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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 - Failure to optimize out useless zero-ing after register was already zero-ed"
href="https://bugs.llvm.org/show_bug.cgi?id=45723">45723</a>
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<th>Summary</th>
<td>Failure to optimize out useless zero-ing after register was already zero-ed
</td>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>gabravier@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
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<p>
<div>
<pre>int f(bool b, int *p)
{
return b && *p;
}
LLVM generates this with -O3 :
f(bool, int*): # @f(bool, int*)
xor eax, eax ; Note that eax is zero-ed here
test dil, dil
je .LBB0_2
xor eax, eax ; Zero-ing eax here is thus useless
cmp dword ptr [rsi], 0
setne al
.LBB0_2:
ret</pre>
</div>
</p>
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