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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 --- - Reassociate wrongly preserves nuw" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D23926&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=wWxdXLcnx_3F0TsURXEbVGoh-g-57OhmZvFGGNHerrk&s=-eRBMyaaQqh2s_fDGMBki2gD2FFSeSn7Tw3mDRlbPBI&e=">23926</a>
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<th>Summary</th>
<td>Reassociate wrongly preserves nuw
</td>
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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>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>Keywords</th>
<td>miscompilation
</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>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>nunoplopes@sapo.pt
</td>
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<th>CC</th>
<td>david.majnemer@gmail.com, llvmbugs@cs.uiuc.edu, regehr@cs.utah.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>$ cat bug.ll
define i2 @func78000101(i2, i2) {
%3 = add nuw i2 %0, 1
%4 = sub nuw nsw i2 %1, %3
ret i2 %4
}
$ opt -reassociate -S bug.ll
define i2 @func78000101(i2, i2) {
%.neg = sub i2 0, %0
%.neg1 = add nuw i2 %.neg, -1
%3 = add i2 %.neg1, %1
ret i2 %3
}
$ ./alive.py bug.opt
----------------------------------------
Optimization: func78000101
Precondition: true
%3 = add nuw i2 %0, 1
%4 = sub nuw nsw i2 %1, %3
ret i2 %4
=>
%.neg = sub i2 0, %0
%.neg1 = add nuw i2 %.neg, -1
%3 = add i2 %.neg1, %1
ret i2 %3
ERROR: Domain of undefinedness of Target is smaller than Source's for i2 %3
Example:
%0 i2 = 0x2 (2, -2)
%1 i2 = 0x0 (0)
%.neg i2 = 0x2 (2, -2)
%.neg1 i2 = 0x1 (1)
Undef inputs: %1
Source value: 0x3 (3, -1)
Target value: undef</pre>
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