1 //===-- llvm/CodeGen/VirtRegMap.cpp - Virtual Register Map ----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the VirtRegMap class.
12 // It also contains implementations of the the Spiller interface, which, given a
13 // virtual register map and a machine function, eliminates all virtual
14 // references by replacing them with physical register references - adding spill
17 //===----------------------------------------------------------------------===//
19 #define DEBUG_TYPE "spiller"
20 #include "VirtRegMap.h"
21 #include "llvm/Function.h"
22 #include "llvm/CodeGen/MachineFrameInfo.h"
23 #include "llvm/CodeGen/MachineFunction.h"
24 #include "llvm/CodeGen/SSARegMap.h"
25 #include "llvm/Target/TargetMachine.h"
26 #include "llvm/Target/TargetInstrInfo.h"
27 #include "llvm/Support/CommandLine.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/Compiler.h"
30 #include "llvm/ADT/BitVector.h"
31 #include "llvm/ADT/Statistic.h"
32 #include "llvm/ADT/STLExtras.h"
33 #include "llvm/ADT/SmallSet.h"
37 STATISTIC(NumSpills, "Number of register spills");
38 STATISTIC(NumReMats, "Number of re-materialization");
39 STATISTIC(NumDRM , "Number of re-materializable defs elided");
40 STATISTIC(NumStores, "Number of stores added");
41 STATISTIC(NumLoads , "Number of loads added");
42 STATISTIC(NumReused, "Number of values reused");
43 STATISTIC(NumDSE , "Number of dead stores elided");
44 STATISTIC(NumDCE , "Number of copies elided");
47 enum SpillerName { simple, local };
49 static cl::opt<SpillerName>
51 cl::desc("Spiller to use: (default: local)"),
53 cl::values(clEnumVal(simple, " simple spiller"),
54 clEnumVal(local, " local spiller"),
59 //===----------------------------------------------------------------------===//
60 // VirtRegMap implementation
61 //===----------------------------------------------------------------------===//
63 VirtRegMap::VirtRegMap(MachineFunction &mf)
64 : TII(*mf.getTarget().getInstrInfo()), MF(mf),
65 Virt2PhysMap(NO_PHYS_REG), Virt2StackSlotMap(NO_STACK_SLOT),
66 Virt2ReMatIdMap(NO_STACK_SLOT), ReMatMap(NULL),
67 ReMatId(MAX_STACK_SLOT+1) {
71 void VirtRegMap::grow() {
72 unsigned LastVirtReg = MF.getSSARegMap()->getLastVirtReg();
73 Virt2PhysMap.grow(LastVirtReg);
74 Virt2StackSlotMap.grow(LastVirtReg);
75 Virt2ReMatIdMap.grow(LastVirtReg);
76 ReMatMap.grow(LastVirtReg);
79 int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
80 assert(MRegisterInfo::isVirtualRegister(virtReg));
81 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
82 "attempt to assign stack slot to already spilled register");
83 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(virtReg);
84 int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
86 Virt2StackSlotMap[virtReg] = frameIndex;
91 void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) {
92 assert(MRegisterInfo::isVirtualRegister(virtReg));
93 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
94 "attempt to assign stack slot to already spilled register");
95 assert((frameIndex >= 0 ||
96 (frameIndex >= MF.getFrameInfo()->getObjectIndexBegin())) &&
97 "illegal fixed frame index");
98 Virt2StackSlotMap[virtReg] = frameIndex;
101 int VirtRegMap::assignVirtReMatId(unsigned virtReg) {
102 assert(MRegisterInfo::isVirtualRegister(virtReg));
103 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
104 "attempt to assign re-mat id to already spilled register");
105 Virt2ReMatIdMap[virtReg] = ReMatId;
109 void VirtRegMap::assignVirtReMatId(unsigned virtReg, int id) {
110 assert(MRegisterInfo::isVirtualRegister(virtReg));
111 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
112 "attempt to assign re-mat id to already spilled register");
113 Virt2ReMatIdMap[virtReg] = id;
116 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
117 unsigned OpNo, MachineInstr *NewMI) {
118 // Move previous memory references folded to new instruction.
119 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
120 for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
121 E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
122 MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
123 MI2VirtMap.erase(I++);
127 const TargetInstrDescriptor *TID = OldMI->getInstrDescriptor();
128 if (TID->getOperandConstraint(OpNo, TOI::TIED_TO) != -1 ||
129 TID->findTiedToSrcOperand(OpNo) != -1) {
130 // Folded a two-address operand.
132 } else if (OldMI->getOperand(OpNo).isDef()) {
138 // add new memory reference
139 MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
142 void VirtRegMap::print(std::ostream &OS) const {
143 const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
145 OS << "********** REGISTER MAP **********\n";
146 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
147 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) {
148 if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG)
149 OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n";
153 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
154 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i)
155 if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT)
156 OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n";
160 void VirtRegMap::dump() const {
165 //===----------------------------------------------------------------------===//
166 // Simple Spiller Implementation
167 //===----------------------------------------------------------------------===//
169 Spiller::~Spiller() {}
172 struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller {
173 bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM);
177 bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
178 DOUT << "********** REWRITE MACHINE CODE **********\n";
179 DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
180 const TargetMachine &TM = MF.getTarget();
181 const MRegisterInfo &MRI = *TM.getRegisterInfo();
183 // LoadedRegs - Keep track of which vregs are loaded, so that we only load
184 // each vreg once (in the case where a spilled vreg is used by multiple
185 // operands). This is always smaller than the number of operands to the
186 // current machine instr, so it should be small.
