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/ADT/Statistic.h"
30 #include "llvm/ADT/STLExtras.h"
36 Statistic<> NumSpills("spiller", "Number of register spills");
37 Statistic<> NumStores("spiller", "Number of stores added");
38 Statistic<> NumLoads ("spiller", "Number of loads added");
39 Statistic<> NumReused("spiller", "Number of values reused");
40 Statistic<> NumDSE ("spiller", "Number of dead stores elided");
41 Statistic<> NumDCE ("spiller", "Number of copies elided");
43 enum SpillerName { simple, local };
47 cl::desc("Spiller to use: (default: local)"),
49 cl::values(clEnumVal(simple, " simple spiller"),
50 clEnumVal(local, " local spiller"),
55 //===----------------------------------------------------------------------===//
56 // VirtRegMap implementation
57 //===----------------------------------------------------------------------===//
59 void VirtRegMap::grow() {
60 Virt2PhysMap.grow(MF.getSSARegMap()->getLastVirtReg());
61 Virt2StackSlotMap.grow(MF.getSSARegMap()->getLastVirtReg());
64 int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
65 assert(MRegisterInfo::isVirtualRegister(virtReg));
66 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
67 "attempt to assign stack slot to already spilled register");
68 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(virtReg);
69 int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
71 Virt2StackSlotMap[virtReg] = frameIndex;
76 void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) {
77 assert(MRegisterInfo::isVirtualRegister(virtReg));
78 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
79 "attempt to assign stack slot to already spilled register");
80 Virt2StackSlotMap[virtReg] = frameIndex;
83 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
84 unsigned OpNo, MachineInstr *NewMI) {
85 // Move previous memory references folded to new instruction.
86 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
87 for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
88 E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
89 MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
90 MI2VirtMap.erase(I++);
94 if (!OldMI->getOperand(OpNo).isDef()) {
95 assert(OldMI->getOperand(OpNo).isUse() && "Operand is not use or def?");
98 MRInfo = OldMI->getOperand(OpNo).isUse() ? isModRef : isMod;
101 // add new memory reference
102 MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
105 void VirtRegMap::print(std::ostream &OS) const {
106 const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
108 OS << "********** REGISTER MAP **********\n";
109 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
110 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) {
111 if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG)
112 OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n";
116 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
117 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i)
118 if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT)
119 OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n";
123 void VirtRegMap::dump() const { print(std::cerr); }
126 //===----------------------------------------------------------------------===//
127 // Simple Spiller Implementation
128 //===----------------------------------------------------------------------===//
130 Spiller::~Spiller() {}
133 struct SimpleSpiller : public Spiller {
134 bool runOnMachineFunction(MachineFunction& mf, const VirtRegMap &VRM);
138 bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF,
139 const VirtRegMap &VRM) {
140 DEBUG(std::cerr << "********** REWRITE MACHINE CODE **********\n");
141 DEBUG(std::cerr << "********** Function: "
142 << MF.getFunction()->getName() << '\n');
143 const TargetMachine &TM = MF.getTarget();
144 const MRegisterInfo &MRI = *TM.getRegisterInfo();
145 bool *PhysRegsUsed = MF.getUsedPhysregs();
147 // LoadedRegs - Keep track of which vregs are loaded, so that we only load
148 // each vreg once (in the case where a spilled vreg is used by multiple
149 // operands). This is always smaller than the number of operands to the
150 // current machine instr, so it should be small.
