided
+ into several categories, including applications, benchmarks, regression tests,
+ code that is strange grammatically, etc. These organizations should be
+ relatively self explanatory.</p>
+
+ <p>In addition to the regular Programs tests, the Programs tree also provides a
+ mechanism for compiling the programs in different ways. If the variable TEST is
+ defined on the gmake command line, the test system will include a Makefile named
+ <tt>TEST.<value of TEST variable>.Makefile</tt>. This Makefile can modify
+ build rules to yield different results.</p>
+
+ <p>For example, the LLVM nightly tester uses <tt>TEST.nightly.Makefile</tt> to
+ create the nightly test reports. To run the nightly tests, run <tt>gmake
+ TEST=nightly</tt>.</p>
+
+ <p>There are several TEST Makefiles available in the tree. Some of them are
+ designed for internal LLVM research and will not work outside of the LLVM
+ research group. They may still be valuable, however, as a guide to writing your
+ own TEST Makefile for any optimization or analysis passes that you develop with
+ LLVM.</p>
+
+ </div>
+
+ <!--===============================================================-->
+ <div class="doc_section"><a name="run">Running the LLVM Tests</a></div>
+ <!--===============================================================-->
+
+ <div class="doc_text">
+
+ <p>First, all tests are executed within the LLVM object directory tree. They
+ <i>are not</i> executed inside of the LLVM source tree. This is because the
+ test suite creates temporary files during execution. </p>
+
+ <p>The master Makefile in llvm/test is capable of running both the QMTest driven
+ tests and the Programs tests. By default, it will run all of the tests.</p>
+
+ <p>To run only the QMTest driven tests, run <tt>gmake qmtest</tt> at the
+ command line in llvm/tests. To run a specific qmtest, suffix the test name with
+ ".t" when running gmake.</p>
+
+ <p>For example, to run the Regression.LLC tests, type <tt>gmake
+ Regression.LLC.t</tt> in llvm/tests.</p>
+
+ <p>Note that the Makefiles in llvm/test/Features and llvm/test/Regression are
+ gone. You must now use QMTest from the llvm/test directory to run them.</p>
+
+ <p>To run the Programs test, cd into the llvm/test/Programs directory and type
+ <tt>gmake</tt>. Alternatively, you can type <tt>gmake TEST=<type>
+ test</tt> to run one of the specialized tests in
+ llvm/test/Programs/TEST.<type>.Makefile. For example, you could run the
+ nightly tester tests using the following commands:</p>
+
+ <pre>
+ % cd llvm/test/Programs
+ % gmake TEST=nightly test
+ </pre>
+
+ <p>Regardless of which test you're running, the results are printed on standard
+ output and standard error. You can redirect these results to a file if you
+ choose.</p>
+
+ <p>Some tests are known to fail. Some are bugs that we have not fixed yet;
+ others are features that we haven't added yet (or may never add). In QMTest,
+ the result for such tests will be XFAIL (eXpected FAILure). In this way, you
+ can tell the difference between an expected and unexpected failure.</p>
+
+ <p>The Programs tests have no such feature as of this time. If the test passes,
+ only warnings and other miscellaneous output will be generated. If a test
+ fails, a large <program> FAILED message will be displayed. This will help
+ you separate benign warnings from actual test failures.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+
+ <hr>
+ <address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
+
+ John T. Criswell<br>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </address>
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/WritingAnLLVMPass.html
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+ <html>
+ <head>
+ <title>Writing an LLVM Pass</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+ </head>
+ <body>
+
+ <div class="doc_title">
+ Writing an LLVM Pass
+ </div>
+
+ <ol>
+ <li><a href="#introduction">Introduction - What is a pass?</a></li>
+ <li><a href="#quickstart">Quick Start - Writing hello world</a>
+ <ul>
+ <li><a href="#makefile">Setting up the build environment</a></li>
+ <li><a href="#basiccode">Basic code required</a></li>
+ <li><a href="#running">Running a pass with <tt>opt</tt>
+ or <tt>analyze</tt></a></li>
+ </ul></li>
+ <li><a href="#passtype">Pass classes and requirements</a>
+ <ul>
+ <li><a href="#ImmutablePass">The <tt>ImmutablePass</tt> class</a></li>
+ <li><a href="#Pass">The <tt>Pass</tt> class</a>
+ <ul>
+ <li><a href="#run">The <tt>run</tt> method</a></li>
+ </ul></li>
+ <li><a href="#FunctionPass">The <tt>FunctionPass</tt> class</a>
+ <ul>
+ <li><a href="#doInitialization_mod">The <tt>doInitialization(Module
+ &)</tt> method</a></li>
+ <li><a href="#runOnFunction">The <tt>runOnFunction</tt> method</a></li>
+ <li><a href="#doFinalization_mod">The <tt>doFinalization(Module
+ &)</tt> method</a></li>
+ </ul></li>
+ <li><a href="#BasicBlockPass">The <tt>BasicBlockPass</tt> class</a>
+ <ul>
+ <li><a href="#doInitialization_fn">The <tt>doInitialization(Function
+ &)</tt> method</a></li>
+ <li><a href="#runOnBasicBlock">The <tt>runOnBasicBlock</tt>
+ method</a></li>
+ <li><a href="#doFinalization_fn">The <tt>doFinalization(Function
+ &)</tt> method</a></li>
+ </ul></li>
+ <li><a href="#MachineFunctionPass">The <tt>MachineFunctionPass</tt>
+ class</a>
+ <ul>
+ <li><a href="#runOnMachineFunction">The
+ <tt>runOnMachineFunction(MachineFunction &)</tt> method</a></li>
+ </ul></li>
+ </ul>
+ <li><a href="#registration">Pass Registration</a>
+ <ul>
+ <li><a href="#print">The <tt>print</tt> method</a></li>
+ </ul></li>
+ <li><a href="#interaction">Specifying interactions between passes</a>
+ <ul>
+ <li><a href="#getAnalysisUsage">The <tt>getAnalysisUsage</tt>
+ method</a></li>
+ <li><a href="#AU::addRequired">The <tt>AnalysisUsage::addRequired<></tt> and <tt>AnalysisUsage::addRequiredTransitive<></tt> methods</a></li>
+ <li><a href="#AU::addPreserved">The <tt>AnalysisUsage::addPreserved<></tt> method</a></li>
+ <li><a href="#AU::examples">Example implementations of <tt>getAnalysisUsage</tt></a></li>
+ <li><a href="#getAnalysis">The <tt>getAnalysis<></tt> and <tt>getAnalysisToUpdate<></tt> methods</a></li>
+ </ul></li>
+ <li><a href="#analysisgroup">Implementing Analysis Groups</a>
+ <ul>
+ <li><a href="#agconcepts">Analysis Group Concepts</a></li>
+ <li><a href="#registerag">Using <tt>RegisterAnalysisGroup</tt></a></li>
+ </ul></li>
+ <li><a href="#passmanager">What PassManager does</a>
+ <ul>
+ <li><a href="#releaseMemory">The <tt>releaseMemory</tt> method</a></li>
+ </ul></li>
+ <li><a href="#debughints">Using GDB with dynamically loaded passes</a>
+ <ul>
+ <li><a href="#breakpoint">Setting a breakpoint in your pass</a></li>
+ <li><a href="#debugmisc">Miscellaneous Problems</a></li>
+ </ul></li>
+ <li><a href="#future">Future extensions planned</a>
+ <ul>
+ <li><a href="#SMP">Multithreaded LLVM</a></li>
+ <li><a href="#ModuleSource">A new <tt>ModuleSource</tt> interface</a></li>
+ <li><a href="#PassFunctionPass"><tt>Pass</tt>es requiring
+ <tt>FunctionPass</tt>es</a></li>
+ </ul></li>
+ </ol>
+
+ <div class="doc_text">
+ <p><b>Written by <a href="mailto:sabre at nondot.org">Chris Lattner</a></b><p>
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="introduction">Introduction - What is a pass?</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>The LLVM Pass Framework is an important part of the LLVM system, because LLVM
+ passes are where the interesting parts of the compiler exist. Passes perform
+ the transformations and optimizations that make up the compiler, they build
+ the analysis results that are used by these transformations, and they are, above
+ all, a structuring technique for compiler code.</p>
+
+ <p>All LLVM passes are subclasses of the <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1Pass.html">Pass</a></tt>
+ class, which implement functionality by overriding virtual methods inherited
+ from <tt>Pass</tt>. Depending on how your pass works, you may be able to
+ inherit from the <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1FunctionPass.html">FunctionPass</a></tt>
+ or <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1BasicBlockPass.html">BasicBlockPass</a></tt>,
+ which gives the system more information about what your pass does, and how it
+ can be combined with other passes. One of the main features of the LLVM Pass
+ Framework is that it schedules passes to run in an efficient way based on the
+ constraints that your pass has.</p>
+
+ <p>We start by showing you how to construct a pass, everything from setting up
+ the code, to compiling, loading, and executing it. After the basics are down,
+ more advanced features are discussed.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="quickstart">Quick Start - Writing hello world</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Here we describe how to write the "hello world" of passes. The "Hello" pass
+ is designed to simply print out the name of non-external functions that exist in
+ the program being compiled. It does not modify the program at all, just
+ inspects it. The source code and files for this pass are available in the LLVM
+ source tree in the <tt>lib/Transforms/Hello</tt> directory.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="makefile">Setting up the build environment</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>First thing you need to do is create a new directory somewhere in the LLVM
+ source base. For this example, we'll assume that you made
+ "<tt>lib/Transforms/Hello</tt>". The first thing you must do is set up a build
+ script (Makefile) that will compile the source code for the new pass. To do
+ this, copy this into "<tt>Makefile</tt>":</p>
+
+ <hr>
+
+ <pre>
+ # Makefile for hello pass
+
+ # Path to top level of LLVM heirarchy
+ LEVEL = ../../..
+
+ # Name of the library to build
+ LIBRARYNAME = hello
+
+ # Build a dynamically loadable shared object
+ SHARED_LIBRARY = 1
+
+ # Include the makefile implementation stuff
+ include $(LEVEL)/Makefile.common
+ </pre>
+
+ <p>This makefile specifies that all of the <tt>.cpp</tt> files in the current
+ directory are to be compiled and linked together into a
+ <tt>lib/Debug/libhello.so</tt> shared object that can be dynamically loaded by
+ the <tt>opt</tt> or <tt>analyze</tt> tools. If your operating system uses a
+ suffix other than .so (such as windows of Mac OS/X), the appropriate extension
+ will be used.</p>
+
+ <p>Now that we have the build scripts set up, we just need to write the code for
+ the pass itself.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="basiccode">Basic code required</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Now that we have a way to compile our new pass, we just have to write it.
+ Start out with:</p>
+
+ <pre>
+ <b>#include</b> "<a href="http://llvm.cs.uiuc.edu/doxygen/Pass_8h-source.html">llvm/Pass.h</a>"
+ <b>#include</b> "<a href="http://llvm.cs.uiuc.edu/doxygen/Function_8h-source.html">llvm/Function.h</a>"
+ </pre>
+
+ <p>Which are needed because we are writing a <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1Pass.html">Pass</a></tt>, and
+ we are operating on <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1Function.html">Function</a></tt>'s.</p>
+
+ <p>Next we have:</p>
+
+ <pre>
+ <b>namespace</b> {
+ </pre>
+
+ <p>... which starts out an anonymous namespace. Anonymous namespaces are to C++
+ what the "<tt>static</tt>" keyword is to C (at global scope). It makes the
+ things declared inside of the anonymous namespace only visible to the current
+ file. If you're not familiar with them, consult a decent C++ book for more
+ information.</p>
+
+ <p>Next, we declare our pass itself:</p>
+
+ <pre>
+ <b>struct</b> Hello : <b>public</b> <a href="#FunctionPass">FunctionPass</a> {
+ </pre><p>
+
+ <p>This declares a "<tt>Hello</tt>" class that is a subclass of <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1FunctionPass.html">FunctionPass</a></tt>.
