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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - EarlyCSE is pessimistic around backedges"
href="https://llvm.org/bugs/show_bug.cgi?id=27547">27547</a>
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<th>Summary</th>
<td>EarlyCSE is pessimistic around backedges
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>sanjoy@playingwithpointers.com
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</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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</tr></table>
<p>
<div>
<pre>EarlyCSE optimizes the store in @f0 to store "true", but not the one in @f1.
Looks like EarlyCSE needlessly depends on %stay having one predecessor.
define void @f0(i32 %x, i1* %ptr) {
%c = icmp eq i32 %x, 0
br i1 %c, label %stay, label %leave
leave:
ret void
stay:
%c2 = icmp eq i32 %x, 0
store i1 %c2, i1* %ptr
ret void
}
define void @f1(i32 %x, i1* %ptr) {
%c = icmp eq i32 %x, 0
br i1 %c, label %stay, label %leave
leave:
ret void
stay:
%c2 = icmp eq i32 %x, 0
store i1 %c2, i1* %ptr
br label %stay
}</pre>
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</p>
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