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Add MachineRegisterInfo::constrainRegClass and use it in MachineCSE.

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This function is intended to be used when inserting a machine instruction that
trivially restricts the legal registers, like LEA requiring a GR32_NOSP
argument.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115875 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2010-10-06 23:54:39 +00:00
parent 893ab5d701
commit bf4699c561
3 changed files with 24 additions and 7 deletions
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8
include/llvm/CodeGen/MachineRegisterInfo.h
View File

@ -203,6 +203,14 @@ public:
///
void setRegClass(unsigned Reg, const TargetRegisterClass *RC);
/// constrainRegClass - Constrain the register class of the specified virtual
/// register to be a common subclass of RC and the current register class.
/// Return the new register class, or NULL if no such class exists.
/// This should only be used when the constraint is known to be trivial, like
/// GR32 -> GR32_NOSP. Beware of increasing register pressure.
const TargetRegisterClass *constrainRegClass(unsigned Reg,
const TargetRegisterClass *RC);
/// createVirtualRegister - Create and return a new virtual register in the
/// function with the specified register class.
///

9
lib/CodeGen/MachineCSE.cpp
View File

@ -120,17 +120,12 @@ bool MachineCSE::PerformTrivialCoalescing(MachineInstr *MI,
continue;
if (DefMI->getOperand(0).getSubReg() || DefMI->getOperand(1).getSubReg())
continue;
const TargetRegisterClass *SRC = MRI->getRegClass(SrcReg);
const TargetRegisterClass *RC = MRI->getRegClass(Reg);
const TargetRegisterClass *NewRC = getCommonSubClass(RC, SRC);
if (!NewRC)
if (!MRI->constrainRegClass(SrcReg, MRI->getRegClass(Reg)))
continue;
DEBUG(dbgs() << "Coalescing: " << *DefMI);
DEBUG(dbgs() << "*** to: " << *MI);
DEBUG(dbgs() << "*** to: " << *MI);
MO.setReg(SrcReg);
MRI->clearKillFlags(SrcReg);
if (NewRC != SRC)
MRI->setRegClass(SrcReg, NewRC);
DefMI->eraseFromParent();
++NumCoalesces;
Changed = true;

14
lib/CodeGen/MachineRegisterInfo.cpp
View File

@ -60,6 +60,20 @@ MachineRegisterInfo::setRegClass(unsigned Reg, const TargetRegisterClass *RC) {
RegClass2VRegMap[RC->getID()].push_back(VR);
}
const TargetRegisterClass *
MachineRegisterInfo::constrainRegClass(unsigned Reg,
const TargetRegisterClass *RC) {
const TargetRegisterClass *OldRC = getRegClass(Reg);
if (OldRC == RC)
return RC;
const TargetRegisterClass *NewRC = getCommonSubClass(OldRC, RC);
if (!NewRC)
return 0;
if (NewRC != OldRC)
setRegClass(Reg, NewRC);
return NewRC;
}
/// createVirtualRegister - Create and return a new virtual register in the
/// function with the specified register class.
///