X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FVirtRegMap.cpp;h=3fb84bdd8f74c278c436c60edd13f241a8f47335;hb=2d87734a8ffad5933edbbc15a3b643df1e8a767e;hp=144780129dc1beaf9ad9128793c457407ad6d5bc;hpb=47cb7173ea48691343b1046a0228a87c03b4167e;p=oota-llvm.git diff --git a/lib/CodeGen/VirtRegMap.cpp b/lib/CodeGen/VirtRegMap.cpp index 144780129dc..3fb84bdd8f7 100644 --- a/lib/CodeGen/VirtRegMap.cpp +++ b/lib/CodeGen/VirtRegMap.cpp @@ -26,23 +26,26 @@ #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 -#include using namespace llvm; -namespace { - Statistic<> NumSpills("spiller", "Number of register spills"); - Statistic<> NumStores("spiller", "Number of stores added"); - Statistic<> NumLoads ("spiller", "Number of loads added"); - Statistic<> NumReused("spiller", "Number of values reused"); - Statistic<> NumDSE ("spiller", "Number of dead stores elided"); - Statistic<> NumDCE ("spiller", "Number of copies elided"); +STATISTIC(NumSpills, "Number of register spills"); +STATISTIC(NumReMats, "Number of re-materialization"); +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 }; - cl::opt + static cl::opt SpillerOpt("spiller", cl::desc("Spiller to use: (default: local)"), cl::Prefix, @@ -56,6 +59,13 @@ namespace { // VirtRegMap implementation //===----------------------------------------------------------------------===// +VirtRegMap::VirtRegMap(MachineFunction &mf) + : TII(*mf.getTarget().getInstrInfo()), MF(mf), + Virt2PhysMap(NO_PHYS_REG), Virt2StackSlotMap(NO_STACK_SLOT), + ReMatId(MAX_STACK_SLOT+1) { + grow(); +} + void VirtRegMap::grow() { Virt2PhysMap.grow(MF.getSSARegMap()->getLastVirtReg()); Virt2StackSlotMap.grow(MF.getSSARegMap()->getLastVirtReg()); @@ -77,9 +87,27 @@ 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(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT && + "attempt to assign re-mat id to already spilled register"); + const MachineInstr *DefMI = getReMaterializedMI(virtReg); + int FrameIdx; + if (TII.isLoadFromStackSlot((MachineInstr*)DefMI, FrameIdx)) { + // Load from stack slot is re-materialize as reload from the stack slot! + Virt2StackSlotMap[virtReg] = FrameIdx; + return FrameIdx; + } + Virt2StackSlotMap[virtReg] = ReMatId; + return ReMatId++; +} + void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI, unsigned OpNo, MachineInstr *NewMI) { // Move previous memory references folded to new instruction. @@ -91,11 +119,15 @@ void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI, } ModRef MRInfo; - if (!OldMI->getOperand(OpNo).isDef()) { - assert(OldMI->getOperand(OpNo).isUse() && "Operand is not use or def?"); - MRInfo = isRef; + const TargetInstrDescriptor *TID = OldMI->getInstrDescriptor(); + if (TID->getOperandConstraint(OpNo, TOI::TIED_TO) != -1 || + TID->findTiedToSrcOperand(OpNo) != -1) { + // Folded a two-address operand. + MRInfo = isModRef; + } else if (OldMI->getOperand(OpNo).isDef()) { + MRInfo = isMod; } else { - MRInfo = OldMI->getOperand(OpNo).isUse() ? isModRef : isMod; + MRInfo = isRef; } // add new memory reference @@ -120,7 +152,9 @@ void VirtRegMap::print(std::ostream &OS) const { OS << '\n'; } -void VirtRegMap::dump() const { print(std::cerr); } +void VirtRegMap::dump() const { + print(DOUT); +} //===----------------------------------------------------------------------===// @@ -130,16 +164,14 @@ void VirtRegMap::dump() const { print(std::cerr); } Spiller::~Spiller() {} namespace { - struct SimpleSpiller : public Spiller { - bool runOnMachineFunction(MachineFunction& mf, const VirtRegMap &VRM); + struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller { + bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM); }; } -bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, - const