</li>
<li><a href="#t_derived">Derived Types</a>
<ol>
- <li><a href="#t_array">Array Type</a></li>
+ <li><a href="#t_aggregate">Aggregate Types</a>
+ <ol>
+ <li><a href="#t_array">Array Type</a></li>
+ <li><a href="#t_struct">Structure Type</a></li>
+ <li><a href="#t_pstruct">Packed Structure Type</a></li>
+ <li><a href="#t_union">Union Type</a></li>
+ <li><a href="#t_vector">Vector Type</a></li>
+ </ol>
+ </li>
<li><a href="#t_function">Function Type</a></li>
<li><a href="#t_pointer">Pointer Type</a></li>
- <li><a href="#t_struct">Structure Type</a></li>
- <li><a href="#t_pstruct">Packed Structure Type</a></li>
- <li><a href="#t_vector">Vector Type</a></li>
<li><a href="#t_opaque">Opaque Type</a></li>
</ol>
</li>
<div class="doc_text">
-<p>Named metadata is a collection of metadata. <a href="#metadata"> Metadata </a>
- node and null are the only valid named metadata operands.
- Metadata strings are not allowed as an named metadata operand.</p>
+<p>Named metadata is a collection of metadata. <a href="#metadata">Metadata
+ nodes</a> (but not metadata strings) and null are the only valid operands for
+ a named metadata.</p>
<h5>Syntax:</h5>
<div class="doc_code">
</div>
<dl>
+ <dt><tt><b>alignstack(<<em>n</em>>)</b></tt></dt>
+ <dd>This attribute indicates that, when emitting the prologue and epilogue,
+ the backend should forcibly align the stack pointer. Specify the
+ desired alignment, which must be a power of two, in parentheses.
+
<dt><tt><b>alwaysinline</b></tt></dt>
<dd>This attribute indicates that the inliner should attempt to inline this
function into callers whenever possible, ignoring any active inlining size
<ul>
<li><tt>E</tt> - big endian</li>
- <li><tt>p:32:64:64</tt> - 32-bit pointers with 64-bit alignment</li>
+ <li><tt>p:64:64:64</tt> - 64-bit pointers with 64-bit alignment</li>
<li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li>
<li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li>
<li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li>
<a href="#t_pointer">pointer</a>,
<a href="#t_vector">vector</a>,
<a href="#t_struct">structure</a>,
+ <a href="#t_union">union</a>,
<a href="#t_array">array</a>,
<a href="#t_label">label</a>,
<a href="#t_metadata">metadata</a>.
</tr>
<tr>
<td><a href="#t_derived">derived</a></td>
- <td><a href="#t_integer">integer</a>,
- <a href="#t_array">array</a>,
+ <td><a href="#t_array">array</a>,
<a href="#t_function">function</a>,
<a href="#t_pointer">pointer</a>,
<a href="#t_struct">structure</a>,
<a href="#t_pstruct">packed structure</a>,
+ <a href="#t_union">union</a>,
<a href="#t_vector">vector</a>,
<a href="#t_opaque">opaque</a>.
</td>
possible to have a two dimensional array, using an array as the element type
of another array.</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsubsection"> <a name="t_aggregate">Aggregate Types</a> </div>
+
+<div class="doc_text">
+
+<p>Aggregate Types are a subset of derived types that can contain multiple
+ member types. <a href="#t_array">Arrays</a>,
+ <a href="#t_struct">structs</a>, <a href="#t_vector">vectors</a> and
+ <a href="#t_union">unions</a> are aggregate types.</p>
+
+</div>
+
</div>
<!-- _______________________________________________________________________ -->
<h5>Overview:</h5>
<p>The function type can be thought of as a function signature. It consists of
a return type and a list of formal parameter types. The return type of a
- function type is a scalar type, a void type, or a struct type. If the return
- type is a struct type then all struct elements must be of first class types,
- and the struct must have at least one element.</p>
+ function type is a scalar type, a void type, a struct type, or a union
+ type. If the return type is a struct type then all struct elements must be
+ of first class types, and the struct must have at least one element.</p>
<h5>Syntax:</h5>
<pre>
</div>
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsubsection"> <a name="t_union">Union Type</a> </div>
+
+<div class="doc_text">
+
+<h5>Overview:</h5>
+<p>A union type describes an object with size and alignment suitable for
+ an object of any one of a given set of types (also known as an "untagged"
+ union). It is similar in concept and usage to a
+ <a href="#t_struct">struct</a>, except that all members of the union
+ have an offset of zero. The elements of a union may be any type that has a
+ size. Unions must have at least one member - empty unions are not allowed.
