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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Regression: Emits worse sequence for conditional move operation"
href="http://llvm.org/bugs/show_bug.cgi?id=16486">16486</a>
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<th>Summary</th>
<td>Regression: Emits worse sequence for conditional move operation
</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>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>david.majnemer@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
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<th>Classification</th>
<td>Unclassified
</td>
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<p>
<div>
<pre>consider the following:
define i32 @_Z4blahiiii(i32 %a, i32 %b, i32 %c, i32 %d) #0 {
entry:
%cmp = icmp sgt i32 %a, %b
%add = add nsw i32 %a, %c
%add1 = add nsw i32 %b, %d
%x.0 = select i1 %cmp, i32 %add, i32 %add1
ret i32 %x.0
}
this leaves us with:
addl %edi, %edx
addl %esi, %ecx
cmpl %esi, %edi
cmovgl %edx, %ecx
movl %ecx, %eax
ret
however, if we swap around operands a bit:
define i32 @_Z4blahiiii(i32 %a, i32 %b, i32 %c, i32 %d) #0 {
entry:
%cmp = icmp sgt i32 %a, %b
%add = add nsw i32 %c, %a
%add1 = add nsw i32 %d, %b
%x.0 = select i1 %cmp, i32 %add, i32 %add1
ret i32 %x.0
}
we instead get:
addl %edi, %edx
leal (%rcx,%rsi), %eax
cmpl %esi, %edi
cmovgl %edx, %eax
ret</pre>
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