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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 - TargetLowering.SimplifySetCC - missing icmp eq knownbits combine"
href="https://bugs.llvm.org/show_bug.cgi?id=41182">41182</a>
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<th>Summary</th>
<td>TargetLowering.SimplifySetCC - missing icmp eq knownbits combine
</td>
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<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>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Common Code Generator Code
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>lebedev.ri@gmail.com, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
</td>
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<p>
<div>
<pre><a href="https://gcc.godbolt.org/z/JahwVe">https://gcc.godbolt.org/z/JahwVe</a>
define i32 @square(i32 %a0) {
%1 = and i32 %a0, 127
%2 = icmp eq i32 %1, -2
%3 = select i1 %2, i32 42, i32 -17
ret i32 %3
}
square: # @square
andl $127, %edi
cmpl $-2, %edi
movl $42, %ecx
movl $-17, %eax
cmovel %ecx, %eax
retq
We should be able to constant fold this completely as we know that some of the
known bits will never match:
square: # @square
movl $-17, %eax
retq</pre>
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