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Not safe to "kill" a register if its live range extends pass the end of block branch.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49911 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2008-04-18 19:22:23 +00:00
parent 3f73beaeb2
commit 883d260045
1 changed files with 29 additions and 3 deletions
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32
lib/CodeGen/SimpleRegisterCoalescing.cpp
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@ -613,6 +613,19 @@ static void PropagateDeadness(LiveInterval &li, MachineInstr *CopyMI,
}
}
/// isSameOrFallThroughBB - Return true if MBB == SuccMBB or MBB simply
/// fallthoughs to SuccMBB.
static bool isSameOrFallThroughBB(MachineBasicBlock *MBB,
MachineBasicBlock *SuccMBB,
const TargetInstrInfo *tii_) {
if (MBB == SuccMBB)
return true;
MachineBasicBlock *TBB = 0, *FBB = 0;
std::vector<MachineOperand> Cond;
return !tii_->AnalyzeBranch(*MBB, TBB, FBB, Cond) && !TBB && !FBB &&
MBB->isSuccessor(SuccMBB);
}
/// ShortenDeadCopySrcLiveRange - Shorten a live range as it's artificially
/// extended by a dead copy. Mark the last use (if any) of the val# as kill as
/// ends the live range there. If there isn't another use, then this live range
@ -643,14 +656,29 @@ SimpleRegisterCoalescing::ShortenDeadCopySrcLiveRange(LiveInterval &li,
// More uses past this copy? Nothing to do.
return false;
MachineBasicBlock *CopyMBB = CopyMI->getParent();
unsigned MBBStart = li_->getMBBStartIdx(CopyMBB);
unsigned LastUseIdx;
MachineOperand *LastUse = lastRegisterUse(LR->start, CopyIdx-1, li.reg,
LastUseIdx);
if (LastUse) {
MachineInstr *LastUseMI = LastUse->getParent();
if (!isSameOrFallThroughBB(LastUseMI->getParent(), CopyMBB, tii_)) {
// r1024 = op
// ...
// BB1:
// = r1024
//
// BB2:
// r1025<dead> = r1024<kill>
if (MBBStart < LR->end)
removeRange(li, MBBStart, LR->end, li_, tri_);
return false;
}
// There are uses before the copy, just shorten the live range to the end
// of last use.
LastUse->setIsKill();
MachineInstr *LastUseMI = LastUse->getParent();
removeRange(li, li_->getDefIndex(LastUseIdx), LR->end, li_, tri_);
unsigned SrcReg, DstReg;
if (tii_->isMoveInstr(*LastUseMI, SrcReg, DstReg) &&
@ -663,8 +691,6 @@ SimpleRegisterCoalescing::ShortenDeadCopySrcLiveRange(LiveInterval &li,
}
// Is it livein?
MachineBasicBlock *CopyMBB = CopyMI->getParent();
unsigned MBBStart = li_->getMBBStartIdx(CopyMBB);
if (LR->start <= MBBStart && LR->end > MBBStart) {
if (LR->start == 0) {
assert(TargetRegisterInfo::isPhysicalRegister(li.reg));