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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 - suboptimal codegen for conditional float return?"
href="https://bugs.llvm.org/show_bug.cgi?id=39534">39534</a>
</td>
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<tr>
<th>Summary</th>
<td>suboptimal codegen for conditional float return?
</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>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>trass3r@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
</td>
</tr></table>
<p>
<div>
<pre>bool isNanOrInf(float x)
{
return (reinterpret_cast<unsigned&>(x) & 0x7F800000) == 0x7F800000;
}
float test(float x)
{
return isNanOrInf(x) ? 0 : x;
}
test(float):
vmovd eax, xmm0
not eax
vpxor xmm1, xmm1, xmm1
and eax, 2139095040
je .LBB1_2
vmovdqa xmm1, xmm0
.LBB1_2:
vmovdqa xmm0, xmm1
ret
In contrast gcc does not use xmm1 at all:
test(float):
vmovd eax, xmm0
mov edx, 2139095040
and edx, eax
cmp edx, 2139095040
je .L5
ret
.L5:
vxorps xmm0, xmm0, xmm0
ret
<a href="https://gcc.godbolt.org/z/biNBFq">https://gcc.godbolt.org/z/biNBFq</a></pre>
</div>
</p>
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