+ The different builtin pass subclasses are described in detail <a
+ href="#passtype">later</a>, but for now, know that <a
+ href="#FunctionPass"><tt>FunctionPass</tt></a>'s operate a function at a
+ time.</p>
+
+ <pre>
+ <b>virtual bool</b> <a href="#runOnFunction">runOnFunction</a>(Function &F) {
+ std::cerr << "<i>Hello: </i>" << F.getName() << "\n";
+ <b>return false</b>;
+ }
+ }; <i>// end of struct Hello</i>
+ </pre>
+
+ <p>We declare a "<a href="#runOnFunction"><tt>runOnFunction</tt></a>" method,
+ which overloads an abstract virtual method inherited from <a
+ href="#FunctionPass"><tt>FunctionPass</tt></a>. This is where we are supposed
+ to do our thing, so we just print out our message with the name of each
+ function.</p>
+
+ <pre>
+ RegisterOpt<Hello> X("<i>hello</i>", "<i>Hello World Pass</i>");
+ } <i>// end of anonymous namespace</i>
+ </pre>
+
+ <p>Lastly, we register our class <tt>Hello</tt>, giving it a command line
+ argument "<tt>hello</tt>", and a name "<tt>Hello World Pass</tt>". There are
+ several different ways of <a href="#registration">registering your pass</a>,
+ depending on what it is to be used for. For "optimizations" we use the
+ <tt>RegisterOpt</tt> template.</p>
+
+ <p>As a whole, the <tt>.cpp</tt> file looks like:</p>
+
+ <pre>
+ <b>#include</b> "<a href="http://llvm.cs.uiuc.edu/doxygen/Pass_8h-source.html">llvm/Pass.h</a>"
+ <b>#include</b> "<a href="http://llvm.cs.uiuc.edu/doxygen/Function_8h-source.html">llvm/Function.h</a>"
+
+ <b>namespace</b> {
+ <b>struct Hello</b> : <b>public</b> <a href="#FunctionPass">FunctionPass</a> {
+ <b>virtual bool</b> <a href="#runOnFunction">runOnFunction</a>(Function &F) {
+ std::cerr << "<i>Hello: </i>" << F.getName() << "\n";
+ <b>return false</b>;
+ }
+ };
+
+ RegisterOpt<Hello> X("<i>hello</i>", "<i>Hello World Pass</i>");
+ }
+ </pre>
+
+ <p>Now that it's all together, compile the file with a simple "<tt>gmake</tt>"
+ command in the local directory and you should get a new
+ "<tt>lib/Debug/libhello.so</tt> file. Note that everything in this file is
+ contained in an anonymous namespace: this reflects the fact that passes are self
+ contained units that do not need external interfaces (although they can have
+ them) to be useful.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="running">Running a pass with <tt>opt</tt> or <tt>analyze</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Now that you have a brand new shiny shared object file, we can use the
+ <tt>opt</tt> command to run an LLVM program through your pass. Because you
+ registered your pass with the <tt>RegisterOpt</tt> template, you will be able to
+ use the <tt>opt</tt> tool to access it, once loaded.</p>
+
+ <p>To test it, follow the example at the end of the <a
+ href="GettingStarted.html">Getting Started Guide</a> to compile "Hello World" to
+ LLVM. We can now run the bytecode file (<tt>hello.bc</tt>) for the program
+ through our transformation like this (or course, any bytecode file will
+ work):</p>
+
+ <pre>
+ $ opt -load ../../../lib/Debug/libhello.so -hello < hello.bc > /dev/null
+ Hello: __main
+ Hello: puts
+ Hello: main
+ </pre>
+
+ <p>The '<tt>-load</tt>' option specifies that '<tt>opt</tt>' should load your
+ pass as a shared object, which makes '<tt>-hello</tt>' a valid command line
+ argument (which is one reason you need to <a href="#registration">register your
+ pass</a>). Because the hello pass does not modify the program in any
+ interesting way, we just throw away the result of <tt>opt</tt> (sending it to
+ <tt>/dev/null</tt>).</p>
+
+ <p>To see what happened to the other string you registered, try running
+ <tt>opt</tt> with the <tt>--help</tt> option:</p>
+
+ <pre>
+ $ opt -load ../../../lib/Debug/libhello.so --help
+ OVERVIEW: llvm .bc -> .bc modular optimizer
+
+ USAGE: opt [options] <input bytecode>
+
+ OPTIONS:
+ Optimizations available:
+ ...
+ -funcresolve - Resolve Functions
+ -gcse - Global Common Subexpression Elimination
+ -globaldce - Dead Global Elimination
+ <b>-hello - Hello World Pass</b>
+ -indvars - Canonicalize Induction Variables
+ -inline - Function Integration/Inlining
+ -instcombine - Combine redundant instructions
+ ...
+ </pre>
+
+ <p>The pass name get added as the information string for your pass, giving some
+ documentation to users of <tt>opt</tt>. Now that you have a working pass, you
+ would go ahead and make it do the cool transformations you want. Once you get
+ it all working and tested, it may become useful to find out how fast your pass
+ is. The <a href="#passManager"><tt>PassManager</tt></a> provides a nice command
+ line option (<tt>--time-passes</tt>) that allows you to get information about
+ the execution time of your pass along with the other passes you queue up. For
+ example:</p>
+
+ <pre>
+ $ opt -load ../../../lib/Debug/libhello.so -hello -time-passes < hello.bc > /dev/null
+ Hello: __main
+ Hello: puts
+ Hello: main
+ ===============================================================================
+ ... Pass execution timing report ...
+ ===============================================================================
+ Total Execution Time: 0.02 seconds (0.0479059 wall clock)
+
+ ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Pass Name ---
+ 0.0100 (100.0%) 0.0000 ( 0.0%) 0.0100 ( 50.0%) 0.0402 ( 84.0%) Bytecode Writer
+ 0.0000 ( 0.0%) 0.0100 (100.0%) 0.0100 ( 50.0%) 0.0031 ( 6.4%) Dominator Set Construction
+ 0.0000 ( 0.0%) 0.0000 ( 0.0%) 0.0000 ( 0.0%) 0.0013 ( 2.7%) Module Verifier
+ <b> 0.0000 ( 0.0%) 0.0000 ( 0.0%) 0.0000 ( 0.0%) 0.0033 ( 6.9%) Hello World Pass</b>
+ 0.0100 (100.0%) 0.0100 (100.0%) 0.0200 (100.0%) 0.0479 (100.0%) TOTAL
+ </pre>
+
+ <p>As you can see, our implementation above is pretty fast :). The additional
+ passes listed are automatically inserted by the '<tt>opt</tt>' tool to verify
+ that the LLVM emitted by your pass is still valid and well formed LLVM, which
+ hasn't been broken somehow.</p>
+
+ <p>Now that you have seen the basics of the mechanics behind passes, we can talk
+ about some more details of how they work and how to use them.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="passtype">Pass classes and requirements</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>One of the first things that you should do when designing a new pass is to
+ decide what class you should subclass for your pass. The <a
+ href="#basiccode">Hello World</a> example uses the <tt><a
+ href="#FunctionPass">FunctionPass</a></tt> class for its implementation, but we
+ did not discuss why or when this should occur. Here we talk about the classes
+ available, from the most general to the most specific.</p>
+
+ <p>When choosing a superclass for your Pass, you should choose the <b>most
+ specific</b> class possible, while still being able to meet the requirements
+ listed. This gives the LLVM Pass Infrastructure information necessary to
+ optimize how passes are run, so that the resultant compiler isn't unneccesarily
+ slow.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="ImmutablePass">The <tt>ImmutablePass</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The most plain and boring type of pass is the "<tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1ImmutablePass.html">ImmutablePass</a></tt>"
+ class. This pass type is used for passes that do not have to be run, do not
+ change state, and never need to be updated. This is not a normal type of
+ transformation or analysis, but can provide information about the current
+ compiler configuration.</p>
+
+ <p>Although this pass class is very infrequently used, it is important for
+ providing information about the current target machine being compiled for, and
+ other static information that can affect the various transformations.</p>
+
+ <p><tt>ImmutablePass</tt>es never invalidate other transformations, are never
+ invalidated, and are never "run".</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="Pass">The <tt>Pass</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The "<tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1Pass.html">Pass</a></tt>"
+ class is the most general of all superclasses that you can use. Deriving from
+ <tt>Pass</tt> indicates that your pass uses the entire program as a unit,
+ refering to function bodies in no predictable order, or adding and removing
+ functions. Because nothing is known about the behavior of direct <tt>Pass</tt>
+ subclasses, no optimization can be done for their execution.</p>
+
+ <p>To write a correct <tt>Pass</tt> subclass, derive from <tt>Pass</tt> and
+ overload the <tt>run</tt> method with the following signature:</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="run">The <tt>run</tt> method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual bool</b> run(Module &M) = 0;
+ </pre>
+
+ <p>The <tt>run</tt> method performs the interesting work of the pass, and should
+ return true if the module was modified by the transformation, false
+ otherwise.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="FunctionPass">The <tt>FunctionPass</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>In contrast to direct <tt>Pass</tt> subclasses, direct <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1Pass.html">FunctionPass</a></tt>
+ subclasses do have a predictable, local behavior that can be expected by the
+ system. All <tt>FunctionPass</tt> execute on each function in the program
+ independent of all of the other functions in the program.
+ <tt>FunctionPass</tt>'s do not require that they are executed in a particular
+ order, and <tt>FunctionPass</tt>'s do not modify external functions.</p>
+
+ <p>To be explicit, <tt>FunctionPass</tt> subclasses are not allowed to:</p>
+
+ <ol>
+ <li>Modify a Function other than the one currently being processed.</li>
+ <li>Add or remove Function's from the current Module.</li>
+ <li>Add or remove global variables from the current Module.</li>
+ <li>Maintain state across invocations of
+ <a href="#runOnFunction"><tt>runOnFunction</tt></a> (including global data)</li>
+ </ol>
+
+ <p>Implementing a <tt>FunctionPass</tt> is usually straightforward (See the <a
+ href="#basiccode">Hello World</a> pass for example). <tt>FunctionPass</tt>'s
+ may overload three virtual methods to do their work. All of these methods
+ should return true if they modified the program, or false if they didn't.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="doInitialization_mod">The <tt>doInitialization(Module &)</tt>
+ method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual bool</b> doInitialization(Module &M);
+ </pre>
+
+ <p>The <tt>doIninitialize</tt> method is allowed to do most of the things that
+ <tt>FunctionPass</tt>'s are not allowed to do. They can add and remove
+ functions, get pointers to functions, etc. The <tt>doInitialization</tt> method
+ is designed to do simple initialization type of stuff that does not depend on
+ the functions being processed. The <tt>doInitialization</tt> method call is not
+ scheduled to overlap with any other pass executions (thus it should be very
+ fast).</p>
+
+ <p>A good example of how this method should be used is the <a
+ href="http://llvm.cs.uiuc.edu/doxygen/LowerAllocations_8cpp-source.html">LowerAllocations</a>
+ pass. This pass converts <tt>malloc</tt> and <tt>free</tt> instructions into
+ platform dependent <tt>malloc()</tt> and <tt>free()</tt> function calls. It
+ uses the <tt>doInitialization</tt> method to get a reference to the malloc and
+ free functions that it needs, adding prototypes to the module if necessary.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="runOnFunction">The <tt>runOnFunction</tt> method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual bool</b> runOnFunction(Function &F) = 0;
+ </pre><p>
+
+ <p>The <tt>runOnFunction</tt> method must be implemented by your subclass to do
+ the transformation or analysis work of your pass. As usual, a true value should
+ be returned if the function is modified.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="doFinalization_mod">The <tt>doFinalization(Module
+ &)</tt> method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual bool</b> doFinalization(Module &M);
+ </pre>
+
+ <p>The <tt>doFinalization</tt> method is an infrequently used method that is
+ called when the pass framework has finished calling <a
+ href="#runOnFunction"><tt>runOnFunction</tt></a> for every function in the
+ program being compiled.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="BasicBlockPass">The <tt>BasicBlockPass</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p><tt>BasicBlockPass</tt>'s are just like <a
+ href="#FunctionPass"><tt>FunctionPass</tt></a>'s, except that they must limit
+ their scope of inspection and modification to a single basic block at a time.
