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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - O2 and O2 lto result differ"
href="https://bugs.llvm.org/show_bug.cgi?id=40373">40373</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>O2 and O2 lto result differ
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>6.0
</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>Interprocedural Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>konstantin.vladimirov@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Simple test (after creduce):
---
unsigned b, c, d, e, f;
int main() {
unsigned h[15] = {3, 12, 2, 10, 6, 11, 7, 9, 8, 14, 3, 5, 1, 4, 0};
unsigned long i[15] = {0}, j[15] = {0};
for (; e < 7; e++) {
for (d = 0; d < 15; d += 3) {
f = 305 ^ j[d] >> 5;
j[d] = (104 * j[d] ^ d) - (-j[d] < 8) & 906;
}
for (c = 1; c < 15; c++) {
b = i[h[c]];
i[h[c]] = 3 - i[h[c]];
}
}
return b;
}
---
clang -O2 test.c -o corr
clang -O2 -flto test.c -o wrong
<span class="quote">> wrong
> echo $?</span >
238
<span class="quote">> corr
> echo $?</span >
0
<span class="quote">> clang -v</span >
clang version 6.0.0 (tags/RELEASE_600/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i586-suse-linux/2.95.3
Found candidate GCC installation: /usr/lib64/gcc/x86_64-suse-linux/4.3
Selected GCC installation: /usr/lib64/gcc/x86_64-suse-linux/4.3
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64</pre>
</div>
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