151 std::vector<unsigned> LoadedRegs;
153 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
155 DEBUG(std::cerr << MBBI->getBasicBlock()->getName() << ":\n");
156 MachineBasicBlock &MBB = *MBBI;
157 for (MachineBasicBlock::iterator MII = MBB.begin(),
158 E = MBB.end(); MII != E; ++MII) {
159 MachineInstr &MI = *MII;
160 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
161 MachineOperand &MO = MI.getOperand(i);
162 if (MO.isRegister() && MO.getReg())
163 if (MRegisterInfo::isVirtualRegister(MO.getReg())) {
164 unsigned VirtReg = MO.getReg();
165 unsigned PhysReg = VRM.getPhys(VirtReg);
166 if (VRM.hasStackSlot(VirtReg)) {
167 int StackSlot = VRM.getStackSlot(VirtReg);
168 const TargetRegisterClass* RC =
169 MF.getSSARegMap()->getRegClass(VirtReg);
172 std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
173 == LoadedRegs.end()) {
174 MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
175 LoadedRegs.push_back(VirtReg);
177 DEBUG(std::cerr << '\t' << *prior(MII));
181 MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
185 PhysRegsUsed[PhysReg] = true;
186 MI.SetMachineOperandReg(i, PhysReg);
188 PhysRegsUsed[MO.getReg()] = true;
192 DEBUG(std::cerr << '\t' << MI);
199 //===----------------------------------------------------------------------===//
200 // Local Spiller Implementation
201 //===----------------------------------------------------------------------===//
204 /// LocalSpiller - This spiller does a simple pass over the machine basic
205 /// block to attempt to keep spills in registers as much as possible for
206 /// blocks that have low register pressure (the vreg may be spilled due to
207 /// register pressure in other blocks).
208 class LocalSpiller : public Spiller {
209 const MRegisterInfo *MRI;
210 const TargetInstrInfo *TII;
212 bool runOnMachineFunction(MachineFunction &MF, const VirtRegMap &VRM) {
213 MRI = MF.getTarget().getRegisterInfo();
214 TII = MF.getTarget().getInstrInfo();
215 DEBUG(std::cerr << "\n**** Local spiller rewriting function '"
216 << MF.getFunction()->getName() << "':\n");
218 for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
220 RewriteMBB(*MBB, VRM);
224 void RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM);
225 void ClobberPhysReg(unsigned PR, std::map<int, unsigned> &SpillSlots,
226 std::multimap<unsigned, int> &PhysRegs);
227 void ClobberPhysRegOnly(unsigned PR, std::map<int, unsigned> &SpillSlots,
228 std::multimap<unsigned, int> &PhysRegs);
229 void ModifyStackSlot(int Slot, std::map<int, unsigned> &SpillSlots,
230 std::multimap<unsigned, int> &PhysRegs);
234 /// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
235 /// top down, keep track of which spills slots are available in each register.
236 class AvailableSpills {
237 const MRegisterInfo *MRI;
238 const TargetInstrInfo *TII;
240 // SpillSlotsAvailable - This map keeps track of all of the spilled virtual
241 // register values that are still available, due to being loaded or stored to,
242 // but not invalidated yet.
243 std::map<int, unsigned> SpillSlotsAvailable;
245 // PhysRegsAvailable - This is the inverse of SpillSlotsAvailable, indicating
246 // which stack slot values are currently held by a physreg. This is used to
247 // invalidate entries in SpillSlotsAvailable when a physreg is modified.
248 std::multimap<unsigned, int> PhysRegsAvailable;
250 void ClobberPhysRegOnly(unsigned PhysReg);
252 AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
253 : MRI(mri), TII(tii) {
256 /// getSpillSlotPhysReg - If the specified stack slot is available in a
257 /// physical register, return that PhysReg, otherwise return 0.
258 unsigned getSpillSlotPhysReg(int Slot) const {
259 std::map<int, unsigned>::const_iterator I = SpillSlotsAvailable.find(Slot);
260 if (I != SpillSlotsAvailable.end())
265 /// addAvailable - Mark that the specified stack slot is available in the
266 /// specified physreg.
267 void addAvailable(int Slot, unsigned Reg) {
268 PhysRegsAvailable.insert(std::make_pair(Reg, Slot));
269 SpillSlotsAvailable[Slot] = Reg;
271 DEBUG(std::cerr << "Remembering SS#" << Slot << " in physreg "
272 << MRI->getName(Reg) << "\n");
276 /// ClobberPhysReg - This is called when the specified physreg changes
277 /// value. We use this to invalidate any info about stuff we thing lives in
278 /// it and any of its aliases.
