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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [NewGVN] Miscompile with nonnull metadata"
href="https://bugs.llvm.org/show_bug.cgi?id=37540">37540</a>
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<th>Summary</th>
<td>[NewGVN] Miscompile with nonnull metadata
</td>
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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>All
</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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</tr>
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<th>Reporter</th>
<td>nikita.ppv@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>NewGVN optimizes:
define i1 @test({}** %arg, i1 %arg2) {
br i1 %arg2, label %bb1, label %bb2
bb1:
%load1 = load {}*, {}** %arg
%cmp1 = icmp eq {}* %load1, null
ret i1 %cmp1
bb2:
%load2 = load {}*, {}** %arg, !nonnull !1
%cmp2 = icmp eq {}* %load2, null
ret i1 %cmp2
}
!1 = !{}
into:
define i1 @test({}** %arg, i1 %arg2) {
br i1 %arg2, label %bb1, label %bb2
bb1: ; preds = %0
ret i1 false
bb2: ; preds = %0
ret i1 false
}
The reason is that %load1 and %load2 are found congruent with %load2 chosen as
leader. Thus %cmp1 in bb1 calls SimplifyCmp with icmp eq {}* %load2, null,
which is simplified to i1 false based on the !nonnull metadata of %load2.
However, this metadata is not applicable in this branch.
This bug prevents bootstrapping of rustc under newgvn.</pre>
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