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), Virt2SplitMap(0),
67 ReMatMap(NULL), 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 Virt2SplitMap.grow(LastVirtReg);
77 ReMatMap.grow(LastVirtReg);
80 int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
81 assert(MRegisterInfo::isVirtualRegister(virtReg));
82 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
83 "attempt to assign stack slot to already spilled register");
84 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(virtReg);
85 int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
87 Virt2StackSlotMap[virtReg] = frameIndex;
92 void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) {
93 assert(MRegisterInfo::isVirtualRegister(virtReg));
94 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
95 "attempt to assign stack slot to already spilled register");
96 assert((frameIndex >= 0 ||
97 (frameIndex >= MF.getFrameInfo()->getObjectIndexBegin())) &&
98 "illegal fixed frame index");
99 Virt2StackSlotMap[virtReg] = frameIndex;
102 int VirtRegMap::assignVirtReMatId(unsigned virtReg) {
103 assert(MRegisterInfo::isVirtualRegister(virtReg));
104 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
105 "attempt to assign re-mat id to already spilled register");
106 Virt2ReMatIdMap[virtReg] = ReMatId;
110 void VirtRegMap::assignVirtReMatId(unsigned virtReg, int id) {
111 assert(MRegisterInfo::isVirtualRegister(virtReg));
112 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
113 "attempt to assign re-mat id to already spilled register");
114 Virt2ReMatIdMap[virtReg] = id;
117 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
118 MachineInstr *NewMI, ModRef MRInfo) {
119 // Move previous memory references folded to new instruction.
120 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
121 for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
122 E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
123 MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
124 MI2VirtMap.erase(I++);
127 // add new memory reference
128 MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
131 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *MI, ModRef MRInfo) {
132 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(MI);
133 MI2VirtMap.insert(IP, std::make_pair(MI, std::make_pair(VirtReg, MRInfo)));
136 void VirtRegMap::print(std::ostream &OS) const {
137 const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
139 OS << "********** REGISTER MAP **********\n";
140 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
141 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) {
142 if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG)
143 OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n";
147 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
148 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i)
149 if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT)
150 OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n";
154 void VirtRegMap::dump() const {
159 //===----------------------------------------------------------------------===//
160 // Simple Spiller Implementation
161 //===----------------------------------------------------------------------===//
163 Spiller::~Spiller() {}
166 struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller {
167 bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM);
171 bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
172 DOUT << "********** REWRITE MACHINE CODE **********\n";
173 DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
174 const TargetMachine &TM = MF.getTarget();
175 const MRegisterInfo &MRI = *TM.getRegisterInfo();
177 // LoadedRegs - Keep track of which vregs are loaded, so that we only load
178 // each vreg once (in the case where a spilled vreg is used by multiple
179 // operands). This is always smaller than the number of operands to the
180 // current machine instr, so it should be small.
181 std::vector<unsigned> LoadedRegs;
183 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
185 DOUT << MBBI->getBasicBlock()->getName() << ":\n";
186 MachineBasicBlock &MBB = *MBBI;
187 for (MachineBasicBlock::iterator MII = MBB.begin(),
188 E = MBB.end(); MII != E; ++MII) {
189 MachineInstr &MI = *MII;
190 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
191 MachineOperand &MO = MI.getOperand(i);
192 if (MO.isRegister() && MO.getReg())
193 if (MRegisterInfo::isVirtualRegister(MO.getReg())) {
194 unsigned VirtReg = MO.getReg();
195 unsigned PhysReg = VRM.getPhys(VirtReg);
196 if (!VRM.isAssignedReg(VirtReg)) {
197 int StackSlot = VRM.getStackSlot(VirtReg);
198 const TargetRegisterClass* RC =
199 MF.getSSARegMap()->getRegClass(VirtReg);
202 std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
203 == LoadedRegs.end()) {
204 MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
205 LoadedRegs.push_back(VirtReg);
207 DOUT << '\t' << *prior(MII);
211 MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
215 MF.setPhysRegUsed(PhysReg);
216 MI.getOperand(i).setReg(PhysReg);
218 MF.setPhysRegUsed(MO.getReg());
229 //===----------------------------------------------------------------------===//
230 // Local Spiller Implementation
231 //===----------------------------------------------------------------------===//
234 class AvailableSpills;
236 /// LocalSpiller - This spiller does a simple pass over the machine basic
237 /// block to attempt to keep spills in registers as much as possible for
238 /// blocks that have low register pressure (the vreg may be spilled due to
239 /// register pressure in other blocks).
