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 Virt2ReMatIdMap(NO_STACK_SLOT), ReMatMap(NULL),
66 ReMatId(MAX_STACK_SLOT+1) {
70 void VirtRegMap::grow() {
71 unsigned LastVirtReg = MF.getSSARegMap()->getLastVirtReg();
72 Virt2PhysMap.grow(LastVirtReg);
73 Virt2StackSlotMap.grow(LastVirtReg);
74 Virt2ReMatIdMap.grow(LastVirtReg);
75 ReMatMap.grow(LastVirtReg);
78 int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
79 assert(MRegisterInfo::isVirtualRegister(virtReg));
80 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
81 "attempt to assign stack slot to already spilled register");
82 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(virtReg);
83 int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
85 Virt2StackSlotMap[virtReg] = frameIndex;
90 void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) {
91 assert(MRegisterInfo::isVirtualRegister(virtReg));
92 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
93 "attempt to assign stack slot to already spilled register");
94 assert((frameIndex >= 0 ||
95 (frameIndex >= MF.getFrameInfo()->getObjectIndexBegin())) &&
96 "illegal fixed frame index");
97 Virt2StackSlotMap[virtReg] = frameIndex;
100 int VirtRegMap::assignVirtReMatId(unsigned virtReg) {
101 assert(MRegisterInfo::isVirtualRegister(virtReg));
102 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
103 "attempt to assign re-mat id to already spilled register");
104 Virt2ReMatIdMap[virtReg] = ReMatId;
108 void VirtRegMap::assignVirtReMatId(unsigned virtReg, int id) {
109 assert(MRegisterInfo::isVirtualRegister(virtReg));
110 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
111 "attempt to assign re-mat id to already spilled register");
112 Virt2ReMatIdMap[virtReg] = id;
115 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
116 unsigned OpNo, MachineInstr *NewMI) {
117 // Move previous memory references folded to new instruction.
118 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
119 for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
120 E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
121 MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
122 MI2VirtMap.erase(I++);
126 const TargetInstrDescriptor *TID = OldMI->getInstrDescriptor();
127 if (TID->getOperandConstraint(OpNo, TOI::TIED_TO) != -1 ||
128 TID->findTiedToSrcOperand(OpNo) != -1) {
129 // Folded a two-address operand.
131 } else if (OldMI->getOperand(OpNo).isDef()) {
137 // add new memory reference
138 MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
141 void VirtRegMap::print(std::ostream &OS) const {
142 const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
144 OS << "********** REGISTER MAP **********\n";
145 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
146 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) {
147 if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG)
148 OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n";
152 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
153 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i)
154 if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT)
155 OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n";
159 void VirtRegMap::dump() const {
164 //===----------------------------------------------------------------------===//
165 // Simple Spiller Implementation
166 //===----------------------------------------------------------------------===//
168 Spiller::~Spiller() {}
171 struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller {
172 bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM);
176 bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
177 DOUT << "********** REWRITE MACHINE CODE **********\n";
178 DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
179 const TargetMachine &TM = MF.getTarget();
180 const MRegisterInfo &MRI = *TM.getRegisterInfo();
182 // LoadedRegs - Keep track of which vregs are loaded, so that we only load
183 // each vreg once (in the case where a spilled vreg is used by multiple
184 // operands). This is always smaller than the number of operands to the
185 // current machine instr, so it should be small.
186 std::vector<unsigned> LoadedRegs;
188 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
190 DOUT << MBBI->getBasicBlock()->getName() << ":\n";
191 MachineBasicBlock &MBB = *MBBI;
192 for (MachineBasicBlock::iterator MII = MBB.begin(),
193 E = MBB.end(); MII != E; ++MII) {
194 MachineInstr &MI = *MII;
195 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
196 MachineOperand &MO = MI.getOperand(i);
197 if (MO.isRegister() && MO.getReg())
198 if (MRegisterInfo::isVirtualRegister(MO.getReg())) {
199 unsigned VirtReg = MO.getReg();
200 unsigned PhysReg = VRM.getPhys(VirtReg);
201 if (!VRM.isAssignedReg(VirtReg)) {
202 int StackSlot = VRM.getStackSlot(VirtReg);
203 const TargetRegisterClass* RC =
204 MF.getSSARegMap()->getRegClass(VirtReg);
207 std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
208 == LoadedRegs.end()) {
209 MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
210 LoadedRegs.push_back(VirtReg);
212 DOUT << '\t' << *prior(MII);
216 MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
220 MF.setPhysRegUsed(PhysReg);
221 MI.getOperand(i).setReg(PhysReg);
223 MF.setPhysRegUsed(MO.getReg());
234 //===----------------------------------------------------------------------===//
235 // Local Spiller Implementation
236 //===----------------------------------------------------------------------===//
239 /// LocalSpiller - This spiller does a simple pass over the machine basic
240 /// block to attempt to keep spills in registers as much as possible for
241 /// blocks that have low register pressure (the vreg may be spilled due to
242 /// register pressure in other blocks).
