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| <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> <font size=+5 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>LLVM Language Reference Manual</b></font></td> | |
| </tr></table> | |
| <ol> | |
| <li><a href="#abstract">Abstract</a> | |
| <li><a href="#introduction">Introduction</a> | |
| <li><a href="#identifiers">Identifiers</a> | |
| <li><a href="#typesystem">Type System</a> | |
| <ol> | |
| <li><a href="#t_primitive">Primitive Types</a> | |
| <ol> | |
| <li><a href="#t_classifications">Type Classifications</a> | |
| </ol> | |
| <li><a href="#t_derived">Derived Types</a> | |
| <ol> | |
| <li><a href="#t_array" >Array Type</a> | |
| <li><a href="#t_function">Function Type</a> | |
| <li><a href="#t_pointer">Pointer Type</a> | |
| <li><a href="#t_struct" >Structure Type</a> | |
| <!-- <li><a href="#t_packed" >Packed Type</a> --> | |
| </ol> | |
| </ol> | |
| <li><a href="#highlevel">High Level Structure</a> | |
| <ol> | |
| <li><a href="#modulestructure">Module Structure</a> | |
| <li><a href="#globalvars">Global Variables</a> | |
| <li><a href="#functionstructure">Function Structure</a> | |
| </ol> | |
| <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><a href="#i_br" >'<tt>br</tt>' Instruction</a> | |
| <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a> | |
| <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a> | |
| <li><a href="#i_unwind" >'<tt>unwind</tt>' Instruction</a> | |
| </ol> | |
| <li><a href="#binaryops">Binary Operations</a> | |
| <ol> | |
| <li><a href="#i_add" >'<tt>add</tt>' Instruction</a> | |
| <li><a href="#i_sub" >'<tt>sub</tt>' Instruction</a> | |
| <li><a href="#i_mul" >'<tt>mul</tt>' Instruction</a> | |
| <li><a href="#i_div" >'<tt>div</tt>' Instruction</a> | |
| <li><a href="#i_rem" >'<tt>rem</tt>' Instruction</a> | |
| <li><a href="#i_setcc">'<tt>set<i>cc</i></tt>' Instructions</a> | |
| </ol> | |
| <li><a href="#bitwiseops">Bitwise Binary Operations</a> | |
| <ol> | |
| <li><a href="#i_and">'<tt>and</tt>' Instruction</a> | |
| <li><a href="#i_or" >'<tt>or</tt>' Instruction</a> | |
| <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a> | |
| <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a> | |
| <li><a href="#i_shr">'<tt>shr</tt>' Instruction</a> | |
| </ol> | |
| <li><a href="#memoryops">Memory Access Operations</a> | |
| <ol> | |
| <li><a href="#i_malloc" >'<tt>malloc</tt>' Instruction</a> | |
| <li><a href="#i_free" >'<tt>free</tt>' Instruction</a> | |
| <li><a href="#i_alloca" >'<tt>alloca</tt>' Instruction</a> | |
| <li><a href="#i_load" >'<tt>load</tt>' Instruction</a> | |
| <li><a href="#i_store" >'<tt>store</tt>' Instruction</a> | |
| <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a> | |
| </ol> | |
| <li><a href="#otherops">Other Operations</a> | |
| <ol> | |
| <li><a href="#i_phi" >'<tt>phi</tt>' Instruction</a> | |
| <li><a href="#i_cast">'<tt>cast .. to</tt>' Instruction</a> | |
| <li><a href="#i_call" >'<tt>call</tt>' Instruction</a> | |
| <li><a href="#i_vanext">'<tt>vanext</tt>' Instruction</a> | |
| <li><a href="#i_vaarg" >'<tt>vaarg</tt>' Instruction</a> | |
| </ol> | |
| </ol> | |
| <li><a href="#intrinsics">Intrinsic Functions</a> | |
| <ol> | |
| <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a> | |
| <ol> | |
| <li><a href="#i_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a> | |
| <li><a href="#i_va_end" >'<tt>llvm.va_end</tt>' Intrinsic</a> | |
| <li><a href="#i_va_copy" >'<tt>llvm.va_copy</tt>' Intrinsic</a> | |
| </ol> | |
| </ol> | |
| <p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a> and <A href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></b><p> | |
| </ol> | |
| <!-- *********************************************************************** --> | |
| <p><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b> | |
| <a name="abstract">Abstract | |
| </b></font></td></tr></table><ul> | |
| <!-- *********************************************************************** --> | |
| <blockquote> | |
| This document is a reference manual for the LLVM assembly language. LLVM is | |
| an 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. | |
| </blockquote> | |
| <!-- *********************************************************************** --> | |
| </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b> | |
| <a name="introduction">Introduction | |
| </b></font></td></tr></table><ul> | |
| <!-- *********************************************************************** --> | |
| The LLVM code representation is designed to be used in three different forms: as | |
| an in-memory compiler IR, as an on-disk bytecode 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> | |
| The LLVM representation aims to be a 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> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="wellformed"><h4><hr size=0>Well Formedness</h4><ul> | |
| 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> | |
| <pre> | |
| %x = <a href="#i_add">add</a> int 1, %x | |
| </pre> | |
| ...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 bytecode. | |
| The violations pointed out by the verifier pass indicate bugs in transformation | |
| passes or input to the parser.<p> | |
| <!-- Describe the typesetting conventions here. --> | |
| <!-- *********************************************************************** --> | |
| </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b> | |
| <a name="identifiers">Identifiers | |
| </b></font></td></tr></table><ul> | |
| <!-- *********************************************************************** --> | |
| LLVM uses three different forms of identifiers, for different purposes:<p> | |
| <ol> | |
| <li>Numeric constants are represented as you would expect: 12, -3 123.421, etc. | |
| Floating point constants have an optional hexidecimal notation. | |
| <li>Named values are represented as a string of characters with a '%' prefix. | |
| For example, %foo, %DivisionByZero, %a.really.long.identifier. 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. In | |
| this way, anything except a <tt>"</tt> character can be used in a name. | |
| <li>Unnamed values are represented as an unsigned numeric value with a '%' | |
| prefix. For example, %12, %2, %44. | |
| </ol><p> | |
| LLVM requires the values start with a '%' sign 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> | |
| 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_cast">cast</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_uint">uint</a></tt>', etc...), and others. These reserved | |
| words cannot conflict with variable names, because none of them start with a '%' | |
| character.<p> | |
| Here is an example of LLVM code to multiply the integer variable '<tt>%X</tt>' | |
| by 8:<p> | |
| The easy way: | |
| <pre> | |
| %result = <a href="#i_mul">mul</a> uint %X, 8 | |
| </pre> | |
| After strength reduction: | |
| <pre> | |
| %result = <a href="#i_shl">shl</a> uint %X, ubyte 3 | |
| </pre> | |
| And the hard way: | |
| <pre> | |
| <a href="#i_add">add</a> uint %X, %X <i>; yields {uint}:%0</i> | |
| <a href="#i_add">add</a> uint %0, %0 <i>; yields {uint}:%1</i> | |
| %result = <a href="#i_add">add</a> uint %1, %1 | |
| </pre> | |
| 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>Unnamed temporaries are created when the result of a computation is not | |
| assigned to a named value. | |
| <li>Unnamed temporaries are numbered sequentially | |
| </ol><p> | |
| ...and it also show 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> | |
| The one non-intuitive notation for constants is the optional hexidecimal 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>' which is also supported by the parser. The only time hexadecimal | |
| floating point constants are useful (and the only time that they are generated | |
| by the disassembler) is when an FP constant has to be emitted that is not | |
| representable as a decimal floating point number exactly. For example, NaN's, | |
| infinities, and other special cases are represented in their IEEE hexadecimal | |
| format so that assembly and disassembly do not cause any bits to change in the | |
| constants.<p> | |
| <!-- *********************************************************************** --> | |
| </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b> | |
