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(NumStores, "Number of stores added");
40 STATISTIC(NumLoads , "Number of loads added");
41 STATISTIC(NumReused, "Number of values reused");
42 STATISTIC(NumDSE , "Number of dead stores elided");
43 STATISTIC(NumDCE , "Number of copies elided");
46 enum SpillerName { simple, local };
48 static cl::opt<SpillerName>
50 cl::desc("Spiller to use: (default: local)"),
52 cl::values(clEnumVal(simple, " simple spiller"),
53 clEnumVal(local, " local spiller"),
58 //===----------------------------------------------------------------------===//
59 // VirtRegMap implementation
60 //===----------------------------------------------------------------------===//
62 VirtRegMap::VirtRegMap(MachineFunction &mf)
63 : TII(*mf.getTarget().getInstrInfo()), MF(mf),
64 Virt2PhysMap(NO_PHYS_REG), Virt2StackSlotMap(NO_STACK_SLOT),
65 ReMatId(MAX_STACK_SLOT+1) {
69 void VirtRegMap::grow() {
70 Virt2PhysMap.grow(MF.getSSARegMap()->getLastVirtReg());
71 Virt2StackSlotMap.grow(MF.getSSARegMap()->getLastVirtReg());
74 int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
75 assert(MRegisterInfo::isVirtualRegister(virtReg));
76 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
77 "attempt to assign stack slot to already spilled register");
78 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(virtReg);
79 int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
81 Virt2StackSlotMap[virtReg] = frameIndex;
86 void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) {
87 assert(MRegisterInfo::isVirtualRegister(virtReg));
88 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
89 "attempt to assign stack slot to already spilled register");
90 assert((frameIndex >= 0 ||
91 (frameIndex >= MF.getFrameInfo()->getObjectIndexBegin())) &&
92 "illegal fixed frame index");
93 Virt2StackSlotMap[virtReg] = frameIndex;
96 int VirtRegMap::assignVirtReMatId(unsigned virtReg) {
97 assert(MRegisterInfo::isVirtualRegister(virtReg));
98 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
99 "attempt to assign re-mat id to already spilled register");
100 const MachineInstr *DefMI = getReMaterializedMI(virtReg);
102 if (TII.isLoadFromStackSlot((MachineInstr*)DefMI, FrameIdx)) {
103 // Load from stack slot is re-materialize as reload from the stack slot!
104 Virt2StackSlotMap[virtReg] = FrameIdx;
107 Virt2StackSlotMap[virtReg] = ReMatId;
111 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
112 unsigned OpNo, MachineInstr *NewMI) {
113 // Move previous memory references folded to new instruction.
114 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
115 for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
116 E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
117 MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
118 MI2VirtMap.erase(I++);
122 const TargetInstrDescriptor *TID = OldMI->getInstrDescriptor();
123 if (TID->getOperandConstraint(OpNo, TOI::TIED_TO) != -1 ||
124 TID->findTiedToSrcOperand(OpNo) != -1) {
125 // Folded a two-address operand.
127 } else if (OldMI->getOperand(OpNo).isDef()) {
133 // add new memory reference
134 MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
137 void VirtRegMap::print(std::ostream &OS) const {
138 const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
140 OS << "********** REGISTER MAP **********\n";
141 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
142 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) {
143 if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG)
144 OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n";
148 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
149 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i)
150 if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT)
151 OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n";
155 void VirtRegMap::dump() const {
160 //===----------------------------------------------------------------------===//
161 // Simple Spiller Implementation
162 //===----------------------------------------------------------------------===//
164 Spiller::~Spiller() {}
167 struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller {
168 bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM);
172 bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
173 DOUT << "********** REWRITE MACHINE CODE **********\n";
174 DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
175 const TargetMachine &TM = MF.getTarget();
176 const MRegisterInfo &MRI = *TM.getRegisterInfo();
178 // LoadedRegs - Keep track of which vregs are loaded, so that we only load
179 // each vreg once (in the case where a spilled vreg is used by multiple
180 // operands). This is always smaller than the number of operands to the
181 // current machine instr, so it should be small.
182 std::vector<unsigned> LoadedRegs;
184 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
186 DOUT << MBBI->getBasicBlock()->getName() << ":\n";
187 MachineBasicBlock &MBB = *MBBI;
188 for (MachineBasicBlock::iterator MII = MBB.begin(),
189 E = MBB.end(); MII != E; ++MII) {
190 MachineInstr &MI = *MII;
191 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
192 MachineOperand &MO = MI.getOperand(i);
193 if (MO.isRegister() && MO.getReg())
194 if (MRegisterInfo::isVirtualRegister(MO.getReg())) {
195 unsigned VirtReg = MO.getReg();
196 unsigned PhysReg = VRM.getPhys(VirtReg);
197 if (VRM.hasStackSlot(VirtReg)) {
198 int StackSlot = VRM.getStackSlot(VirtReg);
199 const TargetRegisterClass* RC =
200 MF.getSSARegMap()->getRegClass(VirtReg);
203 std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
204 == LoadedRegs.end()) {
205 MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
206 LoadedRegs.push_back(VirtReg);
208 DOUT << '\t' << *prior(MII);
212 MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
216 MF.setPhysRegUsed(PhysReg);
217 MI.getOperand(i).setReg(PhysReg);
219 MF.setPhysRegUsed(MO.getReg());
230 //===----------------------------------------------------------------------===//
231 // Local Spiller Implementation
232 //===----------------------------------------------------------------------===//
235 /// LocalSpiller - This spiller does a simple pass over the machine basic
236 /// block to attempt to keep spills in registers as much as possible for
237 /// blocks that have low register pressure (the vreg may be spilled due to
238 /// register pressure in other blocks).
239 class VISIBILITY_HIDDEN LocalSpiller : public Spiller {
240 const MRegisterInfo *MRI;
241 const TargetInstrInfo *TII;
243 bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
244 MRI = MF.getTarget().getRegisterInfo();
245 TII = MF.getTarget().getInstrInfo();
246 DOUT << "\n**** Local spiller rewriting function '"
247 << MF.getFunction()->getName() << "':\n";
249 std::vector<MachineInstr *> ReMatedMIs;
250 for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
252 RewriteMBB(*MBB, VRM, ReMatedMIs);
253 for (unsigned i = 0, e = ReMatedMIs.size(); i != e; ++i)
254 delete ReMatedMIs[i];
258 void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM,
259 std::vector<MachineInstr*> &ReMatedMIs);
263 /// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
264 /// top down, keep track of which spills slots are available in each register.
266 /// Note that not all physregs are created equal here. In particular, some
267 /// physregs are reloads that we are allowed to clobber or ignore at any time.
268 /// Other physregs are values that the register allocated program is using that
269 /// we cannot CHANGE, but we can read if we like. We keep track of this on a
270 /// per-stack-slot basis as the low bit in the value of the SpillSlotsAvailable
271 /// entries. The predicate 'canClobberPhysReg()' checks this bit and
272 /// addAvailable sets it if.
274 class VISIBILITY_HIDDEN AvailableSpills {
275 const MRegisterInfo *MRI;
276 const TargetInstrInfo *TII;
278 // SpillSlotsAvailable - This map keeps track of all of the spilled virtual
279 // register values that are still available, due to being loaded or stored to,
280 // but not invalidated yet.
281 std::map<int, unsigned> SpillSlotsAvailable;
283 // PhysRegsAvailable - This is the inverse of SpillSlotsAvailable, indicating
284 // which stack slot values are currently held by a physreg. This is used to
285 // invalidate entries in SpillSlotsAvailable when a physreg is modified.
286 std::multimap<unsigned, int> PhysRegsAvailable;
288 void disallowClobberPhysRegOnly(unsigned PhysReg);
290 void ClobberPhysRegOnly(unsigned PhysReg);
292 AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
293 : MRI(mri), TII(tii) {
296 const MRegisterInfo *getRegInfo() const { return MRI; }
298 /// getSpillSlotPhysReg - If the specified stack slot is available in a
299 /// physical register, return that PhysReg, otherwise return 0.
300 unsigned getSpillSlotPhysReg(int Slot) const {
301 std::map<int, unsigned>::const_iterator I = SpillSlotsAvailable.find(Slot);
302 if (I != SpillSlotsAvailable.end()) {
303 return I->second >> 1; // Remove the CanClobber bit.
308 /// addAvailable - Mark that the specified stack slot is available in the
309 /// specified physreg. If CanClobber is true, the physreg can be modified at
310 /// any time without changing the semantics of the program.
311 void addAvailable(int Slot, MachineInstr *MI, unsigned Reg,
312 bool CanClobber = true) {
313 // If this stack slot is thought to be available in some other physreg,
314 // remove its record.
