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2059 lines
87 KiB
HTML
2059 lines
87 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>LLVM Assembly Language Reference Manual</title>
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<link rel="stylesheet" href="llvm.css" type="text/css">
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</head>
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<body>
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<div class="doc_title"> LLVM Language Reference Manual </div>
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<ol>
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<li><a href="#abstract">Abstract</a></li>
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<li><a href="#introduction">Introduction</a></li>
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<li><a href="#identifiers">Identifiers</a></li>
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<li><a href="#typesystem">Type System</a>
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<ol>
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<li><a href="#t_primitive">Primitive Types</a>
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<ol>
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<li><a href="#t_classifications">Type Classifications</a></li>
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</ol>
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</li>
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<li><a href="#t_derived">Derived Types</a>
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<ol>
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<li><a href="#t_array">Array Type</a></li>
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<li><a href="#t_function">Function Type</a></li>
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<li><a href="#t_pointer">Pointer Type</a></li>
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<li><a href="#t_struct">Structure Type</a></li>
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<!-- <li><a href="#t_packed" >Packed Type</a> -->
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</ol>
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</li>
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</ol>
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</li>
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<li><a href="#highlevel">High Level Structure</a>
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<ol>
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<li><a href="#modulestructure">Module Structure</a></li>
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<li><a href="#globalvars">Global Variables</a></li>
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<li><a href="#functionstructure">Function Structure</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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<ol>
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<li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li>
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<li><a href="#i_br">'<tt>br</tt>' Instruction</a></li>
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<li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li>
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<li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li>
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<li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li>
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</ol>
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</li>
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<li><a href="#binaryops">Binary Operations</a>
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<ol>
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<li><a href="#i_add">'<tt>add</tt>' Instruction</a></li>
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<li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li>
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<li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li>
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<li><a href="#i_div">'<tt>div</tt>' Instruction</a></li>
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<li><a href="#i_rem">'<tt>rem</tt>' Instruction</a></li>
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<li><a href="#i_setcc">'<tt>set<i>cc</i></tt>' Instructions</a></li>
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</ol>
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</li>
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<li><a href="#bitwiseops">Bitwise Binary Operations</a>
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<ol>
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<li><a href="#i_and">'<tt>and</tt>' Instruction</a></li>
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<li><a href="#i_or">'<tt>or</tt>' Instruction</a></li>
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<li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li>
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<li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li>
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<li><a href="#i_shr">'<tt>shr</tt>' Instruction</a></li>
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</ol>
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</li>
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<li><a href="#memoryops">Memory Access Operations</a>
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<ol>
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<li><a href="#i_malloc">'<tt>malloc</tt>' Instruction</a></li>
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<li><a href="#i_free">'<tt>free</tt>' Instruction</a></li>
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<li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li>
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<li><a href="#i_load">'<tt>load</tt>' Instruction</a></li>
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<li><a href="#i_store">'<tt>store</tt>' Instruction</a></li>
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<li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li>
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</ol>
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</li>
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<li><a href="#otherops">Other Operations</a>
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<ol>
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<li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li>
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<li><a href="#i_cast">'<tt>cast .. to</tt>' Instruction</a></li>
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<li><a href="#i_call">'<tt>call</tt>' Instruction</a></li>
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<li><a href="#i_vanext">'<tt>vanext</tt>' Instruction</a></li>
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<li><a href="#i_vaarg">'<tt>vaarg</tt>' Instruction</a></li>
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</ol>
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</li>
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</ol>
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</li>
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<li><a href="#intrinsics">Intrinsic Functions</a>
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<ol>
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<li><a href="#int_varargs">Variable Argument Handling Intrinsics</a>
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<ol>
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<li><a href="#i_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li>
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<li><a href="#i_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li>
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<li><a href="#i_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li>
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</ol>
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</li>
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<li><a href="#int_codegen">Code Generator Intrinsics</a>
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<ol>
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<li><a href="#i_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li>
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<li><a href="#i_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li>
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</ol>
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</li>
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<li><a href="#int_libc">Standard C Library Intrinsics</a>
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<ol>
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<li><a href="#i_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a></li>
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<li><a href="#i_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a></li>
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<li><a href="#i_memset">'<tt>llvm.memset</tt>' Intrinsic</a></li>
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</ol>
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</li>
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<li><a href="#int_debugger">Debugger intrinsics</a>
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</ol>
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</li>
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</ol>
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<div class="doc_text">
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<p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
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and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></b></p>
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<p> </p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"> <a name="abstract">Abstract </a></div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This document is a reference manual for the LLVM assembly language.