240 class VISIBILITY_HIDDEN LocalSpiller : public Spiller {
242 const MRegisterInfo *MRI;
243 const TargetInstrInfo *TII;
245 bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
246 RegMap = MF.getSSARegMap();
247 MRI = MF.getTarget().getRegisterInfo();
248 TII = MF.getTarget().getInstrInfo();
249 DOUT << "\n**** Local spiller rewriting function '"
250 << MF.getFunction()->getName() << "':\n";
251 DOUT << "**** Machine Instrs (NOTE! Does not include spills and reloads!) ****\n";
254 for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
256 RewriteMBB(*MBB, VRM);
258 DOUT << "**** Post Machine Instrs ****\n";
264 bool PrepForUnfoldOpti(MachineBasicBlock &MBB,
265 MachineBasicBlock::iterator &MII,
266 std::vector<MachineInstr*> &MaybeDeadStores,
267 AvailableSpills &Spills, BitVector &RegKills,
268 std::vector<MachineOperand*> &KillOps,
270 void SpillRegToStackSlot(MachineBasicBlock &MBB,
271 MachineBasicBlock::iterator &MII,
272 int Idx, unsigned PhysReg, int StackSlot,
273 const TargetRegisterClass *RC,
274 bool isAvailable, MachineInstr *&LastStore,
275 AvailableSpills &Spills,
276 SmallSet<MachineInstr*, 4> &ReMatDefs,
278 std::vector<MachineOperand*> &KillOps,
280 void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
284 /// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
285 /// top down, keep track of which spills slots or remat are available in each
288 /// Note that not all physregs are created equal here. In particular, some
289 /// physregs are reloads that we are allowed to clobber or ignore at any time.
290 /// Other physregs are values that the register allocated program is using that
291 /// we cannot CHANGE, but we can read if we like. We keep track of this on a
292 /// per-stack-slot / remat id basis as the low bit in the value of the
293 /// SpillSlotsAvailable entries. The predicate 'canClobberPhysReg()' checks
294 /// this bit and addAvailable sets it if.
296 class VISIBILITY_HIDDEN AvailableSpills {
297 const MRegisterInfo *MRI;
298 const TargetInstrInfo *TII;
300 // SpillSlotsOrReMatsAvailable - This map keeps track of all of the spilled
301 // or remat'ed virtual register values that are still available, due to being
302 // loaded or stored to, but not invalidated yet.
303 std::map<int, unsigned> SpillSlotsOrReMatsAvailable;
305 // PhysRegsAvailable - This is the inverse of SpillSlotsOrReMatsAvailable,
306 // indicating which stack slot values are currently held by a physreg. This
307 // is used to invalidate entries in SpillSlotsOrReMatsAvailable when a
308 // physreg is modified.
309 std::multimap<unsigned, int> PhysRegsAvailable;
311 void disallowClobberPhysRegOnly(unsigned PhysReg);
313 void ClobberPhysRegOnly(unsigned PhysReg);
315 AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
316 : MRI(mri), TII(tii) {
319 const MRegisterInfo *getRegInfo() const { return MRI; }
321 /// getSpillSlotOrReMatPhysReg - If the specified stack slot or remat is
322 /// available in a physical register, return that PhysReg, otherwise
324 unsigned getSpillSlotOrReMatPhysReg(int Slot) const {
325 std::map<int, unsigned>::const_iterator I =
326 SpillSlotsOrReMatsAvailable.find(Slot);
327 if (I != SpillSlotsOrReMatsAvailable.end()) {
328 return I->second >> 1; // Remove the CanClobber bit.
333 /// addAvailable - Mark that the specified stack slot / remat is available in
334 /// the specified physreg. If CanClobber is true, the physreg can be modified
335 /// at any time without changing the semantics of the program.
