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path on alpha, now has come the time for new vararg support. So, with out further ado, I revert behavior back a couple of years! Well, ok, I lied. A few more notes. First, the Simple ISels cannot be expected to work any longer, but they should still compile Second, there are likely some bugs to track down once the nightly testers start with this. Third, the initial patch doesn't include sparcv9, but I'll do that today. Forth, subsequent patches won't bother being long winded. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22251 91177308-0d34-0410-b5e6-96231b3b80d8
3269 lines
117 KiB
HTML
3269 lines
117 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"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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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="author" content="Chris Lattner">
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<meta name="description"
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content="LLVM Assembly Language Reference Manual.">
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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="#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="#linkage">Linkage Types</a></li>
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<li><a href="#callingconv">Calling Conventions</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="#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></li>
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<li><a href="#t_opaque">Opaque Type</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="#constants">Constants</a>
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<ol>
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<li><a href="#simpleconstants">Simple Constants</a>
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<li><a href="#aggregateconstants">Aggregate Constants</a>
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<li><a href="#globalconstants">Global Variable and Function Addresses</a>
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<li><a href="#undefvalues">Undefined Values</a>
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<li><a href="#constantexprs">Constant Expressions</a>
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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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<li><a href="#i_unreachable">'<tt>unreachable</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_select">'<tt>select</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_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_gc">Accurate Garbage Collection Intrinsics</a>
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<ol>
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<li><a href="#i_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li>
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<li><a href="#i_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li>
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<li><a href="#i_gcwrite">'<tt>llvm.gcwrite</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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<li><a href="#i_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li>
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<li><a href="#i_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li>
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</ol>
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</li>
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<li><a href="#int_os">Operating System Intrinsics</a>
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<ol>
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<li><a href="#i_readport">'<tt>llvm.readport</tt>' Intrinsic</a></li>
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<li><a href="#i_writeport">'<tt>llvm.writeport</tt>' Intrinsic</a></li>
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<li><a href="#i_readio">'<tt>llvm.readio</tt>' Intrinsic</a></li>
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<li><a href="#i_writeio">'<tt>llvm.writeio</tt>' Intrinsic</a></li>
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</ol>
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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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<li><a href="#i_isunordered">'<tt>llvm.isunordered</tt>' Intrinsic</a></li>
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</ol>
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</li>
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<li><a href="#int_count">Bit counting Intrinsics</a>
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<ol>
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<li><a href="#int_ctpop">'<tt>llvm.ctpop</tt>' Intrinsic </a></li>
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<li><a href="#int_ctlz">'<tt>llvm.ctlz</tt>' Intrinsic </a></li>
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<li><a href="#int_cttz">'<tt>llvm.cttz</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></li>
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</ol>
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</li>
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</ol>
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<div class="doc_author">
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<p>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></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 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>
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%x = <a href="#i_add">add</a> int 1, %x
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</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>Named values are represented as a string of characters with a '%' prefix.
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For example, %foo, %DivisionByZero, %a.really.long.identifier. The actual
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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 surrounded
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with quotes. In this way, anything except a <tt>"</tt> character can be used
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in a name.</li>
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<li>Unnamed values are represented as an unsigned numeric value with a '%'
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prefix. For example, %12, %2, %44.</li>
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<li>Constants, which are described in a <a href="#constants">section about
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constants</a>, below.</li>
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</ol>
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<p>LLVM requires that values start with a '%' sign for two reasons: Compilers
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don't need to worry about name clashes with reserved words, and the set of
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reserved words may be expanded in the future without penalty. Additionally,
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unnamed identifiers allow a compiler to quickly come up with a temporary
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variable without having to avoid symbol table 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>', etc...),
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and others. These reserved words cannot conflict with variable names, because
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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
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'<tt>%X</tt>' by 8:</p>
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<p>The easy way:</p>
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<pre>
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%result = <a href="#i_mul">mul</a> uint %X, 8
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</pre>
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<p>After strength reduction:</p>
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<pre>
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%result = <a href="#i_shl">shl</a> uint %X, ubyte 3
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</pre>
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<p>And the hard way:</p>
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<pre>
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<a href="#i_add">add</a> uint %X, %X <i>; yields {uint}:%0</i>
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<a href="#i_add">add</a> uint %0, %0 <i>; yields {uint}:%1</i>
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%result = <a href="#i_add">add</a> uint %1, %1
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</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 of
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line.</li>
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<li>Unnamed temporaries are created when the result of a computation is not
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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 shows a convention that we follow in this document. When
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demonstrating instructions, we will follow an instruction with a comment that
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defines the type and name of value produced. Comments are shown in italic
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text.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"> <a name="highlevel">High Level Structure</a> </div>
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<!-- *********************************************************************** -->
|
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<!-- ======================================================================= -->
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<div class="doc_subsection"> <a name="modulestructure">Module Structure</a>
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</div>
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<div class="doc_text">
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<p>LLVM programs are composed of "Module"s, each of which is a
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translation unit of the input programs. Each module consists of
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functions, global variables, and symbol table entries. Modules may be
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combined together with the LLVM linker, which merges function (and
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global variable) definitions, resolves forward declarations, and merges
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symbol table entries. Here is an example of the "hello world" module:</p>
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|
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<pre><i>; Declare the string constant as a global constant...</i>
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<a href="#identifiers">%.LC0</a> = <a href="#linkage_internal">internal</a> <a
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href="#globalvars">constant</a> <a href="#t_array">[13 x sbyte]</a> c"hello world\0A\00" <i>; [13 x sbyte]*</i>
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<i>; External declaration of the puts function</i>
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<a href="#functionstructure">declare</a> int %puts(sbyte*) <i>; int(sbyte*)* </i>
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<i>; Definition of main function</i>
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int %main() { <i>; int()* </i>
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<i>; Convert [13x sbyte]* to sbyte *...</i>
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%cast210 = <a
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href="#i_getelementptr">getelementptr</a> [13 x sbyte]* %.LC0, long 0, long 0 <i>; sbyte*</i>
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<i>; Call puts function to write out the string to stdout...</i>
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<a
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href="#i_call">call</a> int %puts(sbyte* %cast210) <i>; int</i>
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<a
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href="#i_ret">ret</a> int 0<br>}<br></pre>
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|
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|
<p>This example is made up of a <a href="#globalvars">global variable</a>
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named "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>"
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function, and a <a href="#functionstructure">function definition</a>
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for "<tt>main</tt>".</p>
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<p>In general, a module is made up of a list of global values,
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where both functions and global variables are global values. Global values are
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represented by a pointer to a memory location (in this case, a pointer to an
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array of char, and a pointer to a function), and have one of the following <a
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href="#linkage">linkage types</a>.</p>
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|
|
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</div>
|
|
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|
<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="linkage">Linkage Types</a>
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</div>
|
|
|
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<div class="doc_text">
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|
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<p>
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All Global Variables and Functions have one of the following types of linkage:
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</p>
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|
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<dl>
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|
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<dt><tt><b><a name="linkage_internal">internal</a></b></tt> </dt>
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<dd>Global values with internal linkage are only directly accessible by
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objects in the current module. In particular, linking code into a module with
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|
an internal global value may cause the internal to be renamed as necessary to
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|
avoid collisions. Because the symbol is internal to the module, all
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|
references can be updated. This corresponds to the notion of the
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'<tt>static</tt>' keyword in C, or the idea of "anonymous namespaces" in C++.
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</dd>
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<dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt>
|
|
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<dd>"<tt>linkonce</tt>" linkage is similar to <tt>internal</tt> linkage, with
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the twist that linking together two modules defining the same
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<tt>linkonce</tt> globals will cause one of the globals to be discarded. This
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|
is typically used to implement inline functions. Unreferenced
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<tt>linkonce</tt> globals are allowed to be discarded.
