-// ReusedOp - For each reused operand, we keep track of a bit of information, in
-// case we need to rollback upon processing a new operand. See comments below.
-namespace {
- struct ReusedOp {
- // The MachineInstr operand that reused an available value.
- unsigned Operand;
-
- // StackSlotOrReMat - The spill slot or remat id of the value being reused.
- unsigned StackSlotOrReMat;
-
- // PhysRegReused - The physical register the value was available in.
- unsigned PhysRegReused;
-
- // AssignedPhysReg - The physreg that was assigned for use by the reload.
- unsigned AssignedPhysReg;
-
- // VirtReg - The virtual register itself.
- unsigned VirtReg;
-
- ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
- unsigned vreg)
- : Operand(o), StackSlotOrReMat(ss), PhysRegReused(prr),
- AssignedPhysReg(apr), VirtReg(vreg) {}
- };
-
- /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
- /// is reused instead of reloaded.
- class VISIBILITY_HIDDEN ReuseInfo {
- MachineInstr &MI;
- std::vector<ReusedOp> Reuses;
- BitVector PhysRegsClobbered;
- public:
- ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
- PhysRegsClobbered.resize(mri->getNumRegs());
- }
-
- bool hasReuses() const {
- return !Reuses.empty();
- }
-
- /// addReuse - If we choose to reuse a virtual register that is already
- /// available instead of reloading it, remember that we did so.
- void addReuse(unsigned OpNo, unsigned StackSlotOrReMat,
- unsigned PhysRegReused, unsigned AssignedPhysReg,
- unsigned VirtReg) {
- // If the reload is to the assigned register anyway, no undo will be
- // required.
- if (PhysRegReused == AssignedPhysReg) return;
-
- // Otherwise, remember this.
- Reuses.push_back(ReusedOp(OpNo, StackSlotOrReMat, PhysRegReused,
- AssignedPhysReg, VirtReg));
- }
-
- void markClobbered(unsigned PhysReg) {
- PhysRegsClobbered.set(PhysReg);
- }
-
- bool isClobbered(unsigned PhysReg) const {
- return PhysRegsClobbered.test(PhysReg);
- }
-
- /// GetRegForReload - We are about to emit a reload into PhysReg. If there
- /// is some other operand that is using the specified register, either pick
- /// a new register to use, or evict the previous reload and use this reg.
- unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
- AvailableSpills &Spills,
- std::vector<MachineInstr*> &MaybeDeadStores,
- SmallSet<unsigned, 8> &Rejected,
- BitVector &RegKills,
- std::vector<MachineOperand*> &KillOps,
- VirtRegMap &VRM) {
- if (Reuses.empty()) return PhysReg; // This is most often empty.
-
- for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
- ReusedOp &Op = Reuses[ro];
- // If we find some other reuse that was supposed to use this register
- // exactly for its reload, we can change this reload to use ITS reload
- // register. That is, unless its reload register has already been
- // considered and subsequently rejected because it has also been reused
- // by another operand.
- if (Op.PhysRegReused == PhysReg &&
- Rejected.count(Op.AssignedPhysReg) == 0) {
- // Yup, use the reload register that we didn't use before.
- unsigned NewReg = Op.AssignedPhysReg;
- Rejected.insert(PhysReg);
- return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected,
- RegKills, KillOps, VRM);
- } else {
- // Otherwise, we might also have a problem if a previously reused
- // value aliases the new register. If so, codegen the previous reload
- // and use this one.
- unsigned PRRU = Op.PhysRegReused;
- const MRegisterInfo *MRI = Spills.getRegInfo();
- if (MRI->areAliases(PRRU, PhysReg)) {
- // Okay, we found out that an alias of a reused register
- // was used. This isn't good because it means we have
- // to undo a previous reuse.
- MachineBasicBlock *MBB = MI->getParent();
- const TargetRegisterClass *AliasRC =
- MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
-
- // Copy Op out of the vector and remove it, we're going to insert an
- // explicit load for it.
- ReusedOp NewOp = Op;
- Reuses.erase(Reuses.begin()+ro);
-
- // Ok, we're going to try to reload the assigned physreg into the
- // slot that we were supposed to in the first place. However, that
- // register could hold a reuse. Check to see if it conflicts or
- // would prefer us to use a different register.
- unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
- MI, Spills, MaybeDeadStores,
- Rejected, RegKills, KillOps, VRM);
-
- if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) {
- MRI->reMaterialize(*MBB, MI, NewPhysReg,
- VRM.getReMaterializedMI(NewOp.VirtReg));
- ++NumReMats;
- } else {
- MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg,
- NewOp.StackSlotOrReMat, AliasRC);
- // Any stores to this stack slot are not dead anymore.
- MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL;
- ++NumLoads;
- }
- Spills.ClobberPhysReg(NewPhysReg);
- Spills.ClobberPhysReg(NewOp.PhysRegReused);
-
- MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
-
- Spills.addAvailable(NewOp.StackSlotOrReMat, MI, NewPhysReg);
- MachineBasicBlock::iterator MII = MI;
- --MII;
- UpdateKills(*MII, RegKills, KillOps);
- DOUT << '\t' << *MII;
-
- DOUT << "Reuse undone!\n";
- --NumReused;
-
- // Finally, PhysReg is now available, go ahead and use it.
- return PhysReg;
- }
- }
- }
- return PhysReg;
- }
-
- /// GetRegForReload - Helper for the above GetRegForReload(). Add a
- /// 'Rejected' set to remember which registers have been considered and
- /// rejected for the reload. This avoids infinite looping in case like
- /// this:
- /// t1 := op t2, t3
- /// t2 <- assigned r0 for use by the reload but ended up reuse r1
- /// t3 <- assigned r1 for use by the reload but ended up reuse r0
- /// t1 <- desires r1
- /// sees r1 is taken by t2, tries t2's reload register r0
- /// sees r0 is taken by t3, tries t3's reload register r1
- /// sees r1 is taken by t2, tries t2's reload register r0 ...
- unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
- AvailableSpills &Spills,
- std::vector<MachineInstr*> &MaybeDeadStores,
- BitVector &RegKills,
- std::vector<MachineOperand*> &KillOps,
- VirtRegMap &VRM) {
- SmallSet<unsigned, 8> Rejected;
- return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected,
- RegKills, KillOps, VRM);
- }
- };
-}
-
-
-/// rewriteMBB - Keep track of which spills are available even after the
-/// register allocator is done with them. If possible, avoid reloading vregs.
-void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
- DOUT << MBB.getBasicBlock()->getName() << ":\n";
-
- 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(MRI, 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(MRI->getNumRegs());
- std::vector<MachineOperand*> KillOps;
- KillOps.resize(MRI->getNumRegs(), NULL);
-
- for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
- MII != E; ) {
- MachineInstr &MI = *MII;
- MachineBasicBlock::iterator NextMII = MII; ++NextMII;
- VirtRegMap::MI2VirtMapTy::const_iterator I, End;
-
- bool Erased = false;
- bool BackTracked = false;
-
- /// ReusedOperands - Keep track of operand reuse in case we need to undo
- /// reuse.
- ReuseInfo ReusedOperands(MI, MRI);
-
- // Loop over all of the implicit defs, clearing them from our available
- // sets.
- const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
- if (TID->ImplicitDefs) {
- const unsigned *ImpDef = TID->ImplicitDefs;
- for ( ; *ImpDef; ++ImpDef) {
- MF.setPhysRegUsed(*ImpDef);
- ReusedOperands.markClobbered(*ImpDef);
- Spills.ClobberPhysReg(*ImpDef);
- }
- }
-
- // Process all of the spilled uses and all non spilled reg references.
- 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 (MRegisterInfo::isPhysicalRegister(VirtReg)) {
- // Ignore physregs for spilling, but remember that it is used by this
- // function.
- MF.setPhysRegUsed(VirtReg);
- ReusedOperands.markClobbered(VirtReg);
- continue;
- }
-
- assert(MRegisterInfo::isVirtualRegister(VirtReg) &&
- "Not a virtual or a physical register?");
-
- unsigned SubIdx = 0;
- bool isSubReg = RegMap->isSubRegister(VirtReg);
- if (isSubReg) {
- SubIdx = RegMap->getSubRegisterIndex(VirtReg);
- VirtReg = RegMap->getSuperRegister(VirtReg);
- }
-
- if (VRM.isAssignedReg(VirtReg)) {
- // This virtual register was assigned a physreg!