336 void addAvailable(int SlotOrReMat, MachineInstr *MI, unsigned Reg,
337 bool CanClobber = true) {
338 // If this stack slot is thought to be available in some other physreg,
339 // remove its record.
340 ModifyStackSlotOrReMat(SlotOrReMat);
342 PhysRegsAvailable.insert(std::make_pair(Reg, SlotOrReMat));
343 SpillSlotsOrReMatsAvailable[SlotOrReMat]= (Reg << 1) | (unsigned)CanClobber;
345 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
346 DOUT << "Remembering RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1;
348 DOUT << "Remembering SS#" << SlotOrReMat;
349 DOUT << " in physreg " << MRI->getName(Reg) << "\n";
352 /// canClobberPhysReg - Return true if the spiller is allowed to change the
353 /// value of the specified stackslot register if it desires. The specified
354 /// stack slot must be available in a physreg for this query to make sense.
355 bool canClobberPhysReg(int SlotOrReMat) const {
356 assert(SpillSlotsOrReMatsAvailable.count(SlotOrReMat) &&
357 "Value not available!");
358 return SpillSlotsOrReMatsAvailable.find(SlotOrReMat)->second & 1;
361 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
362 /// stackslot register. The register is still available but is no longer
363 /// allowed to be modifed.
364 void disallowClobberPhysReg(unsigned PhysReg);
366 /// ClobberPhysReg - This is called when the specified physreg changes
367 /// value. We use this to invalidate any info about stuff that lives in
368 /// it and any of its aliases.
369 void ClobberPhysReg(unsigned PhysReg);
371 /// ModifyStackSlotOrReMat - This method is called when the value in a stack
372 /// slot changes. This removes information about which register the previous
373 /// value for this slot lives in (as the previous value is dead now).
374 void ModifyStackSlotOrReMat(int SlotOrReMat);
378 /// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
379 /// stackslot register. The register is still available but is no longer
380 /// allowed to be modifed.
381 void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
382 std::multimap<unsigned, int>::iterator I =
383 PhysRegsAvailable.lower_bound(PhysReg);
384 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
385 int SlotOrReMat = I->second;
387 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
388 "Bidirectional map mismatch!");
389 SpillSlotsOrReMatsAvailable[SlotOrReMat] &= ~1;
390 DOUT << "PhysReg " << MRI->getName(PhysReg)
391 << " copied, it is available for use but can no longer be modified\n";
395 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
396 /// stackslot register and its aliases. The register and its aliases may
397 /// still available but is no longer allowed to be modifed.
398 void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
399 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
400 disallowClobberPhysRegOnly(*AS);
401 disallowClobberPhysRegOnly(PhysReg);
404 /// ClobberPhysRegOnly - This is called when the specified physreg changes
405 /// value. We use this to invalidate any info about stuff we thing lives in it.
406 void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
407 std::multimap<unsigned, int>::iterator I =
408 PhysRegsAvailable.lower_bound(PhysReg);
409 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
410 int SlotOrReMat = I->second;
411 PhysRegsAvailable.erase(I++);
412 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
413 "Bidirectional map mismatch!");
414 SpillSlotsOrReMatsAvailable.erase(SlotOrReMat);
415 DOUT << "PhysReg " << MRI->getName(PhysReg)
416 << " clobbered, invalidating ";
417 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
418 DOUT << "RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1 << "\n";
420 DOUT << "SS#" << SlotOrReMat << "\n";
424 /// ClobberPhysReg - This is called when the specified physreg changes
425 /// value. We use this to invalidate any info about stuff we thing lives in
426 /// it and any of its aliases.
427 void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
428 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
429 ClobberPhysRegOnly(*AS);
430 ClobberPhysRegOnly(PhysReg);
433 /// ModifyStackSlotOrReMat - This method is called when the value in a stack
434 /// slot changes. This removes information about which register the previous
435 /// value for this slot lives in (as the previous value is dead now).