315 ModifyStackSlot(Slot);
317 PhysRegsAvailable.insert(std::make_pair(Reg, Slot));
318 SpillSlotsAvailable[Slot] = (Reg << 1) | (unsigned)CanClobber;
320 if (Slot > VirtRegMap::MAX_STACK_SLOT)
321 DOUT << "Remembering RM#" << Slot-VirtRegMap::MAX_STACK_SLOT-1;
323 DOUT << "Remembering SS#" << Slot;
324 DOUT << " in physreg " << MRI->getName(Reg) << "\n";
327 /// canClobberPhysReg - Return true if the spiller is allowed to change the
328 /// value of the specified stackslot register if it desires. The specified
329 /// stack slot must be available in a physreg for this query to make sense.
330 bool canClobberPhysReg(int Slot) const {
331 assert(SpillSlotsAvailable.count(Slot) && "Slot not available!");
332 return SpillSlotsAvailable.find(Slot)->second & 1;
335 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
336 /// stackslot register. The register is still available but is no longer
337 /// allowed to be modifed.
338 void disallowClobberPhysReg(unsigned PhysReg);
340 /// ClobberPhysReg - This is called when the specified physreg changes
341 /// value. We use this to invalidate any info about stuff we thing lives in
342 /// it and any of its aliases.
343 void ClobberPhysReg(unsigned PhysReg);
345 /// ModifyStackSlot - This method is called when the value in a stack slot
346 /// changes. This removes information about which register the previous value
347 /// for this slot lives in (as the previous value is dead now).
348 void ModifyStackSlot(int Slot);
352 /// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
353 /// stackslot register. The register is still available but is no longer
354 /// allowed to be modifed.
355 void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
356 std::multimap<unsigned, int>::iterator I =
357 PhysRegsAvailable.lower_bound(PhysReg);
358 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
359 int Slot = I->second;
361 assert((SpillSlotsAvailable[Slot] >> 1) == PhysReg &&
362 "Bidirectional map mismatch!");
363 SpillSlotsAvailable[Slot] &= ~1;
364 DOUT << "PhysReg " << MRI->getName(PhysReg)
365 << " copied, it is available for use but can no longer be modified\n";
369 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
370 /// stackslot register and its aliases. The register and its aliases may
371 /// still available but is no longer allowed to be modifed.
372 void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
373 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
374 disallowClobberPhysRegOnly(*AS);
375 disallowClobberPhysRegOnly(PhysReg);
378 /// ClobberPhysRegOnly - This is called when the specified physreg changes
379 /// value. We use this to invalidate any info about stuff we thing lives in it.
380 void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
381 std::multimap<unsigned, int>::iterator I =
382 PhysRegsAvailable.lower_bound(PhysReg);
383 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
384 int Slot = I->second;
385 PhysRegsAvailable.erase(I++);
386 assert((SpillSlotsAvailable[Slot] >> 1) == PhysReg &&
387 "Bidirectional map mismatch!");
388 SpillSlotsAvailable.erase(Slot);
389 DOUT << "PhysReg " << MRI->getName(PhysReg)
390 << " clobbered, invalidating ";
391 if (Slot > VirtRegMap::MAX_STACK_SLOT)
392 DOUT << "RM#" << Slot-VirtRegMap::MAX_STACK_SLOT-1 << "\n";
394 DOUT << "SS#" << Slot << "\n";
398 /// ClobberPhysReg - This is called when the specified physreg changes
399 /// value. We use this to invalidate any info about stuff we thing lives in
400 /// it and any of its aliases.
401 void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
402 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
403 ClobberPhysRegOnly(*AS);
404 ClobberPhysRegOnly(PhysReg);
407 /// ModifyStackSlot - This method is called when the value in a stack slot
408 /// changes. This removes information about which register the previous value
409 /// for this slot lives in (as the previous value is dead now).
410 void AvailableSpills::ModifyStackSlot(int Slot) {
411 std::map<int, unsigned>::iterator It = SpillSlotsAvailable.find(Slot);
412 if (It == SpillSlotsAvailable.end()) return;
413 unsigned Reg = It->second >> 1;
414 SpillSlotsAvailable.erase(It);
416 // This register may hold the value of multiple stack slots, only remove this
417 // stack slot from the set of values the register contains.
418 std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
420 assert(I != PhysRegsAvailable.end() && I->first == Reg &&
421 "Map inverse broken!");
422 if (I->second == Slot) break;
424 PhysRegsAvailable.erase(I);
429 // ReusedOp - For each reused operand, we keep track of a bit of information, in
430 // case we need to rollback upon processing a new operand. See comments below.
433 // The MachineInstr operand that reused an available value.
436 // StackSlot - The spill slot of the value being reused.
439 // PhysRegReused - The physical register the value was available in.
440 unsigned PhysRegReused;
442 // AssignedPhysReg - The physreg that was assigned for use by the reload.
443 unsigned AssignedPhysReg;
445 // VirtReg - The virtual register itself.
448 ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
450 : Operand(o), StackSlot(ss), PhysRegReused(prr), AssignedPhysReg(apr),
454 /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
455 /// is reused instead of reloaded.
456 class VISIBILITY_HIDDEN ReuseInfo {
458 std::vector<ReusedOp> Reuses;
459 BitVector PhysRegsClobbered;
461 ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
462 PhysRegsClobbered.resize(mri->getNumRegs());
465 bool hasReuses() const {
466 return !Reuses.empty();
469 /// addReuse - If we choose to reuse a virtual register that is already
470 /// available instead of reloading it, remember that we did so.
471 void addReuse(unsigned OpNo, unsigned StackSlot,
472 unsigned PhysRegReused, unsigned AssignedPhysReg,
474 // If the reload is to the assigned register anyway, no undo will be
476 if (PhysRegReused == AssignedPhysReg) return;
478 // Otherwise, remember this.
479 Reuses.push_back(ReusedOp(OpNo, StackSlot, PhysRegReused,
480 AssignedPhysReg, VirtReg));
483 void markClobbered(unsigned PhysReg) {
484 PhysRegsClobbered.set(PhysReg);
487 bool isClobbered(unsigned PhysReg) const {
488 return PhysRegsClobbered.test(PhysReg);
491 /// GetRegForReload - We are about to emit a reload into PhysReg. If there
492 /// is some other operand that is using the specified register, either pick
493 /// a new register to use, or evict the previous reload and use this reg.
494 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
495 AvailableSpills &Spills,
496 std::map<int, MachineInstr*> &MaybeDeadStores,
497 SmallSet<unsigned, 8> &Rejected) {
498 if (Reuses.empty()) return PhysReg; // This is most often empty.
500 for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
501 ReusedOp &Op = Reuses[ro];
502 // If we find some other reuse that was supposed to use this register
503 // exactly for its reload, we can change this reload to use ITS reload
504 // register. That is, unless its reload register has already been
505 // considered and subsequently rejected because it has also been reused
506 // by another operand.
507 if (Op.PhysRegReused == PhysReg &&
508 Rejected.count(Op.AssignedPhysReg) == 0) {
509 // Yup, use the reload register that we didn't use before.
510 unsigned NewReg = Op.AssignedPhysReg;
511 Rejected.insert(PhysReg);
512 return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected);
514 // Otherwise, we might also have a problem if a previously reused
515 // value aliases the new register. If so, codegen the previous reload
517 unsigned PRRU = Op.PhysRegReused;
518 const MRegisterInfo *MRI = Spills.getRegInfo();
519 if (MRI->areAliases(PRRU, PhysReg)) {
520 // Okay, we found out that an alias of a reused register
521 // was used. This isn't good because it means we have
522 // to undo a previous reuse.
523 MachineBasicBlock *MBB = MI->getParent();
524 const TargetRegisterClass *AliasRC =
525 MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
527 // Copy Op out of the vector and remove it, we're going to insert an
528 // explicit load for it.
530 Reuses.erase(Reuses.begin()+ro);
532 // Ok, we're going to try to reload the assigned physreg into the
533 // slot that we were supposed to in the first place. However, that
534 // register could hold a reuse. Check to see if it conflicts or
535 // would prefer us to use a different register.
536 unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
537 MI, Spills, MaybeDeadStores, Rejected);
539 MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg,
540 NewOp.StackSlot, AliasRC);
541 Spills.ClobberPhysReg(NewPhysReg);
542 Spills.ClobberPhysReg(NewOp.PhysRegReused);
544 // Any stores to this stack slot are not dead anymore.
545 MaybeDeadStores.erase(NewOp.StackSlot);
547 MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
549 Spills.addAvailable(NewOp.StackSlot, MI, NewPhysReg);
551 DEBUG(MachineBasicBlock::iterator MII = MI;
552 DOUT << '\t' << *prior(MII));
554 DOUT << "Reuse undone!\n";
557 // Finally, PhysReg is now available, go ahead and use it.
565 /// GetRegForReload - Helper for the above GetRegForReload(). Add a
566 /// 'Rejected' set to remember which registers have been considered and
567 /// rejected for the reload. This avoids infinite looping in case like
570 /// t2 <- assigned r0 for use by the reload but ended up reuse r1
571 /// t3 <- assigned r1 for use by the reload but ended up reuse r0
573 /// sees r1 is taken by t2, tries t2's reload register r0
574 /// sees r0 is taken by t3, tries t3's reload register r1
575 /// sees r1 is taken by t2, tries t2's reload register r0 ...
