1 //===-- llvm/CodeGen/VirtRegMap.cpp - Virtual Register Map ----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the VirtRegMap class.
12 // It also contains implementations of the the Spiller interface, which, given a
13 // virtual register map and a machine function, eliminates all virtual
14 // references by replacing them with physical register references - adding spill
17 //===----------------------------------------------------------------------===//
19 #define DEBUG_TYPE "spiller"
20 #include "VirtRegMap.h"
21 #include "llvm/Function.h"
22 #include "llvm/CodeGen/MachineFrameInfo.h"
23 #include "llvm/CodeGen/MachineFunction.h"
24 #include "llvm/CodeGen/SSARegMap.h"
25 #include "llvm/Target/TargetMachine.h"
26 #include "llvm/Target/TargetInstrInfo.h"
27 #include "llvm/Support/CommandLine.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/Compiler.h"
30 #include "llvm/ADT/BitVector.h"
31 #include "llvm/ADT/Statistic.h"
32 #include "llvm/ADT/STLExtras.h"
33 #include "llvm/ADT/SmallSet.h"
37 STATISTIC(NumSpills, "Number of register spills");
38 STATISTIC(NumReMats, "Number of re-materialization");
39 STATISTIC(NumDRM , "Number of re-materializable defs elided");
40 STATISTIC(NumStores, "Number of stores added");
41 STATISTIC(NumLoads , "Number of loads added");
42 STATISTIC(NumReused, "Number of values reused");
43 STATISTIC(NumDSE , "Number of dead stores elided");
44 STATISTIC(NumDCE , "Number of copies elided");
47 enum SpillerName { simple, local };
49 static cl::opt<SpillerName>
51 cl::desc("Spiller to use: (default: local)"),
53 cl::values(clEnumVal(simple, " simple spiller"),
54 clEnumVal(local, " local spiller"),
59 //===----------------------------------------------------------------------===//
60 // VirtRegMap implementation
61 //===----------------------------------------------------------------------===//
63 VirtRegMap::VirtRegMap(MachineFunction &mf)
64 : TII(*mf.getTarget().getInstrInfo()), MF(mf),
65 Virt2PhysMap(NO_PHYS_REG), Virt2StackSlotMap(NO_STACK_SLOT),
66 Virt2ReMatIdMap(NO_STACK_SLOT), ReMatMap(NULL),
67 ReMatId(MAX_STACK_SLOT+1) {
71 void VirtRegMap::grow() {
72 unsigned LastVirtReg = MF.getSSARegMap()->getLastVirtReg();
73 Virt2PhysMap.grow(LastVirtReg);
74 Virt2StackSlotMap.grow(LastVirtReg);
75 Virt2ReMatIdMap.grow(LastVirtReg);
76 ReMatMap.grow(LastVirtReg);
79 int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
80 assert(MRegisterInfo::isVirtualRegister(virtReg));
81 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
82 "attempt to assign stack slot to already spilled register");
83 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(virtReg);
84 int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
86 Virt2StackSlotMap[virtReg] = frameIndex;
91 void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) {
92 assert(MRegisterInfo::isVirtualRegister(virtReg));
93 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
94 "attempt to assign stack slot to already spilled register");
95 assert((frameIndex >= 0 ||
96 (frameIndex >= MF.getFrameInfo()->getObjectIndexBegin())) &&
97 "illegal fixed frame index");
98 Virt2StackSlotMap[virtReg] = frameIndex;
101 int VirtRegMap::assignVirtReMatId(unsigned virtReg) {
102 assert(MRegisterInfo::isVirtualRegister(virtReg));
103 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
104 "attempt to assign re-mat id to already spilled register");
105 Virt2ReMatIdMap[virtReg] = ReMatId;
109 void VirtRegMap::assignVirtReMatId(unsigned virtReg, int id) {
110 assert(MRegisterInfo::isVirtualRegister(virtReg));
111 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
112 "attempt to assign re-mat id to already spilled register");
113 Virt2ReMatIdMap[virtReg] = id;
116 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
117 unsigned OpNo, MachineInstr *NewMI) {
118 // Move previous memory references folded to new instruction.
119 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
120 for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
121 E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
122 MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
123 MI2VirtMap.erase(I++);
127 const TargetInstrDescriptor *TID = OldMI->getInstrDescriptor();
128 if (TID->getOperandConstraint(OpNo, TOI::TIED_TO) != -1 ||
129 TID->findTiedToSrcOperand(OpNo) != -1) {
130 // Folded a two-address operand.
132 } else if (OldMI->getOperand(OpNo).isDef()) {
138 // add new memory reference
139 MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
142 void VirtRegMap::print(std::ostream &OS) const {
143 const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
145 OS << "********** REGISTER MAP **********\n";
146 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
147 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) {
148 if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG)
149 OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n";
153 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
154 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i)
155 if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT)
156 OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n";
160 void VirtRegMap::dump() const {
165 //===----------------------------------------------------------------------===//
166 // Simple Spiller Implementation
167 //===----------------------------------------------------------------------===//
169 Spiller::~Spiller() {}
172 struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller {
173 bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM);
177 bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
178 DOUT << "********** REWRITE MACHINE CODE **********\n";
179 DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
180 const TargetMachine &TM = MF.getTarget();
181 const MRegisterInfo &MRI = *TM.getRegisterInfo();
183 // LoadedRegs - Keep track of which vregs are loaded, so that we only load
184 // each vreg once (in the case where a spilled vreg is used by multiple
185 // operands). This is always smaller than the number of operands to the
186 // current machine instr, so it should be small.
