<li><a href="#metadata">Metadata Nodes and Metadata Strings</a>
<ol>
<li><a href="#tbaa">'<tt>tbaa</tt>' Metadata</a></li>
- <li><a href="#fpaccuracy">'<tt>fpaccuracy</tt>' Metadata</a></li>
+ <li><a href="#fpmath">'<tt>fpmath</tt>' Metadata</a></li>
+ <li><a href="#range">'<tt>range</tt>' Metadata</a></li>
</ol>
</li>
</ol>
<div>
-<p>LLVM programs are composed of "Module"s, each of which is a translation unit
- of the input programs. Each module consists of functions, global variables,
- and symbol table entries. Modules may be combined together with the LLVM
- linker, which merges function (and global variable) definitions, resolves
- forward declarations, and merges symbol table entries. Here is an example of
- the "hello world" module:</p>
+<p>LLVM programs are composed of <tt>Module</tt>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 class="doc_code">
<i>; Declare the string constant as a global constant.</i>
-<a href="#identifiers">@.LC0</a> = <a href="#linkage_internal">internal</a> <a href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" <i>; [13 x i8]*</i>
+<a href="#identifiers">@.str</a> = <a href="#linkage_private">private</a> <a href="#globalvars">unnamed_addr</a> <a href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00"
<i>; External declaration of the puts function</i>
-<a href="#functionstructure">declare</a> i32 @puts(i8*) <i>; i32 (i8*)* </i>
+<a href="#functionstructure">declare</a> i32 @puts(i8* <a href="#nocapture">nocapture</a>) <a href="#fnattrs">nounwind</a>
<i>; Definition of main function</i>
define i32 @main() { <i>; i32()* </i>
<i>; Convert [13 x i8]* to i8 *...</i>
- %cast210 = <a href="#i_getelementptr">getelementptr</a> [13 x i8]* @.LC0, i64 0, i64 0 <i>; i8*</i>
+ %cast210 = <a href="#i_getelementptr">getelementptr</a> [13 x i8]* @.str, i64 0, i64 0
<i>; Call puts function to write out the string to stdout.</i>
- <a href="#i_call">call</a> i32 @puts(i8* %cast210) <i>; i32</i>
+ <a href="#i_call">call</a> i32 @puts(i8* %cast210)
<a href="#i_ret">ret</a> i32 0
}
<i>; Named metadata</i>
-!1 = metadata !{i32 41}
+!1 = metadata !{i32 42}
!foo = !{!1, null}
</pre>
<p>This example is made up of a <a href="#globalvars">global variable</a> named
- "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>" function,
+ "<tt>.str</tt>", an external declaration of the "<tt>puts</tt>" function,
a <a href="#functionstructure">function definition</a> for
"<tt>main</tt>" and <a href="#namedmetadatastructure">named metadata</a>
- "<tt>foo"</tt>.</p>
+ "<tt>foo</tt>".</p>
-<p>In general, a module is made up of a list of global values, where both
- functions and global variables are global values. Global values are
+<p>In general, a module is made up of a list of global values (where both
+ functions and global variables are global values). Global values are
represented by a pointer to a memory location (in this case, a pointer to an
array of char, and a pointer to a function), and have one of the
following <a href="#linkage">linkage types</a>.</p>
<!-- _______________________________________________________________________ -->
<h4>
- <a name="fpaccuracy">'<tt>fpaccuracy</tt>' Metadata</a>
+ <a name="fpmath">'<tt>fpmath</tt>' Metadata</a>
</h4>
<div>
-<p><tt>fpaccuracy</tt> metadata may be attached to any instruction of floating
- point type. It expresses the maximum relative error of the result of
- that instruction, in ULPs. ULP is defined as follows:</p>
+<p><tt>fpmath</tt> metadata may be attached to any instruction of floating point
+ type. It can be used to express the maximum acceptable relative error in the
+ result of that instruction, in ULPs, thus potentially allowing the compiler
+ to use a more efficient but less accurate method of computing it.