576 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
577 AvailableSpills &Spills,
578 std::map<int, MachineInstr*> &MaybeDeadStores) {
579 SmallSet<unsigned, 8> Rejected;
580 return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected);
586 /// InvalidateKills - MI is going to be deleted. If any of its operands are
587 /// marked kill, then invalidate the information.
588 static void InvalidateKills(MachineInstr &MI, BitVector &RegKills,
589 std::vector<MachineOperand*> &KillOps) {
590 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
591 MachineOperand &MO = MI.getOperand(i);
592 if (!MO.isReg() || !MO.isUse() || !MO.isKill())
594 unsigned Reg = MO.getReg();
595 if (KillOps[Reg] == &MO) {
602 /// UpdateKills - Track and update kill info. If a MI reads a register that is
603 /// marked kill, then it must be due to register reuse. Transfer the kill info
605 static void UpdateKills(MachineInstr &MI, BitVector &RegKills,
606 std::vector<MachineOperand*> &KillOps) {
607 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
608 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
609 MachineOperand &MO = MI.getOperand(i);
610 if (!MO.isReg() || !MO.isUse())
612 unsigned Reg = MO.getReg();
617 // That can't be right. Register is killed but not re-defined and it's
618 // being reused. Let's fix that.
619 KillOps[Reg]->unsetIsKill();
620 if (i < TID->numOperands &&
621 TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
622 // Unless it's a two-address operand, this is the new kill.
632 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
633 const MachineOperand &MO = MI.getOperand(i);
634 if (!MO.isReg() || !MO.isDef())
636 unsigned Reg = MO.getReg();
643 /// rewriteMBB - Keep track of which spills are available even after the
644 /// register allocator is done with them. If possible, avoid reloading vregs.
645 void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM,
646 std::vector<MachineInstr*> &ReMatedMIs) {
647 DOUT << MBB.getBasicBlock()->getName() << ":\n";
649 // Spills - Keep track of which spilled values are available in physregs so
650 // that we can choose to reuse the physregs instead of emitting reloads.
651 AvailableSpills Spills(MRI, TII);
653 // MaybeDeadStores - When we need to write a value back into a stack slot,
654 // keep track of the inserted store. If the stack slot value is never read
655 // (because the value was used from some available register, for example), and
656 // subsequently stored to, the original store is dead. This map keeps track
657 // of inserted stores that are not used. If we see a subsequent store to the
658 // same stack slot, the original store is deleted.
659 std::map<int, MachineInstr*> MaybeDeadStores;
661 // Keep track of kill information.
662 BitVector RegKills(MRI->getNumRegs());
663 std::vector<MachineOperand*> KillOps;
664 KillOps.resize(MRI->getNumRegs(), NULL);
666 MachineFunction &MF = *MBB.getParent();
667 for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
669 MachineInstr &MI = *MII;
670 MachineBasicBlock::iterator NextMII = MII; ++NextMII;
671 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
674 bool BackTracked = false;
676 /// ReusedOperands - Keep track of operand reuse in case we need to undo
678 ReuseInfo ReusedOperands(MI, MRI);
680 // Loop over all of the implicit defs, clearing them from our available
682 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
684 // If this instruction is being rematerialized, just remove it!
686 if (TII->isTriviallyReMaterializable(&MI) ||
687 TII->isLoadFromStackSlot(&MI, FrameIdx)) {
689 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
690 MachineOperand &MO = MI.getOperand(i);
691 if (!MO.isRegister() || MO.getReg() == 0)
692 continue; // Ignore non-register operands.
693 if (MO.isDef() && !VRM.isReMaterialized(MO.getReg())) {
699 VRM.RemoveFromFoldedVirtMap(&MI);
700 ReMatedMIs.push_back(MI.removeFromParent());
701 goto ProcessNextInst;
705 if (TID->ImplicitDefs) {
706 const unsigned *ImpDef = TID->ImplicitDefs;
707 for ( ; *ImpDef; ++ImpDef) {
708 MF.setPhysRegUsed(*ImpDef);
709 ReusedOperands.markClobbered(*ImpDef);
710 Spills.ClobberPhysReg(*ImpDef);
714 // Process all of the spilled uses and all non spilled reg references.
715 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
716 MachineOperand &MO = MI.getOperand(i);
717 if (!MO.isRegister() || MO.getReg() == 0)
718 continue; // Ignore non-register operands.
