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| <title>LLVM Assembly Language Reference Manual</title> | |
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| <meta name="author" content="Chris Lattner"> | |
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| <body> | |
| <div class="doc_title"> LLVM Language Reference Manual </div> | |
| <ol> | |
| <li><a href="#abstract">Abstract</a></li> | |
| <li><a href="#introduction">Introduction</a></li> | |
| <li><a href="#identifiers">Identifiers</a></li> | |
| <li><a href="#highlevel">High Level Structure</a> | |
| <ol> | |
| <li><a href="#modulestructure">Module Structure</a></li> | |
| <li><a href="#linkage">Linkage Types</a> | |
| <ol> | |
| <li><a href="#linkage_private">'<tt>private</tt>' Linkage</a></li> | |
| <li><a href="#linkage_linker_private">'<tt>linker_private</tt>' Linkage</a></li> | |
| <li><a href="#linkage_internal">'<tt>internal</tt>' Linkage</a></li> | |
| <li><a href="#linkage_available_externally">'<tt>available_externally</tt>' Linkage</a></li> | |
| <li><a href="#linkage_linkonce">'<tt>linkonce</tt>' Linkage</a></li> | |
| <li><a href="#linkage_common">'<tt>common</tt>' Linkage</a></li> | |
| <li><a href="#linkage_weak">'<tt>weak</tt>' Linkage</a></li> | |
| <li><a href="#linkage_appending">'<tt>appending</tt>' Linkage</a></li> | |
| <li><a href="#linkage_externweak">'<tt>extern_weak</tt>' Linkage</a></li> | |
| <li><a href="#linkage_linkonce">'<tt>linkonce_odr</tt>' Linkage</a></li> | |
| <li><a href="#linkage_weak">'<tt>weak_odr</tt>' Linkage</a></li> | |
| <li><a href="#linkage_external">'<tt>externally visible</tt>' Linkage</a></li> | |
| <li><a href="#linkage_dllimport">'<tt>dllimport</tt>' Linkage</a></li> | |
| <li><a href="#linkage_dllexport">'<tt>dllexport</tt>' Linkage</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#callingconv">Calling Conventions</a></li> | |
| <li><a href="#namedtypes">Named Types</a></li> | |
| <li><a href="#globalvars">Global Variables</a></li> | |
| <li><a href="#functionstructure">Functions</a></li> | |
| <li><a href="#aliasstructure">Aliases</a></li> | |
| <li><a href="#paramattrs">Parameter Attributes</a></li> | |
| <li><a href="#fnattrs">Function Attributes</a></li> | |
| <li><a href="#gc">Garbage Collector Names</a></li> | |
| <li><a href="#moduleasm">Module-Level Inline Assembly</a></li> | |
| <li><a href="#datalayout">Data Layout</a></li> | |
| <li><a href="#pointeraliasing">Pointer Aliasing Rules</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#typesystem">Type System</a> | |
| <ol> | |
| <li><a href="#t_classifications">Type Classifications</a></li> | |
| <li><a href="#t_primitive">Primitive Types</a> | |
| <ol> | |
| <li><a href="#t_floating">Floating Point Types</a></li> | |
| <li><a href="#t_void">Void Type</a></li> | |
| <li><a href="#t_label">Label Type</a></li> | |
| <li><a href="#t_metadata">Metadata Type</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#t_derived">Derived Types</a> | |
| <ol> | |
| <li><a href="#t_integer">Integer Type</a></li> | |
| <li><a href="#t_array">Array Type</a></li> | |
| <li><a href="#t_function">Function Type</a></li> | |
| <li><a href="#t_pointer">Pointer Type</a></li> | |
| <li><a href="#t_struct">Structure Type</a></li> | |
| <li><a href="#t_pstruct">Packed Structure Type</a></li> | |
| <li><a href="#t_vector">Vector Type</a></li> | |
| <li><a href="#t_opaque">Opaque Type</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#t_uprefs">Type Up-references</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#constants">Constants</a> | |
| <ol> | |
| <li><a href="#simpleconstants">Simple Constants</a></li> | |
| <li><a href="#complexconstants">Complex Constants</a></li> | |
| <li><a href="#globalconstants">Global Variable and Function Addresses</a></li> | |
| <li><a href="#undefvalues">Undefined Values</a></li> | |
| <li><a href="#constantexprs">Constant Expressions</a></li> | |
| <li><a href="#metadata">Embedded Metadata</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#othervalues">Other Values</a> | |
| <ol> | |
| <li><a href="#inlineasm">Inline Assembler Expressions</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#intrinsic_globals">Intrinsic Global Variables</a> | |
| <ol> | |
| <li><a href="#intg_used">The '<tt>llvm.used</tt>' Global Variable</a></li> | |
| <li><a href="#intg_compiler_used">The '<tt>llvm.compiler.used</tt>' | |
| Global Variable</a></li> | |
| <li><a href="#intg_global_ctors">The '<tt>llvm.global_ctors</tt>' | |
| Global Variable</a></li> | |
| <li><a href="#intg_global_dtors">The '<tt>llvm.global_dtors</tt>' | |
| Global Variable</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#instref">Instruction Reference</a> | |
| <ol> | |
| <li><a href="#terminators">Terminator Instructions</a> | |
| <ol> | |
| <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li> | |
| <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li> | |
| <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li> | |
| <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li> | |
| <li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li> | |
| <li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#binaryops">Binary Operations</a> | |
| <ol> | |
| <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li> | |
| <li><a href="#i_fadd">'<tt>fadd</tt>' Instruction</a></li> | |
| <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li> | |
| <li><a href="#i_fsub">'<tt>fsub</tt>' Instruction</a></li> | |
| <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li> | |
| <li><a href="#i_fmul">'<tt>fmul</tt>' Instruction</a></li> | |
| <li><a href="#i_udiv">'<tt>udiv</tt>' Instruction</a></li> | |
| <li><a href="#i_sdiv">'<tt>sdiv</tt>' Instruction</a></li> | |
| <li><a href="#i_fdiv">'<tt>fdiv</tt>' Instruction</a></li> | |
| <li><a href="#i_urem">'<tt>urem</tt>' Instruction</a></li> | |
| <li><a href="#i_srem">'<tt>srem</tt>' Instruction</a></li> | |
| <li><a href="#i_frem">'<tt>frem</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#bitwiseops">Bitwise Binary Operations</a> | |
| <ol> | |
| <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li> | |
| <li><a href="#i_lshr">'<tt>lshr</tt>' Instruction</a></li> | |
| <li><a href="#i_ashr">'<tt>ashr</tt>' Instruction</a></li> | |
| <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li> | |
| <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li> | |
| <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#vectorops">Vector Operations</a> | |
| <ol> | |
| <li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li> | |
| <li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li> | |
| <li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#aggregateops">Aggregate Operations</a> | |
| <ol> | |
| <li><a href="#i_extractvalue">'<tt>extractvalue</tt>' Instruction</a></li> | |
| <li><a href="#i_insertvalue">'<tt>insertvalue</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#memoryops">Memory Access and Addressing Operations</a> | |
| <ol> | |
| <li><a href="#i_malloc">'<tt>malloc</tt>' Instruction</a></li> | |
| <li><a href="#i_free">'<tt>free</tt>' Instruction</a></li> | |
| <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li> | |
| <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li> | |
| <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li> | |
| <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#convertops">Conversion Operations</a> | |
| <ol> | |
| <li><a href="#i_trunc">'<tt>trunc .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_zext">'<tt>zext .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_sext">'<tt>sext .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_fpext">'<tt>fpext .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#otherops">Other Operations</a> | |
| <ol> | |
| <li><a href="#i_icmp">'<tt>icmp</tt>' Instruction</a></li> | |
| <li><a href="#i_fcmp">'<tt>fcmp</tt>' Instruction</a></li> | |
| <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li> | |
| <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li> | |
| <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li> | |
| <li><a href="#i_va_arg">'<tt>va_arg</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| </ol> | |
| </li> | |
| <li><a href="#intrinsics">Intrinsic Functions</a> | |
| <ol> | |
| <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a> | |
| <ol> | |
| <li><a href="#int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li> | |
| <li><a href="#int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li> | |
| <li><a href="#int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a> | |
| <ol> | |
| <li><a href="#int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li> | |
| <li><a href="#int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li> | |
| <li><a href="#int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_codegen">Code Generator Intrinsics</a> | |
| <ol> | |
| <li><a href="#int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li> | |
| <li><a href="#int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li> | |
| <li><a href="#int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li> | |
| <li><a href="#int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a></li> | |
| <li><a href="#int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li> | |
| <li><a href="#int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li> | |
| <li><a href="#int_readcyclecounter"><tt>llvm.readcyclecounter</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_libc">Standard C Library Intrinsics</a> | |
| <ol> | |
| <li><a href="#int_memcpy">'<tt>llvm.memcpy.*</tt>' Intrinsic</a></li> | |
| <li><a href="#int_memmove">'<tt>llvm.memmove.*</tt>' Intrinsic</a></li> | |
| <li><a href="#int_memset">'<tt>llvm.memset.*</tt>' Intrinsic</a></li> | |
| <li><a href="#int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a></li> | |
| <li><a href="#int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a></li> | |
| <li><a href="#int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a></li> | |
| <li><a href="#int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a></li> | |
| <li><a href="#int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_manip">Bit Manipulation Intrinsics</a> | |
| <ol> | |
| <li><a href="#int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li> | |
| <li><a href="#int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic </a></li> | |
| <li><a href="#int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic </a></li> | |
| <li><a href="#int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic </a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_overflow">Arithmetic with Overflow Intrinsics</a> | |
| <ol> | |
| <li><a href="#int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt> Intrinsics</a></li> | |
| <li><a href="#int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt> Intrinsics</a></li> | |
| <li><a href="#int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt> Intrinsics</a></li> | |
| <li><a href="#int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt> Intrinsics</a></li> | |
| <li><a href="#int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt> Intrinsics</a></li> | |
| <li><a href="#int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt> Intrinsics</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_debugger">Debugger intrinsics</a></li> | |
| <li><a href="#int_eh">Exception Handling intrinsics</a></li> | |
| <li><a href="#int_trampoline">Trampoline Intrinsic</a> | |
| <ol> | |
| <li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_atomics">Atomic intrinsics</a> | |
| <ol> | |
| <li><a href="#int_memory_barrier"><tt>llvm.memory_barrier</tt></a></li> | |
| <li><a href="#int_atomic_cmp_swap"><tt>llvm.atomic.cmp.swap</tt></a></li> | |
| <li><a href="#int_atomic_swap"><tt>llvm.atomic.swap</tt></a></li> | |
| <li><a href="#int_atomic_load_add"><tt>llvm.atomic.load.add</tt></a></li> | |
| <li><a href="#int_atomic_load_sub"><tt>llvm.atomic.load.sub</tt></a></li> | |
| <li><a href="#int_atomic_load_and"><tt>llvm.atomic.load.and</tt></a></li> | |
| <li><a href="#int_atomic_load_nand"><tt>llvm.atomic.load.nand</tt></a></li> | |
| <li><a href="#int_atomic_load_or"><tt>llvm.atomic.load.or</tt></a></li> | |
| <li><a href="#int_atomic_load_xor"><tt>llvm.atomic.load.xor</tt></a></li> | |
| <li><a href="#int_atomic_load_max"><tt>llvm.atomic.load.max</tt></a></li> | |
| <li><a href="#int_atomic_load_min"><tt>llvm.atomic.load.min</tt></a></li> | |
| <li><a href="#int_atomic_load_umax"><tt>llvm.atomic.load.umax</tt></a></li> | |
| <li><a href="#int_atomic_load_umin"><tt>llvm.atomic.load.umin</tt></a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_general">General intrinsics</a> | |
| <ol> | |
| <li><a href="#int_var_annotation"> | |
| '<tt>llvm.var.annotation</tt>' Intrinsic</a></li> | |
| <li><a href="#int_annotation"> | |
| '<tt>llvm.annotation.*</tt>' Intrinsic</a></li> | |
| <li><a href="#int_trap"> | |
| '<tt>llvm.trap</tt>' Intrinsic</a></li> | |
| <li><a href="#int_stackprotector"> | |
| '<tt>llvm.stackprotector</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| </ol> | |
| </li> | |
| </ol> | |
| <div class="doc_author"> | |
| <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a> | |
| and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="abstract">Abstract </a></div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>This document is a reference manual for the LLVM assembly language. LLVM is | |
| a Static Single Assignment (SSA) based representation that provides type | |
| safety, low-level operations, flexibility, and the capability of representing | |
| 'all' high-level languages cleanly. It is the common code representation | |
| used throughout all phases of the LLVM compilation strategy.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="introduction">Introduction</a> </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>The LLVM code representation is designed to be used in three different forms: | |
| as an in-memory compiler IR, as an on-disk bitcode representation (suitable | |
| for fast loading by a Just-In-Time compiler), and as a human readable | |
| assembly language representation. This allows LLVM to provide a powerful | |
| intermediate representation for efficient compiler transformations and | |
| analysis, while providing a natural means to debug and visualize the | |
| transformations. The three different forms of LLVM are all equivalent. This | |
| document describes the human readable representation and notation.</p> | |
| <p>The LLVM representation aims to be light-weight and low-level while being | |
| expressive, typed, and extensible at the same time. It aims to be a | |
| "universal IR" of sorts, by being at a low enough level that high-level ideas | |
| may be cleanly mapped to it (similar to how microprocessors are "universal | |
| IR's", allowing many source languages to be mapped to them). By providing | |
| type information, LLVM can be used as the target of optimizations: for | |
| example, through pointer analysis, it can be proven that a C automatic | |
| variable is never accessed outside of the current function... allowing it to | |
| be promoted to a simple SSA value instead of a memory location.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div> | |
| <div class="doc_text"> | |
| <p>It is important to note that this document describes 'well formed' LLVM | |
| assembly language. There is a difference between what the parser accepts and | |
| what is considered 'well formed'. For example, the following instruction is | |
| syntactically okay, but not well formed:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| %x = <a href="#i_add">add</a> i32 1, %x | |
| </pre> | |
| </div> | |
| <p>...because the definition of <tt>%x</tt> does not dominate all of its | |
| uses. The LLVM infrastructure provides a verification pass that may be used | |
| to verify that an LLVM module is well formed. This pass is automatically run | |
| by the parser after parsing input assembly and by the optimizer before it | |
| outputs bitcode. The violations pointed out by the verifier pass indicate | |
| bugs in transformation passes or input to the parser.</p> | |
| </div> | |
| <!-- Describe the typesetting conventions here. --> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="identifiers">Identifiers</a> </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>LLVM identifiers come in two basic types: global and local. Global | |
| identifiers (functions, global variables) begin with the <tt>'@'</tt> | |
| character. Local identifiers (register names, types) begin with | |
| the <tt>'%'</tt> character. Additionally, there are three different formats | |
| for identifiers, for different purposes:</p> | |
| <ol> | |
| <li>Named values are represented as a string of characters with their prefix. | |
| For example, <tt>%foo</tt>, <tt>@DivisionByZero</tt>, | |
| <tt>%a.really.long.identifier</tt>. The actual regular expression used is | |
| '<tt>[%@][a-zA-Z$._][a-zA-Z$._0-9]*</tt>'. Identifiers which require | |
| other characters in their names can be surrounded with quotes. Special | |
| characters may be escaped using <tt>"\xx"</tt> where <tt>xx</tt> is the | |
| ASCII code for the character in hexadecimal. In this way, any character | |
| can be used in a name value, even quotes themselves.</li> | |
| <li>Unnamed values are represented as an unsigned numeric value with their | |
| prefix. For example, <tt>%12</tt>, <tt>@2</tt>, <tt>%44</tt>.</li> | |
| <li>Constants, which are described in a <a href="#constants">section about | |
| constants</a>, below.</li> | |
| </ol> | |
| <p>LLVM requires that values start with a prefix for two reasons: Compilers | |
| don't need to worry about name clashes with reserved words, and the set of | |
| reserved words may be expanded in the future without penalty. Additionally, | |
| unnamed identifiers allow a compiler to quickly come up with a temporary | |
| variable without having to avoid symbol table conflicts.</p> | |
| <p>Reserved words in LLVM are very similar to reserved words in other | |
| languages. There are keywords for different opcodes | |
| ('<tt><a href="#i_add">add</a></tt>', | |
| '<tt><a href="#i_bitcast">bitcast</a></tt>', | |
| '<tt><a href="#i_ret">ret</a></tt>', etc...), for primitive type names | |
| ('<tt><a href="#t_void">void</a></tt>', | |
| '<tt><a href="#t_primitive">i32</a></tt>', etc...), and others. These | |
| reserved words cannot conflict with variable names, because none of them | |
| start with a prefix character (<tt>'%'</tt> or <tt>'@'</tt>).</p> | |
| <p>Here is an example of LLVM code to multiply the integer variable | |
| '<tt>%X</tt>' by 8:</p> | |
| <p>The easy way:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| %result = <a href="#i_mul">mul</a> i32 %X, 8 | |
| </pre> | |
| </div> | |
| <p>After strength reduction:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| %result = <a href="#i_shl">shl</a> i32 %X, i8 3 | |
| </pre> | |
| </div> | |
| <p>And the hard way:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| <a href="#i_add">add</a> i32 %X, %X <i>; yields {i32}:%0</i> | |
| <a href="#i_add">add</a> i32 %0, %0 <i>; yields {i32}:%1</i> | |
| %result = <a href="#i_add">add</a> i32 %1, %1 | |
| </pre> | |
| </div> | |
| <p>This last way of multiplying <tt>%X</tt> by 8 illustrates several important | |
| lexical features of LLVM:</p> | |
| <ol> | |
| <li>Comments are delimited with a '<tt>;</tt>' and go until the end of | |
| line.</li> | |
| <li>Unnamed temporaries are created when the result of a computation is not | |
| assigned to a named value.</li> | |
| <li>Unnamed temporaries are numbered sequentially</li> | |
| </ol> | |
| <p>...and it also shows a convention that we follow in this document. When | |
| demonstrating instructions, we will follow an instruction with a comment that | |
| defines the type and name of value produced. Comments are shown in italic | |
| text.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="highlevel">High Level Structure</a> </div> | |
| <!-- *********************************************************************** --> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="modulestructure">Module Structure</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM programs are composed of "Module"s, each of which is a translation unit | |
| of the input programs. Each module consists of functions, global variables, | |
| and symbol table entries. Modules may be combined together with the LLVM | |
| linker, which merges function (and global variable) definitions, resolves | |
| forward declarations, and merges symbol table entries. Here is an example of | |
| the "hello world" module:</p> | |
| <div class="doc_code"> | |
| <pre><i>; Declare the string constant as a global constant...</i> | |
| <a href="#identifiers">@.LC0</a> = <a href="#linkage_internal">internal</a> <a | |
| href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" <i>; [13 x i8]*</i> | |
| <i>; External declaration of the puts function</i> | |
| <a href="#functionstructure">declare</a> i32 @puts(i8 *) <i>; i32(i8 *)* </i> | |
| <i>; Definition of main function</i> | |
| define i32 @main() { <i>; i32()* </i> | |
| <i>; Convert [13 x i8]* to i8 *...</i> | |
| %cast210 = <a | |
| href="#i_getelementptr">getelementptr</a> [13 x i8]* @.LC0, i64 0, i64 0 <i>; i8 *</i> | |
| <i>; Call puts function to write out the string to stdout...</i> | |
| <a | |
| href="#i_call">call</a> i32 @puts(i8 * %cast210) <i>; i32</i> | |
| <a | |
| href="#i_ret">ret</a> i32 0<br>}<br> | |
| </pre> | |
| </div> | |
| <p>This example is made up of a <a href="#globalvars">global variable</a> named | |
| "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>" function, and | |
| a <a href="#functionstructure">function definition</a> for | |
| "<tt>main</tt>".</p> | |
| <p>In general, a module is made up of a list of global values, where both | |
| functions and global variables are global values. Global values are | |
| represented by a pointer to a memory location (in this case, a pointer to an | |
| array of char, and a pointer to a function), and have one of the | |
| following <a href="#linkage">linkage types</a>.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="linkage">Linkage Types</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>All Global Variables and Functions have one of the following types of | |
| linkage:</p> | |
| <dl> | |
| <dt><tt><b><a name="linkage_private">private</a></b></tt>: </dt> | |
| <dd>Global values with private linkage are only directly accessible by objects | |
| in the current module. In particular, linking code into a module with an | |
| private global value may cause the private to be renamed as necessary to | |
| avoid collisions. Because the symbol is private to the module, all | |
| references can be updated. This doesn't show up in any symbol table in the | |
| object file.</dd> | |
| <dt><tt><b><a name="linkage_linker_private">linker_private</a></b></tt>: </dt> | |
| <dd>Similar to private, but the symbol is passed through the assembler and | |
| removed by the linker after evaluation.</dd> | |
| <dt><tt><b><a name="linkage_internal">internal</a></b></tt>: </dt> | |
| <dd>Similar to private, but the value shows as a local symbol | |
| (<tt>STB_LOCAL</tt> in the case of ELF) in the object file. This | |
| corresponds to the notion of the '<tt>static</tt>' keyword in C.</dd> | |
| <dt><tt><b><a name="linkage_available_externally">available_externally</a></b></tt>: </dt> | |
| <dd>Globals with "<tt>available_externally</tt>" linkage are never emitted | |
| into the object file corresponding to the LLVM module. They exist to | |
| allow inlining and other optimizations to take place given knowledge of | |
| the definition of the global, which is known to be somewhere outside the | |
| module. Globals with <tt>available_externally</tt> linkage are allowed to | |
| be discarded at will, and are otherwise the same as <tt>linkonce_odr</tt>. | |
| This linkage type is only allowed on definitions, not declarations.</dd> | |
| <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt> | |
| <dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of | |
| the same name when linkage occurs. This is typically used to implement | |
| inline functions, templates, or other code which must be generated in each | |
| translation unit that uses it. Unreferenced <tt>linkonce</tt> globals are | |
| allowed to be discarded.</dd> | |
| <dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt> | |
| <dd>"<tt>weak</tt>" linkage has the same merging semantics as | |
| <tt>linkonce</tt> linkage, except that unreferenced globals with | |
| <tt>weak</tt> linkage may not be discarded. This is used for globals that | |
| are declared "weak" in C source code.</dd> | |
| <dt><tt><b><a name="linkage_common">common</a></b></tt>: </dt> | |
| <dd>"<tt>common</tt>" linkage is most similar to "<tt>weak</tt>" linkage, but | |
| they are used for tentative definitions in C, such as "<tt>int X;</tt>" at | |
| global scope. | |
| Symbols with "<tt>common</tt>" linkage are merged in the same way as | |
| <tt>weak symbols</tt>, and they may not be deleted if unreferenced. | |
| <tt>common</tt> symbols may not have an explicit section, | |
| must have a zero initializer, and may not be marked '<a | |
| href="#globalvars"><tt>constant</tt></a>'. Functions and aliases may not | |
| have common linkage.</dd> | |
| <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_externweak">extern_weak</a></b></tt>: </dt> | |
| <dd>The semantics of this linkage follow the ELF object file model: the symbol | |
| is weak until linked, if not linked, the symbol becomes null instead of | |
| being an undefined reference.</dd> | |
| <dt><tt><b><a name="linkage_linkonce">linkonce_odr</a></b></tt>: </dt> | |