243 class VISIBILITY_HIDDEN LocalSpiller : public Spiller {
244 const MRegisterInfo *MRI;
245 const TargetInstrInfo *TII;
247 bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
248 MRI = MF.getTarget().getRegisterInfo();
249 TII = MF.getTarget().getInstrInfo();
250 DOUT << "\n**** Local spiller rewriting function '"
251 << MF.getFunction()->getName() << "':\n";
253 for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
255 RewriteMBB(*MBB, VRM);
259 void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
263 /// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
264 /// top down, keep track of which spills slots or remat are available in each
267 /// Note that not all physregs are created equal here. In particular, some
268 /// physregs are reloads that we are allowed to clobber or ignore at any time.
269 /// Other physregs are values that the register allocated program is using that
270 /// we cannot CHANGE, but we can read if we like. We keep track of this on a
271 /// per-stack-slot / remat id basis as the low bit in the value of the
272 /// SpillSlotsAvailable entries. The predicate 'canClobberPhysReg()' checks
273 /// this bit and addAvailable sets it if.
275 class VISIBILITY_HIDDEN AvailableSpills {
276 const MRegisterInfo *MRI;
277 const TargetInstrInfo *TII;
279 // SpillSlotsOrReMatsAvailable - This map keeps track of all of the spilled
280 // or remat'ed virtual register values that are still available, due to being
281 // loaded or stored to, but not invalidated yet.
282 std::map<int, unsigned> SpillSlotsOrReMatsAvailable;
284 // PhysRegsAvailable - This is the inverse of SpillSlotsOrReMatsAvailable,
285 // indicating which stack slot values are currently held by a physreg. This
286 // is used to invalidate entries in SpillSlotsOrReMatsAvailable when a
287 // physreg is modified.
288 std::multimap<unsigned, int> PhysRegsAvailable;
290 void disallowClobberPhysRegOnly(unsigned PhysReg);
292 void ClobberPhysRegOnly(unsigned PhysReg);
294 AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
295 : MRI(mri), TII(tii) {
298 const MRegisterInfo *getRegInfo() const { return MRI; }
300 /// getSpillSlotOrReMatPhysReg - If the specified stack slot or remat is
301 /// available in a physical register, return that PhysReg, otherwise
303 unsigned getSpillSlotOrReMatPhysReg(int Slot) const {
304 std::map<int, unsigned>::const_iterator I =
305 SpillSlotsOrReMatsAvailable.find(Slot);
306 if (I != SpillSlotsOrReMatsAvailable.end()) {
307 return I->second >> 1; // Remove the CanClobber bit.
312 /// addAvailable - Mark that the specified stack slot / remat is available in
313 /// the specified physreg. If CanClobber is true, the physreg can be modified
314 /// at any time without changing the semantics of the program.
315 void addAvailable(int SlotOrReMat, MachineInstr *MI, unsigned Reg,
316 bool CanClobber = true) {
317 // If this stack slot is thought to be available in some other physreg,
318 // remove its record.
319 ModifyStackSlotOrReMat(SlotOrReMat);
321 PhysRegsAvailable.insert(std::make_pair(Reg, SlotOrReMat));
322 SpillSlotsOrReMatsAvailable[SlotOrReMat] = (Reg << 1) | (unsigned)CanClobber;
324 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
325 DOUT << "Remembering RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1;
327 DOUT << "Remembering SS#" << SlotOrReMat;
328 DOUT << " in physreg " << MRI->getName(Reg) << "\n";
331 /// canClobberPhysReg - Return true if the spiller is allowed to change the
332 /// value of the specified stackslot register if it desires. The specified
333 /// stack slot must be available in a physreg for this query to make sense.
334 bool canClobberPhysReg(int SlotOrReMat) const {
335 assert(SpillSlotsOrReMatsAvailable.count(SlotOrReMat) && "Value not available!");
336 return SpillSlotsOrReMatsAvailable.find(SlotOrReMat)->second & 1;
339 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
340 /// stackslot register. The register is still available but is no longer
341 /// allowed to be modifed.