| <a name="typesystem">Type System | |
| </b></font></td></tr></table><ul> | |
| <!-- *********************************************************************** --> | |
| The LLVM type system is one of the most important features of the intermediate | |
| representation. Being typed enables a number of optimizations to be performed | |
| on the IR directly, without having to do extra analyses on the side before the | |
| transformation. A strong type system makes it easier to read the generated code | |
| and enables novel analyses and transformations that are not feasible to perform | |
| on normal three address code representations.<p> | |
| <!-- The written form for the type system was heavily influenced by the | |
| syntactic problems with types in the C language<sup><a | |
| href="#rw_stroustrup">1</a></sup>.<p> --> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="t_primitive">Primitive Types | |
| </b></font></td></tr></table><ul> | |
| The primitive types are the fundemental building blocks of the LLVM system. The | |
| current set of primitive types are as follows:<p> | |
| <table border=0 align=center><tr><td> | |
| <table border=1 cellspacing=0 cellpadding=4 align=center> | |
| <tr><td><tt>void</tt></td> <td>No value</td></tr> | |
| <tr><td><tt>ubyte</tt></td> <td>Unsigned 8 bit value</td></tr> | |
| <tr><td><tt>ushort</tt></td><td>Unsigned 16 bit value</td></tr> | |
| <tr><td><tt>uint</tt></td> <td>Unsigned 32 bit value</td></tr> | |
| <tr><td><tt>ulong</tt></td> <td>Unsigned 64 bit value</td></tr> | |
| <tr><td><tt>float</tt></td> <td>32 bit floating point value</td></tr> | |
| <tr><td><tt>label</tt></td> <td>Branch destination</td></tr> | |
| </table> | |
| </td><td valign=top> | |
| <table border=1 cellspacing=0 cellpadding=4 align=center> | |
| <tr><td><tt>bool</tt></td> <td>True or False value</td></tr> | |
| <tr><td><tt>sbyte</tt></td> <td>Signed 8 bit value</td></tr> | |
| <tr><td><tt>short</tt></td> <td>Signed 16 bit value</td></tr> | |
| <tr><td><tt>int</tt></td> <td>Signed 32 bit value</td></tr> | |
| <tr><td><tt>long</tt></td> <td>Signed 64 bit value</td></tr> | |
| <tr><td><tt>double</tt></td><td>64 bit floating point value</td></tr> | |
| </table> | |
| </td></tr></table><p> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="t_classifications"><h4><hr size=0>Type Classifications</h4><ul> | |
| These different primitive types fall into a few useful classifications:<p> | |
| <table border=1 cellspacing=0 cellpadding=4 align=center> | |
| <tr><td><a name="t_signed">signed</td> <td><tt>sbyte, short, int, long, float, double</tt></td></tr> | |
| <tr><td><a name="t_unsigned">unsigned</td><td><tt>ubyte, ushort, uint, ulong</tt></td></tr> | |
| <tr><td><a name="t_integer">integer</td><td><tt>ubyte, sbyte, ushort, short, uint, int, ulong, long</tt></td></tr> | |
| <tr><td><a name="t_integral">integral</td><td><tt>bool, ubyte, sbyte, ushort, short, uint, int, ulong, long</tt></td></tr> | |
| <tr><td><a name="t_floating">floating point</td><td><tt>float, double</tt></td></tr> | |
| <tr><td><a name="t_firstclass">first class</td><td><tt>bool, ubyte, sbyte, ushort, short,<br> uint, int, ulong, long, float, double, <a href="#t_pointer">pointer</a></tt></td></tr> | |
| </table><p> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="t_derived">Derived Types | |
| </b></font></td></tr></table><ul> | |
| 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> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="t_array"><h4><hr size=0>Array Type</h4><ul> | |
| <h5>Overview:</h5> | |
| 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> | |
| The number of elements is a constant integer value, elementtype may be any type | |
| with a size.<p> | |
| <h5>Examples:</h5> | |
| <ul> | |
| <tt>[40 x int ]</tt>: Array of 40 integer values.<br> | |
| <tt>[41 x int ]</tt>: Array of 41 integer values.<br> | |
| <tt>[40 x uint]</tt>: Array of 40 unsigned integer values.<p> | |
| </ul> | |
| Here are some examples of multidimensional arrays:<p> | |
| <ul> | |
| <table border=0 cellpadding=0 cellspacing=0> | |
| <tr><td><tt>[3 x [4 x int]]</tt></td><td>: 3x4 array integer values.</td></tr> | |
| <tr><td><tt>[12 x [10 x float]]</tt></td><td>: 12x10 array of single precision floating point values.</td></tr> | |
| <tr><td><tt>[2 x [3 x [4 x uint]]]</tt></td><td>: 2x3x4 array of unsigned integer values.</td></tr> | |
| </table> | |
| </ul> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="t_function"><h4><hr size=0>Function Type</h4><ul> | |
| <h5>Overview:</h5> | |
| The function type can be thought of as a function signature. It consists of a | |
| return type and a list of formal parameter types. Function types are usually | |
| used when to build virtual function tables (which are structures of pointers to | |
| functions), for indirect function calls, and when defining a function.<p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <returntype> (<parameter list>) | |
| </pre> | |
| Where '<tt><parameter list></tt>' is a comma-separated list of type | |
| specifiers. Optionally, the parameter list may include a type <tt>...</tt>, | |
| which indicates that the function takes a variable number of arguments. | |
| Variable argument functions can access their arguments with the <a | |
| href="#int_varargs">variable argument handling intrinsic</a> functions. | |
| <p> | |
| <h5>Examples:</h5> | |
| <ul> | |
| <table border=0 cellpadding=0 cellspacing=0> | |
| <tr><td><tt>int (int)</tt></td><td>: function taking an <tt>int</tt>, returning | |
| an <tt>int</tt></td></tr> | |
| <tr><td><tt>float (int, int *) *</tt></td><td>: <a href="#t_pointer">Pointer</a> | |
| to a function that takes an <tt>int</tt> and a <a href="#t_pointer">pointer</a> | |
| to <tt>int</tt>, returning <tt>float</tt>.</td></tr> | |
| <tr><td><tt>int (sbyte *, ...)</tt></td><td>: A vararg function that takes at | |
| least one <a href="#t_pointer">pointer</a> to <tt>sbyte</tt> (signed char in C), | |
| which returns an integer. This is the signature for <tt>printf</tt> in | |
| LLVM.</td></tr> | |
| </table> | |
| </ul> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="t_struct"><h4><hr size=0>Structure Type</h4><ul> | |
| <h5>Overview:</h5> | |
| 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> | |
| 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 border=0 cellpadding=0 cellspacing=0> | |
| <tr><td><tt>{ int, int, int }</tt></td><td>: a triple of three <tt>int</tt> | |
| values</td></tr> | |
| <tr><td><tt>{ float, int (int) * }</tt></td><td>: A pair, where the first | |
| element is a <tt>float</tt> and the second element is a <a | |
| href="#t_pointer">pointer</a> to a <a href="t_function">function</a> that takes | |
| an <tt>int</tt>, returning an <tt>int</tt>.</td></tr> | |
| </table> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="t_pointer"><h4><hr size=0>Pointer Type</h4><ul> | |
| <h5>Overview:</h5> | |
| As in many languages, the pointer type represents a pointer or reference to | |
| another object, which must live in memory.<p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <type> * | |
| </pre> | |
| <h5>Examples:</h5> | |
| <table border=0 cellpadding=0 cellspacing=0> | |
| <tr><td><tt>[4x int]*</tt></td><td>: <a href="#t_pointer">pointer</a> to <a | |
| href="#t_array">array</a> of four <tt>int</tt> values</td></tr> | |
| <tr><td><tt>int (int *) *</tt></td><td>: A <a href="#t_pointer">pointer</a> to a | |
| <a href="t_function">function</a> that takes an <tt>int</tt>, returning an | |
| <tt>int</tt>.</td></tr> | |
| </table> | |
| <p> | |
| <!-- _______________________________________________________________________ --> | |
| <!-- | |
| </ul><a name="t_packed"><h4><hr size=0>Packed Type</h4><ul> | |
| Mention/decide that packed types work with saturation or not. Maybe have a packed+saturated type in addition to just a packed type.<p> | |
| Packed types should be 'nonsaturated' because standard data types are not saturated. Maybe have a saturated packed type?<p> | |
| --> | |
| <!-- *********************************************************************** --> | |
| </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b> | |
| <a name="highlevel">High Level Structure | |
| </b></font></td></tr></table><ul> | |