720 if (MRegisterInfo::isPhysicalRegister(MO.getReg())) {
721 // Ignore physregs for spilling, but remember that it is used by this
723 MF.setPhysRegUsed(MO.getReg());
724 ReusedOperands.markClobbered(MO.getReg());
728 assert(MRegisterInfo::isVirtualRegister(MO.getReg()) &&
729 "Not a virtual or a physical register?");
731 unsigned VirtReg = MO.getReg();
732 if (!VRM.hasStackSlot(VirtReg)) {
733 // This virtual register was assigned a physreg!
734 unsigned Phys = VRM.getPhys(VirtReg);
735 MF.setPhysRegUsed(Phys);
737 ReusedOperands.markClobbered(Phys);
738 MI.getOperand(i).setReg(Phys);
742 // This virtual register is now known to be a spilled value.
744 continue; // Handle defs in the loop below (handle use&def here though)
746 bool doReMat = VRM.isReMaterialized(VirtReg);
747 int StackSlot = VRM.getStackSlot(VirtReg);
750 // Check to see if this stack slot is available.
751 if ((PhysReg = Spills.getSpillSlotPhysReg(StackSlot))) {
752 // This spilled operand might be part of a two-address operand. If this
753 // is the case, then changing it will necessarily require changing the
754 // def part of the instruction as well. However, in some cases, we
755 // aren't allowed to modify the reused register. If none of these cases
757 bool CanReuse = true;
758 int ti = TID->getOperandConstraint(i, TOI::TIED_TO);
760 MI.getOperand(ti).isReg() &&
761 MI.getOperand(ti).getReg() == VirtReg) {
762 // Okay, we have a two address operand. We can reuse this physreg as
763 // long as we are allowed to clobber the value and there isn't an
764 // earlier def that has already clobbered the physreg.
765 CanReuse = Spills.canClobberPhysReg(StackSlot) &&
766 !ReusedOperands.isClobbered(PhysReg);
770 // If this stack slot value is already available, reuse it!
771 if (StackSlot > VirtRegMap::MAX_STACK_SLOT)
772 DOUT << "Reusing RM#" << StackSlot-VirtRegMap::MAX_STACK_SLOT-1;
774 DOUT << "Reusing SS#" << StackSlot;
775 DOUT << " from physreg "
776 << MRI->getName(PhysReg) << " for vreg"
777 << VirtReg <<" instead of reloading into physreg "
778 << MRI->getName(VRM.getPhys(VirtReg)) << "\n";
779 MI.getOperand(i).setReg(PhysReg);
781 // The only technical detail we have is that we don't know that
782 // PhysReg won't be clobbered by a reloaded stack slot that occurs
783 // later in the instruction. In particular, consider 'op V1, V2'.
784 // If V1 is available in physreg R0, we would choose to reuse it
785 // here, instead of reloading it into the register the allocator
786 // indicated (say R1). However, V2 might have to be reloaded
787 // later, and it might indicate that it needs to live in R0. When
788 // this occurs, we need to have information available that
789 // indicates it is safe to use R1 for the reload instead of R0.
791 // To further complicate matters, we might conflict with an alias,
792 // or R0 and R1 might not be compatible with each other. In this
793 // case, we actually insert a reload for V1 in R1, ensuring that
794 // we can get at R0 or its alias.
795 ReusedOperands.addReuse(i, StackSlot, PhysReg,
796 VRM.getPhys(VirtReg), VirtReg);
798 // Only mark it clobbered if this is a use&def operand.
799 ReusedOperands.markClobbered(PhysReg);
804 // Otherwise we have a situation where we have a two-address instruction
805 // whose mod/ref operand needs to be reloaded. This reload is already
806 // available in some register "PhysReg", but if we used PhysReg as the
807 // operand to our 2-addr instruction, the instruction would modify
808 // PhysReg. This isn't cool if something later uses PhysReg and expects
809 // to get its initial value.
811 // To avoid this problem, and to avoid doing a load right after a store,
812 // we emit a copy from PhysReg into the designated register for this
814 unsigned DesignatedReg = VRM.getPhys(VirtReg);
815 assert(DesignatedReg && "Must map virtreg to physreg!");
817 // Note that, if we reused a register for a previous operand, the
818 // register we want to reload into might not actually be
819 // available. If this occurs, use the register indicated by the
821 if (ReusedOperands.hasReuses())
822 DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
823 Spills, MaybeDeadStores);
825 // If the mapped designated register is actually the physreg we have
826 // incoming, we don't need to inserted a dead copy.
827 if (DesignatedReg == PhysReg) {
828 // If this stack slot value is already available, reuse it!