342 void disallowClobberPhysReg(unsigned PhysReg);
344 /// ClobberPhysReg - This is called when the specified physreg changes
345 /// value. We use this to invalidate any info about stuff we thing lives in
346 /// it and any of its aliases.
347 void ClobberPhysReg(unsigned PhysReg);
349 /// ModifyStackSlotOrReMat - This method is called when the value in a stack slot
350 /// changes. This removes information about which register the previous value
351 /// for this slot lives in (as the previous value is dead now).
352 void ModifyStackSlotOrReMat(int SlotOrReMat);
356 /// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
357 /// stackslot register. The register is still available but is no longer
358 /// allowed to be modifed.
359 void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
360 std::multimap<unsigned, int>::iterator I =
361 PhysRegsAvailable.lower_bound(PhysReg);
362 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
363 int SlotOrReMat = I->second;
365 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
366 "Bidirectional map mismatch!");
367 SpillSlotsOrReMatsAvailable[SlotOrReMat] &= ~1;
368 DOUT << "PhysReg " << MRI->getName(PhysReg)
369 << " copied, it is available for use but can no longer be modified\n";
373 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
374 /// stackslot register and its aliases. The register and its aliases may
375 /// still available but is no longer allowed to be modifed.
376 void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
377 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
378 disallowClobberPhysRegOnly(*AS);
379 disallowClobberPhysRegOnly(PhysReg);
382 /// ClobberPhysRegOnly - This is called when the specified physreg changes
383 /// value. We use this to invalidate any info about stuff we thing lives in it.
384 void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
385 std::multimap<unsigned, int>::iterator I =
386 PhysRegsAvailable.lower_bound(PhysReg);
387 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
388 int SlotOrReMat = I->second;
389 PhysRegsAvailable.erase(I++);
390 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
391 "Bidirectional map mismatch!");
392 SpillSlotsOrReMatsAvailable.erase(SlotOrReMat);
393 DOUT << "PhysReg " << MRI->getName(PhysReg)
394 << " clobbered, invalidating ";
395 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
396 DOUT << "RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1 << "\n";
398 DOUT << "SS#" << SlotOrReMat << "\n";
402 /// ClobberPhysReg - This is called when the specified physreg changes
403 /// value. We use this to invalidate any info about stuff we thing lives in
404 /// it and any of its aliases.
405 void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
406 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
407 ClobberPhysRegOnly(*AS);
408 ClobberPhysRegOnly(PhysReg);
411 /// ModifyStackSlotOrReMat - This method is called when the value in a stack slot
412 /// changes. This removes information about which register the previous value
413 /// for this slot lives in (as the previous value is dead now).
414 void AvailableSpills::ModifyStackSlotOrReMat(int SlotOrReMat) {
415 std::map<int, unsigned>::iterator It = SpillSlotsOrReMatsAvailable.find(SlotOrReMat);
416 if (It == SpillSlotsOrReMatsAvailable.end()) return;
417 unsigned Reg = It->second >> 1;
418 SpillSlotsOrReMatsAvailable.erase(It);
420 // This register may hold the value of multiple stack slots, only remove this
421 // stack slot from the set of values the register contains.
422 std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
424 assert(I != PhysRegsAvailable.end() && I->first == Reg &&
425 "Map inverse broken!");
426 if (I->second == SlotOrReMat) break;
428 PhysRegsAvailable.erase(I);
433 /// InvalidateKills - MI is going to be deleted. If any of its operands are
434 /// marked kill, then invalidate the information.
435 static void InvalidateKills(MachineInstr &MI, BitVector &RegKills,
436 std::vector<MachineOperand*> &KillOps) {
437 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
438 MachineOperand &MO = MI.getOperand(i);
439 if (!MO.isReg() || !MO.isUse() || !MO.isKill())
441 unsigned Reg = MO.getReg();
442 if (KillOps[Reg] == &MO) {
449 /// UpdateKills - Track and update kill info. If a MI reads a register that is
450 /// marked kill, then it must be due to register reuse. Transfer the kill info
452 static void UpdateKills(MachineInstr &MI, BitVector &RegKills,
453 std::vector<MachineOperand*> &KillOps) {
454 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
455 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
456 MachineOperand &MO = MI.getOperand(i);
457 if (!MO.isReg() || !MO.isUse())
459 unsigned Reg = MO.getReg();
464 // That can't be right. Register is killed but not re-defined and it's
465 // being reused. Let's fix that.