279 void ClobberPhysReg(unsigned PhysReg);
281 /// ModifyStackSlot - This method is called when the value in a stack slot
282 /// changes. This removes information about which register the previous value
283 /// for this slot lives in (as the previous value is dead now).
284 void ModifyStackSlot(int Slot);
287 /// ClobberPhysRegOnly - This is called when the specified physreg changes
288 /// value. We use this to invalidate any info about stuff we thing lives in it.
289 void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
290 std::multimap<unsigned, int>::iterator I =
291 PhysRegsAvailable.lower_bound(PhysReg);
292 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
293 int Slot = I->second;
294 PhysRegsAvailable.erase(I++);
295 assert(SpillSlotsAvailable[Slot] == PhysReg &&
296 "Bidirectional map mismatch!");
297 SpillSlotsAvailable.erase(Slot);
298 DEBUG(std::cerr << "PhysReg " << MRI->getName(PhysReg)
299 << " clobbered, invalidating SS#" << Slot << "\n");
303 /// ClobberPhysReg - This is called when the specified physreg changes
304 /// value. We use this to invalidate any info about stuff we thing lives in
305 /// it and any of its aliases.
306 void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
307 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
308 ClobberPhysRegOnly(*AS);
309 ClobberPhysRegOnly(PhysReg);
312 /// ModifyStackSlot - This method is called when the value in a stack slot
313 /// changes. This removes information about which register the previous value
314 /// for this slot lives in (as the previous value is dead now).
315 void AvailableSpills::ModifyStackSlot(int Slot) {
316 std::map<int, unsigned>::iterator It = SpillSlotsAvailable.find(Slot);
317 if (It == SpillSlotsAvailable.end()) return;
318 unsigned Reg = It->second;
319 SpillSlotsAvailable.erase(It);
321 // This register may hold the value of multiple stack slots, only remove this
322 // stack slot from the set of values the register contains.
323 std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
325 assert(I != PhysRegsAvailable.end() && I->first == Reg &&
326 "Map inverse broken!");
327 if (I->second == Slot) break;
329 PhysRegsAvailable.erase(I);
334 // ReusedOp - For each reused operand, we keep track of a bit of information, in
335 // case we need to rollback upon processing a new operand. See comments below.
338 // The MachineInstr operand that reused an available value.
341 // StackSlot - The spill slot of the value being reused.
344 // PhysRegReused - The physical register the value was available in.
345 unsigned PhysRegReused;
347 // AssignedPhysReg - The physreg that was assigned for use by the reload.
348 unsigned AssignedPhysReg;
350 // VirtReg - The virtual register itself.
353 ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
355 : Operand(o), StackSlot(ss), PhysRegReused(prr), AssignedPhysReg(apr),
361 /// rewriteMBB - Keep track of which spills are available even after the
362 /// register allocator is done with them. If possible, avoid reloading vregs.
363 void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) {
365 DEBUG(std::cerr << MBB.getBasicBlock()->getName() << ":\n");
367 // Spills - Keep track of which spilled values are available in physregs so
368 // that we can choose to reuse the physregs instead of emitting reloads.
369 AvailableSpills Spills(MRI, TII);
371 std::vector<ReusedOp> ReusedOperands;
373 // DefAndUseVReg - When we see a def&use operand that is spilled, keep track
374 // of it. ".first" is the machine operand index (should always be 0 for now),
375 // and ".second" is the virtual register that is spilled.
376 std::vector<std::pair<unsigned, unsigned> > DefAndUseVReg;
378 // MaybeDeadStores - When we need to write a value back into a stack slot,
379 // keep track of the inserted store. If the stack slot value is never read
380 // (because the value was used from some available register, for example), and
381 // subsequently stored to, the original store is dead. This map keeps track
382 // of inserted stores that are not used. If we see a subsequent store to the
383 // same stack slot, the original store is deleted.
