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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - wrong code at -O2 on x86_64-linux-gnu"
href="https://bugs.llvm.org/show_bug.cgi?id=45360">45360</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code at -O2 on x86_64-linux-gnu
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>qrzhang@gatech.edu
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>It appears to be a recent regression. It happens at O2 and above. O1 works
fine.
$ clang-trunk -v
clang version 11.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
f6b2c003f360c3d0dcfe13d751805643f229f79b)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
$ clang-trunk abc.c ; ./a.out
0
$ clang-trunk -O2 abc.c ; ./a.out
Floating point exception (core dumped)
$ cat abc.c
int printf(const char *, ...);
int a, c, d, e, f, h, i;
unsigned b, k;
short g, j;
volatile int l;
int m() {
for (;;) {
j = 2;
for (; j >= 0; j--)
for (; g;)
;
h = 0;
for (; h <= 2; h++)
f &= d;
e = 0;
for (; e <= 2; e++) {
if (k)
for (; l; l--)
;
if (j) {
i = f == 0 ? 0 : b % f;
if (i)
;
else
return 1;
} else {
c = 0;
for (; c != 5; c = c + 5)
f = 0;
}
}
}
}
int main() {
m();
printf("%X\n", a);
}</pre>
</div>
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