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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Failure to simplify abs(select(-x,+x,cond)) -> abs(x)"
href="https://bugs.llvm.org/show_bug.cgi?id=39474">39474</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Failure to simplify abs(select(-x,+x,cond)) -> abs(x)
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Windows NT
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>filcab@gmail.com, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com, tilkax@gmail.com
</td>
</tr></table>
<p>
<div>
<pre><a href="https://godbolt.org/z/IiYvRv">https://godbolt.org/z/IiYvRv</a>
#include <algorithm>
int abs_s32(bool b, int x)
{
return std::abs(b ? -x : x);
}
float abs_f32(bool b, float x)
{
return std::abs(b ? -x : x);
}
_Z7abs_s32bi: # @_Z7abs_s32bi
movl %esi, %ecx
negl %ecx
testl %edi, %edi
cmovel %esi, %ecx
movl %ecx, %eax
negl %eax
cmovll %ecx, %eax
retq
_Z7abs_f32bf: # @_Z7abs_f32bf
testl %edi, %edi
je .LBB1_2
xorps .LCPI1_0(%rip), %xmm0
.LBB1_2:
andps .LCPI1_1(%rip), %xmm0
retq
gcc manages to optimize both:
_Z7abs_s32bi:
movl %esi, %eax
cltd
xorl %edx, %eax
subl %edx, %eax
ret
_Z7abs_f32bf:
andps .LC0(%rip), %xmm0
ret</pre>
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