187 std::vector<unsigned> LoadedRegs;
189 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
191 DOUT << MBBI->getBasicBlock()->getName() << ":\n";
192 MachineBasicBlock &MBB = *MBBI;
193 for (MachineBasicBlock::iterator MII = MBB.begin(),
194 E = MBB.end(); MII != E; ++MII) {
195 MachineInstr &MI = *MII;
196 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
197 MachineOperand &MO = MI.getOperand(i);
198 if (MO.isRegister() && MO.getReg())
199 if (MRegisterInfo::isVirtualRegister(MO.getReg())) {
200 unsigned VirtReg = MO.getReg();
201 unsigned PhysReg = VRM.getPhys(VirtReg);
202 if (!VRM.isAssignedReg(VirtReg)) {
203 int StackSlot = VRM.getStackSlot(VirtReg);
204 const TargetRegisterClass* RC =
205 MF.getSSARegMap()->getRegClass(VirtReg);
208 std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
209 == LoadedRegs.end()) {
210 MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
211 LoadedRegs.push_back(VirtReg);
213 DOUT << '\t' << *prior(MII);
217 MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
221 MF.setPhysRegUsed(PhysReg);
222 MI.getOperand(i).setReg(PhysReg);
224 MF.setPhysRegUsed(MO.getReg());
235 //===----------------------------------------------------------------------===//
236 // Local Spiller Implementation
237 //===----------------------------------------------------------------------===//
240 /// LocalSpiller - This spiller does a simple pass over the machine basic
241 /// block to attempt to keep spills in registers as much as possible for
242 /// blocks that have low register pressure (the vreg may be spilled due to
243 /// register pressure in other blocks).
244 class VISIBILITY_HIDDEN LocalSpiller : public Spiller {
245 const MRegisterInfo *MRI;
246 const TargetInstrInfo *TII;
248 bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
249 MRI = MF.getTarget().getRegisterInfo();
250 TII = MF.getTarget().getInstrInfo();
251 DOUT << "\n**** Local spiller rewriting function '"
252 << MF.getFunction()->getName() << "':\n";
253 DOUT << "**** Machine Instrs (NOTE! Does not include spills and reloads!) ****\n";
256 for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
258 RewriteMBB(*MBB, VRM);
260 DOUT << "**** Post Machine Instrs ****\n";
266 void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
270 /// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
271 /// top down, keep track of which spills slots or remat are available in each
274 /// Note that not all physregs are created equal here. In particular, some
275 /// physregs are reloads that we are allowed to clobber or ignore at any time.
276 /// Other physregs are values that the register allocated program is using that
277 /// we cannot CHANGE, but we can read if we like. We keep track of this on a
278 /// per-stack-slot / remat id basis as the low bit in the value of the
279 /// SpillSlotsAvailable entries. The predicate 'canClobberPhysReg()' checks
280 /// this bit and addAvailable sets it if.
282 class VISIBILITY_HIDDEN AvailableSpills {
283 const MRegisterInfo *MRI;
284 const TargetInstrInfo *TII;
286 // SpillSlotsOrReMatsAvailable - This map keeps track of all of the spilled
287 // or remat'ed virtual register values that are still available, due to being
288 // loaded or stored to, but not invalidated yet.
289 std::map<int, unsigned> SpillSlotsOrReMatsAvailable;
291 // PhysRegsAvailable - This is the inverse of SpillSlotsOrReMatsAvailable,
292 // indicating which stack slot values are currently held by a physreg. This
293 // is used to invalidate entries in SpillSlotsOrReMatsAvailable when a
294 // physreg is modified.
295 std::multimap<unsigned, int> PhysRegsAvailable;
297 void disallowClobberPhysRegOnly(unsigned PhysReg);
299 void ClobberPhysRegOnly(unsigned PhysReg);
301 AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
302 : MRI(mri), TII(tii) {
305 const MRegisterInfo *getRegInfo() const { return MRI; }
307 /// getSpillSlotOrReMatPhysReg - If the specified stack slot or remat is
308 /// available in a physical register, return that PhysReg, otherwise
310 unsigned getSpillSlotOrReMatPhysReg(int Slot) const {
311 std::map<int, unsigned>::const_iterator I =
312 SpillSlotsOrReMatsAvailable.find(Slot);
313 if (I != SpillSlotsOrReMatsAvailable.end()) {
314 return I->second >> 1; // Remove the CanClobber bit.
319 /// addAvailable - Mark that the specified stack slot / remat is available in
320 /// the specified physreg. If CanClobber is true, the physreg can be modified
321 /// at any time without changing the semantics of the program.