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LLVM is an SSA based representation that provides type safety,
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low-level operations, flexibility, and the capability of representing
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'all' high-level languages cleanly. It is the common code
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representation used throughout all phases of the LLVM compilation
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strategy.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"> <a name="introduction">Introduction</a> </div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>The LLVM code representation is designed to be used in three
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different forms: as an in-memory compiler IR, as an on-disk bytecode
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representation (suitable for fast loading by a Just-In-Time compiler),
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and as a human readable assembly language representation. This allows
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LLVM to provide a powerful intermediate representation for efficient
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compiler transformations and analysis, while providing a natural means
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to debug and visualize the transformations. The three different forms
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of LLVM are all equivalent. This document describes the human readable
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representation and notation.</p>
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<p>The LLVM representation aims to be a light-weight and low-level
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while being expressive, typed, and extensible at the same time. It
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aims to be a "universal IR" of sorts, by being at a low enough level
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that high-level ideas may be cleanly mapped to it (similar to how
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microprocessors are "universal IR's", allowing many source languages to
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be mapped to them). By providing type information, LLVM can be used as
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the target of optimizations: for example, through pointer analysis, it
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can be proven that a C automatic variable is never accessed outside of
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the current function... allowing it to be promoted to a simple SSA
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value instead of a memory location.</p>
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</div>
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<!-- _______________________________________________________________________ -->
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<div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div>
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<div class="doc_text">
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<p>It is important to note that this document describes 'well formed'
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LLVM assembly language. There is a difference between what the parser
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accepts and what is considered 'well formed'. For example, the
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following instruction is syntactically okay, but not well formed:</p>
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<pre> %x = <a href="#i_add">add</a> int 1, %x<br></pre>
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<p>...because the definition of <tt>%x</tt> does not dominate all of
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its uses. The LLVM infrastructure provides a verification pass that may
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be used to verify that an LLVM module is well formed. This pass is
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automatically run by the parser after parsing input assembly, and by
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the optimizer before it outputs bytecode. The violations pointed out
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by the verifier pass indicate bugs in transformation passes or input to
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the parser.</p>
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<!-- Describe the typesetting conventions here. --> </div>
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<!-- *********************************************************************** -->
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<div class="doc_section"> <a name="identifiers">Identifiers</a> </div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>LLVM uses three different forms of identifiers, for different
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purposes:</p>
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<ol>
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<li>Numeric constants are represented as you would expect: 12, -3
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123.421, etc. Floating point constants have an optional hexidecimal
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notation.</li>
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<li>Named values are represented as a string of characters with a '%'
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prefix. For example, %foo, %DivisionByZero,
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%a.really.long.identifier. The actual regular expression used is '<tt>%[a-zA-Z$._][a-zA-Z$._0-9]*</tt>'.
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Identifiers which require other characters in their names can be
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surrounded with quotes. In this way, anything except a <tt>"</tt>
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character can be used in a name.</li>
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<li>Unnamed values are represented as an unsigned numeric value with
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a '%' prefix. For example, %12, %2, %44.</li>
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</ol>
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<p>LLVM requires the values start with a '%' sign for two reasons:
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Compilers don't need to worry about name clashes with reserved words,
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and the set of reserved words may be expanded in the future without
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penalty. Additionally, unnamed identifiers allow a compiler to quickly
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come up with a temporary variable without having to avoid symbol table
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conflicts.</p>
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<p>Reserved words in LLVM are very similar to reserved words in other
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languages. There are keywords for different opcodes ('<tt><a
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href="#i_add">add</a></tt>', '<tt><a href="#i_cast">cast</a></tt>', '<tt><a
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href="#i_ret">ret</a></tt>', etc...), for primitive type names ('<tt><a
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href="#t_void">void</a></tt>', '<tt><a href="#t_uint">uint</a></tt>',
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etc...), and others. These reserved words cannot conflict with
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variable names, because none of them start with a '%' character.</p>
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<p>Here is an example of LLVM code to multiply the integer variable '<tt>%X</tt>'
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by 8:</p>
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<p>The easy way:</p>
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<pre> %result = <a href="#i_mul">mul</a> uint %X, 8<br></pre>
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<p>After strength reduction:</p>
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<pre> %result = <a href="#i_shl">shl</a> uint %X, ubyte 3<br></pre>
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<p>And the hard way:</p>
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<pre> <a href="#i_add">add</a> uint %X, %X <i>; yields {uint}:%0</i>
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<a
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href="#i_add">add</a> uint %0, %0 <i>; yields {uint}:%1</i>
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%result = <a
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href="#i_add">add</a> uint %1, %1<br></pre>
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<p>This last way of multiplying <tt>%X</tt> by 8 illustrates several
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important lexical features of LLVM:</p>
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<ol>
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<li>Comments are delimited with a '<tt>;</tt>' and go until the end
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of line.</li>
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<li>Unnamed temporaries are created when the result of a computation
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is not assigned to a named value.</li>
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<li>Unnamed temporaries are numbered sequentially</li>
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</ol>
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<p>...and it also show a convention that we follow in this document.