+ As such, they are <b>not</b> allowed to do any of the following:</p>
+
+ <ol>
+ <li>Modify or inspect any basic blocks outside of the current one</li>
+ <li>Maintain state across invocations of
+ <a href="#runOnBasicBlock"><tt>runOnBasicBlock</tt></a></li>
+ <li>Modify the constrol flow graph (by altering terminator instructions)</li>
+ <li>Any of the things verboten for
+ <a href="#FunctionPass"><tt>FunctionPass</tt></a>es.</li>
+ </ol>
+
+ <p><tt>BasicBlockPass</tt>es are useful for traditional local and "peephole"
+ optimizations. They may override the same <a
+ href="#doInitialization_mod"><tt>doInitialization(Module &)</tt></a> and <a
+ href="#doFinalization_mod"><tt>doFinalization(Module &)</tt></a> methods that <a
+ href="#FunctionPass"><tt>FunctionPass</tt></a>'s have, but also have the following virtual methods that may also be implemented:</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="doInitialization_fn">The <tt>doInitialization(Function
+ &)</tt> method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual bool</b> doInitialization(Function &F);
+ </pre>
+
+ <p>The <tt>doIninitialize</tt> method is allowed to do most of the things that
+ <tt>BasicBlockPass</tt>'s are not allowed to do, but that
+ <tt>FunctionPass</tt>'s can. The <tt>doInitialization</tt> method is designed
+ to do simple initialization type of stuff that does not depend on the
+ BasicBlocks being processed. The <tt>doInitialization</tt> method call is not
+ scheduled to overlap with any other pass executions (thus it should be very
+ fast).</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="runOnBasicBlock">The <tt>runOnBasicBlock</tt> method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual bool</b> runOnBasicBlock(BasicBlock &BB) = 0;
+ </pre>
+
+ <p>Override this function to do the work of the <tt>BasicBlockPass</tt>. This
+ function is not allowed to inspect or modify basic blocks other than the
+ parameter, and are not allowed to modify the CFG. A true value must be returned
+ if the basic block is modified.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="doFinalization_fn">The <tt>doFinalization(Function &)</tt>
+ method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual bool</b> doFinalization(Function &F);
+ </pre>
+
+ <p>The <tt>doFinalization</tt> method is an infrequently used method that is
+ called when the pass framework has finished calling <a
+ href="#runOnBasicBlock"><tt>runOnBasicBlock</tt></a> for every BasicBlock in the
+ program being compiled. This can be used to perform per-function
+ finalization.</p>
+
+ </div>
+
+ <!-- ======================================================================= -->
+ <div class="doc_subsection">
+ <a name="MachineFunctionPass">The <tt>MachineFunctionPass</tt> class</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>A <tt>MachineFunctionPass</tt> is a part of the LLVM code generator that
+ executes on the machine-dependent representation of each LLVM function in the
+ program. A <tt>MachineFunctionPass</tt> is also a <tt>FunctionPass</tt>, so all
+ the restrictions that apply to a <tt>FunctionPass</tt> also apply to it.
+ <tt>MachineFunctionPass</tt>es also have additional restrictions. In particular,
+ <tt>MachineFunctionPass</tt>es are not allowed to do any of the following:</p>
+
+ <ol>
+ <li>Modify any LLVM Instructions, BasicBlocks or Functions.</li>
+ <li>Modify a MachineFunction other than the one currently being processed.</li>
+ <li>Add or remove MachineFunctions from the current Module.</li>
+ <li>Add or remove global variables from the current Module.</li>
+ <li>Maintain state across invocations of <a
+ href="#runOnMachineFunction"><tt>runOnMachineFunction</tt></a> (including global
+ data)</li>
+ </ol>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="runOnMachineFunction">The <tt>runOnMachineFunction(MachineFunction
+ &MF)</tt> method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual bool</b> runOnMachineFunction(MachineFunction &MF) = 0;
+ </pre>
+
+ <p><tt>runOnMachineFunction</tt> can be considered the main entry point of a
+ <tt>MachineFunctionPass</tt>; that is, you should override this method to do the
+ work of your <tt>MachineFunctionPass</tt>.</p>
+
+ <p>The <tt>runOnMachineFunction</tt> method is called on every
+ <tt>MachineFunction</tt> in a <tt>Module</tt>, so that the
+ <tt>MachineFunctionPass</tt> may perform optimizations on the machine-dependent
+ representation of the function. If you want to get at the LLVM <tt>Function</tt>
+ for the <tt>MachineFunction</tt> you're working on, use
+ <tt>MachineFunction</tt>'s <tt>getFunction()</tt> accessor method -- but
+ remember, you may not modify the LLVM <tt>Function</tt> or its contents from a
+ <tt>MachineFunctionPass</tt>.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="registration">Pass registration</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>In the <a href="#basiccode">Hello World</a> example pass we illustrated how
+ pass registration works, and discussed some of the reasons that it is used and
+ what it does. Here we discuss how and why passes are registered.</p>
+
+ <p>Passes can be registered in several different ways. Depending on the general
+ classification of the pass, you should use one of the following templates to
+ register the pass:</p>
+
+ <ul>
+ <li><b><tt>RegisterOpt</tt></b> - This template should be used when you are
+ registering a pass that logically should be available for use in the
+ '<tt>opt</tt>' utility.</li>
+
+ <li><b><tt>RegisterAnalysis</tt></b> - This template should be used when you are
+ registering a pass that logically should be available for use in the
+ '<tt>analyze</tt>' utility.</li>
+
+ <li><b><tt>RegisterPass</tt></b> - This is the generic form of the
+ <tt>Register*</tt> templates that should be used if you want your pass listed by
+ multiple or no utilities. This template takes an extra third argument that
+ specifies which tools it should be listed in. See the <a
+ href="http://llvm.cs.uiuc.edu/doxygen/PassSupport_8h-source.html">PassSupport.h</a>
+ file for more information.</li>
+
+ </ul>
+
+ <p>Regardless of how you register your pass, you must specify at least two
+ parameters. The first parameter is the name of the pass that is to be used on
+ the command line to specify that the pass should be added to a program (for
+ example <tt>opt</tt> or <tt>analyze</tt>). The second argument is the name of
+ the pass, which is to be used for the <tt>--help</tt> output of programs, as
+ well as for debug output generated by the <tt>--debug-pass</tt> option.</p>
+
+ <p>If a pass is registered to be used by the <tt>analyze</tt> utility, you
+ should implement the virtual <tt>print</tt> method:</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="print">The <tt>print</tt> method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual void</b> print(std::ostream &O, <b>const</b> Module *M) <b>const</b>;
+ </pre>
+
+ <p>The <tt>print</tt> method must be implemented by "analyses" in order to print
+ a human readable version of the analysis results. This is useful for debugging
+ an analysis itself, as well as for other people to figure out how an analysis
+ works. The <tt>analyze</tt> tool uses this method to generate its output.</p>
+
+ <p>The <tt>ostream</tt> parameter specifies the stream to write the results on,
+ and the <tt>Module</tt> parameter gives a pointer to the top level module of the
+ program that has been analyzed. Note however that this pointer may be null in
+ certain circumstances (such as calling the <tt>Pass::dump()</tt> from a
+ debugger), so it should only be used to enhance debug output, it should not be
+ depended on.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="interaction">Specifying interactions between passes</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>One of the main responsibilities of the <tt>PassManager</tt> is the make sure
+ that passes interact with each other correctly. Because <tt>PassManager</tt>
+ tries to <a href="#passmanager">optimize the execution of passes</a> it must
+ know how the passes interact with each other and what dependencies exist between
+ the various passes. To track this, each pass can declare the set of passes that
+ are required to be executed before the current pass, and the passes which are
+ invalidated by the current pass.</p>
+
+ <p>Typically this functionality is used to require that analysis results are
+ computed before your pass is run. Running arbitrary transformation passes can
+ invalidate the computed analysis results, which is what the invalidation set
+ specifies. If a pass does not implement the <tt><a
+ href="#getAnalysisUsage">getAnalysisUsage</a></tt> method, it defaults to not
+ having any prerequisite passes, and invalidating <b>all</b> other passes.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="getAnalysisUsage">The <tt>getAnalysisUsage</tt> method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual void</b> getAnalysisUsage(AnalysisUsage &Info) <b>const</b>;
+ </pre>
+
+ <p>By implementing the <tt>getAnalysisUsage</tt> method, the required and
+ invalidated sets may be specified for your transformation. The implementation
+ should fill in the <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AnalysisUsage.html">AnalysisUsage</a></tt>
+ object with information about which passes are required and not invalidated. To
+ do this, a pass may call any of the following methods on the AnalysisUsage
+ object:</p>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="AU::addRequired">The <tt>AnalysisUsage::addRequired<></tt> and <tt>AnalysisUsage::addRequiredTransitive<></tt> methods</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ If you pass requires a previous pass to be executed (an analysis for example),
+ it can use one of these methods to arrange for it to be run before your pass.
+ LLVM has many different types of analyses and passes that can be required,
+ spaning the range from <tt>DominatorSet</tt> to <tt>BreakCriticalEdges</tt>.
+ requiring <tt>BreakCriticalEdges</tt>, for example, guarantees that there will
+ be no critical edges in the CFG when your pass has been run.
+ </p>
+
+ <p>
+ Some analyses chain to other analyses to do their job. For example, an <a
+ href="AliasAnalysis.html">AliasAnalysis</a> implementation is required to <a
+ href="AliasAnalysis.html#chaining">chain</a> to other alias analysis passes. In
+ cases where analyses chain, the <tt>addRequiredTransitive</tt> method should be
+ used instead of the <tt>addRequired</tt> method. This informs the PassManager
+ that the transitively required pass should be alive as long as the requiring
+ pass is.
+ </p>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="AU::addPreserved">The <tt>AnalysisUsage::addPreserved<></tt> method</a>
+ </div>
+
+ <div class="doc_text">
+ <p>
+ One of the jobs of the PassManager is to optimize how and when analyses are run.
+ In particular, it attempts to avoid recomputing data unless it needs to. For
+ this reason, passes are allowed to declare that they preserve (i.e., they don't
+ invalidate) an existing analysis if it's available. For example, a simple
+ constant folding pass would not modify the CFG, so it can't possible effect the
+ results of dominator analysis. By default, all passes are assumed to invalidate
+ all others.
+ </p>
+
+ <p>
+ The <tt>AnalysisUsage</tt> class provides several methods which are useful in
+ certain circumstances that are related to <tt>addPreserved</tt>. In particular,
+ the <tt>setPreservesAll</tt> method can be called to indicate that the pass does
+ not modify the LLVM program at all (which is true for analyses), and the
+ <tt>setPreservesCFG</tt> method can be used by transformations that change
+ instructions in the program but do not modify the CFG or terminator instructions
+ (note that this property is implicitly set for <a
+ href="#BasicBlockPass">BasicBlockPass</a>'s).
+ </p>
+
+ <p>
+ <tt>addPreserved</tt> is particularly useful for transformations like
+ <tt>BreakCriticalEdges</tt>. This pass knows how to update a small set of loop
+ and dominator related analyses if they exist, so it can preserve them, despite
+ the fact that it hacks on the CFG.
+ </p>
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="AU::examples">Example implementations of <tt>getAnalysisUsage</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <i>// This is an example implementation from an analysis, which does not modify
+ // the program at all, yet has a prerequisite.</i>
+ <b>void</b> <a href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1PostDominanceFrontier.html">PostDominanceFrontier</a>::getAnalysisUsage(AnalysisUsage &AU) <b>const</b> {
+ AU.setPreservesAll();
+ AU.addRequired<<a href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1PostDominatorTree.html">PostDominatorTree</a>>();
+ }
+ </pre>
+
+ <p>and:</p>
+
+ <pre>
+ <i>// This example modifies the program, but does not modify the CFG</i>
+ <b>void</b> <a href="http://llvm.cs.uiuc.edu/doxygen/structLICM.html">LICM</a>::getAnalysisUsage(AnalysisUsage &AU) <b>const</b> {
+ AU.setPreservesCFG();
+ AU.addRequired<<a href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1LoopInfo.html">LoopInfo</a>>();
+ }
+ </pre>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="getAnalysis">The <tt>getAnalysis<></tt> and <tt>getAnalysisToUpdate<></tt> methods</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>Pass::getAnalysis<></tt> method is automatically inherited by
+ your class, providing you with access to the passes that you declared that you
+ required with the <a href="#getAnalysisUsage"><tt>getAnalysisUsage</tt></a>
+ method. It takes a single template argument that specifies which pass class you
+ want, and returns a reference to that pass. For example:</p>
+
+ <pre>
+ bool LICM::runOnFunction(Function &F) {
+ LoopInfo &LI = getAnalysis<LoopInfo>();
+ ...
+ }
+ </pre>
+
+ <p>This method call returns a reference to the pass desired. You may get a
+ runtime assertion failure if you attempt to get an analysis that you did not
+ declare as required in your <a
+ href="#getAnalysisUsage"><tt>getAnalysisUsage</tt></a> implementation. This
+ method can be called by your <tt>run*</tt> method implementation, or by any
+ other local method invoked by your <tt>run*</tt> method.</p>
+
+ <p>
+ If your pass is capable of updating analyses if they exist (e.g.,
+ <tt>BreakCriticalEdges</tt>, as described above), you can use the
+ <tt>getAnalysisToUpdate</tt> method, which returns a pointer to the analysis if
+ it is active. For example:</p>
+
+ <pre>
+ ...
+ if (DominatorSet *DS = getAnalysisToUpdate<DominatorSet>()) {
+ <i>// A DominatorSet is active. This code will update it.</i>
+ }
+ ...
+ </pre>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="analysisgroup">Implementing Analysis Groups</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Now that we understand the basics of how passes are defined, how the are
+ used, and how they are required from other passes, it's time to get a little bit
+ fancier. All of the pass relationships that we have seen so far are very
+ simple: one pass depends on one other specific pass to be run before it can run.
