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Update the LangRef documentation for llvm.ctlz and llvm.cttz to specify
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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@ -7335,12 +7335,12 @@ LLVM</a>.</p>
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targets support all bit widths or vector types, however.</p>
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<pre>
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declare i8 @llvm.ctlz.i8 (i8 <src>)
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declare i16 @llvm.ctlz.i16(i16 <src>)
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declare i32 @llvm.ctlz.i32(i32 <src>)
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declare i64 @llvm.ctlz.i64(i64 <src>)
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declare i256 @llvm.ctlz.i256(i256 <src>)
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declare <2 x i32> @llvm.ctlz.v2i32(<2 x i32> <src;gt)
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declare i8 @llvm.ctlz.i8 (i8 <src>, i1 <is_zero_undef>)
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declare i16 @llvm.ctlz.i16 (i16 <src>, i1 <is_zero_undef>)
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declare i32 @llvm.ctlz.i32 (i32 <src>, i1 <is_zero_undef>)
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declare i64 @llvm.ctlz.i64 (i64 <src>, i1 <is_zero_undef>)
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declare i256 @llvm.ctlz.i256(i256 <src>, i1 <is_zero_undef>)
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declase <2 x i32> @llvm.ctlz.v2i32(<2 x i32> <src>, i1 <is_zero_undef>)
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</pre>
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<h5>Overview:</h5>
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@ -7348,15 +7348,22 @@ LLVM</a>.</p>
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leading zeros in a variable.</p>
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<h5>Arguments:</h5>
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<p>The only argument is the value to be counted. The argument may be of any
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integer type, or any vector type with integer element type.
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The return type must match the argument type.</p>
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<p>The first argument is the value to be counted. This argument may be of any
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integer type, or a vectory with integer element type. The return type
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must match the first argument type.</p>
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<p>The second argument must be a constant and is a flag to indicate whether the
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intrinsic should ensure that a zero as the first argument produces a defined
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result. Historically some architectures did not provide a defined result for
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zero values as efficiently, and many algorithms are now predicated on
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avoiding zero-value inputs.</p>
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<h5>Semantics:</h5>
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<p>The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant)
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zeros in a variable, or within each element of the vector if the operation
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is of vector type. If the src == 0 then the result is the size in bits of
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the type of src. For example, <tt>llvm.ctlz(i32 2) = 30</tt>.</p>
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zeros in a variable, or within each element of the vector.
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If <tt>src == 0</tt> then the result is the size in bits of the type of
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<tt>src</tt> if <tt>is_zero_undef == 0</tt> and <tt>undef</tt> otherwise.
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For example, <tt>llvm.ctlz(i32 2) = 30</tt>.</p>
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</div>
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@ -7373,12 +7380,12 @@ LLVM</a>.</p>
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support all bit widths or vector types, however.</p>
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<pre>
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declare i8 @llvm.cttz.i8 (i8 <src>)
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declare i16 @llvm.cttz.i16(i16 <src>)
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declare i32 @llvm.cttz.i32(i32 <src>)
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declare i64 @llvm.cttz.i64(i64 <src>)
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declare i256 @llvm.cttz.i256(i256 <src>)
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declase <2 x i32> @llvm.cttz.v2i32(<2 x i32> <src>)
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declare i8 @llvm.cttz.i8 (i8 <src>, i1 <is_zero_undef>)
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declare i16 @llvm.cttz.i16 (i16 <src>, i1 <is_zero_undef>)
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declare i32 @llvm.cttz.i32 (i32 <src>, i1 <is_zero_undef>)
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declare i64 @llvm.cttz.i64 (i64 <src>, i1 <is_zero_undef>)
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declare i256 @llvm.cttz.i256(i256 <src>, i1 <is_zero_undef>)
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declase <2 x i32> @llvm.cttz.v2i32(<2 x i32> <src>, i1 <is_zero_undef>)
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</pre>
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<h5>Overview:</h5>
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@ -7386,15 +7393,22 @@ LLVM</a>.</p>
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trailing zeros.</p>
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<h5>Arguments:</h5>
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<p>The only argument is the value to be counted. The argument may be of any
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integer type, or a vectory with integer element type.. The return type
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must match the argument type.</p>
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<p>The first argument is the value to be counted. This argument may be of any
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integer type, or a vectory with integer element type. The return type
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must match the first argument type.</p>
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<p>The second argument must be a constant and is a flag to indicate whether the
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intrinsic should ensure that a zero as the first argument produces a defined
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result. Historically some architectures did not provide a defined result for
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zero values as efficiently, and many algorithms are now predicated on
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avoiding zero-value inputs.</p>
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<h5>Semantics:</h5>
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<p>The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant)
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zeros in a variable, or within each element of a vector.
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If the src == 0 then the result is the size in bits of
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the type of src. For example, <tt>llvm.cttz(2) = 1</tt>.</p>
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If <tt>src == 0</tt> then the result is the size in bits of the type of
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<tt>src</tt> if <tt>is_zero_undef == 0</tt> and <tt>undef</tt> otherwise.
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For example, <tt>llvm.cttz(2) = 1</tt>.</p>
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</div>
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