| <dt><tt><b><a name="linkage_weak">weak_odr</a></b></tt>: </dt> | |
| <dd>Some languages allow differing globals to be merged, such as two functions | |
| with different semantics. Other languages, such as <tt>C++</tt>, ensure | |
| that only equivalent globals are ever merged (the "one definition rule" - | |
| "ODR"). Such languages can use the <tt>linkonce_odr</tt> | |
| and <tt>weak_odr</tt> linkage types to indicate that the global will only | |
| be merged with equivalent globals. These linkage types are otherwise the | |
| same as their non-<tt>odr</tt> versions.</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>The next two types of linkage are targeted for Microsoft Windows platform | |
| only. They are designed to support importing (exporting) symbols from (to) | |
| DLLs (Dynamic Link Libraries).</p> | |
| <dl> | |
| <dt><tt><b><a name="linkage_dllimport">dllimport</a></b></tt>: </dt> | |
| <dd>"<tt>dllimport</tt>" linkage causes the compiler to reference a function | |
| or variable via a global pointer to a pointer that is set up by the DLL | |
| exporting the symbol. On Microsoft Windows targets, the pointer name is | |
| formed by combining <code>__imp_</code> and the function or variable | |
| name.</dd> | |
| <dt><tt><b><a name="linkage_dllexport">dllexport</a></b></tt>: </dt> | |
| <dd>"<tt>dllexport</tt>" linkage causes the compiler to provide a global | |
| pointer to a pointer in a DLL, so that it can be referenced with the | |
| <tt>dllimport</tt> attribute. On Microsoft Windows targets, the pointer | |
| name is formed by combining <code>__imp_</code> and the function or | |
| variable name.</dd> | |
| </dl> | |
| <p>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.</p> | |
| <p>It is illegal for a function <i>declaration</i> to have any linkage type | |
| other than "externally visible", <tt>dllimport</tt> | |
| or <tt>extern_weak</tt>.</p> | |
| <p>Aliases can have only <tt>external</tt>, <tt>internal</tt>, <tt>weak</tt> | |
| or <tt>weak_odr</tt> linkages.</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 | |
| (Application Binary Interface). Implementations of this convention should | |
| allow arbitrary <a href="CodeGenerator.html#tailcallopt">tail call | |
| optimization</a> 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="visibility">Visibility Styles</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>All Global Variables and Functions have one of the following visibility | |
| styles:</p> | |
| <dl> | |
| <dt><b>"<tt>default</tt>" - Default style</b>:</dt> | |
| <dd>On targets that use the ELF object file format, default visibility means | |
| that the declaration is visible to other modules and, in shared libraries, | |
| means that the declared entity may be overridden. On Darwin, default | |
| visibility means that the declaration is visible to other modules. Default | |
| visibility corresponds to "external linkage" in the language.</dd> | |
| <dt><b>"<tt>hidden</tt>" - Hidden style</b>:</dt> | |
| <dd>Two declarations of an object with hidden visibility refer to the same | |
| object if they are in the same shared object. Usually, hidden visibility | |
| indicates that the symbol will not be placed into the dynamic symbol | |
| table, so no other module (executable or shared library) can reference it | |
| directly.</dd> | |
| <dt><b>"<tt>protected</tt>" - Protected style</b>:</dt> | |
| <dd>On ELF, protected visibility indicates that the symbol will be placed in | |
| the dynamic symbol table, but that references within the defining module | |
| will bind to the local symbol. That is, the symbol cannot be overridden by | |
| another module.</dd> | |
| </dl> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="namedtypes">Named Types</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM IR allows you to specify name aliases for certain types. This can make | |
| it easier to read the IR and make the IR more condensed (particularly when | |
| recursive types are involved). An example of a name specification is:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| %mytype = type { %mytype*, i32 } | |
| </pre> | |
| </div> | |
| <p>You may give a name to any <a href="#typesystem">type</a> except | |
| "<a href="t_void">void</a>". Type name aliases may be used anywhere a type | |
| is expected with the syntax "%mytype".</p> | |
| <p>Note that type names are aliases for the structural type that they indicate, | |
| and that you can therefore specify multiple names for the same type. This | |
| often leads to confusing behavior when dumping out a .ll file. Since LLVM IR | |
| uses structural typing, the name is not part of the type. When printing out | |
| LLVM IR, the printer will pick <em>one name</em> to render all types of a | |
| particular shape. This means that if you have code where two different | |
| source types end up having the same LLVM type, that the dumper will sometimes | |
| print the "wrong" or unexpected type. This is an important design point and | |
| isn't going to change.</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, may | |
| have an explicit section to be placed in, and may have an optional explicit | |
| alignment specified. A variable may be defined as "thread_local", which | |
| means that it will not be shared by threads (each thread will have a | |
| separated copy of the variable). 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> | |
| <p>A global variable may be declared to reside in a target-specific numbered | |
| address space. For targets that support them, address spaces may affect how | |
| optimizations are performed and/or what target instructions are used to | |
| access the variable. The default address space is zero. The address space | |
| qualifier must precede any other attributes.</p> | |
| <p>LLVM allows an explicit section to be specified for globals. If the target | |
| supports it, it will emit globals to the section specified.</p> | |
| <p>An explicit alignment may be specified for a global. If not present, or if | |
| the alignment is set to zero, the alignment of the global is set by the | |
| target to whatever it feels convenient. If an explicit alignment is | |
| specified, the global is forced to have at least that much alignment. All | |
| alignments must be a power of 2.</p> | |
| <p>For example, the following defines a global in a numbered address space with | |
| an initializer, section, and alignment:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| @G = addrspace(5) constant float 1.0, section "foo", align 4 | |
| </pre> | |
| </div> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="functionstructure">Functions</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM function definitions consist of the "<tt>define</tt>" keyord, an | |
| optional <a href="#linkage">linkage type</a>, an optional | |
| <a href="#visibility">visibility style</a>, an optional | |
| <a href="#callingconv">calling convention</a>, a return type, an optional | |
| <a href="#paramattrs">parameter attribute</a> for the return type, a function | |
| name, a (possibly empty) argument list (each with optional | |
| <a href="#paramattrs">parameter attributes</a>), optional | |
| <a href="#fnattrs">function attributes</a>, an optional section, an optional | |
| alignment, an optional <a href="#gc">garbage collector name</a>, an opening | |
| curly brace, a list of basic blocks, and a closing curly brace.</p> | |
| <p>LLVM function declarations consist of the "<tt>declare</tt>" keyword, an | |
| optional <a href="#linkage">linkage type</a>, an optional | |
| <a href="#visibility">visibility style</a>, an optional | |
| <a href="#callingconv">calling convention</a>, a return type, an optional | |
| <a href="#paramattrs">parameter attribute</a> for the return type, a function | |
| name, a possibly empty list of arguments, an optional alignment, and an | |
| optional <a href="#gc">garbage collector name</a>.</p> | |
| <p>A function definition contains a list of basic blocks, forming the CFG | |
| (Control Flow Graph) 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 function 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 allows an explicit section to be specified for functions. If the target | |
| supports it, it will emit functions to the section specified.</p> | |
| <p>An explicit alignment may be specified for a function. If not present, or if | |
| the alignment is set to zero, the alignment of the function is set by the | |
| target to whatever it feels convenient. If an explicit alignment is | |
| specified, the function is forced to have at least that much alignment. All | |
| alignments must be a power of 2.</p> | |
| <h5>Syntax:</h5> | |
| <div class="doc_code"> | |
| <pre> | |
| define [<a href="#linkage">linkage</a>] [<a href="#visibility">visibility</a>] | |
| [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] | |
| <ResultType> @<FunctionName> ([argument list]) | |
| [<a href="#fnattrs">fn Attrs</a>] [section "name"] [align N] | |
| [<a href="#gc">gc</a>] { ... } | |
| </pre> | |
| </div> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="aliasstructure">Aliases</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Aliases act as "second name" for the aliasee value (which can be either | |
| function, global variable, another alias or bitcast of global value). Aliases | |
| may have an optional <a href="#linkage">linkage type</a>, and an | |
| optional <a href="#visibility">visibility style</a>.</p> | |
| <h5>Syntax:</h5> | |
| <div class="doc_code"> | |
| <pre> | |
| @<Name> = alias [Linkage] [Visibility] <AliaseeTy> @<Aliasee> | |
| </pre> | |
| </div> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"><a name="paramattrs">Parameter Attributes</a></div> | |
| <div class="doc_text"> | |
| <p>The return type and each parameter of a function type may have a set of | |
| <i>parameter attributes</i> associated with them. Parameter attributes are | |
| used to communicate additional information about the result or parameters of | |
| a function. Parameter attributes are considered to be part of the function, | |
| not of the function type, so functions with different parameter attributes | |
| can have the same function type.</p> | |
| <p>Parameter attributes are simple keywords that follow the type specified. If | |
| multiple parameter attributes are needed, they are space separated. For | |
| example:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| declare i32 @printf(i8* noalias nocapture, ...) | |
| declare i32 @atoi(i8 zeroext) | |
| declare signext i8 @returns_signed_char() | |
| </pre> | |
| </div> | |
| <p>Note that any attributes for the function result (<tt>nounwind</tt>, | |
| <tt>readonly</tt>) come immediately after the argument list.</p> | |
| <p>Currently, only the following parameter attributes are defined:</p> | |
| <dl> | |
| <dt><tt>zeroext</tt></dt> | |
| <dd>This indicates to the code generator that the parameter or return value | |
| should be zero-extended to a 32-bit value by the caller (for a parameter) | |
| or the callee (for a return value).</dd> | |
| <dt><tt>signext</tt></dt> | |
| <dd>This indicates to the code generator that the parameter or return value | |
| should be sign-extended to a 32-bit value by the caller (for a parameter) | |
| or the callee (for a return value).</dd> | |
| <dt><tt>inreg</tt></dt> | |
| <dd>This indicates that this parameter or return value should be treated in a | |
| special target-dependent fashion during while emitting code for a function | |
| call or return (usually, by putting it in a register as opposed to memory, | |
| though some targets use it to distinguish between two different kinds of | |
| registers). Use of this attribute is target-specific.</dd> | |
| <dt><tt><a name="byval">byval</a></tt></dt> | |
| <dd>This indicates that the pointer parameter should really be passed by value | |
| to the function. The attribute implies that a hidden copy of the pointee | |
| is made between the caller and the callee, so the callee is unable to | |
| modify the value in the callee. This attribute is only valid on LLVM | |
| pointer arguments. It is generally used to pass structs and arrays by | |
| value, but is also valid on pointers to scalars. The copy is considered | |
| to belong to the caller not the callee (for example, | |
| <tt><a href="#readonly">readonly</a></tt> functions should not write to | |
| <tt>byval</tt> parameters). This is not a valid attribute for return | |
| values. The byval attribute also supports specifying an alignment with | |
| the align attribute. This has a target-specific effect on the code | |
| generator that usually indicates a desired alignment for the synthesized | |
| stack slot.</dd> | |
| <dt><tt>sret</tt></dt> | |
| <dd>This indicates that the pointer parameter specifies the address of a | |
| structure that is the return value of the function in the source program. | |
| This pointer must be guaranteed by the caller to be valid: loads and | |
| stores to the structure may be assumed by the callee to not to trap. This | |
| may only be applied to the first parameter. This is not a valid attribute | |
| for return values. </dd> | |
| <dt><tt>noalias</tt></dt> | |
| <dd>This indicates that the pointer does not alias any global or any other | |
| parameter. The caller is responsible for ensuring that this is the | |
| case. On a function return value, <tt>noalias</tt> additionally indicates | |
| that the pointer does not alias any other pointers visible to the | |
| caller. For further details, please see the discussion of the NoAlias | |
| response in | |
| <a href="http://llvm.org/docs/AliasAnalysis.html#MustMayNo">alias | |
| analysis</a>.</dd> | |
| <dt><tt>nocapture</tt></dt> | |
| <dd>This indicates that the callee does not make any copies of the pointer | |
| that outlive the callee itself. This is not a valid attribute for return | |
| values.</dd> | |
| <dt><tt>nest</tt></dt> | |
| <dd>This indicates that the pointer parameter can be excised using the | |
| <a href="#int_trampoline">trampoline intrinsics</a>. This is not a valid | |
| attribute for return values.</dd> | |
| </dl> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="gc">Garbage Collector Names</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Each function may specify a garbage collector name, which is simply a | |
| string:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| define void @f() gc "name" { ... | |
| </pre> | |
| </div> | |
| <p>The compiler declares the supported values of <i>name</i>. Specifying a | |
| collector which will cause the compiler to alter its output in order to | |
| support the named garbage collection algorithm.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="fnattrs">Function Attributes</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Function attributes are set to communicate additional information about a | |
| function. Function attributes are considered to be part of the function, not | |
| of the function type, so functions with different parameter attributes can | |
| have the same function type.</p> | |
| <p>Function attributes are simple keywords that follow the type specified. If | |
| multiple attributes are needed, they are space separated. For example:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| define void @f() noinline { ... } | |
| define void @f() alwaysinline { ... } | |
| define void @f() alwaysinline optsize { ... } | |
| define void @f() optsize | |
| </pre> | |
| </div> | |
| <dl> | |
| <dt><tt>alwaysinline</tt></dt> | |
| <dd>This attribute indicates that the inliner should attempt to inline this | |
| function into callers whenever possible, ignoring any active inlining size | |
| threshold for this caller.</dd> | |
| <dt><tt>noinline</tt></dt> | |
| <dd>This attribute indicates that the inliner should never inline this | |
| function in any situation. This attribute may not be used together with | |
| the <tt>alwaysinline</tt> attribute.</dd> | |
| <dt><tt>optsize</tt></dt> | |
| <dd>This attribute suggests that optimization passes and code generator passes | |
| make choices that keep the code size of this function low, and otherwise | |
| do optimizations specifically to reduce code size.</dd> | |
| <dt><tt>noreturn</tt></dt> | |
| <dd>This function attribute indicates that the function never returns | |
| normally. This produces undefined behavior at runtime if the function | |
| ever does dynamically return.</dd> | |
| <dt><tt>nounwind</tt></dt> | |
| <dd>This function attribute indicates that the function never returns with an | |
| unwind or exceptional control flow. If the function does unwind, its | |
| runtime behavior is undefined.</dd> | |
| <dt><tt>readnone</tt></dt> | |
| <dd>This attribute indicates that the function computes its result (or decides | |
| to unwind an exception) based strictly on its arguments, without | |
| dereferencing any pointer arguments or otherwise accessing any mutable | |
| state (e.g. memory, control registers, etc) visible to caller functions. | |
| It does not write through any pointer arguments | |
| (including <tt><a href="#byval">byval</a></tt> arguments) and never | |
| changes any state visible to callers. This means that it cannot unwind | |
| exceptions by calling the <tt>C++</tt> exception throwing methods, but | |
| could use the <tt>unwind</tt> instruction.</dd> | |
| <dt><tt><a name="readonly">readonly</a></tt></dt> | |
| <dd>This attribute indicates that the function does not write through any | |
| pointer arguments (including <tt><a href="#byval">byval</a></tt> | |
| arguments) or otherwise modify any state (e.g. memory, control registers, | |
| etc) visible to caller functions. It may dereference pointer arguments | |
| and read state that may be set in the caller. A readonly function always | |
| returns the same value (or unwinds an exception identically) when called | |
| with the same set of arguments and global state. It cannot unwind an | |
| exception by calling the <tt>C++</tt> exception throwing methods, but may | |
| use the <tt>unwind</tt> instruction.</dd> | |
| <dt><tt><a name="ssp">ssp</a></tt></dt> | |
| <dd>This attribute indicates that the function should emit a stack smashing | |
| protector. It is in the form of a "canary"—a random value placed on | |
| the stack before the local variables that's checked upon return from the | |
| function to see if it has been overwritten. A heuristic is used to | |
| determine if a function needs stack protectors or not.<br> | |
| <br> | |
| If a function that has an <tt>ssp</tt> attribute is inlined into a | |
| function that doesn't have an <tt>ssp</tt> attribute, then the resulting | |
| function will have an <tt>ssp</tt> attribute.</dd> | |
| <dt><tt>sspreq</tt></dt> | |
| <dd>This attribute indicates that the function should <em>always</em> emit a | |
| stack smashing protector. This overrides | |
| the <tt><a href="#ssp">ssp</a></tt> function attribute.<br> | |
| <br> | |
| If a function that has an <tt>sspreq</tt> attribute is inlined into a | |
| function that doesn't have an <tt>sspreq</tt> attribute or which has | |
| an <tt>ssp</tt> attribute, then the resulting function will have | |
| an <tt>sspreq</tt> attribute.</dd> | |
| <dt><tt>noredzone</tt></dt> | |
| <dd>This attribute indicates that the code generator should not use a red | |
| zone, even if the target-specific ABI normally permits it.</dd> | |
| <dt><tt>noimplicitfloat</tt></dt> | |
| <dd>This attributes disables implicit floating point instructions.</dd> | |
| <dt><tt>naked</tt></dt> | |
| <dd>This attribute disables prologue / epilogue emission for the function. | |
| This can have very system-specific consequences.</dd> | |
| </dl> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="moduleasm">Module-Level Inline Assembly</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Modules may contain "module-level inline asm" blocks, which corresponds to | |
| the GCC "file scope inline asm" blocks. These blocks are internally | |
| concatenated by LLVM and treated as a single unit, but may be separated in | |
| the <tt>.ll</tt> file if desired. The syntax is very simple:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| module asm "inline asm code goes here" | |
| module asm "more can go here" | |
| </pre> | |
| </div> | |
| <p>The strings can contain any character by escaping non-printable characters. | |
| The escape sequence used is simply "\xx" where "xx" is the two digit hex code | |
| for the number.</p> | |
| <p>The inline asm code is simply printed to the machine code .s file when | |
| assembly code is generated.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="datalayout">Data Layout</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>A module may specify a target specific data layout string that specifies how | |
| data is to be laid out in memory. The syntax for the data layout is | |
| simply:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| target datalayout = "<i>layout specification</i>" | |
| </pre> | |
| </div> | |
| <p>The <i>layout specification</i> consists of a list of specifications | |
| separated by the minus sign character ('-'). Each specification starts with | |
| a letter and may include other information after the letter to define some | |
| aspect of the data layout. The specifications accepted are as follows:</p> | |
| <dl> | |
| <dt><tt>E</tt></dt> | |
| <dd>Specifies that the target lays out data in big-endian form. That is, the | |
| bits with the most significance have the lowest address location.</dd> | |
| <dt><tt>e</tt></dt> | |
| <dd>Specifies that the target lays out data in little-endian form. That is, | |
| the bits with the least significance have the lowest address | |
| location.</dd> | |
| <dt><tt>p:<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> | |
| <dd>This specifies the <i>size</i> of a pointer and its <i>abi</i> and | |
| <i>preferred</i> alignments. All sizes are in bits. Specifying | |
| the <i>pref</i> alignment is optional. If omitted, the | |
| preceding <tt>:</tt> should be omitted too.</dd> | |
| <dt><tt>i<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> | |
| <dd>This specifies the alignment for an integer type of a given bit | |
| <i>size</i>. The value of <i>size</i> must be in the range [1,2^23).</dd> | |
| <dt><tt>v<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> | |
| <dd>This specifies the alignment for a vector type of a given bit | |
| <i>size</i>.</dd> | |
| <dt><tt>f<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> | |
| <dd>This specifies the alignment for a floating point type of a given bit | |
| <i>size</i>. The value of <i>size</i> must be either 32 (float) or 64 | |
| (double).</dd> | |
| <dt><tt>a<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> | |
| <dd>This specifies the alignment for an aggregate type of a given bit | |
| <i>size</i>.</dd> | |
| <dt><tt>s<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> | |
| <dd>This specifies the alignment for a stack object of a given bit | |
| <i>size</i>.</dd> | |
| </dl> | |
| <p>When constructing the data layout for a given target, LLVM starts with a | |
| default set of specifications which are then (possibly) overriden by the | |
| specifications in the <tt>datalayout</tt> keyword. The default specifications | |
| are given in this list:</p> | |
| <ul> | |
| <li><tt>E</tt> - big endian</li> | |
| <li><tt>p:32:64:64</tt> - 32-bit pointers with 64-bit alignment</li> | |
| <li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li> | |
| <li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li> | |
| <li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li> | |
| <li><tt>i32:32:32</tt> - i32 is 32-bit aligned</li> | |
| <li><tt>i64:32:64</tt> - i64 has ABI alignment of 32-bits but preferred | |
| alignment of 64-bits</li> | |
| <li><tt>f32:32:32</tt> - float is 32-bit aligned</li> | |
| <li><tt>f64:64:64</tt> - double is 64-bit aligned</li> | |
| <li><tt>v64:64:64</tt> - 64-bit vector is 64-bit aligned</li> | |
| <li><tt>v128:128:128</tt> - 128-bit vector is 128-bit aligned</li> | |
| <li><tt>a0:0:1</tt> - aggregates are 8-bit aligned</li> | |
| <li><tt>s0:64:64</tt> - stack objects are 64-bit aligned</li> | |
| </ul> | |
| <p>When LLVM is determining the alignment for a given type, it uses the | |
| following rules:</p> | |
| <ol> | |
| <li>If the type sought is an exact match for one of the specifications, that | |
| specification is used.</li> | |
| <li>If no match is found, and the type sought is an integer type, then the | |
| smallest integer type that is larger than the bitwidth of the sought type | |
| is used. If none of the specifications are larger than the bitwidth then | |
| the the largest integer type is used. For example, given the default | |
| specifications above, the i7 type will use the alignment of i8 (next | |
| largest) while both i65 and i256 will use the alignment of i64 (largest | |
| specified).</li> | |
| <li>If no match is found, and the type sought is a vector type, then the | |
| largest vector type that is smaller than the sought vector type will be | |
| used as a fall back. This happens because <128 x double> can be | |
| implemented in terms of 64 <2 x double>, for example.</li> | |
| </ol> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="pointeraliasing">Pointer Aliasing Rules</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Any memory access must be done through a pointer value associated | |
| with an address range of the memory access, otherwise the behavior | |
| is undefined. Pointer values are associated with address ranges | |
| according to the following rules:</p> | |
| <ul> | |
| <li>A pointer value formed from a | |
| <tt><a href="#i_getelementptr">getelementptr</a></tt> instruction | |
| is associated with the addresses associated with the first operand | |
