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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Loop vectorizer cannot generate runtime checks for uniform loads"
href="http://llvm.org/bugs/show_bug.cgi?id=19446">19446</a>
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<th>Summary</th>
<td>Loop vectorizer cannot generate runtime checks for uniform loads
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Loop Optimizer
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>hfinkel@anl.gov
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=12382" name="attach_12382" title="test case showing uniform load">attachment 12382</a> <a href="attachment.cgi?id=12382&action=edit" title="test case showing uniform load">[details]</a></span>
test case showing uniform load
Currently, AccessAnalysis::canCheckPtrAtRT calls hasComputableBounds, and
hasComputableBounds has:
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PtrScev);
if (!AR)
return false;
return AR->isAffine();
so we don't generate runtime checks for uniform loads. For example, if the loop
has:
%12 = load double* %ref3, align 8, !tbaa !4
%arrayidx = getelementptr inbounds [10000000 x double]* @c, i64 0, i64
%.idx..015
%13 = load double* %arrayidx, align 8, !tbaa !4
%mul5 = fmul double %12, %13
where %ref3 is loop invariant, this loop will not vectorize because we won't
generate the necessary runtime check. I've attached a (simple) test case.</pre>
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