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</dd>
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<dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt>
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<dd>"<tt>weak</tt>" linkage is exactly the same as <tt>linkonce</tt> linkage,
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except that unreferenced <tt>weak</tt> globals may not be discarded. This is
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used to implement constructs in C such as "<tt>int X;</tt>" at global scope.
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</dd>
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|
|
<dt><tt><b><a name="linkage_appending">appending</a></b></tt>: </dt>
|
|
|
|
<dd>"<tt>appending</tt>" linkage may only be applied to global variables of
|
|
pointer to array type. When two global variables with appending linkage are
|
|
linked together, the two global arrays are appended together. This is the
|
|
LLVM, typesafe, equivalent of having the system linker append together
|
|
"sections" with identical names when .o files are linked.
|
|
</dd>
|
|
|
|
<dt><tt><b><a name="linkage_external">externally visible</a></b></tt>:</dt>
|
|
|
|
<dd>If none of the above identifiers are used, the global is externally
|
|
visible, meaning that it participates in linkage and can be used to resolve
|
|
external symbol references.
|
|
</dd>
|
|
</dl>
|
|
|
|
<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="callingconv">Calling Conventions</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a>
|
|
and <a href="#i_invoke">invokes</a> can all have an optional calling convention
|
|
specified for the call. The calling convention of any pair of dynamic
|
|
caller/callee must match, or the behavior of the program is undefined. The
|
|
following calling conventions are supported by LLVM, and more may be added in
|
|
the future:</p>
|
|
|
|
<dl>
|
|
<dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt>
|
|
|
|
<dd>This calling convention (the default if no other calling convention is
|
|
specified) matches the target C calling conventions. This calling convention
|
|
supports varargs function calls and tolerates some mismatch in the declared
|
|
prototype and implemented declaration of the function (as does normal C).
|
|
</dd>
|
|
|
|
<dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt>
|
|
|
|
<dd>This calling convention attempts to make calls as fast as possible
|
|
(e.g. by passing things in registers). This calling convention allows the
|
|
target to use whatever tricks it wants to produce fast code for the target,
|
|
without having to conform to an externally specified ABI. Implementations of
|
|
this convention should allow arbitrary tail call optimization to be supported.
|
|
This calling convention does not support varargs and requires the prototype of
|
|
all callees to exactly match the prototype of the function definition.
|
|
</dd>
|
|
|
|
<dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt>
|
|
|
|
<dd>This calling convention attempts to make code in the caller as efficient
|
|
as possible under the assumption that the call is not commonly executed. As
|
|
such, these calls often preserve all registers so that the call does not break
|
|
any live ranges in the caller side. This calling convention does not support
|
|
varargs and requires the prototype of all callees to exactly match the
|
|
prototype of the function definition.
|
|
</dd>
|
|
|
|
<dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt>
|
|
|
|
<dd>Any calling convention may be specified by number, allowing
|
|
target-specific calling conventions to be used. Target specific calling
|
|
conventions start at 64.
|
|
</dd>
|
|
</dl>
|
|
|
|
<p>More calling conventions can be added/defined on an as-needed basis, to
|
|
support pascal conventions or any other well-known target-independent
|
|
convention.</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 <b>never</b> be modified (enabling better
|
|
optimization, allowing the global data to be placed in the read-only section of
|
|
an executable, etc). Note that variables that need runtime initialization
|
|
cannot be marked "constant", as there is a store to the variable.</p>
|
|
|
|
<p>
|
|
LLVM explicitly allows <em>declarations</em> of global variables to be marked
|
|
constant, even if the final definition of the global is not. This capability
|
|
can be used to enable slightly better optimization of the program, but requires
|
|
the language definition to guarantee that optimizations based on the
|
|
'constantness' are valid for the translation units that do not include the
|
|
definition.
|
|
</p>
|
|
|
|
<p>As SSA values, global variables define pointer values that are in
|
|
scope (i.e. they dominate) 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 consist of an optional <a href="#linkage">linkage
|
|
type</a>, an optional <a href="#callingconv">calling convention</a>, a return
|
|
type, a function name, 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, an optional <a
|
|
href="#callingconv">calling convention</a>, a return type, a function name, and
|
|
a possibly empty list of arguments.</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 a 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 resolve references to each
|
|
appropriately.</p>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section"> <a name="typesystem">Type System</a> </div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The LLVM type system is one of the most important features of the
|
|
intermediate representation. Being typed enables a number of
|
|
optimizations to be performed on the IR directly, without having to do
|
|
extra analyses on the side before the transformation. A strong type
|
|
system makes it easier to read the generated code and enables novel
|
|
analyses and transformations that are not feasible to perform on normal
|
|
three address code representations.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div>
|
|
<div class="doc_text">
|
|
<p>The primitive types are the fundamental building blocks of the LLVM
|
|
system. The current set of primitive types is as follows:</p>
|
|
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left">
|
|
<table>
|
|
<tbody>
|
|
<tr><th>Type</th><th>Description</th></tr>
|
|
<tr><td><tt>void</tt></td><td>No value</td></tr>
|
|
<tr><td><tt>ubyte</tt></td><td>Unsigned 8-bit value</td></tr>
|
|
<tr><td><tt>ushort</tt></td><td>Unsigned 16-bit value</td></tr>
|
|
<tr><td><tt>uint</tt></td><td>Unsigned 32-bit value</td></tr>
|
|
<tr><td><tt>ulong</tt></td><td>Unsigned 64-bit value</td></tr>
|
|
<tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr>
|
|
<tr><td><tt>label</tt></td><td>Branch destination</td></tr>
|
|
</tbody>
|
|
</table>
|
|
</td>
|
|
<td class="right">
|
|
<table>
|
|
<tbody>
|
|
<tr><th>Type</th><th>Description</th></tr>
|
|
<tr><td><tt>bool</tt></td><td>True or False value</td></tr>
|
|
<tr><td><tt>sbyte</tt></td><td>Signed 8-bit value</td></tr>
|
|
<tr><td><tt>short</tt></td><td>Signed 16-bit value</td></tr>
|
|
<tr><td><tt>int</tt></td><td>Signed 32-bit value</td></tr>
|
|
<tr><td><tt>long</tt></td><td>Signed 64-bit value</td></tr>
|
|
<tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr>
|
|
</tbody>
|
|
</table>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="t_classifications">Type
|
|
Classifications</a> </div>
|
|
<div class="doc_text">
|
|
<p>These different primitive types fall into a few useful
|
|
classifications:</p>
|
|
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<tbody>
|
|
<tr><th>Classification</th><th>Types</th></tr>
|
|
<tr>
|
|
<td><a name="t_signed">signed</a></td>
|
|
<td><tt>sbyte, short, int, long, float, double</tt></td>
|
|
</tr>
|
|
<tr>
|
|
<td><a name="t_unsigned">unsigned</a></td>
|
|
<td><tt>ubyte, ushort, uint, ulong</tt></td>
|
|
</tr>
|
|
<tr>
|
|
<td><a name="t_integer">integer</a></td>
|
|
<td><tt>ubyte, sbyte, ushort, short, uint, int, ulong, long</tt></td>
|
|
</tr>
|
|
<tr>
|
|
<td><a name="t_integral">integral</a></td>
|
|
<td><tt>bool, ubyte, sbyte, ushort, short, uint, int, ulong, long</tt>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td><a name="t_floating">floating point</a></td>
|
|
<td><tt>float, double</tt></td>
|
|
</tr>
|
|
<tr>
|
|
<td><a name="t_firstclass">first class</a></td>
|
|
<td><tt>bool, ubyte, sbyte, ushort, short, uint, int, ulong, long,<br>
|
|
float, double, <a href="#t_pointer">pointer</a>,
|
|
<a href="#t_packed">packed</a></tt></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
<p>The <a href="#t_firstclass">first class</a> types are perhaps the
|
|
most important. Values of these types are the only ones which can be
|
|
produced by instructions, passed as arguments, or used as operands to
|
|
instructions. This means that all structures and arrays must be
|
|
manipulated either by pointer or by component.</p>
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection"> <a name="t_derived">Derived Types</a> </div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The real power in LLVM comes from the derived types in the system.
|
|
This is what allows a programmer to represent arrays, functions,
|
|
pointers, and other useful types. Note that these derived types may be
|
|
recursive: For example, it is possible to have a two dimensional array.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>The array type is a very simple derived type that arranges elements
|
|
sequentially in memory. The array type requires a size (number of
|
|
elements) and an underlying data type.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
|
|
<pre>
|
|
[<# elements> x <elementtype>]
|
|
</pre>
|
|
|
|
<p>The number of elements is a constant integer value; elementtype may
|
|
be any type with a size.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left">
|
|
<tt>[40 x int ]</tt><br/>
|
|
<tt>[41 x int ]</tt><br/>
|
|
<tt>[40 x uint]</tt><br/>
|
|
</td>
|
|
<td class="left">
|
|
Array of 40 integer values.<br/>
|
|
Array of 41 integer values.<br/>
|
|
Array of 40 unsigned integer values.<br/>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
<p>Here are some examples of multidimensional arrays:</p>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left">
|
|
<tt>[3 x [4 x int]]</tt><br/>
|
|
<tt>[12 x [10 x float]]</tt><br/>
|
|
<tt>[2 x [3 x [4 x uint]]]</tt><br/>
|
|
</td>
|
|
<td class="left">
|
|
3x4 array of integer values.<br/>
|
|
12x10 array of single precision floating point values.<br/>
|
|
2x3x4 array of unsigned integer values.<br/>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Overview:</h5>
|
|
<p>The function type can be thought of as a function signature. It
|
|
consists of a return type and a list of formal parameter types.
|
|
Function types are usually used to build virtual function tables
|
|
(which are structures of pointers to functions), for indirect function
|
|
calls, and when defining a function.</p>
|
|
<p>
|
|
The return type of a function type cannot be an aggregate type.
|
|
</p>
|
|
<h5>Syntax:</h5>
|
|
<pre> <returntype> (<parameter list>)<br></pre>
|
|
<p>Where '<tt><parameter list></tt>' is a comma-separated list of type
|
|
specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
|
|
which indicates that the function takes a variable number of arguments.
|
|
Variable argument functions can access their arguments with the <a
|
|
href="#int_varargs">variable argument handling intrinsic</a> functions.</p>
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left">
|
|
<tt>int (int)</tt> <br/>
|
|
<tt>float (int, int *) *</tt><br/>
|
|
<tt>int (sbyte *, ...)</tt><br/>
|
|
</td>
|
|
<td class="left">
|
|
function taking an <tt>int</tt>, returning an <tt>int</tt><br/>
|
|
<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>.<br/>
|
|
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.<br/>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="t_struct">Structure Type</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Overview:</h5>
|
|
<p>The structure type is used to represent a collection of data members
|
|
together in memory. The packing of the field types is defined to match
|
|
the ABI of the underlying processor. The elements of a structure may
|
|
be any type that has a size.</p>
|
|
<p>Structures are accessed using '<tt><a href="#i_load">load</a></tt>
|
|
and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a
|
|
field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>'
|
|
instruction.</p>
|
|
<h5>Syntax:</h5>
|
|
<pre> { <type list> }<br></pre>
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left">
|
|
<tt>{ int, int, int }</tt><br/>
|
|
<tt>{ float, int (int) * }</tt><br/>
|
|
</td>
|
|
<td class="left">
|
|
a triple of three <tt>int</tt> values<br/>
|
|
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>.<br/>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Overview:</h5>
|
|
<p>As in many languages, the pointer type represents a pointer or
|
|
reference to another object, which must live in memory.</p>
|
|
<h5>Syntax:</h5>
|
|
<pre> <type> *<br></pre>
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left">
|
|
<tt>[4x int]*</tt><br/>
|
|
<tt>int (int *) *</tt><br/>
|
|
</td>
|
|
<td class="left">
|
|
A <a href="#t_pointer">pointer</a> to <a href="#t_array">array</a> of
|
|
four <tt>int</tt> values<br/>
|
|
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>.<br/>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="t_packed">Packed Type</a> </div>
|
|
<div class="doc_text">
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>A packed type is a simple derived type that represents a vector
|
|
of elements. Packed types are used when multiple primitive data
|
|
are operated in parallel using a single instruction (SIMD).
|
|
A packed type requires a size (number of
|
|
elements) and an underlying primitive data type. Packed types are
|
|
considered <a href="#t_firstclass">first class</a>.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
|
|
<pre>
|
|
< <# elements> x <elementtype> >
|
|
</pre>
|
|
|
|
<p>The number of elements is a constant integer value; elementtype may
|
|
be any integral or floating point type.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left">
|
|
<tt><4 x int></tt><br/>
|
|
<tt><8 x float></tt><br/>
|
|
<tt><2 x uint></tt><br/>
|
|
</td>
|
|
<td class="left">
|
|
Packed vector of 4 integer values.<br/>
|
|
Packed vector of 8 floating-point values.<br/>
|
|
Packed vector of 2 unsigned integer values.<br/>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="t_opaque">Opaque Type</a> </div>
|
|
<div class="doc_text">
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>Opaque types are used to represent unknown types in the system. This
|
|
corresponds (for example) to the C notion of a foward declared structure type.
|
|
In LLVM, opaque types can eventually be resolved to any type (not just a
|
|
structure type).</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
|
|
<pre>
|
|
opaque
|
|
</pre>
|
|
|
|
<h5>Examples:</h5>
|
|
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left">
|
|
<tt>opaque</tt>
|
|
</td>
|
|
<td class="left">
|
|
An opaque type.<br/>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section"> <a name="constants">Constants</a> </div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM has several different basic types of constants. This section describes
|
|
them all and their syntax.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection"><a name="simpleconstants">Simple Constants</a></div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<dl>
|
|
<dt><b>Boolean constants</b></dt>
|
|
|
|
<dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid
|
|
constants of the <tt><a href="#t_primitive">bool</a></tt> type.
|
|
</dd>
|
|
|
|
<dt><b>Integer constants</b></dt>
|
|
|
|
<dd>Standard integers (such as '4') are constants of the <a
|
|
href="#t_integer">integer</a> type. Negative numbers may be used with signed
|
|
integer types.
|
|
</dd>
|
|
|
|
<dt><b>Floating point constants</b></dt>
|
|
|
|
<dd>Floating point constants use standard decimal notation (e.g. 123.421),
|
|
exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal
|
|
notation (see below). Floating point constants must have a <a
|
|
href="#t_floating">floating point</a> type. </dd>
|
|
|
|
<dt><b>Null pointer constants</b></dt>
|
|
|
|
<dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant
|
|
and must be of <a href="#t_pointer">pointer type</a>.</dd>
|
|
|
|
</dl>
|
|
|
|
<p>The one non-intuitive notation for constants is the optional hexadecimal form
|
|
of floating point constants. For example, the form '<tt>double
|
|
0x432ff973cafa8000</tt>' is equivalent to (but harder to read than) '<tt>double
|
|
4.5e+15</tt>'. The only time hexadecimal floating point constants are required
|
|
(and the only time that they are generated by the disassembler) is when a
|
|
floating point constant must be emitted but it cannot be represented as a
|
|
decimal floating point number. For example, NaN's, infinities, and other
|
|
special values are represented in their IEEE hexadecimal format so that
|
|
assembly and disassembly do not cause any bits to change in the constants.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection"><a name="aggregateconstants">Aggregate Constants</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>Aggregate constants arise from aggregation of simple constants
|
|
and smaller aggregate constants.</p>
|
|
|
|
<dl>
|
|
<dt><b>Structure constants</b></dt>
|
|
|
|
<dd>Structure constants are represented with notation similar to structure
|
|
type definitions (a comma separated list of elements, surrounded by braces
|
|
(<tt>{}</tt>)). For example: "<tt>{ int 4, float 17.0, int* %G }</tt>",
|
|
where "<tt>%G</tt>" is declared as "<tt>%G = external global int</tt>". Structure constants
|
|
must have <a href="#t_struct">structure type</a>, and the number and
|
|
types of elements must match those specified by the type.
