<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
-<html><head><title>llvm Assembly Language Reference Manual</title></head>
+<html><head><title>LLVM Assembly Language Reference Manual</title></head>
<body bgcolor=white>
<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 Assembly Language Reference Manual</b></font></td>
+<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="#t_derived">Derived Types</a>
<ol>
<li><a href="#t_array" >Array Type</a>
- <li><a href="#t_method" >Method 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>
+ <!-- <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="#methodstructure">Method 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_callwith">'<tt>call .. with</tt>' Instruction</a>
- </ol>
- <li><a href="#unaryops">Unary Operations</a>
- <ol>
- <li><a href="#i_not" >'<tt>not</tt>' Instruction</a>
+ <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>
</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_icall">'<tt>icall</tt>' Instruction</a>
- <li><a href="#i_phi" >'<tt>phi</tt>' Instruction</a>
+ <li><a href="#i_vanext">'<tt>vanext</tt>' Instruction</a>
+ <li><a href="#i_vaarg" >'<tt>vaarg</tt>' Instruction</a>
</ol>
- <li><a href="#builtinfunc">Builtin Functions</a>
</ol>
- <li><a href="#todo">TODO List</a>
+ <li><a href="#intrinsics">Intrinsic Functions</a>
+ <ol>
+ <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a>
<ol>
- <li><a href="#exception">Exception Handling Instructions</a>
- <li><a href="#synchronization">Synchronization Instructions</a>
+ <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>
- <li><a href="#extensions">Possible Extensions</a>
- <ol>
- <li><a href="#i_tailcall">'<tt>tailcall</tt>' Instruction</a>
- <li><a href="#globalvars">Global Variables</a>
- <li><a href="#explicitparrellelism">Explicit Parrellelism</a>
- </ol>
- <li><a href="#related">Related Work</a>
+ </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>
+<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 describes the LLVM assembly language IR/VM. LLVM is an SSA
- based representation that attempts to be a useful midlevel IR by providing
- type safety, low level operations, flexibility, and the capability to
- represent 'all' high level languages cleanly.
+ 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>
+</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 is designed to exhibit a dual nature: on one hand, it is a useful compiler IR, on the other hand, it is a bytecode representation for dynamic compilation. We contend that this is a natural and good thing, making LLVM a natural form of communication between different compiler phases, and also between a static and dynamic compiler.<p>
-
-This dual nature leads to three different representations of LLVM (the human readable assembly representation, the compact bytecode representation, and the in memory, pointer based, representation). 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, type safe, 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. By providing type safety, 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>
+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>
+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 only a <tt><a href="#i_phi">phi</a></tt> node may refer to itself. The LLVM api provides a verification function (<tt>verify</tt>) that may be used to verify that a whole module or a single method is well formed. It is useful to validate whether an optimization pass performed a well formed transformation to the code.<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 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.
+<!-- 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>
+</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>
<!-- *********************************************************************** -->
<ol>
<li>Numeric constants are represented as you would expect: 12, -3 123.421, etc.
-<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>'.
-<li>Unnamed values are represented as an unsigned numeric value with a '%' prefix. For example, %12, %2, %44.
+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>
+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 may start with a '%' character.<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>
+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> int %X, 8
+ %result = <a href="#i_mul">mul</a> uint %X, 8
</pre>
After strength reduction:
<pre>
- %result = <a href="#i_shl">shl</a> int %X, ubyte 3
+ %result = <a href="#i_shl">shl</a> uint %X, ubyte 3
</pre>
And the hard way:
<pre>
- <a href="#i_add">add</a> int %X, %X <i>; yields {int}:%0</i>
- <a href="#i_add">add</a> int %0, %0 <i>; yields {int}:%1</i>
- %result = <a href="#i_add">add</a> int %1, %1
+ <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 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>
+...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>
+</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 important to the overall usefulness of the language and VM runtime. By being strongly typed, a number of optimizations may be performed on the IR directly, without having to do extra analysis to derive types. A strong type system also makes it easier to comprehend generated code and assists with safety concerns.<p>
+The LLVM type system is one of the most important features of the intermediate
+representation. Being typed enables a number of optimizations to be performed
+on the IR directly, without having to do extra analyses on the side before the
+transformation. A strong type system makes it easier to read the generated code
+and enables novel analyses and transformations that are not feasible to perform
+on normal three address code representations.<p>
-The assembly language form for the type system was heavily influenced by the type problems in the C language<sup><a href="#rw_stroustrup">1</a></sup>.<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>
+</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>
+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>
<tr><td><tt>label</tt></td> <td>Branch destination</td></tr>
</table>
-</td><td>
+</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>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>
-<tr><td><tt>lock</tt></td> <td>Recursive mutex value</td></tr>
</table>
</td></tr></table><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_integral">integral</td><td><tt>ubyte, sbyte, ushort, short, uint, int, ulong, long</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, uint, int, ulong, long, float, double, lock</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>
-
-
+The <a href="#t_firstclass">first class</a> types are perhaps the most
+important. Values of these types are the only ones which can be produced by
+instructions, passed as arguments, or used as operands to instructions. This
+means that all structures and arrays must be manipulated either by pointer or by
+component.<p>
<!-- ======================================================================= -->
<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, methods, 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>
+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>
<h5>Overview:</h5>
-The array type is a very simple derived type. It arranges elements sequentially in memory. There are two different forms of the array type:<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>
-<ol>
-<a name="t_array_fixed"><b><li>Fixed size array type:</b><br>
- The simplest form of the array type, has a size hard coded in as part of the type. Thus these are three distinct type qualifiers:<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>
-
-Fixed sized arrays are very useful for compiler optimization passes and for representing analysis results. Additionally, multidimensional arrays must have fixed sizes for all dimensions except the outer-most dimension.<p>
-
-<a name="t_array_unsized"><b><li>Dynamically sized array type:</b><br>
- The dynamically sized arrays are very similar to the fixed size arrays, except that the size of the array is calculated at runtime by the virtual machine. This is useful for representing generic methods that take any size array as an argument, or when representing Java style arrays.