| <!-- *********************************************************************** --> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="modulestructure">Module Structure | |
| </b></font></td></tr></table><ul> | |
| LLVM programs are composed of "Module"s, each of which is a translation unit of | |
| the input programs. Each module consists of functions, global variables, and | |
| symbol table entries. Modules may be combined together with the LLVM linker, | |
| which merges function (and global variable) definitions, resolves forward | |
| declarations, and merges symbol table entries. Here is an example of the "hello world" module:<p> | |
| <pre> | |
| <i>; Declare the string constant as a global constant...</i> | |
| <a href="#identifiers">%.LC0</a> = <a href="#linkage_internal">internal</a> <a href="#globalvars">constant</a> <a href="#t_array">[13 x sbyte]</a> c"hello world\0A\00" <i>; [13 x sbyte]*</i> | |
| <i>; External declaration of the puts function</i> | |
| <a href="#functionstructure">declare</a> int %puts(sbyte*) <i>; int(sbyte*)* </i> | |
| <i>; Definition of main function</i> | |
| int %main() { <i>; int()* </i> | |
| <i>; Convert [13x sbyte]* to sbyte *...</i> | |
| %cast210 = <a href="#i_getelementptr">getelementptr</a> [13 x sbyte]* %.LC0, long 0, long 0 <i>; sbyte*</i> | |
| <i>; Call puts function to write out the string to stdout...</i> | |
| <a href="#i_call">call</a> int %puts(sbyte* %cast210) <i>; int</i> | |
| <a href="#i_ret">ret</a> int 0 | |
| } | |
| </pre> | |
| This example is made up of a <a href="#globalvars">global variable</a> named | |
| "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>" function, and a | |
| <a href="#functionstructure">function definition</a> for "<tt>main</tt>".<p> | |
| <a name="linkage"> | |
| In general, a module is made up of a list of global values, where both functions | |
| and global variables are global values. Global values are represented by a | |
| pointer to a memory location (in this case, a pointer to an array of char, and a | |
| pointer to a function), and have one of the following linkage types:<p> | |
| <dl> | |
| <a name="linkage_internal"> | |
| <dt><tt><b>internal</b></tt> | |
| <dd>Global values with internal linkage are only directly accessible by objects | |
| in the current module. In particular, linking code into a module with an | |
| internal global value may cause the internal to be renamed as necessary to avoid | |
| collisions. Because the symbol is internal to the module, all references can be | |
| updated. This corresponds to the notion of the '<tt>static</tt>' keyword in C, | |
| or the idea of "anonymous namespaces" in C++.<p> | |
| <a name="linkage_linkonce"> | |
| <dt><tt><b>linkonce</b></tt>: | |
| <dd>"<tt>linkonce</tt>" linkage is similar to <tt>internal</tt> linkage, with | |
| the twist that linking together two modules defining the same <tt>linkonce</tt> | |
| globals will cause one of the globals to be discarded. This is typically used | |
| to implement inline functions. Unreferenced <tt>linkonce</tt> globals are | |
| allowed to be discarded.<p> | |
| <a name="linkage_weak"> | |
| <dt><tt><b>weak</b></tt>: | |
| <dd>"<tt>weak</tt>" linkage is exactly the same as <tt>linkonce</tt> linkage, | |
| except that unreferenced <tt>weak</tt> globals may not be discarded. This is | |
| used to implement constructs in C such as "<tt>int X;</tt>" at global scope.<p> | |
| <a name="linkage_appending"> | |
| <dt><tt><b>appending</b></tt>: | |
| <dd>"<tt>appending</tt>" linkage may only applied to global variables of pointer | |
| to array type. When two global variables with appending linkage are linked | |
| together, the two global arrays are appended together. This is the LLVM, | |
| typesafe, equivalent of having the system linker append together "sections" with | |
| identical names when .o files are linked.<p> | |
| <a name="linkage_external"> | |
| <dt><tt><b>externally visible</b></tt>: | |
| <dd>If none of the above identifiers are used, the global is externally visible, | |
| meaning that it participates in linkage and can be used to resolve external | |
| symbol references.<p> | |
| </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. It is illegal for a function | |
| <i>declaration</i> to have any linkage type other than "externally visible".<p> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="globalvars">Global Variables | |
| </b></font></td></tr></table><ul> | |
| Global variables define regions of memory allocated at compilation time instead | |
| of run-time. Global variables may optionally be initialized. A variable may | |
| be defined as a global "constant", which indicates that the contents of the | |
| variable will never be modified (opening options for optimization). Constants | |
| must always have an initial value.<p> | |
| As SSA values, global variables define pointer values that are in scope | |
| (i.e. they dominate) for all basic blocks in the program. Global variables | |
| always define a pointer to their "content" type because they describe a region | |
| of memory, and all memory objects in LLVM are accessed through pointers.<p> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="functionstructure">Functions | |
| </b></font></td></tr></table><ul> | |
| LLVM functions definitions are composed of a (possibly empty) argument list, an | |
| opening curly brace, a list of basic blocks, and a closing curly brace. LLVM | |
| function declarations are defined with the "<tt>declare</tt>" keyword, a | |
| function name and a function signature.<p> | |
| A function definition contains a list of basic blocks, forming the CFG for the | |
| function. Each basic block may optionally start with a label (giving the basic | |
| block a symbol table entry), contains a list of instructions, and ends with a <a | |
| href="#terminators">terminator</a> instruction (such as a branch or function | |
| return).<p> | |
| The first basic block in program is special in two ways: it is immediately | |
| executed on entrance to the function, and it is not allowed to have predecessor | |
| basic blocks (i.e. there can not be any branches to the entry block of a | |
| function). Because the block can have no predecessors, it also cannot have any | |
| <a href="#i_phi">PHI nodes</a>.<p> | |
| <!-- *********************************************************************** --> | |
| </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b> | |
| <a name="instref">Instruction Reference | |
| </b></font></td></tr></table><ul> | |
| <!-- *********************************************************************** --> | |
| The LLVM instruction set consists of several different classifications of | |
| instructions: <a href="#terminators">terminator instructions</a>, <a | |
| href="#binaryops">binary instructions</a>, <a href="#memoryops">memory | |
| instructions</a>, and <a href="#otherops">other instructions</a>.<p> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="terminators">Terminator Instructions | |
| </b></font></td></tr></table><ul> | |
| 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> | |
| There are five different terminator instructions: the '<a | |
| href="#i_ret"><tt>ret</tt></a>' instruction, the '<a | |
| href="#i_br"><tt>br</tt></a>' instruction, the '<a | |
| href="#i_switch"><tt>switch</tt></a>' instruction, the '<a | |
| href="#i_invoke"><tt>invoke</tt></a>' instruction, and the '<a | |
| href="#i_unwind"><tt>unwind</tt></a>' instruction.<p> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_ret"><h4><hr size=0>'<tt>ret</tt>' Instruction</h4><ul> | |
| <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> | |
| The '<tt>ret</tt>' instruction is used to return control flow (and a value) from | |
| a function, back to the caller.<p> | |
| There are two forms of the '<tt>ret</tt>' instructruction: one that returns a | |
| value and then causes control flow, and one that just causes control flow to | |
| occur.<p> | |
| <h5>Arguments:</h5> | |
| The '<tt>ret</tt>' instruction may return any '<a href="#t_firstclass">first | |
| class</a>' type. Notice that a function is not <a href="#wellformed">well | |
| formed</a> if there exists a '<tt>ret</tt>' instruction inside of the function | |
| that returns a value that does not match the return type of the function.<p> | |
| <h5>Semantics:</h5> | |
| When the '<tt>ret</tt>' instruction is executed, control flow returns back to | |
| the calling function's context. If the caller is a "<a | |
| href="#i_call"><tt>call</tt></a> instruction, execution continues at the | |
| instruction after the call. If the caller was an "<a | |
| href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues at the | |
| beginning "normal" of the destination block. If the instruction returns a | |
| value, that value shall set the call or invoke instruction's return value.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| ret int 5 <i>; Return an integer value of 5</i> | |
| ret void <i>; Return from a void function</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_br"><h4><hr size=0>'<tt>br</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| br bool <cond>, label <iftrue>, label <iffalse> | |
| br label <dest> <i>; Unconditional branch</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| 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> | |
| The conditional branch form of the '<tt>br</tt>' instruction takes a single | |
| '<tt>bool</tt>' value and two '<tt>label</tt>' values. The unconditional form | |
| of the '<tt>br</tt>' instruction takes a single '<tt>label</tt>' value as a | |
| target.<p> | |
| <h5>Semantics:</h5> | |
| Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>bool</tt>' | |
| argument is evaluated. If the value is <tt>true</tt>, control flows to the | |
| '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>, | |
| control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| Test: | |
| %cond = <a href="#i_setcc">seteq</a> int %a, %b | |
| br bool %cond, label %IfEqual, label %IfUnequal | |
| IfEqual: | |
| <a href="#i_ret">ret</a> int 1 | |
| IfUnequal: | |
| <a href="#i_ret">ret</a> int 0 | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_switch"><h4><hr size=0>'<tt>switch</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| switch uint <value>, label <defaultdest> [ int <val>, label &dest>, ... ] | |
| </pre> | |
| <h5>Overview:</h5> | |
| 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> | |
| The '<tt>switch</tt>' instruction uses three parameters: a '<tt>uint</tt>' | |
| 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.<p> | |
| <h5>Semantics:</h5> | |
| The <tt>switch</tt> instruction specifies a table of values and destinations. | |
| When the '<tt>switch</tt>' instruction is executed, this table is searched for | |
| the given value. If the value is found, the corresponding destination is | |
| branched to, otherwise the default value it transfered to.<p> | |
| <h5>Implementation:</h5> | |
| Depending on properties of the target machine and the particular <tt>switch</tt> | |
| instruction, this instruction may be code generated as a series of chained | |
| conditional branches, or with a lookup table.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <i>; Emulate a conditional br instruction</i> | |
| %Val = <a href="#i_cast">cast</a> bool %value to uint | |
| switch uint %Val, label %truedest [int 0, label %falsedest ] | |
| <i>; Emulate an unconditional br instruction</i> | |
| switch uint 0, label %dest [ ] | |
| <i>; Implement a jump table:</i> | |
| switch uint %val, label %otherwise [ int 0, label %onzero, | |
| int 1, label %onone, | |
| int 2, label %ontwo ] | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_invoke"><h4><hr size=0>'<tt>invoke</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = invoke <ptr to function ty> %<function ptr val>(<function args>) | |
| to label <normal label> except label <exception label> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>invoke</tt>' instruction causes control to transfer to a specified | |
| function, with the possibility of control flow transfer to either the | |
| '<tt>normal</tt>' <tt>label</tt> label or the '<tt>exception</tt>' | |
| <tt>label</tt>. If the callee function returns with the "<tt><a | |
| href="#i_ret">ret</a></tt>" instruction, control flow will return to the | |
| "normal" label. If the callee (or any indirect callees) returns with the "<a | |
| href="#i_unwind"><tt>unwind</tt></a>" instruction, control is interrupted, and | |
| continued at the dynamically nearest "except" label.<p> | |
| <h5>Arguments:</h5> | |
| This instruction requires several arguments:<p> | |
| <ol> | |
| <li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to | |
| function value being invoked. In most cases, this is a direct function | |
| invocation, but indirect <tt>invoke</tt>s are just as possible, branching off | |
| an arbitrary pointer to function value. | |
| <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a | |
| function to be invoked. | |
| <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>'<tt>normal label</tt>': the label reached when the called function executes | |
| a '<tt><a href="#i_ret">ret</a></tt>' instruction. | |
| <li>'<tt>exception label</tt>': the label reached when a callee returns with the | |
| <a href="#i_unwind"><tt>unwind</tt></a> instruction. | |
| </ol> | |
| <h5>Semantics:</h5> | |
| 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> | |
| This instruction is used in languages with destructors to ensure that proper | |
| cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown | |
| exception. Additionally, this is important for implementation of | |
| '<tt>catch</tt>' clauses in high-level languages that support them.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %retval = invoke int %Test(int 15) | |
| to label %Continue | |
| except label %TestCleanup <i>; {int}:retval set</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_unwind"><h4><hr size=0>'<tt>unwind</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| unwind | |
| </pre> | |
| <h5>Overview:</h5> | |
| 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. | |
| <h5>Semantics:</h5> | |
| The '<tt>unwind</tt>' intrinsic causes execution of the current function to | |
| immediately halt. The dynamic call stack is then searched for the first <a | |
| href="#i_invoke"><tt>invoke</tt></a> instruction on the call stack. Once found, | |
| execution continues at the "exceptional" destination block specified by the | |
| <tt>invoke</tt> instruction. If there is no <tt>invoke</tt> instruction in the | |
| dynamic call chain, undefined behavior results. | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="binaryops">Binary Operations | |
| </b></font></td></tr></table><ul> | |
| Binary operators are used to do most of the computation in a program. They | |
| require two operands, execute an operation on them, and produce a single value. | |
| The result value of a binary operator is not necessarily the same type as its | |
| operands.<p> | |
| There are several different binary operators:<p> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_add"><h4><hr size=0>'<tt>add</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = add <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>add</tt>' instruction returns the sum of its two operands.<p> | |
| <h5>Arguments:</h5> | |
| The two arguments to the '<tt>add</tt>' instruction must be either <a href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p> | |
| <h5>Semantics:</h5> | |
| The value produced is the integer or floating point sum of the two operands.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = add int 4, %var <i>; yields {int}:result = 4 + %var</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_sub"><h4><hr size=0>'<tt>sub</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = sub <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>sub</tt>' instruction returns the difference of its two operands.<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> | |
| The two arguments to the '<tt>sub</tt>' instruction must be either <a | |
| href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> | |
| values. Both arguments must have identical types.<p> | |
| <h5>Semantics:</h5> | |
| The value produced is the integer or floating point difference of the two | |
| operands.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = sub int 4, %var <i>; yields {int}:result = 4 - %var</i> | |
| <result> = sub int 0, %val <i>; yields {int}:result = -%var</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_mul"><h4><hr size=0>'<tt>mul</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = mul <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>mul</tt>' instruction returns the product of its two operands.<p> | |