- unsigned Phys = VRM.getPhys(VirtReg);
- MF.setPhysRegUsed(Phys);
- if (MO.isDef())
- ReusedOperands.markClobbered(Phys);
- unsigned RReg = isSubReg ? MRI->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 (!PhysReg && DoReMat) {
- // This use is rematerializable. But perhaps the value is available in
- // stack if the definition is not deleted. If so, check if we can
- // reuse the value.
- ReuseSlot = VRM.getStackSlot(VirtReg);
- if (ReuseSlot != VirtRegMap::NO_STACK_SLOT)
- PhysReg = Spills.getSpillSlotOrReMatPhysReg(ReuseSlot);
- }
-
- // 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 &&
- (isSubReg || MI.getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)) {
- const TargetRegisterClass* RC = RegMap->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 "
- << MRI->getName(PhysReg) << " for vreg"
- << VirtReg <<" instead of reloading into physreg "
- << MRI->getName(VRM.getPhys(VirtReg)) << "\n";
- unsigned RReg = isSubReg ? MRI->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);
- MBB.erase(DeadStore);
- VRM.RemoveFromFoldedVirtMap(DeadStore);
- MaybeDeadStores[ReuseSlot] = NULL;
- ++NumDSE;
- }
- }
- continue;
- } // CanReuse
-
- // Otherwise we have a situation where we have a two-address instruction
- // whose mod/ref operand needs to be reloaded. This reload is already
- // available in some register "PhysReg", but if we used PhysReg as the
- // operand to our 2-addr instruction, the instruction would modify
- // PhysReg. This isn't cool if something later uses PhysReg and expects
- // to get its initial value.
- //
- // To avoid this problem, and to avoid doing a load right after a store,
- // we emit a copy from PhysReg into the designated register for this
- // operand.
- unsigned DesignatedReg = VRM.getPhys(VirtReg);
- assert(DesignatedReg && "Must map virtreg to physreg!");
-
- // Note that, if we reused a register for a previous operand, the
- // register we want to reload into might not actually be
- // available. If this occurs, use the register indicated by the
- // reuser.
- if (ReusedOperands.hasReuses())
- DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
- Spills, MaybeDeadStores, RegKills, KillOps, VRM);
-
- // If the mapped designated register is actually the physreg we have
- // incoming, we don't need to inserted a dead copy.
- if (DesignatedReg == PhysReg) {
- // 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 " << MRI->getName(PhysReg) << " for vreg"
- << VirtReg
- << " instead of reloading into same physreg.\n";
- unsigned RReg = isSubReg ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
- MI.getOperand(i).setReg(RReg);
- ReusedOperands.markClobbered(PhysReg);
- ++NumReused;
- continue;
- }
-
- const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
- MF.setPhysRegUsed(DesignatedReg);
- ReusedOperands.markClobbered(DesignatedReg);
- MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC, RC);
-
- MachineInstr *CopyMI = prior(MII);
- UpdateKills(*CopyMI, RegKills, KillOps);
-
- // This invalidates DesignatedReg.
- Spills.ClobberPhysReg(DesignatedReg);
-
- Spills.addAvailable(ReuseSlot, &MI, DesignatedReg);
- unsigned RReg =
- isSubReg ? MRI->getSubReg(DesignatedReg, SubIdx) : DesignatedReg;
- MI.getOperand(i).setReg(RReg);
- DOUT << '\t' << *prior(MII);
- ++NumReused;
- continue;
- } // is (PhysReg)
-
- // Otherwise, reload it and remember that we have it.
- PhysReg = VRM.getPhys(VirtReg);
- assert(PhysReg && "Must map virtreg to physreg!");
-
- // Note that, if we reused a register for a previous operand, the
- // register we want to reload into might not actually be
- // available. If this occurs, use the register indicated by the
- // reuser.
- if (ReusedOperands.hasReuses())
- PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
- Spills, MaybeDeadStores, RegKills, KillOps, VRM);
-
- MF.setPhysRegUsed(PhysReg);
- ReusedOperands.markClobbered(PhysReg);
- if (DoReMat) {
- MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg));
- ++NumReMats;
- } else {
- const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
- MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, SSorRMId, RC);
- ++NumLoads;
- }
- // This invalidates PhysReg.
- Spills.ClobberPhysReg(PhysReg);
-
- // Any stores to this stack slot are not dead anymore.
- if (!DoReMat)
- MaybeDeadStores[SSorRMId] = NULL;
- Spills.addAvailable(SSorRMId, &MI, PhysReg);
- // Assumes this is the last use. IsKill will be unset if reg is reused
- // unless it's a two-address operand.