+ </p>
+
+<p>The size of the union as a whole will be the size of its largest member,
+ and the alignment requirements of the union as a whole will be the largest
+ alignment requirement of any member.</p>
+
+<p>Union members 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.
+ Since all members are at offset zero, the getelementptr instruction does
+ not affect the address, only the type of the resulting pointer.</p>
+
+<h5>Syntax:</h5>
+<pre>
+ union { <type list> }
+</pre>
+
+<h5>Examples:</h5>
+<table class="layout">
+ <tr class="layout">
+ <td class="left"><tt>union { i32, i32*, float }</tt></td>
+ <td class="left">A union of three types: an <tt>i32</tt>, a pointer to
+ an <tt>i32</tt>, and a <tt>float</tt>.</td>
+ </tr><tr class="layout">
+ <td class="left">
+ <tt>union { float, i32 (i32) * }</tt></td>
+ <td class="left">A union, where the first element is a <tt>float</tt> and the
+ second element is a <a href="#t_pointer">pointer</a> to a
+ <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
+ an <tt>i32</tt>.</td>
+ </tr>
+</table>
+
+</div>
+
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div>
<div class="doc_text">
<h5>Overview:</h5>
-<p>As in many languages, the pointer type represents a pointer or reference to
- another object, which must live in memory. Pointer types may have an optional
- address space attribute defining the target-specific numbered address space
- where the pointed-to object resides. The default address space is zero.</p>
+<p>The pointer type is used to specify memory locations.
+ Pointers are commonly used to reference objects in memory.</p>
+
+<p>Pointer types may have an optional address space attribute defining the
+ numbered address space where the pointed-to object resides. The default
+ address space is number zero. The semantics of non-zero address
+ spaces are target-specific.</p>
<p>Note that LLVM does not permit pointers to void (<tt>void*</tt>) nor does it
permit pointers to labels (<tt>label*</tt>). Use <tt>i8*</tt> instead.</p>
the number and types of elements must match those specified by the
type.</dd>
+ <dt><b>Union constants</b></dt>
+ <dd>Union constants are represented with notation similar to a structure with
+ a single element - that is, a single typed element surrounded
+ by braces (<tt>{}</tt>)). For example: "<tt>{ i32 4 }</tt>". The
+ <a href="#t_union">union type</a> can be initialized with a single-element
+ struct as long as the type of the struct element matches the type of
+ one of the union members.</dd>
+
<dt><b>Array constants</b></dt>
<dd>Array constants are represented with notation similar to array type
definitions (a comma separated list of elements, surrounded by square
<dt><b>Zero initialization</b></dt>
<dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a
- value to zero of <em>any</em> type, including scalar and aggregate types.
+ value to zero of <em>any</em> type, including scalar and
+ <a href="#t_aggregate">aggregate</a> types.
This is often used to avoid having to print large zero initializers
(e.g. for large arrays) and is always exactly equivalent to using explicit
zero initializers.</dd>
</div>
-<!-- ======================================================================= -->
-<div class="doc_subsection"><a name="metadata">Metadata Nodes and Metadata Strings</a>
-</div>
-
-<div class="doc_text">
-
-<p>Metadata provides a way to attach arbitrary data to the instruction
- stream without affecting the behaviour of the program. There are two
- metadata primitives, strings and nodes. All metadata has the
- <tt>metadata</tt> type and is identified in syntax by a preceding exclamation
- point ('<tt>!</tt>').</p>
-
-<p>A metadata string is a string surrounded by double quotes. It can contain
- any character by escaping non-printable characters with "\xx" where "xx" is
- the two digit hex code. For example: "<tt>!"test\00"</tt>".</p>
-
-<p>Metadata nodes are represented with notation similar to structure constants
- (a comma separated list of elements, surrounded by braces and preceded by an
- exclamation point). For example: "<tt>!{ metadata !"test\00", i32
- 10}</tt>".</p>
-
-<p>A metadata node will attempt to track changes to the values it holds. In the
- event that a value is deleted, it will be replaced with a typeless
- "<tt>null</tt>", such as "<tt>metadata !{null, i32 10}</tt>".</p>
-
-<p>A <a href="#namedmetadatastructure">named metadata</a> is a collection of
- metadata nodes. For example: "<tt>!foo = metadata !{!4, !3}</tt>".