| <h5>Arguments:</h5> | |
| The two arguments to the '<tt>mul</tt>' instruction must be either <a href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p> | |
| <h5>Semantics:</h5> | |
| The value produced is the integer or floating point product of the two | |
| operands.<p> | |
| There is no signed vs unsigned multiplication. The appropriate action is taken | |
| based on the type of the operand. <p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = mul int 4, %var <i>; yields {int}:result = 4 * %var</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_div"><h4><hr size=0>'<tt>div</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = div <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>div</tt>' instruction returns the quotient of its two operands.<p> | |
| <h5>Arguments:</h5> | |
| The two arguments to the '<tt>div</tt>' instruction must be either <a | |
| href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> | |
| values. Both arguments must have identical types.<p> | |
| <h5>Semantics:</h5> | |
| The value produced is the integer or floating point quotient of the two | |
| operands.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = div int 4, %var <i>; yields {int}:result = 4 / %var</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_rem"><h4><hr size=0>'<tt>rem</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = rem <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>rem</tt>' instruction returns the remainder from the division of its two operands.<p> | |
| <h5>Arguments:</h5> | |
| The two arguments to the '<tt>rem</tt>' instruction must be either <a href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p> | |
| <h5>Semantics:</h5> | |
| This returns the <i>remainder</i> of a division (where the result has the same | |
| sign as the divisor), not the <i>modulus</i> (where the result has the same sign | |
| as the dividend) of a value. For more information about the difference, see: <a | |
| href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The Math | |
| Forum</a>.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = rem int 4, %var <i>; yields {int}:result = 4 % %var</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_setcc"><h4><hr size=0>'<tt>set<i>cc</i></tt>' Instructions</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = seteq <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setne <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setlt <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setgt <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setle <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setge <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> The '<tt>set<i>cc</i></tt>' family of instructions returns a | |
| boolean value based on a comparison of their two operands.<p> | |
| <h5>Arguments:</h5> The two arguments to the '<tt>set<i>cc</i></tt>' | |
| instructions must be of <a href="#t_firstclass">first class</a> or <a | |
| href="#t_pointer">pointer</a> type (it is not possible to compare | |
| '<tt>label</tt>'s, '<tt>array</tt>'s, '<tt>structure</tt>' or '<tt>void</tt>' | |
| values, etc...). Both arguments must have identical types.<p> | |
| <h5>Semantics:</h5> | |
| The '<tt>seteq</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' value if | |
| both operands are equal.<br> | |
| The '<tt>setne</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' value if | |
| both operands are unequal.<br> | |
| The '<tt>setlt</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' value if | |
| the first operand is less than the second operand.<br> | |
| The '<tt>setgt</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' value if | |
| the first operand is greater than the second operand.<br> | |
| The '<tt>setle</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' value if | |
| the first operand is less than or equal to the second operand.<br> | |
| The '<tt>setge</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' value if | |
| the first operand is greater than or equal to the second operand.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = seteq int 4, 5 <i>; yields {bool}:result = false</i> | |
| <result> = setne float 4, 5 <i>; yields {bool}:result = true</i> | |
| <result> = setlt uint 4, 5 <i>; yields {bool}:result = true</i> | |
| <result> = setgt sbyte 4, 5 <i>; yields {bool}:result = false</i> | |
| <result> = setle sbyte 4, 5 <i>; yields {bool}:result = true</i> | |
| <result> = setge sbyte 4, 5 <i>; yields {bool}:result = false</i> | |
| </pre> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="bitwiseops">Bitwise Binary Operations | |
| </b></font></td></tr></table><ul> | |
| Bitwise binary operators are used to do various forms of bit-twiddling in a | |
| program. They are generally very efficient instructions, and can commonly be | |
| strength reduced from other instructions. They require two operands, execute an | |
| operation on them, and produce a single value. The resulting value of the | |
| bitwise binary operators is always the same type as its first operand.<p> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_and"><h4><hr size=0>'<tt>and</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = and <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>and</tt>' instruction returns the bitwise logical and of its two operands.<p> | |
| <h5>Arguments:</h5> | |
| The two arguments to the '<tt>and</tt>' instruction must be <a | |
| href="#t_integral">integral</a> values. Both arguments must have identical | |
| types.<p> | |
| <h5>Semantics:</h5> | |
| The truth table used for the '<tt>and</tt>' instruction is:<p> | |
| <center><table border=1 cellspacing=0 cellpadding=4> | |
| <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> | |
| </table></center><p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = and int 4, %var <i>; yields {int}:result = 4 & %var</i> | |
| <result> = and int 15, 40 <i>; yields {int}:result = 8</i> | |
| <result> = and int 4, 8 <i>; yields {int}:result = 0</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_or"><h4><hr size=0>'<tt>or</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = or <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> The '<tt>or</tt>' instruction returns the bitwise logical | |
| inclusive or of its two operands.<p> | |
| <h5>Arguments:</h5> | |
| The two arguments to the '<tt>or</tt>' instruction must be <a | |
| href="#t_integral">integral</a> values. Both arguments must have identical | |
| types.<p> | |
| <h5>Semantics:</h5> | |
| The truth table used for the '<tt>or</tt>' instruction is:<p> | |
| <center><table border=1 cellspacing=0 cellpadding=4> | |
| <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> | |
| </table></center><p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = or int 4, %var <i>; yields {int}:result = 4 | %var</i> | |
| <result> = or int 15, 40 <i>; yields {int}:result = 47</i> | |
| <result> = or int 4, 8 <i>; yields {int}:result = 12</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_xor"><h4><hr size=0>'<tt>xor</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = xor <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| 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> | |
| The two arguments to the '<tt>xor</tt>' instruction must be <a | |
| href="#t_integral">integral</a> values. Both arguments must have identical | |
| types.<p> | |
| <h5>Semantics:</h5> | |
| The truth table used for the '<tt>xor</tt>' instruction is:<p> | |
| <center><table border=1 cellspacing=0 cellpadding=4> | |
| <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> | |
| </table></center><p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = xor int 4, %var <i>; yields {int}:result = 4 ^ %var</i> | |
| <result> = xor int 15, 40 <i>; yields {int}:result = 39</i> | |
| <result> = xor int 4, 8 <i>; yields {int}:result = 12</i> | |
| <result> = xor int %V, -1 <i>; yields {int}:result = ~%V</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_shl"><h4><hr size=0>'<tt>shl</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = shl <ty> <var1>, ubyte <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>shl</tt>' instruction returns the first operand shifted to the left a | |
