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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - wrong codegen (miscompile) for weird type"
href="https://llvm.org/bugs/show_bug.cgi?id=27825">27825</a>
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</tr>
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<th>Summary</th>
<td>wrong codegen (miscompile) for weird type
</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>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>spatel+llvm@rotateright.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>As noted here:
<a href="https://groups.google.com/d/msg/llvm-dev/QhPhmkfwWmY/XCyol-XjCAAJ">https://groups.google.com/d/msg/llvm-dev/QhPhmkfwWmY/XCyol-XjCAAJ</a>
Something (during DAG type legalization?) is going wrong in this simple
example:
@g = constant i8 128
define i8 @main() {
%ptr = bitcast i8* @g to i7*
%v7 = load i7, i7* %ptr
; br label %cmp
; cmp:
%ret = zext i7 %v7 to i8
ret i8 %ret
}
$ ./llc -o - i7.ll | ./clang -x assembler - -o i7 && ./i7 ; echo $?
128
The high bit of the i8 value should have been masked off. If you uncomment the
branch+label, it works as expected (but we should confirm that's not two wrongs
making it right):
$ ./llc -o - i7.ll | ./clang -x assembler - -o i7 && ./i7 ; echo $?
0</pre>
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