#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Support/Compiler.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
+#include <algorithm>
+#include <iostream>
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");
+ static Statistic<> NumSpills("spiller", "Number of register spills");
+ static Statistic<> NumStores("spiller", "Number of stores added");
+ static Statistic<> NumLoads ("spiller", "Number of loads added");
+ static Statistic<> NumReused("spiller", "Number of values reused");
+ static Statistic<> NumDSE ("spiller", "Number of dead stores elided");
+ static Statistic<> NumDCE ("spiller", "Number of copies elided");
enum SpillerName { simple, local };
- cl::opt<SpillerName>
+ static cl::opt<SpillerName>
SpillerOpt("spiller",
cl::desc("Spiller to use: (default: local)"),
cl::Prefix,
// VirtRegMap implementation
//===----------------------------------------------------------------------===//
+VirtRegMap::VirtRegMap(MachineFunction &mf)
+ : TII(*mf.getTarget().getInstrInfo()), MF(mf),
+ Virt2PhysMap(NO_PHYS_REG), Virt2StackSlotMap(NO_STACK_SLOT) {
+ grow();
+}
+
void VirtRegMap::grow() {
Virt2PhysMap.grow(MF.getSSARegMap()->getLastVirtReg());
Virt2StackSlotMap.grow(MF.getSSARegMap()->getLastVirtReg());
Virt2StackSlotMap[virtReg] = frameIndex;
}
-void VirtRegMap::virtFolded(unsigned virtReg,
- MachineInstr* oldMI,
- MachineInstr* newMI) {
- // move previous memory references folded to new instruction
- MI2VirtMapTy::iterator i, e;
- std::vector<MI2VirtMapTy::mapped_type> regs;
- for (tie(i, e) = MI2VirtMap.equal_range(oldMI); i != e; ) {
- regs.push_back(i->second);
- MI2VirtMap.erase(i++);
+void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
+ unsigned OpNo, MachineInstr *NewMI) {
+ // 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++);
+ }
+
+ ModRef MRInfo;
+ if (TII.getOperandConstraint(OldMI->getOpcode(), OpNo,
+ TargetInstrInfo::TIED_TO)) {
+ // Folded a two-address operand.
+ MRInfo = isModRef;
+ } else if (OldMI->getOperand(OpNo).isDef()) {
+ MRInfo = isMod;
+ } else {
+ MRInfo = isRef;
}
- for (unsigned i = 0, e = regs.size(); i != e; ++i)
- MI2VirtMap.insert(std::make_pair(newMI, i));
// add new memory reference
- MI2VirtMap.insert(std::make_pair(newMI, virtReg));
+ MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
}
void VirtRegMap::print(std::ostream &OS) const {
e = MF.getSSARegMap()->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,
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) {
+bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
DEBUG(std::cerr << "********** REWRITE MACHINE CODE **********\n");
DEBUG(std::cerr << "********** Function: "
<< MF.getFunction()->getName() << '\n');
- const TargetMachine& TM = MF.getTarget();
- const MRegisterInfo& MRI = *TM.getRegisterInfo();
+ const TargetMachine &TM = MF.getTarget();
+ const MRegisterInfo &MRI = *TM.getRegisterInfo();
+ bool *PhysRegsUsed = MF.getUsedPhysregs();
// 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
// current machine instr, so it should be small.
