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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 with gather"
href="https://bugs.llvm.org/show_bug.cgi?id=48044">48044</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missed loop vectorization with gather
</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>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>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>int c1[256], c2[256], r[256];
unsigned int f[256*257];
#define SETMASK (1 << 21)
#define CLEARMASK (~(SETMASK))
void foo(void)
{
int i, j, base;
for (i = 0; i <=255; i++) {
base = r[i];
for (j = 0; j <= 255; j++) {
c1[j] = f[(j << 8) + base] & CLEARMASK;
c2[j] = (f[(j << 8) + base + 1] & CLEARMASK) - 1;
}
}
}
O3 AVX2: Loop not vectorized due to cost model.
ICC vectorizes it.
<a href="https://godbolt.org/z/9E5ehz">https://godbolt.org/z/9E5ehz</a></pre>
</div>
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