https://llvm.org/bugs/show_bug.cgi?id=28129
Bug ID: 28129
Summary: [x86, SSE] should -1 vector constant creation be
domain aware?
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: spatel+l...@rotateright.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
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:
http://reviews.llvm.org/D21269
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.
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