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A register def can be partially dead when the whole register has use(s) but a subreg does not.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31760 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2006-11-15 20:54:11 +00:00
parent a6c4c1eb90
commit 9a1956ae6a
1 changed files with 8 additions and 1 deletions
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9
lib/CodeGen/LiveIntervalAnalysis.cpp
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@ -575,7 +575,6 @@ void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
// A physical register cannot be live across basic block, so its
// lifetime must end somewhere in its defining basic block.
DEBUG(std::cerr << "\t\tregister: "; printRegName(interval.reg));
typedef LiveVariables::killed_iterator KillIter;
unsigned baseIndex = MIIdx;
unsigned start = getDefIndex(baseIndex);
@ -599,6 +598,14 @@ void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
DEBUG(std::cerr << " killed");
end = getUseIndex(baseIndex) + 1;
goto exit;
} else if (lv_->ModifiesRegister(mi, interval.reg)) {
// Another instruction redefines the register before it is ever read.
// Then the register is essentially dead at the instruction that defines
// it. Hence its interval is:
// [defSlot(def), defSlot(def)+1)
DEBUG(std::cerr << " dead");
end = getDefIndex(start) + 1;
goto exit;
}
}