384 std::map<int, MachineInstr*> MaybeDeadStores;
386 bool *PhysRegsUsed = MBB.getParent()->getUsedPhysregs();
388 for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
390 MachineInstr &MI = *MII;
391 MachineBasicBlock::iterator NextMII = MII; ++NextMII;
393 ReusedOperands.clear();
394 DefAndUseVReg.clear();
396 // Process all of the spilled uses and all non spilled reg references.
397 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
398 MachineOperand &MO = MI.getOperand(i);
399 if (!MO.isRegister() || MO.getReg() == 0)
400 continue; // Ignore non-register operands.
402 if (MRegisterInfo::isPhysicalRegister(MO.getReg())) {
403 // Ignore physregs for spilling, but remember that it is used by this
405 PhysRegsUsed[MO.getReg()] = true;
409 assert(MRegisterInfo::isVirtualRegister(MO.getReg()) &&
410 "Not a virtual or a physical register?");
412 unsigned VirtReg = MO.getReg();
413 if (!VRM.hasStackSlot(VirtReg)) {
414 // This virtual register was assigned a physreg!
415 unsigned Phys = VRM.getPhys(VirtReg);
416 PhysRegsUsed[Phys] = true;
417 MI.SetMachineOperandReg(i, Phys);
421 // This virtual register is now known to be a spilled value.
423 continue; // Handle defs in the loop below (handle use&def here though)
425 // If this is both a def and a use, we need to emit a store to the
426 // stack slot after the instruction. Keep track of D&U operands
427 // because we are about to change it to a physreg here.
429 // Remember that this was a def-and-use operand, and that the
430 // stack slot is live after this instruction executes.
431 DefAndUseVReg.push_back(std::make_pair(i, VirtReg));
434 int StackSlot = VRM.getStackSlot(VirtReg);
437 // Check to see if this stack slot is available.
438 if ((PhysReg = Spills.getSpillSlotPhysReg(StackSlot))) {
439 // If this stack slot value is already available, reuse it!
440 DEBUG(std::cerr << "Reusing SS#" << StackSlot << " from physreg "
441 << MRI->getName(PhysReg) << " for vreg"
442 << VirtReg <<" instead of reloading into physreg "
443 << MRI->getName(VRM.getPhys(VirtReg)) << "\n");
444 MI.SetMachineOperandReg(i, PhysReg);
446 // The only technical detail we have is that we don't know that
447 // PhysReg won't be clobbered by a reloaded stack slot that occurs
448 // later in the instruction. In particular, consider 'op V1, V2'.
449 // If V1 is available in physreg R0, we would choose to reuse it
450 // here, instead of reloading it into the register the allocator
451 // indicated (say R1). However, V2 might have to be reloaded
452 // later, and it might indicate that it needs to live in R0. When
453 // this occurs, we need to have information available that
454 // indicates it is safe to use R1 for the reload instead of R0.
456 // To further complicate matters, we might conflict with an alias,
457 // or R0 and R1 might not be compatible with each other. In this
458 // case, we actually insert a reload for V1 in R1, ensuring that
459 // we can get at R0 or its alias.
460 ReusedOperands.push_back(ReusedOp(i, StackSlot, PhysReg,
461 VRM.getPhys(VirtReg), VirtReg));
466 // Otherwise, reload it and remember that we have it.
467 PhysReg = VRM.getPhys(VirtReg);
468 assert(PhysReg && "Must map virtreg to physreg!");
469 const TargetRegisterClass* RC =
470 MBB.getParent()->getSSARegMap()->getRegClass(VirtReg);
473 // Note that, if we reused a register for a previous operand, the
474 // register we want to reload into might not actually be
475 // available. If this occurs, use the register indicated by the
477 if (!ReusedOperands.empty()) // This is most often empty.
478 for (unsigned ro = 0, e = ReusedOperands.size(); ro != e; ++ro)
479 if (ReusedOperands[ro].PhysRegReused == PhysReg) {
480 // Yup, use the reload register that we didn't use before.
