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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 - Loop with "# pragma clang loop interleave (enable)" is not interleaved"
href="https://bugs.llvm.org/show_bug.cgi?id=47667">47667</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Loop with "# pragma clang loop interleave (enable)" is not interleaved
</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>fj8765ah@aa.jp.fujitsu.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>If you write "# pragma loop interleave (enable)" and "# pragma loop vectorize
(enable)" on the loop, the behavior is the same.
The reason is that they both create metadata like this:.
!8 = !{!"llvm.loop.vectorize.enable", i1 true}
Users will write these pragmas if they want to vectorize or interleave.
However, if "# pragma clang loop interleave (enable)" is specified, it is not
interleaved.
I think it should be interleaved. What do you think?
I think we should do one of the following two things.
* When the metadata described above exists, apply both vectorization and
interleaving.
* Create and control separate metadata for each.
It seems that interleaving is not controlled by the pragma but controlled by
the -funroll-loops option.
By the way, "# pragma clang loop interleave (disable)" is controlled by the
following metadata, so there is no problem.
!25 = !{!"llvm.loop.interleave.count", i32 1}
- interleave.c :
void foo(double * restrict a,
double * restrict b,
double * restrict c,
int n) {
#pragma clang loop interleave(enable)
for (int i=0;i<n;i++)
c[i] = a[i] + b[i];
return;
}
$ clang -O1 interleave.c -Rpass=loop-vector -S -Rpass-analysis=loop-vector
interleave.c:7:3: remark: the cost-model indicates that interleaving is
beneficial but is explicitly disabled or interleave count is set to 1
[-Rpass-analysis=loop-vectorize]
for (int i=0;i<n;i++)
^
interleave.c:7:3: remark: vectorized loop (vectorization width: 2, interleaved
count: 1) [-Rpass=loop-vectorize]
$ clang -O1 interleave.c -Rpass=loop-vector -S -funroll-loops
interleave.c:7:3: remark: vectorized loop (vectorization width: 2, interleaved
count: 2) [-Rpass=loop-vectorize]
for (int i=0;i<n;i++)
^
- vectorize.c :
void foo(double * restrict a,
double * restrict b,
double * restrict c,
int n) {
#pragma clang loop vectorize(enable)
for (int i=0;i<n;i++)
c[i] = a[i] + b[i];
return;
}
$ clang -O1 vectorize.c -Rpass=loop-vector -S -Rpass-analysis=loop-vector
vectorize.c:7:3: remark: the cost-model indicates that interleaving is
beneficial but is explicitly disabled or interleave count is set to 1
[-Rpass-analysis=loop-vectorize]
for (int i=0;i<n;i++)
^
vectorize.c:7:3: remark: vectorized loop (vectorization width: 2, interleaved
count: 1) [-Rpass=loop-vectorize]
$ clang -O1 vectorize.c -Rpass=loop-vector -S -funroll-loops
vectorize.c:7:3: remark: vectorized loop (vectorization width: 2, interleaved
count: 2) [-Rpass=loop-vectorize]
for (int i=0;i<n;i++)
^</pre>
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