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Add a utility function for conservatively clearing kill flags, and make

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use of it in MachineCSE.

llvm-svn: 103726
This commit is contained in:
Dan Gohman 2010-05-13 19:24:00 +00:00
parent d7b4c5b82e
commit 223379b3a9
3 changed files with 19 additions and 1 deletions
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6
include/llvm/CodeGen/MachineRegisterInfo.h
View File

@ -162,6 +162,12 @@ public:
/// register or null if none is found. This assumes that the code is in SSA
/// form, so there should only be one definition.
MachineInstr *getVRegDef(unsigned Reg) const;
/// clearKillFlags - Iterate over all the uses of the given register and
/// clear the kill flag from the MachineOperand. This function is used by
/// optimization passes which extend register lifetimes and need only
/// preserve conservative kill flag information.
void clearKillFlags(unsigned Reg) const;
#ifndef NDEBUG
void dumpUses(unsigned RegNo) const;

5
lib/CodeGen/MachineCSE.cpp
View File

@ -112,6 +112,7 @@ bool MachineCSE::PerformTrivialCoalescing(MachineInstr *MI,
DEBUG(dbgs() << "Coalescing: " << *DefMI);
DEBUG(dbgs() << "*** to: " << *MI);
MO.setReg(SrcReg);
MRI->clearKillFlags(SrcReg);
if (NewRC != SRC)
MRI->setRegClass(SrcReg, NewRC);
DefMI->eraseFromParent();
@ -365,8 +366,10 @@ bool MachineCSE::ProcessBlock(MachineBasicBlock *MBB) {
// Actually perform the elimination.
if (DoCSE) {
for (unsigned i = 0, e = CSEPairs.size(); i != e; ++i)
for (unsigned i = 0, e = CSEPairs.size(); i != e; ++i) {
MRI->replaceRegWith(CSEPairs[i].first, CSEPairs[i].second);
MRI->clearKillFlags(CSEPairs[i].second);
}
MI->eraseFromParent();
++NumCSEs;
} else {

9
lib/CodeGen/MachineRegisterInfo.cpp
View File

@ -133,6 +133,15 @@ bool MachineRegisterInfo::hasOneNonDBGUse(unsigned RegNo) const {
return ++UI == use_nodbg_end();
}
/// clearKillFlags - Iterate over all the uses of the given register and
/// clear the kill flag from the MachineOperand. This function is used by
/// optimization passes which extend register lifetimes and need only
/// preserve conservative kill flag information.
void MachineRegisterInfo::clearKillFlags(unsigned Reg) const {
for (use_iterator UI = use_begin(Reg), UE = use_end(); UI != UE; ++UI)
UI.getOperand().setIsKill(false);
}
bool MachineRegisterInfo::isLiveIn(unsigned Reg) const {
for (livein_iterator I = livein_begin(), E = livein_end(); I != E; ++I)
if (I->first == Reg || I->second == Reg)