//===-- llvm/CodeGen/VirtRegMap.cpp - Virtual Register Map ----------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the VirtRegMap class. // // It also contains implementations of the the Spiller interface, which, given a // virtual register map and a machine function, eliminates all virtual // references by replacing them with physical register references - adding spill // code as necessary. // //===----------------------------------------------------------------------===// #define DEBUG_TYPE "spiller" #include "VirtRegMap.h" #include "llvm/Function.h" #include "llvm/CodeGen/MachineFrameInfo.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineRegisterInfo.h" #include "llvm/Target/TargetMachine.h" #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/Compiler.h" #include "llvm/ADT/BitVector.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/SmallSet.h" #include using namespace llvm; STATISTIC(NumSpills, "Number of register spills"); STATISTIC(NumReMats, "Number of re-materialization"); STATISTIC(NumDRM , "Number of re-materializable defs elided"); STATISTIC(NumStores, "Number of stores added"); STATISTIC(NumLoads , "Number of loads added"); STATISTIC(NumReused, "Number of values reused"); STATISTIC(NumDSE , "Number of dead stores elided"); STATISTIC(NumDCE , "Number of copies elided"); namespace { enum SpillerName { simple, local }; static cl::opt SpillerOpt("spiller", cl::desc("Spiller to use: (default: local)"), cl::Prefix, cl::values(clEnumVal(simple, " simple spiller"), clEnumVal(local, " local spiller"), clEnumValEnd), cl::init(local)); } //===----------------------------------------------------------------------===// // VirtRegMap implementation //===----------------------------------------------------------------------===// VirtRegMap::VirtRegMap(MachineFunction &mf) : TII(*mf.getTarget().getInstrInfo()), MF(mf), Virt2PhysMap(NO_PHYS_REG), Virt2StackSlotMap(NO_STACK_SLOT), Virt2ReMatIdMap(NO_STACK_SLOT), Virt2SplitMap(0), Virt2SplitKillMap(0), ReMatMap(NULL), ReMatId(MAX_STACK_SLOT+1) { grow(); } void VirtRegMap::grow() { unsigned LastVirtReg = MF.getRegInfo().getLastVirtReg(); Virt2PhysMap.grow(LastVirtReg); Virt2StackSlotMap.grow(LastVirtReg); Virt2ReMatIdMap.grow(LastVirtReg); Virt2SplitMap.grow(LastVirtReg); Virt2SplitKillMap.grow(LastVirtReg); ReMatMap.grow(LastVirtReg); } int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) { assert(MRegisterInfo::isVirtualRegister(virtReg)); assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT && "attempt to assign stack slot to already spilled register"); const TargetRegisterClass* RC = MF.getRegInfo().getRegClass(virtReg); int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(), RC->getAlignment()); Virt2StackSlotMap[virtReg] = frameIndex; ++NumSpills; return frameIndex; } void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) { assert(MRegisterInfo::isVirtualRegister(virtReg)); assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT && "attempt to assign stack slot to already spilled register"); assert((frameIndex >= 0 || (frameIndex >= MF.getFrameInfo()->getObjectIndexBegin())) && "illegal fixed frame index"); Virt2StackSlotMap[virtReg] = frameIndex; } int VirtRegMap::assignVirtReMatId(unsigned virtReg) { assert(MRegisterInfo::isVirtualRegister(virtReg)); assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT && "attempt to assign re-mat id to already spilled register"); Virt2ReMatIdMap[virtReg] = ReMatId; return ReMatId++; } void VirtRegMap::assignVirtReMatId(unsigned virtReg, int id) { assert(MRegisterInfo::isVirtualRegister(virtReg)); assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT && "attempt to assign re-mat id to already spilled register"); Virt2ReMatIdMap[virtReg] = id; } void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI, MachineInstr *NewMI, ModRef MRInfo) { // Move previous memory references folded to new instruction. MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI); for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI), E = MI2VirtMap.end(); I != E && I->first == OldMI; ) { MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second)); MI2VirtMap.erase(I++); } // add