-// ************************** //
-// Reuse Info Implementation //
-// ************************** //
-
-/// 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 ReuseInfo::GetRegForReload(unsigned PhysReg, MachineInstr *MI,
- AvailableSpills &Spills,
- std::vector<MachineInstr*> &MaybeDeadStores,
- SmallSet<unsigned, 8> &Rejected,
- BitVector &RegKills,
- std::vector<MachineOperand*> &KillOps,
- VirtRegMap &VRM) {
- const TargetInstrInfo* TII = MI->getParent()->getParent()->getTarget()
- .getInstrInfo();
-
- 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 TargetRegisterInfo *TRI = Spills.getRegInfo();
- if (TRI->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()->getRegInfo().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);
-
- MachineBasicBlock::iterator MII = MI;
- if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) {
- ReMaterialize(*MBB, MII, NewPhysReg, NewOp.VirtReg, TII, TRI,VRM);
- } else {
- TII->loadRegFromStackSlot(*MBB, MII, NewPhysReg,
- NewOp.StackSlotOrReMat, AliasRC);
- MachineInstr *LoadMI = prior(MII);
- VRM.addSpillSlotUse(NewOp.StackSlotOrReMat, LoadMI);
- // Any stores to this stack slot are not dead anymore.
- MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL;
- ++NumLoads;
- }
- Spills.ClobberPhysReg(NewPhysReg);
- Spills.ClobberPhysReg(NewOp.PhysRegReused);
-
- unsigned SubIdx = MI->getOperand(NewOp.Operand).getSubReg();
- unsigned RReg = SubIdx ? TRI->getSubReg(NewPhysReg, SubIdx) : NewPhysReg;
- MI->getOperand(NewOp.Operand).setReg(RReg);
-
- Spills.addAvailable(NewOp.StackSlotOrReMat, NewPhysReg);
- --MII;
- UpdateKills(*MII, RegKills, KillOps, TRI);
- DOUT << '\t' << *MII;
-
- DOUT << "Reuse undone!\n";
- --NumReused;
-
- // Finally, PhysReg is now available, go ahead and use it.
- return PhysReg;
- }
- }