[llvm-commits] [llvm] r50861 - in /llvm/trunk: docs/Passes.html lib/Transforms/IPO/StripDeadPrototypes.cpp lib/Transforms/IPO/StructRetPromotion.cpp lib/Transforms/Scalar/CodeGenPrepare.cpp lib/Transforms/Scalar/JumpThreading.cpp lib/Transforms/Scalar/LoopDeletion.cpp

Tanya Lattner lattner at apple.com
Thu May 8 11:11:45 PDT 2008


For the changes to the JumpThreading Class, I don't think doxygen  
will pick up the comments at the top of the file (but correct me if I  
am wrong).

I think its better to leave them at the top of the class (in doxygen  
style) so it shows up in doxygen.

-Tanya

On May 8, 2008, at 10:46 AM, Gordon Henriksen wrote:

> Author: gordon
> Date: Thu May  8 12:46:35 2008
> New Revision: 50861
>
> URL: http://llvm.org/viewvc/llvm-project?rev=50861&view=rev
> Log:
> Improve pass documentation and comments.
>
> Patch by Matthijs Kooijman!
>
> Modified:
>     llvm/trunk/docs/Passes.html
>     llvm/trunk/lib/Transforms/IPO/StripDeadPrototypes.cpp
>     llvm/trunk/lib/Transforms/IPO/StructRetPromotion.cpp
>     llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
>     llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
>     llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp
>
> Modified: llvm/trunk/docs/Passes.html
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ 
> Passes.html?rev=50861&r1=50860&r2=50861&view=diff
>
> ====================================================================== 
> ========
> --- llvm/trunk/docs/Passes.html (original)
> +++ llvm/trunk/docs/Passes.html Thu May  8 12:46:35 2008
> @@ -116,7 +116,7 @@
>  <tr><td><a href="#argpromotion">-argpromotion</a></td><td>Promote  
> 'by reference' arguments to scalars</td></tr>
>  <tr><td><a href="#block-placement">-block-placement</a></ 
> td><td>Profile Guided Basic Block Placement</td></tr>
>  <tr><td><a href="#break-crit-edges">-break-crit-edges</a></ 
> td><td>Break critical edges in CFG</td></tr>
> -<tr><td><a href="#cee">-cee</a></td><td>Correlated Expression  
> Elimination</td></tr>
> +<tr><td><a href="#codegenprepare">-codegenprepare</a></ 
> td><td>Prepare a function for code generation </td></tr>
>  <tr><td><a href="#condprop">-condprop</a></td><td>Conditional  
> Propagation</td></tr>
>  <tr><td><a href="#constmerge">-constmerge</a></td><td>Merge  
> Duplicate Global Constants</td></tr>
>  <tr><td><a href="#constprop">-constprop</a></td><td>Simple  
> constant propagation</td></tr>
> @@ -142,8 +142,10 @@
>  <tr><td><a href="#internalize">-internalize</a></ 
> td><td>Internalize Global Symbols</td></tr>
>  <tr><td><a href="#ipconstprop">-ipconstprop</a></ 
> td><td>Interprocedural constant propagation</td></tr>
>  <tr><td><a href="#ipsccp">-ipsccp</a></td><td>Interprocedural  
> Sparse Conditional Constant Propagation</td></tr>
> +<tr><td><a href="#jump-threading">-jump-threading</a></ 
> td><td>Thread control through conditional blocks </td></tr>
>  <tr><td><a href="#lcssa">-lcssa</a></td><td>Loop-Closed SSA Form  
> Pass</td></tr>
>  <tr><td><a href="#licm">-licm</a></td><td>Loop Invariant Code  
> Motion</td></tr>
> +<tr><td><a href="#loop-deletion">-loop-deletion</a></td><td>Dead  
> Loop Deletion Pass </td></tr>
>  <tr><td><a href="#loop-extract">-loop-extract</a></td><td>Extract  
> loops into new functions</td></tr>
>  <tr><td><a href="#loop-extract-single">-loop-extract-single</a></ 
> td><td>Extract at most one loop into a new function</td></tr>
>  <tr><td><a href="#loop-index-split">-loop-index-split</a></ 
> td><td>Index Split Loops</td></tr>
> @@ -152,14 +154,12 @@
>  <tr><td><a href="#loop-unroll">-loop-unroll</a></td><td>Unroll  
> loops</td></tr>
>  <tr><td><a href="#loop-unswitch">-loop-unswitch</a></ 
> td><td>Unswitch loops</td></tr>
>  <tr><td><a href="#loopsimplify">-loopsimplify</a></ 
> td><td>Canonicalize natural loops</td></tr>
> -<tr><td><a href="#lower-packed">-lower-packed</a></td><td>lowers  
> packed operations to operations on smaller packed datatypes</td></tr>
>  <tr><td><a href="#lowerallocs">-lowerallocs</a></td><td>Lower  
> allocations from instructions to calls</td></tr>
> -<tr><td><a href="#lowergc">-lowergc</a></td><td>Lower GC  
> intrinsics, for GCless code generators</td></tr>
>  <tr><td><a href="#lowerinvoke">-lowerinvoke</a></td><td>Lower  
> invoke and unwind, for unwindless code generators</td></tr>
> -<tr><td><a href="#lowerselect">-lowerselect</a></td><td>Lower  
> select instructions to branches</td></tr>
>  <tr><td><a href="#lowersetjmp">-lowersetjmp</a></td><td>Lower Set  
> Jump</td></tr>
>  <tr><td><a href="#lowerswitch">-lowerswitch</a></td><td>Lower  
> SwitchInst's to branches</td></tr>
>  <tr><td><a href="#mem2reg">-mem2reg</a></td><td>Promote Memory to  
> Register</td></tr>
> +<tr><td><a href="#memcpyopt">-memcpyopt</a></td><td>Optimize use  
> of memcpy and friends</td></tr>
>  <tr><td><a href="#mergereturn">-mergereturn</a></td><td>Unify  
> function exit nodes</td></tr>
>  <tr><td><a href="#predsimplify">-predsimplify</a></ 
> td><td>Predicate Simplifier</td></tr>
>  <tr><td><a href="#prune-eh">-prune-eh</a></td><td>Remove unused  
> exception handling info</td></tr>
> @@ -171,6 +171,8 @@
>  <tr><td><a href="#simplify-libcalls">-simplify-libcalls</a></ 
> td><td>Simplify well-known library calls</td></tr>
>  <tr><td><a href="#simplifycfg">-simplifycfg</a></td><td>Simplify  
> the CFG</td></tr>
>  <tr><td><a href="#strip">-strip</a></td><td>Strip all symbols from  
> a module</td></tr>
> +<tr><td><a href="#strip-dead-prototypes">-strip-dead-prototypes</ 
> a></td><td>Remove unused function declarations</td></tr>
> +<tr><td><a href="#sretpromotion">-sretpromotion</a></ 
> td><td>Promote sret arguments</td></tr>
>  <tr><td><a href="#tailcallelim">-tailcallelim</a></td><td>Tail  
> Call Elimination</td></tr>
>  <tr><td><a href="#tailduplicate">-tailduplicate</a></td><td>Tail  
> Duplication</td></tr>
>
> @@ -739,27 +741,12 @@
>
>   
> <!-------------------------------------------------------------------- 
> ------ -->
>  <div class="doc_subsection">
> -  <a name="cee">Correlated Expression Elimination</a>
> +  <a name="codegenprepare">Prepare a function for code generation</a>
>  </div>
>  <div class="doc_text">
> -  <p>Correlated Expression Elimination propagates information from  
> conditional
> -  branches to blocks dominated by destinations of the branch.  It  
> propagates
> -  information from the condition check itself into the body of the  
> branch,
> -  allowing transformations like these for example:</p>
> -
> -<blockquote><pre>
> -if (i == 7)
> -  ... 4*i;  // constant propagation
> -
> -M = i+1; N = j+1;
> -if (i == j)
> -  X = M-N;  // = M-M == 0;
> -</pre></blockquote>
> -
> -   <p>This is called Correlated Expression Elimination because we  
> eliminate or
> -   simplify expressions that are correlated with the direction of  
> a branch. In
> -   this way we use static information to give us some information  
> about the
> -   dynamic value of a variable.</p>
> +  This pass munges the code in the input function to better  
> prepare it for
> +  SelectionDAG-based code generation. This works around  
> limitations in it's
> +  basic-block-at-a-time approach. It should eventually be removed.
>  </div>
>
>   
> <!-------------------------------------------------------------------- 
> ------ -->
> @@ -1183,6 +1170,35 @@
>
>   
> <!-------------------------------------------------------------------- 
> ------ -->
>  <div class="doc_subsection">
> +  <a name="jump-threading">Thread control through conditional  
> blocks</a>
> +</div>
> +<div class="doc_text">
> +  <p>
> +  Jump threading tries to find distinct threads of control flow  
> running through
> +  a basic block. This pass looks at blocks that have multiple  
> predecessors and
> +  multiple successors.  If one or more of the predecessors of the  
> block can be
> +  proven to always cause a jump to one of the successors, we  
> forward the edge
> +  from the predecessor to the successor by duplicating the  
> contents of this
> +  block.