-
-<p>Optimizations may rely on metadata to provide additional information about
- the program that isn't available in the instructions, or that isn't easily
- computable. Similarly, the code generator may expect a certain metadata
- format to be used to express debugging information.</p>
-
-</div>
-
<!-- *********************************************************************** -->
<div class="doc_section"> <a name="othervalues">Other Values</a> </div>
<!-- *********************************************************************** -->
</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="metadata">Metadata Nodes and Metadata
+ Strings</a>
+</div>
+
+<div class="doc_text">
+
+<p>LLVM IR allows metadata to be attached to instructions in the program that
+ can convey extra information about the code to the optimizers and code
+ generator. One example application of metadata is source-level debug
+ information. There are two metadata primitives: strings and nodes. All
+ metadata has the <tt>metadata</tt> type and is identified in syntax by a
+ preceding exclamation point ('<tt>!</tt>').</p>
+
+<p>A metadata string is a string surrounded by double quotes. It can contain
+ any character by escaping non-printable characters with "\xx" where "xx" is
+ the two digit hex code. For example: "<tt>!"test\00"</tt>".</p>
+
+<p>Metadata nodes are represented with notation similar to structure constants
+ (a comma separated list of elements, surrounded by braces and preceded by an
+ exclamation point). For example: "<tt>!{ metadata !"test\00", i32
+ 10}</tt>". Metadata nodes can have any values as their operand.</p>
+
+<p>A <a href="#namedmetadatastructure">named metadata</a> is a collection of
+ metadata nodes, which can be looked up in the module symbol table. For
+ example: "<tt>!foo = metadata !{!4, !3}</tt>".
+
+</div>
+
<!-- *********************************************************************** -->
<div class="doc_section">
block to the "normal" label. If the callee unwinds then no return value is
available.</p>
+<p>Note that the code generator does not yet completely support unwind, and
+that the invoke/unwind semantics are likely to change in future versions.</p>
+
<h5>Example:</h5>
<pre>
%retval = invoke i32 @Test(i32 15) to label %Continue
specified by the <tt>invoke</tt> instruction. If there is no <tt>invoke</tt>
instruction in the dynamic call chain, undefined behavior results.</p>
+<p>Note that the code generator does not yet completely support unwind, and
+that the invoke/unwind semantics are likely to change in future versions.</p>
+
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_text">
-<p>LLVM supports several instructions for working with aggregate values.</p>
+<p>LLVM supports several instructions for working with
+ <a href="#t_aggregate">aggregate</a> values.</p>
</div>
</pre>
<h5>Overview:</h5>
-<p>The '<tt>extractvalue</tt>' instruction extracts the value of a struct field
- or array element from an aggregate value.</p>
+<p>The '<tt>extractvalue</tt>' instruction extracts the value of a member field
+ from an <a href="#t_aggregate">aggregate</a> value.</p>
<h5>Arguments:</h5>
<p>The first operand of an '<tt>extractvalue</tt>' instruction is a value
- of <a href="#t_struct">struct</a> or <a href="#t_array">array</a> type. The
- operands are constant indices to specify which value to extract in a similar
- manner as indices in a
+ of <a href="#t_struct">struct</a>, <a href="#t_union">union</a> or
+ <a href="#t_array">array</a> type. The operands are constant indices to
+ specify which value to extract in a similar manner as indices in a
'<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.</p>
<h5>Semantics:</h5>
</pre>
<h5>Overview:</h5>
-<p>The '<tt>insertvalue</tt>' instruction inserts a value into a struct field or
- array element in an aggregate.</p>
-
+<p>The '<tt>insertvalue</tt>' instruction inserts a value into a member field
+ in an <a href="#t_aggregate">aggregate</a> value.</p>
<h5>Arguments:</h5>
<p>The first operand of an '<tt>insertvalue</tt>' instruction is a value
- of <a href="#t_struct">struct</a> or <a href="#t_array">array</a> type. The
- second operand is a first-class value to insert. The following operands are
- constant indices indicating the position at which to insert the value in a
- similar manner as indices in a
+ of <a href="#t_struct">struct</a>, <a href="#t_union">union</a> or
+ <a href="#t_array">array</a> type. The second operand is a first-class
+ value to insert. The following operands are constant indices indicating
+ the position at which to insert the value in a similar manner as indices in a
'<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction. The
value to insert must have the same type as the value identified by the
