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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [x86, SSE] unnecessary shifts for bitwise logic with comparison (pcmp)?"
href="https://llvm.org/bugs/show_bug.cgi?id=28486">28486</a>
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<th>Summary</th>
<td>[x86, SSE] unnecessary shifts for bitwise logic with comparison (pcmp)?
</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
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<th>Component</th>
<td>Backend: X86
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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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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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</tr></table>
<p>
<div>
<pre>I don't know how a <4 x i1> parameter is mapped to an XMM reg. In the larger
motivating example, the %boolvec is not a function parameter; it's a loop
value/phi, so this may not be an accurate minimization.
define <4 x i32> @bool_or(<4 x i32> %a, <4 x i32> %b, <4 x i1> %boolvec) {
%cmp = icmp eq <4 x i32> %a, %b
%or = or <4 x i1> %boolvec, %cmp
%ext = sext <4 x i1> %or to <4 x i32>
ret <4 x i32> %ext
}
$ ./llc -o - boolvec2.ll
pcmpeqd %xmm1, %xmm0
por %xmm2, %xmm0 <--- assume %xmm2 conforms to getBooleanContents?
pslld $31, %xmm0
psrad $31, %xmm0 <--- if so, shifts are unnecessary
retq</pre>
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