#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>
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");
+ 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());
}
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
}
void VirtRegMap::print(std::ostream &OS) const {
+ OStream LOS(OS);
+ print(LOS);
+}
+
+void VirtRegMap::print(OStream &OS) const {
const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
OS << "********** REGISTER MAP **********\n";
OS << '\n';
}
-void VirtRegMap::dump() const { print(std::cerr); }
+void VirtRegMap::dump() const {
+ OStream OS = DOUT;
+ print(OS);
+}
//===----------------------------------------------------------------------===//
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();
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) {
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()) {
}
}
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();
}
}
/// 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";
for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
MBB != E; ++MBB)
return true;
}
private:
- void RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM);
+ void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
void ClobberPhysReg(unsigned PR, std::map<int, unsigned> &SpillSlots,
- std::map<unsigned, int> &PhysRegs);
+ std::multimap<unsigned, int> &PhysRegs);
void ClobberPhysRegOnly(unsigned PR, std::map<int, unsigned> &SpillSlots,
- std::map<unsigned, int> &PhysRegs);
+ std::multimap<unsigned, int> &PhysRegs);
+ void ModifyStackSlot(int Slot, std::map<int, unsigned> &SpillSlots,
+ std::multimap<unsigned, int> &PhysRegs);
};
}
-void LocalSpiller::ClobberPhysRegOnly(unsigned PhysReg,
- std::map<int, unsigned> &SpillSlots,
- std::map<unsigned, int> &PhysRegs) {
- std::map<unsigned, int>::iterator I = PhysRegs.find(PhysReg);
- if (I != PhysRegs.end()) {
+/// 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 disallowClobberPhysRegOnly(unsigned PhysReg);
+
+ 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;
+
+ DOUT << "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;
+ }
+
+ /// 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.
+ 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);
+};
+}
+
+/// 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<unsigned, int>::iterator I =
+ PhysRegsAvailable.lower_bound(PhysReg);
+ while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
int Slot = I->second;
- PhysRegs.erase(I);
- assert(SpillSlots[Slot] == PhysReg && "Bidirectional map mismatch!");
- SpillSlots.erase(Slot);
- DEBUG(std::cerr << "PhysReg " << MRI->getName(PhysReg)
- << " clobbered, invalidating SS#" << Slot << "\n");
+ I++;
+ assert((SpillSlotsAvailable[Slot] >> 1) == PhysReg &&
+ "Bidirectional map mismatch!");
+ SpillSlotsAvailable[Slot] &= ~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<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);
+ DOUT << "PhysReg " << MRI->getName(PhysReg)
+ << " clobbered, invalidating SS#" << Slot << "\n";
}
}
-void LocalSpiller::ClobberPhysReg(unsigned PhysReg,
- std::map<int, unsigned> &SpillSlots,
- std::map<unsigned, int> &PhysRegs) {
+/// 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, SpillSlots, PhysRegs);
- ClobberPhysRegOnly(PhysReg, SpillSlots, PhysRegs);
+ 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;
+ }
+ PhysRegsAvailable.erase(I);
+}
+
+
// 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.
// 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;
+ bool *PhysRegsClobbered;
+ public:
+ ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
+ PhysRegsClobbered = new bool[mri->getNumRegs()];
+ std::fill(PhysRegsClobbered, PhysRegsClobbered+mri->getNumRegs(), false);
+ }
+ ~ReuseInfo() {
+ delete[] PhysRegsClobbered;
+ }
+
+ 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));
+ }
+
+ void markClobbered(unsigned PhysReg) {
+ PhysRegsClobbered[PhysReg] = true;
+ }
- ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr)
- : Operand(o), StackSlot(ss), PhysRegReused(prr), AssignedPhysReg(apr) {}
+ bool isClobbered(unsigned PhysReg) const {
+ return PhysRegsClobbered[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<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;
+ 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;
+ DOUT << '\t' << *prior(MII));
+
+ DOUT << "Reuse undone!\n";
+ --NumReused;
+
+ // Finally, PhysReg is now available, go ahead and use it.
+ return PhysReg;
+ }
+ }
+ }
+ return PhysReg;
+ }
};
}
/// 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) {
+void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
- // SpillSlotsAvailable - This map keeps track of all of the spilled virtual
- // register values that are still available, due to being loaded to stored to,
- // but not invalidated yet.
- std::map<int, unsigned> SpillSlotsAvailable;
-
- // PhysRegsAvailable - This is the inverse of SpillSlotsAvailable, indicating
- // which physregs are in use holding a stack slot value.