VirtRegMap &VRM) { - DEBUG(std::cerr << "********** REWRITE MACHINE CODE **********\n"); - DEBUG(std::cerr << "********** Function: " - << MF.getFunction()->getName() << '\n'); +bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) { + DOUT << "********** REWRITE MACHINE CODE **********\n"; + DOUT << "********** Function: " << MF.getFunction()->getName() << '\n'; const TargetMachine &TM = MF.getTarget(); const MRegisterInfo &MRI = *TM.getRegisterInfo(); bool *PhysRegsUsed = MF.getUsedPhysregs(); @@ -152,7 +184,7 @@ bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end(); MBBI != E; ++MBBI) { - DEBUG(std::cerr << MBBI->getBasicBlock()->getName() << ":\n"); + DOUT << MBBI->getBasicBlock()->getName() << ":\n"; MachineBasicBlock &MBB = *MBBI; for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end(); MII != E; ++MII) { @@ -174,7 +206,7 @@ bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC); LoadedRegs.push_back(VirtReg); ++NumLoads; - DEBUG(std::cerr << '\t' << *prior(MII)); + DOUT << '\t' << *prior(MII); } if (MO.isDef()) { @@ -183,13 +215,13 @@ bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, } } PhysRegsUsed[PhysReg] = true; - MI.SetMachineOperandReg(i, PhysReg); + MI.getOperand(i).setReg(PhysReg); } else { PhysRegsUsed[MO.getReg()] = true; } } - DEBUG(std::cerr << '\t' << MI); + DOUT << '\t' << MI; LoadedRegs.clear(); } } @@ -205,29 +237,27 @@ namespace { /// 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 LocalSpiller : public Spiller { + class VISIBILITY_HIDDEN LocalSpiller : public Spiller { const MRegisterInfo *MRI; const TargetInstrInfo *TII; public: - bool runOnMachineFunction(MachineFunction &MF, const VirtRegMap &VRM) { + bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) { MRI = MF.getTarget().getRegisterInfo(); TII = MF.getTarget().getInstrInfo(); - DEBUG(std::cerr << "\n**** Local spiller rewriting function '" - << MF.getFunction()->getName() << "':\n"); + DOUT << "\n**** Local spiller rewriting function '" + << MF.getFunction()->getName() << "':\n"; + std::vector ReMatedMIs; for (MachineFunction::iterator MBB = MF.begin(), E = MF.end(); MBB != E; ++MBB) - RewriteMBB(*MBB, VRM); + RewriteMBB(*MBB, VRM, ReMatedMIs); + for (unsigned i = 0, e = ReMatedMIs.size(); i != e; ++i) + delete ReMatedMIs[i]; return true; } private: - void RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM); - void ClobberPhysReg(unsigned PR, std::map &SpillSlots, - std::multimap &PhysRegs); - void ClobberPhysRegOnly(unsigned PR, std::map &SpillSlots, - std::multimap &PhysRegs); - void ModifyStackSlot(int Slot, std::map &SpillSlots, - std::multimap &PhysRegs); + void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM, + std::vector &ReMatedMIs); }; } @@ -241,60 +271,119 @@ namespace { /// per-stack-slot basis as the low bit in the value of the SpillSlotsAvailable /// entries. The predicate 'canClobberPhysReg()' checks this bit and /// addAvailable sets it if. -class AvailableSpills { +namespace { +class VISIBILITY_HIDDEN AvailableSpills { const MRegisterInfo *MRI; const TargetInstrInfo *TII; // SpillSlotsAvailable - This map keeps track of all of the spilled virtual // register values that are still available, due to being loaded or stored to, - // but not invalidated yet. - std::map SpillSlotsAvailable; + // but not invalidated yet. It also tracks the instructions that defined + // or used the register. + typedef std::pair > SSInfo; + std::map SpillSlotsAvailable; // PhysRegsAvailable - This is the inverse of SpillSlotsAvailable, indicating // which stack slot values are currently held by a physreg. This is used to // invalidate entries in SpillSlotsAvailable 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; } + /// getSpillSlotPhysReg - If the specified stack slot is available in a - /// physical register, return that PhysReg, otherwise return 0. - unsigned getSpillSlotPhysReg(int Slot) const { - std::map::const_iterator I = SpillSlotsAvailable.find(Slot); - if (I != SpillSlotsAvailable.end()) - return I->second >> 1; // Remove the CanClobber bit. + /// physical register, return that PhysReg, otherwise return 0. It also + /// returns by reference the instruction that either defines or last uses + /// the register. + unsigned getSpillSlotPhysReg(int Slot, MachineInstr *&SSMI) const { + std::map::const_iterator I = SpillSlotsAvailable.find(Slot); + if (I != SpillSlotsAvailable.end()) { + if (!I->second.second.empty()) + SSMI = I->second.second.back(); + return I->second.first >> 1; // Remove the CanClobber bit. + } return 0; } - - const MRegisterInfo *getRegInfo() const { return MRI; } + /// addLastUse - Add the last use information of all stack slots whose + /// values are available in the specific register. + void addLastUse(unsigned PhysReg, MachineInstr *Use) { + std::multimap::iterator I = + PhysRegsAvailable.lower_bound(PhysReg); + while (I != PhysRegsAvailable.end() && I->first == PhysReg) { + int Slot = I->second; + I++; + + std::map::iterator II = SpillSlotsAvailable.find(Slot); + assert(II != SpillSlotsAvailable.end() && "Slot not available!"); + unsigned Val = II->second.first; + assert((Val >> 1) == PhysReg && "Bidirectional map mismatch!"); + // This can be true if there are multiple uses of the same register. + if (II->second.second.back() != Use) + II->second.second.push_back(Use); + } + } + + /// removeLastUse - Remove the last use information of all stack slots whose + /// values are available in the specific register. + void removeLastUse(unsigned PhysReg, MachineInstr *Use) { + std::multimap::iterator I = + PhysRegsAvailable.lower_bound(PhysReg); + while (I != PhysRegsAvailable.end() && I->first == PhysReg) { + int Slot = I->second; + I++; + + std::map::iterator II = SpillSlotsAvailable.find(Slot); + assert(II != SpillSlotsAvailable.end() && "Slot not available!"); + unsigned Val = II->second.first; + assert((Val >> 1) == PhysReg && "Bidirectional map mismatch!"); + if (II->second.second.back() == Use) + II->second.second.pop_back(); + } + } + /// addAvailable - Mark that the specified stack slot 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 Slot, unsigned Reg, bool CanClobber = true) { + void addAvailable(int Slot, MachineInstr *MI, unsigned Reg, + bool CanClobber = true) { // If this stack slot is thought to be available in some other physreg, // remove its record. ModifyStackSlot(Slot); PhysRegsAvailable.insert(std::make_pair(Reg, Slot)); - SpillSlotsAvailable[Slot] = (Reg << 1) | (unsigned)CanClobber; + std::vector DefUses; + DefUses.push_back(MI); + SpillSlotsAvailable[Slot] = + std::make_pair((Reg << 1) | (unsigned)CanClobber, DefUses); - DEBUG(std::cerr << "Remembering SS#" << Slot << " in physreg " - << MRI->getName(Reg) << "\n"); + if (Slot > VirtRegMap::MAX_STACK_SLOT) + DOUT << "Remembering RM#" << Slot-VirtRegMap::MAX_STACK_SLOT-1; + else + DOUT << "Remembering SS#" << Slot; + 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 Slot) const { assert(SpillSlotsAvailable.count(Slot) && "Slot not available!"); - return SpillSlotsAvailable.find(Slot)->second & 1; + return SpillSlotsAvailable.find(Slot)->second.first & 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 we thing lives in /// it and any of its aliases. @@ -305,6 +394,33 @@ public: /// for this slot lives in (as the previous value is dead now). void ModifyStackSlot(int Slot); }; +} + +/// 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 Slot = I->second; + I++; + assert((SpillSlotsAvailable[Slot].first >> 1) == PhysReg && + "Bidirectional map mismatch!"); + SpillSlotsAvailable[Slot].first &= ~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. @@ -314,11 +430,15 @@ void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) { while (I != PhysRegsAvailable.end() && I->first == PhysReg) { int Slot = I->second; PhysRegsAvailable.erase(I++); - assert((SpillSlotsAvailable[Slot] >> 1) == PhysReg && + assert((SpillSlotsAvailable[Slot].first >> 1) == PhysReg && "Bidirectional map mismatch!"); SpillSlotsAvailable.erase(Slot); - DEBUG(std::cerr << "PhysReg " << MRI->getName(PhysReg) - << " clobbered, invalidating SS#" << Slot << "\n"); + DOUT << "PhysReg " << MRI->getName(PhysReg) + << " clobbered, invalidating "; + if (Slot > VirtRegMap::MAX_STACK_SLOT) + DOUT << "RM#" << Slot-VirtRegMap::MAX_STACK_SLOT-1 << "\n"; + else + DOUT << "SS#" << Slot << "\n"; } } @@ -335,9 +455,9 @@ void AvailableSpills::ClobberPhysReg(unsigned PhysReg) { /// changes. This removes information about which register the previous value /// for this slot lives in (as the previous value is dead now). void AvailableSpills::ModifyStackSlot(int Slot) { - std::map::iterator It = SpillSlotsAvailable.find(Slot); + std::map::iterator It = SpillSlotsAvailable.find(Slot); if (It == SpillSlotsAvailable.end()) return; - unsigned Reg = It->second >> 1; + unsigned Reg = It->second.first >> 1; SpillSlotsAvailable.erase(It); // This register may hold the value of multiple stack slots, only remove this @@ -380,11 +500,14 @@ namespace { /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that /// is reused instead of reloaded. - class ReuseInfo { + class VISIBILITY_HIDDEN ReuseInfo { MachineInstr &MI; std::vector Reuses; + BitVector PhysRegsClobbered; public: - ReuseInfo(MachineInstr &mi) : MI(mi) {} + ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) { + PhysRegsClobbered.resize(mri->getNumRegs()); + } bool hasReuses() const { return !Reuses.empty(); @@ -403,28 +526,37 @@ namespace { Reuses.push_back(ReusedOp(OpNo, StackSlot, 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::map &MaybeDeadStores) { + std::map &MaybeDeadStores, + SmallSet &Rejected) { 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. - if (Op.PhysRegReused == PhysReg) { + // 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; - - // Remove the record for the previous reuse. We know it can never be - // invalidated now. - Reuses.erase(Reuses.begin()+ro); - return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores); + Rejected.insert(PhysReg); + return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected); } else { // Otherwise, we might also have a problem if a previously reused // value aliases the new register. If so, codegen the previous reload @@ -437,50 +569,77 @@ namespace { // to undo a previous reuse. MachineBasicBlock *MBB = MI->getParent(); const TargetRegisterClass *AliasRC = - MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg); - MRI->loadRegFromStackSlot(*MBB, MI, Op.AssignedPhysReg, - Op.StackSlot, AliasRC); - Spills.ClobberPhysReg(Op.AssignedPhysReg); - Spills.ClobberPhysReg(Op.PhysRegReused); + 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); + + MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg, + NewOp.StackSlot, AliasRC); + Spills.ClobberPhysReg(NewPhysReg); + Spills.ClobberPhysReg(NewOp.PhysRegReused); // Any stores to this stack slot are not dead anymore. - MaybeDeadStores.erase(Op.StackSlot); + MaybeDeadStores.erase(NewOp.StackSlot); - MI->SetMachineOperandReg(Op.Operand, Op.AssignedPhysReg); + MI->getOperand(NewOp.Operand).setReg(NewPhysReg); - Spills.addAvailable(Op.StackSlot, Op.AssignedPhysReg); + Spills.addAvailable(NewOp.StackSlot, MI, NewPhysReg); ++NumLoads; DEBUG(MachineBasicBlock::iterator MII = MI; - std::cerr << '\t' << *prior(MII)); + DOUT << '\t' << *prior(MII)); - DEBUG(std::cerr << "Reuse undone!