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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 - [SimplifyCFG] Alignment mismatch prevents sinking"
href="https://bugs.llvm.org/show_bug.cgi?id=45772">45772</a>
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<th>Summary</th>
<td>[SimplifyCFG] Alignment mismatch prevents sinking
</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>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>nikita.ppv@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>opt -S -simplifycfg -sink-common-insts
define void @test(i1 %c, i32* %p1, i32* %p2) {
br i1 %c, label %if1, label %if2
if1:
store i32 0, i32* %p1, align 4
br label %end
if2:
store i32 0, i32* %p2, align 8
br label %end
end:
ret void
}
will not sink the stores into end, because the alignment of the stores differs.
Using align 4 on both stores will sink.
This is because SimplifyCFG checks isSameOperationAs() without the
CompareIgnoringAlignment flag. I believe it should be setting the flag and then
picking the minimum alignment for load/store (possibly by extending andIRFlags
to do that).
Noticed this as an unexpected improvement when inferring less alignment
information.</pre>
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