481 PhysReg = ReusedOperands[ro].AssignedPhysReg;
482 goto RecheckRegister;
484 ReusedOp &Op = ReusedOperands[ro];
485 unsigned PRRU = Op.PhysRegReused;
486 if (MRI->areAliases(PRRU, PhysReg)) {
487 // Okay, we found out that an alias of a reused register
488 // was used. This isn't good because it means we have
489 // to undo a previous reuse.
490 const TargetRegisterClass *AliasRC =
491 MBB.getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
492 MRI->loadRegFromStackSlot(MBB, &MI, Op.AssignedPhysReg,
493 Op.StackSlot, AliasRC);
494 Spills.ClobberPhysReg(Op.AssignedPhysReg);
495 Spills.ClobberPhysReg(Op.PhysRegReused);
497 // Any stores to this stack slot are not dead anymore.
498 MaybeDeadStores.erase(Op.StackSlot);
500 MI.SetMachineOperandReg(Op.Operand, Op.AssignedPhysReg);
502 Spills.addAvailable(Op.StackSlot, Op.AssignedPhysReg);
504 DEBUG(std::cerr << '\t' << *prior(MII));
506 DEBUG(std::cerr << "Reuse undone!\n");
507 ReusedOperands.erase(ReusedOperands.begin()+ro);
513 PhysRegsUsed[PhysReg] = true;
514 MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
515 // This invalidates PhysReg.
516 Spills.ClobberPhysReg(PhysReg);
518 // Any stores to this stack slot are not dead anymore.
519 MaybeDeadStores.erase(StackSlot);
520 Spills.addAvailable(StackSlot, PhysReg);
522 MI.SetMachineOperandReg(i, PhysReg);
523 DEBUG(std::cerr << '\t' << *prior(MII));
526 // Loop over all of the implicit defs, clearing them from our available
528 for (const unsigned *ImpDef = TII->getImplicitDefs(MI.getOpcode());
530 PhysRegsUsed[*ImpDef] = true;
531 Spills.ClobberPhysReg(*ImpDef);
534 DEBUG(std::cerr << '\t' << MI);
536 // If we have folded references to memory operands, make sure we clear all
537 // physical registers that may contain the value of the spilled virtual
539 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
540 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
541 DEBUG(std::cerr << "Folded vreg: " << I->second.first << " MR: "
542 << I->second.second);
543 unsigned VirtReg = I->second.first;
544 VirtRegMap::ModRef MR = I->second.second;
545 if (!VRM.hasStackSlot(VirtReg)) {
546 DEBUG(std::cerr << ": No stack slot!\n");
549 int SS = VRM.getStackSlot(VirtReg);
550 DEBUG(std::cerr << " - StackSlot: " << SS << "\n");
552 // If this folded instruction is just a use, check to see if it's a
553 // straight load from the virt reg slot.
554 if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
556 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
557 // If this spill slot is available, turn it into a copy (or nothing)
558 // instead of leaving it as a load!
560 if (FrameIdx == SS && (InReg = Spills.getSpillSlotPhysReg(SS))) {
561 DEBUG(std::cerr << "Promoted Load To Copy: " << MI);
562 MachineFunction &MF = *MBB.getParent();
563 if (DestReg != InReg) {
564 MRI->copyRegToReg(MBB, &MI, DestReg, InReg,
565 MF.getSSARegMap()->getRegClass(VirtReg));
566 // Revisit the copy so we make sure to notice the effects of the
567 // operation on the destreg (either needing to RA it if it's
568 // virtual or needing to clobber any values if it's physical).
570 --NextMII; // backtrack to the copy.
573 goto ProcessNextInst;
578 // If this reference is not a use, any previous store is now dead.
579 // Otherwise, the store to this stack slot is not dead anymore.
580 std::map<int, MachineInstr*>::iterator MDSI = MaybeDeadStores.find(SS);
581 if (MDSI != MaybeDeadStores.end()) {
582 if (MR & VirtRegMap::isRef) // Previous store is not dead.
583 MaybeDeadStores.erase(MDSI);
585 // If we get here, the store is dead, nuke it now.
