[llvm-commits] [llvm] r76396 - /llvm/trunk/docs/LangRef.html
Chris Lattner
sabre at nondot.org
Sun Jul 19 22:55:22 PDT 2009
Author: lattner
Date: Mon Jul 20 00:55:19 2009
New Revision: 76396
URL: http://llvm.org/viewvc/llvm-project?rev=76396&view=rev
Log:
document llvm.used and llvm.metadata. Stub out llvm.global_[cd]tors
Modified:
llvm/trunk/docs/LangRef.html
Modified: llvm/trunk/docs/LangRef.html
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/LangRef.html?rev=76396&r1=76395&r2=76396&view=diff
==============================================================================
--- llvm/trunk/docs/LangRef.html (original)
+++ llvm/trunk/docs/LangRef.html Mon Jul 20 00:55:19 2009
@@ -91,6 +91,15 @@
<li><a href="#inlineasm">Inline Assembler Expressions</a></li>
</ol>
</li>
+ <li><a href="#intrinsic_globals">Intrinsic Global Variables</a>
+ <ol>
+ <li><a href="#intg_used">The '<tt>llvm.used</tt>' Global Variable</a></li>
+ <li><a href="#intg_global_ctors">The '<tt>llvm.global_ctors</tt>'
+ Global Variable</a></li>
+ <li><a href="#intg_global_dtors">The '<tt>llvm.global_dtors</tt>'
+ Global Variable</a></li>
+ </ol>
+ </li>
<li><a href="#instref">Instruction Reference</a>
<ol>
<li><a href="#terminators">Terminator Instructions</a>
@@ -2150,6 +2159,76 @@
</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="intrinsic_globals">Intrinsic Global Variables</a>
+</div>
+<!-- *********************************************************************** -->
+
+<p>LLVM has a number of "magic" global variables that contain data that affect
+code generation or other IR semantics. These are documented here. All globals
+of this sort should have a section specified as "llvm.metadata". This section
+and all globals that start with "llvm." are reserved for LLVM.</p>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+<a name="intg_used">The '<tt>llvm.used</tt>' Global Variable</a>
+</div>
+
+<div class="doc_text">
+
+<p>The <tt>@llvm.used</tt> global is an array with i8* element type which has <a
+href="#linkage_appending">appending linkage</a>. This array contains a list of
+pointers to global variables and functions which may optionally have a pointer
+cast formed of bitcast or getelementptr. For example, a legal use of it is:</p>
+
+<pre>
+ @X = global i8 4
+ @Y = global i32 123
+
+ @llvm.used = appending global [2 x i8*] [
+ i8* @X,
+ i8* bitcast (i32* @Y to i8*)
+ ], section "llvm.metadata"
+</pre>
+
+<p>If a global variable appears in the <tt>@llvm.used</tt> list, then the
+compiler, assembler, and linker are required to treat the symbol as if there is
+a reference to the global that it cannot see. For example, if a variable has
+internal linkage and no references other than that from the <tt>@llvm.used</tt>
+list, it cannot be deleted. This is commonly used to represent references from
+inline asms and other things the compiler cannot "see", and corresponds to
+"attribute((used))" in GNU C.</p>
+
+<p>On some targets, the code generator must emit a directive to the assembler or
+object file to prevent the assembler and linker from molesting the symbol.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+<a name="intg_global_ctors">The '<tt>llvm.global_ctors</tt>' Global Variable</a>
+</div>
+
+<div class="doc_text">
+
+<p>TODO: Describe this.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+<a name="intg_global_dtors">The '<tt>llvm.global_dtors</tt>' Global Variable</a>
+</div>
+
+<div class="doc_text">
+
+<p>TODO: Describe this.</p>
+
+</div>
+
+
<!-- *********************************************************************** -->
<div class="doc_section"> <a name="instref">Instruction Reference</a> </div>
<!-- *********************************************************************** -->
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