187 std::vector<unsigned> LoadedRegs;
189 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
191 DOUT << MBBI->getBasicBlock()->getName() << ":\n";
192 MachineBasicBlock &MBB = *MBBI;
193 for (MachineBasicBlock::iterator MII = MBB.begin(),
194 E = MBB.end(); MII != E; ++MII) {
195 MachineInstr &MI = *MII;
196 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
197 MachineOperand &MO = MI.getOperand(i);
198 if (MO.isRegister() && MO.getReg())
199 if (MRegisterInfo::isVirtualRegister(MO.getReg())) {
200 unsigned VirtReg = MO.getReg();
201 unsigned PhysReg = VRM.getPhys(VirtReg);
202 if (!VRM.isAssignedReg(VirtReg)) {
203 int StackSlot = VRM.getStackSlot(VirtReg);
204 const TargetRegisterClass* RC =
205 MF.getSSARegMap()->getRegClass(VirtReg);
208 std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
209 == LoadedRegs.end()) {
210 MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
211 LoadedRegs.push_back(VirtReg);
213 DOUT << '\t' << *prior(MII);
217 MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
221 MF.setPhysRegUsed(PhysReg);
222 MI.getOperand(i).setReg(PhysReg);
224 MF.setPhysRegUsed(MO.getReg());
235 //===----------------------------------------------------------------------===//
236 // Local Spiller Implementation
237 //===----------------------------------------------------------------------===//
240 /// LocalSpiller - This spiller does a simple pass over the machine basic
241 /// block to attempt to keep spills in registers as much as possible for
242 /// blocks that have low register pressure (the vreg may be spilled due to
243 /// register pressure in other blocks).
244 class VISIBILITY_HIDDEN LocalSpiller : public Spiller {
246 const MRegisterInfo *MRI;
247 const TargetInstrInfo *TII;
249 bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
250 RegMap = MF.getSSARegMap();
251 MRI = MF.getTarget().getRegisterInfo();
252 TII = MF.getTarget().getInstrInfo();
253 DOUT << "\n**** Local spiller rewriting function '"
254 << MF.getFunction()->getName() << "':\n";
255 DOUT << "**** Machine Instrs (NOTE! Does not include spills and reloads!) ****\n";
258 for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
260 RewriteMBB(*MBB, VRM);
262 DOUT << "**** Post Machine Instrs ****\n";
268 void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
272 /// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
273 /// top down, keep track of which spills slots or remat are available in each
276 /// Note that not all physregs are created equal here. In particular, some
277 /// physregs are reloads that we are allowed to clobber or ignore at any time.
278 /// Other physregs are values that the register allocated program is using that
279 /// we cannot CHANGE, but we can read if we like. We keep track of this on a
280 /// per-stack-slot / remat id basis as the low bit in the value of the
281 /// SpillSlotsAvailable entries. The predicate 'canClobberPhysReg()' checks
282 /// this bit and addAvailable sets it if.
284 class VISIBILITY_HIDDEN AvailableSpills {
285 const MRegisterInfo *MRI;
286 const TargetInstrInfo *TII;
288 // SpillSlotsOrReMatsAvailable - This map keeps track of all of the spilled
289 // or remat'ed virtual register values that are still available, due to being
290 // loaded or stored to, but not invalidated yet.
291 std::map<int, unsigned> SpillSlotsOrReMatsAvailable;
293 // PhysRegsAvailable - This is the inverse of SpillSlotsOrReMatsAvailable,
294 // indicating which stack slot values are currently held by a physreg. This
295 // is used to invalidate entries in SpillSlotsOrReMatsAvailable when a
296 // physreg is modified.
297 std::multimap<unsigned, int> PhysRegsAvailable;
299 void disallowClobberPhysRegOnly(unsigned PhysReg);
301 void ClobberPhysRegOnly(unsigned PhysReg);
303 AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
304 : MRI(mri), TII(tii) {
307 const MRegisterInfo *getRegInfo() const { return MRI; }
309 /// getSpillSlotOrReMatPhysReg - If the specified stack slot or remat is
310 /// available in a physical register, return that PhysReg, otherwise
312 unsigned getSpillSlotOrReMatPhysReg(int Slot) const {
313 std::map<int, unsigned>::const_iterator I =
314 SpillSlotsOrReMatsAvailable.find(Slot);
315 if (I != SpillSlotsOrReMatsAvailable.end()) {
316 return I->second >> 1; // Remove the CanClobber bit.
321 /// addAvailable - Mark that the specified stack slot / remat is available in
322 /// the specified physreg. If CanClobber is true, the physreg can be modified
323 /// at any time without changing the semantics of the program.
324 void addAvailable(int SlotOrReMat, MachineInstr *MI, unsigned Reg,
325 bool CanClobber = true) {
326 // If this stack slot is thought to be available in some other physreg,
327 // remove its record.