322 void addAvailable(int SlotOrReMat, MachineInstr *MI, unsigned Reg,
323 bool CanClobber = true) {
324 // If this stack slot is thought to be available in some other physreg,
325 // remove its record.
326 ModifyStackSlotOrReMat(SlotOrReMat);
328 PhysRegsAvailable.insert(std::make_pair(Reg, SlotOrReMat));
329 SpillSlotsOrReMatsAvailable[SlotOrReMat]= (Reg << 1) | (unsigned)CanClobber;
331 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
332 DOUT << "Remembering RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1;
334 DOUT << "Remembering SS#" << SlotOrReMat;
335 DOUT << " in physreg " << MRI->getName(Reg) << "\n";
338 /// canClobberPhysReg - Return true if the spiller is allowed to change the
339 /// value of the specified stackslot register if it desires. The specified
340 /// stack slot must be available in a physreg for this query to make sense.
341 bool canClobberPhysReg(int SlotOrReMat) const {
342 assert(SpillSlotsOrReMatsAvailable.count(SlotOrReMat) &&
343 "Value not available!");
344 return SpillSlotsOrReMatsAvailable.find(SlotOrReMat)->second & 1;
347 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
348 /// stackslot register. The register is still available but is no longer
349 /// allowed to be modifed.
350 void disallowClobberPhysReg(unsigned PhysReg);
352 /// ClobberPhysReg - This is called when the specified physreg changes
353 /// value. We use this to invalidate any info about stuff we thing lives in
354 /// it and any of its aliases.
355 void ClobberPhysReg(unsigned PhysReg);
357 /// ModifyStackSlotOrReMat - This method is called when the value in a stack
358 /// slot changes. This removes information about which register the previous
359 /// value for this slot lives in (as the previous value is dead now).
360 void ModifyStackSlotOrReMat(int SlotOrReMat);
364 /// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
365 /// stackslot register. The register is still available but is no longer
366 /// allowed to be modifed.
367 void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
368 std::multimap<unsigned, int>::iterator I =
369 PhysRegsAvailable.lower_bound(PhysReg);
370 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
371 int SlotOrReMat = I->second;
373 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
374 "Bidirectional map mismatch!");
375 SpillSlotsOrReMatsAvailable[SlotOrReMat] &= ~1;
376 DOUT << "PhysReg " << MRI->getName(PhysReg)
377 << " copied, it is available for use but can no longer be modified\n";
381 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
382 /// stackslot register and its aliases. The register and its aliases may
383 /// still available but is no longer allowed to be modifed.
384 void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
385 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
386 disallowClobberPhysRegOnly(*AS);
387 disallowClobberPhysRegOnly(PhysReg);
390 /// ClobberPhysRegOnly - This is called when the specified physreg changes
391 /// value. We use this to invalidate any info about stuff we thing lives in it.
392 void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
393 std::multimap<unsigned, int>::iterator I =
394 PhysRegsAvailable.lower_bound(PhysReg);
395 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
396 int SlotOrReMat = I->second;
397 PhysRegsAvailable.erase(I++);
398 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
399 "Bidirectional map mismatch!");
400 SpillSlotsOrReMatsAvailable.erase(SlotOrReMat);
401 DOUT << "PhysReg " << MRI->getName(PhysReg)
402 << " clobbered, invalidating ";
403 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
404 DOUT << "RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1 << "\n";
406 DOUT << "SS#" << SlotOrReMat << "\n";
410 /// ClobberPhysReg - This is called when the specified physreg changes
411 /// value. We use this to invalidate any info about stuff we thing lives in
412 /// it and any of its aliases.
413 void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
414 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
415 ClobberPhysRegOnly(*AS);
416 ClobberPhysRegOnly(PhysReg);
419 /// ModifyStackSlotOrReMat - This method is called when the value in a stack
420 /// slot changes. This removes information about which register the previous
421 /// value for this slot lives in (as the previous value is dead now).
422 void AvailableSpills::ModifyStackSlotOrReMat(int SlotOrReMat) {
423 std::map<int, unsigned>::iterator It =
424 SpillSlotsOrReMatsAvailable.find(SlotOrReMat);
425 if (It == SpillSlotsOrReMatsAvailable.end()) return;
426 unsigned Reg = It->second >> 1;
427 SpillSlotsOrReMatsAvailable.erase(It);
429 // This register may hold the value of multiple stack slots, only remove this
430 // stack slot from the set of values the register contains.
431 std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
433 assert(I != PhysRegsAvailable.end() && I->first == Reg &&
434 "Map inverse broken!");
435 if (I->second == SlotOrReMat) break;
437 PhysRegsAvailable.erase(I);
442 /// InvalidateKills - MI is going to be deleted. If any of its operands are
443 /// marked kill, then invalidate the information.