| specified number of bits. | |
| <h5>Arguments:</h5> | |
| The first argument to the '<tt>shl</tt>' instruction must be an <a | |
| href="#t_integer">integer</a> type. The second argument must be an | |
| '<tt>ubyte</tt>' type.<p> | |
| <h5>Semantics:</h5> | |
| The value produced is <tt>var1</tt> * 2<sup><tt>var2</tt></sup>.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = shl int 4, ubyte %var <i>; yields {int}:result = 4 << %var</i> | |
| <result> = shl int 4, ubyte 2 <i>; yields {int}:result = 16</i> | |
| <result> = shl int 1, ubyte 10 <i>; yields {int}:result = 1024</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_shr"><h4><hr size=0>'<tt>shr</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = shr <ty> <var1>, ubyte <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>shr</tt>' instruction returns the first operand shifted to the right a specified number of bits. | |
| <h5>Arguments:</h5> | |
| The first argument to the '<tt>shr</tt>' instruction must be an <a href="#t_integer">integer</a> type. The second argument must be an '<tt>ubyte</tt>' type.<p> | |
| <h5>Semantics:</h5> | |
| If the first argument is a <a href="#t_signed">signed</a> type, the most | |
| significant bit is duplicated in the newly free'd bit positions. If the first | |
| argument is unsigned, zero bits shall fill the empty positions.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <result> = shr int 4, ubyte %var <i>; yields {int}:result = 4 >> %var</i> | |
| <result> = shr uint 4, ubyte 1 <i>; yields {uint}:result = 2</i> | |
| <result> = shr int 4, ubyte 2 <i>; yields {int}:result = 1</i> | |
| <result> = shr sbyte 4, ubyte 3 <i>; yields {sbyte}:result = 0</i> | |
| <result> = shr sbyte -2, ubyte 1 <i>; yields {sbyte}:result = -1</i> | |
| </pre> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="memoryops">Memory Access Operations | |
| </b></font></td></tr></table><ul> | |
| 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> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_malloc"><h4><hr size=0>'<tt>malloc</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = malloc <type>, uint <NumElements> <i>; yields {type*}:result</i> | |
| <result> = malloc <type> <i>; yields {type*}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>malloc</tt>' instruction allocates memory from the system heap and returns a pointer to it.<p> | |
| <h5>Arguments:</h5> | |
| The the '<tt>malloc</tt>' instruction allocates | |
| <tt>sizeof(<type>)*NumElements</tt> bytes of memory from the operating | |
| system, and returns a pointer of the appropriate type to the program. The | |
| second form of the instruction is a shorter version of the first instruction | |
| that defaults to allocating one element.<p> | |
| '<tt>type</tt>' must be a sized type.<p> | |
| <h5>Semantics:</h5> | |
| Memory is allocated using the system "<tt>malloc</tt>" function, and a pointer | |
| is returned.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %array = malloc [4 x ubyte ] <i>; yields {[%4 x ubyte]*}:array</i> | |
| %size = <a href="#i_add">add</a> uint 2, 2 <i>; yields {uint}:size = uint 4</i> | |
| %array1 = malloc ubyte, uint 4 <i>; yields {ubyte*}:array1</i> | |
| %array2 = malloc [12 x ubyte], uint %size <i>; yields {[12 x ubyte]*}:array2</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_free"><h4><hr size=0>'<tt>free</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| free <type> <value> <i>; yields {void}</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>free</tt>' instruction returns memory back to the unused memory heap, to be reallocated in the future.<p> | |
| <h5>Arguments:</h5> | |
| '<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> | |
| Access to the memory pointed to by the pointer is not longer defined after this instruction executes.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %array = <a href="#i_malloc">malloc</a> [4 x ubyte] <i>; yields {[4 x ubyte]*}:array</i> | |
| free [4 x ubyte]* %array | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_alloca"><h4><hr size=0>'<tt>alloca</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = alloca <type>, uint <NumElements> <i>; yields {type*}:result</i> | |
| <result> = alloca <type> <i>; yields {type*}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>alloca</tt>' instruction allocates memory on the current stack frame of | |
| the procedure that is live until the current function returns to its caller.<p> | |
| <h5>Arguments:</h5> | |
| The the '<tt>alloca</tt>' instruction allocates | |
| <tt>sizeof(<type>)*NumElements</tt> bytes of memory on the runtime stack, | |
| returning a pointer of the appropriate type to the program. The second form of | |
| the instruction is a shorter version of the first that defaults to allocating | |
| one element.<p> | |
| '<tt>type</tt>' may be any sized type.<p> | |
| <h5>Semantics:</h5> | |
| Memory is allocated, a pointer is returned. '<tt>alloca</tt>'d memory is | |
| automatically released when the function returns. The '<tt>alloca</tt>' | |
| instruction is commonly used to represent automatic variables that must have an | |
| address available. When the function returns (either with the <tt><a | |
| href="#i_ret">ret</a></tt> or <tt><a href="#i_invoke">invoke</a></tt> | |
| instructions), the memory is reclaimed.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %ptr = alloca int <i>; yields {int*}:ptr</i> | |
| %ptr = alloca int, uint 4 <i>; yields {int*}:ptr</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_load"><h4><hr size=0>'<tt>load</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = load <ty>* <pointer> | |
| <result> = volatile load <ty>* <pointer> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>load</tt>' instruction is used to read from memory.<p> | |
| <h5>Arguments:</h5> | |
| The argument to the '<tt>load</tt>' instruction specifies the memory address to | |
| load from. The pointer must point to a <a href="t_firstclass">first class</a> | |
| type. If the <tt>load</tt> is marked as <tt>volatile</tt> then the optimizer is | |
| not allowed to modify the number or order of execution of this <tt>load</tt> | |
| with other volatile <tt>load</tt> and <tt><a href="#i_store">store</a></tt> | |
| instructions. <p> | |
| <h5>Semantics:</h5> | |
| The location of memory pointed to is loaded. | |
| <h5>Examples:</h5> | |
| <pre> | |
| %ptr = <a href="#i_alloca">alloca</a> int <i>; yields {int*}:ptr</i> | |
| <a href="#i_store">store</a> int 3, int* %ptr <i>; yields {void}</i> | |
| %val = load int* %ptr <i>; yields {int}:val = int 3</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_store"><h4><hr size=0>'<tt>store</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| store <ty> <value>, <ty>* <pointer> <i>; yields {void}</i> | |
| volatile store <ty> <value>, <ty>* <pointer> <i>; yields {void}</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>store</tt>' instruction is used to write to memory.<p> | |
| <h5>Arguments:</h5> | |
| There are two arguments to the '<tt>store</tt>' instruction: a value to store | |
| and an address to store it into. The type of the '<tt><pointer></tt>' | |
| operand must be a pointer to the type of the '<tt><value></tt>' operand. | |
| If the <tt>store</tt> is marked as <tt>volatile</tt> then the optimizer is not | |
| allowed to modify the number or order of execution of this <tt>store</tt> with | |
| other volatile <tt>load</tt> and <tt><a href="#i_store">store</a></tt> | |
| instructions.<p> | |
| <h5>Semantics:</h5> The contents of memory are updated to contain | |
| '<tt><value></tt>' at the location specified by the | |
| '<tt><pointer></tt>' operand.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %ptr = <a href="#i_alloca">alloca</a> int <i>; yields {int*}:ptr</i> | |
| <a href="#i_store">store</a> int 3, int* %ptr <i>; yields {void}</i> | |
| %val = load int* %ptr <i>; yields {int}:val = int 3</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_getelementptr"><h4><hr size=0>'<tt>getelementptr</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = getelementptr <ty>* <ptrval>{, long <aidx>|, ubyte <sidx>}* | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>getelementptr</tt>' instruction is used to get the address of a | |
| subelement of an aggregate data structure.<p> | |