> +  </p>
> +  <p>
> +  An example of when this can occur is code like this:
> +  </p>
> +
> +  <pre
> +>if () { ...
> +  X = 4;
> +}
> +if (X < 3) {</pre>
> +
> +  <p>
> +  In this case, the unconditional branch at the end of the first  
> if can be
> +  revectored to the false side of the second if.
> +  </p>
> +</div>
> +
> +<!------------------------------------------------------------------- 
> ------- -->
> +<div class="doc_subsection">
>    <a name="lcssa">Loop-Closed SSA Form Pass</a>
>  </div>
>  <div class="doc_text">
> @@ -1246,6 +1262,18 @@
>          variable.</li>
>    </ul>
>  </div>
> +<!------------------------------------------------------------------- 
> ------- -->
> +<div class="doc_subsection">
> +  <a name="loop-deletion">Dead Loop Deletion Pass</a>
> +</div>
> +<div class="doc_text">
> +  <p>
> +  This file implements the Dead Loop Deletion Pass.  This pass is  
> responsible
> +  for eliminating loops with non-infinite computable trip counts  
> that have no
> +  side effects or volatile instructions, and do not contribute to the
> +  computation of the function's return value.
> +  </p>
> +</div>
>
>   
> <!-------------------------------------------------------------------- 
> ------ -->
>  <div class="doc_subsection">
> @@ -1390,17 +1418,6 @@
>
>   
> <!-------------------------------------------------------------------- 
> ------ -->
>  <div class="doc_subsection">
> -  <a name="lower-packed">lowers packed operations to operations on  
> smaller packed datatypes</a>
> -</div>
> -<div class="doc_text">
> -  <p>
> -  Lowers operations on vector datatypes into operations on more  
> primitive vector
> -  datatypes, and finally to scalar operations.
> -  </p>
> -</div>
> -
> - 
> <!-------------------------------------------------------------------- 
> ------ -->
> -<div class="doc_subsection">
>    <a name="lowerallocs">Lower allocations from instructions to  
> calls</a>
>  </div>
>  <div class="doc_text">
> @@ -1417,29 +1434,6 @@
>
>   
> <!-------------------------------------------------------------------- 
> ------ -->
>  <div class="doc_subsection">
> -  <a name="lowergc">Lower GC intrinsics, for GCless code  
> generators</a>
> -</div>
> -<div class="doc_text">
> -  <p>
> -  This file implements lowering for the <tt>llvm.gc*</tt>  
> intrinsics for targets
> -  that do not natively support them (which includes the C  
> backend).  Note that
> -  the code generated is not as efficient as it would be for  
> targets that
> -  natively support the GC intrinsics, but it is useful for getting  
> new targets
> -  up-and-running quickly.
> -  </p>
> -
> -  <p>
> -  This pass implements the code transformation described in this  
> paper:
> -  </p>
> -
> -  <blockquote><p>
> -    "Accurate Garbage Collection in an Uncooperative Environment"
> -    Fergus Henderson, ISMM, 2002
> -  </p></blockquote>
> -</div>
> -
> - 
> <!-------------------------------------------------------------------- 
> ------ -->
> -<div class="doc_subsection">
>    <a name="lowerinvoke">Lower invoke and unwind, for unwindless  
> code generators</a>
>  </div>
>  <div class="doc_text">
> @@ -1481,25 +1475,6 @@
>
>   
> <!-------------------------------------------------------------------- 
> ------ -->
>  <div class="doc_subsection">
> -  <a name="lowerselect">Lower select instructions to branches</a>
> -</div>
> -<div class="doc_text">
> -  <p>
> -  Lowers select instructions into conditional branches for targets  
> that do not
> -  have conditional moves or that have not implemented the select  
> instruction
> -  yet.
> -  </p>
> -
> -  <p>
> -  Note that this pass could be improved.  In particular it turns  
> every select
> -  instruction into a new conditional branch, even though some  
> common cases have
> -  select instructions on the same predicate next to each other.   
> It would be
> -  better to use the same branch for the whole group of selects.
