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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DAGCombine] Failure to recognise alternative ISD::ABS pattern"
href="https://bugs.llvm.org/show_bug.cgi?id=36036">36036</a>
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<th>Summary</th>
<td>[DAGCombine] Failure to recognise alternative ISD::ABS pattern
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Common Code Generator Code
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
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</tr></table>
<p>
<div>
<pre>__v4si abs(__v4si v) {
__m128i sign = _mm_srai_epi32( v, 31 );
return _mm_xor_si128( _mm_add_epi32( v, sign ), sign );
}
__v4si abs_alt(__v4si v) {
__m128i sign = _mm_srai_epi32( v, 31 );
return _mm_sub_epi32( _mm_xor_si128( v, sign ), sign );
}
define <4 x i32> @abs(<4 x i32>) {
%2 = icmp slt <4 x i32> %0, zeroinitializer
%3 = sub <4 x i32> zeroinitializer, %0
%4 = select <4 x i1> %2, <4 x i32> %3, <4 x i32> %0
ret <4 x i32> %4
}
define <4 x i32> @abs_alt(<4 x i32>) {
%2 = ashr <4 x i32> %0, <i32 31, i32 31, i32 31, i32 31>
%3 = xor <4 x i32> %2, %0
%4 = sub <4 x i32> %3, %2
ret <4 x i32> %4
}
llc -mcpu=btver2
abs:
vpabsd %xmm0, %xmm0
retq
abs_alt:
vpsrad $31, %xmm0, %xmm1
vpxor %xmm0, %xmm1, %xmm0
vpsubd %xmm1, %xmm0, %xmm0
retq</pre>
</div>
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