328 ModifyStackSlotOrReMat(SlotOrReMat);
330 PhysRegsAvailable.insert(std::make_pair(Reg, SlotOrReMat));
331 SpillSlotsOrReMatsAvailable[SlotOrReMat]= (Reg << 1) | (unsigned)CanClobber;
333 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
334 DOUT << "Remembering RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1;
336 DOUT << "Remembering SS#" << SlotOrReMat;
337 DOUT << " in physreg " << MRI->getName(Reg) << "\n";
340 /// canClobberPhysReg - Return true if the spiller is allowed to change the
341 /// value of the specified stackslot register if it desires. The specified
342 /// stack slot must be available in a physreg for this query to make sense.
343 bool canClobberPhysReg(int SlotOrReMat) const {
344 assert(SpillSlotsOrReMatsAvailable.count(SlotOrReMat) &&
345 "Value not available!");
346 return SpillSlotsOrReMatsAvailable.find(SlotOrReMat)->second & 1;
349 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
350 /// stackslot register. The register is still available but is no longer
351 /// allowed to be modifed.
352 void disallowClobberPhysReg(unsigned PhysReg);
354 /// ClobberPhysReg - This is called when the specified physreg changes
355 /// value. We use this to invalidate any info about stuff we thing lives in
356 /// it and any of its aliases.
357 void ClobberPhysReg(unsigned PhysReg);
359 /// ModifyStackSlotOrReMat - This method is called when the value in a stack
360 /// slot changes. This removes information about which register the previous
361 /// value for this slot lives in (as the previous value is dead now).
362 void ModifyStackSlotOrReMat(int SlotOrReMat);
366 /// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
367 /// stackslot register. The register is still available but is no longer
368 /// allowed to be modifed.
369 void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
370 std::multimap<unsigned, int>::iterator I =
371 PhysRegsAvailable.lower_bound(PhysReg);
372 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
373 int SlotOrReMat = I->second;
375 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
376 "Bidirectional map mismatch!");
377 SpillSlotsOrReMatsAvailable[SlotOrReMat] &= ~1;
378 DOUT << "PhysReg " << MRI->getName(PhysReg)
379 << " copied, it is available for use but can no longer be modified\n";
383 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
384 /// stackslot register and its aliases. The register and its aliases may
385 /// still available but is no longer allowed to be modifed.
386 void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
387 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
388 disallowClobberPhysRegOnly(*AS);
389 disallowClobberPhysRegOnly(PhysReg);
392 /// ClobberPhysRegOnly - This is called when the specified physreg changes
393 /// value. We use this to invalidate any info about stuff we thing lives in it.
394 void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
395 std::multimap<unsigned, int>::iterator I =
396 PhysRegsAvailable.lower_bound(PhysReg);
397 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
398 int SlotOrReMat = I->second;
399 PhysRegsAvailable.erase(I++);
400 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
401 "Bidirectional map mismatch!");
402 SpillSlotsOrReMatsAvailable.erase(SlotOrReMat);
403 DOUT << "PhysReg " << MRI->getName(PhysReg)
404 << " clobbered, invalidating ";
405 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
406 DOUT << "RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1 << "\n";
408 DOUT << "SS#" << SlotOrReMat << "\n";
412 /// ClobberPhysReg - This is called when the specified physreg changes
413 /// value. We use this to invalidate any info about stuff we thing lives in
414 /// it and any of its aliases.
415 void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
416 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
417 ClobberPhysRegOnly(*AS);
418 ClobberPhysRegOnly(PhysReg);
421 /// ModifyStackSlotOrReMat - This method is called when the value in a stack
422 /// slot changes. This removes information about which register the previous
423 /// value for this slot lives in (as the previous value is dead now).
424 void AvailableSpills::ModifyStackSlotOrReMat(int SlotOrReMat) {
425 std::map<int, unsigned>::iterator It =
426 SpillSlotsOrReMatsAvailable.find(SlotOrReMat);
427 if (It == SpillSlotsOrReMatsAvailable.end()) return;
428 unsigned Reg = It->second >> 1;
429 SpillSlotsOrReMatsAvailable.erase(It);
431 // This register may hold the value of multiple stack slots, only remove this
432 // stack slot from the set of values the register contains.
433 std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
435 assert(I != PhysRegsAvailable.end() && I->first == Reg &&
436 "Map inverse broken!");
437 if (I->second == SlotOrReMat) break;
439 PhysRegsAvailable.erase(I);
444 /// InvalidateKills - MI is going to be deleted. If any of its operands are
445 /// marked kill, then invalidate the information.
446 static void InvalidateKills(MachineInstr &MI, BitVector &RegKills,
447 std::vector<MachineOperand*> &KillOps,
448 SmallVector<unsigned, 1> *KillRegs = NULL) {
449 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
450 MachineOperand &MO = MI.getOperand(i);
451 if (!MO.isRegister() || !MO.isUse() || !MO.isKill())
453 unsigned Reg = MO.getReg();
455 KillRegs->push_back(Reg);
456 if (KillOps[Reg] == &MO) {
463 /// InvalidateRegDef - If the def operand of the specified def MI is now dead
464 /// (since it's spill instruction is removed), mark it isDead. Also checks if
465 /// the def MI has other definition operands that are not dead. Returns it by
467 static bool InvalidateRegDef(MachineBasicBlock::iterator I,
468 MachineInstr &NewDef, unsigned Reg,
470 // Due to remat, it's possible this reg isn't being reused. That is,
471 // the def of this reg (by prev MI) is now dead.
472 MachineInstr *DefMI = I;
473 MachineOperand *DefOp = NULL;
474 for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) {
475 MachineOperand &MO = DefMI->getOperand(i);
476 if (MO.isRegister() && MO.isDef()) {
477 if (MO.getReg() == Reg)
479 else if (!MO.isDead())
486 bool FoundUse = false, Done = false;
487 MachineBasicBlock::iterator E = NewDef;
489 for (; !Done && I != E; ++I) {
490 MachineInstr *NMI = I;
491 for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) {
492 MachineOperand &MO = NMI->getOperand(j);
493 if (!MO.isRegister() || MO.getReg() != Reg)
497 Done = true; // Stop after scanning all the operands of this MI.
508 /// UpdateKills - Track and update kill info. If a MI reads a register that is
509 /// marked kill, then it must be due to register reuse. Transfer the kill info
511 static void UpdateKills(MachineInstr &MI, BitVector &RegKills,
512 std::vector<MachineOperand*> &KillOps) {
513 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
514 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
515 MachineOperand &MO = MI.getOperand(i);
516 if (!MO.isRegister() || !MO.isUse())
518 unsigned Reg = MO.getReg();
523 // That can't be right. Register is killed but not re-defined and it's
524 // being reused. Let's fix that.
525 KillOps[Reg]->unsetIsKill();
526 if (i < TID->numOperands &&
527 TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
528 // Unless it's a two-address operand, this is the new kill.
538 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
539 const MachineOperand &MO = MI.getOperand(i);
540 if (!MO.isRegister() || !MO.isDef())
542 unsigned Reg = MO.getReg();
549 // ReusedOp - For each reused operand, we keep track of a bit of information, in
550 // case we need to rollback upon processing a new operand. See comments below.
553 // The MachineInstr operand that reused an available value.
556 // StackSlotOrReMat - The spill slot or remat id of the value being reused.
557 unsigned StackSlotOrReMat;
559 // PhysRegReused - The physical register the value was available in.
560 unsigned PhysRegReused;
562 // AssignedPhysReg - The physreg that was assigned for use by the reload.
563 unsigned AssignedPhysReg;
565 // VirtReg - The virtual register itself.
568 ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
570 : Operand(o), StackSlotOrReMat(ss), PhysRegReused(prr),
571 AssignedPhysReg(apr), VirtReg(vreg) {}
574 /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
575 /// is reused instead of reloaded.
576 class VISIBILITY_HIDDEN ReuseInfo {
578 std::vector<ReusedOp> Reuses;
579 BitVector PhysRegsClobbered;
581 ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
582 PhysRegsClobbered.resize(mri->getNumRegs());
585 bool hasReuses() const {
586 return !Reuses.empty();
589 /// addReuse - If we choose to reuse a virtual register that is already
590 /// available instead of reloading it, remember that we did so.
591 void addReuse(unsigned OpNo, unsigned StackSlotOrReMat,
592 unsigned PhysRegReused, unsigned AssignedPhysReg,
594 // If the reload is to the assigned register anyway, no undo will be
596 if (PhysRegReused == AssignedPhysReg) return;
598 // Otherwise, remember this.
599 Reuses.push_back(ReusedOp(OpNo, StackSlotOrReMat, PhysRegReused,
600 AssignedPhysReg, VirtReg));
603 void markClobbered(unsigned PhysReg) {
604 PhysRegsClobbered.set(PhysReg);
607 bool isClobbered(unsigned PhysReg) const {
608 return PhysRegsClobbered.test(PhysReg);
611 /// GetRegForReload - We are about to emit a reload into PhysReg. If there
612 /// is some other operand that is using the specified register, either pick
613 /// a new register to use, or evict the previous reload and use this reg.
614 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
615 AvailableSpills &Spills,
616 std::vector<MachineInstr*> &MaybeDeadStores,
617 SmallSet<unsigned, 8> &Rejected,
619 std::vector<MachineOperand*> &KillOps,
621 if (Reuses.empty()) return PhysReg; // This is most often empty.
623 for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
624 ReusedOp &Op = Reuses[ro];
625 // If we find some other reuse that was supposed to use this register
626 // exactly for its reload, we can change this reload to use ITS reload
627 // register. That is, unless its reload register has already been
628 // considered and subsequently rejected because it has also been reused
629 // by another operand.
630 if (Op.PhysRegReused == PhysReg &&
631 Rejected.count(Op.AssignedPhysReg) == 0) {
632 // Yup, use the reload register that we didn't use before.
633 unsigned NewReg = Op.AssignedPhysReg;
634 Rejected.insert(PhysReg);
635 return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected,
636 RegKills, KillOps, VRM);
638 // Otherwise, we might also have a problem if a previously reused
639 // value aliases the new register. If so, codegen the previous reload
641 unsigned PRRU = Op.PhysRegReused;
642 const MRegisterInfo *MRI = Spills.getRegInfo();
643 if (MRI->areAliases(PRRU, PhysReg)) {
644 // Okay, we found out that an alias of a reused register
645 // was used. This isn't good because it means we have
646 // to undo a previous reuse.
