<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Redundant extra XOR"
href="https://bugs.llvm.org/show_bug.cgi?id=41326">41326</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Redundant extra XOR
</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>
<tr>
<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>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.bolvansky@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>unsigned extra_xor(unsigned a, unsigned b)
{
if (a == 0 || b == 0)
return 0;
unsigned y = 0;
while (b != 0)
{
if (b & 1ul)
y ^= a;
a <<= 1;
b >>= 1;
}
return y;
}
extra_xor(unsigned int, unsigned int):
xor eax, eax
test edi, edi
je .LBB0_4
test esi, esi
je .LBB0_4
xor eax, eax <------- should be eliminated
.LBB0_3:
mov ecx, esi
and ecx, 1
neg ecx
and ecx, edi
xor eax, ecx
add edi, edi
shr esi
jne .LBB0_3
.LBB0_4:
ret</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>