466 KillOps[Reg]->unsetIsKill();
467 if (i < TID->numOperands &&
468 TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
469 // Unless it's a two-address operand, this is the new kill.
479 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
480 const MachineOperand &MO = MI.getOperand(i);
481 if (!MO.isReg() || !MO.isDef())
483 unsigned Reg = MO.getReg();
490 // ReusedOp - For each reused operand, we keep track of a bit of information, in
491 // case we need to rollback upon processing a new operand. See comments below.
494 // The MachineInstr operand that reused an available value.
497 // StackSlotOrReMat - The spill slot or remat id of the value being reused.
498 unsigned StackSlotOrReMat;
500 // PhysRegReused - The physical register the value was available in.
501 unsigned PhysRegReused;
503 // AssignedPhysReg - The physreg that was assigned for use by the reload.
504 unsigned AssignedPhysReg;
506 // VirtReg - The virtual register itself.
509 ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
511 : Operand(o), StackSlotOrReMat(ss), PhysRegReused(prr), AssignedPhysReg(apr),
515 /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
516 /// is reused instead of reloaded.
517 class VISIBILITY_HIDDEN ReuseInfo {
519 std::vector<ReusedOp> Reuses;
520 BitVector PhysRegsClobbered;
522 ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
523 PhysRegsClobbered.resize(mri->getNumRegs());
526 bool hasReuses() const {
527 return !Reuses.empty();
530 /// addReuse - If we choose to reuse a virtual register that is already
531 /// available instead of reloading it, remember that we did so.
532 void addReuse(unsigned OpNo, unsigned StackSlotOrReMat,
533 unsigned PhysRegReused, unsigned AssignedPhysReg,
535 // If the reload is to the assigned register anyway, no undo will be
537 if (PhysRegReused == AssignedPhysReg) return;
539 // Otherwise, remember this.
540 Reuses.push_back(ReusedOp(OpNo, StackSlotOrReMat, PhysRegReused,
541 AssignedPhysReg, VirtReg));
544 void markClobbered(unsigned PhysReg) {
545 PhysRegsClobbered.set(PhysReg);
548 bool isClobbered(unsigned PhysReg) const {
549 return PhysRegsClobbered.test(PhysReg);
552 /// GetRegForReload - We are about to emit a reload into PhysReg. If there
553 /// is some other operand that is using the specified register, either pick
554 /// a new register to use, or evict the previous reload and use this reg.
555 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
556 AvailableSpills &Spills,
557 std::vector<MachineInstr*> &MaybeDeadStores,
558 SmallSet<unsigned, 8> &Rejected,
560 std::vector<MachineOperand*> &KillOps,
562 if (Reuses.empty()) return PhysReg; // This is most often empty.
564 for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
565 ReusedOp &Op = Reuses[ro];
566 // If we find some other reuse that was supposed to use this register
567 // exactly for its reload, we can change this reload to use ITS reload
568 // register. That is, unless its reload register has already been
569 // considered and subsequently rejected because it has also been reused
570 // by another operand.
571 if (Op.PhysRegReused == PhysReg &&
572 Rejected.count(Op.AssignedPhysReg) == 0) {
573 // Yup, use the reload register that we didn't use before.
574 unsigned NewReg = Op.AssignedPhysReg;
575 Rejected.insert(PhysReg);
576 return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected,
577 RegKills, KillOps, VRM);
579 // Otherwise, we might also have a problem if a previously reused
580 // value aliases the new register. If so, codegen the previous reload
582 unsigned PRRU = Op.PhysRegReused;
583 const MRegisterInfo *MRI = Spills.getRegInfo();
584 if (MRI->areAliases(PRRU, PhysReg)) {
585 // Okay, we found out that an alias of a reused register
586 // was used. This isn't good because it means we have
587 // to undo a previous reuse.
588 MachineBasicBlock *MBB = MI->getParent();
589 const TargetRegisterClass *AliasRC =
590 MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
592 // Copy Op out of the vector and remove it, we're going to insert an
593 // explicit load for it.
595 Reuses.erase(Reuses.begin()+ro);
597 // Ok, we're going to try to reload the assigned physreg into the
598 // slot that we were supposed to in the first place. However, that
599 // register could hold a reuse. Check to see if it conflicts or
600 // would prefer us to use a different register.
601 unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
602 MI, Spills, MaybeDeadStores,
603 Rejected, RegKills, KillOps, VRM);
605 if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) {
606 MRI->reMaterialize(*MBB, MI, NewPhysReg,
607 VRM.getReMaterializedMI(NewOp.VirtReg));
610 MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg,
611 NewOp.StackSlotOrReMat, AliasRC);
612 // Any stores to this stack slot are not dead anymore.
613 MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL;
616 Spills.ClobberPhysReg(NewPhysReg);
617 Spills.ClobberPhysReg(NewOp.PhysRegReused);
619 MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
621 Spills.addAvailable(NewOp.StackSlotOrReMat, MI, NewPhysReg);
622 MachineBasicBlock::iterator MII = MI;
624 UpdateKills(*MII, RegKills, KillOps);
625 DOUT << '\t' << *MII;
627 DOUT << "Reuse undone!\n";
630 // Finally, PhysReg is now available, go ahead and use it.
638 /// GetRegForReload - Helper for the above GetRegForReload(). Add a
639 /// 'Rejected' set to remember which registers have been considered and
640 /// rejected for the reload. This avoids infinite looping in case like
643 /// t2 <- assigned r0 for use by the reload but ended up reuse r1
644 /// t3 <- assigned r1 for use by the reload but ended up reuse r0
646 /// sees r1 is taken by t2, tries t2's reload register r0
647 /// sees r0 is taken by t3, tries t3's reload register r1
648 /// sees r1 is taken by t2, tries t2's reload register r0 ...
649 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
650 AvailableSpills &Spills,
651 std::vector<MachineInstr*> &MaybeDeadStores,
653 std::vector<MachineOperand*> &KillOps,
655 SmallSet<unsigned, 8> Rejected;
656 return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected,
657 RegKills, KillOps, VRM);
663 /// rewriteMBB - Keep track of which spills are available even after the
664 /// register allocator is done with them. If possible, avoid reloading vregs.
665 void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
666 DOUT << MBB.getBasicBlock()->getName() << ":\n";
668 MachineFunction &MF = *MBB.getParent();
670 // Spills - Keep track of which spilled values are available in physregs so
671 // that we can choose to reuse the physregs instead of emitting reloads.
672 AvailableSpills Spills(MRI, TII);
674 // MaybeDeadStores - When we need to write a value back into a stack slot,
675 // keep track of the inserted store. If the stack slot value is never read
676 // (because the value was used from some available register, for example), and
677 // subsequently stored to, the original store is dead. This map keeps track
678 // of inserted stores that are not used. If we see a subsequent store to the
679 // same stack slot, the original store is deleted.
680 std::vector<MachineInstr*> MaybeDeadStores;
681 MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL);
683 // Keep track of kill information.
684 BitVector RegKills(MRI->getNumRegs());
685 std::vector<MachineOperand*> KillOps;
686 KillOps.resize(MRI->getNumRegs(), NULL);
688 for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
690 MachineInstr &MI = *MII;
691 MachineBasicBlock::iterator NextMII = MII; ++NextMII;
692 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
695 bool BackTracked = false;
697 /// ReusedOperands - Keep track of operand reuse in case we need to undo
699 ReuseInfo ReusedOperands(MI, MRI);
701 // Loop over all of the implicit defs, clearing them from our available
703 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
704 if (TID->ImplicitDefs) {
705 const unsigned *ImpDef = TID->ImplicitDefs;
706 for ( ; *ImpDef; ++ImpDef) {
707 MF.setPhysRegUsed(*ImpDef);
708 ReusedOperands.markClobbered(*ImpDef);
709 Spills.ClobberPhysReg(*ImpDef);
713 // Process all of the spilled uses and all non spilled reg references.
714 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
715 MachineOperand &MO = MI.getOperand(i);
716 if (!MO.isRegister() || MO.getReg() == 0)
717 continue; // Ignore non-register operands.
719 if (MRegisterInfo::isPhysicalRegister(MO.getReg())) {
720 // Ignore physregs for spilling, but remember that it is used by this
722 MF.setPhysRegUsed(MO.getReg());
723 ReusedOperands.markClobbered(MO.getReg());
727 assert(MRegisterInfo::isVirtualRegister(MO.getReg()) &&
728 "Not a virtual or a physical register?");
730 unsigned VirtReg = MO.getReg();
731 if (VRM.isAssignedReg(VirtReg)) {
732 // This virtual register was assigned a physreg!
733 unsigned Phys = VRM.getPhys(VirtReg);
734 MF.setPhysRegUsed(Phys);
736 ReusedOperands.markClobbered(Phys);
737 MI.getOperand(i).setReg(Phys);
741 // This virtual register is now known to be a spilled value.
