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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Optimize C++ spaceship comparison"
href="https://bugs.llvm.org/show_bug.cgi?id=49866">49866</a>
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</tr>
<tr>
<th>Summary</th>
<td>Optimize C++ spaceship comparison
</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>Linux
</td>
</tr>
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<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>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>marc.glisse@normalesup.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Similar to gcc's <a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94589">https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94589</a> , it would
be nice to optimize (x<=>y)@0 to x@y for all comparisons @, and clang/llvm
seems to manage for some but not all.
#include <compare>
int n(int x){return (x<=>0)<0;}
Debian clang version 13.0.0-++20210129063721+010b176cdefb-1~exp1
x86_64-pc-linux-gnu
movl %edi, %eax
shrl $24, %eax
testl %edi, %edi
setne %cl
testb %al, %al
sets %al
andb %cl, %al
movzbl %al, %eax
retq</pre>
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