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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - swap select operands and reuse existing inverted condition"
href="https://bugs.llvm.org/show_bug.cgi?id=41113">41113</a>
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<th>Summary</th>
<td>swap select operands and reuse existing inverted condition
</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>PC
</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>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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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>spatel+llvm@rotateright.com
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</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>I'm not sure if there's an existing pass that should have responsibility for
this transform:
define i1 @swapportunity(i8 %a, i8 %b, i8 %c, i8 %d, i8* %p) {
%cmp1 = icmp ult i8 %a, %b
%sel = select i1 %cmp1, i8 %c, i8 %d
store i8 %sel, i8* %p
%cmp2 = icmp uge i8 %a, %b ; this could also be a 'not' of cmp1
ret i1 %cmp2
}
-->
define i1 @swapportunity(i8 %a, i8 %b, i8 %c, i8 %d, i8* %p) {
%cmp2 = icmp uge i8 %a, %b
%swap = select i1 %cmp2, i8 %d, i8 %c
store i8 %swap, i8* %p
ret i1 %cmp2
}
-------------------------------------------------------------------
It's not quite CSE or instcombine. There's precedence for a similar
analysis/transform in instcombine via "swapMayExposeCSEOpportunities()", but
that seems suspect to include there as this is not really a local/peephole
pattern-match.</pre>
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</p>
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