- if (TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
- MI.getOperand(i).setIsKill();
- unsigned RReg = isSubReg ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
- MI.getOperand(i).setReg(RReg);
- UpdateKills(*prior(MII), RegKills, KillOps);
- DOUT << '\t' << *prior(MII);
- }
-
- DOUT << '\t' << MI;
-
- // If we have folded references to memory operands, make sure we clear all
- // physical registers that may contain the value of the spilled virtual
- // register
- SmallSet<int, 1> FoldedSS;
- for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
- DOUT << "Folded vreg: " << I->second.first << " MR: "
- << I->second.second;
- unsigned VirtReg = I->second.first;
- VirtRegMap::ModRef MR = I->second.second;
- if (VRM.isAssignedReg(VirtReg)) {
- DOUT << ": No stack slot!\n";
- continue;
- }
- int SS = VRM.getStackSlot(VirtReg);
- FoldedSS.insert(SS);
- DOUT << " - StackSlot: " << SS << "\n";
-
- // If this folded instruction is just a use, check to see if it's a
- // straight load from the virt reg slot.
- if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
- int FrameIdx;
- unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx);
- if (DestReg && FrameIdx == SS) {
- // If this spill slot is available, turn it into a copy (or nothing)
- // instead of leaving it as a load!
- if (unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SS)) {
- DOUT << "Promoted Load To Copy: " << MI;
- if (DestReg != InReg) {
- const TargetRegisterClass *RC = RegMap->getRegClass(VirtReg);
- MRI->copyRegToReg(MBB, &MI, DestReg, InReg, RC, RC);
- // Revisit the copy so we make sure to notice the effects of the
- // operation on the destreg (either needing to RA it if it's
- // virtual or needing to clobber any values if it's physical).
- NextMII = &MI;
- --NextMII; // backtrack to the copy.
- BackTracked = true;
- } else
- DOUT << "Removing now-noop copy: " << MI;
-
- VRM.RemoveFromFoldedVirtMap(&MI);
- MBB.erase(&MI);
- Erased = true;
- goto ProcessNextInst;
- }
- } else {
- unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
- SmallVector<MachineInstr*, 4> NewMIs;
- if (PhysReg &&
- MRI->unfoldMemoryOperand(MF, &MI, PhysReg, false, false, NewMIs)) {
- MBB.insert(MII, NewMIs[0]);
- VRM.RemoveFromFoldedVirtMap(&MI);
- MBB.erase(&MI);
- Erased = true;
- --NextMII; // backtrack to the unfolded instruction.
- BackTracked = true;
- goto ProcessNextInst;
- }
- }
- }
-
- // If this reference is not a use, any previous store is now dead.
- // Otherwise, the store to this stack slot is not dead anymore.
- MachineInstr* DeadStore = MaybeDeadStores[SS];
- if (DeadStore) {
- bool isDead = true;
- MachineInstr *NewStore = NULL;
- if (MR & VirtRegMap::isRef) {
- unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
- SmallVector<MachineInstr*, 4> NewMIs;
- if (PhysReg &&
- DeadStore->findRegisterUseOperandIdx(PhysReg, true) != -1 &&
- MRI->unfoldMemoryOperand(MF, &MI, PhysReg, false, true, NewMIs)) {
- MBB.insert(MII, NewMIs[0]);
- NewStore = NewMIs[1];
- MBB.insert(MII, NewStore);
- VRM.RemoveFromFoldedVirtMap(&MI);
- MBB.erase(&MI);
- Erased = true;
- --NextMII;
- --NextMII; // backtrack to the unfolded instruction.
- BackTracked = true;
- } else
- isDead = false;
- }
-
- if (isDead) { // Previous store is dead.
- // If we get here, the store is dead, nuke it now.
- DOUT << "Removed dead store:\t" << *DeadStore;
- InvalidateKills(*DeadStore, RegKills, KillOps);
- VRM.RemoveFromFoldedVirtMap(DeadStore);
- MBB.erase(DeadStore);
- if (!NewStore)
- ++NumDSE;
- }
-
- MaybeDeadStores[SS] = NULL;
- if (NewStore) {
- // Treat this store as a spill merged into a copy. That makes the
- // stack slot value available.
- VRM.virtFolded(VirtReg, NewStore, VirtRegMap::isMod);
- goto ProcessNextInst;