436 void AvailableSpills::ModifyStackSlotOrReMat(int SlotOrReMat) {
437 std::map<int, unsigned>::iterator It =
438 SpillSlotsOrReMatsAvailable.find(SlotOrReMat);
439 if (It == SpillSlotsOrReMatsAvailable.end()) return;
440 unsigned Reg = It->second >> 1;
441 SpillSlotsOrReMatsAvailable.erase(It);
443 // This register may hold the value of multiple stack slots, only remove this
444 // stack slot from the set of values the register contains.
445 std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
447 assert(I != PhysRegsAvailable.end() && I->first == Reg &&
448 "Map inverse broken!");
449 if (I->second == SlotOrReMat) break;
451 PhysRegsAvailable.erase(I);
456 /// InvalidateKills - MI is going to be deleted. If any of its operands are
457 /// marked kill, then invalidate the information.
458 static void InvalidateKills(MachineInstr &MI, BitVector &RegKills,
459 std::vector<MachineOperand*> &KillOps,
460 SmallVector<unsigned, 2> *KillRegs = NULL) {
461 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
462 MachineOperand &MO = MI.getOperand(i);
463 if (!MO.isRegister() || !MO.isUse() || !MO.isKill())
465 unsigned Reg = MO.getReg();
467 KillRegs->push_back(Reg);
468 if (KillOps[Reg] == &MO) {
475 /// InvalidateRegDef - If the def operand of the specified def MI is now dead
476 /// (since it's spill instruction is removed), mark it isDead. Also checks if
477 /// the def MI has other definition operands that are not dead. Returns it by
479 static bool InvalidateRegDef(MachineBasicBlock::iterator I,
480 MachineInstr &NewDef, unsigned Reg,
482 // Due to remat, it's possible this reg isn't being reused. That is,
483 // the def of this reg (by prev MI) is now dead.
484 MachineInstr *DefMI = I;
485 MachineOperand *DefOp = NULL;
486 for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) {
487 MachineOperand &MO = DefMI->getOperand(i);
488 if (MO.isRegister() && MO.isDef()) {
489 if (MO.getReg() == Reg)
491 else if (!MO.isDead())
498 bool FoundUse = false, Done = false;
499 MachineBasicBlock::iterator E = NewDef;
501 for (; !Done && I != E; ++I) {
502 MachineInstr *NMI = I;
503 for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) {
504 MachineOperand &MO = NMI->getOperand(j);
505 if (!MO.isRegister() || MO.getReg() != Reg)
509 Done = true; // Stop after scanning all the operands of this MI.
520 /// UpdateKills - Track and update kill info. If a MI reads a register that is
521 /// marked kill, then it must be due to register reuse. Transfer the kill info
523 static void UpdateKills(MachineInstr &MI, BitVector &RegKills,
524 std::vector<MachineOperand*> &KillOps) {
525 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
526 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
527 MachineOperand &MO = MI.getOperand(i);
528 if (!MO.isRegister() || !MO.isUse())
530 unsigned Reg = MO.getReg();
535 // That can't be right. Register is killed but not re-defined and it's
536 // being reused. Let's fix that.
537 KillOps[Reg]->unsetIsKill();
538 if (i < TID->numOperands &&
539 TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
540 // Unless it's a two-address operand, this is the new kill.
550 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
551 const MachineOperand &MO = MI.getOperand(i);
552 if (!MO.isRegister() || !MO.isDef())
554 unsigned Reg = MO.getReg();
561 // ReusedOp - For each reused operand, we keep track of a bit of information, in
562 // case we need to rollback upon processing a new operand. See comments below.
565 // The MachineInstr operand that reused an available value.
568 // StackSlotOrReMat - The spill slot or remat id of the value being reused.
569 unsigned StackSlotOrReMat;
571 // PhysRegReused - The physical register the value was available in.
572 unsigned PhysRegReused;
574 // AssignedPhysReg - The physreg that was assigned for use by the reload.
575 unsigned AssignedPhysReg;
577 // VirtReg - The virtual register itself.
580 ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
582 : Operand(o), StackSlotOrReMat(ss), PhysRegReused(prr),
583 AssignedPhysReg(apr), VirtReg(vreg) {}
586 /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
587 /// is reused instead of reloaded.