| of the <tt>getelementptr</tt>.</li> | |
| <li>An address of a global variable is associated with the address | |
| range of the variable's storage.</li> | |
| <li>The result value of an allocation instruction is associated with | |
| the address range of the allocated storage.</li> | |
| <li>A null pointer in the default address-space is associated with | |
| no address.</li> | |
| <li>A pointer value formed by an | |
| <tt><a href="#i_inttoptr">inttoptr</a></tt> is associated with all | |
| address ranges of all pointer values that contribute (directly or | |
| indirectly) to the computation of the pointer's value.</li> | |
| <li>The result value of a | |
| <tt><a href="#i_bitcast">bitcast</a></tt> is associated with all | |
| addresses associated with the operand of the <tt>bitcast</tt>.</li> | |
| <li>An integer constant other than zero or a pointer value returned | |
| from a function not defined within LLVM may be associated with address | |
| ranges allocated through mechanisms other than those provided by | |
| LLVM. Such ranges shall not overlap with any ranges of addresses | |
| allocated by mechanisms provided by LLVM.</li> | |
| </ul> | |
| <p>LLVM IR does not associate types with memory. The result type of a | |
| <tt><a href="#i_load">load</a></tt> merely indicates the size and | |
| alignment of the memory from which to load, as well as the | |
| interpretation of the value. The first operand of a | |
| <tt><a href="#i_store">store</a></tt> similarly only indicates the size | |
| and alignment of the store.</p> | |
| <p>Consequently, type-based alias analysis, aka TBAA, aka | |
| <tt>-fstrict-aliasing</tt>, is not applicable to general unadorned | |
| LLVM IR. <a href="#metadata">Metadata</a> may be used to encode | |
| additional information which specialized optimization passes may use | |
| to implement type-based alias analysis.</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 intermediate representation 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_classifications">Type | |
| Classifications</a> </div> | |
| <div class="doc_text"> | |
| <p>The 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 href="#t_integer">integer</a></td> | |
| <td><tt>i1, i2, i3, ... i8, ... i16, ... i32, ... i64, ... </tt></td> | |
| </tr> | |
| <tr> | |
| <td><a href="#t_floating">floating point</a></td> | |
| <td><tt>float, double, x86_fp80, fp128, ppc_fp128</tt></td> | |
| </tr> | |
| <tr> | |
| <td><a name="t_firstclass">first class</a></td> | |
| <td><a href="#t_integer">integer</a>, | |
| <a href="#t_floating">floating point</a>, | |
| <a href="#t_pointer">pointer</a>, | |
| <a href="#t_vector">vector</a>, | |
| <a href="#t_struct">structure</a>, | |
| <a href="#t_array">array</a>, | |
| <a href="#t_label">label</a>, | |
| <a href="#t_metadata">metadata</a>. | |
| </td> | |
| </tr> | |
| <tr> | |
| <td><a href="#t_primitive">primitive</a></td> | |
| <td><a href="#t_label">label</a>, | |
| <a href="#t_void">void</a>, | |
| <a href="#t_floating">floating point</a>, | |
| <a href="#t_metadata">metadata</a>.</td> | |
| </tr> | |
| <tr> | |
| <td><a href="#t_derived">derived</a></td> | |
| <td><a href="#t_integer">integer</a>, | |
| <a href="#t_array">array</a>, | |
| <a href="#t_function">function</a>, | |
| <a href="#t_pointer">pointer</a>, | |
| <a href="#t_struct">structure</a>, | |
| <a href="#t_pstruct">packed structure</a>, | |
| <a href="#t_vector">vector</a>, | |
| <a href="#t_opaque">opaque</a>. | |
| </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.</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.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_floating">Floating Point Types</a> </div> | |
| <div class="doc_text"> | |
| <table> | |
| <tbody> | |
| <tr><th>Type</th><th>Description</th></tr> | |
| <tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr> | |
| <tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr> | |
| <tr><td><tt>fp128</tt></td><td>128-bit floating point value (112-bit mantissa)</td></tr> | |
| <tr><td><tt>x86_fp80</tt></td><td>80-bit floating point value (X87)</td></tr> | |
| <tr><td><tt>ppc_fp128</tt></td><td>128-bit floating point value (two 64-bits)</td></tr> | |
| </tbody> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_void">Void Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>The void type does not represent any value and has no size.</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| void | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_label">Label Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>The label type represents code labels.</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| label | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_metadata">Metadata Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>The metadata type represents embedded metadata. The only derived type that | |
| may contain metadata is <tt>metadata*</tt> or a function type that returns or | |
| takes metadata typed parameters, but not pointer to metadata types.</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| metadata | |
| </pre> | |
| </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_integer">Integer Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>The integer type is a very simple derived type that simply specifies an | |
| arbitrary bit width for the integer type desired. Any bit width from 1 bit to | |
| 2^23-1 (about 8 million) can be specified.</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| iN | |
| </pre> | |
| <p>The number of bits the integer will occupy is specified by the <tt>N</tt> | |
| value.</p> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"><tt>i1</tt></td> | |
| <td class="left">a single-bit integer.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt>i32</tt></td> | |
| <td class="left">a 32-bit integer.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt>i1942652</tt></td> | |
| <td class="left">a really big integer of over 1 million bits.</td> | |
| </tr> | |
| </table> | |
| <p>Note that the code generator does not yet support large integer types to be | |
| used as function return types. The specific limit on how large a return type | |
| the code generator can currently handle is target-dependent; currently it's | |
| often 64 bits for 32-bit targets and 128 bits for 64-bit targets.</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; <tt>elementtype</tt> may | |
| be any type with a size.</p> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"><tt>[40 x i32]</tt></td> | |
| <td class="left">Array of 40 32-bit integer values.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt>[41 x i32]</tt></td> | |
| <td class="left">Array of 41 32-bit integer values.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt>[4 x i8]</tt></td> | |
| <td class="left">Array of 4 8-bit integer values.</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 i32]]</tt></td> | |
| <td class="left">3x4 array of 32-bit integer values.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt>[12 x [10 x float]]</tt></td> | |
| <td class="left">12x10 array of single precision floating point values.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt>[2 x [3 x [4 x i16]]]</tt></td> | |
| <td class="left">2x3x4 array of 16-bit integer values.</td> | |
| </tr> | |
| </table> | |
| <p>Note that 'variable sized arrays' can be implemented in LLVM with a zero | |
| length array. Normally, accesses past the end of an array are undefined in | |
| LLVM (e.g. it is illegal to access the 5th element of a 3 element array). As | |
| a special case, however, zero length arrays are recognized to be variable | |
| length. This allows implementation of 'pascal style arrays' with the LLVM | |
| type "<tt>{ i32, [0 x float]}</tt>", for example.</p> | |
| <p>Note that the code generator does not yet support large aggregate types to be | |
| used as function return types. The specific limit on how large an aggregate | |
| return type the code generator can currently handle is target-dependent, and | |
| also dependent on the aggregate element types.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>The function type can be thought of as a function signature. It consists of | |
| a return type and a list of formal parameter types. The return type of a | |
| function type is a scalar type, a void type, or a struct type. If the return | |
| type is a struct type then all struct elements must be of first class types, | |
| and the struct must have at least one element.</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <returntype list> (<parameter list>) | |
| </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. '<tt><returntype list></tt>' is a comma-separated list of | |
| <a href="#t_firstclass">first class</a> type specifiers.</p> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"><tt>i32 (i32)</tt></td> | |
| <td class="left">function taking an <tt>i32</tt>, returning an <tt>i32</tt> | |
| </td> | |
| </tr><tr class="layout"> | |
| <td class="left"><tt>float (i16 signext, i32 *) * | |
| </tt></td> | |
| <td class="left"><a href="#t_pointer">Pointer</a> to a function that takes | |
| an <tt>i16</tt> that should be sign extended and a | |
| <a href="#t_pointer">pointer</a> to <tt>i32</tt>, returning | |
| <tt>float</tt>. | |
| </td> | |
| </tr><tr class="layout"> | |
| <td class="left"><tt>i32 (i8*, ...)</tt></td> | |
| <td class="left">A vararg function that takes at least one | |
| <a href="#t_pointer">pointer</a> to <tt>i8 </tt> (char in C), | |
| which returns an integer. This is the signature for <tt>printf</tt> in | |
| LLVM. | |
| </td> | |
| </tr><tr class="layout"> | |
| <td class="left"><tt>{i32, i32} (i32)</tt></td> | |
| <td class="left">A function taking an <tt>i32</tt>, returning two | |
| <tt>i32</tt> values as an aggregate of type <tt>{ i32, i32 }</tt> | |
| </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> } | |
| </pre> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"><tt>{ i32, i32, i32 }</tt></td> | |
| <td class="left">A triple of three <tt>i32</tt> values</td> | |
| </tr><tr class="layout"> | |
| <td class="left"><tt>{ float, i32 (i32) * }</tt></td> | |
| <td class="left">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>i32</tt>, returning | |
| an <tt>i32</tt>.</td> | |
| </tr> | |
| </table> | |
| <p>Note that the code generator does not yet support large aggregate types to be | |
| used as function return types. The specific limit on how large an aggregate | |
| return type the code generator can currently handle is target-dependent, and | |
| also dependent on the aggregate element types.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_pstruct">Packed Structure Type</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>The packed structure type is used to represent a collection of data members | |
| together in memory. There is no padding between fields. Further, the | |
| alignment of a packed structure is 1 byte. The elements of a packed | |
| 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> } > | |
| </pre> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"><tt>< { i32, i32, i32 } ></tt></td> | |
| <td class="left">A triple of three <tt>i32</tt> values</td> | |
| </tr><tr class="layout"> | |
| <td class="left"> | |
| <tt>< { float, i32 (i32)* } ></tt></td> | |
| <td class="left">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>i32</tt>, returning | |
| an <tt>i32</tt>.</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. Pointer types may have an optional | |
| address space attribute defining the target-specific numbered address space | |
| where the pointed-to object resides. The default address space is zero.</p> | |
| <p>Note that LLVM does not permit pointers to void (<tt>void*</tt>) nor does it | |
| permit pointers to labels (<tt>label*</tt>). Use <tt>i8*</tt> instead.</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <type> * | |
| </pre> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"><tt>[4 x i32]*</tt></td> | |
| <td class="left">A <a href="#t_pointer">pointer</a> to <a | |
| href="#t_array">array</a> of four <tt>i32</tt> values.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt>i32 (i32 *) *</tt></td> | |
| <td class="left"> A <a href="#t_pointer">pointer</a> to a <a | |
| href="#t_function">function</a> that takes an <tt>i32*</tt>, returning an | |
| <tt>i32</tt>.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt>i32 addrspace(5)*</tt></td> | |
| <td class="left">A <a href="#t_pointer">pointer</a> to an <tt>i32</tt> value | |
| that resides in address space #5.</td> | |
| </tr> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_vector">Vector Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>A vector type is a simple derived type that represents a vector of elements. | |
| Vector types are used when multiple primitive data are operated in parallel | |
| using a single instruction (SIMD). A vector type requires a size (number of | |
| elements) and an underlying primitive data type. Vectors must have a power | |
| of two length (1, 2, 4, 8, 16 ...). Vector 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 | |
| integer or floating point type.</p> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"><tt><4 x i32></tt></td> | |
| <td class="left">Vector of 4 32-bit integer values.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt><8 x float></tt></td> | |
| <td class="left">Vector of 8 32-bit floating-point values.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt><2 x i64></tt></td> | |
| <td class="left">Vector of 2 64-bit integer values.</td> | |
| </tr> | |
| </table> | |
| <p>Note that the code generator does not yet support large vector types to be | |
| used as function return types. The specific limit on how large a vector | |
| return type codegen can currently handle is target-dependent; currently it's | |
| often a few times longer than a hardware vector register.</p> | |
| </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 forward 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.</td> | |
| </tr> | |
| </table> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="t_uprefs">Type Up-references</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>An "up reference" allows you to refer to a lexically enclosing type without | |
| requiring it to have a name. For instance, a structure declaration may | |
| contain a pointer to any of the types it is lexically a member of. Example | |
| of up references (with their equivalent as named type declarations) | |
| include:</p> | |
| <pre> | |
| { \2 * } %x = type { %x* } | |
| { \2 }* %y = type { %y }* | |
| \1* %z = type %z* | |
| </pre> | |
| <p>An up reference is needed by the asmprinter for printing out cyclic types | |
| when there is no declared name for a type in the cycle. Because the | |
| asmprinter does not want to print out an infinite type string, it needs a | |
| syntax to handle recursive types that have no names (all names are optional | |
| in llvm IR).</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| \<level> | |
| </pre> | |
| <p>The level is the count of the lexical type that is being referred to.</p> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"><tt>\1*</tt></td> | |
| <td class="left">Self-referential pointer.</td> | |
| </tr> | |
| <tr class="layout"> | |
| <td class="left"><tt>{ { \3*, i8 }, i32 }</tt></td> | |
| <td class="left">Recursive structure where the upref refers to the out-most | |
| structure.</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">i1</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 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). The assembler requires the exact decimal value of a | |
| floating-point constant. For example, the assembler accepts 1.25 but | |
| rejects 1.3 because 1.3 is a repeating decimal in binary. 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 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 in a reasonable number of | |
| digits. 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> | |
| <p>When using the hexadecimal form, constants of types float and double are | |
| represented using the 16-digit form shown above (which matches the IEEE754 | |
| representation for double); float values must, however, be exactly | |
| representable as IEE754 single precision. Hexadecimal format is always used | |
| for long double, and there are three forms of long double. The 80-bit format | |
| used by x86 is represented as <tt>0xK</tt> followed by 20 hexadecimal digits. | |
| The 128-bit format used by PowerPC (two adjacent doubles) is represented | |
| by <tt>0xM</tt> followed by 32 hexadecimal digits. The IEEE 128-bit format | |
| is represented by <tt>0xL</tt> followed by 32 hexadecimal digits; no | |
| currently supported target uses this format. Long doubles will only work if | |
| they match the long double format on your target. All hexadecimal formats | |
| are big-endian (sign bit at the left).</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="aggregateconstants"></a> <!-- old anchor --> | |
| <a name="complexconstants">Complex Constants</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Complex constants are a (potentially recursive) combination of simple | |
| constants and smaller complex 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>{ i32 4, float 17.0, i32* @G }</tt>", | |
| where "<tt>@G</tt>" is declared as "<tt>@G = external global i32</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>[ i32 42, i32 11, i32 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>Vector constants</b></dt> | |
| <dd>Vector constants are represented with notation similar to vector type | |
| definitions (a comma separated list of elements, surrounded by | |
| less-than/greater-than's (<tt><></tt>)). For example: "<tt>< i32 | |
| 42, i32 11, i32 74, i32 100 ></tt>". Vector constants must | |
| have <a href="#t_vector">vector 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> | |
| <dt><b>Metadata node</b></dt> | |
| <dd>A metadata node is a structure-like constant with | |
| <a href="#t_metadata">metadata type</a>. For example: "<tt>metadata !{ | |
| i32 0, metadata !"test" }</tt>". Unlike other constants that are meant to | |
| be interpreted as part of the instruction stream, metadata is a place to | |
| attach additional information such as debug info.</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> | |
| <div class="doc_code"> | |
| <pre> | |
| @X = global i32 17 | |
| @Y = global i32 42 | |
| @Z = global [2 x i32*] [ i32* @X, i32* @Y ] | |
| </pre> | |
| </div> | |
| </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>trunc ( CST to TYPE )</tt></b></dt> | |
| <dd>Truncate a constant to another type. The bit size of CST must be larger | |
| than the bit size of TYPE. Both types must be integers.</dd> | |
| <dt><b><tt>zext ( CST to TYPE )</tt></b></dt> | |
| <dd>Zero extend a constant to another type. The bit size of CST must be | |
| smaller or equal to the bit size of TYPE. Both types must be | |
| integers.</dd> | |
| <dt><b><tt>sext ( CST to TYPE )</tt></b></dt> | |
| <dd>Sign extend a constant to another type. The bit size of CST must be | |
| smaller or equal to the bit size of TYPE. Both types must be | |
| integers.</dd> | |
| <dt><b><tt>fptrunc ( CST to TYPE )</tt></b></dt> | |
| <dd>Truncate a floating point constant to another floating point type. The | |
| size of CST must be larger than the size of TYPE. Both types must be | |
| floating point.</dd> | |
| <dt><b><tt>fpext ( CST to TYPE )</tt></b></dt> | |
| <dd>Floating point extend a constant to another type. The size of CST must be | |
| smaller or equal to the size of TYPE. Both types must be floating | |
| point.</dd> | |
| <dt><b><tt>fptoui ( CST to TYPE )</tt></b></dt> | |
| <dd>Convert a floating point constant to the corresponding unsigned integer | |
| constant. TYPE must be a scalar or vector integer type. CST must be of | |
| scalar or vector floating point type. Both CST and TYPE must be scalars, | |
| or vectors of the same number of elements. If the value won't fit in the | |
| integer type, the results are undefined.</dd> | |
| <dt><b><tt>fptosi ( CST to TYPE )</tt></b></dt> | |
| <dd>Convert a floating point constant to the corresponding signed integer | |
| constant. TYPE must be a scalar or vector integer type. CST must be of | |
| scalar or vector floating point type. Both CST and TYPE must be scalars, | |
| or vectors of the same number of elements. If the value won't fit in the | |
| integer type, the results are undefined.</dd> | |
| <dt><b><tt>uitofp ( CST to TYPE )</tt></b></dt> | |
| <dd>Convert an unsigned integer constant to the corresponding floating point | |
| constant. TYPE must be a scalar or vector floating point type. CST must be | |
| of scalar or vector integer type. Both CST and TYPE must be scalars, or | |
| vectors of the same number of elements. If the value won't fit in the | |
| floating point type, the results are undefined.</dd> | |
| <dt><b><tt>sitofp ( CST to TYPE )</tt></b></dt> | |
| <dd>Convert a signed integer constant to the corresponding floating point | |
| constant. TYPE must be a scalar or vector floating point type. CST must be | |
| of scalar or vector integer type. Both CST and TYPE must be scalars, or | |
| vectors of the same number of elements. If the value won't fit in the | |
| floating point type, the results are undefined.</dd> | |
| <dt><b><tt>ptrtoint ( CST to TYPE )</tt></b></dt> | |
| <dd>Convert a pointer typed constant to the corresponding integer constant | |
| <tt>TYPE</tt> must be an integer type. <tt>CST</tt> must be of pointer | |
| type. The <tt>CST</tt> value is zero extended, truncated, or unchanged to | |
| make it fit in <tt>TYPE</tt>.</dd> | |
| <dt><b><tt>inttoptr ( CST to TYPE )</tt></b></dt> | |
| <dd>Convert a integer constant to a pointer constant. TYPE must be a pointer | |
| type. CST must be of integer type. The CST value is zero extended, | |
| truncated, or unchanged to make it fit in a pointer size. This one is | |
| <i>really</i> dangerous!</dd> | |
| <dt><b><tt>bitcast ( CST to TYPE )</tt></b></dt> | |
| <dd>Convert a constant, CST, to another TYPE. The constraints of the operands | |
| are the same as those for the <a href="#i_bitcast">bitcast | |
| instruction</a>.</dd> | |
| <dt><b><tt>getelementptr ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt> | |
| <dt><b><tt>getelementptr inbounds ( 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>select ( COND, VAL1, VAL2 )</tt></b></dt> | |
| <dd>Perform the <a href="#i_select">select operation</a> on constants.</dd> | |
| <dt><b><tt>icmp COND ( VAL1, VAL2 )</tt></b></dt> | |
| <dd>Performs the <a href="#i_icmp">icmp operation</a> on constants.</dd> | |
| <dt><b><tt>fcmp COND ( VAL1, VAL2 )</tt></b></dt> | |
| <dd>Performs the <a href="#i_fcmp">fcmp operation</a> on constants.</dd> | |
| <dt><b><tt>extractelement ( VAL, IDX )</tt></b></dt> | |
| <dd>Perform the <a href="#i_extractelement">extractelement operation</a> on | |
| constants.</dd> | |
| <dt><b><tt>insertelement ( VAL, ELT, IDX )</tt></b></dt> | |
| <dd>Perform the <a href="#i_insertelement">insertelement operation</a> on | |
| constants.</dd> | |
| <dt><b><tt>shufflevector ( VEC1, VEC2, IDXMASK )</tt></b></dt> | |
| <dd>Perform the <a href="#i_shufflevector">shufflevector operation</a> on | |
| constants.</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_subsection"><a name="metadata">Embedded Metadata</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Embedded metadata provides a way to attach arbitrary data to the instruction | |
| stream without affecting the behaviour of the program. There are two | |
| metadata primitives, strings and nodes. All metadata has the | |
| <tt>metadata</tt> type and is identified in syntax by a preceding exclamation | |
| point ('<tt>!</tt>').</p> | |
| <p>A metadata string is a string surrounded by double quotes. It can contain | |
| any character by escaping non-printable characters with "\xx" where "xx" is | |
| the two digit hex code. For example: "<tt>!"test\00"</tt>".</p> | |
| <p>Metadata nodes are represented with notation similar to structure constants | |
| (a comma separated list of elements, surrounded by braces and preceeded by an | |
| exclamation point). For example: "<tt>!{ metadata !"test\00", i32 | |
| 10}</tt>".</p> | |
| <p>A metadata node will attempt to track changes to the values it holds. In the | |
| event that a value is deleted, it will be replaced with a typeless | |
| "<tt>null</tt>", such as "<tt>metadata !{null, i32 10}</tt>".</p> | |
| <p>Optimizations may rely on metadata to provide additional information about | |
| the program that isn't available in the instructions, or that isn't easily | |
| computable. Similarly, the code generator may expect a certain metadata | |
| format to be used to express debugging information.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="othervalues">Other Values</a> </div> | |
| <!-- *********************************************************************** --> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="inlineasm">Inline Assembler Expressions</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM supports inline assembler expressions (as opposed | |
| to <a href="#moduleasm"> Module-Level Inline Assembly</a>) through the use of | |
| a special value. This value represents the inline assembler as a string | |
| (containing the instructions to emit), a list of operand constraints (stored | |
| as a string), and a flag that indicates whether or not the inline asm | |
| expression has side effects. An example inline assembler expression is:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| i32 (i32) asm "bswap $0", "=r,r" | |
| </pre> | |
| </div> | |
| <p>Inline assembler expressions may <b>only</b> be used as the callee operand of | |
| a <a href="#i_call"><tt>call</tt> instruction</a>. Thus, typically we | |
| have:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| %X = call i32 asm "<a href="#int_bswap">bswap</a> $0", "=r,r"(i32 %Y) | |
| </pre> | |
| </div> | |
| <p>Inline asms with side effects not visible in the constraint list must be | |
| marked as having side effects. This is done through the use of the | |
| '<tt>sideeffect</tt>' keyword, like so:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| call void asm sideeffect "eieio", ""() | |
| </pre> | |
| </div> | |
| <p>TODO: The format of the asm and constraints string still need to be | |
| documented here. Constraints on what can be done (e.g. duplication, moving, | |
| etc need to be documented). This is probably best done by reference to | |
| another document that covers inline asm from a holistic perspective.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> | |
| <a name="intrinsic_globals">Intrinsic Global Variables</a> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <p>LLVM has a number of "magic" global variables that contain data that affect | |
| code generation or other IR semantics. These are documented here. All globals | |
| of this sort should have a section specified as "<tt>llvm.metadata</tt>". This | |
| section and all globals that start with "<tt>llvm.</tt>" are reserved for use | |
| by LLVM.</p> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="intg_used">The '<tt>llvm.used</tt>' Global Variable</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>The <tt>@llvm.used</tt> global is an array with i8* element type which has <a | |
| href="#linkage_appending">appending linkage</a>. This array contains a list of | |
| pointers to global variables and functions which may optionally have a pointer | |
| cast formed of bitcast or getelementptr. For example, a legal use of it is:</p> | |
| <pre> | |
| @X = global i8 4 | |
| @Y = global i32 123 | |
| @llvm.used = appending global [2 x i8*] [ | |
| i8* @X, | |
| i8* bitcast (i32* @Y to i8*) | |
| ], section "llvm.metadata" | |
| </pre> | |
| <p>If a global variable appears in the <tt>@llvm.used</tt> list, then the | |
| compiler, assembler, and linker are required to treat the symbol as if there is | |
| a reference to the global that it cannot see. For example, if a variable has | |
| internal linkage and no references other than that from the <tt>@llvm.used</tt> | |
| list, it cannot be deleted. This is commonly used to represent references from | |
| inline asms and other things the compiler cannot "see", and corresponds to | |
| "attribute((used))" in GNU C.</p> | |
| <p>On some targets, the code generator must emit a directive to the assembler or | |
| object file to prevent the assembler and linker from molesting the symbol.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="intg_compiler_used">The '<tt>llvm.compiler.used</tt>' Global Variable</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>The <tt>@llvm.compiler.used</tt> directive is the same as the | |
| <tt>@llvm.used</tt> directive, except that it only prevents the compiler from | |
| touching the symbol. On targets that support it, this allows an intelligent | |
| linker to optimize references to the symbol without being impeded as it would be | |
| by <tt>@llvm.used</tt>.</p> | |
| <p>This is a rare construct that should only be used in rare circumstances, and | |
| should not be exposed to source languages.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="intg_global_ctors">The '<tt>llvm.global_ctors</tt>' Global Variable</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>TODO: Describe this.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="intg_global_dtors">The '<tt>llvm.global_dtors</tt>' Global Variable</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>TODO: Describe this.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="instref">Instruction Reference</a> </div> | |
| <!-- *********************************************************************** --> | |
| <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 optionally | |
| 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 optionally accepts a single argument, the | |
| return value. The type of the return value must be a | |
| '<a href="#t_firstclass">first class</a>' type.</p> | |
| <p>A function is not <a href="#wellformed">well formed</a> if it it has a | |
| non-void return type and contains a '<tt>ret</tt>' instruction with no return | |
| value or a return value with a type that does not match its type, or if it | |
| has a void return type and contains a '<tt>ret</tt>' instruction with a | |
| return value.</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 i32 5 <i>; Return an integer value of 5</i> | |
| ret void <i>; Return from a void function</i> | |
| ret { i32, i8 } { i32 4, i8 2 } <i>; Return a struct of values 4 and 2</i> | |
| </pre> | |
| <p>Note that the code generator does not yet fully support large | |
| return values. The specific sizes that are currently supported are | |
| dependent on the target. For integers, on 32-bit targets the limit | |
| is often 64 bits, and on 64-bit targets the limit is often 128 bits. | |
| For aggregate types, the current limits are dependent on the element | |
| types; for example targets are often limited to 2 total integer | |
| elements and 2 total floating-point elements.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_br">'<tt>br</tt>' Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| br i1 <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>i1</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>i1</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: | |
| %cond = <a href="#i_icmp">icmp</a> eq i32 %a, %b | |
| br i1 %cond, label %IfEqual, label %IfUnequal | |
| IfEqual: | |
| <a href="#i_ret">ret</a> i32 1 | |
| IfUnequal: | |
| <a href="#i_ret">ret</a> i32 0 | |
| </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_zext">zext</a> i1 %value to i32 | |
| switch i32 %Val, label %truedest [ i32 0, label %falsedest ] | |
| <i>; Emulate an unconditional br instruction</i> | |
| switch i32 0, label %dest [ ] | |
| <i>; Implement a jump table:</i> | |
| switch i32 %val, label %otherwise [ i32 0, label %onzero | |
| i32 1, label %onone | |
| i32 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>] [<a href="#paramattrs">ret attrs</a>] <ptr to function ty> <function ptr val>(<function args>) [<a href="#fnattrs">fn attrs</a>] | |
| to label <normal label> unwind 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>The optional <a href="#paramattrs">Parameter Attributes</a> list for | |
| return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and | |
| '<tt>inreg</tt>' attributes are valid here.</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> | |
| <li>The optional <a href="#fnattrs">function attributes</a> list. Only | |
| '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and | |
| '<tt>readnone</tt>' attributes are valid here.</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> | |
| <p>For the purposes of the SSA form, the definition of the value returned by the | |
| '<tt>invoke</tt>' instruction is deemed to occur on the edge from the current | |
| block to the "normal" label. If the callee unwinds then no return value is | |
| available.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %retval = invoke i32 @Test(i32 15) to label %Continue | |
| unwind label %TestCleanup <i>; {i32}:retval set</i> | |
| %retval = invoke <a href="#callingconv">coldcc</a> i32 %Testfnptr(i32 15) to label %Continue | |
| unwind label %TestCleanup <i>; {i32}: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>' instruction 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 of the same type, 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_vector">vector</a> data type. The result value | |
| has 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> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = add nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = add nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = add nuw nsw <ty> <op1>, <op2> <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 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of | |
| integer values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the integer sum of the two operands.</p> | |
| <p>If the sum has unsigned overflow, the result returned is the mathematical | |
| result modulo 2<sup>n</sup>, where n is the bit width of the result.</p> | |
| <p>Because LLVM integers use a two's complement representation, this instruction | |
| is appropriate for both signed and unsigned integers.</p> | |
| <p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap" | |
| and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or | |
| <tt>nsw</tt> keywords are present, the result value of the <tt>add</tt> | |
| is undefined if unsigned and/or signed overflow, respectively, occurs.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = add i32 4, %var <i>; yields {i32}:result = 4 + %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_fadd">'<tt>fadd</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = fadd <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>fadd</tt>' instruction returns the sum of its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>fadd</tt>' instruction must be | |
| <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of | |
| floating point values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the floating point sum of the two operands.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = fadd float 4.0, %var <i>; yields {float}:result = 4.0 + %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> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = sub nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = sub nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = sub nuw nsw <ty> <op1>, <op2> <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 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of | |
| integer values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the integer difference of the two operands.</p> | |
| <p>If the difference has unsigned overflow, the result returned is the | |
| mathematical result modulo 2<sup>n</sup>, where n is the bit width of the | |
| result.</p> | |
| <p>Because LLVM integers use a two's complement representation, this instruction | |
| is appropriate for both signed and unsigned integers.</p> | |
| <p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap" | |
| and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or | |
| <tt>nsw</tt> keywords are present, the result value of the <tt>sub</tt> | |
| is undefined if unsigned and/or signed overflow, respectively, occurs.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = sub i32 4, %var <i>; yields {i32}:result = 4 - %var</i> | |
| <result> = sub i32 0, %val <i>; yields {i32}:result = -%var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_fsub">'<tt>fsub</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = fsub <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>fsub</tt>' instruction returns the difference of its two | |
| operands.</p> | |
| <p>Note that the '<tt>fsub</tt>' instruction is used to represent the | |
| '<tt>fneg</tt>' instruction present in most other intermediate | |
| representations.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>fsub</tt>' instruction must be | |
| <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of | |
| floating point values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the floating point difference of the two operands.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = fsub float 4.0, %var <i>; yields {float}:result = 4.0 - %var</i> | |
| <result> = fsub float -0.0, %val <i>; yields {float}: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> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = mul nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = mul nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = mul nuw nsw <ty> <op1>, <op2> <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 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of | |
| integer values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the integer product of the two operands.</p> | |
| <p>If the result of the multiplication has unsigned overflow, the result | |
| returned is the mathematical result modulo 2<sup>n</sup>, where n is the bit | |
| width of the result.</p> | |
| <p>Because LLVM integers use a two's complement representation, and the result | |
| is the same width as the operands, this instruction returns the correct | |
| result for both signed and unsigned integers. If a full product | |
| (e.g. <tt>i32</tt>x<tt>i32</tt>-><tt>i64</tt>) is needed, the operands should | |
| be sign-extended or zero-extended as appropriate to the width of the full | |
| product.</p> | |
| <p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap" | |
| and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or | |
| <tt>nsw</tt> keywords are present, the result value of the <tt>mul</tt> | |
| is undefined if unsigned and/or signed overflow, respectively, occurs.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = mul i32 4, %var <i>; yields {i32}:result = 4 * %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_fmul">'<tt>fmul</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = fmul <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>fmul</tt>' instruction returns the product of its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>fmul</tt>' instruction must be | |
| <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of | |
| floating point values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the floating point product of the two operands.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = fmul float 4.0, %var <i>; yields {float}:result = 4.0 * %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_udiv">'<tt>udiv</tt>' Instruction | |
| </a></div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = udiv <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>udiv</tt>' instruction returns the quotient of its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>udiv</tt>' instruction must be | |
| <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer | |
| values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the unsigned integer quotient of the two operands.</p> | |
| <p>Note that unsigned integer division and signed integer division are distinct | |
| operations; for signed integer division, use '<tt>sdiv</tt>'.</p> | |
| <p>Division by zero leads to undefined behavior.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_sdiv">'<tt>sdiv</tt>' Instruction | |
| </a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = sdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| <result> = sdiv exact <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>sdiv</tt>' instruction returns the quotient of its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>sdiv</tt>' instruction must be | |
| <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer | |
| values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the signed integer quotient of the two operands rounded | |
| towards zero.</p> | |
| <p>Note that signed integer division and unsigned integer division are distinct | |
| operations; for unsigned integer division, use '<tt>udiv</tt>'.</p> | |
| <p>Division by zero leads to undefined behavior. Overflow also leads to | |
| undefined behavior; this is a rare case, but can occur, for example, by doing | |
| a 32-bit division of -2147483648 by -1.</p> | |
| <p>If the <tt>exact</tt> keyword is present, the result value of the | |
| <tt>sdiv</tt> is undefined if the result would be rounded or if overflow | |
| would occur.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = sdiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_fdiv">'<tt>fdiv</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = fdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>fdiv</tt>' instruction returns the quotient of its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>fdiv</tt>' instruction must be | |
| <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of | |
| floating point values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the floating point quotient of the two operands.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = fdiv float 4.0, %var <i>; yields {float}:result = 4.0 / %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_urem">'<tt>urem</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = urem <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>urem</tt>' instruction returns the remainder from the unsigned | |
| division of its two arguments.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>urem</tt>' instruction must be | |
| <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer | |
| values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>This instruction returns the unsigned integer <i>remainder</i> of a division. | |
| This instruction always performs an unsigned division to get the | |
| remainder.</p> | |
| <p>Note that unsigned integer remainder and signed integer remainder are | |
| distinct operations; for signed integer remainder, use '<tt>srem</tt>'.</p> | |
| <p>Taking the remainder of a division by zero leads to undefined behavior.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = urem i32 4, %var <i>; yields {i32}:result = 4 % %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_srem">'<tt>srem</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = srem <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>srem</tt>' instruction returns the remainder from the signed | |
| division of its two operands. This instruction can also take | |
| <a href="#t_vector">vector</a> versions of the values in which case the | |
| elements must be integers.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>srem</tt>' instruction must be | |
| <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer | |
| values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>This instruction returns the <i>remainder</i> of a division (where the result | |
| has the same sign as the dividend, <tt>op1</tt>), not the <i>modulo</i> | |
| operator (where the result has the same sign as the divisor, <tt>op2</tt>) 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>. For a table of how this is implemented in various languages, | |
| please see <a href="http://en.wikipedia.org/wiki/Modulo_operation"> | |
| Wikipedia: modulo operation</a>.</p> | |
| <p>Note that signed integer remainder and unsigned integer remainder are | |
| distinct operations; for unsigned integer remainder, use '<tt>urem</tt>'.</p> | |
| <p>Taking the remainder of a division by zero leads to undefined behavior. | |
| Overflow also leads to undefined behavior; this is a rare case, but can | |
| occur, for example, by taking the remainder of a 32-bit division of | |
| -2147483648 by -1. (The remainder doesn't actually overflow, but this rule | |
| lets srem be implemented using instructions that return both the result of | |
| the division and the remainder.)</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = srem i32 4, %var <i>; yields {i32}:result = 4 % %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_frem">'<tt>frem</tt>' Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = frem <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>frem</tt>' instruction returns the remainder from the division of | |
| its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>frem</tt>' instruction must be | |
| <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of | |
| floating point values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>This instruction returns the <i>remainder</i> of a division. The remainder | |
| has the same sign as the dividend.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = frem float 4.0, %var <i>; yields {float}:result = 4.0 % %var</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 of the | |
| same type, execute an operation on them, and produce a single value. The | |
| resulting value is the same type as its operands.</p> | |
| </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> <op1>, <op2> <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>Both arguments to the '<tt>shl</tt>' instruction must be the | |
| same <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of | |
| integer type. '<tt>op2</tt>' is treated as an unsigned value.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is <tt>op1</tt> * 2<sup><tt>op2</tt></sup> mod | |
| 2<sup>n</sup>, where <tt>n</tt> is the width of the result. If <tt>op2</tt> | |
| is (statically or dynamically) negative or equal to or larger than the number | |
| of bits in <tt>op1</tt>, the result is undefined. If the arguments are | |
| vectors, each vector element of <tt>op1</tt> is shifted by the corresponding | |
| shift amount in <tt>op2</tt>.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = shl i32 4, %var <i>; yields {i32}: 4 << %var</i> | |
| <result> = shl i32 4, 2 <i>; yields {i32}: 16</i> | |
| <result> = shl i32 1, 10 <i>; yields {i32}: 1024</i> | |
| <result> = shl i32 1, 32 <i>; undefined</i> | |
| <result> = shl <2 x i32> < i32 1, i32 1>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 2, i32 4></i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_lshr">'<tt>lshr</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = lshr <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>lshr</tt>' instruction (logical shift right) returns the first | |
| operand shifted to the right a specified number of bits with zero fill.</p> | |
| <h5>Arguments:</h5> | |
| <p>Both arguments to the '<tt>lshr</tt>' instruction must be the same | |
| <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer | |
| type. '<tt>op2</tt>' is treated as an unsigned value.</p> | |
| <h5>Semantics:</h5> | |
| <p>This instruction always performs a logical shift right operation. The most | |
| significant bits of the result will be filled with zero bits after the shift. | |
| If <tt>op2</tt> is (statically or dynamically) equal to or larger than the | |
| number of bits in <tt>op1</tt>, the result is undefined. If the arguments are | |
| vectors, each vector element of <tt>op1</tt> is shifted by the corresponding | |
| shift amount in <tt>op2</tt>.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = lshr i32 4, 1 <i>; yields {i32}:result = 2</i> | |
| <result> = lshr i32 4, 2 <i>; yields {i32}:result = 1</i> | |
| <result> = lshr i8 4, 3 <i>; yields {i8}:result = 0</i> | |
| <result> = lshr i8 -2, 1 <i>; yields {i8}:result = 0x7FFFFFFF </i> | |
| <result> = lshr i32 1, 32 <i>; undefined</i> | |
| <result> = lshr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 0x7FFFFFFF, i32 1></i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_ashr">'<tt>ashr</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = ashr <ty> <op1>, <op2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>ashr</tt>' instruction (arithmetic shift right) returns the first | |
| operand shifted to the right a specified number of bits with sign | |
| extension.</p> | |
| <h5>Arguments:</h5> | |
| <p>Both arguments to the '<tt>ashr</tt>' instruction must be the same | |
| <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer | |
| type. '<tt>op2</tt>' is treated as an unsigned value.</p> | |
| <h5>Semantics:</h5> | |
| <p>This instruction always performs an arithmetic shift right operation, The | |
| most significant bits of the result will be filled with the sign bit | |
| of <tt>op1</tt>. If <tt>op2</tt> is (statically or dynamically) equal to or | |
| larger than the number of bits in <tt>op1</tt>, the result is undefined. If | |
| the arguments are vectors, each vector element of <tt>op1</tt> is shifted by | |
| the corresponding shift amount in <tt>op2</tt>.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = ashr i32 4, 1 <i>; yields {i32}:result = 2</i> | |
| <result> = ashr i32 4, 2 <i>; yields {i32}:result = 1</i> | |
| <result> = ashr i8 4, 3 <i>; yields {i8}:result = 0</i> | |
| <result> = ashr i8 -2, 1 <i>; yields {i8}:result = -1</i> | |
| <result> = ashr i32 1, 32 <i>; undefined</i> | |
| <result> = ashr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 3> <i>; yields: result=<2 x i32> < i32 -1, i32 0></i> | |
| </pre> | |
| </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> <op1>, <op2> <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_integer">integer</a> or <a href="#t_vector">vector</a> of integer | |
| values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The truth table used for the '<tt>and</tt>' instruction is:</p> | |
| <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> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = and i32 4, %var <i>; yields {i32}:result = 4 & %var</i> | |
| <result> = and i32 15, 40 <i>; yields {i32}:result = 8</i> | |
| <result> = and i32 4, 8 <i>; yields {i32}: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> <op1>, <op2> <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_integer">integer</a> or <a href="#t_vector">vector</a> of integer | |
| values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The truth table used for the '<tt>or</tt>' instruction is:</p> | |
| <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> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = or i32 4, %var <i>; yields {i32}:result = 4 | %var</i> | |
| <result> = or i32 15, 40 <i>; yields {i32}:result = 47</i> | |
| <result> = or i32 4, 8 <i>; yields {i32}: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> <op1>, <op2> <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_integer">integer</a> or <a href="#t_vector">vector</a> of integer | |
