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Update the LangRef documentation for llvm.ctlz and llvm.cttz to specify

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the behavior with the newly added flag for undefined results on a zero
input.

I'm terrible at documentation, so comments and suggestions welcome here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146361 91177308-0d34-0410-b5e6-96231b3b80d8
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Chandler Carruth 2011-12-12 04:36:04 +00:00
parent c4eab904c9
commit 48b0bbf930
1 changed files with 37 additions and 23 deletions
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@ -7335,12 +7335,12 @@ LLVM</a>.</p>
targets support all bit widths or vector types, however.</p> targets support all bit widths or vector types, however.</p>
<pre> <pre>
declare i8 @llvm.ctlz.i8 (i8 &lt;src&gt;) declare i8 @llvm.ctlz.i8 (i8 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declare i16 @llvm.ctlz.i16(i16 &lt;src&gt;) declare i16 @llvm.ctlz.i16 (i16 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declare i32 @llvm.ctlz.i32(i32 &lt;src&gt;) declare i32 @llvm.ctlz.i32 (i32 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declare i64 @llvm.ctlz.i64(i64 &lt;src&gt;) declare i64 @llvm.ctlz.i64 (i64 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declare i256 @llvm.ctlz.i256(i256 &lt;src&gt;) declare i256 @llvm.ctlz.i256(i256 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declare &lt;2 x i32&gt; @llvm.ctlz.v2i32(&lt;2 x i32&gt; &lt;src;gt) declase &lt;2 x i32&gt; @llvm.ctlz.v2i32(&lt;2 x i32&gt; &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
</pre> </pre>
<h5>Overview:</h5> <h5>Overview:</h5>
@ -7348,15 +7348,22 @@ LLVM</a>.</p>
leading zeros in a variable.</p> leading zeros in a variable.</p>
<h5>Arguments:</h5> <h5>Arguments:</h5>
<p>The only argument is the value to be counted. The argument may be of any <p>The first argument is the value to be counted. This argument may be of any
integer type, or any vector type with integer element type. integer type, or a vectory with integer element type. The return type
The return type must match the argument type.</p> must match the first argument type.</p>
<p>The second argument must be a constant and is a flag to indicate whether the
intrinsic should ensure that a zero as the first argument produces a defined
result. Historically some architectures did not provide a defined result for
zero values as efficiently, and many algorithms are now predicated on
avoiding zero-value inputs.</p>
<h5>Semantics:</h5> <h5>Semantics:</h5>
<p>The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant) <p>The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant)
zeros in a variable, or within each element of the vector if the operation zeros in a variable, or within each element of the vector.
is of vector type. If the src == 0 then the result is the size in bits of If <tt>src == 0</tt> then the result is the size in bits of the type of
the type of src. For example, <tt>llvm.ctlz(i32 2) = 30</tt>.</p> <tt>src</tt> if <tt>is_zero_undef == 0</tt> and <tt>undef</tt> otherwise.
For example, <tt>llvm.ctlz(i32 2) = 30</tt>.</p>
</div> </div>
@ -7373,12 +7380,12 @@ LLVM</a>.</p>
support all bit widths or vector types, however.</p> support all bit widths or vector types, however.</p>
<pre> <pre>
declare i8 @llvm.cttz.i8 (i8 &lt;src&gt;) declare i8 @llvm.cttz.i8 (i8 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declare i16 @llvm.cttz.i16(i16 &lt;src&gt;) declare i16 @llvm.cttz.i16 (i16 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declare i32 @llvm.cttz.i32(i32 &lt;src&gt;) declare i32 @llvm.cttz.i32 (i32 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declare i64 @llvm.cttz.i64(i64 &lt;src&gt;) declare i64 @llvm.cttz.i64 (i64 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declare i256 @llvm.cttz.i256(i256 &lt;src&gt;) declare i256 @llvm.cttz.i256(i256 &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
declase &lt;2 x i32&gt; @llvm.cttz.v2i32(&lt;2 x i32&gt; &lt;src&gt;) declase &lt;2 x i32&gt; @llvm.cttz.v2i32(&lt;2 x i32&gt; &lt;src&gt;, i1 &lt;is_zero_undef&gt;)
</pre> </pre>
<h5>Overview:</h5> <h5>Overview:</h5>
@ -7386,15 +7393,22 @@ LLVM</a>.</p>
trailing zeros.</p> trailing zeros.</p>
<h5>Arguments:</h5> <h5>Arguments:</h5>
<p>The only argument is the value to be counted. The argument may be of any <p>The first argument is the value to be counted. This argument may be of any
integer type, or a vectory with integer element type.. The return type integer type, or a vectory with integer element type. The return type
must match the argument type.</p> must match the first argument type.</p>
<p>The second argument must be a constant and is a flag to indicate whether the
intrinsic should ensure that a zero as the first argument produces a defined
result. Historically some architectures did not provide a defined result for
zero values as efficiently, and many algorithms are now predicated on
avoiding zero-value inputs.</p>
<h5>Semantics:</h5> <h5>Semantics:</h5>
<p>The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant) <p>The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant)
zeros in a variable, or within each element of a vector. zeros in a variable, or within each element of a vector.
If the src == 0 then the result is the size in bits of If <tt>src == 0</tt> then the result is the size in bits of the type of
the type of src. For example, <tt>llvm.cttz(2) = 1</tt>.</p> <tt>src</tt> if <tt>is_zero_undef == 0</tt> and <tt>undef</tt> otherwise.
For example, <tt>llvm.cttz(2) = 1</tt>.</p>
</div> </div>