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When demonstrating instructions, we will follow an instruction with a
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comment that defines the type and name of value produced. Comments are
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shown in italic text.</p>
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<p>The one non-intuitive notation for constants is the optional
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hexidecimal form of floating point constants. For example, the form '<tt>double
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0x432ff973cafa8000</tt>' is equivalent to (but harder to read than) '<tt>double
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4.5e+15</tt>' which is also supported by the parser. The only time
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hexadecimal floating point constants are useful (and the only time that
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they are generated by the disassembler) is when an FP constant has to
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be emitted that is not representable as a decimal floating point number
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exactly. For example, NaN's, infinities, and other special cases are
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represented in their IEEE hexadecimal format so that assembly and
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disassembly do not cause any bits to change in the constants.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"> <a name="typesystem">Type System</a> </div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>The LLVM type system is one of the most important features of the
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intermediate representation. Being typed enables a number of
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optimizations to be performed on the IR directly, without having to do
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extra analyses on the side before the transformation. A strong type
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system makes it easier to read the generated code and enables novel
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analyses and transformations that are not feasible to perform on normal
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three address code representations.</p>
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<!-- The written form for the type system was heavily influenced by the
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syntactic problems with types in the C language<sup><a
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href="#rw_stroustrup">1</a></sup>.<p> --> </div>
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<!-- ======================================================================= -->
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<div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div>
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<div class="doc_text">
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<p>The primitive types are the fundemental building blocks of the LLVM
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system. The current set of primitive types are as follows:</p>
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<p>
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<table border="0" align="center">
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<tbody>
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<tr>
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<td>
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<table border="1" cellspacing="0" cellpadding="4" align="center">
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<tbody>
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<tr>
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<td><tt>void</tt></td>
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<td>No value</td>
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</tr>
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<tr>
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<td><tt>ubyte</tt></td>
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<td>Unsigned 8 bit value</td>
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</tr>
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<tr>
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<td><tt>ushort</tt></td>
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<td>Unsigned 16 bit value</td>
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</tr>
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<tr>
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<td><tt>uint</tt></td>
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<td>Unsigned 32 bit value</td>
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</tr>
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<tr>
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<td><tt>ulong</tt></td>
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<td>Unsigned 64 bit value</td>
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</tr>
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<tr>
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<td><tt>float</tt></td>
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<td>32 bit floating point value</td>
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</tr>
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<tr>
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<td><tt>label</tt></td>
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<td>Branch destination</td>
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</tr>
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</tbody>
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</table>
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</td>
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<td valign="top">
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<table border="1" cellspacing="0" cellpadding="4" align="center"">
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<tbody>
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<tr>
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<td><tt>bool</tt></td>
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<td>True or False value</td>
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</tr>
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<tr>
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<td><tt>sbyte</tt></td>
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<td>Signed 8 bit value</td>
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</tr>
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<tr>
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<td><tt>short</tt></td>
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<td>Signed 16 bit value</td>
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</tr>
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<tr>
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<td><tt>int</tt></td>
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<td>Signed 32 bit value</td>
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</tr>
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<tr>
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<td><tt>long</tt></td>
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<td>Signed 64 bit value</td>
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</tr>
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<tr>
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<td><tt>double</tt></td>
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<td>64 bit floating point value</td>
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</tr>
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</tbody>
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</table>
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</td>
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</tr>
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</tbody>
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</table>
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</p>
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</div>
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<!-- _______________________________________________________________________ -->
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<div class="doc_subsubsection"> <a name="t_classifications">Type
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Classifications</a> </div>
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<div class="doc_text">