829 if (StackSlot > VirtRegMap::MAX_STACK_SLOT)
830 DOUT << "Reusing RM#" << StackSlot-VirtRegMap::MAX_STACK_SLOT-1;
832 DOUT << "Reusing SS#" << StackSlot;
833 DOUT << " from physreg " << MRI->getName(PhysReg) << " for vreg"
835 << " instead of reloading into same physreg.\n";
836 MI.getOperand(i).setReg(PhysReg);
837 ReusedOperands.markClobbered(PhysReg);
842 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(VirtReg);
843 MF.setPhysRegUsed(DesignatedReg);
844 ReusedOperands.markClobbered(DesignatedReg);
845 MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC);
847 MachineInstr *CopyMI = prior(MII);
848 UpdateKills(*CopyMI, RegKills, KillOps);
850 // This invalidates DesignatedReg.
851 Spills.ClobberPhysReg(DesignatedReg);
853 Spills.addAvailable(StackSlot, &MI, DesignatedReg);
854 MI.getOperand(i).setReg(DesignatedReg);
855 DOUT << '\t' << *prior(MII);
860 // Otherwise, reload it and remember that we have it.
861 PhysReg = VRM.getPhys(VirtReg);
862 assert(PhysReg && "Must map virtreg to physreg!");
863 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(VirtReg);
865 // Note that, if we reused a register for a previous operand, the
866 // register we want to reload into might not actually be
867 // available. If this occurs, use the register indicated by the
869 if (ReusedOperands.hasReuses())
870 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
871 Spills, MaybeDeadStores);
873 MF.setPhysRegUsed(PhysReg);
874 ReusedOperands.markClobbered(PhysReg);
876 MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg));
879 MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
882 // This invalidates PhysReg.
883 Spills.ClobberPhysReg(PhysReg);
885 // Any stores to this stack slot are not dead anymore.
887 MaybeDeadStores.erase(StackSlot);
888 Spills.addAvailable(StackSlot, &MI, PhysReg);
889 // Assumes this is the last use. IsKill will be unset if reg is reused
890 // unless it's a two-address operand.
891 if (TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
892 MI.getOperand(i).setIsKill();
893 MI.getOperand(i).setReg(PhysReg);
894 UpdateKills(*prior(MII), RegKills, KillOps);
895 DOUT << '\t' << *prior(MII);
900 // If we have folded references to memory operands, make sure we clear all
901 // physical registers that may contain the value of the spilled virtual
903 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
904 DOUT << "Folded vreg: " << I->second.first << " MR: "
906 unsigned VirtReg = I->second.first;
907 VirtRegMap::ModRef MR = I->second.second;
908 if (!VRM.hasStackSlot(VirtReg)) {
909 DOUT << ": No stack slot!\n";
912 int SS = VRM.getStackSlot(VirtReg);
913 DOUT << " - StackSlot: " << SS << "\n";
915 // If this folded instruction is just a use, check to see if it's a
916 // straight load from the virt reg slot.
917 if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
919 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
920 if (FrameIdx == SS) {
921 // If this spill slot is available, turn it into a copy (or nothing)
922 // instead of leaving it as a load!
923 if (unsigned InReg = Spills.getSpillSlotPhysReg(SS)) {
924 DOUT << "Promoted Load To Copy: " << MI;
925 if (DestReg != InReg) {
926 MRI->copyRegToReg(MBB, &MI, DestReg, InReg,
927 MF.getSSARegMap()->getRegClass(VirtReg));
928 // Revisit the copy so we make sure to notice the effects of the
929 // operation on the destreg (either needing to RA it if it's
930 // virtual or needing to clobber any values if it's physical).
932 --NextMII; // backtrack to the copy.
935 DOUT << "Removing now-noop copy: " << MI;
937 VRM.RemoveFromFoldedVirtMap(&MI);
940 goto ProcessNextInst;
946 // If this reference is not a use, any previous store is now dead.
947 // Otherwise, the store to this stack slot is not dead anymore.
948 std::map<int, MachineInstr*>::iterator MDSI = MaybeDeadStores.find(SS);
949 if (MDSI != MaybeDeadStores.end()) {
950 if (MR & VirtRegMap::isRef) // Previous store is not dead.
951 MaybeDeadStores.erase(MDSI);
953 // If we get here, the store is dead, nuke it now.
954 assert(VirtRegMap::isMod && "Can't be modref!");
955 DOUT << "Removed dead store:\t" << *MDSI->second;
956 InvalidateKills(*MDSI->second, RegKills, KillOps);
957 MBB.erase(MDSI->second);
958 VRM.RemoveFromFoldedVirtMap(MDSI->second);
959 MaybeDeadStores.erase(MDSI);
964 // If the spill slot value is available, and this is a new definition of
965 // the value, the value is not available anymore.