new memory reference MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo))); } void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *MI, ModRef MRInfo) { MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(MI); MI2VirtMap.insert(IP, std::make_pair(MI, std::make_pair(VirtReg, MRInfo))); } void VirtRegMap::print(std::ostream &OS) const { const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo(); OS << "********** REGISTER MAP **********\n"; for (unsigned i = MRegisterInfo::FirstVirtualRegister, e = MF.getRegInfo().getLastVirtReg(); i <= e; ++i) { if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG) OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n"; } for (unsigned i = MRegisterInfo::FirstVirtualRegister, e = MF.getRegInfo().getLastVirtReg(); i <= e; ++i) if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT) OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n"; OS << '\n'; } void VirtRegMap::dump() const { print(DOUT); } //===----------------------------------------------------------------------===// // Simple Spiller Implementation //===----------------------------------------------------------------------===// Spiller::~Spiller() {} namespace { struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller { bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM); }; } bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) { DOUT << "********** REWRITE MACHINE CODE **********\n"; DOUT << "********** Function: " << MF.getFunction()->getName() << '\n'; const TargetMachine &TM = MF.getTarget(); const TargetInstrInfo &TII = *TM.getInstrInfo(); // LoadedRegs - Keep track of which vregs are loaded, so that we only load // each vreg once (in the case where a spilled vreg is used by multiple // operands). This is always smaller than the number of operands to the // current machine instr, so it should be small. std::vector LoadedRegs; for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end(); MBBI != E; ++MBBI) { DOUT << MBBI->getBasicBlock()->getName() << ":\n"; MachineBasicBlock &MBB = *MBBI; for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end(); MII != E; ++MII) { MachineInstr &MI = *MII; for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { MachineOperand &MO = MI.getOperand(i); if (MO.isRegister() && MO.getReg()) if (MRegisterInfo::isVirtualRegister(MO.getReg())) { unsigned VirtReg = MO.getReg(); unsigned PhysReg = VRM.getPhys(VirtReg); if (!VRM.isAssignedReg(VirtReg)) { int StackSlot = VRM.getStackSlot(VirtReg); const TargetRegisterClass* RC = MF.getRegInfo().getRegClass(VirtReg); if (MO.isUse() && std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg) == LoadedRegs.end()) { TII.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC); LoadedRegs.push_back(VirtReg); ++NumLoads; DOUT << '\t' << *prior(MII); } if (MO.isDef()) { TII.storeRegToStackSlot(MBB, next(MII), PhysReg, true, StackSlot, RC); ++NumStores; } } MF.getRegInfo().setPhysRegUsed(PhysReg); MI.getOperand(i).setReg(PhysReg); } else { MF.getRegInfo().setPhysRegUsed(MO.getReg()); } } DOUT << '\t' << MI; LoadedRegs.clear(); } } return true; } //===----------------------------------------------------------------------===// // Local Spiller Implementation //===----------------------------------------------------------------------===// namespace { class AvailableSpills; /// LocalSpiller - This spiller does a simple pass over the machine basic /// block to attempt to keep spills in registers as much as possible for /// blocks that have low register pressure (the vreg may be spilled due to /// register pressure in other blocks). class VISIBILITY_HIDDEN LocalSpiller : public Spiller { MachineRegisterInfo *RegInfo; const MRegisterInfo *MRI; const TargetInstrInfo *TII; public: bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) { RegInfo = &MF.getRegInfo(); MRI = MF.getTarget().getRegisterInfo(); TII = MF.getTarget().getInstrInfo(); DOUT << "\n**** Local spiller rewriting function '" << MF.getFunction()->getName() << "':\n"; DOUT << "**** Machine Instrs (NOTE! Does not include spills and reloads!)" " ****\n"; DEBUG(MF.dump()); for (MachineFunction::iterator MBB = MF.begin(), E = MF.end(); MBB != E; ++MBB) RewriteMBB(*MBB, VRM); DOUT << "**** Post Machine Instrs ****\n"; DEBUG(MF.dump()); return true; } private: bool PrepForUnfoldOpti(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MII, std::vector &MaybeDeadStores, AvailableSpills &Spills, BitVector &RegKills, std::vector &KillOps, VirtRegMap &VRM); void SpillRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MII, int Idx, unsigned PhysReg, int StackSlot, const TargetRegisterClass *RC, bool isAvailable, MachineInstr *&LastStore, AvailableSpills &Spills, SmallSet &ReMatDefs, BitVector &RegKills, std::vector &KillOps, VirtRegMap &VRM); void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM); }; } /// AvailableSpills - As the local spiller is scanning and rewriting an MBB from /// top down, keep track of which spills slots or remat are available in each /// register. /// /// Note that not all physregs are created equal here. In particular, some /// physregs are reloads that we are allowed to clobber or ignore at any time. /// Other physregs are values that the register allocated program is using that /// we cannot CHANGE, but we can read if we like. We keep track of this on a /// per-stack-slot / remat id basis as the low bit in the value of the /// SpillSlotsAvailable entries. The predicate 'canClobberPhysReg()' checks /// this bit and addAvailable sets it if. namespace { class VISIBILITY_HIDDEN AvailableSpills { const MRegisterInfo *MRI; const TargetInstrInfo *TII; // SpillSlotsOrReMatsAvailable - This map keeps track of all of the spilled // or remat'ed virtual register values that are still available, due to being // loaded or stored to, but not invalidated yet. std::map SpillSlotsOrReMatsAvailable; // PhysRegsAvailable - This is the inverse of SpillSlotsOrReMatsAvailable, // indicating which stack slot values are currently held by a physreg. This // is used to invalidate entries in SpillSlotsOrReMatsAvailable when a // physreg is modified. std::multimap PhysRegsAvailable; void disallowClobberPhysRegOnly(unsigned PhysReg); void ClobberPhysRegOnly(unsigned PhysReg); public: AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii) : MRI(mri), TII(tii) { } const MRegisterInfo *getRegInfo() const { return MRI; } /// getSpillSlotOrReMatPhysReg - If the specified stack slot or remat is /// available in a physical register, return that PhysReg, otherwise /// return 0. unsigned getSpillSlotOrReMatPhysReg(int Slot) const { std::map::const_iterator I = SpillSlotsOrReMatsAvailable.find(Slot); if (I != SpillSlotsOrReMatsAvailable.end()) { return I->second >> 1; // Remove the CanClobber bit. } return 0; } /// addAvailable - Mark that the specified stack slot / remat is available in /// the specified physreg. If CanClobber is true, the physreg can be modified /// at any time without changing the semantics of the program. void addAvailable(int SlotOrReMat, MachineInstr *MI, unsigned Reg, bool CanClobber = true) { // If this stack slot is thought to be available in some other physreg, // remove its record. ModifyStackSlotOrReMat(SlotOrReMat); PhysRegsAvailable.insert(std::make_pair(Reg, SlotOrReMat)); SpillSlotsOrReMatsAvailable[SlotOrReMat]= (Reg << 1) | (unsigned)CanClobber; if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT) DOUT << "Remembering RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1; else DOUT << "Remembering SS#" << SlotOrReMat; DOUT << " in physreg " << MRI->getName(Reg) << "\n"; } /// canClobberPhysReg - Return true if the spiller is allowed to change the /// value of the specified stackslot register if it desires. The specified /// stack slot must be available in a physreg for this query to make sense. bool canClobberPhysReg(int SlotOrReMat) const { assert(SpillSlotsOrReMatsAvailable.count(SlotOrReMat) && "Value not available!"); return SpillSlotsOrReMatsAvailable.find(SlotOrReMat)->second & 1; } /// disallowClobberPhysReg - Unset the CanClobber bit of the specified /// stackslot register. The register is still available but is no longer /// allowed to be modifed. void disallowClobberPhysReg(unsigned PhysReg); /// ClobberPhysReg - This is called when the specified physreg changes /// value. We use this to invalidate any info about stuff that lives in /// it and any of its aliases. void ClobberPhysReg(unsigned PhysReg); /// ModifyStackSlotOrReMat - This method is called when the value in a stack /// slot changes. This removes information about which register the previous /// value for this slot lives in (as the previous value is dead now). void ModifyStackSlotOrReMat(int SlotOrReMat); }; } /// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified /// stackslot register. The register is still available but is no longer /// allowed to be modifed. void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) { std::multimap::iterator I = PhysRegsAvailable.lower_bound(PhysReg); while (I != PhysRegsAvailable.end() && I->first == PhysReg) { int SlotOrReMat = I->second; I++; assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg && "Bidirectional map mismatch!"); SpillSlotsOrReMatsAvailable[SlotOrReMat] &= ~1; DOUT << "PhysReg " << MRI->getName(PhysReg) << " copied, it is available for use but can no longer be modified\n"; } } /// disallowClobberPhysReg - Unset the CanClobber bit of the specified /// stackslot register and its aliases. The register and its aliases may /// still available but is no longer allowed to be modifed. void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) { for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS) disallowClobberPhysRegOnly(*AS); disallowClobberPhysRegOnly(PhysReg); } /// ClobberPhysRegOnly - This is called when the specified physreg changes /// value. We use this to invalidate any info about stuff we thing lives in it. void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) { std::multimap::iterator I = PhysRegsAvailable.lower_bound(PhysReg); while (I != PhysRegsAvailable.end() && I->first == PhysReg) { int SlotOrReMat = I->second; PhysRegsAvailable.erase(I++); assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg && "Bidirectional map mismatch!"); SpillSlotsOrReMatsAvailable.erase(SlotOrReMat); DOUT << "PhysReg " << MRI->getName(PhysReg) << " clobbered, invalidating "; if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT) DOUT << "RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1 << "\n"; else DOUT << "SS#" << SlotOrReMat << "\n"; } } /// ClobberPhysReg - This is called when the specified physreg changes /// value. We use this to invalidate any info about stuff we thing lives in /// it and any of its aliases. void AvailableSpills::ClobberPhysReg(unsigned PhysReg) { for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS) ClobberPhysRegOnly(*AS); ClobberPhysRegOnly(PhysReg); } /// ModifyStackSlotOrReMat - This method is called when the value in a stack /// slot changes. This removes information about which register the previous /// value for this slot lives in (as the previous value is dead now). void AvailableSpills::ModifyStackSlotOrReMat(int SlotOrReMat) { std::map::iterator It = SpillSlotsOrReMatsAvailable.find(SlotOrReMat); if (It == SpillSlotsOrReMatsAvailable.end()) return; unsigned Reg = It->second >> 1; SpillSlotsOrReMatsAvailable.erase(It); // This register may hold the value of multiple stack slots, only remove this // stack slot from the set of values the register contains. std::multimap::iterator I = PhysRegsAvailable.lower_bound(Reg); for (; ; ++I) { assert(I != PhysRegsAvailable.end() && I->first == Reg && "Map inverse broken!"); if (I->second == SlotOrReMat) break; } PhysRegsAvailable.erase(I); } /// InvalidateKills - MI is going to be deleted. If any of its operands are /// marked kill, then invalidate the information. static void InvalidateKills(MachineInstr &MI, BitVector &RegKills, std::vector &KillOps, SmallVector *KillRegs = NULL) { for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { MachineOperand &MO = MI.getOperand(i); if (!MO.isRegister() || !MO.isUse() || !MO.isKill()) continue; unsigned Reg = MO.getReg(); if (KillRegs) KillRegs->push_back(Reg); if (KillOps[Reg] == &MO) { RegKills.reset(Reg); KillOps[Reg] = NULL; } } } /// InvalidateKill - A MI that defines