-</ol><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>[[10 x int]]</tt></td><td>: Nx10 array of 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_
method"><h4><hr size=0>Method Type</h4><ul>
+</ul><a name="t_
function"><h4><hr size=0>Function Type</h4><ul>
<h5>Overview:</h5>
-The method type can be thought of as a method signature. It consists of a return type and a list of formal parameter types. Method types are usually used when to build virtual function tables (which are structures of pointers to methods) and for indirect method calls.<p>
+The function type can be thought of as a function signature. It consists of a
+return type and a list of formal parameter types. Function types are usually
+used 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 seperated list of type specifiers.<p>
+Where '<tt><parameter list></tt>' is a comma-separated list of type
+specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
+which indicates that the function takes a variable number of arguments.
+Variable argument functions can access their arguments with the <a
+href="#int_varargs">variable argument handling intrinsic</a> functions.
+<p>
<h5>Examples:</h5>
<ul>
<table border=0 cellpadding=0 cellspacing=0>
-<tr><td><tt>int (int)</tt></td><td>: method 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 method 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 (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>
<h5>Overview:</h5>
-The structure type is used to represent a collection of data members together in memory. Although the runtime is allowed to lay out the data members any way that it would like, they are guaranteed to be "close" to each other.<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>
-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>
+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>
<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_method">method</a> that takes an <tt>int</tt>, returning an <tt>int</tt>.</td></tr>
+
+<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>
+</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>
+</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>
-talk about the elements of a module: constant pool and method list.<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="methodstructure">Method Structure
+</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>
-talk about the constant pool<p>
-talk about how basic blocks delinate labels<p>
-talk about how basic blocks end with terminators<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>
+</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>
<!-- *********************************************************************** -->
-List all of the instructions, list valid types that they accept. Tell what they
-do and stuff also.
+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>
+</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>
-
-As was mentioned <a href="#methodstructure">previously</a>, every basic block in
-a program ends with a "Terminator" instruction. Additionally, all terminators yield a '<tt>void</tt>' value: they produce control flow, not values.<p>
-
-There are three different terminator instructions: the '<a href="#i_ret"><tt>ret</tt></a>' instruction, the '<a href="#i_br"><tt>br</tt></a>' instruction, and the '<a href="#i_switch"><tt>switch</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>
<!-- _______________________________________________________________________ -->
<h5>Syntax:</h5>
<pre>
- ret <type> <value> <i>; Return a value from a non-void method</i>
- ret void <i>; Return from void method</i>
+ 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 optionally a value) from a method, 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>
+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 method is not <a href="#wellformed">well formed</a> if there exists a '<tt>ret</tt>' instruction inside of the method that returns a value that does not match the return type of the method.<p>
+
+The '<tt>ret</tt>' instruction may return any '<a href="#t_firstclass">first
+class</a>' type. Notice that a function is not <a href="#wellformed">well
+formed</a> if there exists a '<tt>ret</tt>' instruction inside of the function
+that returns a value that does not match the return type of the function.<p>
<h5>Semantics:</h5>
-When the '<tt>ret</tt>' instruction is executed, control flow returns back to the calling method's context. If the instruction returns a value, that value shall be propogated into the calling method's data space.<p>
+
+When the '<tt>ret</tt>' instruction is executed, control flow returns back to
+the calling function's context. If the caller is a "<a
+href="#i_call"><tt>call</tt></a> instruction, execution continues at the
+instruction after the call. If the caller was an "<a
+href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues at the
+beginning "normal" of the destination block. If the instruction returns a
+value, that value shall set the call or invoke instruction's return value.<p>
+
<h5>Example:</h5>
<pre>
ret int 5 <i>; Return an integer value of 5</i>
- ret void <i>; Return from a void method</i>
+ ret void <i>; Return from a void function</i>
</pre>
</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 method. There are two forms of this instruction, corresponding to a conditional branch and an unconditional branch. The '<tt>br</tt>' instruction is a (useful) special case '<tt><a href="#i_switch">switch</a></tt>' instruction.<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>
-The conditional branch form of the '<tt>br</tt>' instruction shall take 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>
+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>
+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>
%cond = <a href="#i_setcc">seteq</a> int %a, %b
br bool %cond, label %IfEqual, label %IfUnequal
IfEqual:
- <a href="#i_ret">ret</a> bool true
+ <a href="#i_ret">ret</a> int 1
IfUnequal:
- <a href="#i_ret">ret</a> bool false
+ <a href="#i_ret">ret</a> int 0
</pre>
<h5>Syntax:</h5>
<pre>
- <i>; Definitions for lookup indirect branch</i>
- %switchtype = type [<anysize> x { uint, label }]
-
- <i>; Lookup indirect branch</i>
- switch uint <value>, label <defaultdest>, %switchtype <switchtable>
+ switch uint <value>, label <defaultdest> [ int <val>, label &dest>, ... ]
- <i>; Indexed indirect branch</i>
- switch uint <idxvalue>, label <defaultdest>, [<anysize> x label] <desttable>
</pre>
<h5>Overview:</h5>
-The '<tt>switch</tt>' instruction is used to transfer control flow to one of several different places. It is a simple generalization of the '<tt>br</tt>' instruction, and supports a strict superset of its functionality.<p>
-The '<tt>switch</tt>' statement supports two different styles of indirect branching: lookup branching and indexed branching. Lookup branching is generally useful if the values to switch on are spread far appart, where index branching is useful if the values to switch on are generally dense.<p>
-
-
The two different forms of the '<tt>switch</tt>' statement are simple hints to the underlying virtual machine implementation. For example, a virtual machine may choose to implement a small indirect branch table as a series of predicated comparisons: if it is faster for the target architecture.<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>
-The lookup form of the '<tt>switch</tt>' instruction uses three parameters: a '<tt>uint</tt>' comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination, and a sized array of pairs of comparison value constants and '<tt>label</tt>'s. The sized array must be a constant value.<p>
-The indexed form of the '<tt>switch</tt>' instruction uses three parameters: an '<tt>uint</tt>' index value, a default '<tt>label</tt>' and a sized array of '<tt>label</tt>'s. The '<tt>dests</tt>' array must be a constant array.