|
|
</dd>
|
|
|
|
<dt><b>Array constants</b></dt>
|
|
|
|
<dd>Array constants are represented with notation similar to array type
|
|
definitions (a comma separated list of elements, surrounded by square brackets
|
|
(<tt>[]</tt>)). For example: "<tt>[ int 42, int 11, int 74 ]</tt>". Array
|
|
constants must have <a href="#t_array">array type</a>, and the number and
|
|
types of elements must match those specified by the type.
|
|
</dd>
|
|
|
|
<dt><b>Packed constants</b></dt>
|
|
|
|
<dd>Packed constants are represented with notation similar to packed type
|
|
definitions (a comma separated list of elements, surrounded by
|
|
less-than/greater-than's (<tt><></tt>)). For example: "<tt>< int 42,
|
|
int 11, int 74, int 100 ></tt>". Packed constants must have <a
|
|
href="#t_packed">packed type</a>, and the number and types of elements must
|
|
match those specified by the type.
|
|
</dd>
|
|
|
|
<dt><b>Zero initialization</b></dt>
|
|
|
|
<dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a
|
|
value to zero of <em>any</em> type, including scalar and aggregate types.
|
|
This is often used to avoid having to print large zero initializers (e.g. for
|
|
large arrays), and is always exactly equivalent to using explicit zero
|
|
initializers.
|
|
</dd>
|
|
</dl>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="globalconstants">Global Variable and Function Addresses</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The addresses of <a href="#globalvars">global variables</a> and <a
|
|
href="#functionstructure">functions</a> are always implicitly valid (link-time)
|
|
constants. These constants are explicitly referenced when the <a
|
|
href="#identifiers">identifier for the global</a> is used and always have <a
|
|
href="#t_pointer">pointer</a> type. For example, the following is a legal LLVM
|
|
file:</p>
|
|
|
|
<pre>
|
|
%X = global int 17
|
|
%Y = global int 42
|
|
%Z = global [2 x int*] [ int* %X, int* %Y ]
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection"><a name="undefvalues">Undefined Values</a></div>
|
|
<div class="doc_text">
|
|
<p>The string '<tt>undef</tt>' is recognized as a type-less constant that has
|
|
no specific value. Undefined values may be of any type and be used anywhere
|
|
a constant is permitted.</p>
|
|
|
|
<p>Undefined values indicate to the compiler that the program is well defined
|
|
no matter what value is used, giving the compiler more freedom to optimize.
|
|
</p>
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection"><a name="constantexprs">Constant Expressions</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>Constant expressions are used to allow expressions involving other constants
|
|
to be used as constants. Constant expressions may be of any <a
|
|
href="#t_firstclass">first class</a> type and may involve any LLVM operation
|
|
that does not have side effects (e.g. load and call are not supported). The
|
|
following is the syntax for constant expressions:</p>
|
|
|
|
<dl>
|
|
<dt><b><tt>cast ( CST to TYPE )</tt></b></dt>
|
|
|
|
<dd>Cast a constant to another type.</dd>
|
|
|
|
<dt><b><tt>getelementptr ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt>
|
|
|
|
<dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on
|
|
constants. As with the <a href="#i_getelementptr">getelementptr</a>
|
|
instruction, the index list may have zero or more indexes, which are required
|
|
to make sense for the type of "CSTPTR".</dd>
|
|
|
|
<dt><b><tt>OPCODE ( LHS, RHS )</tt></b></dt>
|
|
|
|
<dd>Perform the specified operation of the LHS and RHS constants. OPCODE may
|
|
be any of the <a href="#binaryops">binary</a> or <a href="#bitwiseops">bitwise
|
|
binary</a> operations. The constraints on operands are the same as those for
|
|
the corresponding instruction (e.g. no bitwise operations on floating point
|
|
values are allowed).</dd>
|
|
</dl>
|
|
</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="#bitwiseops">bitwise 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 six 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, the '<a
|
|
href="#i_unwind"><tt>unwind</tt></a>' instruction, and the '<a
|
|
href="#i_unreachable"><tt>unreachable</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>' instruction: 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 of the "normal" 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, control flow is
|
|
transfered to the corresponding destination; otherwise, control flow is
|
|
transfered to the default destination.</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, it could be generated 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 [<a href="#callingconv">cconv</a>] <ptr to function ty> %<function ptr val>(<function args>)
|
|
to label <normal label> except label <exception label>
|
|
</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>' label or the
|
|
'<tt>exception</tt>' label. 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 "exception" label.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>This instruction requires several arguments:</p>
|
|
|
|
<ol>
|
|
<li>
|
|
The optional "cconv" marker indicates which <a href="callingconv">calling
|
|
convention</a> the call should use. If none is specified, the call defaults
|
|
to using C calling conventions.
|
|
</li>
|
|
<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) to label %Continue
|
|
except label %TestCleanup <i>; {int}:retval set</i>
|
|
%retval = invoke <a href="#callingconv">coldcc</a> int %Test(int 15) to label %Continue
|
|
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
|
|
</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_subsubsection"> <a name="i_unreachable">'<tt>unreachable</tt>'
|
|
Instruction</a> </div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
unreachable
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>The '<tt>unreachable</tt>' instruction has no defined semantics. This
|
|
instruction is used to inform the optimizer that a particular portion of the
|
|
code is not reachable. This can be used to indicate that the code after a
|
|
no-return function cannot be reached, and other facts.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>The '<tt>unreachable</tt>' instruction has no defined semantics.</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 operands might represent
|
|
multiple data, as is the case with the <a href="#t_packed">packed</a> data type.
|
|
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.
|
|
This instruction can also take <a href="#t_packed">packed</a> versions of the 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.
|
|
This instruction can also take <a href="#t_packed">packed</a> versions of the 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.
|
|
This instruction can also take <a href="#t_packed">packed</a> versions of the 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.
|
|
This instruction can also take <a href="#t_packed">packed</a> versions of the 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.
|
|
This instruction can also take <a href="#t_packed">packed</a> versions of the values.
