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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Vectorization of a group of interleaved-stores with gaps using masked-vector-store is not supported"
href="https://bugs.llvm.org/show_bug.cgi?id=50566">50566</a>
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<th>Summary</th>
<td>Vectorization of a group of interleaved-stores with gaps using masked-vector-store is not supported
</td>
</tr>
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<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>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Loop Optimizer
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>dorit.nuzman@intel.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>Compiling the following:
void test(short *p, int n, int xoffset, int yoffset) {
#pragma clang loop vectorize(enable)
for( int i=0;i<n;i++){
p[i*4] += xoffset;
p[i*4 + 1] += yoffset;
}
}
with:
Clang -O2 -mllvm -enable-interleaved-mem-accesses -mllvm
-enable-masked-interleaved-mem-accesses
The vectorizer identifies the interleaved-loads-group and
interleaved-stores-group:
LV: We can vectorize this loop!
LV: Analyzing interleaved accesses...
LV: Creating an interleave group with: store i16 %conv7, i16 * %arrayidx4,
align 2
LV: Inserted: store i16 %conv1, i16 * %arrayidx, align 2
into the interleave group with store i16 %conv7, i16 )* %arrayidx4, align
2
LV: Creating an interleave group with: %3 = load i16, i16 * %arrayidx4, align
2
LV: Inserted: %2 = load i16, i16 * %arrayidx, align 2
into the interleave group with %3 = load i16, i16 * %arrayidx4, align 2
…but while it can support the loads as an interleaved-group, it cannot support
the stores as an interleaved-group:
LV: Invalidate candidate interleaved store group due to gaps.
LV: Interleaved group requires epilogue iteration.
…and so we have to resort to vectorizing the loop using scatter /
scalarization.
At the time <a href="https://reviews.llvm.org/D53668">https://reviews.llvm.org/D53668</a> added support for vectorizing a
group of interleaved-loads with gaps using a masked wide-load, but support for
the symmetric case of stores is still missing.</pre>
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</p>
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