+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 lookup style switch statement 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. <p>
-The index branch form simply looks up a label element directly in a table and branches to it.<p>
+The <tt>switch</tt> instruction specifies a table of values and destinations.
+When the '<tt>switch</tt>' instruction is executed, this table is searched for
+the given value. If the value is found, the corresponding destination is
+branched to, otherwise the default value it transfered to.<p>
+
+<h5>Implementation:</h5>
-In either case, the compiler knows the static size of the array, because it is provided as part of the constant values type.<p>
+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, [1 x label] [label %falsedest ]
+ switch uint %Val, label %truedest [int 0, label %falsedest ]
<i>; Emulate an unconditional br instruction</i>
- switch uint 0, label %dest, [ 0 x label] [ ]
-
- <i>; Implement a jump table using the constant pool:</i>
- void "testmeth"(int %arg0)
- %switchdests = [3 x label] [ label %onzero, label %onone, label %ontwo ]
- {
- ...
- switch uint %val, label %otherwise, [3 x label] %switchdests...
- ...
- }
-
- <i>; Implement the equivilent jump table directly:</i>
- switch uint %val, label %otherwise, [3 x label] [ label %onzero,
- label %onone,
- label %ontwo ]
+ 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_
callwith"><h4><hr size=0>'<tt>call .. with</tt>' Instruction</h4><ul>
+</ul><a name="i_
invoke"><h4><hr size=0>'<tt>invoke</tt>' Instruction</h4><ul>
<h5>Syntax:</h5>
<pre>
- <result> = call <method ty> %<method name>(<method args>) with label <break label>
+ <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>call .. with</tt>' instruction is used to cause control flow to transfer to a specified method, with the possibility of control flow transfer to the '<tt>break label</tt>' label, in addition to the possibility of fallthrough to the next basic block. The '<tt><a href="#i_call">call</a></tt>' instruction is closely related, but does guarantees that control flow either never returns from the invoked method, or that it returns to the instruction succeeding the '<tt><a href="#i_call">call</a></tt>' instruction.<p>
-TODO: icall .. with needs to be defined as well for an indirect call.<p>
+The '<tt>invoke</tt>' instruction causes control to transfer to a specified
+function, with the possibility of control flow transfer to either the
+'<tt>normal</tt>' <tt>label</tt> label or the '<tt>exception</tt>'
+<tt>label</tt>. If the callee function returns with the "<tt><a
+href="#i_ret">ret</a></tt>" instruction, control flow will return to the
+"normal" label. If the callee (or any indirect callees) returns with the "<a
+href="#i_unwind"><tt>unwind</tt></a>" instruction, control is interrupted, and
+continued at the dynamically nearest "except" label.<p>
+
<h5>Arguments:</h5>
This instruction requires several arguments:<p>
<ol>
-<li>'<tt>method ty</tt>': shall be the signature of the named method being invoked. This must be a <a href="#t_method">method type</a>.
-<li>'<tt>method name</tt>': method name to be invoked.
-<li>'<tt>method args</tt>': argument list whose types match the method signature argument types.
-<li>'<tt>break label</tt>': a label that specifies the break label associated with this call.
-</ol>
-<h5>Semantics:</h5>
+<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.
-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 assiciates a label with the method invocation that may be accessed via the runtime library provided by the execution environment. 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>
+<li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a
+function to be invoked.
-For a more comprehensive explanation of this instruction look in the llvm/docs/2001-05-18-ExceptionHandling.txt document.