- std::map<unsigned, int> PhysRegsAvailable;
-
- DEBUG(std::cerr << MBB.getBasicBlock()->getName() << ":\n");
-
- std::vector<ReusedOp> ReusedOperands;
-
- // 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<std::pair<unsigned, unsigned> > DefAndUseVReg;
+ 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);
+
// 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
MachineInstr &MI = *MII;
MachineBasicBlock::iterator NextMII = MII; ++NextMII;
- ReusedOperands.clear();
- DefAndUseVReg.clear();
+ /// ReusedOperands - Keep track of operand reuse in case we need to undo
+ /// reuse.
+ ReuseInfo ReusedOperands(MI, MRI);
+
+ // Loop over all of the implicit defs, clearing them from our available
+ // sets.
+ const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
+ 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) {
// Ignore physregs for spilling, but remember that it is used by this
// function.
PhysRegsUsed[MO.getReg()] = true;
+ ReusedOperands.markClobbered(MO.getReg());
continue;
}
// 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;
}
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));
- }
-
int StackSlot = VRM.getStackSlot(VirtReg);
unsigned PhysReg;
// Check to see if this stack slot is available.
- std::map<int, unsigned>::iterator SSI =
- SpillSlotsAvailable.find(StackSlot);
- if (SSI != SpillSlotsAvailable.end()) {
- DEBUG(std::cerr << "Reusing SS#" << StackSlot << " from physreg "
- << MRI->getName(SSI->second) << " for vreg"
- << VirtReg <<" instead of reloading into physreg "
- << MRI->getName(VRM.getPhys(VirtReg)) << "\n");
- // If this stack slot value is already available, reuse it!
- PhysReg = SSI->second;
- 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.
+ 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 = 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 is 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!
+ DOUT << "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);
+ 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.push_back(ReusedOp(i, StackSlot, PhysReg,
- VRM.getPhys(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!
+ DOUT << "Reusing SS#" << StackSlot << " 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);
+
+ // This invalidates DesignatedReg.
+ Spills.ClobberPhysReg(DesignatedReg);
+
+ Spills.addAvailable(StackSlot, DesignatedReg);
+ MI.getOperand(i).setReg(DesignatedReg);
+ DOUT << '\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);
- RecheckRegister:
// 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.empty()) // This is most often empty.
- for (unsigned ro = 0, e = ReusedOperands.size(); ro != e; ++ro)
- if (ReusedOperands[ro].PhysRegReused == PhysReg) {
- // Yup, use the reload register that we didn't use before.
- PhysReg = ReusedOperands[ro].AssignedPhysReg;
- goto RecheckRegister;
- } else {
- ReusedOp &Op = ReusedOperands[ro];
- unsigned PRRU = Op.PhysRegReused;
- 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.
- MRI->loadRegFromStackSlot(MBB, &MI, Op.AssignedPhysReg,
- Op.StackSlot, RC);
- ClobberPhysReg(Op.AssignedPhysReg, SpillSlotsAvailable,
- PhysRegsAvailable);
-
- // Any stores to this stack slot are not dead anymore.
- MaybeDeadStores.erase(Op.StackSlot);
-
- MI.SetMachineOperandReg(Op.Operand, Op.AssignedPhysReg);
- PhysRegsAvailable[Op.AssignedPhysReg] = Op.StackSlot;
- SpillSlotsAvailable[Op.StackSlot] = Op.AssignedPhysReg;
- PhysRegsAvailable.erase(Op.PhysRegReused);
- DEBUG(std::cerr << "Remembering SS#" << Op.StackSlot
- << " in physreg "
- << MRI->getName(Op.AssignedPhysReg) << "\n");
- ++NumLoads;
- DEBUG(std::cerr << '\t' << *prior(MII));
-
- DEBUG(std::cerr << "Reuse undone!\n");
- ReusedOperands.erase(ReusedOperands.begin()+ro);
- --NumReused;
- goto ContinueReload;
- }
- }
- ContinueReload:
+ if (ReusedOperands.hasReuses())
+ PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
+ Spills, MaybeDeadStores);
+
PhysRegsUsed[PhysReg] = true;
+ ReusedOperands.markClobbered(PhysReg);
MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
// This invalidates PhysReg.
- ClobberPhysReg(PhysReg, SpillSlotsAvailable, PhysRegsAvailable);
+ Spills.ClobberPhysReg(PhysReg);
// Any stores to this stack slot are not dead anymore.