> -  </p>
> -</div>
> -
> - 
> <!-------------------------------------------------------------------- 
> ------ -->
> -<div class="doc_subsection">
>    <a name="lowersetjmp">Lower Set Jump</a>
>  </div>
>  <div class="doc_text">
> @@ -1557,6 +1532,17 @@
>
>   
> <!-------------------------------------------------------------------- 
> ------ -->
>  <div class="doc_subsection">
> +  <a name="memcpyopt">Optimize use of memcpy and friend</a>
> +</div>
> +<div class="doc_text">
> +  <p>
> +  This pass performs various transformations related to  
> eliminating memcpy
> +  calls, or transforming sets of stores into memset's.
> +  </p>
> +</div>
> +
> +<!------------------------------------------------------------------- 
> ------- -->
> +<div class="doc_subsection">
>    <a name="mergereturn">Unify function exit nodes</a>
>  </div>
>  <div class="doc_text">
> @@ -1753,6 +1739,42 @@
>
>   
> <!-------------------------------------------------------------------- 
> ------ -->
>  <div class="doc_subsection">
> +  <a name="strip-dead-prototypes">Remove unused function  
> declarations</a>
> +</div>
> +<div class="doc_text">
> +  <p>
> +  This pass loops over all of the functions in the input module,  
> looking for
> +  dead declarations and removes them. Dead declarations are  
> declarations of
> +  functions for which no implementation is available (i.e.,  
> declarations for
> +  unused library functions).
> +  </p>
> +</div>
> +
> +<!------------------------------------------------------------------- 
> ------- -->
> +<div class="doc_subsection">
> +  <a name="sretpromotion">Promote sret arguments</a>
> +</div>
> +<div class="doc_text">
> +  <p>
> +  This pass finds functions that return a struct (using a pointer  
> to the struct
> +  as the first argument of the function, marked with the  
> '<tt>sret</tt>' attribute) and
> +  replaces them with a new function that simply returns each of  
> the elements of
> +  that struct (using multiple return values).
> +  </p>
> +
> +  <p>
> +  This pass works under a number of conditions:
> +  </p>
> +
> +  <ul>
> +  <li>The returned struct must not contain other structs</li>
> +  <li>The returned struct must only be used to load values from</li>
> +  <li>The placeholder struct passed in is the result of an  
> <tt>alloca</tt></li>
> +  </ul>
> +</div>
> +
> +<!------------------------------------------------------------------- 
> ------- -->
> +<div class="doc_subsection">
>    <a name="tailcallelim">Tail Call Elimination</a>
>  </div>
>  <div class="doc_text">
>
> Modified: llvm/trunk/lib/Transforms/IPO/StripDeadPrototypes.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ 
> IPO/StripDeadPrototypes.cpp?rev=50861&r1=50860&r2=50861&view=diff
>
> ====================================================================== 
> ========
> --- llvm/trunk/lib/Transforms/IPO/StripDeadPrototypes.cpp (original)
> +++ llvm/trunk/lib/Transforms/IPO/StripDeadPrototypes.cpp Thu May   
> 8 12:46:35 2008
> @@ -1,4 +1,4 @@
> -//===-- StripDeadPrototypes.cpp - Removed unused function  
> declarations ----===//
> +//===-- StripDeadPrototypes.cpp - Remove unused function  
> declarations ----===//
>  //
>  //                     The LLVM Compiler Infrastructure
>  //
> @@ -8,7 +8,9 @@
>  // 
> ===------------------------------------------------------------------- 
> ---===//
>  //
>  // This pass loops over all of the functions in the input module,  
> looking for
> -// dead declarations and removes them.
> +// dead declarations and removes them. Dead declarations are  
> declarations of
> +// functions for which no implementation is available (i.e.,  
> declarations for
> +// unused library functions).
>  //
>  // 
> ===------------------------------------------------------------------- 
> ---===//
>
>
> Modified: llvm/trunk/lib/Transforms/IPO/StructRetPromotion.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ 
> IPO/StructRetPromotion.cpp?rev=50861&r1=50860&r2=50861&view=diff
>
> ====================================================================== 
> ========
> --- llvm/trunk/lib/Transforms/IPO/StructRetPromotion.cpp (original)
> +++ llvm/trunk/lib/Transforms/IPO/StructRetPromotion.cpp Thu May  8  
> 12:46:35 2008
> @@ -1,4 +1,4 @@
> -//===-- StructRetPromotion.cpp - Promote sret arguments  
> -000000------------===//
> +//===-- StructRetPromotion.cpp - Promote sret arguments  
> ------------------===//
>  //
>  //                     The LLVM Compiler Infrastructure
>  //
> @@ -7,7 +7,16 @@
>  //
>  // 
> ===------------------------------------------------------------------- 
> ---===//
>  //
> -// TODO : Describe this pass.