-
-<h5>Example:</h5>
-<pre>
- %retval = call int (int) %Test(int 15) with label %TestCleanup <i>; {int}:retval set</i>
-</pre>
+<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>
-<!-- ======================================================================= -->
-</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="unaryops">Unary Operations
-</b></font></td></tr></table><ul>
+<h5>Semantics:</h5>
-Unary operators are used to do a simple operation to a single value.<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>
-There is only one unary operators: the '<a href="#i_not"><tt>not</tt></a>' instruction.<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_
not"><h4><hr size=0>'<tt>not</tt>' Instruction</h4><ul>
+</ul><a name="i_
unwind"><h4><hr size=0>'<tt>unwind</tt>' Instruction</h4><ul>
<h5>Syntax:</h5>
<pre>
- <result> = not <ty> <var> <i>; yields {ty}:result</i>
+ unwind
</pre>
<h5>Overview:</h5>
-The '<tt>not</tt>' instruction returns the <a href="#logical_integrals">logical</a> inverse of its operand.<p>
-
-<h5>Arguments:</h5>
-The single argument to '<tt>not</tt>' must be of of <a href="#t_integral">integral</a> type.<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.
<h5>Semantics:</h5>
-The '<tt>not</tt>' instruction returns the <a href="#logical_integrals">logical</a> inverse of an <a href="#t_integral">integral</a> type.<p>
-
-Note that the '<tt>not</tt>' instruction is is not defined over to '<tt>bool</tt>' type. To invert a boolean value, the recommended method is to use:<p>
-<pre>
- <result> = xor bool true, <var> <i>; yields {bool}:result</i>
-</pre>
-
-<h5>Example:</h5>
-<pre>
- %x = not int 1 <i>; {int}:x is now equal to 0</i>
- %x = not bool true <i>; {bool}:x is now equal to false</i>
-</pre>
+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.
<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 neccesarily the same type as its operands.<p>
+Binary operators are used to do most of the computation in a program. They
+require two operands, execute an operation on them, and produce a single value.
+The result value of a binary operator is not necessarily the same type as its
+operands.<p>
There are several different binary operators:<p>
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_integ
ral">integral</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p>
+The two arguments to the '<tt>add</tt>' instruction must be either <a href="#t_integ
er">integer</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p>
<h5>Semantics:</h5>
-...<p>
+
+The value produced is the integer or floating point sum of the two operands.<p>
<h5>Example:</h5>
<pre>
</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 the cannonical way the '<tt>neg</tt>' instruction is represented as well.<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_integral">integral</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p>
+
+The two arguments to the '<tt>sub</tt>' instruction must be either <a
+href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
+values. Both arguments must have identical types.<p>
<h5>Semantics:</h5>
-...<p>
+
+The value produced is the integer or floating point difference of the two
+operands.<p>
<h5>Example:</h5>
<pre>
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_integ
ral">integral</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p>
+The two arguments to the '<tt>mul</tt>' instruction must be either <a href="#t_integ
er">integer</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p>
<h5>Semantics:</h5>
-...<p>
-There is no signed vs unsigned multiplication. The appropriate action is taken based on the type of the operand. <p>
+
+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>
<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_integral">integral</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p>
+
+The two arguments to the '<tt>div</tt>' instruction must be either <a
+href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
+values. Both arguments must have identical types.<p>
<h5>Semantics:</h5>
-...<p>
+
+The value produced is the integer or floating point quotient of the two
+operands.<p>
<h5>Example:</h5>
<pre>
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_integ
ral">integral</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p>
+The two arguments to the '<tt>rem</tt>' instruction must be either <a href="#t_integ
er">integer</a> or <a href="#t_floating">floating point</a> values. Both arguments must have identical types.<p>
<h5>Semantics:</h5>
-TODO: remainder or modulus?<p>
-...<p>
+
+This returns the <i>remainder</i> of a division (where the result has the same
+sign as the divisor), not the <i>modulus</i> (where the result has the same sign
+as the dividend) of a value. For more information about the difference, see: <a
+href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The Math
+Forum</a>.<p>
<h5>Example:</h5>
<pre>
<result> = 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>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_derived">derived</a> type (it is not possible to compare '<tt>label</tt>'s or '<tt>void</tt>' values). Both arguments must have identical types.<p>
-
-The '<tt>setlt</tt>', '<tt>setgt</tt>', '<tt>setle</tt>', and '<tt>setge</tt>' instructions do not operate on '<tt>bool</tt>' typed arguments.<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> 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>
+
+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>
<!-- ======================================================================= -->
-</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>
+</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>
+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>
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 either <a href="#t_integral">integral</a> or <a href="#t_bool"><tt>bool</tt></a> values. Both arguments must have identical types.<p>
+
+The two arguments to the '<tt>and</tt>' instruction must be <a
+href="#t_integral">integral</a> values. Both arguments must have identical
+types.<p>
<h5>Semantics:</h5>
-...<p>
+
+The truth table used for the '<tt>and</tt>' instruction is:<p>
+
+<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>
<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>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 either <a href="#t_integral">integral</a> or <a href="#t_bool"><tt>bool</tt></a> values. Both arguments must have identical types.<p>
+
+The two arguments to the '<tt>or</tt>' instruction must be <a
+href="#t_integral">integral</a> values. Both arguments must have identical
+types.<p>
<h5>Semantics:</h5>
-...<p>
+
+The truth table used for the '<tt>or</tt>' instruction is:<p>
+
+<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>
<h5>Overview:</h5>
-The '<tt>xor</tt>' instruction returns the bitwise logical exclusive or of its two operands.<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>
-The two arguments to the '<tt>xor</tt>' instruction must be either <a href="#t_integral">integral</a> or <a href="#t_bool"><tt>bool</tt></a> values. Both arguments must have identical types.<p>
+
+The two arguments to the '<tt>xor</tt>' instruction must be <a
+href="#t_integral">integral</a> values. Both arguments must have identical
+types.<p>
<h5>Semantics:</h5>
-...<p>
+
+The truth table used for the '<tt>xor</tt>' instruction is:<p>
+
+<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>
<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>
</pre>
<h5>Overview:</h5>
-The '<tt>shl</tt>' instruction returns the first operand shifted to the left a specified number of bits.