+ For many applications, this is great, for others, more flexibility is
+ required.</p>
+
+ <p>In particular, some analyses are defined such that there is a single simple
+ interface to the analysis results, but multiple ways of calculating them.
+ Consider alias analysis for example. The most trivial alias analysis returns
+ "may alias" for any alias query. The most sophisticated analysis a
+ flow-sensitive, context-sensitive interprocedural analysis that can take a
+ significant amount of time to execute (and obviously, there is a lot of room
+ between these two extremes for other implementations). To cleanly support
+ situations like this, the LLVM Pass Infrastructure supports the notion of
+ Analysis Groups.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="agconcepts">Analysis Group Concepts</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>An Analysis Group is a single simple interface that may be implemented by
+ multiple different passes. Analysis Groups can be given human readable names
+ just like passes, but unlike passes, they need not derive from the <tt>Pass</tt>
+ class. An analysis group may have one or more implementations, one of which is
+ the "default" implementation.</p>
+
+ <p>Analysis groups are used by client passes just like other passes are: the
+ <tt>AnalysisUsage::addRequired()</tt> and <tt>Pass::getAnalysis()</tt> methods.
+ In order to resolve this requirement, the <a href="#passmanager">PassManager</a>
+ scans the available passes to see if any implementations of the analysis group
+ are available. If none is available, the default implementation is created for
+ the pass to use. All standard rules for <A href="#interaction">interaction
+ between passes</a> still apply.</p>
+
+ <p>Although <a href="#registration">Pass Registration</a> is optional for normal
+ passes, all analysis group implementations must be registered, and must use the
+ <A href="#registerag"><tt>RegisterAnalysisGroup</tt></a> template to join the
+ implementation pool. Also, a default implementation of the interface
+ <b>must</b> be registered with <A
+ href="#registerag"><tt>RegisterAnalysisGroup</tt></a>.</p>
+
+ <p>As a concrete example of an Analysis Group in action, consider the <a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>
+ analysis group. The default implementation of the alias analysis interface (the
+ <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/structBasicAliasAnalysis.html">basicaa</a></tt>
+ pass) just does a few simple checks that don't require significant analysis to
+ compute (such as: two different globals can never alias each other, etc).
+ Passes that use the <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a></tt>
+ interface (for example the <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/classGCSE.html">gcse</a></tt> pass), do
+ not care which implementation of alias analysis is actually provided, they just
+ use the designated interface.</p>
+
+ <p>From the user's perspective, commands work just like normal. Issuing the
+ command '<tt>opt -gcse ...</tt>' will cause the <tt>basicaa</tt> class to be
+ instantiated and added to the pass sequence. Issuing the command '<tt>opt
+ -somefancyaa -gcse ...</tt>' will cause the <tt>gcse</tt> pass to use the
+ <tt>somefancyaa</tt> alias analysis (which doesn't actually exist, it's just a
+ hypothetical example) instead.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="registerag">Using <tt>RegisterAnalysisGroup</tt></a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>The <tt>RegisterAnalysisGroup</tt> template is used to register the analysis
+ group itself as well as add pass implementations to the analysis group. First,
+ an analysis should be registered, with a human readable name provided for it.
+ Unlike registration of passes, there is no command line argument to be specified
+ for the Analysis Group Interface itself, because it is "abstract":</p>
+
+ <pre>
+ <b>static</b> RegisterAnalysisGroup<<a href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>> A("<i>Alias Analysis</i>");
+ </pre>
+
+ <p>Once the analysis is registered, passes can declare that they are valid
+ implementations of the interface by using the following code:</p>
+
+ <pre>
+ <b>namespace</b> {
+ //<i> Analysis Group implementations <b>must</b> be registered normally...</i>
+ RegisterOpt<FancyAA>
+ B("<i>somefancyaa</i>", "<i>A more complex alias analysis implementation</i>");
+
+ //<i> Declare that we implement the AliasAnalysis interface</i>
+ RegisterAnalysisGroup<<a href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>, FancyAA> C;
+ }
+ </pre>
+
+ <p>This just shows a class <tt>FancyAA</tt> that is registered normally, then
+ uses the <tt>RegisterAnalysisGroup</tt> template to "join" the <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a></tt>
+ analysis group. Every implementation of an analysis group should join using
+ this template. A single pass may join multiple different analysis groups with
+ no problem.</p>
+
+ <pre>
+ <b>namespace</b> {
+ //<i> Analysis Group implementations <b>must</b> be registered normally...</i>
+ RegisterOpt<<a href="http://llvm.cs.uiuc.edu/doxygen/structBasicAliasAnalysis.html">BasicAliasAnalysis</a>>
+ D("<i>basicaa</i>", "<i>Basic Alias Analysis (default AA impl)</i>");
+
+ //<i> Declare that we implement the AliasAnalysis interface</i>
+ RegisterAnalysisGroup<<a href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>, <a href="http://llvm.cs.uiuc.edu/doxygen/structBasicAliasAnalysis.html">BasicAliasAnalysis</a>, <b>true</b>> E;
+ }
+ </pre>
+
+ <p>Here we show how the default implementation is specified (using the extra
+ argument to the <tt>RegisterAnalysisGroup</tt> template). There must be exactly
+ one default implementation available at all times for an Analysis Group to be
+ used. Here we declare that the <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/structBasicAliasAnalysis.html">BasicAliasAnalysis</a></tt>
+ pass is the default implementation for the interface.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="passmanager">What PassManager does</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>The <a
+ href="http://llvm.cs.uiuc.edu/doxygen/PassManager_8h-source.html"><tt>PassManager</tt></a>
+ <a
+ href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1PassManager.html">class</a>
+ takes a list of passes, ensures their <a href="#interaction">prerequisites</a>
+ are set up correctly, and then schedules passes to run efficiently. All of the
+ LLVM tools that run passes use the <tt>PassManager</tt> for execution of these
+ passes.</p>
+
+ <p>The <tt>PassManager</tt> does two main things to try to reduce the execution
+ time of a series of passes:</p>
+
+ <ol>
+ <li><b>Share analysis results</b> - The PassManager attempts to avoid
+ recomputing analysis results as much as possible. This means keeping track of
+ which analyses are available already, which analyses get invalidated, and which
+ analyses are needed to be run for a pass. An important part of work is that the
+ <tt>PassManager</tt> tracks the exact lifetime of all analysis results, allowing
+ it to <a href="#releaseMemory">free memory</a> allocated to holding analysis
+ results as soon as they are no longer needed.</li>
+
+ <li><b>Pipeline the execution of passes on the program</b> - The
+ <tt>PassManager</tt> attempts to get better cache and memory usage behavior out
+ of a series of passes by pipelining the passes together. This means that, given
+ a series of consequtive <a href="#FunctionPass"><tt>FunctionPass</tt></a>'s, it
+ will execute all of the <a href="#FunctionPass"><tt>FunctionPass</tt></a>'s on
+ the first function, then all of the <a
+ href="#FunctionPass"><tt>FunctionPass</tt></a>es on the second function,
+ etc... until the entire program has been run through the passes.
+
+ <p>This improves the cache behavior of the compiler, because it is only touching
+ the LLVM program representation for a single function at a time, instead of
+ traversing the entire program. It reduces the memory consumption of compiler,
+ because, for example, only one <a
+ href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1DominatorSet.html"><tt>DominatorSet</tt></a>
+ needs to be calculated at a time. This also makes it possible some <a
+ href="#SMP">interesting enhancements</a> in the future.</p></li>
+
+ </ol>
+
+ <p>The effectiveness of the <tt>PassManager</tt> is influenced directly by how
+ much information it has about the behaviors of the passes it is scheduling. For
+ example, the "preserved" set is intentionally conservative in the face of an
+ unimplemented <a href="#getAnalysisUsage"><tt>getAnalysisUsage</tt></a> method.
+ Not implementing when it should be implemented will have the effect of not
+ allowing any analysis results to live across the execution of your pass.</p>
+
+ <p>The <tt>PassManager</tt> class exposes a <tt>--debug-pass</tt> command line
+ options that is useful for debugging pass execution, seeing how things work, and
+ diagnosing when you should be preserving more analyses than you currently are
+ (To get information about all of the variants of the <tt>--debug-pass</tt>
+ option, just type '<tt>opt --help-hidden</tt>').</p>
+
+ <p>By using the <tt>--debug-pass=Structure</tt> option, for example, we can see
+ how our <a href="#basiccode">Hello World</a> pass interacts with other passes.
+ Lets try it out with the <tt>gcse</tt> and <tt>licm</tt> passes:</p>
+
+ <pre>
+ $ opt -load ../../../lib/Debug/libhello.so -gcse -licm --debug-pass=Structure < hello.bc > /dev/null
+ Module Pass Manager
+ Function Pass Manager
+ Dominator Set Construction
+ Immediate Dominators Construction
+ Global Common Subexpression Elimination
+ -- Immediate Dominators Construction
+ -- Global Common Subexpression Elimination
+ Natural Loop Construction
+ Loop Invariant Code Motion
+ -- Natural Loop Construction
+ -- Loop Invariant Code Motion
+ Module Verifier
+ -- Dominator Set Construction
+ -- Module Verifier
+ Bytecode Writer
+ --Bytecode Writer
+ </pre>
+
+ <p>This output shows us when passes are constructed and when the analysis
+ results are known to be dead (prefixed with '<tt>--</tt>'). Here we see that
+ GCSE uses dominator and immediate dominator information to do its job. The LICM
+ pass uses natural loop information, which uses dominator sets, but not immediate
+ dominators. Because immediate dominators are no longer useful after the GCSE
+ pass, it is immediately destroyed. The dominator sets are then reused to
+ compute natural loop information, which is then used by the LICM pass.</p>
+
+ <p>After the LICM pass, the module verifier runs (which is automatically added
+ by the '<tt>opt</tt>' tool), which uses the dominator set to check that the
+ resultant LLVM code is well formed. After it finishes, the dominator set
+ information is destroyed, after being computed once, and shared by three
+ passes.</p>
+
+ <p>Lets see how this changes when we run the <a href="#basiccode">Hello
+ World</a> pass in between the two passes:</p>
+
+ <pre>
+ $ opt -load ../../../lib/Debug/libhello.so -gcse -hello -licm --debug-pass=Structure < hello.bc > /dev/null
+ Module Pass Manager
+ Function Pass Manager
+ Dominator Set Construction
+ Immediate Dominators Construction
+ Global Common Subexpression Elimination
+ <b>-- Dominator Set Construction</b>
+ -- Immediate Dominators Construction
+ -- Global Common Subexpression Elimination
+ <b> Hello World Pass
+ -- Hello World Pass
+ Dominator Set Construction</b>
+ Natural Loop Construction
+ Loop Invariant Code Motion
+ -- Natural Loop Construction
+ -- Loop Invariant Code Motion
+ Module Verifier
+ -- Dominator Set Construction
+ -- Module Verifier
+ Bytecode Writer
+ --Bytecode Writer
+ Hello: __main
+ Hello: puts
+ Hello: main
+ </pre>
+
+ <p>Here we see that the <a href="#basiccode">Hello World</a> pass has killed the
+ Dominator Set pass, even though it doesn't modify the code at all! To fix this,
+ we need to add the following <a
+ href="#getAnalysisUsage"><tt>getAnalysisUsage</tt></a> method to our pass:</p>
+
+ <pre>
+ <i>// We don't modify the program, so we preserve all analyses</i>
+ <b>virtual void</b> getAnalysisUsage(AnalysisUsage &AU) <b>const</b> {
+ AU.setPreservesAll();
+ }
+ </pre>
+
+ <p>Now when we run our pass, we get this output:</p>
+
+ <pre>
+ $ opt -load ../../../lib/Debug/libhello.so -gcse -hello -licm --debug-pass=Structure < hello.bc > /dev/null
+ Pass Arguments: -gcse -hello -licm
+ Module Pass Manager
+ Function Pass Manager
+ Dominator Set Construction
+ Immediate Dominators Construction
+ Global Common Subexpression Elimination
+ -- Immediate Dominators Construction
+ -- Global Common Subexpression Elimination
+ Hello World Pass
+ -- Hello World Pass
+ Natural Loop Construction
+ Loop Invariant Code Motion
+ -- Loop Invariant Code Motion
+ -- Natural Loop Construction
+ Module Verifier
+ -- Dominator Set Construction
+ -- Module Verifier
+ Bytecode Writer
+ --Bytecode Writer
+ Hello: __main
+ Hello: puts
+ Hello: main
+ </pre>
+
+ <p>Which shows that we don't accidentally invalidate dominator information
+ anymore, and therefore do not have to compute it twice.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="releaseMemory">The <tt>releaseMemory</tt> method</a>
+ </div>
+
+ <div class="doc_text">
+
+ <pre>
+ <b>virtual void</b> releaseMemory();
+ </pre>
+
+ <p>The <tt>PassManager</tt> automatically determines when to compute analysis
+ results, and how long to keep them around for. Because the lifetime of the pass
+ object itself is effectively the entire duration of the compilation process, we
+ need some way to free analysis results when they are no longer useful. The
+ <tt>releaseMemory</tt> virtual method is the way to do this.</p>
+
+ <p>If you are writing an analysis or any other pass that retains a significant
+ amount of state (for use by another pass which "requires" your pass and uses the
+ <a href="#getAnalysis">getAnalysis</a> method) you should implement
+ <tt>releaseMEmory</tt> to, well, release the memory allocated to maintain this
+ internal state. This method is called after the <tt>run*</tt> method for the
+ class, before the next call of <tt>run*</tt> in your pass.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="debughints">Using GDB with dynamically loaded passes</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Unfortunately, using GDB with dynamically loaded passes is not as easy as it
+ should be. First of all, you can't set a breakpoint in a shared object that has
+ not been loaded yet, and second of all there are problems with inlined functions
+ in shared objects. Here are some suggestions to debugging your pass with
+ GDB.</p>
+
+ <p>For sake of discussion, I'm going to assume that you are debugging a
+ transformation invoked by <tt>opt</tt>, although nothing described here depends
+ on that.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="breakpoint">Setting a breakpoint in your pass</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>First thing you do is start <tt>gdb</tt> on the <tt>opt</tt> process:</p>
+
+ <pre>
+ $ <b>gdb opt</b>
+ GNU gdb 5.0
+ Copyright 2000 Free Software Foundation, Inc.