| values. Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The truth table used for the '<tt>xor</tt>' instruction is:</p> | |
| <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> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = xor i32 4, %var <i>; yields {i32}:result = 4 ^ %var</i> | |
| <result> = xor i32 15, 40 <i>; yields {i32}:result = 39</i> | |
| <result> = xor i32 4, 8 <i>; yields {i32}:result = 12</i> | |
| <result> = xor i32 %V, -1 <i>; yields {i32}:result = ~%V</i> | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="vectorops">Vector Operations</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM supports several instructions to represent vector operations in a | |
| target-independent manner. These instructions cover the element-access and | |
| vector-specific operations needed to process vectors effectively. While LLVM | |
| does directly support these vector operations, many sophisticated algorithms | |
| will want to use target-specific intrinsics to take full advantage of a | |
| specific target.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>extractelement</tt>' instruction extracts a single scalar element | |
| from a vector at a specified index.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first operand of an '<tt>extractelement</tt>' instruction is a value | |
| of <a href="#t_vector">vector</a> type. The second operand is an index | |
| indicating the position from which to extract the element. The index may be | |
| a variable.</p> | |
| <h5>Semantics:</h5> | |
| <p>The result is a scalar of the same type as the element type of | |
| <tt>val</tt>. Its value is the value at position <tt>idx</tt> of | |
| <tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the | |
| results are undefined.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %result = extractelement <4 x i32> %vec, i32 0 <i>; yields i32</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>insertelement</tt>' instruction inserts a scalar element into a | |
| vector at a specified index.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first operand of an '<tt>insertelement</tt>' instruction is a value | |
| of <a href="#t_vector">vector</a> type. The second operand is a scalar value | |
| whose type must equal the element type of the first operand. The third | |
| operand is an index indicating the position at which to insert the value. | |
| The index may be a variable.</p> | |
| <h5>Semantics:</h5> | |
| <p>The result is a vector of the same type as <tt>val</tt>. Its element values | |
| are those of <tt>val</tt> except at position <tt>idx</tt>, where it gets the | |
| value <tt>elt</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the | |
| results are undefined.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %result = insertelement <4 x i32> %vec, i32 1, i32 0 <i>; yields <4 x i32></i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <m x i32> <mask> <i>; yields <m x <ty>></i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>shufflevector</tt>' instruction constructs a permutation of elements | |
| from two input vectors, returning a vector with the same element type as the | |
| input and length that is the same as the shuffle mask.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first two operands of a '<tt>shufflevector</tt>' instruction are vectors | |
| with types that match each other. The third argument is a shuffle mask whose | |
| element type is always 'i32'. The result of the instruction is a vector | |
| whose length is the same as the shuffle mask and whose element type is the | |
| same as the element type of the first two operands.</p> | |
| <p>The shuffle mask operand is required to be a constant vector with either | |
| constant integer or undef values.</p> | |
| <h5>Semantics:</h5> | |
| <p>The elements of the two input vectors are numbered from left to right across | |
| both of the vectors. The shuffle mask operand specifies, for each element of | |
| the result vector, which element of the two input vectors the result element | |
| gets. The element selector may be undef (meaning "don't care") and the | |
| second operand may be undef if performing a shuffle from only one vector.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %result = shufflevector <4 x i32> %v1, <4 x i32> %v2, | |
| <4 x i32> <i32 0, i32 4, i32 1, i32 5> <i>; yields <4 x i32></i> | |
| %result = shufflevector <4 x i32> %v1, <4 x i32> undef, | |
| <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle. | |
| %result = shufflevector <8 x i32> %v1, <8 x i32> undef, | |
| <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> | |
| %result = shufflevector <4 x i32> %v1, <4 x i32> %v2, | |
| <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7 > <i>; yields <8 x i32></i> | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="aggregateops">Aggregate Operations</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM supports several instructions for working with aggregate values.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_extractvalue">'<tt>extractvalue</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = extractvalue <aggregate type> <val>, <idx>{, <idx>}* | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>extractvalue</tt>' instruction extracts the value of a struct field | |
| or array element from an aggregate value.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first operand of an '<tt>extractvalue</tt>' instruction is a value | |
| of <a href="#t_struct">struct</a> or <a href="#t_array">array</a> type. The | |
| operands are constant indices to specify which value to extract in a similar | |
| manner as indices in a | |
| '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.</p> | |
| <h5>Semantics:</h5> | |
| <p>The result is the value at the position in the aggregate specified by the | |
| index operands.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %result = extractvalue {i32, float} %agg, 0 <i>; yields i32</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_insertvalue">'<tt>insertvalue</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = insertvalue <aggregate type> <val>, <ty> <val>, <idx> <i>; yields <n x <ty>></i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>insertvalue</tt>' instruction inserts a value into a struct field or | |
| array element in an aggregate.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first operand of an '<tt>insertvalue</tt>' instruction is a value | |
| of <a href="#t_struct">struct</a> or <a href="#t_array">array</a> type. The | |
| second operand is a first-class value to insert. The following operands are | |
| constant indices indicating the position at which to insert the value in a | |
| similar manner as indices in a | |
| '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction. The | |
| value to insert must have the same type as the value identified by the | |
| indices.</p> | |
| <h5>Semantics:</h5> | |
| <p>The result is an aggregate of the same type as <tt>val</tt>. Its value is | |
| that of <tt>val</tt> except that the value at the position specified by the | |
| indices is that of <tt>elt</tt>.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %result = insertvalue {i32, float} %agg, i32 1, 0 <i>; yields {i32, float}</i> | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="memoryops">Memory Access and Addressing 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>[, i32 <NumElements>][, align <alignment>] <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. The object is always allocated in the generic | |
| address space (address space zero).</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. If | |
| "NumElements" is specified, it is the number of elements allocated, otherwise | |
| "NumElements" is defaulted to be one. If a constant alignment is specified, | |
| the value result of the allocation is guaranteed to be aligned to at least | |
| that boundary. If not specified, or if zero, the target can choose to align | |
| the allocation on any convenient boundary compatible with the type.</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. The result of a zero byte allocation is undefined. The | |
| result is null if there is insufficient memory available.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %array = malloc [4 x i8] <i>; yields {[%4 x i8]*}:array</i> | |
| %size = <a href="#i_add">add</a> i32 2, 2 <i>; yields {i32}:size = i32 4</i> | |
| %array1 = malloc i8, i32 4 <i>; yields {i8*}:array1</i> | |
| %array2 = malloc [12 x i8], i32 %size <i>; yields {[12 x i8]*}:array2</i> | |
| %array3 = malloc i32, i32 4, align 1024 <i>; yields {i32*}:array3</i> | |
| %array4 = malloc i32, align 1024 <i>; yields {i32*}:array4</i> | |
| </pre> | |
| <p>Note that the code generator does not yet respect the alignment value.</p> | |
| </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> | |
| <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. If the pointer is null, the operation is a | |
| noop.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %array = <a href="#i_malloc">malloc</a> [4 x i8] <i>; yields {[4 x i8]*}:array</i> | |
| free [4 x i8]* %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>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>alloca</tt>' instruction allocates memory on the stack frame of the | |
| currently executing function, to be automatically released when this function | |
| returns to its caller. The object is always allocated in the generic address | |
| space (address space zero).</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. | |
| If "NumElements" is specified, it is the number of elements allocated, | |
| otherwise "NumElements" is defaulted to be one. If a constant alignment is | |
| specified, the value result of the allocation is guaranteed to be aligned to | |
| at least that boundary. If not specified, or if zero, the target can choose | |
| to align the allocation on any convenient boundary compatible with the | |
| type.</p> | |
| <p>'<tt>type</tt>' may be any sized type.</p> | |
| <h5>Semantics:</h5> | |
| <p>Memory is allocated; a pointer is returned. The operation is undefined if | |
| there is insufficient stack space for the allocation. '<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. Allocating zero bytes is legal, but the result is undefined.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %ptr = alloca i32 <i>; yields {i32*}:ptr</i> | |
| %ptr = alloca i32, i32 4 <i>; yields {i32*}:ptr</i> | |
| %ptr = alloca i32, i32 4, align 1024 <i>; yields {i32*}:ptr</i> | |
| %ptr = alloca i32, align 1024 <i>; yields {i32*}: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>[, align <alignment>] | |
| <result> = volatile load <ty>* <pointer>[, align <alignment>] | |
| </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 | |
| from which to load. 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> | |
| <p>The optional constant "align" argument specifies the alignment of the | |
| operation (that is, the alignment of the memory address). A value of 0 or an | |
| omitted "align" argument means that the operation has the preferential | |
| alignment for the target. It is the responsibility of the code emitter to | |
| ensure that the alignment information is correct. Overestimating the | |
| alignment results in an undefined behavior. Underestimating the alignment may | |
| produce less efficient code. An alignment of 1 is always safe.</p> | |
| <h5>Semantics:</h5> | |
| <p>The location of memory pointed to is loaded. If the value being loaded is of | |
| scalar type then the number of bytes read does not exceed the minimum number | |
| of bytes needed to hold all bits of the type. For example, loading an | |
| <tt>i24</tt> reads at most three bytes. When loading a value of a type like | |
| <tt>i20</tt> with a size that is not an integral number of bytes, the result | |
| is undefined if the value was not originally written using a store of the | |
| same type.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i> | |
| <a href="#i_store">store</a> i32 3, i32* %ptr <i>; yields {void}</i> | |
| %val = load i32* %ptr <i>; yields {i32}:val = i32 3</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_store">'<tt>store</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i> | |
| volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>] <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 at which to store it. The type of the | |
| '<tt><pointer></tt>' operand must be a pointer to | |
| the <a href="#t_firstclass">first class</a> 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> | |
| <p>The optional constant "align" argument specifies the alignment of the | |
| operation (that is, the alignment of the memory address). A value of 0 or an | |
| omitted "align" argument means that the operation has the preferential | |
| alignment for the target. It is the responsibility of the code emitter to | |
| ensure that the alignment information is correct. Overestimating the | |
| alignment results in an undefined behavior. Underestimating the alignment may | |
| produce less efficient code. An alignment of 1 is always safe.</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. If | |
| '<tt><value></tt>' is of scalar type then the number of bytes written | |
| does not exceed the minimum number of bytes needed to hold all bits of the | |
| type. For example, storing an <tt>i24</tt> writes at most three bytes. When | |
| writing a value of a type like <tt>i20</tt> with a size that is not an | |
| integral number of bytes, it is unspecified what happens to the extra bits | |
| that do not belong to the type, but they will typically be overwritten.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i> | |
| store i32 3, i32* %ptr <i>; yields {void}</i> | |
| %val = <a href="#i_load">load</a> i32* %ptr <i>; yields {i32}:val = i32 3</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = getelementptr <pty>* <ptrval>{, <ty> <idx>}* | |
| <result> = getelementptr inbounds <pty>* <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. It performs address calculation | |
| only and does not access memory.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first argument is always a pointer, and forms the basis of the | |
| calculation. The remaining arguments are indices that indicate which of the | |
| elements of the aggregate object are indexed. The interpretation of each | |
| index is dependent on the type being indexed into. The first index always | |
| indexes the pointer value given as the first argument, the second index | |
| indexes a value of the type pointed to (not necessarily the value directly | |
| pointed to, since the first index can be non-zero), etc. The first type | |
| indexed into must be a pointer value, subsequent types can be arrays, vectors | |
| and structs. Note that subsequent types being indexed into can never be | |
| pointers, since that would require loading the pointer before continuing | |
| calculation.</p> | |
| <p>The type of each index argument depends on the type it is indexing into. | |
| When indexing into a (optionally packed) structure, only <tt>i32</tt> integer | |
| <b>constants</b> are allowed. When indexing into an array, pointer or | |
| vector, integers of any width are allowed, and they are not required to be | |
| constant.</p> | |
| <p>For example, let's consider a C code fragment and how it gets compiled to | |
| LLVM:</p> | |
| <div class="doc_code"> | |
| <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> | |
| </div> | |
| <p>The LLVM code generated by the GCC frontend is:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| %RT = <a href="#namedtypes">type</a> { i8 , [10 x [20 x i32]], i8 } | |
| %ST = <a href="#namedtypes">type</a> { i32, double, %RT } | |
| define i32* @foo(%ST* %s) { | |
| entry: | |
| %reg = getelementptr %ST* %s, i32 1, i32 2, i32 1, i32 5, i32 13 | |
| ret i32* %reg | |
| } | |
| </pre> | |
| </div> | |
| <h5>Semantics:</h5> | |
| <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>{ i32, double, %RT | |
| }</tt>' type, a structure. The second index indexes into the third element | |
| of the structure, yielding a '<tt>%RT</tt>' = '<tt>{ i8 , [10 x [20 x i32]], | |
| i8 }</tt>' type, another structure. The third index indexes into the second | |
| element of the structure, yielding a '<tt>[10 x [20 x i32]]</tt>' type, an | |
| array. The two dimensions of the array are subscripted into, yielding an | |
| '<tt>i32</tt>' type. The '<tt>getelementptr</tt>' instruction returns a | |
| pointer to this element, thus computing a value of '<tt>i32*</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> | |
| define i32* @foo(%ST* %s) { | |
| %t1 = getelementptr %ST* %s, i32 1 <i>; yields %ST*:%t1</i> | |
| %t2 = getelementptr %ST* %t1, i32 0, i32 2 <i>; yields %RT*:%t2</i> | |
| %t3 = getelementptr %RT* %t2, i32 0, i32 1 <i>; yields [10 x [20 x i32]]*:%t3</i> | |
| %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 <i>; yields [20 x i32]*:%t4</i> | |
| %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 <i>; yields i32*:%t5</i> | |
| ret i32* %t5 | |
| } | |
| </pre> | |
| <p>If the <tt>inbounds</tt> keyword is present, the result value of the | |
| <tt>getelementptr</tt> is undefined if the base pointer is not an | |
| <i>in bounds</i> address of an allocated object, or if any of the addresses | |
| that would be formed by successive addition of the offsets implied by the | |
| indices to the base address with infinitely precise arithmetic are not an | |
| <i>in bounds</i> address of that allocated object. | |
| The <i>in bounds</i> addresses for an allocated object are all the addresses | |
| that point into the object, plus the address one byte past the end.</p> | |
| <p>If the <tt>inbounds</tt> keyword is not present, the offsets are added to | |
| the base address with silently-wrapping two's complement arithmetic, and | |
| the result value of the <tt>getelementptr</tt> may be outside the object | |
| pointed to by the base pointer. The result value may not necessarily be | |
| used to access memory though, even if it happens to point into allocated | |
| storage. See the <a href="#pointeraliasing">Pointer Aliasing Rules</a> | |
| section for more information.</p> | |
| <p>The getelementptr instruction is often confusing. For some more insight into | |
| how it works, see <a href="GetElementPtr.html">the getelementptr FAQ</a>.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <i>; yields [12 x i8]*:aptr</i> | |
| %aptr = getelementptr {i32, [12 x i8]}* %saptr, i64 0, i32 1 | |
| <i>; yields i8*:vptr</i> | |
| %vptr = getelementptr {i32, <2 x i8>}* %svptr, i64 0, i32 1, i32 1 | |
| <i>; yields i8*:eptr</i> | |
| %eptr = getelementptr [12 x i8]* %aptr, i64 0, i32 1 | |
| <i>; yields i32*:iptr</i> | |
| %iptr = getelementptr [10 x i32]* @arr, i16 0, i16 0 | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="convertops">Conversion Operations</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>The instructions in this category are the conversion instructions (casting) | |
| which all take a single operand and a type. They perform various bit | |
| conversions on the operand.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_trunc">'<tt>trunc .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = trunc <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>trunc</tt>' instruction truncates its operand to the | |
| type <tt>ty2</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>trunc</tt>' instruction takes a <tt>value</tt> to trunc, which must | |
| be an <a href="#t_integer">integer</a> type, and a type that specifies the | |
| size and type of the result, which must be | |
| an <a href="#t_integer">integer</a> type. The bit size of <tt>value</tt> must | |
| be larger than the bit size of <tt>ty2</tt>. Equal sized types are not | |
| allowed.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>trunc</tt>' instruction truncates the high order bits | |
| in <tt>value</tt> and converts the remaining bits to <tt>ty2</tt>. Since the | |
| source size must be larger than the destination size, <tt>trunc</tt> cannot | |
| be a <i>no-op cast</i>. It will always truncate bits.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = trunc i32 257 to i8 <i>; yields i8:1</i> | |
| %Y = trunc i32 123 to i1 <i>; yields i1:true</i> | |
| %Y = trunc i32 122 to i1 <i>; yields i1:false</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_zext">'<tt>zext .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = zext <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>zext</tt>' instruction zero extends its operand to type | |
| <tt>ty2</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>zext</tt>' instruction takes a value to cast, which must be of | |
| <a href="#t_integer">integer</a> type, and a type to cast it to, which must | |
| also be of <a href="#t_integer">integer</a> type. The bit size of the | |
| <tt>value</tt> must be smaller than the bit size of the destination type, | |
| <tt>ty2</tt>.</p> | |
| <h5>Semantics:</h5> | |
| <p>The <tt>zext</tt> fills the high order bits of the <tt>value</tt> with zero | |
| bits until it reaches the size of the destination type, <tt>ty2</tt>.</p> | |
| <p>When zero extending from i1, the result will always be either 0 or 1.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = zext i32 257 to i64 <i>; yields i64:257</i> | |
| %Y = zext i1 true to i32 <i>; yields i32:1</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_sext">'<tt>sext .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = sext <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>sext</tt>' sign extends <tt>value</tt> to the type <tt>ty2</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>sext</tt>' instruction takes a value to cast, which must be of | |
| <a href="#t_integer">integer</a> type, and a type to cast it to, which must | |
| also be of <a href="#t_integer">integer</a> type. The bit size of the | |
| <tt>value</tt> must be smaller than the bit size of the destination type, | |
| <tt>ty2</tt>.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>sext</tt>' instruction performs a sign extension by copying the sign | |
| bit (highest order bit) of the <tt>value</tt> until it reaches the bit size | |
| of the type <tt>ty2</tt>.</p> | |
| <p>When sign extending from i1, the extension always results in -1 or 0.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = sext i8 -1 to i16 <i>; yields i16 :65535</i> | |
| %Y = sext i1 true to i32 <i>; yields i32:-1</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = fptrunc <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>fptrunc</tt>' instruction truncates <tt>value</tt> to type | |
| <tt>ty2</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>fptrunc</tt>' instruction takes a <a href="#t_floating">floating | |
| point</a> value to cast and a <a href="#t_floating">floating point</a> type | |
| to cast it to. The size of <tt>value</tt> must be larger than the size of | |
| <tt>ty2</tt>. This implies that <tt>fptrunc</tt> cannot be used to make a | |
| <i>no-op cast</i>.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>fptrunc</tt>' instruction truncates a <tt>value</tt> from a larger | |
| <a href="#t_floating">floating point</a> type to a smaller | |
| <a href="#t_floating">floating point</a> type. If the value cannot fit | |
| within the destination type, <tt>ty2</tt>, then the results are | |
| undefined.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = fptrunc double 123.0 to float <i>; yields float:123.0</i> | |
| %Y = fptrunc double 1.0E+300 to float <i>; yields undefined</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_fpext">'<tt>fpext .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = fpext <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>fpext</tt>' extends a floating point <tt>value</tt> to a larger | |
| floating point value.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>fpext</tt>' instruction takes a | |
| <a href="#t_floating">floating point</a> <tt>value</tt> to cast, and | |
| a <a href="#t_floating">floating point</a> type to cast it to. The source | |
| type must be smaller than the destination type.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>fpext</tt>' instruction extends the <tt>value</tt> from a smaller | |
| <a href="#t_floating">floating point</a> type to a larger | |
| <a href="#t_floating">floating point</a> type. The <tt>fpext</tt> cannot be | |
| used to make a <i>no-op cast</i> because it always changes bits. Use | |
| <tt>bitcast</tt> to make a <i>no-op cast</i> for a floating point cast.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = fpext float 3.1415 to double <i>; yields double:3.1415</i> | |
| %Y = fpext float 1.0 to float <i>; yields float:1.0 (no-op)</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = fptoui <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>fptoui</tt>' converts a floating point <tt>value</tt> to its | |
| unsigned integer equivalent of type <tt>ty2</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>fptoui</tt>' instruction takes a value to cast, which must be a | |
| scalar or vector <a href="#t_floating">floating point</a> value, and a type | |
| to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> | |
| type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a | |
| vector integer type with the same number of elements as <tt>ty</tt></p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>fptoui</tt>' instruction converts its | |
| <a href="#t_floating">floating point</a> operand into the nearest (rounding | |
| towards zero) unsigned integer value. If the value cannot fit | |
| in <tt>ty2</tt>, the results are undefined.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = fptoui double 123.0 to i32 <i>; yields i32:123</i> | |