std::vector<unsigned> LoadedRegs;
- for (MachineFunction::iterator mbbi = MF.begin(), E = MF.end();
- mbbi != E; ++mbbi) {
- DEBUG(std::cerr << mbbi->getBasicBlock()->getName() << ":\n");
- for (MachineBasicBlock::iterator mii = mbbi->begin(),
- mie = mbbi->end(); mii != mie; ++mii) {
- for (unsigned i = 0, e = mii->getNumOperands(); i != e; ++i) {
- MachineOperand& mop = mii->getOperand(i);
- if (mop.isRegister() && mop.getReg() &&
- MRegisterInfo::isVirtualRegister(mop.getReg())) {
- unsigned virtReg = mop.getReg();
- unsigned physReg = VRM.getPhys(virtReg);
- if (mop.isUse() && VRM.hasStackSlot(mop.getReg()) &&
- std::find(LoadedRegs.begin(), LoadedRegs.end(),
- virtReg) == LoadedRegs.end()) {
- MRI.loadRegFromStackSlot(*mbbi, mii, physReg,
- VRM.getStackSlot(virtReg));
- LoadedRegs.push_back(virtReg);
- DEBUG(std::cerr << '\t';
- prior(mii)->print(std::cerr, &TM));
- ++NumLoads;
- }
-
- if (mop.isDef() && VRM.hasStackSlot(mop.getReg())) {
- MRI.storeRegToStackSlot(*mbbi, next(mii), physReg,
- VRM.getStackSlot(virtReg));
- ++NumStores;
+ for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
+ MBBI != E; ++MBBI) {
+ DEBUG(std::cerr << 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.hasStackSlot(VirtReg)) {
+ int StackSlot = VRM.getStackSlot(VirtReg);
+ const TargetRegisterClass* RC =
+ MF.getSSARegMap()->getRegClass(VirtReg);
+
+ if (MO.isUse() &&
+ std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
+ == LoadedRegs.end()) {
+ MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
+ LoadedRegs.push_back(VirtReg);
+ ++NumLoads;
+ DEBUG(std::cerr << '\t' << *prior(MII));
+ }
+
+ if (MO.isDef()) {
+ MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
+ ++NumStores;
+ }
+ }
+ PhysRegsUsed[PhysReg] = true;
+ MI.getOperand(i).setReg(PhysReg);
+ } else {
+ PhysRegsUsed[MO.getReg()] = true;
}
- mii->SetMachineOperandReg(i, physReg);
- }
}
- DEBUG(std::cerr << '\t'; mii->print(std::cerr, &TM));
+
+ DEBUG(std::cerr << '\t' << MI);
LoadedRegs.clear();
}
}
//===----------------------------------------------------------------------===//
namespace {
- class LocalSpiller : public Spiller {
- typedef std::vector<unsigned> Phys2VirtMap;
- typedef std::vector<bool> PhysFlag;
- typedef DenseMap<MachineInstr*, VirtReg2IndexFunctor> Virt2MI;
-
- MachineFunction *MF;
- const TargetMachine *TM;
- const TargetInstrInfo *TII;
+ /// 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 {
const MRegisterInfo *MRI;
- const VirtRegMap *VRM;
- Phys2VirtMap p2vMap_;
- PhysFlag dirty_;
- Virt2MI lastDef_;
-
+ const TargetInstrInfo *TII;
public:
- bool runOnMachineFunction(MachineFunction &MF, const VirtRegMap &VRM);
-
- private:
- void vacateJustPhysReg(MachineBasicBlock& mbb,
- MachineBasicBlock::iterator mii,
- unsigned physReg);
-
- void vacatePhysReg(MachineBasicBlock& mbb,
- MachineBasicBlock::iterator mii,
- unsigned physReg) {
- vacateJustPhysReg(mbb, mii, physReg);
- for (const unsigned* as = MRI->getAliasSet(physReg); *as; ++as)
- vacateJustPhysReg(mbb, mii, *as);
- }
-
- void handleUse(MachineBasicBlock& mbb,
- MachineBasicBlock::iterator mii,
- unsigned virtReg,
- unsigned physReg) {
- // check if we are replacing a previous mapping
- if (p2vMap_[physReg] != virtReg) {
- vacatePhysReg(mbb, mii, physReg);
- p2vMap_[physReg] = virtReg;
- // load if necessary
- if (VRM->hasStackSlot(virtReg)) {
- MRI->loadRegFromStackSlot(mbb, mii, physReg,
- VRM->getStackSlot(virtReg));
- ++NumLoads;
- DEBUG(std::cerr << "added: ";
- prior(mii)->print(std::cerr, TM));
- lastDef_[virtReg] = mii;
- }
- }
- }
-
- void handleDef(MachineBasicBlock& mbb,
- MachineBasicBlock::iterator mii,
- unsigned virtReg,
- unsigned physReg) {
- // check if we are replacing a previous mapping
- if (p2vMap_[physReg] != virtReg)
- vacatePhysReg(mbb, mii, physReg);
-
- p2vMap_[physReg] = virtReg;
- dirty_[physReg] = true;
- lastDef_[virtReg] = mii;
+ 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");
+
+ for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
+ MBB != E; ++MBB)