444 static void InvalidateKills(MachineInstr &MI, BitVector &RegKills,
445 std::vector<MachineOperand*> &KillOps,
446 SmallVector<unsigned, 1> *KillRegs = NULL) {
447 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
448 MachineOperand &MO = MI.getOperand(i);
449 if (!MO.isRegister() || !MO.isUse() || !MO.isKill())
451 unsigned Reg = MO.getReg();
453 KillRegs->push_back(Reg);
454 if (KillOps[Reg] == &MO) {
461 /// InvalidateRegDef - If the def operand of the specified def MI is now dead
462 /// (since it's spill instruction is removed), mark it isDead. Also checks if
463 /// the def MI has other definition operands that are not dead. Returns it by
465 static bool InvalidateRegDef(MachineBasicBlock::iterator I,
466 MachineInstr &NewDef, unsigned Reg,
468 // Due to remat, it's possible this reg isn't being reused. That is,
469 // the def of this reg (by prev MI) is now dead.
470 MachineInstr *DefMI = I;
471 MachineOperand *DefOp = NULL;
472 for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) {
473 MachineOperand &MO = DefMI->getOperand(i);
474 if (MO.isRegister() && MO.isDef()) {
475 if (MO.getReg() == Reg)
477 else if (!MO.isDead())
484 bool FoundUse = false, Done = false;
485 MachineBasicBlock::iterator E = NewDef;
487 for (; !Done && I != E; ++I) {
488 MachineInstr *NMI = I;
489 for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) {
490 MachineOperand &MO = NMI->getOperand(j);
491 if (!MO.isRegister() || MO.getReg() != Reg)
495 Done = true; // Stop after scanning all the operands of this MI.
506 /// UpdateKills - Track and update kill info. If a MI reads a register that is
507 /// marked kill, then it must be due to register reuse. Transfer the kill info
509 static void UpdateKills(MachineInstr &MI, BitVector &RegKills,
510 std::vector<MachineOperand*> &KillOps) {
511 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
512 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
513 MachineOperand &MO = MI.getOperand(i);
514 if (!MO.isRegister() || !MO.isUse())
516 unsigned Reg = MO.getReg();
521 // That can't be right. Register is killed but not re-defined and it's
522 // being reused. Let's fix that.
523 KillOps[Reg]->unsetIsKill();
524 if (i < TID->numOperands &&
525 TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
526 // Unless it's a two-address operand, this is the new kill.
536 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
537 const MachineOperand &MO = MI.getOperand(i);
538 if (!MO.isRegister() || !MO.isDef())
540 unsigned Reg = MO.getReg();
547 // ReusedOp - For each reused operand, we keep track of a bit of information, in
548 // case we need to rollback upon processing a new operand. See comments below.
551 // The MachineInstr operand that reused an available value.
554 // StackSlotOrReMat - The spill slot or remat id of the value being reused.
555 unsigned StackSlotOrReMat;
557 // PhysRegReused - The physical register the value was available in.
558 unsigned PhysRegReused;
560 // AssignedPhysReg - The physreg that was assigned for use by the reload.
561 unsigned AssignedPhysReg;
563 // VirtReg - The virtual register itself.
566 ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
568 : Operand(o), StackSlotOrReMat(ss), PhysRegReused(prr),
569 AssignedPhysReg(apr), VirtReg(vreg) {}
572 /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
573 /// is reused instead of reloaded.
574 class VISIBILITY_HIDDEN ReuseInfo {
576 std::vector<ReusedOp> Reuses;
577 BitVector PhysRegsClobbered;
579 ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
580 PhysRegsClobbered.resize(mri->getNumRegs());
583 bool hasReuses() const {
584 return !Reuses.empty();
587 /// addReuse - If we choose to reuse a virtual register that is already
588 /// available instead of reloading it, remember that we did so.
589 void addReuse(unsigned OpNo, unsigned StackSlotOrReMat,
590 unsigned PhysRegReused, unsigned AssignedPhysReg,
592 // If the reload is to the assigned register anyway, no undo will be
594 if (PhysRegReused == AssignedPhysReg) return;
596 // Otherwise, remember this.
597 Reuses.push_back(ReusedOp(OpNo, StackSlotOrReMat, PhysRegReused,
598 AssignedPhysReg, VirtReg));
601 void markClobbered(unsigned PhysReg) {
602 PhysRegsClobbered.set(PhysReg);
605 bool isClobbered(unsigned PhysReg) const {
606 return PhysRegsClobbered.test(PhysReg);
609 /// GetRegForReload - We are about to emit a reload into PhysReg. If there
610 /// is some other operand that is using the specified register, either pick
611 /// a new register to use, or evict the previous reload and use this reg.
612 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
613 AvailableSpills &Spills,
614 std::vector<MachineInstr*> &MaybeDeadStores,
615 SmallSet<unsigned, 8> &Rejected,
617 std::vector<MachineOperand*> &KillOps,
619 if (Reuses.empty()) return PhysReg; // This is most often empty.
621 for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
622 ReusedOp &Op = Reuses[ro];
623 // If we find some other reuse that was supposed to use this register
624 // exactly for its reload, we can change this reload to use ITS reload
625 // register. That is, unless its reload register has already been
626 // considered and subsequently rejected because it has also been reused
627 // by another operand.
628 if (Op.PhysRegReused == PhysReg &&
629 Rejected.count(Op.AssignedPhysReg) == 0) {
630 // Yup, use the reload register that we didn't use before.
