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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 reports change made incorrectly"
href="https://llvm.org/bugs/show_bug.cgi?id=28208">28208</a>
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<th>Summary</th>
<td>Reassociate reports change made incorrectly
</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>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>apilipenko@azulsystems.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>Reassociate pass returns true with no change made on the following function:
define i64 @test(i64 %a, i64 %b) {
%1 = and i64 %b, %a
ret i64 %1
}
opt -S reassociate.ll -reassociate -debug-pass=Executions
[2016-06-20 08:55:35.332437000] 0x1906670 Executing Pass 'Function Pass
Manager' on Module 'simple.ll'...
[2016-06-20 08:55:35.332704000] 0x1908770 Executing Pass 'Reassociate
expressions' on Function 'test'...
[2016-06-20 08:55:35.333682000] 0x1908770 *Made Modification* 'Reassociate
expressions' on Function 'test'...
[2016-06-20 08:55:35.333792000] 0x1908770 Freeing Pass 'Reassociate
expressions' on Function 'test'...
[2016-06-20 08:55:35.333837000] 0x1908770 Executing Pass 'Module Verifier'
on Function 'test'...
[2016-06-20 08:55:35.334012000] 0x1908770 Freeing Pass 'Module Verifier'
on Function 'test'...
[2016-06-20 08:55:35.334048000] 0x1906670 Made Modification 'Function Pass
Manager' on Module 'simple.ll'...
[2016-06-20 08:55:35.334077000] 0x1906670 Executing Pass 'Print module to
stderr' on Module 'simple.ll'...
It happens because it performs two distinct transformations which nullify each
other (canonicalizeOperands swaps arguments of an and and then
ReassociateExpression swaps them back).</pre>
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