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document llvm.used and llvm.metadata. Stub out llvm.global_[cd]tors
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76396 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -91,6 +91,15 @@
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<li><a href="#inlineasm">Inline Assembler Expressions</a></li>
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</ol>
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</li>
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<li><a href="#intrinsic_globals">Intrinsic Global Variables</a>
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<ol>
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<li><a href="#intg_used">The '<tt>llvm.used</tt>' Global Variable</a></li>
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<li><a href="#intg_global_ctors">The '<tt>llvm.global_ctors</tt>'
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Global Variable</a></li>
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<li><a href="#intg_global_dtors">The '<tt>llvm.global_dtors</tt>'
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Global Variable</a></li>
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</ol>
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</li>
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<li><a href="#instref">Instruction Reference</a>
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<ol>
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<li><a href="#terminators">Terminator Instructions</a>
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@ -2150,6 +2159,76 @@ call void asm sideeffect "eieio", ""()
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="intrinsic_globals">Intrinsic Global Variables</a>
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</div>
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<!-- *********************************************************************** -->
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<p>LLVM has a number of "magic" global variables that contain data that affect
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code generation or other IR semantics. These are documented here. All globals
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of this sort should have a section specified as "llvm.metadata". This section
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and all globals that start with "llvm." are reserved for LLVM.</p>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="intg_used">The '<tt>llvm.used</tt>' Global Variable</a>
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</div>
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<div class="doc_text">
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<p>The <tt>@llvm.used</tt> global is an array with i8* element type which has <a
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href="#linkage_appending">appending linkage</a>. This array contains a list of
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pointers to global variables and functions which may optionally have a pointer
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cast formed of bitcast or getelementptr. For example, a legal use of it is:</p>
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<pre>
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@X = global i8 4
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@Y = global i32 123
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@llvm.used = appending global [2 x i8*] [
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i8* @X,
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i8* bitcast (i32* @Y to i8*)
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], section "llvm.metadata"
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</pre>
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<p>If a global variable appears in the <tt>@llvm.used</tt> list, then the
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compiler, assembler, and linker are required to treat the symbol as if there is
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a reference to the global that it cannot see. For example, if a variable has
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internal linkage and no references other than that from the <tt>@llvm.used</tt>
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list, it cannot be deleted. This is commonly used to represent references from
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inline asms and other things the compiler cannot "see", and corresponds to
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"attribute((used))" in GNU C.</p>
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<p>On some targets, the code generator must emit a directive to the assembler or
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object file to prevent the assembler and linker from molesting the symbol.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="intg_global_ctors">The '<tt>llvm.global_ctors</tt>' Global Variable</a>
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</div>
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<div class="doc_text">
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<p>TODO: Describe this.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="intg_global_dtors">The '<tt>llvm.global_dtors</tt>' Global Variable</a>
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</div>
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<div class="doc_text">
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<p>TODO: Describe this.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"> <a name="instref">Instruction Reference</a> </div>
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<!-- *********************************************************************** -->
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