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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missed loop vectorization"
href="https://bugs.llvm.org/show_bug.cgi?id=49476">49476</a>
</td>
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<tr>
<th>Summary</th>
<td>Missed loop vectorization
</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>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Loop Optimizer
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<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 M 32000
#define N 256
double a[M],x[N][N];
void compute()
{
for (int j = 0; j < N; j++) {
for (int i = j+1; i < N; i++) {
a[i] -= x[j][i] * a[j];
}
}
}
With -Ofast, LLVM does not vectorize this code.
for a[j]:
remark: failed to move load with loop-invariant address because the loop may
invalidate its value [-Rpass-missed=licm]
<a href="https://godbolt.org/z/Gx6Px4">https://godbolt.org/z/Gx6Px4</a></pre>
</div>
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