631 unsigned NewReg = Op.AssignedPhysReg;
632 Rejected.insert(PhysReg);
633 return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected,
634 RegKills, KillOps, VRM);
636 // Otherwise, we might also have a problem if a previously reused
637 // value aliases the new register. If so, codegen the previous reload
639 unsigned PRRU = Op.PhysRegReused;
640 const MRegisterInfo *MRI = Spills.getRegInfo();
641 if (MRI->areAliases(PRRU, PhysReg)) {
642 // Okay, we found out that an alias of a reused register
643 // was used. This isn't good because it means we have
644 // to undo a previous reuse.
645 MachineBasicBlock *MBB = MI->getParent();
646 const TargetRegisterClass *AliasRC =
647 MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
649 // Copy Op out of the vector and remove it, we're going to insert an
650 // explicit load for it.
652 Reuses.erase(Reuses.begin()+ro);
654 // Ok, we're going to try to reload the assigned physreg into the
655 // slot that we were supposed to in the first place. However, that
656 // register could hold a reuse. Check to see if it conflicts or
657 // would prefer us to use a different register.
658 unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
659 MI, Spills, MaybeDeadStores,
660 Rejected, RegKills, KillOps, VRM);
662 if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) {
663 MRI->reMaterialize(*MBB, MI, NewPhysReg,
664 VRM.getReMaterializedMI(NewOp.VirtReg));
667 MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg,
668 NewOp.StackSlotOrReMat, AliasRC);
669 // Any stores to this stack slot are not dead anymore.
670 MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL;
673 Spills.ClobberPhysReg(NewPhysReg);
674 Spills.ClobberPhysReg(NewOp.PhysRegReused);
676 MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
678 Spills.addAvailable(NewOp.StackSlotOrReMat, MI, NewPhysReg);
679 MachineBasicBlock::iterator MII = MI;
681 UpdateKills(*MII, RegKills, KillOps);
682 DOUT << '\t' << *MII;
684 DOUT << "Reuse undone!\n";
687 // Finally, PhysReg is now available, go ahead and use it.
695 /// GetRegForReload - Helper for the above GetRegForReload(). Add a
696 /// 'Rejected' set to remember which registers have been considered and
697 /// rejected for the reload. This avoids infinite looping in case like
700 /// t2 <- assigned r0 for use by the reload but ended up reuse r1
701 /// t3 <- assigned r1 for use by the reload but ended up reuse r0
703 /// sees r1 is taken by t2, tries t2's reload register r0
704 /// sees r0 is taken by t3, tries t3's reload register r1
705 /// sees r1 is taken by t2, tries t2's reload register r0 ...
706 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
707 AvailableSpills &Spills,
708 std::vector<MachineInstr*> &MaybeDeadStores,
710 std::vector<MachineOperand*> &KillOps,
712 SmallSet<unsigned, 8> Rejected;
713 return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected,
714 RegKills, KillOps, VRM);
720 /// rewriteMBB - Keep track of which spills are available even after the
721 /// register allocator is done with them. If possible, avoid reloading vregs.
722 void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
723 DOUT << MBB.getBasicBlock()->getName() << ":\n";
725 MachineFunction &MF = *MBB.getParent();
727 // Spills - Keep track of which spilled values are available in physregs so
728 // that we can choose to reuse the physregs instead of emitting reloads.
729 AvailableSpills Spills(MRI, TII);
731 // MaybeDeadStores - When we need to write a value back into a stack slot,
732 // keep track of the inserted store. If the stack slot value is never read
733 // (because the value was used from some available register, for example), and
734 // subsequently stored to, the original store is dead. This map keeps track
735 // of inserted stores that are not used. If we see a subsequent store to the
736 // same stack slot, the original store is deleted.
737 std::vector<MachineInstr*> MaybeDeadStores;
738 MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL);
740 // ReMatDefs - These are rematerializable def MIs which are not deleted.
741 SmallSet<MachineInstr*, 4> ReMatDefs;
743 // Keep track of kill information.
744 BitVector RegKills(MRI->getNumRegs());
745 std::vector<MachineOperand*> KillOps;
746 KillOps.resize(MRI->getNumRegs(), NULL);
748 for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
750 MachineInstr &MI = *MII;
751 MachineBasicBlock::iterator NextMII = MII; ++NextMII;
752 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
755 bool BackTracked = false;
757 /// ReusedOperands - Keep track of operand reuse in case we need to undo
759 ReuseInfo ReusedOperands(MI, MRI);
761 // Loop over all of the implicit defs, clearing them from our available
763 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
764 if (TID->ImplicitDefs) {
765 const unsigned *ImpDef = TID->ImplicitDefs;
766 for ( ; *ImpDef; ++ImpDef) {
767 MF.setPhysRegUsed(*ImpDef);
768 ReusedOperands.markClobbered(*ImpDef);
769 Spills.ClobberPhysReg(*ImpDef);
773 // Process all of the spilled uses and all non spilled reg references.
774 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
775 MachineOperand &MO = MI.getOperand(i);
776 if (!MO.isRegister() || MO.getReg() == 0)
777 continue; // Ignore non-register operands.