588 class VISIBILITY_HIDDEN ReuseInfo {
590 std::vector<ReusedOp> Reuses;
591 BitVector PhysRegsClobbered;
593 ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
594 PhysRegsClobbered.resize(mri->getNumRegs());
597 bool hasReuses() const {
598 return !Reuses.empty();
601 /// addReuse - If we choose to reuse a virtual register that is already
602 /// available instead of reloading it, remember that we did so.
603 void addReuse(unsigned OpNo, unsigned StackSlotOrReMat,
604 unsigned PhysRegReused, unsigned AssignedPhysReg,
606 // If the reload is to the assigned register anyway, no undo will be
608 if (PhysRegReused == AssignedPhysReg) return;
610 // Otherwise, remember this.
611 Reuses.push_back(ReusedOp(OpNo, StackSlotOrReMat, PhysRegReused,
612 AssignedPhysReg, VirtReg));
615 void markClobbered(unsigned PhysReg) {
616 PhysRegsClobbered.set(PhysReg);
619 bool isClobbered(unsigned PhysReg) const {
620 return PhysRegsClobbered.test(PhysReg);
623 /// GetRegForReload - We are about to emit a reload into PhysReg. If there
624 /// is some other operand that is using the specified register, either pick
625 /// a new register to use, or evict the previous reload and use this reg.
626 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
627 AvailableSpills &Spills,
628 std::vector<MachineInstr*> &MaybeDeadStores,
629 SmallSet<unsigned, 8> &Rejected,
631 std::vector<MachineOperand*> &KillOps,
633 if (Reuses.empty()) return PhysReg; // This is most often empty.
635 for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
636 ReusedOp &Op = Reuses[ro];
637 // If we find some other reuse that was supposed to use this register
638 // exactly for its reload, we can change this reload to use ITS reload
639 // register. That is, unless its reload register has already been
640 // considered and subsequently rejected because it has also been reused
641 // by another operand.
642 if (Op.PhysRegReused == PhysReg &&
643 Rejected.count(Op.AssignedPhysReg) == 0) {
644 // Yup, use the reload register that we didn't use before.
645 unsigned NewReg = Op.AssignedPhysReg;
646 Rejected.insert(PhysReg);
647 return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected,
648 RegKills, KillOps, VRM);
650 // Otherwise, we might also have a problem if a previously reused
651 // value aliases the new register. If so, codegen the previous reload
653 unsigned PRRU = Op.PhysRegReused;
654 const MRegisterInfo *MRI = Spills.getRegInfo();
655 if (MRI->areAliases(PRRU, PhysReg)) {
656 // Okay, we found out that an alias of a reused register
657 // was used. This isn't good because it means we have
658 // to undo a previous reuse.
659 MachineBasicBlock *MBB = MI->getParent();
660 const TargetRegisterClass *AliasRC =
661 MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
663 // Copy Op out of the vector and remove it, we're going to insert an
664 // explicit load for it.
666 Reuses.erase(Reuses.begin()+ro);
668 // Ok, we're going to try to reload the assigned physreg into the
669 // slot that we were supposed to in the first place. However, that
670 // register could hold a reuse. Check to see if it conflicts or
671 // would prefer us to use a different register.
672 unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
673 MI, Spills, MaybeDeadStores,
674 Rejected, RegKills, KillOps, VRM);
676 if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) {
677 MRI->reMaterialize(*MBB, MI, NewPhysReg,
678 VRM.getReMaterializedMI(NewOp.VirtReg));
681 MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg,
682 NewOp.StackSlotOrReMat, AliasRC);
683 // Any stores to this stack slot are not dead anymore.
684 MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL;
687 Spills.ClobberPhysReg(NewPhysReg);
688 Spills.ClobberPhysReg(NewOp.PhysRegReused);
690 MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
692 Spills.addAvailable(NewOp.StackSlotOrReMat, MI, NewPhysReg);
693 MachineBasicBlock::iterator MII = MI;
695 UpdateKills(*MII, RegKills, KillOps);
696 DOUT << '\t' << *MII;
698 DOUT << "Reuse undone!\n";
701 // Finally, PhysReg is now available, go ahead and use it.
