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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [InstCombine] `x - ~(y)` vs `x + y + 1`"
href="https://bugs.llvm.org/show_bug.cgi?id=42457">42457</a>
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<th>Summary</th>
<td>[InstCombine] `x - ~(y)` vs `x + y + 1`
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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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>
</tr>
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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>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre><a href="https://godbolt.org/z/2N-IRy">https://godbolt.org/z/2N-IRy</a>
<a href="https://rise4fun.com/Alive/WMn">https://rise4fun.com/Alive/WMn</a>
int bad(unsigned x, unsigned y) {
return x - ~(y);
}
int good(unsigned x, unsigned y) {
return x + y + 1;
}
Name:
%o = xor i32 %y, -1
%r = sub i32 %x, %o
=>
%n = add i32 %y, 1
%r = add i32 %x, %n
We currently don't prefer any one to other, should we?
I'd guess we want the variant with 2 adds?</pre>
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