647 MachineBasicBlock *MBB = MI->getParent();
648 const TargetRegisterClass *AliasRC =
649 MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
651 // Copy Op out of the vector and remove it, we're going to insert an
652 // explicit load for it.
654 Reuses.erase(Reuses.begin()+ro);
656 // Ok, we're going to try to reload the assigned physreg into the
657 // slot that we were supposed to in the first place. However, that
658 // register could hold a reuse. Check to see if it conflicts or
659 // would prefer us to use a different register.
660 unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
661 MI, Spills, MaybeDeadStores,
662 Rejected, RegKills, KillOps, VRM);
664 if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) {
665 MRI->reMaterialize(*MBB, MI, NewPhysReg,
666 VRM.getReMaterializedMI(NewOp.VirtReg));
669 MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg,
670 NewOp.StackSlotOrReMat, AliasRC);
671 // Any stores to this stack slot are not dead anymore.
672 MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL;
675 Spills.ClobberPhysReg(NewPhysReg);
676 Spills.ClobberPhysReg(NewOp.PhysRegReused);
678 MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
680 Spills.addAvailable(NewOp.StackSlotOrReMat, MI, NewPhysReg);
681 MachineBasicBlock::iterator MII = MI;
683 UpdateKills(*MII, RegKills, KillOps);
684 DOUT << '\t' << *MII;
686 DOUT << "Reuse undone!\n";
689 // Finally, PhysReg is now available, go ahead and use it.
697 /// GetRegForReload - Helper for the above GetRegForReload(). Add a
698 /// 'Rejected' set to remember which registers have been considered and
699 /// rejected for the reload. This avoids infinite looping in case like
702 /// t2 <- assigned r0 for use by the reload but ended up reuse r1
703 /// t3 <- assigned r1 for use by the reload but ended up reuse r0
705 /// sees r1 is taken by t2, tries t2's reload register r0
706 /// sees r0 is taken by t3, tries t3's reload register r1
707 /// sees r1 is taken by t2, tries t2's reload register r0 ...
708 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
709 AvailableSpills &Spills,
710 std::vector<MachineInstr*> &MaybeDeadStores,
712 std::vector<MachineOperand*> &KillOps,
714 SmallSet<unsigned, 8> Rejected;
715 return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected,
716 RegKills, KillOps, VRM);
722 /// rewriteMBB - Keep track of which spills are available even after the
723 /// register allocator is done with them. If possible, avoid reloading vregs.
724 void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
725 DOUT << MBB.getBasicBlock()->getName() << ":\n";
727 MachineFunction &MF = *MBB.getParent();
729 // Spills - Keep track of which spilled values are available in physregs so
730 // that we can choose to reuse the physregs instead of emitting reloads.
731 AvailableSpills Spills(MRI, TII);
733 // MaybeDeadStores - When we need to write a value back into a stack slot,
734 // keep track of the inserted store. If the stack slot value is never read
735 // (because the value was used from some available register, for example), and
736 // subsequently stored to, the original store is dead. This map keeps track
737 // of inserted stores that are not used. If we see a subsequent store to the
738 // same stack slot, the original store is deleted.
739 std::vector<MachineInstr*> MaybeDeadStores;
740 MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL);
742 // ReMatDefs - These are rematerializable def MIs which are not deleted.
743 SmallSet<MachineInstr*, 4> ReMatDefs;
745 // Keep track of kill information.
746 BitVector RegKills(MRI->getNumRegs());
747 std::vector<MachineOperand*> KillOps;
748 KillOps.resize(MRI->getNumRegs(), NULL);
750 for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
752 MachineInstr &MI = *MII;
753 MachineBasicBlock::iterator NextMII = MII; ++NextMII;
754 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
757 bool BackTracked = false;
759 /// ReusedOperands - Keep track of operand reuse in case we need to undo
761 ReuseInfo ReusedOperands(MI, MRI);
763 // Loop over all of the implicit defs, clearing them from our available
765 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
766 if (TID->ImplicitDefs) {
767 const unsigned *ImpDef = TID->ImplicitDefs;
768 for ( ; *ImpDef; ++ImpDef) {
769 MF.setPhysRegUsed(*ImpDef);
770 ReusedOperands.markClobbered(*ImpDef);
771 Spills.ClobberPhysReg(*ImpDef);
775 // Process all of the spilled uses and all non spilled reg references.
776 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
777 MachineOperand &MO = MI.getOperand(i);
778 if (!MO.isRegister() || MO.getReg() == 0)
779 continue; // Ignore non-register operands.
781 unsigned VirtReg = MO.getReg();
782 if (MRegisterInfo::isPhysicalRegister(VirtReg)) {
783 // Ignore physregs for spilling, but remember that it is used by this
785 MF.setPhysRegUsed(VirtReg);
786 ReusedOperands.markClobbered(VirtReg);
790 assert(MRegisterInfo::isVirtualRegister(VirtReg) &&
791 "Not a virtual or a physical register?");
794 bool isSubReg = RegMap->isSubRegister(VirtReg);
796 SubIdx = RegMap->getSubRegisterIndex(VirtReg);
797 VirtReg = RegMap->getSuperRegister(VirtReg);
800 if (VRM.isAssignedReg(VirtReg)) {
801 // This virtual register was assigned a physreg!
