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It is safe to remat a value killed by phis. 

The source live range is recomputed using shrinkToUses() which does
handle phis correctly.  The hasPHIKill() condition was relevant in the
old days when ReMaterializeTrivialDef() tried to recompute the live
range itself.

The shrinkToUses() function will mark the original def as dead when no
more uses and phi kills remain.  It is then removed by
runOnMachineFunction().

llvm-svn: 139781
This commit is contained in:
Jakob Stoklund Olesen 2011-09-15 04:52:06 +00:00
parent e7ca8ecd92
commit dca022e377
1 changed files with 1 additions and 3 deletions
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4
llvm/lib/CodeGen/RegisterCoalescer.cpp
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@ -805,9 +805,7 @@ bool RegisterCoalescer::ReMaterializeTrivialDef(LiveInterval &SrcInt,
LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
assert(SrcLR != SrcInt.end() && "Live range not found!");
VNInfo *ValNo = SrcLR->valno;
// If other defs can reach uses of this def, then it's not safe to perform
// the optimization.
if (ValNo->isPHIDef() || ValNo->isUnused() || ValNo->hasPHIKill())
if (ValNo->isPHIDef() || ValNo->isUnused())
return false;
MachineInstr *DefMI = LIS->getInstructionFromIndex(ValNo->def);
if (!DefMI)