586 assert(MR == VirtRegMap::isMod && "Can't be modref!");
587 MBB.erase(MDSI->second);
588 MaybeDeadStores.erase(MDSI);
593 // If the spill slot value is available, and this is a new definition of
594 // the value, the value is not available anymore.
595 if (MR & VirtRegMap::isMod) {
596 // Notice that the value in this stack slot has been modified.
597 Spills.ModifyStackSlot(SS);
599 // If this is *just* a mod of the value, check to see if this is just a
600 // store to the spill slot (i.e. the spill got merged into the copy). If
601 // so, realize that the vreg is available now, and add the store to the
602 // MaybeDeadStore info.
604 if (!(MR & VirtRegMap::isRef)) {
605 if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
606 assert(MRegisterInfo::isPhysicalRegister(SrcReg) &&
607 "Src hasn't been allocated yet?");
608 // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
609 // this as a potentially dead store in case there is a subsequent
610 // store into the stack slot without a read from it.
611 MaybeDeadStores[StackSlot] = &MI;
613 // If the stack slot value was previously available in some other
614 // register, change it now. Otherwise, make the register available,
616 Spills.addAvailable(StackSlot, SrcReg);
622 // Process all of the spilled defs.
623 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
624 MachineOperand &MO = MI.getOperand(i);
625 if (MO.isRegister() && MO.getReg() && MO.isDef()) {
626 unsigned VirtReg = MO.getReg();
628 if (!MRegisterInfo::isVirtualRegister(VirtReg)) {
629 // Check to see if this is a def-and-use vreg operand that we do need
630 // to insert a store for.
631 bool OpTakenCareOf = false;
632 if (MO.isUse() && !DefAndUseVReg.empty()) {
633 for (unsigned dau = 0, e = DefAndUseVReg.size(); dau != e; ++dau)
634 if (DefAndUseVReg[dau].first == i) {
635 VirtReg = DefAndUseVReg[dau].second;
636 OpTakenCareOf = true;
641 if (!OpTakenCareOf) {
642 // Check to see if this is a noop copy. If so, eliminate the
643 // instruction before considering the dest reg to be changed.
645 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
647 DEBUG(std::cerr << "Removing now-noop copy: " << MI);
649 goto ProcessNextInst;
651 Spills.ClobberPhysReg(VirtReg);
656 // The only vregs left are stack slot definitions.
657 int StackSlot = VRM.getStackSlot(VirtReg);
658 const TargetRegisterClass *RC =
659 MBB.getParent()->getSSARegMap()->getRegClass(VirtReg);
662 // If this is a def&use operand, and we used a different physreg for
663 // it than the one assigned, make sure to execute the store from the
664 // correct physical register.
665 if (MO.getReg() == VirtReg)
666 PhysReg = VRM.getPhys(VirtReg);
668 PhysReg = MO.getReg();
670 PhysRegsUsed[PhysReg] = true;
671 MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
672 DEBUG(std::cerr << "Store:\t" << *next(MII));
673 MI.SetMachineOperandReg(i, PhysReg);
675 // Check to see if this is a noop copy. If so, eliminate the
676 // instruction before considering the dest reg to be changed.
679 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
681 DEBUG(std::cerr << "Removing now-noop copy: " << MI);
683 goto ProcessNextInst;
687 // If there is a dead store to this stack slot, nuke it now.
688 MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
690 DEBUG(std::cerr << " Killed store:\t" << *LastStore);
692 MBB.erase(LastStore);
694 LastStore = next(MII);
696 // If the stack slot value was previously available in some other
697 // register, change it now. Otherwise, make the register available,
699 Spills.ModifyStackSlot(StackSlot);
700 Spills.ClobberPhysReg(PhysReg);
702 Spills.addAvailable(StackSlot, PhysReg);
713 llvm::Spiller* llvm::createSpiller() {
714 switch (SpillerOpt) {
715 default: assert(0 && "Unreachable!");
717 return new LocalSpiller();
719 return new SimpleSpiller();