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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 --- - GVNHoist hoists a store above a load of the same memory location"
href="https://llvm.org/bugs/show_bug.cgi?id=30216">30216</a>
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<th>Summary</th>
<td>GVNHoist hoists a store above a load of the same memory location
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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>All
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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>
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<th>Assignee</th>
<td>sebpop@gmail.com
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<th>Reporter</th>
<td>george.burgess.iv@gmail.com
</td>
</tr>
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<th>CC</th>
<td>dberlin@dberlin.org, llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Hi! I have a repro of a bug for you (on r280192):
$ echo '
@A = external global i8
@B = external global i8*
define i8* @Foo() {
store i8 0, i8* @A
br i1 undef, label %if.then, label %if.else
if.then:
store i8* null, i8** @B
ret i8* null
if.else:
%1 = load i8*, i8** @B
store i8* null, i8** @B
ret i8* %1
}
' | opt -gvn-hoist -S
@A = external global i8
@B = external global i8*
define i8* @Foo() {
store i8 0, i8* @A
store i8* null, i8** @B
br i1 undef, label %if.then, label %if.else
if.then: ; preds = %0
ret i8* null
if.else: ; preds = %0
%1 = load i8*, i8** @B
ret i8* %1
}
The hoist of the store to @B above a load of @B is illegal. This won't repro
without the store to @A at the top. :)</pre>
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