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Add a pinned metadata name for fpaccuracy, and document it

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143135 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne 2011-10-27 19:19:14 +00:00
parent 249d953ed7
commit 999f90bedf
3 changed files with 37 additions and 1 deletions
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30
docs/LangRef.html
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@ -103,6 +103,7 @@
<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>
</ol>
</li>
</ol>
@ -2966,6 +2967,35 @@ call void @llvm.dbg.value(metadata !24, i64 0, metadata !25)
</div>
<h4>
<a name="fpaccuracy">'<tt>fpaccuracy</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>
<blockquote><p>
If x is a real number that lies between two finite consecutive floating-point
numbers a and b, without being equal to one of them, then ulp(x) = |b - a|,
otherwise ulp(x) is the distance between the two non-equal finite
floating-point numbers nearest x. Moreover, ulp(NaN) is NaN.
</p></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>
<div class="doc_code">
<pre>
!0 = metadata !{ i32 5, i32 2 }
</pre>
</div>
</div>
</div>
</div>

3
include/llvm/LLVMContext.h
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@ -40,7 +40,8 @@ public:
enum {
MD_dbg = 0, // "dbg"
MD_tbaa = 1, // "tbaa"
MD_prof = 2 // "prof"
MD_prof = 2, // "prof"
MD_fpaccuracy = 3 // "fpaccuracy"
};
/// getMDKindID - Return a unique non-zero ID for the specified metadata kind.

5
lib/VMCore/LLVMContext.cpp
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@ -43,6 +43,11 @@ LLVMContext::LLVMContext() : pImpl(new LLVMContextImpl(*this)) {
// Create the 'prof' metadata kind.
unsigned ProfID = getMDKindID("prof");
assert(ProfID == MD_prof && "prof kind id drifted"); (void)ProfID;
// Create the 'fpaccuracy' metadata kind.
unsigned FPAccuracyID = getMDKindID("fpaccuracy");
assert(FPAccuracyID == MD_fpaccuracy && "fpaccuracy kind id drifted");
(void)FPAccuracyID;
}
LLVMContext::~LLVMContext() { delete pImpl; }