MaybeDeadStores.erase(StackSlot);
-
- MI.SetMachineOperandReg(i, PhysReg);
- PhysRegsAvailable[PhysReg] = StackSlot;
- SpillSlotsAvailable[StackSlot] = PhysReg;
- DEBUG(std::cerr << "Remembering SS#" << StackSlot <<" in physreg "
- << MRI->getName(PhysReg) << "\n");
+ Spills.addAvailable(StackSlot, PhysReg);
++NumLoads;
- DEBUG(std::cerr << '\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;
- ClobberPhysReg(*ImpDef, SpillSlotsAvailable, PhysRegsAvailable);
+ MI.getOperand(i).setReg(PhysReg);
+ DOUT << '\t' << *prior(MII);
}
- 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 = MRI->isLoadFromStackSlot(&MI, FrameIdx)) {
- // If this spill slot is available, insert a copy for it!
- std::map<int, unsigned>::iterator It = SpillSlotsAvailable.find(SS);
- if (FrameIdx == SS && It != SpillSlotsAvailable.end()) {
- DEBUG(std::cerr << "Promoted Load To Copy: " << MI);
- MachineFunction &MF = *MBB.getParent();
- if (DestReg != It->second) {
- MRI->copyRegToReg(MBB, &MI, DestReg, It->second,
- MF.getSSARegMap()->getRegClass(VirtReg));
- // Revisit the copy if the destination is a vreg.
- if (MRegisterInfo::isVirtualRegister(DestReg)) {
+ 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)) {
+ 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.
}
+ VRM.RemoveFromFoldedVirtMap(&MI);
+ MBB.erase(&MI);
+ goto ProcessNextInst;
}
- MBB.erase(&MI);
- goto ProcessNextInst;
}
}
}
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;
}
// 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) {
- std::map<int, unsigned>::iterator It = SpillSlotsAvailable.find(SS);
- if (It != SpillSlotsAvailable.end()) {
- PhysRegsAvailable.erase(It->second);
- SpillSlotsAvailable.erase(It);
+ // 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*/);
+ }
}
}
}
if (MO.isRegister() && MO.getReg() && MO.isDef()) {
unsigned VirtReg = MO.getReg();
- bool TakenCareOf = false;
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;
+ MBB.erase(&MI);
+ VRM.RemoveFromFoldedVirtMap(&MI);
+ Spills.disallowClobberPhysReg(VirtReg);
+ goto ProcessNextInst;
}
-
- if (!OpTakenCareOf) {
- ClobberPhysReg(VirtReg, SpillSlotsAvailable, PhysRegsAvailable);
- TakenCareOf = true;
+
+ // 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, DestReg);
+ goto ProcessNextInst;
}
+
+ continue;
}
- if (!TakenCareOf) {
- // 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)
- PhysReg = VRM.getPhys(VirtReg);
- else
- PhysReg = MO.getReg();
-
- PhysRegsUsed[PhysReg] = true;
- MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
- DEBUG(std::cerr << "Store:\t" << *next(MII));
- MI.SetMachineOperandReg(i, PhysReg);
-
- // 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);
- ++NumDSE;
- MBB.erase(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.
- std::map<int, unsigned>::iterator SSA =
- SpillSlotsAvailable.find(StackSlot);
- if (SSA != SpillSlotsAvailable.end()) {
- // Remove the record for physreg.
- PhysRegsAvailable.erase(SSA->second);
- SpillSlotsAvailable.erase(SSA);
+ // 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 = MI.getInstrDescriptor()->findTiedToSrcOperand(i);
+ if (TiedOp != -1)
+ PhysReg = MI.getOperand(TiedOp).getReg();
+ 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);
}
- ClobberPhysReg(PhysReg, SpillSlotsAvailable, PhysRegsAvailable);
-
- PhysRegsAvailable[PhysReg] = StackSlot;
- SpillSlotsAvailable[StackSlot] = PhysReg;
- DEBUG(std::cerr << "Updating SS#" << StackSlot <<" in physreg "
- << MRI->getName(PhysReg) << " for virtreg #"
- << VirtReg << "\n");
+ }
- ++NumStores;
- VirtReg = PhysReg;
+ PhysRegsUsed[PhysReg] = true;
+ ReusedOperands.markClobbered(PhysReg);
+ MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
+ 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;
+ DOUT << "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) {
+ DOUT << "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:
projects / oota-llvm.git / blobdiff