| <h5>Arguments:</h5> | |
| This instruction takes a list of <tt>long</tt> values and <tt>ubyte</tt> | |
| constants that indicate what form of addressing to perform. The actual types of | |
| the arguments provided depend on the type of the first pointer argument. The | |
| '<tt>getelementptr</tt>' instruction is used to index down through the type | |
| levels of a structure.<p> | |
| For example, lets consider a C code fragment and how it gets compiled to | |
| LLVM:<p> | |
| <pre> | |
| struct RT { | |
| char A; | |
| int B[10][20]; | |
| char C; | |
| }; | |
| struct ST { | |
| int X; | |
| double Y; | |
| struct RT Z; | |
| }; | |
| int *foo(struct ST *s) { | |
| return &s[1].Z.B[5][13]; | |
| } | |
| </pre> | |
| The LLVM code generated by the GCC frontend is: | |
| <pre> | |
| %RT = type { sbyte, [10 x [20 x int]], sbyte } | |
| %ST = type { int, double, %RT } | |
| int* "foo"(%ST* %s) { | |
| %reg = getelementptr %ST* %s, long 1, ubyte 2, ubyte 1, long 5, long 13 | |
| ret int* %reg | |
| } | |
| </pre> | |
| <h5>Semantics:</h5> | |
| The index types specified for the '<tt>getelementptr</tt>' instruction depend on | |
| the pointer type that is being index into. <a href="t_pointer">Pointer</a> and | |
| <a href="t_array">array</a> types require '<tt>long</tt>' values, and <a | |
| href="t_struct">structure</a> types require '<tt>ubyte</tt>' | |
| <b>constants</b>.<p> | |
| In the example above, the first index is indexing into the '<tt>%ST*</tt>' type, | |
| which is a pointer, yielding a '<tt>%ST</tt>' = '<tt>{ int, double, %RT }</tt>' | |
| type, a structure. The second index indexes into the third element of the | |
| structure, yielding a '<tt>%RT</tt>' = '<tt>{ sbyte, [10 x [20 x int]], sbyte | |
| }</tt>' type, another structure. The third index indexes into the second | |
| element of the structure, yielding a '<tt>[10 x [20 x int]]</tt>' type, an | |
| array. The two dimensions of the array are subscripted into, yielding an | |
| '<tt>int</tt>' type. The '<tt>getelementptr</tt>' instruction return a pointer | |
| to this element, thus yielding a '<tt>int*</tt>' type.<p> | |
| Note that it is perfectly legal to index partially through a structure, | |
| returning a pointer to an inner element. Because of this, the LLVM code for the | |
| given testcase is equivalent to:<p> | |
| <pre> | |
| int* "foo"(%ST* %s) { | |
| %t1 = getelementptr %ST* %s , long 1 <i>; yields %ST*:%t1</i> | |
| %t2 = getelementptr %ST* %t1, long 0, ubyte 2 <i>; yields %RT*:%t2</i> | |
| %t3 = getelementptr %RT* %t2, long 0, ubyte 1 <i>; yields [10 x [20 x int]]*:%t3</i> | |
| %t4 = getelementptr [10 x [20 x int]]* %t3, long 0, long 5 <i>; yields [20 x int]*:%t4</i> | |
| %t5 = getelementptr [20 x int]* %t4, long 0, long 13 <i>; yields int*:%t5</i> | |
| ret int* %t5 | |
| } | |
| </pre> | |
| <h5>Example:</h5> | |
| <pre> | |
| <i>; yields [12 x ubyte]*:aptr</i> | |
| %aptr = getelementptr {int, [12 x ubyte]}* %sptr, long 0, ubyte 1 | |
| </pre> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="otherops">Other Operations | |
| </b></font></td></tr></table><ul> | |
| The instructions in this catagory are the "miscellaneous" instructions, which defy better classification.<p> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_phi"><h4><hr size=0>'<tt>phi</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = phi <ty> [ <val0>, <label0>], ... | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>phi</tt>' instruction is used to implement the φ node in the SSA | |
| graph representing the function.<p> | |
| <h5>Arguments:</h5> | |
| The type of the incoming values are specified with the first type field. After | |
| this, the '<tt>phi</tt>' instruction takes a list of pairs as arguments, with | |
| one pair for each predecessor basic block of the current block.<p> | |
| There must be no non-phi instructions between the start of a basic block and the | |
| PHI instructions: i.e. PHI instructions must be first in a basic block.<p> | |
| <h5>Semantics:</h5> | |
| At runtime, the '<tt>phi</tt>' instruction logically takes on the value | |
| specified by the parameter, depending on which basic block we came from in the | |
| last <a href="#terminators">terminator</a> instruction.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| Loop: ; Infinite loop that counts from 0 on up... | |
| %indvar = phi uint [ 0, %LoopHeader ], [ %nextindvar, %Loop ] | |
| %nextindvar = add uint %indvar, 1 | |
| br label %Loop | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_cast"><h4><hr size=0>'<tt>cast .. to</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = cast <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>cast</tt>' instruction is used as the primitive means to convert | |
| integers to floating point, change data type sizes, and break type safety (by | |
| casting pointers).<p> | |
| <h5>Arguments:</h5> | |
| The '<tt>cast</tt>' instruction takes a value to cast, which must be a first | |
| class value, and a type to cast it to, which must also be a first class type.<p> | |
| <h5>Semantics:</h5> | |
| This instruction follows the C rules for explicit casts when determining how the | |
| data being cast must change to fit in its new container.<p> | |
| When casting to bool, any value that would be considered true in the context of | |
| a C '<tt>if</tt>' condition is converted to the boolean '<tt>true</tt>' values, | |
| all else are '<tt>false</tt>'.<p> | |
| When extending an integral value from a type of one signness to another (for | |
| example '<tt>sbyte</tt>' to '<tt>ulong</tt>'), the value is sign-extended if the | |
| <b>source</b> value is signed, and zero-extended if the source value is | |
| unsigned. <tt>bool</tt> values are always zero extended into either zero or | |
| one.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = cast int 257 to ubyte <i>; yields ubyte:1</i> | |
| %Y = cast int 123 to bool <i>; yields bool:true</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_call"><h4><hr size=0>'<tt>call</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = call <ty>* <fnptrval>(<param list>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>call</tt>' instruction represents a simple function call.<p> | |
| <h5>Arguments:</h5> | |
| This instruction requires several arguments:<p> | |
| <ol> | |
| <li>'<tt>ty</tt>': shall be the signature of the pointer to function value being | |
| invoked. The argument types must match the types implied by this signature.<p> | |
| <li>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to be | |
| invoked. In most cases, this is a direct function invocation, but indirect | |
| <tt>call</tt>s are just as possible, calling an arbitrary pointer to function | |
| values.<p> | |
| <li>'<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. | |
| </ol> | |
| <h5>Semantics:</h5> | |
| The '<tt>call</tt>' instruction is used to cause control flow to transfer to a | |
| specified function, with its incoming arguments bound to the specified values. | |
| Upon a '<tt><a href="#i_ret">ret</a></tt>' instruction in the called function, | |
| control flow continues with the instruction after the function call, and the | |
| return value of the function is bound to the result argument. This is a simpler | |
| case of the <a href="#i_invoke">invoke</a> instruction.<p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %retval = call int %test(int %argc) | |
| call int(sbyte*, ...) *%printf(sbyte* %msg, int 12, sbyte 42); | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_vanext"><h4><hr size=0>'<tt>vanext</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <resultarglist> = vanext <va_list> <arglist>, <argty> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>vanext</tt>' instruction is used to access arguments passed through | |
| the "variable argument" area of a function call. It is used to implement the | |
| <tt>va_arg</tt> macro in C.<p> | |
| <h5>Arguments:</h5> | |
| This instruction takes a <tt>valist</tt> value and the type of the argument. It | |
| returns another <tt>valist</tt>. | |
| <h5>Semantics:</h5> | |
| The '<tt>vanext</tt>' instruction advances the specified <tt>valist</tt> past | |
| an argument of the specified type. In conjunction with the <a | |
| href="#i_vaarg"><tt>vaarg</tt></a> instruction, it is used to implement the | |
| <tt>va_arg</tt> macro available in C. For more information, see the variable | |
| argument handling <a href="#int_varargs">Intrinsic Functions</a>.<p> | |
| 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> | |
| <tt>vanext</tt> is an LLVM instruction instead of an <a | |
| href="#intrinsics">intrinsic function</a> because it takes an type as an | |
| argument.</p> | |
| <h5>Example:</h5> | |
| See the <a href="#int_varargs">variable argument processing</a> section.<p> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_vaarg"><h4><hr size=0>'<tt>vaarg</tt>' Instruction</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <resultval> = vaarg <va_list> <arglist>, <argty> | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>vaarg</tt>' instruction is used to access arguments passed through | |
| the "variable argument" area of a function call. It is used to implement the | |
| <tt>va_arg</tt> macro in C.<p> | |
| <h5>Arguments:</h5> | |
| This instruction takes a <tt>valist</tt> value and the type of the argument. It | |
| returns a value of the specified argument type. | |
| <h5>Semantics:</h5> | |
| The '<tt>vaarg</tt>' instruction loads an argument of the specified type from | |
| the specified <tt>va_list</tt>. In conjunction with the <a | |
| href="#i_vanext"><tt>vanext</tt></a> instruction, it is used to implement the | |
| <tt>va_arg</tt> macro available in C. For more information, see the variable | |
| argument handling <a href="#int_varargs">Intrinsic Functions</a>.<p> | |
| 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> | |
| <tt>vaarg</tt> is an LLVM instruction instead of an <a | |
| href="#intrinsics">intrinsic function</a> because it takes an type as an | |
| argument.</p> | |
| <h5>Example:</h5> | |
| See the <a href="#int_varargs">variable argument processing</a> section.<p> | |
| <!-- *********************************************************************** --> | |
| </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b> | |
| <a name="intrinsics">Intrinsic Functions | |
| </b></font></td></tr></table><ul> | |
| <!-- *********************************************************************** --> | |
| LLVM supports the notion of an "intrinsic function". These functions have well | |
| known names and semantics, and are required to follow certain restrictions. | |
| Overall, these instructions represent an extension mechanism for the LLVM | |
| language that does not require changing all of the transformations in LLVM to | |
| add to the language (or the bytecode reader/writer, the parser, etc...).<p> | |
| Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix, this | |
| prefix is reserved in LLVM for intrinsic names, thus functions may not be named | |
| this. Intrinsic functions must always be external functions: you cannot define | |
| the body of intrinsic functions. Intrinsic functions may only be used in call | |
| or invoke instructions: it is illegal to take the address of an intrinsic | |
| function. Additionally, because intrinsic functions are part of the LLVM | |
| language, it is required that they all be documented here if any are added.<p> | |
| Unless an intrinsic function is target-specific, there must be a lowering pass | |
| to eliminate the intrinsic or all backends must support the intrinsic | |
| function.<p> | |
| <!-- ======================================================================= --> | |
| </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0> | |
| <tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b> | |
| <a name="int_varargs">Variable Argument Handling Intrinsics | |
| </b></font></td></tr></table><ul> | |
| Variable argument support is defined in LLVM with the <a | |
| href="#i_vanext"><tt>vanext</tt></a> instruction and these three intrinsic | |
| functions. These functions are related to the similarly named macros defined in | |
| the <tt><stdarg.h></tt> header file.<p> | |
| All of these functions operate on arguments that use a target-specific value | |
| type "<tt>va_list</tt>". The LLVM assembly language reference manual does not | |
| define what this type is, so all transformations should be prepared to handle | |
| intrinsics with any type used.<p> | |
| This example shows how the <a href="#i_vanext"><tt>vanext</tt></a> instruction | |
| and the variable argument handling intrinsic functions are used.<p> | |
| <pre> | |
| int %test(int %X, ...) { | |
| ; Initialize variable argument processing | |
| %ap = call sbyte*()* %<a href="#i_va_start">llvm.va_start</a>() | |
| ; Read a single integer argument | |
| %tmp = vaarg sbyte* %ap, int | |
| ; Advance to the next argument | |
| %ap2 = vanext sbyte* %ap, int | |
| ; Demonstrate usage of llvm.va_copy and llvm.va_end | |
| %aq = call sbyte* (sbyte*)* %<a href="#i_va_copy">llvm.va_copy</a>(sbyte* %ap2) | |
| call void %<a href="#i_va_end">llvm.va_end</a>(sbyte* %aq) | |
| ; Stop processing of arguments. | |
| call void %<a href="#i_va_end">llvm.va_end</a>(sbyte* %ap2) | |
| ret int %tmp | |
| } | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_va_start"><h4><hr size=0>'<tt>llvm.va_start</tt>' Intrinsic</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| call va_list ()* %llvm.va_start() | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>llvm.va_start</tt>' intrinsic returns a new <tt><arglist></tt> | |
| for subsequent use by the variable argument intrinsics.<p> | |
| <h5>Semantics:</h5> | |
| The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt> | |
| macro available in C. In a target-dependent way, it initializes and returns a | |
| <tt>va_list</tt> element, so that the next <tt>vaarg</tt> will produce the first | |
| variable argument passed to the function. Unlike the C <tt>va_start</tt> macro, | |
| this intrinsic does not need to know the last argument of the function, the | |
| compiler can figure that out.<p> | |
| Note that this intrinsic function is only legal to be called from within the | |
| body of a variable argument function.<p> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_va_end"><h4><hr size=0>'<tt>llvm.va_end</tt>' Intrinsic</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| call void (va_list)* %llvm.va_end(va_list <arglist>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| The '<tt>llvm.va_end</tt>' intrinsic destroys <tt><arglist></tt> which has | |
| been initialized previously with <tt><a | |
| href="#i_va_start">llvm.va_start</a></tt> or <tt><a | |
| href="#i_va_copy">llvm.va_copy</a></tt>.<p> | |
| <h5>Arguments:</h5> | |
| The argument is a <tt>va_list</tt> to destroy.<p> | |
| <h5>Semantics:</h5> | |
| The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt> macro | |
| available in C. In a target-dependent way, it destroys the <tt>va_list</tt>. | |
| Calls to <a href="#i_va_start"><tt>llvm.va_start</tt></a> and <a | |
| href="#i_va_copy"><tt>llvm.va_copy</tt></a> must be matched exactly with calls | |
| to <tt>llvm.va_end</tt>.<p> | |
| <!-- _______________________________________________________________________ --> | |
| </ul><a name="i_va_copy"><h4><hr size=0>'<tt>llvm.va_copy</tt>' Intrinsic</h4><ul> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| call va_list (va_list)* %llvm.va_copy(va_list <destarglist>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| 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> | |
| The argument is the <tt>va_list</tt> to copy. | |
| <h5>Semantics:</h5> | |
| The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt> macro | |
| available in C. In a target-dependent way, it copies the source | |
| <tt>va_list</tt> element into the returned list. This intrinsic is necessary | |
| because the <tt><a href="i_va_start">llvm.va_start</a></tt> intrinsic may be | |
| arbitrarily complex and require memory allocation, for example.<p> | |
| <!-- *********************************************************************** --> | |
| </ul> | |
| <!-- *********************************************************************** --> | |
| <hr> | |
| <font size=-1> | |
| <address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address> | |
| <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a> | |
| <br> | |
| <!-- Created: Tue Jan 23 15:19:28 CST 2001 --> | |
| <!-- hhmts start --> | |
| Last modified: Tue Oct 21 10:43:36 CDT 2003 | |
| <!-- hhmts end --> | |
| </font> | |
| </body></html> |