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RegisterCoalescer: Cleanup and improved comment for a subtle detail.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226353 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthias Braun 2015-01-17 00:33:13 +00:00
parent b26c2fc557
commit 0553dac91f
1 changed files with 8 additions and 6 deletions
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14
lib/CodeGen/RegisterCoalescer.cpp
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@ -2345,19 +2345,21 @@ void JoinVals::eraseInstrs(SmallPtrSetImpl<MachineInstr*> &ErasedInstrs,
// Get the def location before markUnused() below invalidates it.
SlotIndex Def = LR.getValNumInfo(i)->def;
switch (Vals[i].Resolution) {
case CR_Keep:
case CR_Keep: {
// If an IMPLICIT_DEF value is pruned, it doesn't serve a purpose any
// longer. The IMPLICIT_DEF instructions are only inserted by
// PHIElimination to guarantee that all PHI predecessors have a value.
if (!Vals[i].ErasableImplicitDef || !Vals[i].Pruned)
break;
// Remove value number i from LR. Note that this VNInfo is still present
// in NewVNInfo, so it will appear as an unused value number in the final
// joined interval.
LR.getValNumInfo(i)->markUnused();
LR.removeValNo(LR.getValNumInfo(i));
// Remove value number i from LR.
VNInfo *VNI = LR.getValNumInfo(i);
LR.removeValNo(VNI);
// Note that this VNInfo is reused and still referenced in NewVNInfo,
// make it appear like an unused value number.
VNI->markUnused();
DEBUG(dbgs() << "\t\tremoved " << i << '@' << Def << ": " << LR << '\n');
// FALL THROUGH.
}
case CR_Erase: {
MachineInstr *MI = Indexes->getInstructionFromIndex(Def);