Changes in directory llvm/lib/CodeGen:
RegisterScavenging.cpp updated: 1.10 -> 1.11 --- Log message: Register scavenger is now capable of scavenging. It spills a register whose use of furthest away to make it available. --- Diffs of the changes: (+90 -2) RegisterScavenging.cpp | 92 +++++++++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 90 insertions(+), 2 deletions(-) Index: llvm/lib/CodeGen/RegisterScavenging.cpp diff -u llvm/lib/CodeGen/RegisterScavenging.cpp:1.10 llvm/lib/CodeGen/RegisterScavenging.cpp:1.11 --- llvm/lib/CodeGen/RegisterScavenging.cpp:1.10 Fri Mar 2 04:43:16 2007 +++ llvm/lib/CodeGen/RegisterScavenging.cpp Tue Mar 6 04:01:25 2007 @@ -28,7 +28,8 @@ void RegScavenger::enterBasicBlock(MachineBasicBlock *mbb) { const MachineFunction &MF = *mbb->getParent(); const TargetMachine &TM = MF.getTarget(); - const MRegisterInfo *RegInfo = TM.getRegisterInfo(); + TII = TM.getInstrInfo(); + RegInfo = TM.getRegisterInfo(); assert((NumPhysRegs == 0 || NumPhysRegs == RegInfo->getNumRegs()) && "Target changed?"); @@ -65,6 +66,19 @@ Tracking = false; } +void RegScavenger::restoreScavengedReg() { + if (!ScavengedReg) + return; + + RegInfo->loadRegFromStackSlot(*MBB, MBBI, ScavengedReg, + ScavengingFrameIndex, ScavengedRC); + MachineBasicBlock::iterator II = prior(MBBI); + RegInfo->eliminateFrameIndex(II, this); + setUsed(ScavengedReg); + ScavengedReg = 0; + ScavengedRC = NULL; +} + void RegScavenger::forward() { // Move ptr forward. if (!Tracking) { @@ -76,6 +90,12 @@ } MachineInstr *MI = MBBI; + + // Reaching a terminator instruction. Restore a scavenged register (which + // must be life out. + if (TII->isTerminatorInstr(MI->getOpcode())) + restoreScavengedReg(); + // Process uses first. BitVector ChangedRegs(NumPhysRegs); for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { @@ -85,7 +105,13 @@ unsigned Reg = MO.getReg(); if (Reg == 0) continue; - assert(isUsed(Reg)); + if (!isUsed(Reg)) { + // Register has been scavenged. Restore it! + if (Reg != ScavengedReg) + assert(false); + else + restoreScavengedReg(); + } if (MO.isKill() && !isReserved(Reg)) ChangedRegs.set(Reg); } @@ -191,3 +217,65 @@ int Reg = RegStatesCopy.find_first(); return (Reg == -1) ? 0 : Reg; } + +/// calcDistanceToUse - Calculate the distance to the first use of the +/// specified register. +static unsigned calcDistanceToUse(MachineBasicBlock *MBB, + MachineBasicBlock::iterator I, unsigned Reg) { + unsigned Dist = 0; + I = next(I); + while (I != MBB->end()) { + Dist++; + if (I->findRegisterUseOperand(Reg)) + return Dist; + I = next(I); + } + return Dist + 1; +} + +unsigned RegScavenger::scavengeRegister(const TargetRegisterClass *RC, + MachineBasicBlock::iterator I) { + assert(ScavengingFrameIndex >= 0 && + "Cannot scavenge a register without an emergency spill slot!"); + + // Mask off the registers which are not in the TargetRegisterClass. + BitVector Candidates(NumPhysRegs, false); + CreateRegClassMask(RC, Candidates); + Candidates ^= ReservedRegs; // Do not include reserved registers. + + // Exclude all the registers being used by the instruction. + for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { + MachineOperand &MO = I->getOperand(i); + if (MO.isReg()) + Candidates.reset(MO.getReg()); + } + + // Find the register whose use is furtherest aaway. + unsigned SReg = 0; + unsigned MaxDist = 0; + int Reg = Candidates.find_first(); + while (Reg != -1) { + unsigned Dist = calcDistanceToUse(MBB, I, Reg); + if (Dist >= MaxDist) { + MaxDist = Dist; + SReg = Reg; + } + Reg = Candidates.find_next(Reg); + } + + if (ScavengedReg != 0) { + // First restore previously scavenged register. + RegInfo->loadRegFromStackSlot(*MBB, I, ScavengedReg, + ScavengingFrameIndex, ScavengedRC); + MachineBasicBlock::iterator II = prior(I); + RegInfo->eliminateFrameIndex(II, this); + } + + RegInfo->storeRegToStackSlot(*MBB, I, SReg, ScavengingFrameIndex, RC); + MachineBasicBlock::iterator II = prior(I); + RegInfo->eliminateFrameIndex(II, this); + ScavengedReg = SReg; + ScavengedRC = RC; + + return SReg; +} _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits