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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 - Missed vectorization for loop with MAX"
href="https://bugs.llvm.org/show_bug.cgi?id=42917">42917</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missed vectorization for loop with MAX
</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>Loop Optimizer
</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>#define max(a,b) (((a) > (b))? (a) : (b))
unsigned p[512];
void vmax() {
for (int i = 0; i < 512; i+=2) {
p[i] = max(p[i], p[i+1]);
}
}
int main() {
for (int i = 0; i < 10000000; ++i) {
vmax();
}
}
icc -O3 vmax.c -march=haswell
0m0,096s
clang -O3 vmax.c -march=haswell
0m1,518s
clang with #pragma clang loop vectorize(enable) interleave(enable)
0m1,096s
<a href="https://godbolt.org/z/5bjKUI">https://godbolt.org/z/5bjKUI</a></pre>
</div>
</p>
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