indices.</p>
<h5>Syntax:</h5>
<pre>
- <result> = load <ty>* <pointer>[, align <alignment>]
- <result> = volatile load <ty>* <pointer>[, align <alignment>]
+ <result> = load <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>]
+ <result> = volatile load <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>]
+ !<index> = !{ i32 1 }
</pre>
<h5>Overview:</h5>
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>
+ instructions.</p>
-<p>The optional constant "align" argument specifies the alignment of the
+<p>The optional constant <tt>align</tt> argument specifies the alignment of the
operation (that is, the alignment of the memory address). A value of 0 or an
- omitted "align" argument means that the operation has the preferential
+ omitted <tt>align</tt> argument means that the operation has the preferential
alignment for the target. It is the responsibility of the code emitter to
ensure that the alignment information is correct. Overestimating the
- alignment results in an undefined behavior. Underestimating the alignment may
+ alignment results in undefined behavior. Underestimating the alignment may
produce less efficient code. An alignment of 1 is always safe.</p>
+<p>The optional <tt>!nontemporal</tt> metadata must reference a single
+ metatadata name <index> corresponding to a metadata node with
+ one <tt>i32</tt> entry of value 1. The existance of
+ the <tt>!nontemporal</tt> metatadata on the instruction tells the optimizer
+ and code generator that this load is not expected to be reused in the cache.
+ The code generator may select special instructions to save cache bandwidth,
+ such as the <tt>MOVNT</tt> intruction on x86.</p>
+
<h5>Semantics:</h5>
<p>The location of memory pointed to is loaded. If the value being loaded is of
scalar type then the number of bytes read does not exceed the minimum number
<h5>Syntax:</h5>
<pre>
- store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
- volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
+ store <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
+ volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
</pre>
<h5>Overview:</h5>
alignment results in an undefined behavior. Underestimating the alignment may
produce less efficient code. An alignment of 1 is always safe.</p>
+<p>The optional !nontemporal metadata must reference a single metatadata
+ name <index> corresponding to a metadata node with one i32 entry of
+ value 1. The existance of the !nontemporal metatadata on the
+ instruction tells the optimizer and code generator that this load is
+ not expected to be reused in the cache. The code generator may
+ select special instructions to save cache bandwidth, such as the
+ MOVNT intruction on x86.</p>
+
+
<h5>Semantics:</h5>
<p>The contents of memory are updated to contain '<tt><value></tt>' at the
location specified by the '<tt><pointer></tt>' operand. If
<h5>Overview:</h5>
<p>The '<tt>getelementptr</tt>' instruction is used to get the address of a
- subelement of an aggregate data structure. It performs address calculation
- only and does not access memory.</p>
+ subelement of an <a href="#t_aggregate">aggregate</a> data structure.
+ It performs address calculation only and does not access memory.</p>
<h5>Arguments:</h5>
<p>The first argument is always a pointer, and forms the basis of the
indexes the pointer value given as the first argument, the second index
indexes a value of the type pointed to (not necessarily the value directly
pointed to, since the first index can be non-zero), etc. The first type
- indexed into must be a pointer value, subsequent types can be arrays, vectors
- and structs. Note that subsequent types being indexed into can never be
- pointers, since that would require loading the pointer before continuing
- calculation.</p>
+ indexed into must be a pointer value, subsequent types can be arrays,
+ vectors, structs and unions. Note that subsequent types being indexed into
+ can never be pointers, since that would require loading the pointer before
+ continuing calculation.</p>
<p>The type of each index argument depends on the type it is indexing into.
- When indexing into a (optionally packed) structure, only <tt>i32</tt> integer
- <b>constants</b> are allowed. When indexing into an array, pointer or
- vector, integers of any width are allowed, and they are not required to be
+ When indexing into a (optionally packed) structure or union, only <tt>i32</tt>
+ integer <b>constants</b> are allowed. When indexing into an array, pointer
+ or vector, integers of any width are allowed, and they are not required to be
constant.</p>
<p>For example, let's consider a C code fragment and how it gets compiled to
projects / oota-llvm.git / blobdiff