743 continue; // Handle defs in the loop below (handle use&def here though)
745 bool DoReMat = VRM.isReMaterialized(VirtReg);
746 int SSorRMId = DoReMat
747 ? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
748 int ReuseSlot = SSorRMId;
750 // Check to see if this stack slot is available.
751 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
752 if (!PhysReg && DoReMat) {
753 // This use is rematerializable. But perhaps the value is available in
754 // stack if the definition is not deleted. If so, check if we can
756 ReuseSlot = VRM.getStackSlot(VirtReg);
757 if (ReuseSlot != VirtRegMap::NO_STACK_SLOT)
758 PhysReg = Spills.getSpillSlotOrReMatPhysReg(ReuseSlot);
761 // This spilled operand might be part of a two-address operand. If this
762 // is the case, then changing it will necessarily require changing the
763 // def part of the instruction as well. However, in some cases, we
764 // aren't allowed to modify the reused register. If none of these cases
766 bool CanReuse = true;
767 int ti = TID->getOperandConstraint(i, TOI::TIED_TO);
769 MI.getOperand(ti).isReg() &&
770 MI.getOperand(ti).getReg() == VirtReg) {
771 // Okay, we have a two address operand. We can reuse this physreg as
772 // long as we are allowed to clobber the value and there isn't an
773 // earlier def that has already clobbered the physreg.
774 CanReuse = Spills.canClobberPhysReg(ReuseSlot) &&
775 !ReusedOperands.isClobbered(PhysReg);
779 // If this stack slot value is already available, reuse it!
780 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
781 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
783 DOUT << "Reusing SS#" << ReuseSlot;
784 DOUT << " from physreg "
785 << MRI->getName(PhysReg) << " for vreg"
786 << VirtReg <<" instead of reloading into physreg "
787 << MRI->getName(VRM.getPhys(VirtReg)) << "\n";
788 MI.getOperand(i).setReg(PhysReg);
790 // The only technical detail we have is that we don't know that
791 // PhysReg won't be clobbered by a reloaded stack slot that occurs
792 // later in the instruction. In particular, consider 'op V1, V2'.
793 // If V1 is available in physreg R0, we would choose to reuse it
794 // here, instead of reloading it into the register the allocator
795 // indicated (say R1). However, V2 might have to be reloaded
796 // later, and it might indicate that it needs to live in R0. When
797 // this occurs, we need to have information available that
798 // indicates it is safe to use R1 for the reload instead of R0.
800 // To further complicate matters, we might conflict with an alias,
801 // or R0 and R1 might not be compatible with each other. In this
802 // case, we actually insert a reload for V1 in R1, ensuring that
803 // we can get at R0 or its alias.
804 ReusedOperands.addReuse(i, ReuseSlot, PhysReg,
805 VRM.getPhys(VirtReg), VirtReg);
807 // Only mark it clobbered if this is a use&def operand.
808 ReusedOperands.markClobbered(PhysReg);
811 if (MI.getOperand(i).isKill() &&
812 ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) {
813 // This was the last use and the spilled value is still available
814 // for reuse. That means the spill was unnecessary!
815 MachineInstr* DeadStore = MaybeDeadStores[ReuseSlot];
817 DOUT << "Removed dead store:\t" << *DeadStore;
818 InvalidateKills(*DeadStore, RegKills, KillOps);
819 MBB.erase(DeadStore);
820 VRM.RemoveFromFoldedVirtMap(DeadStore);
821 MaybeDeadStores[ReuseSlot] = NULL;
828 // Otherwise we have a situation where we have a two-address instruction
829 // whose mod/ref operand needs to be reloaded. This reload is already
830 // available in some register "PhysReg", but if we used PhysReg as the
831 // operand to our 2-addr instruction, the instruction would modify
832 // PhysReg. This isn't cool if something later uses PhysReg and expects
833 // to get its initial value.
835 // To avoid this problem, and to avoid doing a load right after a store,
836 // we emit a copy from PhysReg into the designated register for this
838 unsigned DesignatedReg = VRM.getPhys(VirtReg);
839 assert(DesignatedReg && "Must map virtreg to physreg!");
841 // Note that, if we reused a register for a previous operand, the
842 // register we want to reload into might not actually be
843 // available. If this occurs, use the register indicated by the
845 if (ReusedOperands.hasReuses())
846 DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
847 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
849 // If the mapped designated register is actually the physreg we have
850 // incoming, we don't need to inserted a dead copy.