802 unsigned Phys = VRM.getPhys(VirtReg);
803 MF.setPhysRegUsed(Phys);
805 ReusedOperands.markClobbered(Phys);
806 unsigned RReg = isSubReg ? MRI->getSubReg(Phys, SubIdx) : Phys;
807 MI.getOperand(i).setReg(RReg);
811 // This virtual register is now known to be a spilled value.
813 continue; // Handle defs in the loop below (handle use&def here though)
815 bool DoReMat = VRM.isReMaterialized(VirtReg);
816 int SSorRMId = DoReMat
817 ? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
818 int ReuseSlot = SSorRMId;
820 // Check to see if this stack slot is available.
821 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
822 if (!PhysReg && DoReMat) {
823 // This use is rematerializable. But perhaps the value is available in
824 // stack if the definition is not deleted. If so, check if we can
826 ReuseSlot = VRM.getStackSlot(VirtReg);
827 if (ReuseSlot != VirtRegMap::NO_STACK_SLOT)
828 PhysReg = Spills.getSpillSlotOrReMatPhysReg(ReuseSlot);
831 // If this is a sub-register use, make sure the reuse register is in the
832 // right register class. For example, for x86 not all of the 32-bit
833 // registers have accessible sub-registers.
834 // Similarly so for EXTRACT_SUBREG. Consider this:
836 // MOV32_mr fi#1, EDI
838 // = EXTRACT_SUBREG fi#1
839 // fi#1 is available in EDI, but it cannot be reused because it's not in
840 // the right register file.
842 (isSubReg || MI.getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)) {
843 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
844 if (!RC->contains(PhysReg))
849 // This spilled operand might be part of a two-address operand. If this
850 // is the case, then changing it will necessarily require changing the
851 // def part of the instruction as well. However, in some cases, we
852 // aren't allowed to modify the reused register. If none of these cases
854 bool CanReuse = true;
856 int ti = TID->getOperandConstraint(i, TOI::TIED_TO);
858 MI.getOperand(ti).isRegister() &&
859 MI.getOperand(ti).getReg() == VirtReg) {
860 // Okay, we have a two address operand. We can reuse this physreg as
861 // long as we are allowed to clobber the value and there isn't an
862 // earlier def that has already clobbered the physreg.
863 CanReuse = Spills.canClobberPhysReg(ReuseSlot) &&
864 !ReusedOperands.isClobbered(PhysReg);
868 // If this stack slot value is already available, reuse it!
869 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
870 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
872 DOUT << "Reusing SS#" << ReuseSlot;
873 DOUT << " from physreg "
874 << MRI->getName(PhysReg) << " for vreg"
875 << VirtReg <<" instead of reloading into physreg "
876 << MRI->getName(VRM.getPhys(VirtReg)) << "\n";
877 unsigned RReg = isSubReg ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
878 MI.getOperand(i).setReg(RReg);
880 // The only technical detail we have is that we don't know that
881 // PhysReg won't be clobbered by a reloaded stack slot that occurs
882 // later in the instruction. In particular, consider 'op V1, V2'.
883 // If V1 is available in physreg R0, we would choose to reuse it
884 // here, instead of reloading it into the register the allocator
885 // indicated (say R1). However, V2 might have to be reloaded
886 // later, and it might indicate that it needs to live in R0. When
887 // this occurs, we need to have information available that
888 // indicates it is safe to use R1 for the reload instead of R0.
890 // To further complicate matters, we might conflict with an alias,
891 // or R0 and R1 might not be compatible with each other. In this
892 // case, we actually insert a reload for V1 in R1, ensuring that
893 // we can get at R0 or its alias.
894 ReusedOperands.addReuse(i, ReuseSlot, PhysReg,
895 VRM.getPhys(VirtReg), VirtReg);
897 // Only mark it clobbered if this is a use&def operand.
898 ReusedOperands.markClobbered(PhysReg);
901 if (MI.getOperand(i).isKill() &&
902 ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) {
903 // This was the last use and the spilled value is still available
904 // for reuse. That means the spill was unnecessary!
905 MachineInstr* DeadStore = MaybeDeadStores[ReuseSlot];
907 DOUT << "Removed dead store:\t" << *DeadStore;
908 InvalidateKills(*DeadStore, RegKills, KillOps);
909 MBB.erase(DeadStore);
910 VRM.RemoveFromFoldedVirtMap(DeadStore);
911 MaybeDeadStores[ReuseSlot] = NULL;
918 // Otherwise we have a situation where we have a two-address instruction
919 // whose mod/ref operand needs to be reloaded. This reload is already
920 // available in some register "PhysReg", but if we used PhysReg as the
921 // operand to our 2-addr instruction, the instruction would modify
922 // PhysReg. This isn't cool if something later uses PhysReg and expects
923 // to get its initial value.
925 // To avoid this problem, and to avoid doing a load right after a store,
926 // we emit a copy from PhysReg into the designated register for this
928 unsigned DesignatedReg = VRM.getPhys(VirtReg);
929 assert(DesignatedReg && "Must map virtreg to physreg!");
931 // Note that, if we reused a register for a previous operand, the
932 // register we want to reload into might not actually be
933 // available. If this occurs, use the register indicated by the
935 if (ReusedOperands.hasReuses())
936 DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
937 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
939 // If the mapped designated register is actually the physreg we have
940 // incoming, we don't need to inserted a dead copy.
941 if (DesignatedReg == PhysReg) {
942 // If this stack slot value is already available, reuse it!
943 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
944 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
946 DOUT << "Reusing SS#" << ReuseSlot;
947 DOUT << " from physreg " << MRI->getName(PhysReg) << " for vreg"
949 << " instead of reloading into same physreg.\n";
950 unsigned RReg = isSubReg ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
951 MI.getOperand(i).setReg(RReg);
952 ReusedOperands.markClobbered(PhysReg);
957 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
958 MF.setPhysRegUsed(DesignatedReg);
959 ReusedOperands.markClobbered(DesignatedReg);
960 MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC, RC);
962 MachineInstr *CopyMI = prior(MII);
963 UpdateKills(*CopyMI, RegKills, KillOps);
965 // This invalidates DesignatedReg.
966 Spills.ClobberPhysReg(DesignatedReg);
968 Spills.addAvailable(ReuseSlot, &MI, DesignatedReg);
970 isSubReg ? MRI->getSubReg(DesignatedReg, SubIdx) : DesignatedReg;
971 MI.getOperand(i).setReg(RReg);
972 DOUT << '\t' << *prior(MII);
977 // Otherwise, reload it and remember that we have it.
978 PhysReg = VRM.getPhys(VirtReg);
979 assert(PhysReg && "Must map virtreg to physreg!");
981 // Note that, if we reused a register for a previous operand, the
982 // register we want to reload into might not actually be
983 // available. If this occurs, use the register indicated by the
985 if (ReusedOperands.hasReuses())
986 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
987 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
989 MF.setPhysRegUsed(PhysReg);
990 ReusedOperands.markClobbered(PhysReg);
992 MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg));
995 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
996 MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, SSorRMId, RC);
999 // This invalidates PhysReg.
1000 Spills.ClobberPhysReg(PhysReg);
1002 // Any stores to this stack slot are not dead anymore.
1004 MaybeDeadStores[SSorRMId] = NULL;
1005 Spills.addAvailable(SSorRMId, &MI, PhysReg);
1006 // Assumes this is the last use. IsKill will be unset if reg is reused
1007 // unless it's a two-address operand.
1008 if (TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
1009 MI.getOperand(i).setIsKill();
1010 unsigned RReg = isSubReg ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
1011 MI.getOperand(i).setReg(RReg);
1012 UpdateKills(*prior(MII), RegKills, KillOps);
1013 DOUT << '\t' << *prior(MII);
1018 // If we have folded references to memory operands, make sure we clear all
1019 // physical registers that may contain the value of the spilled virtual
1021 SmallSet<int, 1> FoldedSS;
1022 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
1023 DOUT << "Folded vreg: " << I->second.first << " MR: "
1024 << I->second.second;
1025 unsigned VirtReg = I->second.first;
1026 VirtRegMap::ModRef MR = I->second.second;
1027 if (VRM.isAssignedReg(VirtReg)) {
1028 DOUT << ": No stack slot!\n";
1031 int SS = VRM.getStackSlot(VirtReg);
1032 FoldedSS.insert(SS);
1033 DOUT << " - StackSlot: " << SS << "\n";
1035 // If this folded instruction is just a use, check to see if it's a
1036 // straight load from the virt reg slot.
1037 if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
1039 unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx);
1040 if (DestReg && FrameIdx == SS) {
1041 // If this spill slot is available, turn it into a copy (or nothing)
1042 // instead of leaving it as a load!
1043 if (unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SS)) {
1044 DOUT << "Promoted Load To Copy: " << MI;
1045 if (DestReg != InReg) {
1046 const TargetRegisterClass *RC = RegMap->getRegClass(VirtReg);
1047 MRI->copyRegToReg(MBB, &MI, DestReg, InReg, RC, RC);
1048 // Revisit the copy so we make sure to notice the effects of the
1049 // operation on the destreg (either needing to RA it if it's
1050 // virtual or needing to clobber any values if it's physical).
1052 --NextMII; // backtrack to the copy.
1055 DOUT << "Removing now-noop copy: " << MI;
1057 VRM.RemoveFromFoldedVirtMap(&MI);
1060 goto ProcessNextInst;
1065 // If this reference is not a use, any previous store is now dead.
1066 // Otherwise, the store to this stack slot is not dead anymore.
1067 MachineInstr* DeadStore = MaybeDeadStores[SS];
1069 if (!(MR & VirtRegMap::isRef)) { // Previous store is dead.
1070 // If we get here, the store is dead, nuke it now.
1071 assert(VirtRegMap::isMod && "Can't be modref!");
1072 DOUT << "Removed dead store:\t" << *DeadStore;
1073 InvalidateKills(*DeadStore, RegKills, KillOps);
1074 MBB.erase(DeadStore);
1075 VRM.RemoveFromFoldedVirtMap(DeadStore);
1078 MaybeDeadStores[SS] = NULL;
1081 // If the spill slot value is available, and this is a new definition of
1082 // the value, the value is not available anymore.
1083 if (MR & VirtRegMap::isMod) {
1084 // Notice that the value in this stack slot has been modified.
1085 Spills.ModifyStackSlotOrReMat(SS);
1087 // If this is *just* a mod of the value, check to see if this is just a
1088 // store to the spill slot (i.e. the spill got merged into the copy). If
1089 // so, realize that the vreg is available now, and add the store to the
1090 // MaybeDeadStore info.
