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- Merge UsedBlocks info after two virtual registers are coalesced.

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- Use distance to closest use to determine whether to abort coalescing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35141 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-03-18 09:05:55 +00:00
parent e951cd1647
commit cf596c54d4
1 changed files with 30 additions and 23 deletions
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53
lib/CodeGen/LiveIntervalAnalysis.cpp
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@ -940,48 +940,50 @@ bool LiveIntervals::JoinCopy(MachineInstr *CopyMI,
if (ReduceJoinPhys && !isDead &&
MRegisterInfo::isPhysicalRegister(repSrcReg)) {
// Small function. No need to worry!
if (r2iMap_.size() <= allocatableRegs_.size() * 2)
unsigned Threshold = allocatableRegs_.count() * 2;
if (r2iMap_.size() <= Threshold)
goto TryJoin;
LiveVariables::VarInfo& dvi = lv_->getVarInfo(repDstReg);
// Is the value used in the current BB or any immediate successroe BB?
MachineBasicBlock *SrcBB = CopyMI->getParent();
if (!dvi.UsedBlocks[SrcBB->getNumber()]) {
for (MachineBasicBlock::succ_iterator SI = SrcBB->succ_begin(),
SE = SrcBB->succ_end(); SI != SE; ++SI) {
MachineBasicBlock *SuccMBB = *SI;
if (dvi.UsedBlocks[SuccMBB->getNumber()])
MachineBasicBlock *CopyBB = CopyMI->getParent();
if (dvi.UsedBlocks[CopyBB->getNumber()])
goto TryJoin;
for (MachineBasicBlock::succ_iterator SI = CopyBB->succ_begin(),
SE = CopyBB->succ_end(); SI != SE; ++SI) {
MachineBasicBlock *SuccMBB = *SI;
if (dvi.UsedBlocks[SuccMBB->getNumber()])
goto TryJoin;
}
}
// Ok, no use in this BB and no use in immediate successor BB's. Be really
// careful now!
// It's only used in one BB, forget about it!
if (dvi.UsedBlocks.count() <= 1) {
if (dvi.UsedBlocks.count() < 2) {
++numAborts;
return false;
}
// Examine all the blocks where the value is used. If any is in the same
// loop, then it's ok. Or if the current BB is a preheader of any of the
// loop that uses this value, that's ok as well.
const LoopInfo &LI = getAnalysis<LoopInfo>();
const Loop *L = LI.getLoopFor(SrcBB->getBasicBlock());
// Determine whether to allow coalescing based on how far the closest
// use is.
unsigned CopyIdx = getInstructionIndex(CopyMI);
unsigned MinDist = i2miMap_.size() * InstrSlots::NUM;
int UseBBNum = dvi.UsedBlocks.find_first();
while (UseBBNum != -1) {
MachineBasicBlock *UseBB = mf_->getBlockNumbered(UseBBNum);
const Loop *UL = LI.getLoopFor(UseBB->getBasicBlock());
if ((UL && UL == L) || // A use in the same loop
(UL && L && // A use in a loop and this BB is the preheader
UL->getLoopPreheader() == SrcBB->getBasicBlock()))
goto TryJoin;
unsigned UseIdx = getMBBStartIdx(UseBB);
if (UseIdx > CopyIdx) {
MinDist = std::min(MinDist, UseIdx - CopyIdx);
if (MinDist <= Threshold)
break;
}
UseBBNum = dvi.UsedBlocks.find_next(UseBBNum);
}
// Don't do it!
++numAborts;
return false;
if (MinDist > Threshold) {
// Don't do it!
++numAborts;
return false;
}
}
TryJoin:
@ -1038,6 +1040,11 @@ TryJoin:
if (MRegisterInfo::isPhysicalRegister(repDstReg)) {
for (const unsigned *AS = mri_->getAliasSet(repDstReg); *AS; ++AS)
getInterval(*AS).MergeInClobberRanges(SrcInt);
} else {
// Merge UsedBlocks info if the destination is a virtual register.
LiveVariables::VarInfo& dVI = lv_->getVarInfo(repDstReg);
LiveVariables::VarInfo& sVI = lv_->getVarInfo(repSrcReg);
dVI.UsedBlocks |= sVI.UsedBlocks;
}
DOUT << "\n\t\tJoined. Result = "; DestInt.print(DOUT, mri_);