- MachineFunction &MF = *MBB.getParent();
-
- // Spills - Keep track of which spilled values are available in physregs so
- // that we can choose to reuse the physregs instead of emitting reloads.
- AvailableSpills Spills(TRI, TII);
-
- // MaybeDeadStores - When we need to write a value back into a stack slot,
- // keep track of the inserted store. If the stack slot value is never read
- // (because the value was used from some available register, for example), and
- // subsequently stored to, the original store is dead. This map keeps track
- // of inserted stores that are not used. If we see a subsequent store to the
- // same stack slot, the original store is deleted.
- std::vector<MachineInstr*> MaybeDeadStores;
- MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL);
-
- // ReMatDefs - These are rematerializable def MIs which are not deleted.
- SmallSet<MachineInstr*, 4> ReMatDefs;
-
- // Keep track of kill information.
- BitVector RegKills(TRI->getNumRegs());
- std::vector<MachineOperand*> KillOps;
- KillOps.resize(TRI->getNumRegs(), NULL);
-
- for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
- MII != E; ) {
- MachineBasicBlock::iterator NextMII = MII; ++NextMII;
-
- VirtRegMap::MI2VirtMapTy::const_iterator I, End;
- bool Erased = false;
- bool BackTracked = false;
- if (PrepForUnfoldOpti(MBB, MII,
- MaybeDeadStores, Spills, RegKills, KillOps, VRM))
- NextMII = next(MII);
-
- MachineInstr &MI = *MII;
- const TargetInstrDesc &TID = MI.getDesc();
-
- // Insert restores here if asked to.
- if (VRM.isRestorePt(&MI)) {
- std::vector<unsigned> &RestoreRegs = VRM.getRestorePtRestores(&MI);
- for (unsigned i = 0, e = RestoreRegs.size(); i != e; ++i) {
- unsigned VirtReg = RestoreRegs[e-i-1]; // Reverse order.
- if (!VRM.getPreSplitReg(VirtReg))
- continue; // Split interval spilled again.
- unsigned Phys = VRM.getPhys(VirtReg);
- RegInfo->setPhysRegUsed(Phys);
- if (VRM.isReMaterialized(VirtReg)) {
- ReMaterialize(MBB, MII, Phys, VirtReg, TRI, VRM);
- } else {
- const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
- int SS = VRM.getStackSlot(VirtReg);
- TII->loadRegFromStackSlot(MBB, &MI, Phys, SS, RC);
- MachineInstr *LoadMI = prior(MII);
- VRM.addSpillSlotUse(SS, LoadMI);
- ++NumLoads;
- }
- // This invalidates Phys.
- Spills.ClobberPhysReg(Phys);
- UpdateKills(*prior(MII), RegKills, KillOps);
- DOUT << '\t' << *prior(MII);
- }
- }
-
- // Insert spills here if asked to.
- if (VRM.isSpillPt(&MI)) {
- std::vector<std::pair<unsigned,bool> > &SpillRegs =
- VRM.getSpillPtSpills(&MI);
- for (unsigned i = 0, e = SpillRegs.size(); i != e; ++i) {
- unsigned VirtReg = SpillRegs[i].first;
- bool isKill = SpillRegs[i].second;
- if (!VRM.getPreSplitReg(VirtReg))
- continue; // Split interval spilled again.
- const TargetRegisterClass *RC = RegInfo->getRegClass(VirtReg);
- unsigned Phys = VRM.getPhys(VirtReg);
- int StackSlot = VRM.getStackSlot(VirtReg);
- TII->storeRegToStackSlot(MBB, next(MII), Phys, isKill, StackSlot, RC);
- MachineInstr *StoreMI = next(MII);
- VRM.addSpillSlotUse(StackSlot, StoreMI);
- DOUT << "Store:\t" << StoreMI;
- VRM.virtFolded(VirtReg, StoreMI, VirtRegMap::isMod);
- }
- NextMII = next(MII);
- }
-
- /// ReusedOperands - Keep track of operand reuse in case we need to undo
- /// reuse.
- ReuseInfo ReusedOperands(MI, TRI);
- SmallVector<unsigned, 4> VirtUseOps;
- for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
- MachineOperand &MO = MI.getOperand(i);
- if (!MO.isRegister() || MO.getReg() == 0)
- continue; // Ignore non-register operands.
-
- unsigned VirtReg = MO.getReg();
- if (TargetRegisterInfo::isPhysicalRegister(VirtReg)) {
- // Ignore physregs for spilling, but remember that it is used by this
- // function.
- RegInfo->setPhysRegUsed(VirtReg);
- continue;
- }
-
- // We want to process implicit virtual register uses first.
- if (MO.isImplicit())
- VirtUseOps.insert(VirtUseOps.begin(), i);
- else
- VirtUseOps.push_back(i);
- }
-
- // Process all of the spilled uses and all non spilled reg references.