851 if (DesignatedReg == PhysReg) {
852 // If this stack slot value is already available, reuse it!
853 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
854 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
856 DOUT << "Reusing SS#" << ReuseSlot;
857 DOUT << " from physreg " << MRI->getName(PhysReg) << " for vreg"
859 << " instead of reloading into same physreg.\n";
860 MI.getOperand(i).setReg(PhysReg);
861 ReusedOperands.markClobbered(PhysReg);
866 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(VirtReg);
867 MF.setPhysRegUsed(DesignatedReg);
868 ReusedOperands.markClobbered(DesignatedReg);
869 MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC);
871 MachineInstr *CopyMI = prior(MII);
872 UpdateKills(*CopyMI, RegKills, KillOps);
874 // This invalidates DesignatedReg.
875 Spills.ClobberPhysReg(DesignatedReg);
877 Spills.addAvailable(ReuseSlot, &MI, DesignatedReg);
878 MI.getOperand(i).setReg(DesignatedReg);
879 DOUT << '\t' << *prior(MII);
884 // Otherwise, reload it and remember that we have it.
885 PhysReg = VRM.getPhys(VirtReg);
886 assert(PhysReg && "Must map virtreg to physreg!");
887 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(VirtReg);
889 // Note that, if we reused a register for a previous operand, the
890 // register we want to reload into might not actually be
891 // available. If this occurs, use the register indicated by the
893 if (ReusedOperands.hasReuses())
894 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
895 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
897 MF.setPhysRegUsed(PhysReg);
898 ReusedOperands.markClobbered(PhysReg);
900 MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg));
903 MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, SSorRMId, RC);
906 // This invalidates PhysReg.
907 Spills.ClobberPhysReg(PhysReg);
909 // Any stores to this stack slot are not dead anymore.
911 MaybeDeadStores[SSorRMId] = NULL;
912 Spills.addAvailable(SSorRMId, &MI, PhysReg);
913 // Assumes this is the last use. IsKill will be unset if reg is reused
914 // unless it's a two-address operand.
915 if (TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
916 MI.getOperand(i).setIsKill();
917 MI.getOperand(i).setReg(PhysReg);
918 UpdateKills(*prior(MII), RegKills, KillOps);
919 DOUT << '\t' << *prior(MII);
924 // If we have folded references to memory operands, make sure we clear all
925 // physical registers that may contain the value of the spilled virtual
927 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
928 DOUT << "Folded vreg: " << I->second.first << " MR: "
930 unsigned VirtReg = I->second.first;
931 VirtRegMap::ModRef MR = I->second.second;
932 if (VRM.isAssignedReg(VirtReg)) {
933 DOUT << ": No stack slot!\n";
936 int SS = VRM.getStackSlot(VirtReg);
937 DOUT << " - StackSlot: " << SS << "\n";
939 // If this folded instruction is just a use, check to see if it's a
940 // straight load from the virt reg slot.
941 if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
943 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
944 if (FrameIdx == SS) {
945 // If this spill slot is available, turn it into a copy (or nothing)
946 // instead of leaving it as a load!
947 if (unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SS)) {
948 DOUT << "Promoted Load To Copy: " << MI;
949 if (DestReg != InReg) {
950 MRI->copyRegToReg(MBB, &MI, DestReg, InReg,
951 MF.getSSARegMap()->getRegClass(VirtReg));
952 // Revisit the copy so we make sure to notice the effects of the
953 // operation on the destreg (either needing to RA it if it's
954 // virtual or needing to clobber any values if it's physical).
956 --NextMII; // backtrack to the copy.
959 DOUT << "Removing now-noop copy: " << MI;
961 VRM.RemoveFromFoldedVirtMap(&MI);
964 goto ProcessNextInst;
970 // If this reference is not a use, any previous store is now dead.
971 // Otherwise, the store to this stack slot is not dead anymore.
972 MachineInstr* DeadStore = MaybeDeadStores[SS];
974 if (!(MR & VirtRegMap::isRef)) { // Previous store is dead.
975 // If we get here, the store is dead, nuke it now.
976 assert(VirtRegMap::isMod && "Can't be modref!");
977 DOUT << "Removed dead store:\t" << *DeadStore;
978 InvalidateKills(*DeadStore, RegKills, KillOps);
979 MBB.erase(DeadStore);
980 VRM.RemoveFromFoldedVirtMap(DeadStore);
983 MaybeDeadStores[SS] = NULL;
986 // If the spill slot value is available, and this is a new definition of
987 // the value, the value is not available anymore.
