+/// SpillRegToStackSlot - Spill a register to a specified stack slot. Check if
+/// the last store to the same slot is now dead. If so, remove the last store.
+void LocalSpiller::SpillRegToStackSlot(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator &MII,
+ int Idx, unsigned PhysReg, int StackSlot,
+ const TargetRegisterClass *RC,
+ bool isAvailable, MachineInstr *&LastStore,
+ AvailableSpills &Spills,
+ SmallSet<MachineInstr*, 4> &ReMatDefs,
+ BitVector &RegKills,
+ std::vector<MachineOperand*> &KillOps,
+ VirtRegMap &VRM) {
+ TII->storeRegToStackSlot(MBB, next(MII), PhysReg, true, StackSlot, RC);
+ DOUT << "Store:\t" << *next(MII);
+
+ // If there is a dead store to this stack slot, nuke it now.
+ if (LastStore) {
+ DOUT << "Removed dead store:\t" << *LastStore;
+ ++NumDSE;
+ SmallVector<unsigned, 2> KillRegs;
+ InvalidateKills(*LastStore, RegKills, KillOps, &KillRegs);
+ MachineBasicBlock::iterator PrevMII = LastStore;
+ bool CheckDef = PrevMII != MBB.begin();
+ if (CheckDef)
+ --PrevMII;
+ MBB.erase(LastStore);
+ VRM.RemoveMachineInstrFromMaps(LastStore);
+ if (CheckDef) {
+ // Look at defs of killed registers on the store. Mark the defs
+ // as dead since the store has been deleted and they aren't
+ // being reused.
+ for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
+ bool HasOtherDef = false;
+ if (InvalidateRegDef(PrevMII, *MII, KillRegs[j], HasOtherDef)) {
+ MachineInstr *DeadDef = PrevMII;
+ if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
+ // FIXME: This assumes a remat def does not have side
+ // effects.
+ MBB.erase(DeadDef);
+ VRM.RemoveMachineInstrFromMaps(DeadDef);
+ ++NumDRM;
+ }
+ }
+ }
+ }
+ }
+
+ LastStore = next(MII);
+
+ // If the stack slot value was previously available in some other
+ // register, change it now. Otherwise, make the register available,
+ // in PhysReg.
+ Spills.ModifyStackSlotOrReMat(StackSlot);
+ Spills.ClobberPhysReg(PhysReg);
+ Spills.addAvailable(StackSlot, LastStore, PhysReg, isAvailable);
+ ++NumStores;
+}
+