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author | Evan Cheng <evan.cheng@apple.com> | 2007-03-06 10:01:25 +0000 |
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committer | Evan Cheng <evan.cheng@apple.com> | 2007-03-06 10:01:25 +0000 |
commit | b74a3e6fda768eb6160559e025f8b65c46db46d9 (patch) | |
tree | 99eb6473e9bac4c9fd502a72d0f76d11de274362 /lib/CodeGen/RegisterScavenging.cpp | |
parent | 1d9baccc9b4d664a944f82eef9f708125e3f1552 (diff) | |
download | external_llvm-b74a3e6fda768eb6160559e025f8b65c46db46d9.zip external_llvm-b74a3e6fda768eb6160559e025f8b65c46db46d9.tar.gz external_llvm-b74a3e6fda768eb6160559e025f8b65c46db46d9.tar.bz2 |
Register scavenger is now capable of scavenging. It spills a register whose use of furthest away to make it available.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34964 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/RegisterScavenging.cpp')
-rw-r--r-- | lib/CodeGen/RegisterScavenging.cpp | 92 |
1 files changed, 90 insertions, 2 deletions
diff --git a/lib/CodeGen/RegisterScavenging.cpp b/lib/CodeGen/RegisterScavenging.cpp index c5389d9..6197430 100644 --- a/lib/CodeGen/RegisterScavenging.cpp +++ b/lib/CodeGen/RegisterScavenging.cpp @@ -28,7 +28,8 @@ using namespace llvm; 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 @@ void RegScavenger::enterBasicBlock(MachineBasicBlock *mbb) { 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 @@ void RegScavenger::forward() { } 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 @@ void RegScavenger::forward() { 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 @@ unsigned RegScavenger::FindUnusedReg(const TargetRegisterClass *RegClass, 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; +} |