\n"); - Reuses.erase(Reuses.begin()+ro); + 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::map &MaybeDeadStores) { + SmallSet Rejected; + return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected); + } }; } /// 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, const VirtRegMap &VRM) { - - DEBUG(std::cerr << MBB.getBasicBlock()->getName() << ":\n"); +void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM, + std::vector &ReMatedMIs) { + DOUT << MBB.getBasicBlock()->getName() << ":\n"; // 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); - // DefAndUseVReg - When we see a def&use operand that is spilled, keep track - // of it. ".first" is the machine operand index (should always be 0 for now), - // and ".second" is the virtual register that is spilled. - std::vector > DefAndUseVReg; - // 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 @@ -498,9 +657,42 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) { /// ReusedOperands - Keep track of operand reuse in case we need to undo /// reuse. - ReuseInfo ReusedOperands(MI); - - DefAndUseVReg.clear(); + ReuseInfo ReusedOperands(MI, MRI); + + // Loop over all of the implicit defs, clearing them from our available + // sets. + const TargetInstrDescriptor *TID = MI.getInstrDescriptor(); + + // If this instruction is being rematerialized, just remove it! + int FrameIdx; + if ((TID->Flags & M_REMATERIALIZIBLE) || + TII->isLoadFromStackSlot(&MI, FrameIdx)) { + bool Remove = true; + 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. + if (MO.isDef() && !VRM.isReMaterialized(MO.getReg())) { + Remove = false; + break; + } + } + if (Remove) { + VRM.RemoveFromFoldedVirtMap(&MI); + ReMatedMIs.push_back(MI.removeFromParent()); + MII = NextMII; + continue; + } + } + + const unsigned *ImpDef = TID->ImplicitDefs; + if (ImpDef) { + for ( ; *ImpDef; ++ImpDef) { + PhysRegsUsed[*ImpDef] = true; + 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) { @@ -512,6 +704,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) { // Ignore physregs for spilling, but remember that it is used by this // function. PhysRegsUsed[MO.getReg()] = true; + ReusedOperands.markClobbered(MO.getReg()); continue; } @@ -523,7 +716,9 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) { // This virtual register was assigned a physreg! unsigned Phys = VRM.getPhys(VirtReg); PhysRegsUsed[Phys] = true; - MI.SetMachineOperandReg(i, Phys); + if (MO.isDef()) + ReusedOperands.markClobbered(Phys); + MI.getOperand(i).setReg(Phys); continue; } @@ -531,46 +726,156 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) { if (!MO.isUse()) continue; // Handle defs in the loop below (handle use&def here though) - // If this is both a def and a use, we need to emit a store to the - // stack slot after the instruction. Keep track of D&U operands - // because we are about to change it to a physreg here. - if (MO.isDef()) { - // Remember that this was a def-and-use operand, and that the - // stack slot is live after this instruction executes. - DefAndUseVReg.push_back(std::make_pair(i, VirtReg)); - } - + bool doReMat = VRM.isReMaterialized(VirtReg); int StackSlot = VRM.getStackSlot(VirtReg); unsigned PhysReg; // Check to see if this stack slot is available. - if ((PhysReg = Spills.getSpillSlotPhysReg(StackSlot)) && - // Don't reuse it for a def&use operand if we aren't allowed to change - // the physreg! - (!MO.isDef() || Spills.canClobberPhysReg(StackSlot))) { - // If this stack slot value is already available, reuse it! - DEBUG(std::cerr << "Reusing SS#" << StackSlot << " from physreg " - << MRI->getName(PhysReg) << " for vreg" - << VirtReg <<" instead of reloading into physreg " - << MRI->getName(VRM.getPhys(VirtReg)) << "\n"); - MI.SetMachineOperandReg(i, PhysReg); - - // 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. + MachineInstr *SSMI = NULL; + if ((PhysReg = Spills.getSpillSlotPhysReg(StackSlot, SSMI))) { + // 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).isReg() && + 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(StackSlot) && + !ReusedOperands.isClobbered(PhysReg); + } + + if (CanReuse) { + // If this stack slot value is already available, reuse it! + if (StackSlot > VirtRegMap::MAX_STACK_SLOT) + DOUT << "Reusing RM#" << StackSlot-VirtRegMap::MAX_STACK_SLOT-1; + else + DOUT << "Reusing SS#" << StackSlot; + DOUT << " from physreg " + << MRI->getName(PhysReg) << " for vreg" + << VirtReg <<" instead of reloading into physreg " + << MRI->getName(VRM.getPhys(VirtReg)) << "\n"; + MI.getOperand(i).setReg(PhysReg); + + // Extend the live range of the MI that last kill the register if + // necessary. + bool WasKill = false; + if (SSMI) { + int UIdx = SSMI->findRegisterUseOperand(PhysReg, true); + if (UIdx != -1) { + MachineOperand &MOK = SSMI->getOperand(UIdx); + WasKill = MOK.isKill(); + MOK.unsetIsKill(); + } + } + if (ti == -1) { + // Unless it's the use of a two-address code, transfer the kill + // of the reused register to this use. + if (WasKill) + MI.getOperand(i).setIsKill(); + Spills.addLastUse(PhysReg, &MI); + } + + // 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, StackSlot, PhysReg, + VRM.getPhys(VirtReg), VirtReg); + if (ti != -1) + // Only mark it clobbered if this is a use&def operand. + ReusedOperands.markClobbered(PhysReg); + ++NumReused; + continue; + } + + // 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 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, StackSlot, PhysReg, - VRM.getPhys(VirtReg), VirtReg); + // 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); + + // 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 (StackSlot > VirtRegMap::MAX_STACK_SLOT) + DOUT << "Reusing RM#" << StackSlot-VirtRegMap::MAX_STACK_SLOT-1; + else + DOUT << "Reusing SS#" << StackSlot; + DOUT << " from physreg " << MRI->getName(PhysReg) << " for vreg" + << VirtReg + << " instead of reloading into same physreg.\n"; + MI.getOperand(i).setReg(PhysReg); + ReusedOperands.markClobbered(PhysReg); + ++NumReused; + continue; + } + + const TargetRegisterClass* RC = + MBB.getParent()->getSSARegMap()->getRegClass(VirtReg); + + PhysRegsUsed[DesignatedReg] = true; + ReusedOperands.markClobbered(DesignatedReg); + MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC); + + // Extend the live range of the MI that last kill the register if + // necessary. + bool WasKill = false; + if (SSMI) { + int UIdx = SSMI->findRegisterUseOperand(PhysReg, true); + if (UIdx != -1) { + MachineOperand &MOK = SSMI->getOperand(UIdx); + WasKill = MOK.isKill(); + MOK.unsetIsKill(); + } + } + MachineInstr *CopyMI = prior(MII); + if (WasKill) { + // Transfer kill to the next use. + int UIdx = CopyMI->findRegisterUseOperand(PhysReg); + assert(UIdx != -1); + MachineOperand &MOU = CopyMI->getOperand(UIdx); + MOU.setIsKill(); + } + Spills.addLastUse(PhysReg, CopyMI); + + // This invalidates DesignatedReg. + Spills.ClobberPhysReg(DesignatedReg); + + Spills.addAvailable(StackSlot, &MI, DesignatedReg); + MI.getOperand(i).setReg(DesignatedReg); + DOUT << '\t' << *prior(MII); ++NumReused; continue; } @@ -590,66 +895,102 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) { Spills, MaybeDeadStores); PhysRegsUsed[PhysReg] = true; - MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC); + ReusedOperands.markClobbered(PhysReg); + if (doReMat) { + MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg)); + ++NumReMats; + } else { + MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC); + ++NumLoads; + } // This invalidates PhysReg. Spills.ClobberPhysReg(PhysReg); // Any stores to this stack slot are not dead anymore. - MaybeDeadStores.erase(StackSlot); - Spills.addAvailable(StackSlot, PhysReg); - ++NumLoads; - MI.SetMachineOperandReg(i, PhysReg); - DEBUG(std::cerr << '\t' << *prior(MII)); + if (!doReMat) + MaybeDeadStores.erase(StackSlot); + Spills.addAvailable(StackSlot, &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(); + MI.getOperand(i).setReg(PhysReg); + DOUT << '\t' << *prior(MII); } - // Loop over all of the implicit defs, clearing them from our available - // sets. - for (const unsigned *ImpDef = TII->getImplicitDefs(MI.getOpcode()); - *ImpDef; ++ImpDef) { - PhysRegsUsed[*ImpDef] = true; - Spills.ClobberPhysReg(*ImpDef); - } - - DEBUG(std::cerr << '\t' << MI); + 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 VirtRegMap::MI2VirtMapTy::const_iterator I, End; for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) { - DEBUG(std::cerr << "Folded vreg: " << I->second.first << " MR: " - << I->second.second); + DOUT << "Folded vreg: " << I->second.first << " MR: " + << I->second.second; unsigned VirtReg = I->second.first; VirtRegMap::ModRef MR = I->second.second; if (!VRM.hasStackSlot(VirtReg)) { - DEBUG(std::cerr << ": No stack slot!\n"); + DOUT << ": No stack slot!\n"; continue; } int SS = VRM.getStackSlot(VirtReg); - DEBUG(std::cerr << " - StackSlot: " << SS << "\n"); + 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; if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) { - // If this spill slot is available, turn it into a copy (or nothing) - // instead of leaving it as a load! - unsigned InReg; - if (FrameIdx == SS && (InReg = Spills.getSpillSlotPhysReg(SS))) { - DEBUG(std::cerr << "Promoted Load To Copy: " << MI); - MachineFunction &MF = *MBB.getParent(); - if (DestReg != InReg) { - MRI->copyRegToReg(MBB, &MI, DestReg, InReg, - MF.getSSARegMap()->getRegClass(VirtReg)); - // 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. + if (FrameIdx == SS) { + // If this spill slot is available, turn it into a copy (or nothing) + // instead of leaving it as a load! + MachineInstr *SSMI = NULL; + if (unsigned InReg = Spills.getSpillSlotPhysReg(SS, SSMI)) { + DOUT << "Promoted Load To Copy: " << MI; + MachineFunction &MF = *MBB.getParent(); + if (DestReg != InReg) { + MRI->copyRegToReg(MBB, &MI, DestReg, InReg, + MF.getSSARegMap()->getRegClass(VirtReg)); + // 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. + } else + DOUT << "Removing now-noop copy: " << MI; + + // Either way, the live range of the last kill of InReg has been + // extended. Remove its kill. + bool WasKill = false; + if (SSMI) { + int UIdx = SSMI->findRegisterUseOperand(InReg, true); + if (UIdx != -1) { + MachineOperand &MOK = SSMI->getOperand(UIdx); + WasKill = MOK.isKill(); + MOK.unsetIsKill(); + } + } + if (NextMII != MBB.end()) { + // If NextMII uses InReg and the use is not a two address + // operand, mark it killed. + int UIdx = NextMII->findRegisterUseOperand(InReg); + if (UIdx != -1) { + MachineOperand &MOU = NextMII->getOperand(UIdx); + if (WasKill) { + const TargetInstrDescriptor *NTID = + NextMII->getInstrDescriptor(); + if (UIdx >= NTID->numOperands || + NTID->getOperandConstraint(UIdx, TOI::TIED_TO) == -1) + MOU.setIsKill(); + } + Spills.addLastUse(InReg, &(*NextMII)); + } + } + + VRM.RemoveFromFoldedVirtMap(&MI); + MBB.erase(&MI); + goto ProcessNextInst; } - MBB.erase(&MI); - goto ProcessNextInst; } } } @@ -662,8 +1003,10 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) { MaybeDeadStores.erase(MDSI); else { // If we get here, the store is dead, nuke it now. - assert(MR == VirtRegMap::isMod && "Can't be modref!"); + assert(VirtRegMap::isMod && "Can't be modref!"); + DOUT << "Removed dead store:\t" << *MDSI->second; MBB.erase(MDSI->second); + VRM.RemoveFromFoldedVirtMap(MDSI->second); MaybeDeadStores.erase(MDSI); ++NumDSE; } @@ -692,7 +1035,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) { // 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, SrcReg, false /*don't clobber*/); + Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/); } } } @@ -705,70 +1048,71 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) { unsigned VirtReg = MO.getReg(); if (!MRegisterInfo::isVirtualRegister(VirtReg)) { - // Check to see if this is a def-and-use vreg operand that we do need - // to insert a store for. - bool OpTakenCareOf = false; - if (MO.isUse() && !DefAndUseVReg.empty()) { - for (unsigned dau = 0, e = DefAndUseVReg.size(); dau != e; ++dau) - if (DefAndUseVReg[dau].first == i) { - VirtReg = DefAndUseVReg[dau].second; - OpTakenCareOf = true; - break; - } + // 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; + Spills.removeLastUse(Src, &MI); + MBB.erase(&MI); + VRM.RemoveFromFoldedVirtMap(&MI); + Spills.disallowClobberPhysReg(VirtReg); + goto ProcessNextInst; } - - if (!OpTakenCareOf) { - // 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; - DEBUG(std::cerr << "Removing now-noop copy: " << MI); - MBB.erase(&MI); - goto ProcessNextInst; - } - Spills.ClobberPhysReg(VirtReg); - continue; + + // 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!"); + + // Otherwise, if it wasn't available, remember that it is now! + Spills.addAvailable(FrameIdx, &MI, DestReg); + goto ProcessNextInst; } + + continue; } // The only vregs left are stack slot definitions. int StackSlot = VRM.getStackSlot(VirtReg); const TargetRegisterClass *RC = MBB.getParent()->getSSARegMap()->getRegClass(VirtReg); - unsigned PhysReg; - // If this is a def&use operand, and we used a different physreg for - // it than the one assigned, make sure to execute the store from the - // correct physical register. - if (MO.getReg() == 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(); + else { PhysReg = VRM.getPhys(VirtReg); - else - PhysReg = MO.getReg(); + 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); + } + } PhysRegsUsed[PhysReg] = true; + ReusedOperands.markClobbered(PhysReg); MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC); - DEBUG(std::cerr << "Store:\t" << *next(MII)); - MI.SetMachineOperandReg(i, PhysReg); + DOUT << "Store:\t" << *next(MII); + MI.getOperand(i).setReg(PhysReg); - // 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; - DEBUG(std::cerr << "Removing now-noop copy: " << MI); - MBB.erase(&MI); - goto ProcessNextInst; - } - } - // If there is a dead store to this stack slot, nuke it now. MachineInstr *&LastStore = MaybeDeadStores[StackSlot]; if (LastStore) { - DEBUG(std::cerr << " Killed store:\t" << *LastStore); + DOUT << "Removed dead store:\t" << *LastStore; ++NumDSE; MBB.erase(LastStore); + VRM.RemoveFromFoldedVirtMap(LastStore); } LastStore = next(MII); @@ -777,8 +1121,22 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) { // in PhysReg. Spills.ModifyStackSlot(StackSlot); Spills.ClobberPhysReg(PhysReg); - Spills.addAvailable(StackSlot, PhysReg); + Spills.addAvailable(StackSlot, LastStore, PhysReg); ++NumStores; + + // 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; + Spills.removeLastUse(Src, &MI); + MBB.erase(&MI); + VRM.RemoveFromFoldedVirtMap(&MI); + goto ProcessNextInst; + } + } } } ProcessNextInst: