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That funny 2-address lowering pass can also cause multiple definitions,

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fortunately, they are easy to handle if we know about them.  This patch fixes
some serious pessimization of code produced by the linscan register allocator.

llvm-svn: 15092
This commit is contained in:
Chris Lattner 2004-07-22 00:04:14 +00:00
parent eb21652fba
commit 25dd6b0a24
1 changed files with 18 additions and 8 deletions
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26
lib/CodeGen/LiveIntervals.cpp
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@ -291,10 +291,10 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg);
// Virtual registers may be defined multiple times (due to phi
// elimination). Much of what we do only has to be done once for the vreg.
// We use an empty interval to detect the first time we see a vreg.
// elimination and 2-addr elimination). Much of what we do only has to be
// done once for the vreg. We use an empty interval to detect the first
// time we see a vreg.
if (interval.empty()) {
// Get the Idx of the defining instructions.
unsigned defIndex = getDefIndex(getInstructionIndex(mi));
@ -351,11 +351,21 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
} else {
// If this is the second time we see a virtual register definition, it
// must be due to phi elimination. In this case, the defined value will
// be live until the end of the basic block it is defined in.
unsigned defIndex = getDefIndex(getInstructionIndex(mi));
interval.addRange(defIndex,
getInstructionIndex(&mbb->back()) + InstrSlots::NUM);
// must be due to phi elimination or two addr elimination. If this is
// the result of two address elimination, then the vreg is the first
// operand, and is a def-and-use.
if (mi->getOperand(0).isRegister() &&
mi->getOperand(0).getReg() == interval.reg &&
mi->getOperand(0).isDef() && mi->getOperand(0).isUse()) {
// If this is a two-address definition, just ignore it.
} else {
// Otherwise, this must be because of phi elimination. In this case,
// the defined value will be live until the end of the basic block it
// is defined in.
unsigned defIndex = getDefIndex(getInstructionIndex(mi));
interval.addRange(defIndex,
getInstructionIndex(&mbb->back()) + InstrSlots::NUM);
}
}
DEBUG(std::cerr << '\n');