<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 - (popcount(x) ^ popcount(y)) & 1 - > (popcount(x ^ y)) & 1"
href="https://bugs.llvm.org/show_bug.cgi?id=50094">50094</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>(popcount(x) ^ popcount(y)) & 1 - > (popcount(x ^ y)) & 1
</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>Scalar Optimizations
</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>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Original pattern: (__builtin_parity(x) ^ __builtin_parity(y))
LLVM rewrites it as: (__builtin_popcount(x) ^ __builtin_popcount(y)) & 1
----------------------------------------
define i32 @src(i32 %0, i32 %1) noread nowrite nofree {
%2:
%3 = ctpop i32 %0
%4 = ctpop i32 %1
%5 = xor i32 %4, %3
%6 = and i32 %5, 1
ret i32 %6
}
=>
define i32 @tgt(i32 %0, i32 %1) noread nowrite nofree {
%2:
%3 = xor i32 %1, %0
%4 = ctpop i32 %3
%5 = and i32 %4, 1
ret i32 %5
}
Transformation seems to be correct!
parity_xor(unsigned int, unsigned int): #
@parity_xor(unsigned int, unsigned int)
popcnt ecx, edi
popcnt eax, esi
xor eax, ecx
and eax, 1
ret
tgt(unsigned int, unsigned int): # @tgt(unsigned
int, unsigned int)
xor edi, esi
popcnt eax, edi
and eax, 1
ret
<a href="https://godbolt.org/z/v3h361fz7">https://godbolt.org/z/v3h361fz7</a></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>