the specified register is being deleted, /// invalidate the register kill information. static void InvalidateKill(unsigned Reg, BitVector &RegKills, std::vector &KillOps) { if (RegKills[Reg]) { KillOps[Reg]->setIsKill(false); KillOps[Reg] = NULL; RegKills.reset(Reg); } } /// InvalidateRegDef - If the def operand of the specified def MI is now dead /// (since it's spill instruction is removed), mark it isDead. Also checks if /// the def MI has other definition operands that are not dead. Returns it by /// reference. static bool InvalidateRegDef(MachineBasicBlock::iterator I, MachineInstr &NewDef, unsigned Reg, bool &HasLiveDef) { // Due to remat, it's possible this reg isn't being reused. That is, // the def of this reg (by prev MI) is now dead. MachineInstr *DefMI = I; MachineOperand *DefOp = NULL; for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) { MachineOperand &MO = DefMI->getOperand(i); if (MO.isRegister() && MO.isDef()) { if (MO.getReg() == Reg) DefOp = &MO; else if (!MO.isDead()) HasLiveDef = true; } } if (!DefOp) return false; bool FoundUse = false, Done = false; MachineBasicBlock::iterator E = NewDef; ++I; ++E; for (; !Done && I != E; ++I) { MachineInstr *NMI = I; for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) { MachineOperand &MO = NMI->getOperand(j); if (!MO.isRegister() || MO.getReg() != Reg) continue; if (MO.isUse()) FoundUse = true; Done = true; // Stop after scanning all the operands of this MI. } } if (!FoundUse) { // Def is dead! DefOp->setIsDead(); return true; } return false; } /// UpdateKills - Track and update kill info. If a MI reads a register that is /// marked kill, then it must be due to register reuse. Transfer the kill info /// over. static void UpdateKills(MachineInstr &MI, BitVector &RegKills, std::vector &KillOps) { const TargetInstrDescriptor *TID = MI.getInstrDescriptor(); for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { MachineOperand &MO = MI.getOperand(i); if (!MO.isRegister() || !MO.isUse()) continue; unsigned Reg = MO.getReg(); if (Reg == 0) continue; if (RegKills[Reg]) { // That can't be right. Register is killed but not re-defined and it's // being reused. Let's fix that. KillOps[Reg]->setIsKill(false); KillOps[Reg] = NULL; RegKills.reset(Reg); if (i < TID->numOperands && TID->getOperandConstraint(i, TOI::TIED_TO) == -1) // Unless it's a two-address operand, this is the new kill. MO.setIsKill(); } if (MO.isKill()) { RegKills.set(Reg); KillOps[Reg] = &MO; } } for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { const MachineOperand &MO = MI.getOperand(i); if (!MO.isRegister() || !MO.isDef()) continue; unsigned Reg = MO.getReg(); RegKills.reset(Reg); KillOps[Reg] = NULL; } } // 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 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 &MaybeDeadStores, SmallSet &Rejected, BitVector &RegKills, std::vector &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 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()->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); if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) { MRI->reMaterialize(*MBB, MI, NewPhysReg, VRM.getReMaterializedMI(NewOp.VirtReg)); ++NumReMats; } else { TII->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 &MaybeDeadStores, BitVector &RegKills, std::vector &KillOps, VirtRegMap &VRM) { SmallSet Rejected; return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected, RegKills, KillOps, VRM); } }; } /// PrepForUnfoldOpti - Turn a store folding instruction into a load folding /// instruction. e.g. /// xorl %edi, %eax /// movl %eax, -32(%ebp) /// movl -36(%ebp), %eax /// orl %eax, -32(%ebp) /// ==> /// xorl %edi, %eax /// orl -36(%ebp), %eax /// mov %eax, -32(%ebp) /// This enables unfolding optimization for a subsequent instruction which will /// also eliminate the newly introduced store instruction. bool LocalSpiller::PrepForUnfoldOpti(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MII, std::vector &MaybeDeadStores, AvailableSpills &Spills, BitVector &RegKills, std::vector &KillOps, VirtRegMap &VRM) { MachineFunction &MF = *MBB.getParent(); MachineInstr &MI = *MII; unsigned UnfoldedOpc = 0; unsigned UnfoldPR = 0; unsigned UnfoldVR = 0; int FoldedSS = VirtRegMap::NO_STACK_SLOT; VirtRegMap::MI2VirtMapTy::const_iterator I, End; for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) { // Only transform a MI that folds a single register. if (UnfoldedOpc) return false; UnfoldVR = I->second.first; VirtRegMap::ModRef MR = I->second.second; if (VRM.isAssignedReg(UnfoldVR)) continue; // If this reference is not a use, any previous store is now dead. // Otherwise, the store to this stack slot is not dead anymore. FoldedSS = VRM.getStackSlot(UnfoldVR); MachineInstr* DeadStore = MaybeDeadStores[FoldedSS]; if (DeadStore && (MR & VirtRegMap::isModRef)) { unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(FoldedSS); if (!PhysReg || DeadStore->findRegisterUseOperandIdx(PhysReg, true) == -1) continue; UnfoldPR = PhysReg; UnfoldedOpc = MRI->getOpcodeAfterMemoryUnfold(MI.getOpcode(), false, true); } } if (!UnfoldedOpc) return false; for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { MachineOperand &MO = MI.getOperand(i); if (!MO.isRegister() || MO.getReg() == 0 || !MO.isUse()) continue; unsigned VirtReg = MO.getReg(); if (MRegisterInfo::isPhysicalRegister(VirtReg) || MO.getSubReg()) continue; if (VRM.isAssignedReg(VirtReg)) { unsigned PhysReg = VRM.getPhys(VirtReg); if (PhysReg && MRI->regsOverlap(PhysReg, UnfoldPR)) return false; } else if (VRM.isReMaterialized(VirtReg)) continue; int SS = VRM.getStackSlot(VirtReg); unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS); if (PhysReg) { if (MRI->regsOverlap(PhysReg, UnfoldPR)) return false; continue; } PhysReg = VRM.getPhys(VirtReg); if (!MRI->regsOverlap(PhysReg, UnfoldPR)) continue; // Ok, we'll need to reload the value into a register which makes // it impossible to perform the store unfolding optimization later. // Let's see if it is possible to fold the load if the store is // unfolded. This allows us to perform the store unfolding // optimization. SmallVector NewMIs; if (MRI->unfoldMemoryOperand(MF, &MI, UnfoldVR, false, false, NewMIs)) { assert(NewMIs.size() == 1); MachineInstr *NewMI = NewMIs.back(); NewMIs.clear(); int Idx = NewMI->findRegisterUseOperandIdx(VirtReg); assert(Idx != -1); SmallVector Ops; Ops.push_back(Idx); MachineInstr *FoldedMI = MRI->foldMemoryOperand(NewMI, Ops, SS); if (FoldedMI) { if (!VRM.hasPhys(UnfoldVR)) VRM.assignVirt2Phys(UnfoldVR, UnfoldPR); VRM.virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef); MII = MBB.insert(MII, FoldedMI); VRM.RemoveMachineInstrFromMaps(&MI); MBB.erase(&MI); return true; } delete NewMI; } } return false; } /// findSuperReg - Find the SubReg's super-register of given register class /// where its SubIdx sub-register is SubReg. static unsigned findSuperReg(const TargetRegisterClass *RC, unsigned SubReg, unsigned SubIdx, const MRegisterInfo *MRI) { for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end(); I != E; ++I) { unsigned Reg = *I; if (MRI->getSubReg(Reg, SubIdx) == SubReg) return Reg; } return 0; } /// 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 &ReMatDefs, BitVector &RegKills, std::vector &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 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; } /// rewriteMBB - Keep track of which spills are available even after the /// register allocator is done with them. If possible, avid 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 MaybeDeadStores; MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL); // ReMatDefs - These are rematerializable def MIs which are not deleted. SmallSet ReMatDefs; // Keep track of kill information. BitVector RegKills(MRI->getNumRegs()); std::vector KillOps; KillOps.resize(MRI->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 TargetInstrDescriptor *TID = MI.getInstrDescriptor(); // Insert restores here if asked to. if (VRM.isRestorePt(&MI)) { std::vector &RestoreRegs = VRM.getRestorePtRestores(&MI); for (unsigned i = 0, e = RestoreRegs.size(); i != e; ++i) { unsigned VirtReg = RestoreRegs[i]; if (!VRM.getPreSplitReg(VirtReg)) continue; // Split interval spilled again. unsigned Phys = VRM.getPhys(VirtReg); RegInfo->setPhysRegUsed(Phys); if (VRM.isReMaterialized(VirtReg)) { MRI->reMaterialize(MBB, &MI, Phys, VRM.getReMaterializedMI(VirtReg)); ++NumReMats; } else { const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg); TII->loadRegFromStackSlot(MBB, &MI, Phys, VRM.getStackSlot(VirtReg), RC); ++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 > &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); 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, MRI); // 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. RegInfo->setPhysRegUsed(VirtReg); continue; } assert(MRegisterInfo::isVirtualRegister(VirtReg) && "Not a virtual or a physical 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 ? 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 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 " << MRI->getName(PhysReg) << " for vreg" << VirtReg <<" instead of reloading into physreg " << MRI->getName(VRM.getPhys(VirtReg)) << "\n"; unsigned RReg = SubIdx ? 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); VRM.RemoveMachineInstrFromMaps(DeadStore); MBB.erase(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 = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg; MI.getOperand(i).setReg(RReg); ReusedOperands.markClobbered(RReg); ++NumReused; continue; } const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg); RegInfo->setPhysRegUsed(DesignatedReg); ReusedOperands.markClobbered(DesignatedReg); TII->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 = SubIdx ? MRI->getSubReg(DesignatedReg, SubIdx) : DesignatedReg; MI.getOperand(i).setReg(RReg); DOUT << '\t' << *prior(MII); ++NumReused; continue; } // if (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); RegInfo->setPhysRegUsed(PhysReg); ReusedOperands.markClobbered(PhysReg); if (DoReMat) { MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg)); ++NumReMats; } else { const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg); TII->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 = SubIdx ? 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 FoldedSS; for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) { unsigned VirtReg = I->second.first; VirtRegMap::ModRef MR = I->second.second; DOUT << "Folded vreg: " << VirtReg << " MR: " << MR; int SS = VRM.getStackSlot(VirtReg); if (SS == VirtRegMap::NO_STACK_SLOT) continue; 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 = RegInfo->getRegClass(VirtReg); TII->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; // Unset last kill since it's being reused. InvalidateKill(InReg, RegKills, KillOps); } VRM.RemoveMachineInstrFromMaps(&MI); MBB.erase(&MI); Erased = true; goto ProcessNextInst; } } else { unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS); SmallVector NewMIs; if (PhysReg && MRI->unfoldMemoryOperand(MF, &MI, PhysReg, false, false, NewMIs)) { MBB.insert(MII, NewMIs[0]); VRM.RemoveMachineInstrFromMaps(&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 = !(MR & VirtRegMap::isRef); MachineInstr *NewStore = NULL; if (MR & VirtRegMap::isModRef) { unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS); SmallVector NewMIs; // 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. if (PhysReg && !TII->isStoreToStackSlot(&MI, SS) && // Not profitable! 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.RemoveMachineInstrFromMaps(&MI); MBB.erase(&MI); Erased = true; --NextMII; --NextMII; // backtrack to the unfolded instruction. BackTracked = true; isDead = true; } } 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.RemoveMachineInstrFromMaps(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; } } // If the spill slot value is available, and this is a new definition of // the value, the value is not available anymore. if (MR & VirtRegMap::isMod) { // Notice that the value in this stack slot has been modified. Spills.ModifyStackSlotOrReMat(SS); // If this is *just* a mod of the value, check to see if this is just a // store to the spill slot (i.e. the spill got merged into the copy). If // so, realize that the vreg is available now, and add the store to the // MaybeDeadStore info. int StackSlot; if (!(MR & VirtRegMap::isRef)) { if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) { assert(MRegisterInfo::isPhysicalRegister(SrcReg) && "Src hasn't been allocated yet?"); // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark // this as a potentially dead store in case there is a subsequent // store into the stack slot without a read from it. MaybeDeadStores[StackSlot] = &MI; // If the stack slot value was previously available in some other // register, change it now. Otherwise, make the register available, // in PhysReg. Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/); } } } } // Process all of the spilled defs. for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { MachineOperand &MO = MI.getOperand(i); if (!(MO.isRegister() && MO.getReg() && MO.isDef())) continue; unsigned VirtReg = MO.getReg(); if (!MRegisterInfo::isVirtualRegister(VirtReg)) { // Check to see if this is a noop copy. If so, eliminate the // instruction before considering the dest reg to be changed. unsigned Src, Dst; if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) { ++NumDCE; DOUT << "Removing now-noop copy: " << MI; MBB.erase(&MI); Erased = true; VRM.RemoveMachineInstrFromMaps(&MI); Spills.disallowClobberPhysReg(VirtReg); goto ProcessNextInst; } // If it's not a no-op copy, it clobbers the value in the destreg. Spills.ClobberPhysReg(VirtReg); ReusedOperands.markClobbered(VirtReg); // Check to see if this instruction is a load from a stack slot into // a register. If so, this provides the stack slot value in the reg. int FrameIdx; if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) { assert(DestReg == VirtReg && "Unknown load situation!"); // If it is a folded reference, then it's not safe to clobber. bool Folded = FoldedSS.count(FrameIdx); // Otherwise, if it wasn't available, remember that it is now! Spills.addAvailable(FrameIdx, &MI, DestReg, !Folded); goto ProcessNextInst; } continue; } unsigned SubIdx = MO.getSubReg(); bool DoReMat = VRM.isReMaterialized(VirtReg); if (DoReMat) ReMatDefs.insert(&MI); // The only vregs left are stack slot definitions. int StackSlot = VRM.getStackSlot(VirtReg); const TargetRegisterClass *RC = RegInfo->getRegClass(VirtReg); // If this def is part of a two-address operand, make sure to execute // the store from the correct physical register. unsigned PhysReg; int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i); if (TiedOp != -1) { PhysReg = MI.getOperand(TiedOp).getReg(); if (SubIdx) { unsigned SuperReg = findSuperReg(RC, PhysReg, SubIdx, MRI); assert(SuperReg && MRI->getSubReg(SuperReg, SubIdx) == PhysReg && "Can't find corresponding super-register!"); PhysReg = SuperReg; } } else { PhysReg = VRM.getPhys(VirtReg); if (ReusedOperands.isClobbered(PhysReg)) { // Another def has taken the assigned physreg. It must have been a // use&def which got it due to reuse. Undo the reuse! PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI, Spills, MaybeDeadStores, RegKills, KillOps, VRM); } } RegInfo->setPhysRegUsed(PhysReg); unsigned RReg = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg; ReusedOperands.markClobbered(RReg); MI.getOperand(i).setReg(RReg); if (!MO.isDead()) { MachineInstr *&LastStore = MaybeDeadStores[StackSlot]; SpillRegToStackSlot(MBB, MII, -1, PhysReg, StackSlot, RC, true, LastStore, Spills, ReMatDefs, RegKills, KillOps, VRM); NextMII = next(MII); // Check to see if this is a noop copy. If so, eliminate the // instruction before considering the dest reg to be changed. { unsigned Src, Dst; if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) { ++NumDCE; DOUT << "Removing now-noop copy: " << MI; MBB.erase(&MI); Erased = true; VRM.RemoveMachineInstrFromMaps(&MI); UpdateKills(*LastStore, RegKills, KillOps); goto ProcessNextInst; } } } } ProcessNextInst: if (!Erased && !BackTracked) { for (MachineBasicBlock::iterator II = MI; II != NextMII; ++II) UpdateKills(*II, RegKills, KillOps); } MII = NextMII; } } llvm::Spiller* llvm::createSpiller() { switch (SpillerOpt) { default: assert(0 && "Unreachable!"); case local: return new LocalSpiller(); case simple: return new SimpleSpiller(); } }