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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - fold signbit(x) ? -x : x -> fneg x"
href="https://bugs.llvm.org/show_bug.cgi?id=45306">45306</a>
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<th>Summary</th>
<td>fold signbit(x) ? -x : x -> fneg x
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
</td>
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<th>Keywords</th>
<td>code-quality
</td>
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>nok.raven@gmail.com
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<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
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<pre>This is essentially the <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - copysign folding"
href="show_bug.cgi?id=44153">bug 44153</a> but copysign replaced with conditional fneg.
Probably blocked by <a class="bz_bug_link
bz_status_NEW "
title="NEW - fneg (xor X -2147483648) -> X fold is missing in IR"
href="show_bug.cgi?id=44622">bug 44622</a>.
float changesign_std2(float x) {
bool isneg = std::signbit(x);
return isneg ? -x : x;
}
define dso_local float @_Z15changesign_std2f(float %0) local_unnamed_addr #0 {
%2 = bitcast float %0 to i32
%3 = icmp slt i32 %2, 0
%4 = fneg float %0
%5 = select i1 %3, float %4, float %0
ret float %5
}</pre>
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