<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 - Incorrect result with -O3 -march=skx"
href="https://bugs.llvm.org/show_bug.cgi?id=42833">42833</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Incorrect result with -O3 -march=skx
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Windows NT
</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>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>Vsevolod.Livinskij@frtk.ru
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Clang produces incorrect result with -O3 -march=skx
Reproducer:
#include <stdio.h>
int b;
unsigned c[49];
int d[49];
void i() {
for (int g = 32; g <= 48; g++) {
d[g] -= c[g] + b;
c[g] += c[g] + b;
b -= b;
}
}
int main() {
for (int g = 0; g < 49; ++g)
c[g] = 3;
i();
printf("%d\n", d[36]);
}
Error:
<span class="quote">>$ clang -O3 -march=skx small.c ; ./a.out</span >
0
<span class="quote">>$ clang -O0 -march=skx small.c ; ./a.out</span >
-3
LLVM version:
clang version 10.0.0 (trunk 367162)
Target: x86_64-unknown-linux-gnu
Thread model: posix</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>