| %Y = fptoui float 1.0E+300 to i1 <i>; yields undefined:1</i> | |
| %X = fptoui float 1.04E+17 to i8 <i>; yields undefined:1</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = fptosi <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>fptosi</tt>' instruction converts | |
| <a href="#t_floating">floating point</a> <tt>value</tt> to | |
| type <tt>ty2</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>fptosi</tt>' instruction takes a value to cast, which must be a | |
| scalar or vector <a href="#t_floating">floating point</a> value, and a type | |
| to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> | |
| type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a | |
| vector integer type with the same number of elements as <tt>ty</tt></p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>fptosi</tt>' instruction converts its | |
| <a href="#t_floating">floating point</a> operand into the nearest (rounding | |
| towards zero) signed integer value. If the value cannot fit in <tt>ty2</tt>, | |
| the results are undefined.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = fptosi double -123.0 to i32 <i>; yields i32:-123</i> | |
| %Y = fptosi float 1.0E-247 to i1 <i>; yields undefined:1</i> | |
| %X = fptosi float 1.04E+17 to i8 <i>; yields undefined:1</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = uitofp <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>uitofp</tt>' instruction regards <tt>value</tt> as an unsigned | |
| integer and converts that value to the <tt>ty2</tt> type.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>uitofp</tt>' instruction takes a value to cast, which must be a | |
| scalar or vector <a href="#t_integer">integer</a> value, and a type to cast | |
| it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a> | |
| type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector | |
| floating point type with the same number of elements as <tt>ty</tt></p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>uitofp</tt>' instruction interprets its operand as an unsigned | |
| integer quantity and converts it to the corresponding floating point | |
| value. If the value cannot fit in the floating point value, the results are | |
| undefined.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = uitofp i32 257 to float <i>; yields float:257.0</i> | |
| %Y = uitofp i8 -1 to double <i>; yields double:255.0</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = sitofp <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>sitofp</tt>' instruction regards <tt>value</tt> as a signed integer | |
| and converts that value to the <tt>ty2</tt> type.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>sitofp</tt>' instruction takes a value to cast, which must be a | |
| scalar or vector <a href="#t_integer">integer</a> value, and a type to cast | |
| it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a> | |
| type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector | |
| floating point type with the same number of elements as <tt>ty</tt></p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>sitofp</tt>' instruction interprets its operand as a signed integer | |
| quantity and converts it to the corresponding floating point value. If the | |
| value cannot fit in the floating point value, the results are undefined.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = sitofp i32 257 to float <i>; yields float:257.0</i> | |
| %Y = sitofp i8 -1 to double <i>; yields double:-1.0</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = ptrtoint <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>ptrtoint</tt>' instruction converts the pointer <tt>value</tt> to | |
| the integer type <tt>ty2</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>ptrtoint</tt>' instruction takes a <tt>value</tt> to cast, which | |
| must be a <a href="#t_pointer">pointer</a> value, and a type to cast it to | |
| <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> type.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>ptrtoint</tt>' instruction converts <tt>value</tt> to integer type | |
| <tt>ty2</tt> by interpreting the pointer value as an integer and either | |
| truncating or zero extending that value to the size of the integer type. If | |
| <tt>value</tt> is smaller than <tt>ty2</tt> then a zero extension is done. If | |
| <tt>value</tt> is larger than <tt>ty2</tt> then a truncation is done. If they | |
| are the same size, then nothing is done (<i>no-op cast</i>) other than a type | |
| change.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = ptrtoint i32* %X to i8 <i>; yields truncation on 32-bit architecture</i> | |
| %Y = ptrtoint i32* %x to i64 <i>; yields zero extension on 32-bit architecture</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = inttoptr <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>inttoptr</tt>' instruction converts an integer <tt>value</tt> to a | |
| pointer type, <tt>ty2</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>inttoptr</tt>' instruction takes an <a href="#t_integer">integer</a> | |
| value to cast, and a type to cast it to, which must be a | |
| <a href="#t_pointer">pointer</a> type.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>inttoptr</tt>' instruction converts <tt>value</tt> to type | |
| <tt>ty2</tt> by applying either a zero extension or a truncation depending on | |
| the size of the integer <tt>value</tt>. If <tt>value</tt> is larger than the | |
| size of a pointer then a truncation is done. If <tt>value</tt> is smaller | |
| than the size of a pointer then a zero extension is done. If they are the | |
| same size, nothing is done (<i>no-op cast</i>).</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = inttoptr i32 255 to i32* <i>; yields zero extension on 64-bit architecture</i> | |
| %X = inttoptr i32 255 to i32* <i>; yields no-op on 32-bit architecture</i> | |
| %Y = inttoptr i64 0 to i32* <i>; yields truncation on 32-bit architecture</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = bitcast <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type | |
| <tt>ty2</tt> without changing any bits.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>bitcast</tt>' instruction takes a value to cast, which must be a | |
| non-aggregate first class value, and a type to cast it to, which must also be | |
| a non-aggregate <a href="#t_firstclass">first class</a> type. The bit sizes | |
| of <tt>value</tt> and the destination type, <tt>ty2</tt>, must be | |
| identical. If the source type is a pointer, the destination type must also be | |
| a pointer. This instruction supports bitwise conversion of vectors to | |
| integers and to vectors of other types (as long as they have the same | |
| size).</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type | |
| <tt>ty2</tt>. It is always a <i>no-op cast</i> because no bits change with | |
| this conversion. The conversion is done as if the <tt>value</tt> had been | |
| stored to memory and read back as type <tt>ty2</tt>. Pointer types may only | |
| be converted to other pointer types with this instruction. To convert | |
| pointers to other types, use the <a href="#i_inttoptr">inttoptr</a> or | |
| <a href="#i_ptrtoint">ptrtoint</a> instructions first.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = bitcast i8 255 to i8 <i>; yields i8 :-1</i> | |
| %Y = bitcast i32* %x to sint* <i>; yields sint*:%x</i> | |
| %Z = bitcast <2 x int> %V to i64; <i>; yields i64: %V</i> | |
| </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_icmp">'<tt>icmp</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = icmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>icmp</tt>' instruction returns a boolean value or a vector of | |
| boolean values based on comparison of its two integer, integer vector, or | |
| pointer operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>icmp</tt>' instruction takes three operands. The first operand is | |
| the condition code indicating the kind of comparison to perform. It is not a | |
| value, just a keyword. The possible condition code are:</p> | |
| <ol> | |
| <li><tt>eq</tt>: equal</li> | |
| <li><tt>ne</tt>: not equal </li> | |
| <li><tt>ugt</tt>: unsigned greater than</li> | |
| <li><tt>uge</tt>: unsigned greater or equal</li> | |
| <li><tt>ult</tt>: unsigned less than</li> | |
| <li><tt>ule</tt>: unsigned less or equal</li> | |
| <li><tt>sgt</tt>: signed greater than</li> | |
| <li><tt>sge</tt>: signed greater or equal</li> | |
| <li><tt>slt</tt>: signed less than</li> | |
| <li><tt>sle</tt>: signed less or equal</li> | |
| </ol> | |
| <p>The remaining two arguments must be <a href="#t_integer">integer</a> or | |
| <a href="#t_pointer">pointer</a> or integer <a href="#t_vector">vector</a> | |
| typed. They must also be identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>icmp</tt>' compares <tt>op1</tt> and <tt>op2</tt> according to the | |
| condition code given as <tt>cond</tt>. The comparison performed always yields | |
| either an <a href="#t_primitive"><tt>i1</tt></a> or vector of <tt>i1</tt> | |
| result, as follows:</p> | |
| <ol> | |
| <li><tt>eq</tt>: yields <tt>true</tt> if the operands are equal, | |
| <tt>false</tt> otherwise. No sign interpretation is necessary or | |
| performed.</li> | |
| <li><tt>ne</tt>: yields <tt>true</tt> if the operands are unequal, | |
| <tt>false</tt> otherwise. No sign interpretation is necessary or | |
| performed.</li> | |
| <li><tt>ugt</tt>: interprets the operands as unsigned values and yields | |
| <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li> | |
| <li><tt>uge</tt>: interprets the operands as unsigned values and yields | |
| <tt>true</tt> if <tt>op1</tt> is greater than or equal | |
| to <tt>op2</tt>.</li> | |
| <li><tt>ult</tt>: interprets the operands as unsigned values and yields | |
| <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li> | |
| <li><tt>ule</tt>: interprets the operands as unsigned values and yields | |
| <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> | |
| <li><tt>sgt</tt>: interprets the operands as signed values and yields | |
| <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li> | |
| <li><tt>sge</tt>: interprets the operands as signed values and yields | |
| <tt>true</tt> if <tt>op1</tt> is greater than or equal | |
| to <tt>op2</tt>.</li> | |
| <li><tt>slt</tt>: interprets the operands as signed values and yields | |
| <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li> | |
| <li><tt>sle</tt>: interprets the operands as signed values and yields | |
| <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> | |
| </ol> | |
| <p>If the operands are <a href="#t_pointer">pointer</a> typed, the pointer | |
| values are compared as if they were integers.</p> | |
| <p>If the operands are integer vectors, then they are compared element by | |
| element. The result is an <tt>i1</tt> vector with the same number of elements | |
| as the values being compared. Otherwise, the result is an <tt>i1</tt>.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = icmp eq i32 4, 5 <i>; yields: result=false</i> | |
| <result> = icmp ne float* %X, %X <i>; yields: result=false</i> | |
| <result> = icmp ult i16 4, 5 <i>; yields: result=true</i> | |
| <result> = icmp sgt i16 4, 5 <i>; yields: result=false</i> | |
| <result> = icmp ule i16 -4, 5 <i>; yields: result=false</i> | |
| <result> = icmp sge i16 4, 5 <i>; yields: result=false</i> | |
| </pre> | |
| <p>Note that the code generator does not yet support vector types with | |
| the <tt>icmp</tt> instruction.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"><a name="i_fcmp">'<tt>fcmp</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = fcmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>fcmp</tt>' instruction returns a boolean value or vector of boolean | |
| values based on comparison of its operands.</p> | |
| <p>If the operands are floating point scalars, then the result type is a boolean | |
| (<a href="#t_primitive"><tt>i1</tt></a>).</p> | |
| <p>If the operands are floating point vectors, then the result type is a vector | |
| of boolean with the same number of elements as the operands being | |
| compared.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>fcmp</tt>' instruction takes three operands. The first operand is | |
| the condition code indicating the kind of comparison to perform. It is not a | |
| value, just a keyword. The possible condition code are:</p> | |
| <ol> | |
| <li><tt>false</tt>: no comparison, always returns false</li> | |
| <li><tt>oeq</tt>: ordered and equal</li> | |
| <li><tt>ogt</tt>: ordered and greater than </li> | |
| <li><tt>oge</tt>: ordered and greater than or equal</li> | |
| <li><tt>olt</tt>: ordered and less than </li> | |
| <li><tt>ole</tt>: ordered and less than or equal</li> | |
| <li><tt>one</tt>: ordered and not equal</li> | |
| <li><tt>ord</tt>: ordered (no nans)</li> | |
| <li><tt>ueq</tt>: unordered or equal</li> | |
| <li><tt>ugt</tt>: unordered or greater than </li> | |
| <li><tt>uge</tt>: unordered or greater than or equal</li> | |
| <li><tt>ult</tt>: unordered or less than </li> | |
| <li><tt>ule</tt>: unordered or less than or equal</li> | |
| <li><tt>une</tt>: unordered or not equal</li> | |
| <li><tt>uno</tt>: unordered (either nans)</li> | |
| <li><tt>true</tt>: no comparison, always returns true</li> | |
| </ol> | |
| <p><i>Ordered</i> means that neither operand is a QNAN while | |
| <i>unordered</i> means that either operand may be a QNAN.</p> | |
| <p>Each of <tt>val1</tt> and <tt>val2</tt> arguments must be either | |
| a <a href="#t_floating">floating point</a> type or | |
| a <a href="#t_vector">vector</a> of floating point type. They must have | |
| identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>fcmp</tt>' instruction compares <tt>op1</tt> and <tt>op2</tt> | |
| according to the condition code given as <tt>cond</tt>. If the operands are | |
| vectors, then the vectors are compared element by element. Each comparison | |
| performed always yields an <a href="#t_primitive">i1</a> result, as | |
| follows:</p> | |
| <ol> | |
| <li><tt>false</tt>: always yields <tt>false</tt>, regardless of operands.</li> | |
| <li><tt>oeq</tt>: yields <tt>true</tt> if both operands are not a QNAN and | |
| <tt>op1</tt> is equal to <tt>op2</tt>.</li> | |
| <li><tt>ogt</tt>: yields <tt>true</tt> if both operands are not a QNAN and | |
| <tt>op1</tt> is greather than <tt>op2</tt>.</li> | |
| <li><tt>oge</tt>: yields <tt>true</tt> if both operands are not a QNAN and | |
| <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li> | |
| <li><tt>olt</tt>: yields <tt>true</tt> if both operands are not a QNAN and | |
| <tt>op1</tt> is less than <tt>op2</tt>.</li> | |
| <li><tt>ole</tt>: yields <tt>true</tt> if both operands are not a QNAN and | |
| <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> | |
| <li><tt>one</tt>: yields <tt>true</tt> if both operands are not a QNAN and | |
| <tt>op1</tt> is not equal to <tt>op2</tt>.</li> | |
| <li><tt>ord</tt>: yields <tt>true</tt> if both operands are not a QNAN.</li> | |
| <li><tt>ueq</tt>: yields <tt>true</tt> if either operand is a QNAN or | |
| <tt>op1</tt> is equal to <tt>op2</tt>.</li> | |
| <li><tt>ugt</tt>: yields <tt>true</tt> if either operand is a QNAN or | |
| <tt>op1</tt> is greater than <tt>op2</tt>.</li> | |
| <li><tt>uge</tt>: yields <tt>true</tt> if either operand is a QNAN or | |
| <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li> | |
| <li><tt>ult</tt>: yields <tt>true</tt> if either operand is a QNAN or | |
| <tt>op1</tt> is less than <tt>op2</tt>.</li> | |
| <li><tt>ule</tt>: yields <tt>true</tt> if either operand is a QNAN or | |
| <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> | |
| <li><tt>une</tt>: yields <tt>true</tt> if either operand is a QNAN or | |
| <tt>op1</tt> is not equal to <tt>op2</tt>.</li> | |
| <li><tt>uno</tt>: yields <tt>true</tt> if either operand is a QNAN.</li> | |
| <li><tt>true</tt>: always yields <tt>true</tt>, regardless of operands.</li> | |
| </ol> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = fcmp oeq float 4.0, 5.0 <i>; yields: result=false</i> | |
| <result> = fcmp one float 4.0, 5.0 <i>; yields: result=true</i> | |
| <result> = fcmp olt float 4.0, 5.0 <i>; yields: result=true</i> | |
| <result> = fcmp ueq double 1.0, 2.0 <i>; yields: result=false</i> | |
| </pre> | |
| <p>Note that the code generator does not yet support vector types with | |
| the <tt>fcmp</tt> instruction.</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>], ... | |
| </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 is 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> | |
| <p>For the purposes of the SSA form, the use of each incoming value is deemed to | |
| occur on the edge from the corresponding predecessor block to the current | |
| block (but after any definition of an '<tt>invoke</tt>' instruction's return | |
| value on the same edge).</p> | |
| <h5>Semantics:</h5> | |
| <p>At runtime, the '<tt>phi</tt>' instruction logically takes on the value | |
| specified by the pair corresponding to the predecessor basic block that | |
| executed just prior to the current block.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| Loop: ; Infinite loop that counts from 0 on up... | |
| %indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ] | |
| %nextindvar = add i32 %indvar, 1 | |
| br label %Loop | |
| </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 <i>selty</i> <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i> | |
| <i>selty</i> is either i1 or {<N x i1>} | |
| </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 an 'i1' value or a vector of 'i1' | |
| values indicating the condition, and two values of the | |
| same <a href="#t_firstclass">first class</a> type. If the val1/val2 are | |
| vectors and the condition is a scalar, then entire vectors are selected, not | |
| individual elements.</p> | |
| <h5>Semantics:</h5> | |
| <p>If the condition is an i1 and it evaluates to 1, the instruction returns the | |
| first value argument; otherwise, it returns the second value argument.</p> | |
| <p>If the condition is a vector of i1, then the value arguments must be vectors | |
| of the same size, and the selection is done element by element.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = select i1 true, i8 17, i8 42 <i>; yields i8:17</i> | |
| </pre> | |
| <p>Note that the code generator does not yet support conditions | |
| with vector type.</p> | |
| </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>] [<a href="#paramattrs">ret attrs</a>] <ty> [<fnty>*] <fnptrval>(<function args>) [<a href="#fnattrs">fn attrs</a>] | |
| </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>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>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>The optional <a href="#paramattrs">Parameter Attributes</a> list for | |
| return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and | |
| '<tt>inreg</tt>' attributes are valid here.</li> | |
| <li>'<tt>ty</tt>': the type of the call instruction itself which is also the | |
| type of the return value. Functions that return no value are marked | |
| <tt><a href="#t_void">void</a></tt>.</li> | |
| <li>'<tt>fnty</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.</li> | |
| <li>'<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.</li> | |
| <li>'<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.</li> | |
| <li>The optional <a href="#fnattrs">function attributes</a> list. Only | |
| '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and | |
| '<tt>readnone</tt>' attributes are valid here.</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.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %retval = call i32 @test(i32 %argc) | |
| call i32 (i8 *, ...)* @printf(i8 * %msg, i32 12, i8 42) <i>; yields i32</i> | |
| %X = tail call i32 @foo() <i>; yields i32</i> | |
| %Y = tail call <a href="#callingconv">fastcc</a> i32 @foo() <i>; yields i32</i> | |
| call void %foo(i8 97 signext) | |
| %struct.A = type { i32, i8 } | |
| %r = call %struct.A @foo() <i>; yields { 32, i8 }</i> | |
| %gr = extractvalue %struct.A %r, 0 <i>; yields i32</i> | |
| %gr1 = extractvalue %struct.A %r, 1 <i>; yields i8</i> | |
| %Z = call void @foo() noreturn <i>; indicates that %foo never returns normally</i> | |
| %ZZ = call zeroext i32 @bar() <i>; Return value is %zero extended</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_va_arg">'<tt>va_arg</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 point to the next argument. 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> | |
| <p>Note that the code generator does not yet fully support va_arg on many | |
| targets. Also, it does not currently support va_arg with aggregate types on | |
| any target.</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 intrinsics represent an extension mechanism for | |
| the LLVM language that does not require changing all of the transformations | |
| in LLVM when adding to the language (or the bitcode 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, function names may not | |
| begin with this prefix. 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 if any are added that | |
| they be documented here.</p> | |
| <p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents a | |
| family of functions that perform the same operation but on different data | |
| types. Because LLVM can represent over 8 million different integer types, | |
| overloading is used commonly to allow an intrinsic function to operate on any | |
| integer type. One or more of the argument types or the result type can be | |
| overloaded to accept any integer type. Argument types may also be defined as | |
| exactly matching a previous argument's type or the result type. This allows | |
| an intrinsic function which accepts multiple arguments, but needs all of them | |
| to be of the same type, to only be overloaded with respect to a single | |
| argument or the result.</p> | |
| <p>Overloaded intrinsics will have the names of its overloaded argument types | |
| encoded into its function name, each preceded by a period. Only those types | |
| which are overloaded result in a name suffix. Arguments whose type is matched | |
| against another type do not. For example, the <tt>llvm.ctpop</tt> function | |
| can take an integer of any width and returns an integer of exactly the same | |
| integer width. This leads to a family of functions such as | |
| <tt>i8 @llvm.ctpop.i8(i8 %val)</tt> and <tt>i29 @llvm.ctpop.i29(i29 | |
| %val)</tt>. Only one type, the return type, is overloaded, and only one type | |
| suffix is required. Because the argument's type is matched against the return | |
| type, it does not require its own name suffix.</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_va_arg"><tt>va_arg</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 these functions regardless of the type used.</p> | |
| <p>This example shows how the <a href="#i_va_arg"><tt>va_arg</tt></a> | |
| instruction and the variable argument handling intrinsic functions are | |
| used.</p> | |
| <div class="doc_code"> | |
| <pre> | |
| define i32 @test(i32 %X, ...) { | |
| ; Initialize variable argument processing | |
| %ap = alloca i8* | |
| %ap2 = bitcast i8** %ap to i8* | |
| call void @llvm.va_start(i8* %ap2) | |
| ; Read a single integer argument | |
| %tmp = va_arg i8** %ap, i32 | |
| ; Demonstrate usage of llvm.va_copy and llvm.va_end | |
| %aq = alloca i8* | |
| %aq2 = bitcast i8** %aq to i8* | |
| call void @llvm.va_copy(i8* %aq2, i8* %ap2) | |
| call void @llvm.va_end(i8* %aq2) | |
| ; Stop processing of arguments. | |
| call void @llvm.va_end(i8* %ap2) | |
| ret i32 %tmp | |
| } | |
| declare void @llvm.va_start(i8*) | |
| declare void @llvm.va_copy(i8*, i8*) | |
| declare void @llvm.va_end(i8*) | |
| </pre> | |
| </div> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.va_start(i8* <arglist>) | |
| </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 to which the argument points, 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 as the compiler can figure | |
| that out.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.va_end(i8* <arglist>) | |
| </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="#int_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 pointer to 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> element to which the argument points. Calls | |
| to <a href="#int_va_start"><tt>llvm.va_start</tt></a> | |
| and <a href="#int_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="int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.va_copy(i8* <destarglist>, i8* <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 pointer to 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 <tt>va_list</tt> | |
| element. This intrinsic is necessary because | |
| the <tt><a href="#int_va_start"> llvm.va_start</a></tt> intrinsic may be | |
| arbitrarily complex and require, for example, memory allocation.</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> (GC) requires the implementation and generation of these | |
| intrinsics. These intrinsics allow identification of <a href="#int_gcroot">GC | |
| roots on the stack</a>, as well as garbage collector implementations that | |
| require <a href="#int_gcread">read</a> and <a href="#int_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> | |
| <p>The garbage collection intrinsics only operate on objects in the generic | |
| address space (address space zero).</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.gcroot(i8** %ptrloc, i8* %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 intrinsic 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. The '<tt>llvm.gcroot</tt>' | |
| intrinsic may only be used in a function which <a href="#gc">specifies a GC | |
