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Never attempt to join an early-clobber def with a regular kill.

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This fixes PR14194.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166880 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2012-10-27 17:41:27 +00:00
parent badffcf8fd
commit 163f67f4d9
2 changed files with 23 additions and 0 deletions
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14
lib/CodeGen/RegisterCoalescer.cpp
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@@ -1492,6 +1492,20 @@ JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
if ((V.WriteLanes & OtherV.ValidLanes) == 0)
return CR_Replace;
// If the other live range is killed by DefMI and the live ranges are still
// overlapping, it must be because we're looking at an early clobber def:
//
// %dst<def,early-clobber> = ASM %src<kill>
//
// In this case, it is illegal to merge the two live ranges since the early
// clobber def would clobber %src before it was read.
if (OtherLRQ.isKill()) {
// This case where the def doesn't overlap the kill is handled above.
assert(VNI->def.isEarlyClobber() &&
"Only early clobber defs can overlap a kill");
return CR_Impossible;
}
// VNI is clobbering live lanes in OtherVNI, but there is still the
// possibility that no instructions actually read the clobbered lanes.
// If we're clobbering all the lanes in OtherVNI, at least one must be read.