779 if (MRegisterInfo::isPhysicalRegister(MO.getReg())) {
780 // Ignore physregs for spilling, but remember that it is used by this
782 MF.setPhysRegUsed(MO.getReg());
783 ReusedOperands.markClobbered(MO.getReg());
787 assert(MRegisterInfo::isVirtualRegister(MO.getReg()) &&
788 "Not a virtual or a physical register?");
790 unsigned VirtReg = MO.getReg();
791 if (VRM.isAssignedReg(VirtReg)) {
792 // This virtual register was assigned a physreg!
793 unsigned Phys = VRM.getPhys(VirtReg);
794 MF.setPhysRegUsed(Phys);
796 ReusedOperands.markClobbered(Phys);
797 MI.getOperand(i).setReg(Phys);
801 // This virtual register is now known to be a spilled value.
803 continue; // Handle defs in the loop below (handle use&def here though)
805 bool DoReMat = VRM.isReMaterialized(VirtReg);
806 int SSorRMId = DoReMat
807 ? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
808 int ReuseSlot = SSorRMId;
810 // Check to see if this stack slot is available.
811 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
812 if (!PhysReg && DoReMat) {
813 // This use is rematerializable. But perhaps the value is available in
814 // stack if the definition is not deleted. If so, check if we can
816 ReuseSlot = VRM.getStackSlot(VirtReg);
817 if (ReuseSlot != VirtRegMap::NO_STACK_SLOT)
818 PhysReg = Spills.getSpillSlotOrReMatPhysReg(ReuseSlot);
821 // This spilled operand might be part of a two-address operand. If this
822 // is the case, then changing it will necessarily require changing the
823 // def part of the instruction as well. However, in some cases, we
824 // aren't allowed to modify the reused register. If none of these cases
826 bool CanReuse = true;
827 int ti = TID->getOperandConstraint(i, TOI::TIED_TO);
829 MI.getOperand(ti).isRegister() &&
830 MI.getOperand(ti).getReg() == VirtReg) {
831 // Okay, we have a two address operand. We can reuse this physreg as
832 // long as we are allowed to clobber the value and there isn't an
833 // earlier def that has already clobbered the physreg.
834 CanReuse = Spills.canClobberPhysReg(ReuseSlot) &&
835 !ReusedOperands.isClobbered(PhysReg);
839 // If this stack slot value is already available, reuse it!
840 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
841 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
843 DOUT << "Reusing SS#" << ReuseSlot;
844 DOUT << " from physreg "
845 << MRI->getName(PhysReg) << " for vreg"
846 << VirtReg <<" instead of reloading into physreg "
847 << MRI->getName(VRM.getPhys(VirtReg)) << "\n";
848 MI.getOperand(i).setReg(PhysReg);
850 // The only technical detail we have is that we don't know that
851 // PhysReg won't be clobbered by a reloaded stack slot that occurs
852 // later in the instruction. In particular, consider 'op V1, V2'.
853 // If V1 is available in physreg R0, we would choose to reuse it
854 // here, instead of reloading it into the register the allocator
855 // indicated (say R1). However, V2 might have to be reloaded
856 // later, and it might indicate that it needs to live in R0. When
857 // this occurs, we need to have information available that
858 // indicates it is safe to use R1 for the reload instead of R0.
860 // To further complicate matters, we might conflict with an alias,
861 // or R0 and R1 might not be compatible with each other. In this
862 // case, we actually insert a reload for V1 in R1, ensuring that
863 // we can get at R0 or its alias.
864 ReusedOperands.addReuse(i, ReuseSlot, PhysReg,
865 VRM.getPhys(VirtReg), VirtReg);
867 // Only mark it clobbered if this is a use&def operand.
868 ReusedOperands.markClobbered(PhysReg);
871 if (MI.getOperand(i).isKill() &&
872 ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) {
873 // This was the last use and the spilled value is still available
874 // for reuse. That means the spill was unnecessary!
875 MachineInstr* DeadStore = MaybeDeadStores[ReuseSlot];
877 DOUT << "Removed dead store:\t" << *DeadStore;
878 InvalidateKills(*DeadStore, RegKills, KillOps);
879 MBB.erase(DeadStore);
880 VRM.RemoveFromFoldedVirtMap(DeadStore);
881 MaybeDeadStores[ReuseSlot] = NULL;
888 // Otherwise we have a situation where we have a two-address instruction
889 // whose mod/ref operand needs to be reloaded. This reload is already
890 // available in some register "PhysReg", but if we used PhysReg as the
891 // operand to our 2-addr instruction, the instruction would modify
892 // PhysReg. This isn't cool if something later uses PhysReg and expects
893 // to get its initial value.
895 // To avoid this problem, and to avoid doing a load right after a store,
896 // we emit a copy from PhysReg into the designated register for this
898 unsigned DesignatedReg = VRM.getPhys(VirtReg);
899 assert(DesignatedReg && "Must map virtreg to physreg!");
901 // Note that, if we reused a register for a previous operand, the
902 // register we want to reload into might not actually be
903 // available. If this occurs, use the register indicated by the
905 if (ReusedOperands.hasReuses())
906 DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
907 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
909 // If the mapped designated register is actually the physreg we have
910 // incoming, we don't need to inserted a dead copy.