- for (unsigned j = 0, e = VirtUseOps.size(); j != e; ++j) {
- unsigned i = VirtUseOps[j];
- MachineOperand &MO = MI.getOperand(i);
- unsigned VirtReg = MO.getReg();
- assert(TargetRegisterInfo::isVirtualRegister(VirtReg) &&
- "Not a virtual register?");
-
- unsigned SubIdx = MO.getSubReg();
- if (VRM.isAssignedReg(VirtReg)) {
- // This virtual register was assigned a physreg!
- unsigned Phys = VRM.getPhys(VirtReg);
- RegInfo->setPhysRegUsed(Phys);
- if (MO.isDef())
- ReusedOperands.markClobbered(Phys);
- unsigned RReg = SubIdx ? TRI->getSubReg(Phys, SubIdx) : Phys;
- MI.getOperand(i).setReg(RReg);
- continue;
- }
-
- // This virtual register is now known to be a spilled value.
- if (!MO.isUse())
- continue; // Handle defs in the loop below (handle use&def here though)
-
- bool DoReMat = VRM.isReMaterialized(VirtReg);
- int SSorRMId = DoReMat
- ? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
- int ReuseSlot = SSorRMId;
-
- // Check to see if this stack slot is available.
- unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
-
- // If this is a sub-register use, make sure the reuse register is in the
- // right register class. For example, for x86 not all of the 32-bit
- // registers have accessible sub-registers.
- // Similarly so for EXTRACT_SUBREG. Consider this:
- // EDI = op
- // MOV32_mr fi#1, EDI
- // ...
- // = EXTRACT_SUBREG fi#1
- // fi#1 is available in EDI, but it cannot be reused because it's not in
- // the right register file.
- if (PhysReg &&
- (SubIdx || MI.getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)) {
- const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
- if (!RC->contains(PhysReg))
- PhysReg = 0;
- }
-
- if (PhysReg) {
- // This spilled operand might be part of a two-address operand. If this
- // is the case, then changing it will necessarily require changing the
- // def part of the instruction as well. However, in some cases, we
- // aren't allowed to modify the reused register. If none of these cases
- // apply, reuse it.
- bool CanReuse = true;
- int ti = TID.getOperandConstraint(i, TOI::TIED_TO);
- if (ti != -1 &&
- MI.getOperand(ti).isRegister() &&
- MI.getOperand(ti).getReg() == VirtReg) {
- // Okay, we have a two address operand. We can reuse this physreg as
- // long as we are allowed to clobber the value and there isn't an
- // earlier def that has already clobbered the physreg.
- CanReuse = Spills.canClobberPhysReg(ReuseSlot) &&
- !ReusedOperands.isClobbered(PhysReg);
- }
-
- if (CanReuse) {
- // If this stack slot value is already available, reuse it!
- if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
- DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
- else
- DOUT << "Reusing SS#" << ReuseSlot;
- DOUT << " from physreg "
- << TRI->getName(PhysReg) << " for vreg"
- << VirtReg <<" instead of reloading into physreg "
- << TRI->getName(VRM.getPhys(VirtReg)) << "\n";
- unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
- MI.getOperand(i).setReg(RReg);
-
- // The only technical detail we have is that we don't know that
- // PhysReg won't be clobbered by a reloaded stack slot that occurs
- // later in the instruction. In particular, consider 'op V1, V2'.
- // If V1 is available in physreg R0, we would choose to reuse it
- // here, instead of reloading it into the register the allocator
- // indicated (say R1). However, V2 might have to be reloaded
- // later, and it might indicate that it needs to live in R0. When
- // this occurs, we need to have information available that
- // indicates it is safe to use R1 for the reload instead of R0.
- //
- // To further complicate matters, we might conflict with an alias,
- // or R0 and R1 might not be compatible with each other. In this
- // case, we actually insert a reload for V1 in R1, ensuring that
- // we can get at R0 or its alias.
- ReusedOperands.addReuse(i, ReuseSlot, PhysReg,
- VRM.getPhys(VirtReg), VirtReg);
- if (ti != -1)
- // Only mark it clobbered if this is a use&def operand.
- ReusedOperands.markClobbered(PhysReg);
- ++NumReused;
-
- if (MI.getOperand(i).isKill() &&
- ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) {
- // This was the last use and the spilled value is still available
- // for reuse. That means the spill was unnecessary!
- MachineInstr* DeadStore = MaybeDeadStores[ReuseSlot];
- if (DeadStore) {
- DOUT << "Removed dead store:\t" << *DeadStore;
- InvalidateKills(*DeadStore, RegKills, KillOps);
- VRM.RemoveMachineInstrFromMaps(DeadStore);
- MBB.erase(DeadStore);
- MaybeDeadStores[ReuseSlot] = NULL;
- ++NumDSE;
- }
- }