+ RewriteMBB(*MBB, VRM);
+ return true;
}
-
- void eliminateVirtRegsInMbb(MachineBasicBlock& mbb);
+ private:
+ void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
+ void ClobberPhysReg(unsigned PR, std::map<int, unsigned> &SpillSlots,
+ std::multimap<unsigned, int> &PhysRegs);
+ void ClobberPhysRegOnly(unsigned PR, std::map<int, unsigned> &SpillSlots,
+ std::multimap<unsigned, int> &PhysRegs);
+ void ModifyStackSlot(int Slot, std::map<int, unsigned> &SpillSlots,
+ std::multimap<unsigned, int> &PhysRegs);
};
}
-bool LocalSpiller::runOnMachineFunction(MachineFunction &mf,
- const VirtRegMap &vrm) {
- MF = &mf;
- TM = &MF->getTarget();
- TII = TM->getInstrInfo();
- MRI = TM->getRegisterInfo();
- VRM = &vrm;
- p2vMap_.assign(MRI->getNumRegs(), 0);
- dirty_.assign(MRI->getNumRegs(), false);
+/// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
+/// top down, keep track of which spills slots 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 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;
+
+ // 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<int, unsigned> 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<unsigned, int> PhysRegsAvailable;
+
+ void ClobberPhysRegOnly(unsigned PhysReg);
+public:
+ AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
+ : MRI(mri), TII(tii) {
+ }
+
+ /// 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<int, unsigned>::const_iterator I = SpillSlotsAvailable.find(Slot);
+ if (I != SpillSlotsAvailable.end())
+ return I->second >> 1; // Remove the CanClobber bit.
+ return 0;
+ }
+
+ const MRegisterInfo *getRegInfo() const { return MRI; }
+
+ /// 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) {
+ // 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;
+
+ DEBUG(std::cerr << "Remembering SS#" << Slot << " 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;
+ }
+
+ /// 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 ClobberPhysReg(unsigned PhysReg);
+
+ /// ModifyStackSlot - 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 ModifyStackSlot(int Slot);
+};
+}
- DEBUG(std::cerr << "********** REWRITE MACHINE CODE **********\n");
- DEBUG(std::cerr << "********** Function: "
- << MF->getFunction()->getName() << '\n');
-
- for (MachineFunction::iterator mbbi = MF->begin(),
- mbbe = MF->end(); mbbi != mbbe; ++mbbi) {
- lastDef_.grow(MF->getSSARegMap()->getLastVirtReg());
- DEBUG(std::cerr << mbbi->getBasicBlock()->getName() << ":\n");
- eliminateVirtRegsInMbb(*mbbi);
- // clear map, dirty flag and last ref
- p2vMap_.assign(p2vMap_.size(), 0);
- dirty_.assign(dirty_.size(), false);
- lastDef_.clear();
+/// 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<unsigned, int>::iterator I =
+ PhysRegsAvailable.lower_bound(PhysReg);
+ while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
+ int Slot = I->second;
+ PhysRegsAvailable.erase(I++);
+ assert((SpillSlotsAvailable[Slot] >> 1) == PhysReg &&
+ "Bidirectional map mismatch!");
+ SpillSlotsAvailable.erase(Slot);
+ DEBUG(std::cerr << "PhysReg " << MRI->getName(PhysReg)
+ << " clobbered, invalidating SS#" << Slot << "\n");
}
- return true;
}
-void LocalSpiller::vacateJustPhysReg(MachineBasicBlock& mbb,
- MachineBasicBlock::iterator mii,
- unsigned physReg) {
- unsigned virtReg = p2vMap_[physReg];
- if (dirty_[physReg] && VRM->hasStackSlot(virtReg)) {
- assert(lastDef_[virtReg] && "virtual register is mapped "
- "to a register and but was not defined!");
- MachineBasicBlock::iterator lastDef = lastDef_[virtReg];
- MachineBasicBlock::iterator nextLastRef = next(lastDef);
- MRI->storeRegToStackSlot(*lastDef->getParent(),
- nextLastRef,
- physReg,
- VRM->getStackSlot(virtReg));
- ++NumStores;
- DEBUG(std::cerr << "added: ";
- prior(nextLastRef)->print(std::cerr, TM);
- std::cerr << "after: ";
- lastDef->print(std::cerr, TM));
- lastDef_[virtReg] = 0;
+/// 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);
+}
+
+/// ModifyStackSlot - 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::ModifyStackSlot(int Slot) {