+
+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_integral">integral</a> type. The second argument must be an '<tt>ubyte</tt>' type.<p>
+
+The first argument to the '<tt>shl</tt>' instruction must be an <a
+href="#t_integer">integer</a> type. The second argument must be an
+'<tt>ubyte</tt>' type.<p>
<h5>Semantics:</h5>
-... 0 bits are shifted into the emptied bit positions...<p>
+
+The value produced is <tt>var1</tt> * 2<sup><tt>var2</tt></sup>.<p>
<h5>Example:</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_integ
ral">integral</a> type. The second argument must be an '<tt>ubyte</tt>' type.<p>
+The first argument to the '<tt>shr</tt>' instruction must be an <a href="#t_integ
er">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, zeros shall fill the empty positions...<p>
+
+If the first argument is a <a href="#t_signed">signed</a> type, the most
+significant bit is duplicated in the newly free'd bit positions. If the first
+argument is unsigned, zero bits shall fill the empty positions.<p>
<h5>Example:</h5>
<pre>
<result> = shr int 4, ubyte %var <i>; yields {int}:result = 4 >> %var</i>
- <result> = shr int 4, ubyte 1 <i>; yields {int}:result = 2</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 int 4, ubyte 3 <i>; yields {int}:result = 0</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>
+</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>
-Accessing memory in SSA form is, well, sticky at best. This section describes how to read and write memory in LLVM.<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>
<!-- _______________________________________________________________________ -->
<h5>Syntax:</h5>
<pre>
- <result> = malloc <type> <i>; yields { type *}:result</i>
- <result> = malloc [<type>], uint <NumElements> <i>; yields {[type] *}:result</i>
+ <result> = malloc <type>, uint <NumElements> <i>; yields {type*}:result</i>
+ <result> = malloc <type> <i>; yields {type*}:result</i>
</pre>
<h5>Overview:</h5>
<h5>Arguments:</h5>
-There are two forms of the '<tt>malloc</tt>' instruction, one for allocating a variable of a fixed type, and one for allocating an array. The array form is used to allocate an array, where the upper bound is not known until run time. If the upper bound is known at compile time, it is recommended that the first form be used with a <a href="#t_array_fixed">sized array type</a>.<p>
+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>' m
ay be any type except for a <a href="#t_array_unsized">unsized array type</a>.<p>
+'<tt>type</tt>' m
ust be a sized type.<p>
<h5>Semantics:</h5>
-Memory is allocated, a pointer is returned.<p>
+
+Memory is allocated using the system "<tt>malloc</tt>" function, and a pointer
+is returned.<p>
<h5>Example:</h5>
<pre>
%array = malloc [4 x ubyte ] <i>; yields {[%4 x ubyte]*}:array</i>
%size = <a href="#i_add">add</a> uint 2, 2 <i>; yields {uint}:size = uint 4</i>
- %array1 = malloc [ubyte], uint 4 <i>; yields {[ubyte]*}:array1</i>
- %array2 = malloc [ubyte], uint %size <i>; yields {[ubyte]*}:array2</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>
<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>
+'<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>
-Memory is available for use after this point. The contents of the '<tt>value</tt>' pointer are undefined after this instruction.<p>
+Access to the memory pointed to by the pointer is not longer defined after this instruction executes.<p>
<h5>Example:</h5>
<pre>
<h5>Syntax:</h5>
<pre>
- <result> = alloca <type> <i>; yields {type*}:result</i>
- <result> = alloca [<type>], uint <NumElements> <i>; yields {[type] *}:result</i>
+ <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 as long as the method does not return.<p>
+The '<tt>alloca</tt>' instruction allocates memory on the current stack frame of
+the procedure that is live until the current function returns to its caller.<p>
<h5>Arguments:</h5>
-There are two forms of the '<tt>alloca</tt>' instruction, one for allocating a variable of a fixed type, and one for allocating an array. The array form is used to allocate an array, where the upper bound is not known until run time. If the upper bound is known at compile time, it is recommended that the first form be used with a <a href="#t_array_fixed">sized array type</a>.<p>
-
-'<tt>type</tt>' may be any type except for a <a href="#t_array_unsized">unsized array type</a>.<p>
-Note that a virtual machine may generate more efficient native code for a method if all of the fixed size '<tt>alloca</tt>' instructions live in the first basic block of that method.
+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 method returns. The '<tt>alloca</tt>' utility is how variable spills shall be implemented.<p>
+
+Memory is allocated, a pointer is returned. '<tt>alloca</tt>'d memory is
+automatically released when the function returns. The '<tt>alloca</tt>'
+instruction is commonly used to represent automatic variables that must have an
+address available. When the function returns (either with the <tt><a
+href="#i_ret">ret</a></tt> or <tt><a href="#i_invoke">invoke</a></tt>
+instructions), the memory is reclaimed.<p>
<h5>Example:</h5>
<pre>
%ptr = alloca int <i>; yields {int*}:ptr</i>
- %ptr = alloca [int], uint 4 <i>; yields {[int]*}:ptr</i>
+ %ptr = alloca int, uint 4 <i>; yields {int*}:ptr</i>
</pre>
<h5>Syntax:</h5>
<pre>
- <result> = load <ty>* <pointer> <i>; yields {ty}:result</i>
- <result> = load <ty>* <arrayptr>{, uint <idx>}+ <i>; yields {ty}:result</i>
- <result> = load <ty>* <structptr>{, ubyte <idx>}+ <i>; yields field type</i>
+ <result> = load <ty>* <pointer>
+ <result> = volatile load <ty>* <pointer>
</pre>
<h5>Overview:</h5>
<h5>Arguments:</h5>
-There are three forms of the '<tt>load</tt>' instruction: one for reading from a general pointer, one for reading from a pointer to an array, and one for reading from a pointer to a structure.<p>
-
-In the first form, '<tt><ty></tt>' must be a pointer to a simple type (a primitive type or another pointer).<p>
-
-In the second form, '<tt><ty></tt>' must be a pointer to an array, and a list of one or more indices is provided as indexes into the (possibly multidimensional) array. No bounds checking is performed on array reads.<p>
-
-In the third form, the pointer must point to a (possibly nested) structure. There shall be one ubyte argument for each level of dereferencing involved.<p>
+The argument to the '<tt>load</tt>' instruction specifies the memory address to
+load from. The pointer must point to a <a href="t_firstclass">first class</a>
+type. If the <tt>load</tt> is marked as <tt>volatile</tt> then the optimizer is
+not allowed to modify the number or order of execution of this <tt>load</tt>
+with other volatile <tt>load</tt> and <tt><a href="#i_store">store</a></tt>
+instructions. <p>
<h5>Semantics:</h5>
-...
+
+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>
-
- %array = <a href="#i_malloc">malloc</a> [4 x ubyte] <i>; yields {[4 x ubyte]*}:array</i>
- <a href="#i_store">store</a> ubyte 124, [4 x ubyte]* %array, uint 4
- %val = load [4 x ubyte]* %array, uint 4 <i>; yields {ubyte}:val = ubyte 124</i>
- %val = load {{int, float}}* %stptr, 0, 1 <i>; yields {float}:val</i>
</pre>
<h5>Syntax:</h5>
<pre>
store <ty> <value>, <ty>* <pointer> <i>; yields {void}</i>
- store <ty> <value>, <ty>* <arrayptr>{, uint <idx>}+ <i>; yields {void}</i>
- store <ty> <value>, <ty>* <structptr>{, ubyte <idx>}+ <i>; yields {void}e</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 three forms of the '<tt>store</tt>' instruction: one for writing through a general pointer, one for writing through a pointer to a (possibly multidimensional) array, and one for writing to an element of a (potentially nested) structure.<p>
-The semantics of this instruction closely match that of the <a href="#i_load">load</a> instruction, except that memory is written to, not read from.
+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>
-...
+<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>
-
- %array = <a href="#i_malloc">malloc</a> [4 x ubyte] <i>; yields {[4 x ubyte]*}:array</i>
- <a href="#i_store">store</a> ubyte 124, [4 x ubyte]* %array, uint 4
- %val = load [4 x ubyte]* %array, uint 4 <i>; yields {ubyte}:val = ubyte 124</i>
- %val = load {{int, float}}* %stptr, 0, 1 <i>; yields {float}:val</i>
</pre>
<h5>Syntax:</h5>
<pre>
- <result> = getelementptr <ty>* <arrayptr>{, uint <idx>}+ <i>; yields {ty*}:result</i>
- <result> = getelementptr <ty>* <structptr>{, ubyte <idx>}+ <i>; yields field type*</i>
+ <result> = getelementptr <ty>* <ptrval>{, long <aidx>|, ubyte <sidx>}*
</pre>
<h5>Overview:</h5>
-'<tt>getelementptr</tt>' performs all of the same work that a '<tt><a href="#i_load">load</a>' instruction does, except for the actual memory fetch. Instead, '<tt>getelementpr</tt>' simply performs the addressing arithmetic to get to the element in question, and returns it. This is useful for indexing into a bimodal structure.
+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>
- %aptr = getelementptr {int, [12 x ubyte]}* %sptr, 1 <i>; yields {[12 x ubyte]*}:aptr</i>
- %ub = load [12x ubyte]* %aptr, 4 <i>;yields {ubyte}:ub</i>
+ <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>
+</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"
functions, that defy better classification.<p>
+The instructions in this catagory are the "miscellaneous"
instructions, which defy better classification.<p>
<!-- _______________________________________________________________________ -->
-</ul><a name="i_cast"><h4><hr size=0>'<tt>cast .. to</tt>' Instruction</h4><ul>
-
-<h1>TODO</h1>
-
-<a name="logical_integrals">
- Talk about what is considered true or false for integrals.
-
-
+</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. Only values of
+<a href="#t_firstclass">first class</a> type may be used as the value arguments
+to the PHI node. Only labels be used as the label arguments.<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_ca
ll"><h4><hr size=0>'<tt>call</tt>' Instruction</h4><ul>
+</ul><a name="i_ca
st"><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 <a
+href="#t_firstclass">first class</a> 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>
- %retval = call int %test(int %argc)
+ %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_icall"><h3><hr size=0>'<tt>icall</tt>' Instruction</h3><ul>
-
-Indirect calls are desperately needed to implement virtual function tables (C++, java) and function pointers (C, C++, ...).<p>
-A new instruction <tt>icall</tt> or similar should be introduced to represent an indirect call.<p>
+<!-- _______________________________________________________________________ -->
+</ul><a name="i_call"><h4><hr size=0>'<tt>call</tt>' Instruction</h4><ul>
-Example:
+<h5>Syntax:</h5>
<pre>
- %retval = icall int %funcptr(int %arg1) <i>; yields {int}:%retval</i>
+ <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_
phi"><h4><hr size=0>'<tt>phi</tt>' Instruction</h4><ul>
+</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>
-<pre>
-</pre>
+See the <a href="#int_varargs">variable argument processing</a> section.<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="builtinfunc">Builtin Functions
-</b></font></td></tr></table><ul>
-<b>Notice:</b> Preliminary idea!<p>
-Builtin functions are very similar to normal functions, except they are defined by the implementation. Invocations of these functions are very similar to method invocations, except that the syntax is a little less verbose.<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>
-Builtin functions are useful to implement semi-high level ideas like a '<tt>min</tt>' or '<tt>max</tt>' operation that can have important properties when doing program analysis. For example:
+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>
-<ul>
-<li>Some optimizations can make use of identities defined over the functions,
- for example a parrallelizing compiler could make use of '<tt>min</tt>'
- identities to parrellelize a loop.
-<li>Builtin functions would have polymorphic types, where normal method calls
- may only have a single type.
-<li>Builtin functions would be known to not have side effects, simplifying
- analysis over straight method calls.
-<li>The syntax of the builtin are cleaner than the syntax of the
- '<a href="#i_call"><tt>call</tt></a>' instruction (very minor point).
-</ul>
+<h5>Arguments:</h5>
-Because these invocations are explicit in the representation, the runtime can choose to implement these builtin functions any way that they want, including:
+This instruction takes a <tt>valist</tt> value and the type of the argument. It
+returns a value of the specified argument type.
-<ul>
-<li>Inlining the code directly into the invocation
-<li>Implementing the functions in some sort of Runtime class, convert invocation
- to a standard method call.
-<li>Implementing the functions in some sort of Runtime class, and perform
- standard inlining optimizations on it.
-</ul>
+<h5>Semantics:</h5>
-Note that these builtins do not use quoted identifiers: the name of the builtin effectively becomes an identifier in the language.<p>
+The '<tt>vaarg</tt>' instruction loads an argument of the specified type from
+the specified <tt>va_list</tt>. In conjunction with the <a
+href="#i_vanext"><tt>vanext</tt></a> instruction, it is used to implement the
+<tt>va_arg</tt> macro available in C. For more information, see the variable
+argument handling <a href="#int_varargs">Intrinsic Functions</a>.<p>
-Example:
-<pre>
- ; Example of a normal method call
- %maximum = call int %maximum(int %arg1, int %arg2) <i>; yields {int}:%maximum</i>
+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>
- ; Examples of potential builtin functions
- %max = max(int %arg1, int %arg2) <i>; yields {int}:%max</i>
- %min = min(int %arg1, int %arg2) <i>; yields {int}:%min</i>
- %sin = sin(double %arg) <i>; yields {double}:%sin</i>
- %cos = cos(double %arg) <i>; yields {double}:%cos</i>
+<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>
- ; Show that builtin's are polymorphic, like instructions
- %max = max(float %arg1, float %arg2) <i>; yields {float}:%max</i>
- %cos = cos(float %arg) <i>; yields {float}:%cos</i>
-</pre>
+<h5>Example:</h5>
+
+See the <a href="#int_varargs">variable argument processing</a> section.<p>
-The '<tt>maximum</tt>' vs '<tt>max</tt>' example illustrates the difference in calling semantics between a '<a href="#i_call"><tt>call</tt></a>' instruction and a builtin function invocation. Notice that the '<tt>maximum</tt>' example assumes that the method is defined local to the caller.<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="todo">TODO List
+</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>
<!-- *********************************************************************** -->
-This list of random topics includes things that will <b>need</b> to be addressed before the llvm may be used to implement a java like langauge. Right now, it is pretty much useless for any language, given to unavailable of structure types<p>
+LLVM supports the notion of an "intrinsic function". These functions have well
+known names and semantics, and are required to follow certain restrictions.
+Overall, these instructions represent an extension mechanism for the LLVM
+language that does not require changing all of the transformations in LLVM to
+add to the language (or the bytecode reader/writer, the parser, etc...).<p>
-<!-- _______________________________________________________________________ -->
-</ul><a name="synchronization"><h3><hr size=0>Synchronization Instructions</h3><ul>
+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>
-We will need some type of synchronization instructions to be able to implement stuff in Java well. The way I currently envision doing this is to introduce a '<tt>lock</tt>' type, and then add two (builtin or instructions) operations to lock and unlock the lock.<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="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
-<a name="extensions">Possible Extensions
+<!-- ======================================================================= -->
+</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>
-<!-- *********************************************************************** -->
-These extensions are distinct from the TODO list, as they are mostly "interesting" ideas that could be implemented in the future by someone so motivated. They are not directly required to get <a href="#rw_java">Java</a> like languages working.<p>
+Variable argument support is defined in LLVM with the <a
+href="#i_vanext"><tt>vanext</tt></a> instruction and these three intrinsic
+functions. These functions are related to the similarly named macros defined in
+the <tt><stdarg.h></tt> header file.<p>
-<!-- _______________________________________________________________________ -->
-</ul><a name="i_tailcall"><h3><hr size=0>'<tt>tailcall</tt>' Instruction</h3><ul>
+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 could be useful. Who knows. '.net' does it, but is the optimization really worth the extra hassle? Using strong typing would make this trivial to implement and a runtime could always callback to using downconverting this to a normal '<a href="#i_call"><tt>call</tt></a>' instruction.<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>()
-<!-- _______________________________________________________________________ -->
-</ul><a name="globalvars"><h3><hr size=0>Global Variables</h3><ul>
+ ; Read a single integer argument
+ %tmp = vaarg sbyte* %ap, int
-In order to represent programs written in languages like C, we need to be able to support variables at the module (global) scope. Perhaps they should be written outside of the module definition even. Maybe global functions should be handled like this as well.<p>
+ ; 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="
explicitparrellelism"><h3><hr size=0>Explicit Parrellelism</h3><ul>
+</ul><a name="
i_va_start"><h4><hr size=0>'<tt>llvm.va_start</tt>' Intrinsic</h4><ul>
-With the rise of massively parrellel architectures (like <a href="#rw_ia64">the IA64 architecture</a>, multithreaded CPU cores, and SIMD data sets) it is becoming increasingly more important to extract all of the ILP from a code stream possible. It would be interesting to research encoding methods that can explicitly represent this. One straightforward way to do this would be to introduce a "stop" instruction that is equilivent to the IA64 stop bit.<p>
+<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>
-<!-- *********************************************************************** -->
-</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="related">Related Work
-</b></font></td></tr></table><ul>
-<!-- *********************************************************************** -->
+<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>
-Codesigned virtual machines.<p>
+Note that this intrinsic function is only legal to be called from within the
+body of a variable argument function.<p>
-<dl>
-<a name="rw_safetsa">
-<dt>SafeTSA
-<DD>Description here<p>
-<a name="rw_java">
-<dt><a href="http://www.javasoft.com">Java</a>
-<DD>Desciption here<p>
+<!-- _______________________________________________________________________ -->
+</ul><a name="i_va_end"><h4><hr size=0>'<tt>llvm.va_end</tt>' Intrinsic</h4><ul>
-<a name="rw_net">
-<dt><a href="http://www.microsoft.com/net">Microsoft .net</a>
-<DD>Desciption here<p>
+<h5>Syntax:</h5>
+<pre>
+ call void (va_list)* %llvm.va_end(va_list <arglist>)
+</pre>
-<a name="rw_gccrtl">
-<dt><a href="http://www.math.umn.edu/systems_guide/gcc-2.95.1/gcc_15.html">GNU RTL Intermediate Representation</a>
-<DD>Desciption here<p>
+<h5>Overview:</h5>
-<a name="rw_ia64">
-<dt><a href="http://developer.intel.com/design/ia-64/index.htm">IA64 Architecture & Instruction Set</a>
-<DD>Desciption here<p>
+The '<tt>llvm.va_end</tt>' intrinsic destroys <tt><arglist></tt> which has
+been initialized previously with <tt><a
+href="#i_va_start">llvm.va_start</a></tt> or <tt><a
+href="#i_va_copy">llvm.va_copy</a></tt>.<p>
+
+<h5>Arguments:</h5>
+
+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>
-<a name="rw_mmix">
-<dt><a href="http://www-cs-faculty.stanford.edu/~knuth/mmix-news.html">MMIX Instruction Set</a>
-<DD>Desciption here<p>
-<a name="rw_stroustrup">
-<dt><a href="http://www.research.att.com/~bs/devXinterview.html">"Interview With Bjarne Stroustrup"</a>
-<DD>This interview influenced the design and thought process behind LLVM in several ways, most notably the way that derived types are written in text format. See the question that starts with "you defined the C declarator syntax as an experiment that failed".<p>
-</dl>
<!-- _______________________________________________________________________ -->
-</ul><a name="
rw_vectorization"><h3><hr size=0>Vectorized Architectures</h3><ul>
+</ul><a name="
i_va_copy"><h4><hr size=0>'<tt>llvm.va_copy</tt>' Intrinsic</h4><ul>
-<dl>
-<a name="rw_intel_simd">
-<dt>Intel MMX, MMX2, SSE, SSE2
-<DD>Description here<p>
+<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>
-<a name="rw_amd_simd">
-<dt><a href="http://www.nondot.org/~sabre/os/H1ChipFeatures/3DNow!TechnologyManual.pdf">AMD 3Dnow!, 3Dnow! 2</a>
-<DD>Desciption here<p>
+<h5>Arguments:</h5>
-<a name="rw_sun_simd">
-<dt><a href="http://www.nondot.org/~sabre/os/H1ChipFeatures/VISInstructionSetUsersManual.pdf">Sun VIS ISA</a>
-<DD>Desciption here<p>
+The argument is the <tt>va_list</tt> to copy.
+<h5>Semantics:</h5>
-</dl>
+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>
-more...
<!-- *********************************************************************** -->
</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: Sun Jul 8 19:25:56 CDT 2001
+Last modified: Wed Oct 29 19:30:46 CST 2003
<!-- hhmts end -->
</font>
</body></html>
projects / oota-llvm.git / blobdiff