|
|
Both arguments must have identical types.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>This returns the <i>remainder</i> of a division (where the result
|
|
has the same sign as the divisor), not the <i>modulus</i> (where the
|
|
result has the same sign as the dividend) of a value. For more
|
|
information about the difference, see: <a
|
|
href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The
|
|
Math Forum</a>.</p>
|
|
<h5>Example:</h5>
|
|
<pre> <result> = rem int 4, %var <i>; yields {int}:result = 4 % %var</i>
|
|
</pre>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="i_setcc">'<tt>set<i>cc</i></tt>'
|
|
Instructions</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Syntax:</h5>
|
|
<pre> <result> = seteq <ty> <var1>, <var2> <i>; yields {bool}:result</i>
|
|
<result> = setne <ty> <var1>, <var2> <i>; yields {bool}:result</i>
|
|
<result> = setlt <ty> <var1>, <var2> <i>; yields {bool}:result</i>
|
|
<result> = setgt <ty> <var1>, <var2> <i>; yields {bool}:result</i>
|
|
<result> = setle <ty> <var1>, <var2> <i>; yields {bool}:result</i>
|
|
<result> = setge <ty> <var1>, <var2> <i>; yields {bool}:result</i>
|
|
</pre>
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>set<i>cc</i></tt>' family of instructions returns a boolean
|
|
value based on a comparison of their two operands.</p>
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>set<i>cc</i></tt>' instructions must
|
|
be of <a href="#t_firstclass">first class</a> type (it is not possible
|
|
to compare '<tt>label</tt>'s, '<tt>array</tt>'s, '<tt>structure</tt>'
|
|
or '<tt>void</tt>' values, etc...). Both arguments must have identical
|
|
types.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>seteq</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
|
|
value if both operands are equal.<br>
|
|
The '<tt>setne</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
|
|
value if both operands are unequal.<br>
|
|
The '<tt>setlt</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
|
|
value if the first operand is less than the second operand.<br>
|
|
The '<tt>setgt</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
|
|
value if the first operand is greater than the second operand.<br>
|
|
The '<tt>setle</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
|
|
value if the first operand is less than or equal to the second operand.<br>
|
|
The '<tt>setge</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>'
|
|
value if the first operand is greater than or equal to the second
|
|
operand.</p>
|
|
<h5>Example:</h5>
|
|
<pre> <result> = seteq int 4, 5 <i>; yields {bool}:result = false</i>
|
|
<result> = setne float 4, 5 <i>; yields {bool}:result = true</i>
|
|
<result> = setlt uint 4, 5 <i>; yields {bool}:result = true</i>
|
|
<result> = setgt sbyte 4, 5 <i>; yields {bool}:result = false</i>
|
|
<result> = setle sbyte 4, 5 <i>; yields {bool}:result = true</i>
|
|
<result> = setge sbyte 4, 5 <i>; yields {bool}:result = false</i>
|
|
</pre>
|
|
</div>
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection"> <a name="bitwiseops">Bitwise Binary
|
|
Operations</a> </div>
|
|
<div class="doc_text">
|
|
<p>Bitwise binary operators are used to do various forms of
|
|
bit-twiddling in a program. They are generally very efficient
|
|
instructions and can commonly be strength reduced from other
|
|
instructions. They require two operands, execute an operation on them,
|
|
and produce a single value. The resulting value of the bitwise binary
|
|
operators is always the same type as its first operand.</p>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="i_and">'<tt>and</tt>'
|
|
Instruction</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Syntax:</h5>
|
|
<pre> <result> = and <ty> <var1>, <var2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>and</tt>' instruction returns the bitwise logical and of
|
|
its two operands.</p>
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>and</tt>' instruction must be <a
|
|
href="#t_integral">integral</a> values. Both arguments must have
|
|
identical types.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>The truth table used for the '<tt>and</tt>' instruction is:</p>
|
|
<p> </p>
|
|
<div style="align: center">
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<tbody>
|
|
<tr>
|
|
<td>In0</td>
|
|
<td>In1</td>
|
|
<td>Out</td>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<h5>Example:</h5>
|
|
<pre> <result> = and int 4, %var <i>; yields {int}:result = 4 & %var</i>
|
|
<result> = and int 15, 40 <i>; yields {int}:result = 8</i>
|
|
<result> = and int 4, 8 <i>; yields {int}:result = 0</i>
|
|
</pre>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="i_or">'<tt>or</tt>' Instruction</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Syntax:</h5>
|
|
<pre> <result> = or <ty> <var1>, <var2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive
|
|
or of its two operands.</p>
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>or</tt>' instruction must be <a
|
|
href="#t_integral">integral</a> values. Both arguments must have
|
|
identical types.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>The truth table used for the '<tt>or</tt>' instruction is:</p>
|
|
<p> </p>
|
|
<div style="align: center">
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<tbody>
|
|
<tr>
|
|
<td>In0</td>
|
|
<td>In1</td>
|
|
<td>Out</td>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<h5>Example:</h5>
|
|
<pre> <result> = or int 4, %var <i>; yields {int}:result = 4 | %var</i>
|
|
<result> = or int 15, 40 <i>; yields {int}:result = 47</i>
|
|
<result> = or int 4, 8 <i>; yields {int}:result = 12</i>
|
|
</pre>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="i_xor">'<tt>xor</tt>'
|
|
Instruction</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Syntax:</h5>
|
|
<pre> <result> = xor <ty> <var1>, <var2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive
|
|
or of its two operands. The <tt>xor</tt> is used to implement the
|
|
"one's complement" operation, which is the "~" operator in C.</p>
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>xor</tt>' instruction must be <a
|
|
href="#t_integral">integral</a> values. Both arguments must have
|
|
identical types.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>The truth table used for the '<tt>xor</tt>' instruction is:</p>
|
|
<p> </p>
|
|
<div style="align: center">
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<tbody>
|
|
<tr>
|
|
<td>In0</td>
|
|
<td>In1</td>
|
|
<td>Out</td>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<p> </p>
|
|
<h5>Example:</h5>
|
|
<pre> <result> = xor int 4, %var <i>; yields {int}:result = 4 ^ %var</i>
|
|
<result> = xor int 15, 40 <i>; yields {int}:result = 39</i>
|
|
<result> = xor int 4, 8 <i>; yields {int}:result = 12</i>
|
|
<result> = xor int %V, -1 <i>; yields {int}:result = ~%V</i>
|
|
</pre>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="i_shl">'<tt>shl</tt>'
|
|
Instruction</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Syntax:</h5>
|
|
<pre> <result> = shl <ty> <var1>, ubyte <var2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>shl</tt>' instruction returns the first operand shifted to
|
|
the left a specified number of bits.</p>
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument to the '<tt>shl</tt>' instruction must be an <a
|
|
href="#t_integer">integer</a> type. The second argument must be an '<tt>ubyte</tt>'
|
|
type.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is <tt>var1</tt> * 2<sup><tt>var2</tt></sup>.</p>
|
|
<h5>Example:</h5>
|
|
<pre> <result> = shl int 4, ubyte %var <i>; yields {int}:result = 4 << %var</i>
|
|
<result> = shl int 4, ubyte 2 <i>; yields {int}:result = 16</i>
|
|
<result> = shl int 1, ubyte 10 <i>; yields {int}:result = 1024</i>
|
|
</pre>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="i_shr">'<tt>shr</tt>'
|
|
Instruction</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Syntax:</h5>
|
|
<pre> <result> = shr <ty> <var1>, ubyte <var2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>shr</tt>' instruction returns the first operand shifted to
|
|
the right a specified number of bits.</p>
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument to the '<tt>shr</tt>' instruction must be an <a
|
|
href="#t_integer">integer</a> type. The second argument must be an '<tt>ubyte</tt>'
|
|
type.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>If the first argument is a <a href="#t_signed">signed</a> type, the
|
|
most significant bit is duplicated in the newly free'd bit positions.
|
|
If the first argument is unsigned, zero bits shall fill the empty
|
|
positions.</p>
|
|
<h5>Example:</h5>
|
|
<pre> <result> = shr int 4, ubyte %var <i>; yields {int}:result = 4 >> %var</i>
|
|
<result> = shr uint 4, ubyte 1 <i>; yields {uint}:result = 2</i>
|
|
<result> = shr int 4, ubyte 2 <i>; yields {int}:result = 1</i>
|
|
<result> = shr sbyte 4, ubyte 3 <i>; yields {sbyte}:result = 0</i>
|
|
<result> = shr sbyte -2, ubyte 1 <i>; yields {sbyte}:result = -1</i>
|
|
</pre>
|
|
</div>
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection"> <a name="memoryops">Memory Access
|
|
Operations</a></div>
|
|
<div class="doc_text">
|
|
<p>A key design point of an SSA-based representation is how it
|
|
represents memory. In LLVM, no memory locations are in SSA form, which
|
|
makes things very simple. This section describes how to read, write,
|
|
allocate, and free memory in LLVM.</p>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="i_malloc">'<tt>malloc</tt>'
|
|
Instruction</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Syntax:</h5>
|
|
<pre> <result> = malloc <type>, uint <NumElements> <i>; yields {type*}:result</i>
|
|
<result> = malloc <type> <i>; yields {type*}:result</i>
|
|
</pre>
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>malloc</tt>' instruction allocates memory from the system
|
|
heap and returns a pointer to it.</p>
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>malloc</tt>' instruction allocates <tt>sizeof(<type>)*NumElements</tt>
|
|
bytes of memory from the operating system and returns a pointer of the
|
|
appropriate type to the program. The second form of the instruction is
|
|
a shorter version of the first instruction that defaults to allocating
|
|
one element.</p>
|
|
<p>'<tt>type</tt>' must be a sized type.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>Memory is allocated using the system "<tt>malloc</tt>" function, and
|
|
a pointer is returned.</p>
|
|
<h5>Example:</h5>
|
|
<pre> %array = malloc [4 x ubyte ] <i>; yields {[%4 x ubyte]*}:array</i>
|
|
|
|
%size = <a
|
|
href="#i_add">add</a> uint 2, 2 <i>; yields {uint}:size = uint 4</i>
|
|
%array1 = malloc ubyte, uint 4 <i>; yields {ubyte*}:array1</i>
|
|
%array2 = malloc [12 x ubyte], uint %size <i>; yields {[12 x ubyte]*}:array2</i>
|
|
</pre>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="i_free">'<tt>free</tt>'
|
|
Instruction</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Syntax:</h5>
|
|
<pre> free <type> <value> <i>; yields {void}</i>
|
|
</pre>
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>free</tt>' instruction returns memory back to the unused
|
|
memory heap to be reallocated in the future.</p>
|
|
<p> </p>
|
|
<h5>Arguments:</h5>
|
|
<p>'<tt>value</tt>' shall be a pointer value that points to a value
|
|
that was allocated with the '<tt><a href="#i_malloc">malloc</a></tt>'
|
|
instruction.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>Access to the memory pointed to by the pointer is no 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 '<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_unwind">unwind</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>{, <ty> <idx>}*
|
|
</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 integer constants that indicate what
|
|
elements of the aggregate object to index to. 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 or to a specific index in an array. When indexing into a
|
|
structure, only <tt>uint</tt>
|
|
integer constants are allowed. When indexing into an array or pointer,
|
|
<tt>int</tt> and <tt>long</tt> indexes are allowed of any sign.</p>
|
|
|
|
<p>For example, let's consider a C code fragment and how it gets
|
|
compiled to LLVM:</p>
|
|
|
|
<pre>
|
|
struct RT {
|
|
char A;
|
|
int B[10][20];
|
|
char C;
|
|
};
|
|
struct ST {
|
|
int X;
|
|
double Y;
|
|
struct RT Z;
|
|
};
|
|
|
|
int *foo(struct ST *s) {
|
|
return &s[1].Z.B[5][13];
|
|
}
|
|
</pre>
|
|
|
|
<p>The LLVM code generated by the GCC frontend is:</p>
|
|
|
|
<pre>
|
|
%RT = type { sbyte, [10 x [20 x int]], sbyte }
|
|
%ST = type { int, double, %RT }
|
|
|
|
implementation
|
|
|
|
int* %foo(%ST* %s) {
|
|
entry:
|
|
%reg = getelementptr %ST* %s, int 1, uint 2, uint 1, int 5, int 13
|
|
ret int* %reg
|
|
}
|
|
</pre>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>The index types specified for the '<tt>getelementptr</tt>' instruction depend
|
|
on the pointer type that is being indexed into. <a href="#t_pointer">Pointer</a>
|
|
and <a href="#t_array">array</a> types require <tt>uint</tt>, <tt>int</tt>,
|
|
<tt>ulong</tt>, or <tt>long</tt> values, and <a href="#t_struct">structure</a>
|
|
types require <tt>uint</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 returns a pointer
|
|
to this element, thus computing a value of '<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) {
|
|
%t1 = getelementptr %ST* %s, int 1 <i>; yields %ST*:%t1</i>
|
|
%t2 = getelementptr %ST* %t1, int 0, uint 2 <i>; yields %RT*:%t2</i>
|
|
%t3 = getelementptr %RT* %t2, int 0, uint 1 <i>; yields [10 x [20 x int]]*:%t3</i>
|
|
%t4 = getelementptr [10 x [20 x int]]* %t3, int 0, int 5 <i>; yields [20 x int]*:%t4</i>
|
|
%t5 = getelementptr [20 x int]* %t4, int 0, int 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, uint 1
|
|
</pre>
|
|
|
|
</div>
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection"> <a name="otherops">Other Operations</a> </div>
|
|
<div class="doc_text">
|
|
<p>The instructions in this category are the "miscellaneous"
|
|
instructions, which defy better classification.</p>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection"> <a name="i_phi">'<tt>phi</tt>'
|
|
Instruction</a> </div>
|
|
<div class="doc_text">
|
|
<h5>Syntax:</h5>
|
|
<pre> <result> = phi <ty> [ <val0>, <label0>], ...<br></pre>
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>phi</tt>' instruction is used to implement the φ node in
|
|
the SSA graph representing the function.</p>
|
|
<h5>Arguments:</h5>
|
|
<p>The type of the incoming values are specified with the first type
|
|
field. After this, the '<tt>phi</tt>' instruction takes a list of pairs
|
|
as arguments, with one pair for each predecessor basic block of the
|
|
current block. Only values of <a href="#t_firstclass">first class</a>
|
|
type may be used as the value arguments to the PHI node. Only labels
|
|
may be used as the label arguments.</p>
|
|
<p>There must be no non-phi instructions between the start of a basic
|
|
block and the PHI instructions: i.e. PHI instructions must be first in
|
|
a basic block.</p>
|
|
<h5>Semantics:</h5>
|
|
<p>At runtime, the '<tt>phi</tt>' instruction logically takes on the
|
|
value specified by the parameter, depending on which basic block we
|
|
came from in the last <a href="#terminators">terminator</a> instruction.</p>
|
|
<h5>Example:</h5>
|
|
<pre>Loop: ; Infinite loop that counts from 0 on up...<br> %indvar = phi uint [ 0, %LoopHeader ], [ %nextindvar, %Loop ]<br> %nextindvar = add uint %indvar, 1<br> br label %Loop<br></pre>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_cast">'<tt>cast .. to</tt>' Instruction</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
|
|
<pre>
|
|
<result> = cast <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>cast</tt>' instruction is used as the primitive means to convert
|
|
integers to floating point, change data type sizes, and break type safety (by
|
|
casting pointers).
|
|
</p>
|
|
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The '<tt>cast</tt>' instruction takes a value to cast, which must be a first
|
|
class value, and a type to cast it to, which must also be a <a
|
|
href="#t_firstclass">first class</a> type.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
This instruction follows the C rules for explicit casts when determining how the
|
|
data being cast must change to fit in its new container.
|
|
</p>
|
|
|
|
<p>
|
|
When casting to bool, any value that would be considered true in the context of
|
|
a C '<tt>if</tt>' condition is converted to the boolean '<tt>true</tt>' values,
|
|
all else are '<tt>false</tt>'.
|
|
</p>
|
|
|
|
<p>
|
|
When extending an integral value from a type of one signness to another (for
|
|
example '<tt>sbyte</tt>' to '<tt>ulong</tt>'), the value is sign-extended if the
|
|
<b>source</b> value is signed, and zero-extended if the source value is
|
|
unsigned. <tt>bool</tt> values are always zero extended into either zero or
|
|
one.
|
|
</p>
|
|
|
|
<h5>Example:</h5>
|
|
|
|
<pre>
|
|
%X = cast int 257 to ubyte <i>; yields ubyte:1</i>
|
|
%Y = cast int 123 to bool <i>; yields bool:true</i>
|
|
</pre>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_select">'<tt>select</tt>' Instruction</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
|
|
<pre>
|
|
<result> = select bool <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>select</tt>' instruction is used to choose one value based on a
|
|
condition, without branching.
|
|
</p>
|
|
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The '<tt>select</tt>' instruction requires a boolean value indicating the condition, and two values of the same <a href="#t_firstclass">first class</a> type.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
If the boolean condition evaluates to true, the instruction returns the first
|
|
value argument; otherwise, it returns the second value argument.
|
|
</p>
|
|
|
|
<h5>Example:</h5>
|
|
|
|
<pre>
|
|
%X = select bool true, ubyte 17, ubyte 42 <i>; yields ubyte:17</i>
|
|
</pre>
|
|
</div>
|
|
|
|
|
|
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_call">'<tt>call</tt>' Instruction</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = [tail] call [<a href="#callingconv">cconv</a>] <ty>* <fnptrval>(<param list>)
|
|
</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>The optional "tail" marker indicates whether the callee function accesses
|
|
any allocas or varargs in the caller. If the "tail" marker is present, the
|
|
function call is eligible for tail call optimization. Note that calls may
|
|
be marked "tail" even if they do not occur before a <a
|
|
href="#i_ret"><tt>ret</tt></a> instruction.
|
|
</li>
|
|
<li>
|
|
<p>The optional "cconv" marker indicates which <a href="callingconv">calling
|
|
convention</a> the call should use. If none is specified, the call defaults
|
|
to using C calling conventions.
|
|
</li>
|
|
<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. This type can be omitted if the function is not varargs and
|
|
if the function type does not return a pointer to a function.</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 value.</p>
|
|
</li>
|
|
<li>
|
|
<p>'<tt>function args</tt>': argument list whose types match the
|
|
function signature argument types. All arguments must be of
|
|
<a href="#t_firstclass">first class</a> type. 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)
|
|
call int(sbyte*, ...) *%printf(sbyte* %msg, int 12, sbyte 42);
|
|
%X = tail call int %foo()
|
|
%Y = tail call <a href="#callingconv">fastcc</a> int %foo()
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_vaarg">'<tt>vaarg</tt>' Instruction</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
|
|
<pre>
|
|
<resultval> = va_arg <va_list*> <arglist>, <argty>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>The '<tt>va_arg</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>va_list*</tt> value and the type of
|
|
the argument. It returns a value of the specified argument type and
|
|
increments the <tt>va_list</tt> to poin to the next argument. Again, the
|
|
actual type of <tt>va_list</tt> is target specific.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>The '<tt>va_arg</tt>' instruction loads an argument of the specified
|
|
type from the specified <tt>va_list</tt> and causes the
|
|
<tt>va_list</tt> to point to the next argument. 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>va_arg</tt> is an LLVM instruction instead of an <a
|
|
href="#intrinsics">intrinsic function</a> because it takes a 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>To learn how to add an intrinsic function, please see the <a
|
|
href="ExtendingLLVM.html">Extending LLVM Guide</a>.
|
|
</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 = alloca sbyte*
|
|
call void %<a href="#i_va_start">llvm.va_start</a>(sbyte** %ap)
|
|
|
|
; Read a single integer argument
|
|
%tmp = va_arg sbyte** %ap, int
|
|
|
|
; Demonstrate usage of llvm.va_copy and llvm.va_end
|
|
%aq = alloca sbyte*
|
|
%apv = load sbyte** %ap
|
|
call void %<a href="#i_va_copy">llvm.va_copy</a>(sbyte** %aq, sbyte* %apv)
|
|
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** %ap)
|
|
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> declare void %llvm.va_start(<va_list>* <arglist>)<br></pre>
|
|
<h5>Overview:</h5>
|
|
<P>The '<tt>llvm.va_start</tt>' intrinsic initializes
|
|
<tt>*<arglist></tt> for subsequent use by <tt><a
|
|
href="#i_va_arg">va_arg</a></tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<P>The argument is a pointer to a <tt>va_list</tt> element to initialize.</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 the
|
|
<tt>va_list</tt> element the argument points to, so that the next call to
|
|
<tt>va_arg</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>
|
|
|
|
</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> declare void %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>
|
|
declare void %llvm.va_copy(<va_list>* <destarglist>,
|
|
<va_list> <srcarglist>)
|
|
</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 first argument is a pointer to a <tt>va_list</tt> element to initialize.
|
|
The second argument is a <tt>va_list</tt> element to copy from.</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 destination list. This intrinsic is necessary
|
|
because the <tt><a href="i_va_begin">llvm.va_begin</a></tt> intrinsic may be
|
|
arbitrarily complex and require memory allocation, for example.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="int_gc">Accurate Garbage Collection Intrinsics</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>
|
|
LLVM support for <a href="GarbageCollection.html">Accurate Garbage
|
|
Collection</a> requires the implementation and generation of these intrinsics.
|
|
These intrinsics allow identification of <a href="#i_gcroot">GC roots on the
|
|
stack</a>, as well as garbage collector implementations that require <a
|
|
href="#i_gcread">read</a> and <a href="#i_gcwrite">write</a> barriers.
|
|
Front-ends for type-safe garbage collected languages should generate these
|
|
intrinsics to make use of the LLVM garbage collectors. For more details, see <a
|
|
href="GarbageCollection.html">Accurate Garbage Collection with LLVM</a>.
|
|
</p>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
|
|
<pre>
|
|
declare void %llvm.gcroot(<ty>** %ptrloc, <ty2>* %metadata)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to
|
|
the code generator, and allows some metadata to be associated with it.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>The first argument specifies the address of a stack object that contains the
|
|
root pointer. The second pointer (which must be either a constant or a global
|
|
value address) contains the meta-data to be associated with the root.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>At runtime, a call to this intrinsics stores a null pointer into the "ptrloc"
|
|
location. At compile-time, the code generator generates information to allow
|
|
the runtime to find the pointer at GC safe points.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
|
|
<pre>
|
|
declare sbyte* %llvm.gcread(sbyte** %Ptr)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap
|
|
locations, allowing garbage collector implementations that require read
|
|
barriers.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>The argument is the address to read from, which should be an address
|
|
allocated from the garbage collector.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load
|
|
instruction, but may be replaced with substantially more complex code by the
|
|
garbage collector runtime, as needed.</p>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
|
|
<pre>
|
|
declare void %llvm.gcwrite(sbyte* %P1, sbyte** %P2)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap
|
|
locations, allowing garbage collector implementations that require write
|
|
barriers (such as generational or reference counting collectors).</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>The first argument is the reference to store, and the second is the heap
|
|
location to store to.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store
|
|
instruction, but may be replaced with substantially more complex code by the
|
|
garbage collector runtime, as needed.</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>
|
|
declare 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 be 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>
|
|
declare 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 be that of the obvious
|
|
source-language caller.
|
|
</p>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void %llvm.prefetch(sbyte * <address>,
|
|
uint <rw>, uint <locality>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
|
|
<p>
|
|
The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to insert
|
|
a prefetch instruction if supported; otherwise, it is a noop. Prefetches have
|
|
no
|
|
effect on the behavior of the program but can change its performance
|
|
characteristics.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
<tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the specifier
|
|
determining if the fetch should be for a read (0) or write (1), and
|
|
<tt>locality</tt> is a temporal locality specifier ranging from (0) - no
|
|
locality, to (3) - extremely local keep in cache. The <tt>rw</tt> and
|
|
<tt>locality</tt> arguments must be constant integers.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
This intrinsic does not modify the behavior of the program. In particular,
|
|
prefetches cannot trap and do not produce a value. On targets that support this
|
|
intrinsic, the prefetch can provide hints to the processor cache for better
|
|
performance.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void %llvm.pcmarker( uint <id> )
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
|
|
<p>
|
|
The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program Counter
|
|
(PC) in a region of
|
|
code to simulators and other tools. The method is target specific, but it is
|
|
expected that the marker will use exported symbols to transmit the PC of the marker.
|
|
The marker makes no guaranties that it will remain with any specific instruction
|
|
after optimizations. It is possible that the presense of a marker will inhibit
|
|
optimizations. The intended use is to be inserted after optmizations to allow
|
|
correlations of simulation runs.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
<tt>id</tt> is a numerical id identifying the marker.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
This intrinsic does not modify the behavior of the program. Backends that do not
|
|
support this intrinisic may ignore it.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="int_os">Operating System Intrinsics</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
These intrinsics are provided by LLVM to support the implementation of
|
|
operating system level code.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_readport">'<tt>llvm.readport</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare <integer type> %llvm.readport (<integer type> <address>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.readport</tt>' intrinsic reads data from the specified hardware
|
|
I/O port.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The argument to this intrinsic indicates the hardware I/O address from which
|
|
to read the data. The address is in the hardware I/O address namespace (as
|
|
opposed to being a memory location for memory mapped I/O).
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.readport</tt>' intrinsic reads data from the hardware I/O port
|
|
specified by <i>address</i> and returns the value. The address and return
|
|
value must be integers, but the size is dependent upon the platform upon which
|
|
the program is code generated. For example, on x86, the address must be an
|
|
unsigned 16-bit value, and the return value must be 8, 16, or 32 bits.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_writeport">'<tt>llvm.writeport</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
call void (<integer type>, <integer type>)*
|
|
%llvm.writeport (<integer type> <value>,
|
|
<integer type> <address>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.writeport</tt>' intrinsic writes data to the specified hardware
|
|
I/O port.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The first argument is the value to write to the I/O port.
|
|
</p>
|
|
|
|
<p>
|
|
The second argument indicates the hardware I/O address to which data should be
|
|
written. The address is in the hardware I/O address namespace (as opposed to
|
|
being a memory location for memory mapped I/O).
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.writeport</tt>' intrinsic writes <i>value</i> to the I/O port
|
|
specified by <i>address</i>. The address and value must be integers, but the
|
|
size is dependent upon the platform upon which the program is code generated.
|
|
For example, on x86, the address must be an unsigned 16-bit value, and the
|
|
value written must be 8, 16, or 32 bits in length.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_readio">'<tt>llvm.readio</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare <result> %llvm.readio (<ty> * <pointer>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.readio</tt>' intrinsic reads data from a memory mapped I/O
|
|
address.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The argument to this intrinsic is a pointer indicating the memory address from
|
|
which to read the data. The data must be a
|
|
<a href="#t_firstclass">first class</a> type.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.readio</tt>' intrinsic reads data from a memory mapped I/O
|
|
location specified by <i>pointer</i> and returns the value. The argument must
|
|
be a pointer, and the return value must be a
|
|
<a href="#t_firstclass">first class</a> type. However, certain architectures
|
|
may not support I/O on all first class types. For example, 32-bit processors
|
|
may only support I/O on data types that are 32 bits or less.
|
|
</p>
|
|
|
|
<p>
|
|
This intrinsic enforces an in-order memory model for llvm.readio and
|
|
llvm.writeio calls on machines that use dynamic scheduling. Dynamically
|
|
scheduled processors may execute loads and stores out of order, re-ordering at
|
|
run time accesses to memory mapped I/O registers. Using these intrinsics
|
|
ensures that accesses to memory mapped I/O registers occur in program order.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="i_writeio">'<tt>llvm.writeio</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void %llvm.writeio (<ty1> <value>, <ty2> * <pointer>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.writeio</tt>' intrinsic writes data to the specified memory
|
|
mapped I/O address.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The first argument is the value to write to the memory mapped I/O location.
|
|
The second argument is a pointer indicating the memory address to which the
|
|
data should be written.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.writeio</tt>' intrinsic writes <i>value</i> to the memory mapped
|
|
I/O address specified by <i>pointer</i>. The value must be a
|
|
<a href="#t_firstclass">first class</a> type. However, certain architectures
|
|
may not support I/O on all first class types. For example, 32-bit processors
|
|
may only support I/O on data types that are 32 bits or less.
|
|
</p>
|
|
|
|
<p>
|
|
This intrinsic enforces an in-order memory model for llvm.readio and
|
|
llvm.writeio calls on machines that use dynamic scheduling. Dynamically
|
|
scheduled processors may execute loads and stores out of order, re-ordering at
|
|
run time accesses to memory mapped I/O registers. Using these intrinsics
|
|
ensures that accesses to memory mapped I/O registers occur in program order.
|
|
</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>
|
|
declare void %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>
|
|
declare void %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>
|
|
declare void %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_subsubsection">
|
|
<a name="i_isunordered">'<tt>llvm.isunordered</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare bool %llvm.isunordered(<float or double> Val1, <float or double> Val2)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.isunordered</tt>' intrinsic returns true if either or both of the
|
|
specified floating point values is a NAN.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The arguments are floating point numbers of the same type.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
If either or both of the arguments is a SNAN or QNAN, it returns true, otherwise
|
|
false.
|
|
</p>
|
|
</div>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="int_count">Bit Counting Intrinsics</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
LLVM provides intrinsics for a few important bit counting operations.
|
|
These allow efficient code generation for some algorithms.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="int_ctpop">'<tt>llvm.ctpop</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare int %llvm.ctpop(int <src>)
|
|
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.ctpop</tt>' intrinsic counts the number of ones in a variable.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The only argument is the value to be counted. The argument may be of any
|
|
integer type. The return type must match the argument type.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable.
|
|
</p>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="int_ctlz">'<tt>llvm.ctlz</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare int %llvm.ctlz(int <src>)
|
|
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.ctlz</tt>' intrinsic counts the number of leading zeros in a
|
|
variable.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The only argument is the value to be counted. The argument may be of any
|
|
integer type. The return type must match the argument type.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant) zeros
|
|
in a variable. If the src == 0 then the result is the size in bits of the type
|
|
of src. For example, <tt>llvm.cttz(int 2) = 30</tt>.
|
|
</p>
|
|
</div>
|
|
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<div class="doc_subsubsection">
|
|
<a name="int_cttz">'<tt>llvm.cttz</tt>' Intrinsic</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare int %llvm.cttz(int <src>)
|
|
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.cttz</tt>' intrinsic counts the number of trailing zeros.
|
|
</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>
|
|
The only argument is the value to be counted. The argument may be of any
|
|
integer type. The return type must match the argument type.
|
|
</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>
|
|
The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant) zeros
|
|
in a variable. If the src == 0 then the result is the size in bits of the type
|
|
of src. For example, <tt>llvm.cttz(2) = 1</tt>.
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</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="int_debugger">Debugger Intrinsics</a>
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</div>
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<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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<address>
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src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
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<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
|
|
<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
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Last modified: $Date$
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</address>
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</body>
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</html>
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