+ std::map<int, unsigned>::iterator It = SpillSlotsAvailable.find(Slot);
+ if (It == SpillSlotsAvailable.end()) return;
+ unsigned Reg = It->second >> 1;
+ SpillSlotsAvailable.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<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
+ for (; ; ++I) {
+ assert(I != PhysRegsAvailable.end() && I->first == Reg &&
+ "Map inverse broken!");
+ if (I->second == Slot) break;
}
- p2vMap_[physReg] = 0;
- dirty_[physReg] = false;
+ PhysRegsAvailable.erase(I);
}
-void LocalSpiller::eliminateVirtRegsInMbb(MachineBasicBlock &MBB) {
- for (MachineBasicBlock::iterator MI = MBB.begin(), E = MBB.end();
- MI != E; ++MI) {
-
- // if we have 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, e;
- for (tie(i, e) = VRM->getFoldedVirts(MI); i != e; ++i) {
- if (VRM->hasPhys(i->second))
- vacateJustPhysReg(MBB, MI, VRM->getPhys(i->second));
+
+
+// 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;
+
+ // StackSlot - The spill slot of the value being reused.
+ unsigned StackSlot;
+
+ // 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), StackSlot(ss), PhysRegReused(prr), AssignedPhysReg(apr),
+ VirtReg(vreg) {}
+ };
+
+ /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
+ /// is reused instead of reloaded.
+ class VISIBILITY_HIDDEN ReuseInfo {
+ MachineInstr &MI;
+ std::vector<ReusedOp> Reuses;
+ public:
+ ReuseInfo(MachineInstr &mi) : MI(mi) {}
+
+ 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 StackSlot,
+ 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, StackSlot, PhysRegReused,
+ AssignedPhysReg, VirtReg));
+ }
+
+ /// 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<int, MachineInstr*> &MaybeDeadStores) {
+ 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) {
+ // 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);
+ } else {
+ // Otherwise, we might also have a problem if a previously reused
+ // value aliases the new register. If so, codegen the previous reload
+ // and use this one.
+ unsigned PRRU = Op.PhysRegReused;
+ const MRegisterInfo *MRI = Spills.getRegInfo();
+ if (MRI->areAliases(PRRU, PhysReg)) {
+ // Okay, we found out that an alias of a reused register
+ // was used. This isn't good because it means we have
+ // to undo a previous reuse.
+ MachineBasicBlock *MBB = MI->getParent();
+ const TargetRegisterClass *AliasRC =
+ MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
+
+ // Copy Op out of the vector and remove it, we're going to insert an
+ // explicit load for it.
+ ReusedOp NewOp = Op;
+ Reuses.erase(Reuses.begin()+ro);
+
+ // Ok, we're going to try to reload the assigned physreg into the
+ // slot that we were supposed to in the first place. However, that
+ // register could hold a reuse. Check to see if it conflicts or
+ // would prefer us to use a different register.
+ unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
+ MI, Spills, MaybeDeadStores);
+
+ 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(NewOp.StackSlot);
+
+ MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
+
+ Spills.addAvailable(NewOp.StackSlot, NewPhysReg);
+ ++NumLoads;
+ DEBUG(MachineBasicBlock::iterator MII = MI;
+ std::cerr << '\t' << *prior(MII));
+
+ DEBUG(std::cerr << "Reuse undone!\n");
+ --NumReused;
+
+ // Finally, PhysReg is now available, go ahead and use it.
+ return PhysReg;
+ }
+ }
+ }
+ return PhysReg;
}
+ };
+}
- // rewrite all used operands
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- MachineOperand& op = MI->getOperand(i);
- if (op.isRegister() && op.getReg() && op.isUse() &&
- MRegisterInfo::isVirtualRegister(op.getReg())) {
- unsigned virtReg = op.getReg();
- unsigned physReg = VRM->getPhys(virtReg);
- handleUse(MBB, MI, virtReg, physReg);
- MI->SetMachineOperandReg(i, physReg);
- // mark as dirty if this is def&use
- if (op.isDef()) {
- dirty_[physReg] = true;
- lastDef_[virtReg] = MI;
+
+/// rewriteMBB - Keep track of which spills are available even after the
+/// register allocator is done with them. If possible, avoid reloading vregs.