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<p>These different primitive types fall into a few useful
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classifications:</p>
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<p>
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<table border="1" cellspacing="0" cellpadding="4" align="center">
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<tbody>
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<tr>
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<td><a name="t_signed">signed</a></td>
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<td><tt>sbyte, short, int, long, float, double</tt></td>
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</tr>
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<tr>
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<td><a name="t_unsigned">unsigned</a></td>
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<td><tt>ubyte, ushort, uint, ulong</tt></td>
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</tr>
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<tr>
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<td><a name="t_integer">integer</a></td>
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<td><tt>ubyte, sbyte, ushort, short, uint, int, ulong, long</tt></td>
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</tr>
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<tr>
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<td><a name="t_integral">integral</a></td>
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<td><tt>bool, ubyte, sbyte, ushort, short, uint, int, ulong, long</tt></td>
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</tr>
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<tr>
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<td><a name="t_floating">floating point</a></td>
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<td><tt>float, double</tt></td>
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</tr>
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<tr>
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<td><a name="t_firstclass">first class</a></td>
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<td><tt>bool, ubyte, sbyte, ushort, short,<br>
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uint, int, ulong, long, float, double, <a href="#t_pointer">pointer</a></tt></td>
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</tr>
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|
</tbody>
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|
</table>
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</p>
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|
<p>The <a href="#t_firstclass">first class</a> types are perhaps the
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most important. Values of these types are the only ones which can be
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produced by instructions, passed as arguments, or used as operands to
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|
instructions. This means that all structures and arrays must be
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|
manipulated either by pointer or by component.</p>
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|
</div>
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|
<!-- ======================================================================= -->
|
|
<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.
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This is what allows a programmer to represent arrays, functions,
|
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pointers, and other useful types. Note that these derived types may be
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recursive: For example, it is possible to have a two dimensional array.</p>
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</div>
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<!-- _______________________________________________________________________ -->
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<div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div>
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<div class="doc_text">
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<h5>Overview:</h5>
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<p>The array type is a very simple derived type that arranges elements
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sequentially in memory. The array type requires a size (number of
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elements) and an underlying data type.</p>
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<h5>Syntax:</h5>
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|
<pre> [<# elements> x <elementtype>]<br></pre>
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|
<p>The number of elements is a constant integer value, elementtype may
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be any type with a size.</p>
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<h5>Examples:</h5>
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|
<p> <tt>[40 x int ]</tt>: Array of 40 integer values.<br>
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<tt>[41 x int ]</tt>: Array of 41 integer values.<br>
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<tt>[40 x uint]</tt>: Array of 40 unsigned integer values.</p>
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<p> </p>
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<p>Here are some examples of multidimensional arrays:</p>
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<p>
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|
<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>
|
|
</p>
|
|
</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>
|
|
<p>
|
|
<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>
|
|
</p>
|
|
</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>
|
|
<p>
|
|
<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>
|
|
</p>
|
|
</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>
|
|
<p>
|
|
<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>
|
|
</p>
|
|
</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>
|
|
<a name="linkage_internal"> <dt><tt><b>internal</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>
|
|
</a><a name="linkage_linkonce"> <dt><tt><b>linkonce</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>
|
|
</a><a name="linkage_weak"> <dt><tt><b>weak</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>
|
|
</a><a name="linkage_appending"> <dt><tt><b>appending</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>
|
|
</a><a name="linkage_external"> <dt><tt><b>externally visible</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>
|
|
</a>
|
|
</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). Constants must always have an
|
|
initial value.</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>
|
|
<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>
|
|
</center>
|
|
<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>
|
|
<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>
|
|
</center>
|
|
<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>
|
|
<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>
|
|
</center>
|
|
<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_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">
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<p>
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The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt> prefix),
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are described in the <a
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href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source Level
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Debugging</a> document.
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</p>
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</div>
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<!-- *********************************************************************** -->
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<hr>
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<div class="doc_footer">
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<address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
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<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a> <br>
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Last modified: $Date$ </div>
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</body>
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</html>
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