> +// This pass finds functions that return a struct (using a pointer  
> to the struct
> +// as the first argument of the function, marked with the 'sret'  
> attribute) and
> +// replaces them with a new function that simply returns each of  
> the elements of
> +// that struct (using multiple return values).
> +//
> +// This pass works under a number of conditions:
> +//  1. The returned struct must not contain other structs
> +//  2. The returned struct must only be used to load values from
> +//  3. The placeholder struct passed in is the result of an alloca
> +//
>  // 
> ===------------------------------------------------------------------- 
> ---===//
>
>  #define DEBUG_TYPE "sretpromotion"
>
> Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ 
> Scalar/CodeGenPrepare.cpp?rev=50861&r1=50860&r2=50861&view=diff
>
> ====================================================================== 
> ========
> --- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Thu May  8  
> 12:46:35 2008
> @@ -8,8 +8,8 @@
>  // 
> ===------------------------------------------------------------------- 
> ---===//
>  //
>  // This pass munges the code in the input function to better  
> prepare it for
> -// SelectionDAG-based code generation.  This works around  
> limitations in it's
> -// basic-block-at-a-time approach.  It should eventually be removed.
> +// SelectionDAG-based code generation. This works around  
> limitations in it's
> +// basic-block-at-a-time approach. It should eventually be removed.
>  //
>  // 
> ===------------------------------------------------------------------- 
> ---===//
>
>
> Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ 
> Scalar/JumpThreading.cpp?rev=50861&r1=50860&r2=50861&view=diff
>
> ====================================================================== 
> ========
> --- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Thu May  8  
> 12:46:35 2008
> @@ -9,6 +9,23 @@
>  //
>  // This file implements the Jump Threading pass.
>  //
> +// Jump threading tries to find distinct threads of control flow  
> running through
> +// a basic block. This pass looks at blocks that have multiple  
> predecessors and
> +// multiple successors.  If one or more of the predecessors of the  
> block can be
> +// proven to always cause a jump to one of the successors, we  
> forward the edge
> +// from the predecessor to the successor by duplicating the  
> contents of this
> +// block.
> +//
> +// An example of when this can occur is code like this:
> +//
> +//   if () { ...
> +//     X = 4;
> +//   }
> +//   if (X < 3) {
> +//
> +// In this case, the unconditional branch at the end of the first  
> if can be
> +// revectored to the false side of the second if.
> +//
>  // 
> ===------------------------------------------------------------------- 
> ---===//
>
>  #define DEBUG_TYPE "jump-threading"
> @@ -33,22 +50,6 @@
>            cl::init(6), cl::Hidden);
>
>  namespace {
> -  /// This pass performs 'jump threading', which looks at blocks  
> that have
> -  /// multiple predecessors and multiple successors.  If one or  
> more of the
> -  /// predecessors of the block can be proven to always jump to  
> one of the
> -  /// successors, we forward the edge from the predecessor to the  
> successor by
> -  /// duplicating the contents of this block.
> -  ///
> -  /// An example of when this can occur is code like this:
> -  ///
> -  ///   if () { ...
> -  ///     X = 4;
> -  ///   }
> -  ///   if (X < 3) {
> -  ///
> -  /// In this case, the unconditional branch at the end of the  
> first if can be
> -  /// revectored to the false side of the second if.
> -  ///
>    class VISIBILITY_HIDDEN JumpThreading : public FunctionPass {
>    public:
>      static char ID; // Pass identification
>
> Modified: llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ 
> Scalar/LoopDeletion.cpp?rev=50861&r1=50860&r2=50861&view=diff
>
> ====================================================================== 
> ========
> --- llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp Thu May  8  
> 12:46:35 2008
> @@ -7,10 +7,10 @@
>  //
>  // 
> ===------------------------------------------------------------------- 
> ---===//
>  //
> -// This file implements the Dead Loop Elimination Pass.  This pass is
> -// responsible for eliminating loops with non-infinite computable  
> trip counts
> -// that have no side effects or volatile instructions, and do not  
> contribute
> -// to the computation of the function's return value.
> +// This file implements the Dead Loop Deletion Pass. This pass is  
> responsible
> +// for eliminating loops with non-infinite computable trip counts  
> that have no
> +// side effects or volatile instructions, and do not contribute to  
> the
> +// computation of the function's return value.
>  //
>  // 
> ===------------------------------------------------------------------- 
> ---===//
>
>
>
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