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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [loop vectorizer] disable loop unroll pass to unroll vectorized loop further"
href="https://llvm.org/bugs/show_bug.cgi?id=24414">24414</a>
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<th>Summary</th>
<td>[loop vectorizer] disable loop unroll pass to unroll vectorized loop further
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Loop Optimizer
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>wmi@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>For the testcase 1.c below:
int a[1000], b[1000], c[1000];
void foo(int N) {
int i;
for (i = 0; i < N; i++) {
a[i] = b[i] + c[i];
}
}
~/workarea/llvm-r243652/build/bin/clang -O2 -S 1.c
The loop in 1.c is vectorized and interleaved in loop vectorization. The
interleave factor is 2. After that loop unroll pass unrolls the vectorized loop
another time, and generates an extra loop prologue which cannot be merged with
the scalar remainder loop generated by loop vectorizer.
Maybe it is better to disable loop unroll pass to unroll vectorized loop
further. If it causes any regression, the component of interleave factor
computation needs to be tuned.</pre>
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</p>
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