988 if (MR & VirtRegMap::isMod) {
989 // Notice that the value in this stack slot has been modified.
990 Spills.ModifyStackSlotOrReMat(SS);
992 // If this is *just* a mod of the value, check to see if this is just a
993 // store to the spill slot (i.e. the spill got merged into the copy). If
994 // so, realize that the vreg is available now, and add the store to the
995 // MaybeDeadStore info.
997 if (!(MR & VirtRegMap::isRef)) {
998 if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
999 assert(MRegisterInfo::isPhysicalRegister(SrcReg) &&
1000 "Src hasn't been allocated yet?");
1001 // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
1002 // this as a potentially dead store in case there is a subsequent
1003 // store into the stack slot without a read from it.
1004 MaybeDeadStores[StackSlot] = &MI;
1006 // If the stack slot value was previously available in some other
1007 // register, change it now. Otherwise, make the register available,
1009 Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/);
1015 // Process all of the spilled defs.
1016 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
1017 MachineOperand &MO = MI.getOperand(i);
1018 if (MO.isRegister() && MO.getReg() && MO.isDef()) {
1019 unsigned VirtReg = MO.getReg();
1021 if (!MRegisterInfo::isVirtualRegister(VirtReg)) {
1022 // Check to see if this is a noop copy. If so, eliminate the
1023 // instruction before considering the dest reg to be changed.
1025 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1027 DOUT << "Removing now-noop copy: " << MI;
1030 VRM.RemoveFromFoldedVirtMap(&MI);
1031 Spills.disallowClobberPhysReg(VirtReg);
1032 goto ProcessNextInst;
1035 // If it's not a no-op copy, it clobbers the value in the destreg.
1036 Spills.ClobberPhysReg(VirtReg);
1037 ReusedOperands.markClobbered(VirtReg);
1039 // Check to see if this instruction is a load from a stack slot into
1040 // a register. If so, this provides the stack slot value in the reg.
1042 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
1043 assert(DestReg == VirtReg && "Unknown load situation!");
1045 // Otherwise, if it wasn't available, remember that it is now!
1046 Spills.addAvailable(FrameIdx, &MI, DestReg);
1047 goto ProcessNextInst;
1053 // The only vregs left are stack slot definitions.
1054 int StackSlot = VRM.getStackSlot(VirtReg);
1055 const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(VirtReg);
1057 // If this def is part of a two-address operand, make sure to execute
1058 // the store from the correct physical register.
1060 int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i);
1062 PhysReg = MI.getOperand(TiedOp).getReg();
1064 PhysReg = VRM.getPhys(VirtReg);
1065 if (ReusedOperands.isClobbered(PhysReg)) {
1066 // Another def has taken the assigned physreg. It must have been a
1067 // use&def which got it due to reuse. Undo the reuse!
1068 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
1069 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
1073 MF.setPhysRegUsed(PhysReg);
1074 ReusedOperands.markClobbered(PhysReg);
1075 MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
1076 DOUT << "Store:\t" << *next(MII);
1077 MI.getOperand(i).setReg(PhysReg);
1079 // If there is a dead store to this stack slot, nuke it now.
1080 MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
1082 DOUT << "Removed dead store:\t" << *LastStore;
1084 InvalidateKills(*LastStore, RegKills, KillOps);
1085 MBB.erase(LastStore);
1086 VRM.RemoveFromFoldedVirtMap(LastStore);
1088 LastStore = next(MII);
1090 // If the stack slot value was previously available in some other
1091 // register, change it now. Otherwise, make the register available,
1093 Spills.ModifyStackSlotOrReMat(StackSlot);
1094 Spills.ClobberPhysReg(PhysReg);
1095 Spills.addAvailable(StackSlot, LastStore, PhysReg);
1098 // Check to see if this is a noop copy. If so, eliminate the
1099 // instruction before considering the dest reg to be changed.
1102 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1104 DOUT << "Removing now-noop copy: " << MI;
1107 VRM.RemoveFromFoldedVirtMap(&MI);
1108 UpdateKills(*LastStore, RegKills, KillOps);
1109 goto ProcessNextInst;
1115 if (!Erased && !BackTracked)
1116 for (MachineBasicBlock::iterator II = MI; II != NextMII; ++II)
1117 UpdateKills(*II, RegKills, KillOps);
1123 llvm::Spiller* llvm::createSpiller() {
1124 switch (SpillerOpt) {
1125 default: assert(0 && "Unreachable!");
1127 return new LocalSpiller();
1129 return new SimpleSpiller();