+void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
+
+ DEBUG(std::cerr << 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);
+
+ // 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::map<int, MachineInstr*> MaybeDeadStores;
+
+ bool *PhysRegsUsed = MBB.getParent()->getUsedPhysregs();
+
+ for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
+ MII != E; ) {
+ MachineInstr &MI = *MII;
+ MachineBasicBlock::iterator NextMII = MII; ++NextMII;
+
+ /// ReusedOperands - Keep track of operand reuse in case we need to undo
+ /// reuse.
+ ReuseInfo ReusedOperands(MI);
+
+ // 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.
+
+ if (MRegisterInfo::isPhysicalRegister(MO.getReg())) {
+ // Ignore physregs for spilling, but remember that it is used by this
+ // function.
+ PhysRegsUsed[MO.getReg()] = true;
+ continue;
+ }
+
+ assert(MRegisterInfo::isVirtualRegister(MO.getReg()) &&
+ "Not a virtual or a physical register?");
+
+ unsigned VirtReg = MO.getReg();
+ if (!VRM.hasStackSlot(VirtReg)) {
+ // This virtual register was assigned a physreg!
+ unsigned Phys = VRM.getPhys(VirtReg);
+ PhysRegsUsed[Phys] = true;
+ MI.getOperand(i).setReg(Phys);
+ 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)
+
+ int StackSlot = VRM.getStackSlot(VirtReg);
+ unsigned PhysReg;
+
+ // Check to see if this stack slot is available.
+ if ((PhysReg = Spills.getSpillSlotPhysReg(StackSlot))) {
+
+ // 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 = TII->getOperandConstraint(MI.getOpcode(), i,
+ TargetInstrInfo::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.
+ CanReuse = Spills.canClobberPhysReg(StackSlot);
+ }
+
+ if (CanReuse) {
+ // 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.getOperand(i).setReg(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.
+ //
+ // 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);
+ ++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 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!
+ DEBUG(std::cerr << "Reusing SS#" << StackSlot << " from physreg "
+ << MRI->getName(PhysReg) << " for vreg"
+ << VirtReg
+ << " instead of reloading into same physreg.\n");
+ MI.getOperand(i).setReg(PhysReg);
+ ++NumReused;
+ continue;
}
+
+ const TargetRegisterClass* RC =
+ MBB.getParent()->getSSARegMap()->getRegClass(VirtReg);
+
+ PhysRegsUsed[DesignatedReg] = true;
+ MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC);
+
+ // This invalidates DesignatedReg.
+ Spills.ClobberPhysReg(DesignatedReg);
+
+ Spills.addAvailable(StackSlot, DesignatedReg);
+ MI.getOperand(i).setReg(DesignatedReg);
+ DEBUG(std::cerr << '\t' << *prior(MII));
+ ++NumReused;
+ continue;
}
+
+ // Otherwise, reload it and remember that we have it.
+ PhysReg = VRM.getPhys(VirtReg);
+ assert(PhysReg && "Must map virtreg to physreg!");
+ const TargetRegisterClass* RC =
+ MBB.getParent()->getSSARegMap()->getRegClass(VirtReg);
+
+ // 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);
+
+ PhysRegsUsed[PhysReg] = true;
+ MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
+ // 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.getOperand(i).setReg(PhysReg);
+ DEBUG(std::cerr << '\t' << *prior(MII));
}
- // spill implicit physical register defs
- const TargetInstrDescriptor& tid = TII->get(MI->getOpcode());
- for (const unsigned* id = tid.ImplicitDefs; *id; ++id)
- vacatePhysReg(MBB, MI, *id);
-
- // spill explicit physical register defs
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- MachineOperand& op = MI->getOperand(i);
- if (op.isRegister() && op.getReg() && !op.isUse() &&
- MRegisterInfo::isPhysicalRegister(op.getReg()))
- vacatePhysReg(MBB, MI, op.getReg());
+ // Loop over all of the implicit defs, clearing them from our available
+ // sets.