+ GDB is free software, covered by the GNU General Public License, and you are
+ welcome to change it and/or distribute copies of it under certain conditions.
+ Type "show copying" to see the conditions.
+ There is absolutely no warranty for GDB. Type "show warranty" for details.
+ This GDB was configured as "sparc-sun-solaris2.6"...
+ (gdb)
+ </pre>
+
+ <p>Note that <tt>opt</tt> has a lot of debugging information in it, so it takes
+ time to load. Be patient. Since we cannot set a breakpoint in our pass yet
+ (the shared object isn't loaded until runtime), we must execute the process, and
+ have it stop before it invokes our pass, but after it has loaded the shared
+ object. The most foolproof way of doing this is to set a breakpoint in
+ <tt>PassManager::run</tt> and then run the process with the arguments you
+ want:</p>
+
+ <pre>
+ (gdb) <b>break PassManager::run</b>
+ Breakpoint 1 at 0x2413bc: file Pass.cpp, line 70.
+ (gdb) <b>run test.bc -load $(LLVMTOP)/llvm/lib/Debug/[libname].so -[passoption]</b>
+ Starting program: opt test.bc -load $(LLVMTOP)/llvm/lib/Debug/[libname].so -[passoption]
+ Breakpoint 1, PassManager::run (this=0xffbef174, M=@0x70b298) at Pass.cpp:70
+ 70 bool PassManager::run(Module &M) { return PM->run(M); }
+ (gdb)
+ </pre>
+
+ <p>Once the <tt>opt</tt> stops in the <tt>PassManager::run</tt> method you are
+ now free to set breakpoints in your pass so that you can trace through execution
+ or do other standard debugging stuff.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="debugmisc">Miscellaneous Problems</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Once you have the basics down, there are a couple of problems that GDB has,
+ some with solutions, some without.</p>
+
+ <ul>
+ <li>Inline functions have bogus stack information. In general, GDB does a
+ pretty good job getting stack traces and stepping through inline functions.
+ When a pass is dynamically loaded however, it somehow completely loses this
+ capability. The only solution I know of is to de-inline a function (move it
+ from the body of a class to a .cpp file).</li>
+
+ <li>Restarting the program breaks breakpoints. After following the information
+ above, you have succeeded in getting some breakpoints planted in your pass. Nex
+ thing you know, you restart the program (i.e., you type '<tt>run</tt>' again),
+ and you start getting errors about breakpoints being unsettable. The only way I
+ have found to "fix" this problem is to <tt>delete</tt> the breakpoints that are
+ already set in your pass, run the program, and re-set the breakpoints once
+ execution stops in <tt>PassManager::run</tt>.</li>
+
+ </ul>
+
+ <p>Hopefully these tips will help with common case debugging situations. If
+ you'd like to contribute some tips of your own, just contact <a
+ href="mailto:sabre at nondot.org">Chris</a>.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <div class="doc_section">
+ <a name="future">Future extensions planned</a>
+ </div>
+ <!-- *********************************************************************** -->
+
+ <div class="doc_text">
+
+ <p>Although the LLVM Pass Infrastructure is very capable as it stands, and does
+ some nifty stuff, there are things we'd like to add in the future. Here is
+ where we are going:</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="SMP">Multithreaded LLVM</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Multiple CPU machines are becoming more common and compilation can never be
+ fast enough: obviously we should allow for a multithreaded compiler. Because of
+ the semantics defined for passes above (specifically they cannot maintain state
+ across invocations of their <tt>run*</tt> methods), a nice clean way to
+ implement a multithreaded compiler would be for the <tt>PassManager</tt> class
+ to create multiple instances of each pass object, and allow the separate
+ instances to be hacking on different parts of the program at the same time.</p>
+
+ <p>This implementation would prevent each of the passes from having to implement
+ multithreaded constructs, requiring only the LLVM core to have locking in a few
+ places (for global resources). Although this is a simple extension, we simply
+ haven't had time (or multiprocessor machines, thus a reason) to implement this.
+ Despite that, we have kept the LLVM passes SMP ready, and you should too.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="ModuleSource">A new <tt>ModuleSource</tt> interface</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Currently, the <tt>PassManager</tt>'s <tt>run</tt> method takes a <tt><a
+ href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1Module.html">Module</a></tt>
+ as input, and runs all of the passes on this module. The problem with this
+ approach is that none of the <tt>PassManager</tt> features can be used for
+ timing and debugging the actual <b>loading</b> of the module from disk or
+ standard input.</p>
+
+ <p>To solve this problem, eventually the <tt>PassManager</tt> class will accept
+ a <tt>ModuleSource</tt> object instead of a Module itself. When complete, this
+ will also allow for streaming of functions out of the bytecode representation,
+ allowing us to avoid holding the entire program in memory at once if we only are
+ dealing with <a href="#FunctionPass">FunctionPass</a>es.</p>
+
+ <p>As part of a different issue, eventually the bytecode loader will be extended
+ to allow on-demand loading of functions from the bytecode representation, in
+ order to better support the runtime reoptimizer. The bytecode format is already
+ capable of this, the loader just needs to be reworked a bit.</p>
+
+ </div>
+
+ <!-- _______________________________________________________________________ -->
+ <div class="doc_subsubsection">
+ <a name="PassFunctionPass"><tt>Pass</tt>es requiring <tt>FunctionPass</tt>es</a>
+ </div>
+
+ <div class="doc_text">
+
+ <p>Currently it is illegal for a <a href="#Pass"><tt>Pass</tt></a> to require a
+ <a href="#FunctionPass"><tt>FunctionPass</tt></a>. This is because there is
+ only one instance of the <a href="#FunctionPass"><tt>FunctionPass</tt></a>
+ object ever created, thus nowhere to store information for all of the functions
+ in the program at the same time. Although this has come up a couple of times
+ before, this has always been worked around by factoring one big complicated pass
+ into a global and an interprocedural part, both of which are distinct. In the
+ future, it would be nice to have this though.</p>
+
+ <p>Note that it is no problem for a <a
+ href="#FunctionPass"><tt>FunctionPass</tt></a> to require the results of a <a
+ href="#Pass"><tt>Pass</tt></a>, only the other way around.</p>
+
+ </div>
+
+ <!-- *********************************************************************** -->
+ <hr>
+ <address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
+
+ <a href="mailto:sabre at nondot.org">Chris Lattner</a><br>
+ <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date: 2004/03/19 17:38:11 $
+ </address>
+
+ </body>
+ </html>
Index: llvm-www/releases/1.2/docs/doxygen.cfg
diff -c /dev/null llvm-www/releases/1.2/docs/doxygen.cfg:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/doxygen.cfg Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,898 ----
+ # Doxyfile 1.2.13.1
+
+ # This file describes the settings to be used by the documentation system
+ # doxygen (www.doxygen.org) for a project
+ #
+ # All text after a hash (#) is considered a comment and will be ignored
+ # The format is:
+ # TAG = value [value, ...]
+ # For lists items can also be appended using:
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+ # Values that contain spaces should be placed between quotes (" ")
+
+ #---------------------------------------------------------------------------
+ # General configuration options
+ #---------------------------------------------------------------------------
+
+ # The PROJECT_NAME tag is a single word (or a sequence of words surrounded
+ # by quotes) that should identify the project.
+
+ PROJECT_NAME = LLVM
+
+ # The PROJECT_NUMBER tag can be used to enter a project or revision number.
+ # This could be handy for archiving the generated documentation or
+ # if some version control system is used.
+
+ PROJECT_NUMBER =
+
+ # The OUTPUT_DIRECTORY tag is used to specify the (relative or absolute)
+ # base path where the generated documentation will be put.
+ # If a relative path is entered, it will be relative to the location
+ # where doxygen was started. If left blank the current directory will be used.
+
+ OUTPUT_DIRECTORY = doxygen
+
+ # The OUTPUT_LANGUAGE tag is used to specify the language in which all
+ # documentation generated by doxygen is written. Doxygen will use this
+ # information to generate all constant output in the proper language.
+ # The default language is English, other supported languages are:
+ # Brazilian, Chinese, Croatian, Czech, Danish, Dutch, Finnish, French,
+ # German, Greek, Hungarian, Italian, Japanese, Korean, Norwegian, Polish,
+ # Portuguese, Romanian, Russian, Slovak, Slovene, Spanish and Swedish.
+
+ OUTPUT_LANGUAGE = English
+
+ # If the EXTRACT_ALL tag is set to YES doxygen will assume all entities in
+ # documentation are documented, even if no documentation was available.
+ # Private class members and static file members will be hidden unless
+ # the EXTRACT_PRIVATE and EXTRACT_STATIC tags are set to YES
+
+ EXTRACT_ALL = YES
+
+ # If the EXTRACT_PRIVATE tag is set to YES all private members of a class
+ # will be included in the documentation.
+
+ EXTRACT_PRIVATE = NO
+
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+ # will be included in the documentation.
+
+ EXTRACT_STATIC = YES
+
+ # If the EXTRACT_LOCAL_CLASSES tag is set to YES classes (and structs)
+ # defined locally in source files will be included in the documentation.
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+ EXTRACT_LOCAL_CLASSES = YES
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+ REPEAT_BRIEF = YES
+
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+ ALWAYS_DETAILED_SEC = NO
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+
+ CASE_SENSE_NAMES = YES
+
+ # If the SHORT_NAMES tag is set to YES, doxygen will generate much shorter
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+ SHORT_NAMES = NO
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+
+ JAVADOC_AUTOBRIEF = NO
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+ # If the INHERIT_DOCS tag is set to YES (the default) then an undocumented
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+ GENERATE_TODOLIST = YES
+
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+
+ GENERATE_TESTLIST = YES
+
+ # The GENERATE_BUGLIST tag can be used to enable (YES) or
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+
+ GENERATE_BUGLIST = YES
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+ # This tag can be used to specify a number of aliases that acts
+ # as commands in the documentation. An alias has the form "name=value".
+ # For example adding "sideeffect=\par Side Effects:\n" will allow you to
+ # put the command \sideeffect (or @sideeffect) in the documentation, which
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+ # You can put \n's in the value part of an alias to insert newlines.
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+ ALIASES =
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+ # The ENABLED_SECTIONS tag can be used to enable conditional
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+ ENABLED_SECTIONS =
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+ # command in the documentation regardless of this setting.
+
+ MAX_INITIALIZER_LINES = 30
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+ # For instance some of the names that are used will be different. The list
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+ OPTIMIZE_OUTPUT_FOR_C = NO
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+ # The INPUT tag can be used to specify the files and/or directories that contain
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+ # If the value of the INPUT tag contains directories, you can use the
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+ # *.h++ *.idl
+
+ FILE_PATTERNS =
+
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+ EXCLUDE = ../test ../include/boost
+
+ # If the value of the INPUT tag contains directories, you can use the
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+ EXCLUDE_PATTERNS =
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+ # The EXAMPLE_PATH tag can be used to specify one or more files or
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+ EXAMPLE_PATH =
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+ # If the value of the EXAMPLE_PATH tag contains directories, you can use the
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+ # and *.h) to filter out the source-files in the directories. If left
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+ EXAMPLE_PATTERNS =
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+ EXAMPLE_RECURSIVE = NO
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+
+ # The INPUT_FILTER tag can be used to specify a program that doxygen should
+ # invoke to filter for each input file. Doxygen will invoke the filter program
+ # by executing (via popen()) the command <filter> <input-file>, where <filter>
+ # is the value of the INPUT_FILTER tag, and <input-file> is the name of an
+ # input file. Doxygen will then use the output that the filter program writes
+ # to standard output.
+
+ INPUT_FILTER =
+
+ # If the FILTER_SOURCE_FILES tag is set to YES, the input filter (if set using
+ # INPUT_FILTER) will be used to filter the input files when producing source
+ # files to browse.
+
+ FILTER_SOURCE_FILES = NO
+
+ #---------------------------------------------------------------------------
+ # configuration options related to source browsing
+ #---------------------------------------------------------------------------
+
+ # If the SOURCE_BROWSER tag is set to YES then a list of source files will
+ # be generated. Documented entities will be cross-referenced with these sources.
+
+ SOURCE_BROWSER = YES
+
+ # Setting the INLINE_SOURCES tag to YES will include the body
+ # of functions and classes directly in the documentation.
+
+ INLINE_SOURCES = NO
+
+ # If the REFERENCED_BY_RELATION tag is set to YES (the default)
+ # then for each documented function all documented
+ # functions referencing it will be listed.
+
+ REFERENCED_BY_RELATION = YES
+
+ # If the REFERENCES_RELATION tag is set to YES (the default)
+ # then for each documented function all documented entities
+ # called/used by that function will be listed.
+
+ REFERENCES_RELATION = YES
+
+ #---------------------------------------------------------------------------
+ # configuration options related to the alphabetical class index
+ #---------------------------------------------------------------------------
+
+ # If the ALPHABETICAL_INDEX tag is set to YES, an alphabetical index
+ # of all compounds will be generated. Enable this if the project
+ # contains a lot of classes, structs, unions or interfaces.
+
+ ALPHABETICAL_INDEX = YES
+
+ # If the alphabetical index is enabled (see ALPHABETICAL_INDEX) then
+ # the COLS_IN_ALPHA_INDEX tag can be used to specify the number of columns
+ # in which this list will be split (can be a number in the range [1..20])
+
+ COLS_IN_ALPHA_INDEX = 5
+
+ # In case all classes in a project start with a common prefix, all
+ # classes will be put under the same header in the alphabetical index.
+ # The IGNORE_PREFIX tag can be used to specify one or more prefixes that
+ # should be ignored while generating the index headers.
+
+ IGNORE_PREFIX =
+
+ #---------------------------------------------------------------------------
+ # configuration options related to the HTML output
+ #---------------------------------------------------------------------------
+
+ # If the GENERATE_HTML tag is set to YES (the default) Doxygen will
+ # generate HTML output.
+
+ GENERATE_HTML = YES
+
+ # The HTML_OUTPUT tag is used to specify where the HTML docs will be put.
+ # If a relative path is entered the value of OUTPUT_DIRECTORY will be
+ # put in front of it. If left blank `html' will be used as the default path.
+
+ HTML_OUTPUT = .
+
+ # The HTML_HEADER tag can be used to specify a personal HTML header for
+ # each generated HTML page. If it is left blank doxygen will generate a
+ # standard header.
+
+ HTML_HEADER = doxygen.header
+
+ # The HTML_FOOTER tag can be used to specify a personal HTML footer for
+ # each generated HTML page. If it is left blank doxygen will generate a
+ # standard footer.
+
+ HTML_FOOTER = doxygen.footer
+
+ # The HTML_STYLESHEET tag can be used to specify a user defined cascading
+ # style sheet that is used by each HTML page. It can be used to
+ # fine-tune the look of the HTML output. If the tag is left blank doxygen
+ # will generate a default style sheet
+
+ HTML_STYLESHEET = doxygen.css
+
+ # If the HTML_ALIGN_MEMBERS tag is set to YES, the members of classes,
+ # files or namespaces will be aligned in HTML using tables. If set to
+ # NO a bullet list will be used.
+
+ HTML_ALIGN_MEMBERS = YES
+
+ # If the GENERATE_HTMLHELP tag is set to YES, additional index files
+ # will be generated that can be used as input for tools like the
+ # Microsoft HTML help workshop to generate a compressed HTML help file (.chm)
+ # of the generated HTML documentation.
+
+ GENERATE_HTMLHELP = NO
+
+ # If the GENERATE_HTMLHELP tag is set to YES, the GENERATE_CHI flag
+ # controls if a separate .chi index file is generated (YES) or that
+ # it should be included in the master .chm file (NO).
+
+ GENERATE_CHI = NO
+
+ # If the GENERATE_HTMLHELP tag is set to YES, the BINARY_TOC flag
+ # controls whether a binary table of contents is generated (YES) or a
+ # normal table of contents (NO) in the .chm file.
+
+ BINARY_TOC = NO
+
+ # The TOC_EXPAND flag can be set to YES to add extra items for group members
+ # to the contents of the Html help documentation and to the tree view.
+
+ TOC_EXPAND = NO
+
+ # The DISABLE_INDEX tag can be used to turn on/off the condensed index at
+ # top of each HTML page. The value NO (the default) enables the index and
+ # the value YES disables it.
+
+ DISABLE_INDEX = NO
+
+ # This tag can be used to set the number of enum values (range [1..20])
+ # that doxygen will group on one line in the generated HTML documentation.
+
+ ENUM_VALUES_PER_LINE = 4
+
+ # If the GENERATE_TREEVIEW tag is set to YES, a side panel will be
+ # generated containing a tree-like index structure (just like the one that
+ # is generated for HTML Help). For this to work a browser that supports
+ # JavaScript and frames is required (for instance Mozilla, Netscape 4.0+,
+ # or Internet explorer 4.0+). Note that for large projects the tree generation
+ # can take a very long time. In such cases it is better to disable this feature.
+ # Windows users are probably better off using the HTML help feature.
+
+ GENERATE_TREEVIEW = NO
+
+ # If the treeview is enabled (see GENERATE_TREEVIEW) then this tag can be
+ # used to set the initial width (in pixels) of the frame in which the tree
+ # is shown.
+
+ TREEVIEW_WIDTH = 250
+
+ #---------------------------------------------------------------------------
+ # configuration options related to the LaTeX output
+ #---------------------------------------------------------------------------
+
+ # If the GENERATE_LATEX tag is set to YES (the default) Doxygen will
+ # generate Latex output.
+
+ GENERATE_LATEX = NO
+
+ # The LATEX_OUTPUT tag is used to specify where the LaTeX docs will be put.
+ # If a relative path is entered the value of OUTPUT_DIRECTORY will be
+ # put in front of it. If left blank `latex' will be used as the default path.
+
+ LATEX_OUTPUT =
+
+ # If the COMPACT_LATEX tag is set to YES Doxygen generates more compact
+ # LaTeX documents. This may be useful for small projects and may help to
+ # save some trees in general.
+
+ COMPACT_LATEX = NO
+
+ # The PAPER_TYPE tag can be used to set the paper type that is used
+ # by the printer. Possible values are: a4, a4wide, letter, legal and
+ # executive. If left blank a4wide will be used.
+
+ PAPER_TYPE = a4wide
+
+ # The EXTRA_PACKAGES tag can be to specify one or more names of LaTeX
+ # packages that should be included in the LaTeX output.
+
+ EXTRA_PACKAGES =
+
+ # The LATEX_HEADER tag can be used to specify a personal LaTeX header for
+ # the generated latex document. The header should contain everything until
+ # the first chapter. If it is left blank doxygen will generate a
+ # standard header. Notice: only use this tag if you know what you are doing!
+
+ LATEX_HEADER =
+
+ # If the PDF_HYPERLINKS tag is set to YES, the LaTeX that is generated
+ # is prepared for conversion to pdf (using ps2pdf). The pdf file will
+ # contain links (just like the HTML output) instead of page references
+ # This makes the output suitable for online browsing using a pdf viewer.
+
+ PDF_HYPERLINKS = NO
+
+ # If the USE_PDFLATEX tag is set to YES, pdflatex will be used instead of
+ # plain latex in the generated Makefile. Set this option to YES to get a
+ # higher quality PDF documentation.
+
+ USE_PDFLATEX = NO
+
+ # If the LATEX_BATCHMODE tag is set to YES, doxygen will add the \\batchmode.
+ # command to the generated LaTeX files. This will instruct LaTeX to keep
+ # running if errors occur, instead of asking the user for help.
+ # This option is also used when generating formulas in HTML.
+
+ LATEX_BATCHMODE = NO
+
+ #---------------------------------------------------------------------------
+ # configuration options related to the RTF output
+ #---------------------------------------------------------------------------
+
+ # If the GENERATE_RTF tag is set to YES Doxygen will generate RTF output
+ # The RTF output is optimised for Word 97 and may not look very pretty with
+ # other RTF readers or editors.
+
+ GENERATE_RTF = NO
+
+ # The RTF_OUTPUT tag is used to specify where the RTF docs will be put.
+ # If a relative path is entered the value of OUTPUT_DIRECTORY will be
+ # put in front of it. If left blank `rtf' will be used as the default path.
+
+ RTF_OUTPUT =
+
+ # If the COMPACT_RTF tag is set to YES Doxygen generates more compact
+ # RTF documents. This may be useful for small projects and may help to
+ # save some trees in general.
+
+ COMPACT_RTF = NO
+
+ # If the RTF_HYPERLINKS tag is set to YES, the RTF that is generated
+ # will contain hyperlink fields. The RTF file will
+ # contain links (just like the HTML output) instead of page references.
+ # This makes the output suitable for online browsing using WORD or other
+ # programs which support those fields.
+ # Note: wordpad (write) and others do not support links.
+
+ RTF_HYPERLINKS = NO
+
+ # Load stylesheet definitions from file. Syntax is similar to doxygen's
+ # config file, i.e. a series of assigments. You only have to provide
+ # replacements, missing definitions are set to their default value.
+
+ RTF_STYLESHEET_FILE =
+
+ # Set optional variables used in the generation of an rtf document.
+ # Syntax is similar to doxygen's config file.
+
+ RTF_EXTENSIONS_FILE =
+
+ #---------------------------------------------------------------------------
+ # configuration options related to the man page output
+ #---------------------------------------------------------------------------
+
+ # If the GENERATE_MAN tag is set to YES (the default) Doxygen will
+ # generate man pages
+
+ GENERATE_MAN = NO
+
+ # The MAN_OUTPUT tag is used to specify where the man pages will be put.
+ # If a relative path is entered the value of OUTPUT_DIRECTORY will be
+ # put in front of it. If left blank `man' will be used as the default path.
+
+ MAN_OUTPUT =
+
+ # The MAN_EXTENSION tag determines the extension that is added to
+ # the generated man pages (default is the subroutine's section .3)
+
+ MAN_EXTENSION =
+
+ # If the MAN_LINKS tag is set to YES and Doxygen generates man output,
+ # then it will generate one additional man file for each entity
+ # documented in the real man page(s). These additional files
+ # only source the real man page, but without them the man command
+ # would be unable to find the correct page. The default is NO.
+
+ MAN_LINKS = NO
+
+ #---------------------------------------------------------------------------
+ # configuration options related to the XML output
+ #---------------------------------------------------------------------------
+
+ # If the GENERATE_XML tag is set to YES Doxygen will
+ # generate an XML file that captures the structure of
+ # the code including all documentation. Note that this
+ # feature is still experimental and incomplete at the
+ # moment.
+
+ GENERATE_XML = NO
+
+ #---------------------------------------------------------------------------
+ # configuration options for the AutoGen Definitions output
+ #---------------------------------------------------------------------------
+
+ # If the GENERATE_AUTOGEN_DEF tag is set to YES Doxygen will
+ # generate an AutoGen Definitions (see autogen.sf.net) file
+ # that captures the structure of the code including all
+ # documentation. Note that this feature is still experimental
+ # and incomplete at the moment.
+
+ GENERATE_AUTOGEN_DEF = NO
+
+ #---------------------------------------------------------------------------
+ # Configuration options related to the preprocessor
+ #---------------------------------------------------------------------------
+
+ # If the ENABLE_PREPROCESSING tag is set to YES (the default) Doxygen will
+ # evaluate all C-preprocessor directives found in the sources and include
+ # files.
+
+ ENABLE_PREPROCESSING = YES
+
+ # If the MACRO_EXPANSION tag is set to YES Doxygen will expand all macro
+ # names in the source code. If set to NO (the default) only conditional
+ # compilation will be performed. Macro expansion can be done in a controlled
+ # way by setting EXPAND_ONLY_PREDEF to YES.
+
+ MACRO_EXPANSION = NO
+
+ # If the EXPAND_ONLY_PREDEF and MACRO_EXPANSION tags are both set to YES
+ # then the macro expansion is limited to the macros specified with the
+ # PREDEFINED and EXPAND_AS_PREDEFINED tags.
+
+ EXPAND_ONLY_PREDEF = NO
+
+ # If the SEARCH_INCLUDES tag is set to YES (the default) the includes files
+ # in the INCLUDE_PATH (see below) will be search if a #include is found.
+
+ SEARCH_INCLUDES = YES
+
+ # The INCLUDE_PATH tag can be used to specify one or more directories that
+ # contain include files that are not input files but should be processed by
+ # the preprocessor.
+
+ INCLUDE_PATH = ../include
+
+ # You can use the INCLUDE_FILE_PATTERNS tag to specify one or more wildcard
+ # patterns (like *.h and *.hpp) to filter out the header-files in the
+ # directories. If left blank, the patterns specified with FILE_PATTERNS will
+ # be used.
+
+ INCLUDE_FILE_PATTERNS =
+
+ # The PREDEFINED tag can be used to specify one or more macro names that
+ # are defined before the preprocessor is started (similar to the -D option of
+ # gcc). The argument of the tag is a list of macros of the form: name
+ # or name=definition (no spaces). If the definition and the = are
+ # omitted =1 is assumed.
+
+ PREDEFINED =
+
+ # If the MACRO_EXPANSION and EXPAND_PREDEF_ONLY tags are set to YES then
+ # this tag can be used to specify a list of macro names that should be expanded.
+ # The macro definition that is found in the sources will be used.
+ # Use the PREDEFINED tag if you want to use a different macro definition.
+
+ EXPAND_AS_DEFINED =
+
+ # If the SKIP_FUNCTION_MACROS tag is set to YES (the default) then
+ # doxygen's preprocessor will remove all function-like macros that are alone
+ # on a line and do not end with a semicolon. Such function macros are typically
+ # used for boiler-plate code, and will confuse the parser if not removed.
+
+ SKIP_FUNCTION_MACROS = YES
+
+ #---------------------------------------------------------------------------
+ # Configuration::addtions related to external references
+ #---------------------------------------------------------------------------
+
+ # The TAGFILES tag can be used to specify one or more tagfiles.
+
+ TAGFILES =
+
+ # When a file name is specified after GENERATE_TAGFILE, doxygen will create
+ # a tag file that is based on the input files it reads.
+
+ GENERATE_TAGFILE =
+
+ # If the ALLEXTERNALS tag is set to YES all external classes will be listed
+ # in the class index. If set to NO only the inherited external classes
+ # will be listed.
+
+ ALLEXTERNALS = YES
+
+ # The PERL_PATH should be the absolute path and name of the perl script
+ # interpreter (i.e. the result of `which perl').
+
+ PERL_PATH =
+
+ #---------------------------------------------------------------------------
+ # Configuration options related to the dot tool
+ #---------------------------------------------------------------------------
+
+ # If the CLASS_DIAGRAMS tag is set to YES (the default) Doxygen will generate a
+ # inheritance diagram (in Html, RTF and LaTeX) for classes with base or super
+ # classes. Setting the tag to NO turns the diagrams off. Note that this option
+ # is superceded by the HAVE_DOT option below. This is only a fallback. It is
+ # recommended to install and use dot, since it yield more powerful graphs.
+
+ CLASS_DIAGRAMS = YES
+
+ # If you set the HAVE_DOT tag to YES then doxygen will assume the dot tool is
+ # available from the path. This tool is part of Graphviz, a graph visualization
+ # toolkit from AT&T and Lucent Bell Labs. The other options in this section
+ # have no effect if this option is set to NO (the default)
+
+ HAVE_DOT = YES
+
+ # If the CLASS_GRAPH and HAVE_DOT tags are set to YES then doxygen
+ # will generate a graph for each documented class showing the direct and
+ # indirect inheritance relations. Setting this tag to YES will force the
+ # the CLASS_DIAGRAMS tag to NO.
+
+ CLASS_GRAPH = YES
+
+ # If the COLLABORATION_GRAPH and HAVE_DOT tags are set to YES then doxygen
+ # will generate a graph for each documented class showing the direct and
+ # indirect implementation dependencies (inheritance, containment, and
+ # class references variables) of the class with other documented classes.
+
+ COLLABORATION_GRAPH = YES
+
+ # If set to YES, the inheritance and collaboration graphs will show the
+ # relations between templates and their instances.
+
+ TEMPLATE_RELATIONS = YES
+
+ # If set to YES, the inheritance and collaboration graphs will hide
+ # inheritance and usage relations if the target is undocumented
+ # or is not a class.
+
+ HIDE_UNDOC_RELATIONS = NO
+
+ # If the ENABLE_PREPROCESSING, SEARCH_INCLUDES, INCLUDE_GRAPH, and HAVE_DOT
+ # tags are set to YES then doxygen will generate a graph for each documented
+ # file showing the direct and indirect include dependencies of the file with
+ # other documented files.
+
+ INCLUDE_GRAPH = YES
+
+ # If the ENABLE_PREPROCESSING, SEARCH_INCLUDES, INCLUDED_BY_GRAPH, and
+ # HAVE_DOT tags are set to YES then doxygen will generate a graph for each
+ # documented header file showing the documented files that directly or
+ # indirectly include this file.
+
+ INCLUDED_BY_GRAPH = YES
+
+ # If the GRAPHICAL_HIERARCHY and HAVE_DOT tags are set to YES then doxygen
+ # will graphical hierarchy of all classes instead of a textual one.
+
+ GRAPHICAL_HIERARCHY = YES
+
+ # The tag DOT_PATH can be used to specify the path where the dot tool can be
+ # found. If left blank, it is assumed the dot tool can be found on the path.
+
+ DOT_PATH =
+
+ # The DOTFILE_DIRS tag can be used to specify one or more directories that
+ # contain dot files that are included in the documentation (see the
+ # \dotfile command).
+
+ DOTFILE_DIRS =
+
+ # The MAX_DOT_GRAPH_WIDTH tag can be used to set the maximum allowed width
+ # (in pixels) of the graphs generated by dot. If a graph becomes larger than
+ # this value, doxygen will try to truncate the graph, so that it fits within
+ # the specified constraint. Beware that most browsers cannot cope with very
+ # large images.
+
+ MAX_DOT_GRAPH_WIDTH = 1024
+
+ # The MAX_DOT_GRAPH_HEIGHT tag can be used to set the maximum allows height
+ # (in pixels) of the graphs generated by dot. If a graph becomes larger than
+ # this value, doxygen will try to truncate the graph, so that it fits within
+ # the specified constraint. Beware that most browsers cannot cope with very
+ # large images.
+
+ MAX_DOT_GRAPH_HEIGHT = 1024
+
+ # If the GENERATE_LEGEND tag is set to YES (the default) Doxygen will
+ # generate a legend page explaining the meaning of the various boxes and
+ # arrows in the dot generated graphs.
+
+ GENERATE_LEGEND = YES
+
+ # If the DOT_CLEANUP tag is set to YES (the default) Doxygen will
+ # remove the intermedate dot files that are used to generate
+ # the various graphs.
+
+ DOT_CLEANUP = YES
+
+ #---------------------------------------------------------------------------
+ # Configuration::addtions related to the search engine
+ #---------------------------------------------------------------------------
+
+ # The SEARCHENGINE tag specifies whether or not a search engine should be
+ # used. If set to NO the values of all tags below this one will be ignored.
+
+ SEARCHENGINE = NO
+
+ # The CGI_NAME tag should be the name of the CGI script that
+ # starts the search engine (doxysearch) with the correct parameters.
+ # A script with this name will be generated by doxygen.
+
+ CGI_NAME =
+
+ # The CGI_URL tag should be the absolute URL to the directory where the
+ # cgi binaries are located. See the documentation of your http daemon for
+ # details.
+
+ CGI_URL =
+
+ # The DOC_URL tag should be the absolute URL to the directory where the
+ # documentation is located. If left blank the absolute path to the
+ # documentation, with file:// prepended to it, will be used.
+
+ DOC_URL =
+
+ # The DOC_ABSPATH tag should be the absolute path to the directory where the
+ # documentation is located. If left blank the directory on the local machine
+ # will be used.
+
+ DOC_ABSPATH =
+
+ # The BIN_ABSPATH tag must point to the directory where the doxysearch binary
+ # is installed.
+
+ BIN_ABSPATH =
+
+ # The EXT_DOC_PATHS tag can be used to specify one or more paths to
+ # documentation generated for other projects. This allows doxysearch to search
+ # the documentation for these projects as well.
+
+ EXT_DOC_PATHS =
Index: llvm-www/releases/1.2/docs/doxygen.css
diff -c /dev/null llvm-www/releases/1.2/docs/doxygen.css:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/doxygen.css Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,84 ----
+ BODY { background: white; color: black; font-family: Verdana,Arial,sans-serif; }
+ H1 { text-align: center; }
+ H2 { text-align: center; }
+ H3 { text-align: center; }
+ CAPTION { font-weight: bold }
+ A.qindex {}
+ A.qindexRef {}
+ A.el { text-decoration: none; font-weight: bold }
+ A.elRef { font-weight: bold }
+ A.code { text-decoration: none; font-weight: normal; color: #4444ee }
+ A.codeRef { font-weight: normal; color: #4444ee }
+ A:link {
+ cursor: pointer;
+ text-decoration: none;
+ font-weight: bolder;
+ }
+ A:visited {
+ cursor: pointer;
+ text-decoration: underline;
+ font-weight: bolder;
+ }
+ A:hover {
+ cursor: pointer;
+ text-decoration: underline;
+ font-weight: bolder;
+ }
+ A:active {
+ cursor: pointer;
+ text-decoration: underline;
+ font-weight: bolder;
+ font-style: italic;
+ }
+ DL.el { margin-left: -1cm }
+ DIV.fragment { width: 100%; border: none; background-color: #eeeeee }
+ DIV.ah { background-color: black; font-weight: bold; color: #ffffff; margin-bottom: 3px; margin-top: 3px }
+ TD.md { background-color: #f2f2ff; font-weight: bold; }
+ TD.mdname1 { background-color: #f2f2ff; font-weight: bold; color: #602020; }
+ TD.mdname { background-color: #f2f2ff; font-weight: bold; color: #602020; width: 600px; }
+ DIV.groupHeader { margin-left: 16px; margin-top: 12px; margin-bottom: 6px; font-weight: bold }
+ DIV.groupText { margin-left: 16px; font-style: italic; font-size: smaller }
+ TD.indexkey {
+ background-color: #eeeeff;
+ font-weight: bold;
+ padding-right : 10px;
+ padding-top : 2px;
+ padding-left : 10px;
+ padding-bottom : 2px;
+ margin-left : 0px;
+ margin-right : 0px;
+ margin-top : 2px;
+ margin-bottom : 2px
+ }
+ TD.indexvalue {
+ background-color: #eeeeff;
+ font-style: italic;
+ padding-right : 10px;
+ padding-top : 2px;
+ padding-left : 10px;
+ padding-bottom : 2px;
+ margin-left : 0px;
+ margin-right : 0px;
+ margin-top : 2px;
+ margin-bottom : 2px
+ }
+ span.keyword { color: #008000 }
+ span.keywordtype { color: #604020 }
+ span.keywordflow { color: #e08000 }
+ span.comment { color: #800000 }
+ span.preprocessor { color: #806020 }
+ span.stringliteral { color: #002080 }
+ span.charliteral { color: #008080 }
+
+ .footer {
+ font-size: 80%;
+ font-weight: bold;
+ text-align: center;
+ vertical-align: middle;
+ }
+ .title {
+ font-size: 105%
+ font-weight: bold;
+ text-decoration: underline;
+ text-align: center;
+ }
Index: llvm-www/releases/1.2/docs/doxygen.footer
diff -c /dev/null llvm-www/releases/1.2/docs/doxygen.footer:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/doxygen.footer Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,9 ----
+ <hr>
+ <p class="footer">
+ Generated on $datetime for $projectname version $projectnumber by
+ <a href="http://www.doxygen.org/index.html">doxygen $doxygenversion</a><br/>
+ Copyright © 2003, University of Illinois at Urbana-Champaign. All Rights Reserved.<br/>
+ <a href="/index.php" onmouseover="window.status='Go To LLVM Home Page';return true;" title="LLVM Home Page">Home Page</a>
+ <a href="http://www.doxygen.org/index.html" onmouseover="window.status='Go To Doxygen Home Page';return true;" title="Doxygen Home Page">
+ <img src="doxygen.png" alt="Doxygen Logo" style="border:none;"/></a>
+ </p></body></html>
Index: llvm-www/releases/1.2/docs/doxygen.header
diff -c /dev/null llvm-www/releases/1.2/docs/doxygen.header:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/doxygen.header Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,9 ----
+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
+ <html><head>
+ <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1"/>
+ <meta name="keywords" content="LLVM,Low Level Virtual Machine,C++,doxygen,API,documentation"/>
+ <meta name="description" content="C++ source code API documentation for the Low Level Virtual Machine (LLVM)."/>
+ <title>LLVM: $title</title>
+ <link href="doxygen.css" rel="stylesheet" type="text/css"/>
+ </head><body>
+ <p class="title">LLVM API Documentation</p>
Index: llvm-www/releases/1.2/docs/doxygen.intro
diff -c /dev/null llvm-www/releases/1.2/docs/doxygen.intro:1.1
*** /dev/null Fri Mar 19 11:38:22 2004
--- llvm-www/releases/1.2/docs/doxygen.intro Fri Mar 19 11:38:11 2004
***************
*** 0 ****
--- 1,25 ----
+ ////////////////////////////////////////////////////////////////////////////////
+ /// @file doxygen.intro
+ /// @author Reid Spencer <rspencer at x10sys.com>
+ /// @date 2003/12/30
+ /// @brief LLVM API documentation introduction.
+ ////////////////////////////////////////////////////////////////////////////////
+ ///
+ /// @mainpage LLVM:Low Level Virtual Machine
+ ///
+ /// @section main_intro Introduction
+ /// Welcome to the Low Level Virtual Machine (LLVM)
+ ///
+ /// This documentation describes the @b internal software that makes
+ /// up LLVM, not the @b external use of LLVM. There are no instructions
+ /// here on how to use LLVM, only the APIs that make up the software. For usage
+ /// instructions, please see the programmer's guide or reference manual.
+ ///
+ /// @section main_caveat Caveat
+ /// This documentation is generated directly from the source code with doxygen.
+ /// Since LLVM is constantly under active development, what you're about to
+ /// read is out of date! However, it may still be useful since certain portions of
+ /// LLVM are very stable.
+ ///
+ /// @section main_changelog Change Log
+ /// - Original content written 12/30/2003 by Reid Spencer
Index: llvm-www/releases/1.2/docs/index.html
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*** 0 ****
--- 1,293 ----
+ <html>
+ <title>
+ The LLVM Compiler Infrastructure
+ </title>
+
+ <body>
+
+ <center>
+ <h1>
+ The LLVM Compiler Infrastructure
+ <br>
+ <a href="http://llvm.cs.uiuc.edu">http://llvm.cs.uiuc.edu</a>
+ </h1>
+ </center>
+
+ <hr>
+
+ <h2>
+ Welcome to LLVM!
+ </h2>
+ This file is intended to do four things:
+ <ol>
+ <li>
+ help you get started using LLVM;
+ </li>
+
+ <li>
+ tell you how to get questions about LLVM answered;
+ </li>
+
+ <li>
+ tell you where to find documentation for different kinds of questions; and
+ </li>
+
+ <li>
+ tell you about three LLVM-related mailing lists.
+ </li>
+ </ol>
+
+
+ <hr>
+
+ <h2>
+ Getting Started with LLVM
+ </h2>
+
+ <dl compact>
+ <dt>
+ For license information:
+ <dd>
+ <a href="http://llvm.cs.uiuc.edu/cvsweb/cvsweb.cgi/llvm/LICENSE.TXT?rev=HEAD&content-type=text/x-cvsweb-markup">llvm/LICENSE.TXT</a>
+ <p>
+
+ <dt>
+ Installing and compiling LLVM:
+ <dd>
+ <a href="GettingStarted.html">llvm/docs/GettingStarted.html</a>
+ <p>
+
+ <dt>
+ Learn about features and limitations of this release:
+ <dd>
+ <a href="ReleaseNotes.html">llvm/docs/ReleaseNotes.html</a>
+ <p>
+
+ <dt>
+ Learn how to write a pass within the LLVM system:
+ <dd>
+ <a href="WritingAnLLVMPass.html">llvm/docs/WritingAnLLVMPass.html </a>
+ <p>
+
+ <dt>
+ Learn how to start a new development project using LLVM, where your
+ new source code can live anywhere (outside or inside the LLVM tree),
+ while using LLVM header files and libraries:
+ <dd>
+ <a href="Projects.html">llvm/docs/Projects.html</a>
+ </dl>
+
+ <hr>
+
+ <h2>
+ Getting Help with LLVM
+ </h2>
+
+ <ol>
+ <li>
+ If you have questions or development problems not answered in the
+ documentation, send e-mail to llvmdev at cs.uiuc.edu. This mailing list is
+ monitored by all the people in the LLVM group at Illinois, and you
+ should expect prompt first responses.
+ </li>
+
+ <li>
+ To report a bug, submit a bug report as described in the document:
+ <a href="http://llvm.cs.uiuc.edu/docs/HowToSubmitABug.html">
+ http://llvm.cs.uiuc.edu/docs/HowToSubmitABug.html</a>
+ </li>
+
+ <li>
+ We now use Bugzilla to track bugs, so you can check the status of
+ previous bugs at:
+ <a href="http://llvm.cs.uiuc.edu/bugs/query.cgi">
+ http://llvm.cs.uiuc.edu/bugs/query.cgi </a>
+ </li>
+ </ol>
+
+ <hr>
+
+ <h2>
+ LLVM Documentation
+ </h2>
+
+ All the documents mentioned below except the design overview tech report
+ are included as part of the LLVM release (in llvm/docs/*):
+
+ <h3>
+ LLVM Design Overview:
+ </h3>
+
+ <dl compact>
+ <dt>
+ LLVM: A Compilation Framework for Lifelong Program Analysis
+ & Transformation
+ <dd>
+ <a href="http://llvm.cs.uiuc.edu/pubs/2004-01-30-CGO-LLVM.html">
+ http://llvm.cs.uiuc.edu/pubs/2004-01-30-CGO-LLVM.html </a>
+
+ </dl>
+
+ <h3>
+ LLVM User Guides:
+ </h3>
+
+ <dl compact>
+ <dt>
+ Download and Installation Instructions:
+ <dd>
+ <a href="GettingStarted.html"> llvm/docs/GettingStarted.html</a>
+ <p>
+
+ <dt>
+ LLVM Command Guide:
+ <dd>
+ <a href="CommandGuide/index.html">
+ llvm/docs/CommandGuide/index.html</a>
+ <p>
+
+ <dt>
+ LLVM Assembly Language:
+ <dd>
+ <a href="LangRef.html"> llvm/docs/LangRef.html</a>
+ <p>
+
+ <dt>
+ LLVM Test Suite Guide:
+ <dd>
+ <a href="TestingGuide.html"> llvm/docs/TestingGuide.html</a>
+ <p>
+ </dl>
+
+ <h3>
+ LLVM Programming Documentation:
+ </h3>
+
+ <dl compact>
+ <dt>
+ LLVM Programmers Manual:
+ <dd>
+ <a href="ProgrammersManual.html"> llvm/docs/ProgrammersManual.html</a>
+ <p>
+
+ <dt>
+ Writing an LLVM Pass:
+ <dd>
+ <a href="WritingAnLLVMPass.html"> llvm/docs/WritingAnLLVMPass.html</a>
+ <p>
+
+ <dt>
+ Alias Analysis in LLVM:
+ <dd>
+ <a href="AliasAnalysis.html"> llvm/docs/AliasAnalysis.html</a>
+ <p>
+
+ <dt>
+ Source Level Debugging with LLVM:
+ <dd>
+ <a href="SourceLevelDebugging.html"> llvm/docs/SourceLevelDebugging.html</a>
+ <p>
+
+
+ <dt>
+ TableGen Fundamentals:
+ <dd>
+ <a href="TableGenFundamentals.html"> llvm/docs/TableGenFundamentals.html</a>
+ <p>
+
+
+ <dt>
+ The Stacker Cronicles
+ <dd>
+ <a href="Stacker.html">The Stacker Cronicles</a>
+ - This document describes both the Stacker language and
+ LLVM frontend, but also some details about LLVM useful for
+ those writing front-ends.<p>
+
+
+ <dt>
+ Command Line Library:
+ <dd>
+ <a href="CommandLine.html"> llvm/docs/CommandLine.html</a>
+ <p>
+
+ <dt>
+ Coding Standards:
+ <dd>
+ <a href="CodingStandards.html"> llvm/docs/CodingStandards.html</a>
+ <p>
+ </dl>
+
+ <h3>
+ Other LLVM Resources:
+ </h3>
+
+ <dl compact>
+ <dt>
+ Building the LLVM C/C++ front-end:
+ <dd>
+ <a href="CFEBuildInstrs.html">llvm/docs/CFEBuildInstrs.html</a>
+ <p>
+ <dt>
+ Submitting a Bug:
+ <dd>
+ <a href="http://llvm.cs.uiuc.edu/docs/HowToSubmitABug.html">
+ http://llvm.cs.uiuc.edu/docs/HowToSubmitABug.html</a>
+ <p>
+
+ <dt>
+ Open Projects:
+ <dd>
+ <a href="OpenProjects.html"> llvm/docs/OpenProjects.html</a>
+ <p>
+
+ <dt>
+ Creating a new LLVM Project:
+ <dd>
+ <a href="Projects.html"> llvm/docs/Projects.html</a>
+ <p>
+ </dl>
+
+ <hr>
+
+ <h2>
+ Mailing Lists
+ </h2>
+ There are three mailing lists for providing LLVM users with information:
+
+ <ol>
+ <li> LLVM Announcements List:<br>
+ <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvm-announce">
+ http://mail.cs.uiuc.edu/mailman/listinfo/llvm-announce</a>
+
+ <p>
+ This is a low volume list that provides important announcements regarding
+ LLVM. It is primarily intended to announce new releases, major updates to
+ the software, etc. This list is highly recommended for anyone that uses
+ LLVM.
+ </p>
+
+ <li> LLVM Developers List:<br>
+ <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">
+ http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev</a>
+
+ <p>
+ This list is for people who want to be included in technical discussions
+ of LLVM. People post to this list when they have questions about writing
+ code for or using the LLVM tools. It is relatively low volume.
+ </p>
+
+ <li> LLVM Commits List<br>
+ <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvm-commits">
+ http://mail.cs.uiuc.edu/mailman/listinfo/llvm-commits</a>
+
+ <p>
+ This list contains all commit messages that are made when LLVM developers
+ commit code changes to the CVS archive. It is useful for those who want to
+ stay on the bleeding edge of LLVM development. This list is very high
+ volume.
+ </p>
+ </ol>
+ </body>
+ </html>
+
Index: llvm-www/releases/1.2/docs/llvm.css
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*** 0 ****
--- 1,52 ----
+ /*
+ * LLVM website style sheet
+ */
+
+ /* Common styles */
+ .body { color: black; background: white; margin: 0 0 0 0 }
+
+ /* No borders on image links */
+ a:link img, a:visited img {border-style: none}
+
+ address img { float: right; width: 88px; height: 31px; }
+ address { clear: right; }
+
+ /*
+ * Documentation
+ */
+ /* Common for title and header */
+ .doc_title, .doc_section, .doc_subsection {
+ color: #ffffff; background: #330077;
+ font-family: "Georgia,Palatino,Times,Roman"; font-weight: bold;
+ padding-left: 8pt;
+ padding-top: 1px;
+ padding-bottom: 2px
+ }
+
+ .doc_title { text-align: left; font-size: 25pt }
+ .doc_section { text-align: center; font-size: 22pt; }
+ .doc_subsection { background: #441188; width: 50%;
+ text-align: left; font-size: 12pt; padding: 4pt 4pt 4pt 4pt;
+ margin: 1.5em 0.5em 1.5em 0.5em }
+
+ /* In the future, the 2nd level subsection style may want to become this:
+ .doc_subsubsection { margin: 1.5em 0.5em 1.5 0.5em;
+ font-weight: bold; font-style: oblique;
+ border-bottom: 2px dotted #999999 }
+ */
+
+ /* However, to be consistent with the rest of current documentation which is not
+ all yet using stylesheets, we try to emulate the former layout. */
+ .doc_subsubsection { margin: 1.5em 0.5em 1.5em 0.5em;
+ font-weight: bold;
+ border-top: 2px solid #cecece }
+
+ .doc_text { text-align: left; padding-left: 20pt }
+
+ .doc_footer { text-align: left; padding: 0 0 0 0 }
+
+ .doc_red { color: red }
+
+ .doc_table { text-align: center; width: 90%;
+ padding: 1px 1px 1px 1px; border: 1px; }
+
Index: llvm-www/releases/1.2/docs/venusflytrap.jpg
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