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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [x86, SSE] should -1 vector constant creation be domain aware?"
href="https://llvm.org/bugs/show_bug.cgi?id=28129">28129</a>
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<th>Summary</th>
<td>[x86, SSE] should -1 vector constant creation be domain aware?
</td>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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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
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
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<th>Reporter</th>
<td>spatel+llvm@rotateright.com
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</tr>
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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>Disregard that we're adding NaN values here to just focus on the isel. :)
define <2 x double> @cmp_domain(<2 x double> %a) {
%cmp = fcmp oeq <2 x double> zeroinitializer, zeroinitializer
%sext = sext <2 x i1> %cmp to <2 x i64>
%mask = bitcast <2 x i64> %sext to <2 x double>
%add = fadd <2 x double> %a, %mask
ret <2 x double> %add
}
$ ./llc -o - cmp_domain.ll
pcmpeqd %xmm1, %xmm1
addpd %xmm1, %xmm0
retq
-----------------------------------------------------------------------------
The splat of -1 (NaN) is using an integer domain instruction (pcmpeqd), and
that's getting used by an FP domain instruction.
I'm not sure if this is an actual problem for any CPU...because the
splat-ones-creating-instruction should be recognized as an idiom and not
actually require any execution resources?
But I noticed this as part of:
<a href="http://reviews.llvm.org/D21269">http://reviews.llvm.org/D21269</a>
If we do want to fix this, I think we need to see what happens (in ExeDepsFix?)
to X86::V_SETALLONES versus X86::V_SET0.</pre>
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