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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [InstCombine] icmp eq/ne (and (lshr C, X), Y), 0 fold missed"
href="https://bugs.llvm.org/show_bug.cgi?id=42470">42470</a>
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<th>Summary</th>
<td>[InstCombine] icmp eq/ne (and (lshr C, X), Y), 0 fold missed
</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>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</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
</td>
</tr>
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<th>Reporter</th>
<td>lebedev.ri@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre><a href="https://rise4fun.com/Alive/Aq6">https://rise4fun.com/Alive/Aq6</a>
Name:
Pre: isPowerOf2(-C)
%o0 = lshr i8 C, %y
%o1 = and i8 %o0, %x
%r = icmp eq i8 %o1, 0
=>
%n1 = shl i8 %x, %y
%r = icmp ult i8 %n1, -C
Name:
Pre: isPowerOf2(-C)
%o0 = lshr i8 C, %y
%o1 = and i8 %o0, %x
%r = icmp ne i8 %o1, 0
=>
%n1 = shl i8 %x, %y
%r = icmp uge i8 %n1, -C
* Transforms/InstCombine/shl-and-negC-icmpeq-zero.ll
* Transforms/InstCombine/shl-and-signbit-icmpeq-zero.ll
regress in #42466 because of lack of the fold</pre>
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