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Handle register masks in LiveVariables. 

A register mask operand kills any live physreg that isn't preserved.
Unlike an implicit-def operand, the clobbered physregs are never live
afterwards.

This means LiveVariables has to track a much smaller number of live
physregs, and it should spend much less time in addRegisterDead().

llvm-svn: 148609
This commit is contained in:
Jakob Stoklund Olesen 2012-01-21 00:58:53 +00:00
parent 1630c15b0f
commit 8e3bb315d8
2 changed files with 33 additions and 0 deletions
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3
llvm/include/llvm/CodeGen/LiveVariables.h
View File

@ -160,6 +160,9 @@ private: // Intermediate data structures
/// the last use of the whole register.
bool HandlePhysRegKill(unsigned Reg, MachineInstr *MI);
/// HandleRegMask - Call HandlePhysRegKill for all registers clobbered by Mask.
void HandleRegMask(const MachineOperand&);
void HandlePhysRegUse(unsigned Reg, MachineInstr *MI);
void HandlePhysRegDef(unsigned Reg, MachineInstr *MI,
SmallVector<unsigned, 4> &Defs);

30
llvm/lib/CodeGen/LiveVariables.cpp
View File

@ -417,6 +417,27 @@ bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
return true;
}
void LiveVariables::HandleRegMask(const MachineOperand &MO) {
// Call HandlePhysRegKill() for all live registers clobbered by Mask.
// Clobbered registers are always dead, sp there is no need to use
// HandlePhysRegDef().
for (unsigned Reg = 1, NumRegs = TRI->getNumRegs(); Reg != NumRegs; ++Reg) {
// Skip dead regs.
if (!PhysRegDef[Reg] && !PhysRegUse[Reg])
continue;
// Skip mask-preserved regs.
if (!MO.clobbersPhysReg(Reg));
continue;
// Kill the largest clobbered super-register.
// This avoids needless implicit operands.
unsigned Super = Reg;
for (const unsigned *SR = TRI->getSuperRegisters(Reg); *SR; ++SR)
if ((PhysRegDef[*SR] || PhysRegUse[*SR]) && MO.clobbersPhysReg(*SR))
Super = *SR;
HandlePhysRegKill(Super, 0);
}
}
void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI,
SmallVector<unsigned, 4> &Defs) {
// What parts of the register are previously defined?
@ -534,8 +555,13 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
// Clear kill and dead markers. LV will recompute them.
SmallVector<unsigned, 4> UseRegs;
SmallVector<unsigned, 4> DefRegs;
SmallVector<unsigned, 1> RegMasks;
for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isRegMask()) {
RegMasks.push_back(i);
continue;
}
if (!MO.isReg() || MO.getReg() == 0)
continue;
unsigned MOReg = MO.getReg();
@ -557,6 +583,10 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
HandlePhysRegUse(MOReg, MI);
}
// Process all masked registers. (Call clobbers).
for (unsigned i = 0, e = RegMasks.size(); i != e; ++i)
HandleRegMask(MI->getOperand(RegMasks[i]));
// Process all defs.
for (unsigned i = 0, e = DefRegs.size(); i != e; ++i) {
unsigned MOReg = DefRegs[i];