911 if (DesignatedReg == PhysReg) {
912 // If this stack slot value is already available, reuse it!
913 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
914 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
916 DOUT << "Reusing SS#" << ReuseSlot;
917 DOUT << " from physreg " << MRI->getName(PhysReg) << " for vreg"
919 << " instead of reloading into same physreg.\n";
920 MI.getOperand(i).setReg(PhysReg);
921 ReusedOperands.markClobbered(PhysReg);
926 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(VirtReg);
927 MF.setPhysRegUsed(DesignatedReg);
928 ReusedOperands.markClobbered(DesignatedReg);
929 MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC, RC);
931 MachineInstr *CopyMI = prior(MII);
932 UpdateKills(*CopyMI, RegKills, KillOps);
934 // This invalidates DesignatedReg.
935 Spills.ClobberPhysReg(DesignatedReg);
937 Spills.addAvailable(ReuseSlot, &MI, DesignatedReg);
938 MI.getOperand(i).setReg(DesignatedReg);
939 DOUT << '\t' << *prior(MII);
944 // Otherwise, reload it and remember that we have it.
945 PhysReg = VRM.getPhys(VirtReg);
946 assert(PhysReg && "Must map virtreg to physreg!");
947 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(VirtReg);
949 // Note that, if we reused a register for a previous operand, the
950 // register we want to reload into might not actually be
951 // available. If this occurs, use the register indicated by the
953 if (ReusedOperands.hasReuses())
954 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
955 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
957 MF.setPhysRegUsed(PhysReg);
958 ReusedOperands.markClobbered(PhysReg);
960 MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg));
963 MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, SSorRMId, RC);
966 // This invalidates PhysReg.
967 Spills.ClobberPhysReg(PhysReg);
969 // Any stores to this stack slot are not dead anymore.
971 MaybeDeadStores[SSorRMId] = NULL;
972 Spills.addAvailable(SSorRMId, &MI, PhysReg);
973 // Assumes this is the last use. IsKill will be unset if reg is reused
974 // unless it's a two-address operand.
975 if (TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
976 MI.getOperand(i).setIsKill();
977 MI.getOperand(i).setReg(PhysReg);
978 UpdateKills(*prior(MII), RegKills, KillOps);
979 DOUT << '\t' << *prior(MII);
984 // If we have folded references to memory operands, make sure we clear all
985 // physical registers that may contain the value of the spilled virtual
987 SmallSet<int, 1> FoldedSS;
988 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
989 DOUT << "Folded vreg: " << I->second.first << " MR: "
991 unsigned VirtReg = I->second.first;
992 VirtRegMap::ModRef MR = I->second.second;
993 if (VRM.isAssignedReg(VirtReg)) {
994 DOUT << ": No stack slot!\n";
997 int SS = VRM.getStackSlot(VirtReg);
999 DOUT << " - StackSlot: " << SS << "\n";
1001 // If this folded instruction is just a use, check to see if it's a
1002 // straight load from the virt reg slot.
1003 if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
1005 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
1006 if (FrameIdx == SS) {
1007 // If this spill slot is available, turn it into a copy (or nothing)
1008 // instead of leaving it as a load!
1009 if (unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SS)) {
1010 DOUT << "Promoted Load To Copy: " << MI;
1011 if (DestReg != InReg) {
1012 const TargetRegisterClass *RC =
1013 MF.getSSARegMap()->getRegClass(VirtReg);
1014 MRI->copyRegToReg(MBB, &MI, DestReg, InReg, RC, RC);
1015 // Revisit the copy so we make sure to notice the effects of the
1016 // operation on the destreg (either needing to RA it if it's
1017 // virtual or needing to clobber any values if it's physical).
1019 --NextMII; // backtrack to the copy.
1022 DOUT << "Removing now-noop copy: " << MI;
1024 VRM.RemoveFromFoldedVirtMap(&MI);
1027 goto ProcessNextInst;
1033 // If this reference is not a use, any previous store is now dead.
1034 // Otherwise, the store to this stack slot is not dead anymore.
1035 MachineInstr* DeadStore = MaybeDeadStores[SS];
1037 if (!(MR & VirtRegMap::isRef)) { // Previous store is dead.
1038 // If we get here, the store is dead, nuke it now.
1039 assert(VirtRegMap::isMod && "Can't be modref!");
1040 DOUT << "Removed dead store:\t" << *DeadStore;
1041 InvalidateKills(*DeadStore, RegKills, KillOps);
1042 MBB.erase(DeadStore);
1043 VRM.RemoveFromFoldedVirtMap(DeadStore);
1046 MaybeDeadStores[SS] = NULL;
1049 // If the spill slot value is available, and this is a new definition of
1050 // the value, the value is not available anymore.
1051 if (MR & VirtRegMap::isMod) {
1052 // Notice that the value in this stack slot has been modified.
1053 Spills.ModifyStackSlotOrReMat(SS);
1055 // If this is *just* a mod of the value, check to see if this is just a
1056 // store to the spill slot (i.e. the spill got merged into the copy). If
1057 // so, realize that the vreg is available now, and add the store to the
1058 // MaybeDeadStore info.