+ const unsigned *ImpDef = TII->getImplicitDefs(MI.getOpcode());
+ if (ImpDef) {
+ for ( ; *ImpDef; ++ImpDef) {
+ PhysRegsUsed[*ImpDef] = true;
+ Spills.ClobberPhysReg(*ImpDef);
+ }
}
- // rewrite def operands (def&use was handled with the
- // uses so don't check for those here)
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- MachineOperand& op = MI->getOperand(i);
- if (op.isRegister() && op.getReg() && !op.isUse())
- if (MRegisterInfo::isPhysicalRegister(op.getReg()))
- vacatePhysReg(MBB, MI, op.getReg());
+ DEBUG(std::cerr << '\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);
+ unsigned VirtReg = I->second.first;
+ VirtRegMap::ModRef MR = I->second.second;
+ if (!VRM.hasStackSlot(VirtReg)) {
+ DEBUG(std::cerr << ": No stack slot!\n");
+ continue;
+ }
+ int SS = VRM.getStackSlot(VirtReg);
+ DEBUG(std::cerr << " - 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 (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.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.
+ }
+ VRM.RemoveFromFoldedVirtMap(&MI);
+ MBB.erase(&MI);
+ 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.
+ std::map<int, MachineInstr*>::iterator MDSI = MaybeDeadStores.find(SS);
+ if (MDSI != MaybeDeadStores.end()) {
+ if (MR & VirtRegMap::isRef) // Previous store is not dead.
+ MaybeDeadStores.erase(MDSI);
else {
- unsigned physReg = VRM->getPhys(op.getReg());
- handleDef(MBB, MI, op.getReg(), physReg);
- MI->SetMachineOperandReg(i, physReg);
+ // If we get here, the store is dead, nuke it now.
+ assert(VirtRegMap::isMod && "Can't be modref!");
+ DEBUG(std::cerr << "Removed dead store:\t" << *MDSI->second);
+ MBB.erase(MDSI->second);
+ VRM.RemoveFromFoldedVirtMap(MDSI->second);
+ MaybeDeadStores.erase(MDSI);
+ ++NumDSE;
}
+ }
+
+ // 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.ModifyStackSlot(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, SrcReg, false /*don't clobber*/);
+ }
+ }
+ }
}
- DEBUG(std::cerr << '\t'; MI->print(std::cerr, TM));
- }
+ // 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()) {
+ 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;
+ DEBUG(std::cerr << "Removing now-noop copy: " << MI);
+ MBB.erase(&MI);
+ VRM.RemoveFromFoldedVirtMap(&MI);
+ goto ProcessNextInst;
+ }
+
+ // If it's not a no-op copy, it clobbers the value in the destreg.
+ Spills.ClobberPhysReg(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, DestReg);
+ goto ProcessNextInst;
+ }
+
+ continue;
+ }
- for (unsigned i = 1, e = p2vMap_.size(); i != e; ++i)
- vacateJustPhysReg(MBB, MBB.getFirstTerminator(), i);
+ // The only vregs left are stack slot definitions.
+ int StackSlot = VRM.getStackSlot(VirtReg);
+ const TargetRegisterClass *RC =
+ MBB.getParent()->getSSARegMap()->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 = TII->getTiedToSrcOperand(MI.getOpcode(), i);
+ if (TiedOp != -1)
+ PhysReg = MI.getOperand(TiedOp).getReg();
+ else
+ PhysReg = VRM.getPhys(VirtReg);
+
+ PhysRegsUsed[PhysReg] = true;
+ MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
+ DEBUG(std::cerr << "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);
+ VRM.RemoveFromFoldedVirtMap(&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 << "Removed dead store:\t" << *LastStore);
+ ++NumDSE;
+ MBB.erase(LastStore);
+ VRM.RemoveFromFoldedVirtMap(LastStore);
+ }
+ 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.ModifyStackSlot(StackSlot);
+ Spills.ClobberPhysReg(PhysReg);
+ Spills.addAvailable(StackSlot, PhysReg);
+ ++NumStores;
+ }
+ }
+ ProcessNextInst:
+ MII = NextMII;
+ }
}
+
llvm::Spiller* llvm::createSpiller() {
switch (SpillerOpt) {
default: assert(0 && "Unreachable!");
projects / oota-llvm.git / blobdiff