+ ULP is defined as follows:</p>
<blockquote>
</blockquote>
-<p>The maximum relative error may be any rational number. The metadata node
- shall consist of a pair of unsigned integers respectively representing
- the numerator and denominator. For example, 2.5 ULP:</p>
+<p>The metadata node shall consist of a single non-negative floating
+ point number representing the maximum relative error. For example,
+ 2.5 ULP:</p>
<div class="doc_code">
<pre>
-!0 = metadata !{ i32 5, i32 2 }
+!0 = metadata !{ float 2.5 }
</pre>
</div>
</div>
+<!-- _______________________________________________________________________ -->
+<h4>
+ <a name="range">'<tt>range</tt>' Metadata</a>
+</h4>
+
+<div>
+<p><tt>range</tt> metadata may be attached only to loads of integer types. It
+ expresses the possible ranges the loaded value is in. The ranges are
+ represented with a flattened list of integers. The loaded value is known to
+ be in the union of the ranges defined by each consecutive pair. Each pair
+ has the following properties:</p>
+<ul>
+ <li>The type must match the type loaded by the instruction.</li>
+ <li>The pair <tt>a,b</tt> represents the range <tt>[a,b)</tt>.</li>
+ <li>Both <tt>a</tt> and <tt>b</tt> are constants.</li>
+ <li>The range is allowed to wrap.</li>
+ <li>The range should not represent the full or empty set. That is,
+ <tt>a!=b</tt>. </li>
+</ul>
+
+<p>Examples:</p>
+<div class="doc_code">
+<pre>
+ %a = load i8* %x, align 1, !range !0 ; Can only be 0 or 1
+ %b = load i8* %y, align 1, !range !1 ; Can only be 255 (-1), 0 or 1
+ %c = load i8* %z, align 1, !range !2 ; Can only be 0, 1, 3, 4 or 5
+...
+!0 = metadata !{ i8 0, i8 2 }
+!1 = metadata !{ i8 255, i8 2 }
+!2 = metadata !{ i8 0, i8 2, i8 3, i8 6 }
+</pre>
+</div>
+</div>
</div>
</div>
<tr>
<td>1</td>
<td align="left">
- <dt><b>Error</b></dt>
- <dd>Emits an error if two values disagree. It is an error to have an ID
- with both an Error and a Warning behavior.</dd>
+ <dl>
+ <dt><b>Error</b></dt>
+ <dd>Emits an error if two values disagree. It is an error to have an ID
+ with both an Error and a Warning behavior.</dd>
+ </dl>
</td>
</tr>
<tr>
<td>2</td>
<td align="left">
- <dt><b>Warning</b></dt>
- <dd>Emits a warning if two values disagree.</dd>
+ <dl>
+ <dt><b>Warning</b></dt>
+ <dd>Emits a warning if two values disagree.</dd>
+ </dl>
</td>
</tr>
<tr>
<td>3</td>
<td align="left">
- <dt><b>Require</b></dt>
- <dd>Emits an error when the specified value is not present or doesn't
- have the specified value. It is an error for two (or more)
- <tt>llvm.module.flags</tt> with the same ID to have the Require
- behavior but different values. There may be multiple Require flags
- per ID.</dd>
+ <dl>
+ <dt><b>Require</b></dt>
+ <dd>Emits an error when the specified value is not present or doesn't
+ have the specified value. It is an error for two (or more)
+ <tt>llvm.module.flags</tt> with the same ID to have the Require
+ behavior but different values. There may be multiple Require flags
+ per ID.</dd>
+ </dl>
</td>
</tr>
<tr>
<td>4</td>
<td align="left">
- <dt><b>Override</b></dt>
- <dd>Uses the specified value if the two values disagree. It is an error
- for two (or more) <tt>llvm.module.flags</tt> with the same ID to
- have the Override behavior but different values.</dd>
+ <dl>
+ <dt><b>Override</b></dt>
+ <dd>Uses the specified value if the two values disagree. It is an
+ error for two (or more) <tt>llvm.module.flags</tt> with the same
+ ID to have the Override behavior but different values.</dd>
+ </dl>
</td>
</tr>
</tbody>
following key-value pairs:</p>
<table border="1" cellspacing="0" cellpadding="4">
+ <col width="30%">
<tbody>
<tr>
- <th width="30%">Key</th>
+ <th>Key</th>
<th>Value</th>
</tr>
<tr>
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_resume">resume</a></tt> instructions), the memory is
- reclaimed. Allocating zero bytes is legal, but the result is undefined.</p>
+ reclaimed. Allocating zero bytes is legal, but the result is undefined.
+ The order in which memory is allocated (ie., which way the stack grows) is
+ not specified.</p>
+
+<p>
<h5>Example:</h5>
<pre>
projects / oota-llvm.git / blobdiff