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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [NewGVN] Running NewGVN twice back-to-back discovers additional equivalences"
href="https://bugs.llvm.org/show_bug.cgi?id=38683">38683</a>
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<th>Summary</th>
<td>[NewGVN] Running NewGVN twice back-to-back discovers additional equivalences
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
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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>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>Florian.Hahn@arm.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>running `opt -newgvn -newgvn` on the code below eliminates %bf.set.1 and
%bf.clear.1, but `opt -newgvn` does not.
@a = external global i64
define void @fn1(i1 %bc) {
entry:
br label %for.cond
for.cond: ; preds = %for.cond1.1,
%entry
%tmp = phi i1 [ 1, %entry ], [ 1, %for.cond ]
%conv = zext i1 %tmp to i32
%lv = load i32, i32* bitcast (i64* @a to i32*)
%bf.clear = and i32 %lv, -131072
%bf.set = or i32 %conv, %bf.clear
%bf.clear.1 = and i32 %bf.set, -131072
%bf.set.1 = or i32 1, %bf.clear.1
br i1 %bc, label %for.cond, label %exit
exit: ; preds = %for.cond1
store i32 %bf.set.1, i32* bitcast (i64* @a to i32*)
ret void
}</pre>
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</p>
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