966 if (MR & VirtRegMap::isMod) {
967 // Notice that the value in this stack slot has been modified.
968 Spills.ModifyStackSlot(SS);
970 // If this is *just* a mod of the value, check to see if this is just a
971 // store to the spill slot (i.e. the spill got merged into the copy). If
972 // so, realize that the vreg is available now, and add the store to the
973 // MaybeDeadStore info.
975 if (!(MR & VirtRegMap::isRef)) {
976 if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
977 assert(MRegisterInfo::isPhysicalRegister(SrcReg) &&
978 "Src hasn't been allocated yet?");
979 // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
980 // this as a potentially dead store in case there is a subsequent
981 // store into the stack slot without a read from it.
982 MaybeDeadStores[StackSlot] = &MI;
984 // If the stack slot value was previously available in some other
985 // register, change it now. Otherwise, make the register available,
987 Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/);
993 // Process all of the spilled defs.
994 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
995 MachineOperand &MO = MI.getOperand(i);
996 if (MO.isRegister() && MO.getReg() && MO.isDef()) {
997 unsigned VirtReg = MO.getReg();
999 if (!MRegisterInfo::isVirtualRegister(VirtReg)) {
1000 // Check to see if this is a noop copy. If so, eliminate the
1001 // instruction before considering the dest reg to be changed.
1003 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1005 DOUT << "Removing now-noop copy: " << MI;
1008 VRM.RemoveFromFoldedVirtMap(&MI);
1009 Spills.disallowClobberPhysReg(VirtReg);
1010 goto ProcessNextInst;
1013 // If it's not a no-op copy, it clobbers the value in the destreg.
1014 Spills.ClobberPhysReg(VirtReg);
1015 ReusedOperands.markClobbered(VirtReg);
1017 // Check to see if this instruction is a load from a stack slot into
1018 // a register. If so, this provides the stack slot value in the reg.
1020 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
1021 assert(DestReg == VirtReg && "Unknown load situation!");
1023 // Otherwise, if it wasn't available, remember that it is now!
1024 Spills.addAvailable(FrameIdx, &MI, DestReg);
1025 goto ProcessNextInst;
1031 // The only vregs left are stack slot definitions.
1032 int StackSlot = VRM.getStackSlot(VirtReg);
1033 const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(VirtReg);
1035 // If this def is part of a two-address operand, make sure to execute
1036 // the store from the correct physical register.
1038 int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i);
1040 PhysReg = MI.getOperand(TiedOp).getReg();
1042 PhysReg = VRM.getPhys(VirtReg);
1043 if (ReusedOperands.isClobbered(PhysReg)) {
1044 // Another def has taken the assigned physreg. It must have been a
1045 // use&def which got it due to reuse. Undo the reuse!
1046 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
1047 Spills, MaybeDeadStores);
1051 MF.setPhysRegUsed(PhysReg);
1052 ReusedOperands.markClobbered(PhysReg);
1053 MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
1054 DOUT << "Store:\t" << *next(MII);
1055 MI.getOperand(i).setReg(PhysReg);
1057 // If there is a dead store to this stack slot, nuke it now.
1058 MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
1060 DOUT << "Removed dead store:\t" << *LastStore;
1062 InvalidateKills(*LastStore, RegKills, KillOps);
1063 MBB.erase(LastStore);
1064 VRM.RemoveFromFoldedVirtMap(LastStore);
1066 LastStore = next(MII);
1068 // If the stack slot value was previously available in some other
1069 // register, change it now. Otherwise, make the register available,
1071 Spills.ModifyStackSlot(StackSlot);
1072 Spills.ClobberPhysReg(PhysReg);
1073 Spills.addAvailable(StackSlot, LastStore, PhysReg);
1076 // Check to see if this is a noop copy. If so, eliminate the
1077 // instruction before considering the dest reg to be changed.
1080 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1082 DOUT << "Removing now-noop copy: " << MI;
1085 VRM.RemoveFromFoldedVirtMap(&MI);
1086 goto ProcessNextInst;
1092 if (!Erased && !BackTracked)
1093 for (MachineBasicBlock::iterator II = MI; II != NextMII; ++II)
1094 UpdateKills(*II, RegKills, KillOps);
1100 llvm::Spiller* llvm::createSpiller() {
1101 switch (SpillerOpt) {
1102 default: assert(0 && "Unreachable!");
1104 return new LocalSpiller();
1106 return new SimpleSpiller();