1092 if (!(MR & VirtRegMap::isRef)) {
1093 if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
1094 assert(MRegisterInfo::isPhysicalRegister(SrcReg) &&
1095 "Src hasn't been allocated yet?");
1096 // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
1097 // this as a potentially dead store in case there is a subsequent
1098 // store into the stack slot without a read from it.
1099 MaybeDeadStores[StackSlot] = &MI;
1101 // If the stack slot value was previously available in some other
1102 // register, change it now. Otherwise, make the register available,
1104 Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/);
1110 // Process all of the spilled defs.
1111 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
1112 MachineOperand &MO = MI.getOperand(i);
1113 if (MO.isRegister() && MO.getReg() && MO.isDef()) {
1114 unsigned VirtReg = MO.getReg();
1116 if (!MRegisterInfo::isVirtualRegister(VirtReg)) {
1117 // Check to see if this is a noop copy. If so, eliminate the
1118 // instruction before considering the dest reg to be changed.
1120 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1122 DOUT << "Removing now-noop copy: " << MI;
1125 VRM.RemoveFromFoldedVirtMap(&MI);
1126 Spills.disallowClobberPhysReg(VirtReg);
1127 goto ProcessNextInst;
1130 // If it's not a no-op copy, it clobbers the value in the destreg.
1131 Spills.ClobberPhysReg(VirtReg);
1132 ReusedOperands.markClobbered(VirtReg);
1134 // Check to see if this instruction is a load from a stack slot into
1135 // a register. If so, this provides the stack slot value in the reg.
1137 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
1138 assert(DestReg == VirtReg && "Unknown load situation!");
1140 // If it is a folded reference, then it's not safe to clobber.
1141 bool Folded = FoldedSS.count(FrameIdx);
1142 // Otherwise, if it wasn't available, remember that it is now!
1143 Spills.addAvailable(FrameIdx, &MI, DestReg, !Folded);
1144 goto ProcessNextInst;
1150 bool DoReMat = VRM.isReMaterialized(VirtReg);
1152 ReMatDefs.insert(&MI);
1154 // The only vregs left are stack slot definitions.
1155 int StackSlot = VRM.getStackSlot(VirtReg);
1156 const TargetRegisterClass *RC = RegMap->getRegClass(VirtReg);
1158 // If this def is part of a two-address operand, make sure to execute
1159 // the store from the correct physical register.
1161 int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i);
1163 PhysReg = MI.getOperand(TiedOp).getReg();
1165 PhysReg = VRM.getPhys(VirtReg);
1166 if (ReusedOperands.isClobbered(PhysReg)) {
1167 // Another def has taken the assigned physreg. It must have been a
1168 // use&def which got it due to reuse. Undo the reuse!
1169 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
1170 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
1174 MF.setPhysRegUsed(PhysReg);
1175 ReusedOperands.markClobbered(PhysReg);
1176 MI.getOperand(i).setReg(PhysReg);
1178 MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
1179 DOUT << "Store:\t" << *next(MII);
1181 // If there is a dead store to this stack slot, nuke it now.
1182 MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
1184 DOUT << "Removed dead store:\t" << *LastStore;
1186 SmallVector<unsigned, 1> KillRegs;
1187 InvalidateKills(*LastStore, RegKills, KillOps, &KillRegs);
1188 MachineBasicBlock::iterator PrevMII = LastStore;
1189 bool CheckDef = PrevMII != MBB.begin();
1192 MBB.erase(LastStore);
1193 VRM.RemoveFromFoldedVirtMap(LastStore);
1195 // Look at defs of killed registers on the store. Mark the defs
1196 // as dead since the store has been deleted and they aren't
1198 for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
1199 bool HasOtherDef = false;
1200 if (InvalidateRegDef(PrevMII, MI, KillRegs[j], HasOtherDef)) {
1201 MachineInstr *DeadDef = PrevMII;
1202 if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
1203 // FIXME: This assumes a remat def does not have side
1206 VRM.RemoveFromFoldedVirtMap(DeadDef);
1213 LastStore = next(MII);
1215 // If the stack slot value was previously available in some other
1216 // register, change it now. Otherwise, make the register available,
1218 Spills.ModifyStackSlotOrReMat(StackSlot);
1219 Spills.ClobberPhysReg(PhysReg);
1220 Spills.addAvailable(StackSlot, LastStore, PhysReg);
1223 // Check to see if this is a noop copy. If so, eliminate the
1224 // instruction before considering the dest reg to be changed.
1227 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1229 DOUT << "Removing now-noop copy: " << MI;
1232 VRM.RemoveFromFoldedVirtMap(&MI);
1233 UpdateKills(*LastStore, RegKills, KillOps);
1234 goto ProcessNextInst;
1241 if (!Erased && !BackTracked)
1242 for (MachineBasicBlock::iterator II = MI; II != NextMII; ++II)
1243 UpdateKills(*II, RegKills, KillOps);
1249 llvm::Spiller* llvm::createSpiller() {
1250 switch (SpillerOpt) {
1251 default: assert(0 && "Unreachable!");
1253 return new LocalSpiller();
1255 return new SimpleSpiller();