| algorithm</a>.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare i8* @llvm.gcread(i8* %ObjPtr, i8** %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 second argument is the address to read from, which should be an address | |
| allocated from the garbage collector. The first object is a pointer to the | |
| start of the referenced object, if needed by the language runtime (otherwise | |
| null).</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. The '<tt>llvm.gcread</tt>' intrinsic | |
| may only be used in a function which <a href="#gc">specifies a GC | |
| algorithm</a>.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %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, the second is the start of the | |
| object to store it to, and the third is the address of the field of Obj to | |
| store to. If the runtime does not require a pointer to the object, Obj may | |
| be null.</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. The '<tt>llvm.gcwrite</tt>' intrinsic | |
| may only be used in a function which <a href="#gc">specifies a GC | |
| algorithm</a>.</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="int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare i8 *@llvm.returnaddress(i32 <level>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.returnaddress</tt>' intrinsic attempts to compute 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="int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare i8 *@llvm.frameaddress(i32 <level>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.frameaddress</tt>' intrinsic attempts to return 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="int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare i8 *@llvm.stacksave() | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state | |
| of the function stack, for use | |
| with <a href="#int_stackrestore"> <tt>llvm.stackrestore</tt></a>. This is | |
| useful for implementing language features like scoped automatic variable | |
| sized arrays in C99.</p> | |
| <h5>Semantics:</h5> | |
| <p>This intrinsic returns a opaque pointer value that can be passed | |
| to <a href="#int_stackrestore"><tt>llvm.stackrestore</tt></a>. When | |
| an <tt>llvm.stackrestore</tt> intrinsic is executed with a value saved | |
| from <tt>llvm.stacksave</tt>, it effectively restores the state of the stack | |
| to the state it was in when the <tt>llvm.stacksave</tt> intrinsic executed. | |
| In practice, this pops any <a href="#i_alloca">alloca</a> blocks from the | |
| stack that were allocated after the <tt>llvm.stacksave</tt> was executed.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.stackrestore(i8 * %ptr) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of | |
| the function stack to the state it was in when the | |
| corresponding <a href="#int_stacksave"><tt>llvm.stacksave</tt></a> intrinsic | |
| executed. This is useful for implementing language features like scoped | |
| automatic variable sized arrays in C99.</p> | |
| <h5>Semantics:</h5> | |
| <p>See the description | |
| for <a href="#int_stacksave"><tt>llvm.stacksave</tt></a>.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <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="int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.pcmarker(i32 <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 guarantees | |
| that it will remain with any specific instruction after optimizations. It is | |
| possible that the presence of a marker will inhibit optimizations. The | |
| intended use is to be inserted after optimizations 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_subsubsection"> | |
| <a name="int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare i64 @llvm.readcyclecounter( ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle | |
| counter register (or similar low latency, high accuracy clocks) on those | |
| targets that support it. On X86, it should map to RDTSC. On Alpha, it | |
| should map to RPCC. As the backing counters overflow quickly (on the order | |
| of 9 seconds on alpha), this should only be used for small timings.</p> | |
| <h5>Semantics:</h5> | |
| <p>When directly supported, reading the cycle counter should not modify any | |
| memory. Implementations are allowed to either return a application specific | |
| value or a system wide value. On backends without support, this is lowered | |
| to a constant 0.</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="int_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.memcpy</tt> on any | |
| integer bit width. Not all targets support all bit widths however.</p> | |
| <pre> | |
| declare void @llvm.memcpy.i8(i8 * <dest>, i8 * <src>, | |
| i8 <len>, i32 <align>) | |
| declare void @llvm.memcpy.i16(i8 * <dest>, i8 * <src>, | |
| i16 <len>, i32 <align>) | |
| declare void @llvm.memcpy.i32(i8 * <dest>, i8 * <src>, | |
| i32 <len>, i32 <align>) | |
| declare void @llvm.memcpy.i64(i8 * <dest>, i8 * <src>, | |
| i64 <len>, i32 <align>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy 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> | |
| intrinsics do 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 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 both the source and destination pointers are | |
| aligned to that boundary.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy 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="int_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use llvm.memmove on any integer bit | |
| width. Not all targets support all bit widths however.</p> | |
| <pre> | |
| declare void @llvm.memmove.i8(i8 * <dest>, i8 * <src>, | |
| i8 <len>, i32 <align>) | |
| declare void @llvm.memmove.i16(i8 * <dest>, i8 * <src>, | |
| i16 <len>, i32 <align>) | |
| declare void @llvm.memmove.i32(i8 * <dest>, i8 * <src>, | |
| i32 <len>, i32 <align>) | |
| declare void @llvm.memmove.i64(i8 * <dest>, i8 * <src>, | |
| i64 <len>, i32 <align>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.memmove.*</tt>' intrinsics move 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> | |
| intrinsics do 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 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 source and destination pointers are | |
| aligned to that boundary.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.memmove.*</tt>' intrinsics copy 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="int_memset">'<tt>llvm.memset.*</tt>' Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use llvm.memset on any integer bit | |
| width. Not all targets support all bit widths however.</p> | |
| <pre> | |
| declare void @llvm.memset.i8(i8 * <dest>, i8 <val>, | |
| i8 <len>, i32 <align>) | |
| declare void @llvm.memset.i16(i8 * <dest>, i8 <val>, | |
| i16 <len>, i32 <align>) | |
| declare void @llvm.memset.i32(i8 * <dest>, i8 <val>, | |
| i32 <len>, i32 <align>) | |
| declare void @llvm.memset.i64(i8 * <dest>, i8 <val>, | |
| i64 <len>, i32 <align>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.memset.*</tt>' intrinsics fill 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 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 destination pointer is aligned to that | |
| boundary.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.memset.*</tt>' intrinsics fill "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="int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.sqrt</tt> on any | |
| floating point or vector of floating point type. Not all targets support all | |
| types however.</p> | |
| <pre> | |
| declare float @llvm.sqrt.f32(float %Val) | |
| declare double @llvm.sqrt.f64(double %Val) | |
| declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val) | |
| declare fp128 @llvm.sqrt.f128(fp128 %Val) | |
| declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.sqrt</tt>' intrinsics return the sqrt of the specified operand, | |
| returning the same value as the libm '<tt>sqrt</tt>' functions would. | |
| Unlike <tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined | |
| behavior for negative numbers other than -0.0 (which allows for better | |
| optimization, because there is no need to worry about errno being | |
| set). <tt>llvm.sqrt(-0.0)</tt> is defined to return -0.0 like IEEE sqrt.</p> | |
| <h5>Arguments:</h5> | |
| <p>The argument and return value are floating point numbers of the same | |
| type.</p> | |
| <h5>Semantics:</h5> | |
| <p>This function returns the sqrt of the specified operand if it is a | |
| nonnegative floating point number.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.powi</tt> on any | |
| floating point or vector of floating point type. Not all targets support all | |
| types however.</p> | |
| <pre> | |
| declare float @llvm.powi.f32(float %Val, i32 %power) | |
| declare double @llvm.powi.f64(double %Val, i32 %power) | |
| declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power) | |
| declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power) | |
| declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.powi.*</tt>' intrinsics return the first operand raised to the | |
| specified (positive or negative) power. The order of evaluation of | |
| multiplications is not defined. When a vector of floating point type is | |
| used, the second argument remains a scalar integer value.</p> | |
| <h5>Arguments:</h5> | |
| <p>The second argument is an integer power, and the first is a value to raise to | |
| that power.</p> | |
| <h5>Semantics:</h5> | |
| <p>This function returns the first value raised to the second power with an | |
| unspecified sequence of rounding operations.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.sin</tt> on any | |
| floating point or vector of floating point type. Not all targets support all | |
| types however.</p> | |
| <pre> | |
| declare float @llvm.sin.f32(float %Val) | |
| declare double @llvm.sin.f64(double %Val) | |
| declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val) | |
| declare fp128 @llvm.sin.f128(fp128 %Val) | |
| declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.sin.*</tt>' intrinsics return the sine of the operand.</p> | |
| <h5>Arguments:</h5> | |
| <p>The argument and return value are floating point numbers of the same | |
| type.</p> | |
| <h5>Semantics:</h5> | |
| <p>This function returns the sine of the specified operand, returning the same | |
| values as the libm <tt>sin</tt> functions would, and handles error conditions | |
| in the same way.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.cos</tt> on any | |
| floating point or vector of floating point type. Not all targets support all | |
| types however.</p> | |
| <pre> | |
| declare float @llvm.cos.f32(float %Val) | |
| declare double @llvm.cos.f64(double %Val) | |
| declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val) | |
| declare fp128 @llvm.cos.f128(fp128 %Val) | |
| declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.cos.*</tt>' intrinsics return the cosine of the operand.</p> | |
| <h5>Arguments:</h5> | |
| <p>The argument and return value are floating point numbers of the same | |
| type.</p> | |
| <h5>Semantics:</h5> | |
| <p>This function returns the cosine of the specified operand, returning the same | |
| values as the libm <tt>cos</tt> functions would, and handles error conditions | |
| in the same way.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.pow</tt> on any | |
| floating point or vector of floating point type. Not all targets support all | |
| types however.</p> | |
| <pre> | |
| declare float @llvm.pow.f32(float %Val, float %Power) | |
| declare double @llvm.pow.f64(double %Val, double %Power) | |
| declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power) | |
| declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power) | |
| declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.pow.*</tt>' intrinsics return the first operand raised to the | |
| specified (positive or negative) power.</p> | |
| <h5>Arguments:</h5> | |
| <p>The second argument is a floating point power, and the first is a value to | |
| raise to that power.</p> | |
| <h5>Semantics:</h5> | |
| <p>This function returns the first value raised to the second power, returning | |
| the same values as the libm <tt>pow</tt> functions would, and handles error | |
| conditions in the same way.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_manip">Bit Manipulation Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM provides intrinsics for a few important bit manipulation operations. | |
| These allow efficient code generation for some algorithms.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic function. You can use bswap on any integer | |
| type that is an even number of bytes (i.e. BitWidth % 16 == 0).</p> | |
| <pre> | |
| declare i16 @llvm.bswap.i16(i16 <id>) | |
| declare i32 @llvm.bswap.i32(i32 <id>) | |
| declare i64 @llvm.bswap.i64(i64 <id>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.bswap</tt>' family of intrinsics is used to byte swap integer | |
| values with an even number of bytes (positive multiple of 16 bits). These | |
| are useful for performing operations on data that is not in the target's | |
| native byte order.</p> | |
| <h5>Semantics:</h5> | |
| <p>The <tt>llvm.bswap.i16</tt> intrinsic returns an i16 value that has the high | |
| and low byte of the input i16 swapped. Similarly, | |
| the <tt>llvm.bswap.i32</tt> intrinsic returns an i32 value that has the four | |
| bytes of the input i32 swapped, so that if the input bytes are numbered 0, 1, | |
| 2, 3 then the returned i32 will have its bytes in 3, 2, 1, 0 order. | |
| The <tt>llvm.bswap.i48</tt>, <tt>llvm.bswap.i64</tt> and other intrinsics | |
| extend this concept to additional even-byte lengths (6 bytes, 8 bytes and | |
| more, respectively).</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit | |
| width. Not all targets support all bit widths however.</p> | |
| <pre> | |
| declare i8 @llvm.ctpop.i8(i8 <src>) | |
| declare i16 @llvm.ctpop.i16(i16 <src>) | |
| declare i32 @llvm.ctpop.i32(i32 <src>) | |
| declare i64 @llvm.ctpop.i64(i64 <src>) | |
| declare i256 @llvm.ctpop.i256(i256 <src>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set | |
| in a value.</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> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.ctlz</tt> on any | |
| integer bit width. Not all targets support all bit widths however.</p> | |
| <pre> | |
| declare i8 @llvm.ctlz.i8 (i8 <src>) | |
| declare i16 @llvm.ctlz.i16(i16 <src>) | |
| declare i32 @llvm.ctlz.i32(i32 <src>) | |
| declare i64 @llvm.ctlz.i64(i64 <src>) | |
| declare i256 @llvm.ctlz.i256(i256 <src>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.ctlz</tt>' family of intrinsic functions 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.ctlz(i32 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> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.cttz</tt> on any | |
| integer bit width. Not all targets support all bit widths however.</p> | |
| <pre> | |
| declare i8 @llvm.cttz.i8 (i8 <src>) | |
| declare i16 @llvm.cttz.i16(i16 <src>) | |
| declare i32 @llvm.cttz.i32(i32 <src>) | |
| declare i64 @llvm.cttz.i64(i64 <src>) | |
| declare i256 @llvm.cttz.i256(i256 <src>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.cttz</tt>' family of intrinsic functions 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>.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_overflow">Arithmetic with Overflow Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM provides intrinsics for some arithmetic with overflow operations.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt>' Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.sadd.with.overflow</tt> | |
| on any integer bit width.</p> | |
| <pre> | |
| declare {i16, i1} @llvm.sadd.with.overflow.i16(i16 %a, i16 %b) | |
| declare {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b) | |
| declare {i64, i1} @llvm.sadd.with.overflow.i64(i64 %a, i64 %b) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform | |
| a signed addition of the two arguments, and indicate whether an overflow | |
| occurred during the signed summation.</p> | |
| <h5>Arguments:</h5> | |
| <p>The arguments (%a and %b) and the first element of the result structure may | |
| be of integer types of any bit width, but they must have the same bit | |
| width. The second element of the result structure must be of | |
| type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will | |
| undergo signed addition.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform | |
| a signed addition of the two variables. They return a structure — the | |
| first element of which is the signed summation, and the second element of | |
| which is a bit specifying if the signed summation resulted in an | |
| overflow.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b) | |
| %sum = extractvalue {i32, i1} %res, 0 | |
| %obit = extractvalue {i32, i1} %res, 1 | |
| br i1 %obit, label %overflow, label %normal | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt>' Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.uadd.with.overflow</tt> | |
| on any integer bit width.</p> | |
| <pre> | |
| declare {i16, i1} @llvm.uadd.with.overflow.i16(i16 %a, i16 %b) | |
| declare {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b) | |
| declare {i64, i1} @llvm.uadd.with.overflow.i64(i64 %a, i64 %b) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform | |
| an unsigned addition of the two arguments, and indicate whether a carry | |
| occurred during the unsigned summation.</p> | |
| <h5>Arguments:</h5> | |
| <p>The arguments (%a and %b) and the first element of the result structure may | |
| be of integer types of any bit width, but they must have the same bit | |
| width. The second element of the result structure must be of | |
| type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will | |
| undergo unsigned addition.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform | |
| an unsigned addition of the two arguments. They return a structure — | |
| the first element of which is the sum, and the second element of which is a | |
| bit specifying if the unsigned summation resulted in a carry.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %res = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b) | |
| %sum = extractvalue {i32, i1} %res, 0 | |
| %obit = extractvalue {i32, i1} %res, 1 | |
| br i1 %obit, label %carry, label %normal | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt>' Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.ssub.with.overflow</tt> | |
| on any integer bit width.</p> | |
| <pre> | |
| declare {i16, i1} @llvm.ssub.with.overflow.i16(i16 %a, i16 %b) | |
| declare {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b) | |
| declare {i64, i1} @llvm.ssub.with.overflow.i64(i64 %a, i64 %b) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform | |
| a signed subtraction of the two arguments, and indicate whether an overflow | |
| occurred during the signed subtraction.</p> | |
| <h5>Arguments:</h5> | |
| <p>The arguments (%a and %b) and the first element of the result structure may | |
| be of integer types of any bit width, but they must have the same bit | |
| width. The second element of the result structure must be of | |
| type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will | |
| undergo signed subtraction.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform | |
| a signed subtraction of the two arguments. They return a structure — | |
| the first element of which is the subtraction, and the second element of | |
| which is a bit specifying if the signed subtraction resulted in an | |
| overflow.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %res = call {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b) | |
| %sum = extractvalue {i32, i1} %res, 0 | |
| %obit = extractvalue {i32, i1} %res, 1 | |
| br i1 %obit, label %overflow, label %normal | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt>' Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.usub.with.overflow</tt> | |
| on any integer bit width.</p> | |
| <pre> | |
| declare {i16, i1} @llvm.usub.with.overflow.i16(i16 %a, i16 %b) | |
| declare {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b) | |
| declare {i64, i1} @llvm.usub.with.overflow.i64(i64 %a, i64 %b) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform | |
| an unsigned subtraction of the two arguments, and indicate whether an | |
| overflow occurred during the unsigned subtraction.</p> | |
| <h5>Arguments:</h5> | |
| <p>The arguments (%a and %b) and the first element of the result structure may | |
| be of integer types of any bit width, but they must have the same bit | |
| width. The second element of the result structure must be of | |
| type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will | |
| undergo unsigned subtraction.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform | |
| an unsigned subtraction of the two arguments. They return a structure — | |
| the first element of which is the subtraction, and the second element of | |
| which is a bit specifying if the unsigned subtraction resulted in an | |
| overflow.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %res = call {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b) | |
| %sum = extractvalue {i32, i1} %res, 0 | |
| %obit = extractvalue {i32, i1} %res, 1 | |
| br i1 %obit, label %overflow, label %normal | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt>' Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.smul.with.overflow</tt> | |
| on any integer bit width.</p> | |
| <pre> | |
| declare {i16, i1} @llvm.smul.with.overflow.i16(i16 %a, i16 %b) | |
| declare {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b) | |
| declare {i64, i1} @llvm.smul.with.overflow.i64(i64 %a, i64 %b) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform | |
| a signed multiplication of the two arguments, and indicate whether an | |
| overflow occurred during the signed multiplication.</p> | |
| <h5>Arguments:</h5> | |
| <p>The arguments (%a and %b) and the first element of the result structure may | |
| be of integer types of any bit width, but they must have the same bit | |
| width. The second element of the result structure must be of | |
| type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will | |
| undergo signed multiplication.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform | |
| a signed multiplication of the two arguments. They return a structure — | |
| the first element of which is the multiplication, and the second element of | |
| which is a bit specifying if the signed multiplication resulted in an | |
| overflow.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %res = call {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b) | |
| %sum = extractvalue {i32, i1} %res, 0 | |
| %obit = extractvalue {i32, i1} %res, 1 | |
| br i1 %obit, label %overflow, label %normal | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt>' Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.umul.with.overflow</tt> | |
| on any integer bit width.</p> | |
| <pre> | |
| declare {i16, i1} @llvm.umul.with.overflow.i16(i16 %a, i16 %b) | |
| declare {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b) | |
| declare {i64, i1} @llvm.umul.with.overflow.i64(i64 %a, i64 %b) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform | |
| a unsigned multiplication of the two arguments, and indicate whether an | |
| overflow occurred during the unsigned multiplication.</p> | |
| <h5>Arguments:</h5> | |
| <p>The arguments (%a and %b) and the first element of the result structure may | |
| be of integer types of any bit width, but they must have the same bit | |
| width. The second element of the result structure must be of | |
| type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will | |
| undergo unsigned multiplication.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform | |
| an unsigned multiplication of the two arguments. They return a structure | |
| — the first element of which is the multiplication, and the second | |
| element of which is a bit specifying if the unsigned multiplication resulted | |
| in an overflow.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %res = call {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b) | |
| %sum = extractvalue {i32, i1} %res, 0 | |
| %obit = extractvalue {i32, i1} %res, 1 | |
| br i1 %obit, label %overflow, label %normal | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_debugger">Debugger Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt> | |
| prefix), are described in | |
| the <a href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source | |
| Level Debugging</a> document.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_eh">Exception Handling Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>The LLVM exception handling intrinsics (which all start with | |
| <tt>llvm.eh.</tt> prefix), are described in | |
| the <a href="ExceptionHandling.html#format_common_intrinsics">LLVM Exception | |
| Handling</a> document.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_trampoline">Trampoline Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>This intrinsic makes it possible to excise one parameter, marked with | |
| the <tt>nest</tt> attribute, from a function. The result is a callable | |
| function pointer lacking the nest parameter - the caller does not need to | |
| provide a value for it. Instead, the value to use is stored in advance in a | |
| "trampoline", a block of memory usually allocated on the stack, which also | |
| contains code to splice the nest value into the argument list. This is used | |
| to implement the GCC nested function address extension.</p> | |
| <p>For example, if the function is | |
