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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Use xorl instead of xorq when possible"
href="https://bugs.llvm.org/show_bug.cgi?id=50537">50537</a>
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<th>Summary</th>
<td>Use xorl instead of xorq when possible
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>12.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</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>
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<th>Component</th>
<td>new bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>josephcsible@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>Consider this C code:
unsigned long f(unsigned long x) {
return ((x & 1) + (x >> 1)) * (((x & 1) ^ 1) + x);
}
With -Oz, Clang produces this:
f: # @f
movl %edi, %eax
andl $1, %eax
movq %rdi, %rcx
shrq %rcx
addq %rax, %rcx
xorq $1, %rax
addq %rdi, %rax
imulq %rcx, %rax
retq
<a href="https://godbolt.org/z/Kqsa58Kn9">https://godbolt.org/z/Kqsa58Kn9</a>
It should do "xorl $1, %eax" instead of "xorq $1, %rax" there, as they
both have the same effect since rax will always be either 0 or 1 there, and the
latter requires an extra 1-byte REX prefix.</pre>
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</p>
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