1060 if (!(MR & VirtRegMap::isRef)) {
1061 if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
1062 assert(MRegisterInfo::isPhysicalRegister(SrcReg) &&
1063 "Src hasn't been allocated yet?");
1064 // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
1065 // this as a potentially dead store in case there is a subsequent
1066 // store into the stack slot without a read from it.
1067 MaybeDeadStores[StackSlot] = &MI;
1069 // If the stack slot value was previously available in some other
1070 // register, change it now. Otherwise, make the register available,
1072 Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/);
1078 // Process all of the spilled defs.
1079 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
1080 MachineOperand &MO = MI.getOperand(i);
1081 if (MO.isRegister() && MO.getReg() && MO.isDef()) {
1082 unsigned VirtReg = MO.getReg();
1084 if (!MRegisterInfo::isVirtualRegister(VirtReg)) {
1085 // Check to see if this is a noop copy. If so, eliminate the
1086 // instruction before considering the dest reg to be changed.
1088 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1090 DOUT << "Removing now-noop copy: " << MI;
1093 VRM.RemoveFromFoldedVirtMap(&MI);
1094 Spills.disallowClobberPhysReg(VirtReg);
1095 goto ProcessNextInst;
1098 // If it's not a no-op copy, it clobbers the value in the destreg.
1099 Spills.ClobberPhysReg(VirtReg);
1100 ReusedOperands.markClobbered(VirtReg);
1102 // Check to see if this instruction is a load from a stack slot into
1103 // a register. If so, this provides the stack slot value in the reg.
1105 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
1106 assert(DestReg == VirtReg && "Unknown load situation!");
1108 // If it is a folded reference, then it's not safe to clobber.
1109 bool Folded = FoldedSS.count(FrameIdx);
1110 // Otherwise, if it wasn't available, remember that it is now!
1111 Spills.addAvailable(FrameIdx, &MI, DestReg, !Folded);
1112 goto ProcessNextInst;
1118 bool DoReMat = VRM.isReMaterialized(VirtReg);
1120 ReMatDefs.insert(&MI);
1122 // The only vregs left are stack slot definitions.
1123 int StackSlot = VRM.getStackSlot(VirtReg);
1124 const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(VirtReg);
1126 // If this def is part of a two-address operand, make sure to execute
1127 // the store from the correct physical register.
1129 int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i);
1131 PhysReg = MI.getOperand(TiedOp).getReg();
1133 PhysReg = VRM.getPhys(VirtReg);
1134 if (ReusedOperands.isClobbered(PhysReg)) {
1135 // Another def has taken the assigned physreg. It must have been a
1136 // use&def which got it due to reuse. Undo the reuse!
1137 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
1138 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
1142 MF.setPhysRegUsed(PhysReg);
1143 ReusedOperands.markClobbered(PhysReg);
1144 MI.getOperand(i).setReg(PhysReg);
1146 MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
1147 DOUT << "Store:\t" << *next(MII);
1149 // If there is a dead store to this stack slot, nuke it now.
1150 MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
1152 DOUT << "Removed dead store:\t" << *LastStore;
1154 SmallVector<unsigned, 1> KillRegs;
1155 InvalidateKills(*LastStore, RegKills, KillOps, &KillRegs);
1156 MachineBasicBlock::iterator PrevMII = LastStore;
1157 bool CheckDef = PrevMII != MBB.begin();
1160 MBB.erase(LastStore);
1161 VRM.RemoveFromFoldedVirtMap(LastStore);
1163 // Look at defs of killed registers on the store. Mark the defs
1164 // as dead since the store has been deleted and they aren't
1166 for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
1167 bool HasOtherDef = false;
1168 if (InvalidateRegDef(PrevMII, MI, KillRegs[j], HasOtherDef)) {
1169 MachineInstr *DeadDef = PrevMII;
1170 if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
1171 // FIXME: This assumes a remat def does not have side
1174 VRM.RemoveFromFoldedVirtMap(DeadDef);
1181 LastStore = next(MII);
1183 // If the stack slot value was previously available in some other
1184 // register, change it now. Otherwise, make the register available,
1186 Spills.ModifyStackSlotOrReMat(StackSlot);
1187 Spills.ClobberPhysReg(PhysReg);
1188 Spills.addAvailable(StackSlot, LastStore, PhysReg);
1191 // Check to see if this is a noop copy. If so, eliminate the
1192 // instruction before considering the dest reg to be changed.
1195 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1197 DOUT << "Removing now-noop copy: " << MI;
1200 VRM.RemoveFromFoldedVirtMap(&MI);
1201 UpdateKills(*LastStore, RegKills, KillOps);
1202 goto ProcessNextInst;
1209 if (!Erased && !BackTracked)
1210 for (MachineBasicBlock::iterator II = MI; II != NextMII; ++II)
1211 UpdateKills(*II, RegKills, KillOps);
1217 llvm::Spiller* llvm::createSpiller() {
1218 switch (SpillerOpt) {
1219 default: assert(0 && "Unreachable!");
1221 return new LocalSpiller();
1223 return new SimpleSpiller();