| <tt>i32 f(i8* nest %c, i32 %x, i32 %y)</tt> then the resulting function | |
| pointer has signature <tt>i32 (i32, i32)*</tt>. It can be created as | |
| follows:</p> | |
| <div class="doc_code"> | |
| <pre> | |
| %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86 | |
| %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0 | |
| %p = call i8* @llvm.init.trampoline( i8* %tramp1, i8* bitcast (i32 (i8* nest , i32, i32)* @f to i8*), i8* %nval ) | |
| %fp = bitcast i8* %p to i32 (i32, i32)* | |
| </pre> | |
| </div> | |
| <p>The call <tt>%val = call i32 %fp( i32 %x, i32 %y )</tt> is then equivalent | |
| to <tt>%val = call i32 %f( i8* %nval, i32 %x, i32 %y )</tt>.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare i8* @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>This fills the memory pointed to by <tt>tramp</tt> with code and returns a | |
| function pointer suitable for executing it.</p> | |
| <h5>Arguments:</h5> | |
| <p>The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all | |
| pointers. The <tt>tramp</tt> argument must point to a sufficiently large and | |
| sufficiently aligned block of memory; this memory is written to by the | |
| intrinsic. Note that the size and the alignment are target-specific - LLVM | |
| currently provides no portable way of determining them, so a front-end that | |
| generates this intrinsic needs to have some target-specific knowledge. | |
| The <tt>func</tt> argument must hold a function bitcast to | |
| an <tt>i8*</tt>.</p> | |
| <h5>Semantics:</h5> | |
| <p>The block of memory pointed to by <tt>tramp</tt> is filled with target | |
| dependent code, turning it into a function. A pointer to this function is | |
| returned, but needs to be bitcast to an <a href="#int_trampoline">appropriate | |
| function pointer type</a> before being called. The new function's signature | |
| is the same as that of <tt>func</tt> with any arguments marked with | |
| the <tt>nest</tt> attribute removed. At most one such <tt>nest</tt> argument | |
| is allowed, and it must be of pointer type. Calling the new function is | |
| equivalent to calling <tt>func</tt> with the same argument list, but | |
| with <tt>nval</tt> used for the missing <tt>nest</tt> argument. If, after | |
| calling <tt>llvm.init.trampoline</tt>, the memory pointed to | |
| by <tt>tramp</tt> is modified, then the effect of any later call to the | |
| returned function pointer is undefined.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_atomics">Atomic Operations and Synchronization Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>These intrinsic functions expand the "universal IR" of LLVM to represent | |
| hardware constructs for atomic operations and memory synchronization. This | |
| provides an interface to the hardware, not an interface to the programmer. It | |
| is aimed at a low enough level to allow any programming models or APIs | |
| (Application Programming Interfaces) which need atomic behaviors to map | |
| cleanly onto it. It is also modeled primarily on hardware behavior. Just as | |
| hardware provides a "universal IR" for source languages, it also provides a | |
| starting point for developing a "universal" atomic operation and | |
| synchronization IR.</p> | |
| <p>These do <em>not</em> form an API such as high-level threading libraries, | |
| software transaction memory systems, atomic primitives, and intrinsic | |
| functions as found in BSD, GNU libc, atomic_ops, APR, and other system and | |
| application libraries. The hardware interface provided by LLVM should allow | |
| a clean implementation of all of these APIs and parallel programming models. | |
| No one model or paradigm should be selected above others unless the hardware | |
| itself ubiquitously does so.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_memory_barrier">'<tt>llvm.memory.barrier</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.memory.barrier( i1 <ll>, i1 <ls>, i1 <sl>, i1 <ss>, i1 <device> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The <tt>llvm.memory.barrier</tt> intrinsic guarantees ordering between | |
| specific pairs of memory access types.</p> | |
| <h5>Arguments:</h5> | |
| <p>The <tt>llvm.memory.barrier</tt> intrinsic requires five boolean arguments. | |
| The first four arguments enables a specific barrier as listed below. The | |
| fith argument specifies that the barrier applies to io or device or uncached | |
| memory.</p> | |
| <ul> | |
| <li><tt>ll</tt>: load-load barrier</li> | |
| <li><tt>ls</tt>: load-store barrier</li> | |
| <li><tt>sl</tt>: store-load barrier</li> | |
| <li><tt>ss</tt>: store-store barrier</li> | |
| <li><tt>device</tt>: barrier applies to device and uncached memory also.</li> | |
| </ul> | |
| <h5>Semantics:</h5> | |
| <p>This intrinsic causes the system to enforce some ordering constraints upon | |
| the loads and stores of the program. This barrier does not | |
| indicate <em>when</em> any events will occur, it only enforces | |
| an <em>order</em> in which they occur. For any of the specified pairs of load | |
| and store operations (f.ex. load-load, or store-load), all of the first | |
| operations preceding the barrier will complete before any of the second | |
| operations succeeding the barrier begin. Specifically the semantics for each | |
| pairing is as follows:</p> | |
| <ul> | |
| <li><tt>ll</tt>: All loads before the barrier must complete before any load | |
| after the barrier begins.</li> | |
| <li><tt>ls</tt>: All loads before the barrier must complete before any | |
| store after the barrier begins.</li> | |
| <li><tt>ss</tt>: All stores before the barrier must complete before any | |
| store after the barrier begins.</li> | |
| <li><tt>sl</tt>: All stores before the barrier must complete before any | |
| load after the barrier begins.</li> | |
| </ul> | |
| <p>These semantics are applied with a logical "and" behavior when more than one | |
| is enabled in a single memory barrier intrinsic.</p> | |
| <p>Backends may implement stronger barriers than those requested when they do | |
| not support as fine grained a barrier as requested. Some architectures do | |
| not need all types of barriers and on such architectures, these become | |
| noops.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %ptr = malloc i32 | |
| store i32 4, %ptr | |
| %result1 = load i32* %ptr <i>; yields {i32}:result1 = 4</i> | |
| call void @llvm.memory.barrier( i1 false, i1 true, i1 false, i1 false ) | |
| <i>; guarantee the above finishes</i> | |
| store i32 8, %ptr <i>; before this begins</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_atomic_cmp_swap">'<tt>llvm.atomic.cmp.swap.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.cmp.swap</tt> on | |
| any integer bit width and for different address spaces. Not all targets | |
| support all bit widths however.</p> | |
| <pre> | |
| declare i8 @llvm.atomic.cmp.swap.i8.p0i8( i8* <ptr>, i8 <cmp>, i8 <val> ) | |
| declare i16 @llvm.atomic.cmp.swap.i16.p0i16( i16* <ptr>, i16 <cmp>, i16 <val> ) | |
| declare i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* <ptr>, i32 <cmp>, i32 <val> ) | |
| declare i64 @llvm.atomic.cmp.swap.i64.p0i64( i64* <ptr>, i64 <cmp>, i64 <val> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>This loads a value in memory and compares it to a given value. If they are | |
| equal, it stores a new value into the memory.</p> | |
| <h5>Arguments:</h5> | |
| <p>The <tt>llvm.atomic.cmp.swap</tt> intrinsic takes three arguments. The result | |
| as well as both <tt>cmp</tt> and <tt>val</tt> must be integer values with the | |
| same bit width. The <tt>ptr</tt> argument must be a pointer to a value of | |
| this integer type. While any bit width integer may be used, targets may only | |
| lower representations they support in hardware.</p> | |
| <h5>Semantics:</h5> | |
| <p>This entire intrinsic must be executed atomically. It first loads the value | |
| in memory pointed to by <tt>ptr</tt> and compares it with the | |
| value <tt>cmp</tt>. If they are equal, <tt>val</tt> is stored into the | |
| memory. The loaded value is yielded in all cases. This provides the | |
| equivalent of an atomic compare-and-swap operation within the SSA | |
| framework.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %ptr = malloc i32 | |
| store i32 4, %ptr | |
| %val1 = add i32 4, 4 | |
| %result1 = call i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* %ptr, i32 4, %val1 ) | |
| <i>; yields {i32}:result1 = 4</i> | |
| %stored1 = icmp eq i32 %result1, 4 <i>; yields {i1}:stored1 = true</i> | |
| %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 8</i> | |
| %val2 = add i32 1, 1 | |
| %result2 = call i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* %ptr, i32 5, %val2 ) | |
| <i>; yields {i32}:result2 = 8</i> | |
| %stored2 = icmp eq i32 %result2, 5 <i>; yields {i1}:stored2 = false</i> | |
| %memval2 = load i32* %ptr <i>; yields {i32}:memval2 = 8</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_atomic_swap">'<tt>llvm.atomic.swap.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.swap</tt> on any | |
| integer bit width. Not all targets support all bit widths however.</p> | |
| <pre> | |
| declare i8 @llvm.atomic.swap.i8.p0i8( i8* <ptr>, i8 <val> ) | |
| declare i16 @llvm.atomic.swap.i16.p0i16( i16* <ptr>, i16 <val> ) | |
| declare i32 @llvm.atomic.swap.i32.p0i32( i32* <ptr>, i32 <val> ) | |
| declare i64 @llvm.atomic.swap.i64.p0i64( i64* <ptr>, i64 <val> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>This intrinsic loads the value stored in memory at <tt>ptr</tt> and yields | |
| the value from memory. It then stores the value in <tt>val</tt> in the memory | |
| at <tt>ptr</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The <tt>llvm.atomic.swap</tt> intrinsic takes two arguments. Both | |
| the <tt>val</tt> argument and the result must be integers of the same bit | |
| width. The first argument, <tt>ptr</tt>, must be a pointer to a value of this | |
| integer type. The targets may only lower integer representations they | |
| support.</p> | |
| <h5>Semantics:</h5> | |
| <p>This intrinsic loads the value pointed to by <tt>ptr</tt>, yields it, and | |
| stores <tt>val</tt> back into <tt>ptr</tt> atomically. This provides the | |
| equivalent of an atomic swap operation within the SSA framework.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %ptr = malloc i32 | |
| store i32 4, %ptr | |
| %val1 = add i32 4, 4 | |
| %result1 = call i32 @llvm.atomic.swap.i32.p0i32( i32* %ptr, i32 %val1 ) | |
| <i>; yields {i32}:result1 = 4</i> | |
| %stored1 = icmp eq i32 %result1, 4 <i>; yields {i1}:stored1 = true</i> | |
| %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 8</i> | |
| %val2 = add i32 1, 1 | |
| %result2 = call i32 @llvm.atomic.swap.i32.p0i32( i32* %ptr, i32 %val2 ) | |
| <i>; yields {i32}:result2 = 8</i> | |
| %stored2 = icmp eq i32 %result2, 8 <i>; yields {i1}:stored2 = true</i> | |
| %memval2 = load i32* %ptr <i>; yields {i32}:memval2 = 2</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_atomic_load_add">'<tt>llvm.atomic.load.add.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.load.add</tt> on | |
| any integer bit width. Not all targets support all bit widths however.</p> | |
| <pre> | |
| declare i8 @llvm.atomic.load.add.i8..p0i8( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.add.i16..p0i16( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.add.i32..p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.add.i64..p0i64( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>This intrinsic adds <tt>delta</tt> to the value stored in memory | |
| at <tt>ptr</tt>. It yields the original value at <tt>ptr</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The intrinsic takes two arguments, the first a pointer to an integer value | |
| and the second an integer value. The result is also an integer value. These | |
| integer types can have any bit width, but they must all have the same bit | |
| width. The targets may only lower integer representations they support.</p> | |
| <h5>Semantics:</h5> | |
| <p>This intrinsic does a series of operations atomically. It first loads the | |
| value stored at <tt>ptr</tt>. It then adds <tt>delta</tt>, stores the result | |
| to <tt>ptr</tt>. It yields the original value stored at <tt>ptr</tt>.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %ptr = malloc i32 | |
| store i32 4, %ptr | |
| %result1 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 4 ) | |
| <i>; yields {i32}:result1 = 4</i> | |
| %result2 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 2 ) | |
| <i>; yields {i32}:result2 = 8</i> | |
| %result3 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 5 ) | |
| <i>; yields {i32}:result3 = 10</i> | |
| %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 15</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_atomic_load_sub">'<tt>llvm.atomic.load.sub.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.load.sub</tt> on | |
| any integer bit width and for different address spaces. Not all targets | |
| support all bit widths however.</p> | |
| <pre> | |
| declare i8 @llvm.atomic.load.sub.i8.p0i32( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.sub.i16.p0i32( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.sub.i32.p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.sub.i64.p0i32( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>This intrinsic subtracts <tt>delta</tt> to the value stored in memory at | |
| <tt>ptr</tt>. It yields the original value at <tt>ptr</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The intrinsic takes two arguments, the first a pointer to an integer value | |
| and the second an integer value. The result is also an integer value. These | |
| integer types can have any bit width, but they must all have the same bit | |
| width. The targets may only lower integer representations they support.</p> | |
| <h5>Semantics:</h5> | |
| <p>This intrinsic does a series of operations atomically. It first loads the | |
| value stored at <tt>ptr</tt>. It then subtracts <tt>delta</tt>, stores the | |
| result to <tt>ptr</tt>. It yields the original value stored | |
| at <tt>ptr</tt>.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %ptr = malloc i32 | |
| store i32 8, %ptr | |
| %result1 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 4 ) | |
| <i>; yields {i32}:result1 = 8</i> | |
| %result2 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 2 ) | |
| <i>; yields {i32}:result2 = 4</i> | |
| %result3 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 5 ) | |
| <i>; yields {i32}:result3 = 2</i> | |
| %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = -3</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_atomic_load_and">'<tt>llvm.atomic.load.and.*</tt>' Intrinsic</a><br> | |
| <a name="int_atomic_load_nand">'<tt>llvm.atomic.load.nand.*</tt>' Intrinsic</a><br> | |
| <a name="int_atomic_load_or">'<tt>llvm.atomic.load.or.*</tt>' Intrinsic</a><br> | |
| <a name="int_atomic_load_xor">'<tt>llvm.atomic.load.xor.*</tt>' Intrinsic</a><br> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>These are overloaded intrinsics. You can | |
| use <tt>llvm.atomic.load_and</tt>, <tt>llvm.atomic.load_nand</tt>, | |
| <tt>llvm.atomic.load_or</tt>, and <tt>llvm.atomic.load_xor</tt> on any integer | |
| bit width and for different address spaces. Not all targets support all bit | |
| widths however.</p> | |
| <pre> | |
| declare i8 @llvm.atomic.load.and.i8.p0i8( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.and.i16.p0i16( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.and.i32.p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.and.i64.p0i64( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <pre> | |
| declare i8 @llvm.atomic.load.or.i8.p0i8( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.or.i16.p0i16( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.or.i32.p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.or.i64.p0i64( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <pre> | |
| declare i8 @llvm.atomic.load.nand.i8.p0i32( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.nand.i16.p0i32( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.nand.i32.p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.nand.i64.p0i32( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <pre> | |
| declare i8 @llvm.atomic.load.xor.i8.p0i32( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.xor.i16.p0i32( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.xor.i32.p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.xor.i64.p0i32( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>These intrinsics bitwise the operation (and, nand, or, xor) <tt>delta</tt> to | |
| the value stored in memory at <tt>ptr</tt>. It yields the original value | |
| at <tt>ptr</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>These intrinsics take two arguments, the first a pointer to an integer value | |
| and the second an integer value. The result is also an integer value. These | |
| integer types can have any bit width, but they must all have the same bit | |
| width. The targets may only lower integer representations they support.</p> | |
| <h5>Semantics:</h5> | |
| <p>These intrinsics does a series of operations atomically. They first load the | |
| value stored at <tt>ptr</tt>. They then do the bitwise | |
| operation <tt>delta</tt>, store the result to <tt>ptr</tt>. They yield the | |
| original value stored at <tt>ptr</tt>.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %ptr = malloc i32 | |
| store i32 0x0F0F, %ptr | |
| %result0 = call i32 @llvm.atomic.load.nand.i32.p0i32( i32* %ptr, i32 0xFF ) | |
| <i>; yields {i32}:result0 = 0x0F0F</i> | |
| %result1 = call i32 @llvm.atomic.load.and.i32.p0i32( i32* %ptr, i32 0xFF ) | |
| <i>; yields {i32}:result1 = 0xFFFFFFF0</i> | |
| %result2 = call i32 @llvm.atomic.load.or.i32.p0i32( i32* %ptr, i32 0F ) | |
| <i>; yields {i32}:result2 = 0xF0</i> | |
| %result3 = call i32 @llvm.atomic.load.xor.i32.p0i32( i32* %ptr, i32 0F ) | |
| <i>; yields {i32}:result3 = FF</i> | |
| %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = F0</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_atomic_load_max">'<tt>llvm.atomic.load.max.*</tt>' Intrinsic</a><br> | |
| <a name="int_atomic_load_min">'<tt>llvm.atomic.load.min.*</tt>' Intrinsic</a><br> | |
| <a name="int_atomic_load_umax">'<tt>llvm.atomic.load.umax.*</tt>' Intrinsic</a><br> | |
| <a name="int_atomic_load_umin">'<tt>llvm.atomic.load.umin.*</tt>' Intrinsic</a><br> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>These are overloaded intrinsics. You can use <tt>llvm.atomic.load_max</tt>, | |
| <tt>llvm.atomic.load_min</tt>, <tt>llvm.atomic.load_umax</tt>, and | |
| <tt>llvm.atomic.load_umin</tt> on any integer bit width and for different | |
| address spaces. Not all targets support all bit widths however.</p> | |
| <pre> | |
| declare i8 @llvm.atomic.load.max.i8.p0i8( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.max.i16.p0i16( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.max.i32.p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.max.i64.p0i64( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <pre> | |
| declare i8 @llvm.atomic.load.min.i8.p0i8( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.min.i16.p0i16( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.min.i32..p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.min.i64..p0i64( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <pre> | |
| declare i8 @llvm.atomic.load.umax.i8.p0i8( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.umax.i16.p0i16( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.umax.i32.p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.umax.i64.p0i64( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <pre> | |
| declare i8 @llvm.atomic.load.umin.i8..p0i8( i8* <ptr>, i8 <delta> ) | |
| declare i16 @llvm.atomic.load.umin.i16.p0i16( i16* <ptr>, i16 <delta> ) | |
| declare i32 @llvm.atomic.load.umin.i32..p0i32( i32* <ptr>, i32 <delta> ) | |
| declare i64 @llvm.atomic.load.umin.i64..p0i64( i64* <ptr>, i64 <delta> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>These intrinsics takes the signed or unsigned minimum or maximum of | |
| <tt>delta</tt> and the value stored in memory at <tt>ptr</tt>. It yields the | |
| original value at <tt>ptr</tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>These intrinsics take two arguments, the first a pointer to an integer value | |
| and the second an integer value. The result is also an integer value. These | |
| integer types can have any bit width, but they must all have the same bit | |
| width. The targets may only lower integer representations they support.</p> | |
| <h5>Semantics:</h5> | |
| <p>These intrinsics does a series of operations atomically. They first load the | |
| value stored at <tt>ptr</tt>. They then do the signed or unsigned min or | |
| max <tt>delta</tt> and the value, store the result to <tt>ptr</tt>. They | |
| yield the original value stored at <tt>ptr</tt>.</p> | |
| <h5>Examples:</h5> | |
| <pre> | |
| %ptr = malloc i32 | |
| store i32 7, %ptr | |
| %result0 = call i32 @llvm.atomic.load.min.i32.p0i32( i32* %ptr, i32 -2 ) | |
| <i>; yields {i32}:result0 = 7</i> | |
| %result1 = call i32 @llvm.atomic.load.max.i32.p0i32( i32* %ptr, i32 8 ) | |
| <i>; yields {i32}:result1 = -2</i> | |
| %result2 = call i32 @llvm.atomic.load.umin.i32.p0i32( i32* %ptr, i32 10 ) | |
| <i>; yields {i32}:result2 = 8</i> | |
| %result3 = call i32 @llvm.atomic.load.umax.i32.p0i32( i32* %ptr, i32 30 ) | |
| <i>; yields {i32}:result3 = 8</i> | |
| %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 30</i> | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_general">General Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>This class of intrinsics is designed to be generic and has no specific | |
| purpose.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_var_annotation">'<tt>llvm.var.annotation</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.var.annotation</tt>' intrinsic.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first argument is a pointer to a value, the second is a pointer to a | |
| global string, the third is a pointer to a global string which is the source | |
| file name, and the last argument is the line number.</p> | |
| <h5>Semantics:</h5> | |
| <p>This intrinsic allows annotation of local variables with arbitrary strings. | |
| This can be useful for special purpose optimizations that want to look for | |
| these annotations. These have no other defined use, they are ignored by code | |
| generation and optimization.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_annotation">'<tt>llvm.annotation.*</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <p>This is an overloaded intrinsic. You can use '<tt>llvm.annotation</tt>' on | |
| any integer bit width.</p> | |
| <pre> | |
| declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int> ) | |
| declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int> ) | |
| declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int> ) | |
| declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int> ) | |
| declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.annotation</tt>' intrinsic.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first argument is an integer value (result of some expression), the | |
| second is a pointer to a global string, the third is a pointer to a global | |
| string which is the source file name, and the last argument is the line | |
| number. It returns the value of the first argument.</p> | |
| <h5>Semantics:</h5> | |
| <p>This intrinsic allows annotations to be put on arbitrary expressions with | |
| arbitrary strings. This can be useful for special purpose optimizations that | |
| want to look for these annotations. These have no other defined use, they | |
| are ignored by code generation and optimization.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_trap">'<tt>llvm.trap</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.trap() | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.trap</tt>' intrinsic.</p> | |
| <h5>Arguments:</h5> | |
| <p>None.</p> | |
| <h5>Semantics:</h5> | |
| <p>This intrinsics is lowered to the target dependent trap instruction. If the | |
| target does not have a trap instruction, this intrinsic will be lowered to | |
| the call of the <tt>abort()</tt> function.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_stackprotector">'<tt>llvm.stackprotector</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void @llvm.stackprotector( i8* <guard>, i8** <slot> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The <tt>llvm.stackprotector</tt> intrinsic takes the <tt>guard</tt> and | |
| stores it onto the stack at <tt>slot</tt>. The stack slot is adjusted to | |
| ensure that it is placed on the stack before local variables.</p> | |
| <h5>Arguments:</h5> | |
| <p>The <tt>llvm.stackprotector</tt> intrinsic requires two pointer | |
| arguments. The first argument is the value loaded from the stack | |
| guard <tt>@__stack_chk_guard</tt>. The second variable is an <tt>alloca</tt> | |
| that has enough space to hold the value of the guard.</p> | |
| <h5>Semantics:</h5> | |
| <p>This intrinsic causes the prologue/epilogue inserter to force the position of | |
| the <tt>AllocaInst</tt> stack slot to be before local variables on the | |
| stack. This is to ensure that if a local variable on the stack is | |
| overwritten, it will destroy the value of the guard. When the function exits, | |
| the guard on the stack is checked against the original guard. If they're | |
| different, then the program aborts by calling the <tt>__stack_chk_fail()</tt> | |
| function.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <hr> | |
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