709 /// GetRegForReload - Helper for the above GetRegForReload(). Add a
710 /// 'Rejected' set to remember which registers have been considered and
711 /// rejected for the reload. This avoids infinite looping in case like
714 /// t2 <- assigned r0 for use by the reload but ended up reuse r1
715 /// t3 <- assigned r1 for use by the reload but ended up reuse r0
717 /// sees r1 is taken by t2, tries t2's reload register r0
718 /// sees r0 is taken by t3, tries t3's reload register r1
719 /// sees r1 is taken by t2, tries t2's reload register r0 ...
720 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
721 AvailableSpills &Spills,
722 std::vector<MachineInstr*> &MaybeDeadStores,
724 std::vector<MachineOperand*> &KillOps,
726 SmallSet<unsigned, 8> Rejected;
727 return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected,
728 RegKills, KillOps, VRM);
733 /// PrepForUnfoldOpti - Turn a store folding instruction into a load folding
734 /// instruction. e.g.
736 /// movl %eax, -32(%ebp)
737 /// movl -36(%ebp), %eax
738 /// orl %eax, -32(%ebp)
741 /// orl -36(%ebp), %eax
742 /// mov %eax, -32(%ebp)
743 /// This enables unfolding optimization for a subsequent instruction which will
744 /// also eliminate the newly introduced store instruction.
745 bool LocalSpiller::PrepForUnfoldOpti(MachineBasicBlock &MBB,
746 MachineBasicBlock::iterator &MII,
747 std::vector<MachineInstr*> &MaybeDeadStores,
748 AvailableSpills &Spills,
750 std::vector<MachineOperand*> &KillOps,
752 MachineFunction &MF = *MBB.getParent();
753 MachineInstr &MI = *MII;
754 unsigned UnfoldedOpc = 0;
755 unsigned UnfoldPR = 0;
756 unsigned UnfoldVR = 0;
757 int FoldedSS = VirtRegMap::NO_STACK_SLOT;
758 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
759 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
760 // Only transform a MI that folds a single register.
763 UnfoldVR = I->second.first;
764 VirtRegMap::ModRef MR = I->second.second;
765 if (VRM.isAssignedReg(UnfoldVR))
767 // If this reference is not a use, any previous store is now dead.
768 // Otherwise, the store to this stack slot is not dead anymore.
769 FoldedSS = VRM.getStackSlot(UnfoldVR);
770 MachineInstr* DeadStore = MaybeDeadStores[FoldedSS];
771 if (DeadStore && (MR & VirtRegMap::isModRef)) {
772 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(FoldedSS);
774 DeadStore->findRegisterUseOperandIdx(PhysReg, true) == -1)
777 UnfoldedOpc = MRI->getOpcodeAfterMemoryUnfold(MI.getOpcode(),
785 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
786 MachineOperand &MO = MI.getOperand(i);
787 if (!MO.isRegister() || MO.getReg() == 0 || !MO.isUse())
789 unsigned VirtReg = MO.getReg();
790 if (MRegisterInfo::isPhysicalRegister(VirtReg) || MO.getSubReg())
792 if (VRM.isAssignedReg(VirtReg)) {
793 unsigned PhysReg = VRM.getPhys(VirtReg);
794 if (PhysReg && MRI->regsOverlap(PhysReg, UnfoldPR))
796 } else if (VRM.isReMaterialized(VirtReg))
798 int SS = VRM.getStackSlot(VirtReg);
799 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
801 if (MRI->regsOverlap(PhysReg, UnfoldPR))
805 PhysReg = VRM.getPhys(VirtReg);
806 if (!MRI->regsOverlap(PhysReg, UnfoldPR))
809 // Ok, we'll need to reload the value into a register which makes
810 // it impossible to perform the store unfolding optimization later.
811 // Let's see if it is possible to fold the load if the store is
812 // unfolded. This allows us to perform the store unfolding
814 SmallVector<MachineInstr*, 4> NewMIs;
815 if (MRI->unfoldMemoryOperand(MF, &MI, UnfoldVR, false, false, NewMIs)) {
816 assert(NewMIs.size() == 1);
817 MachineInstr *NewMI = NewMIs.back();
819 int Idx = NewMI->findRegisterUseOperandIdx(VirtReg);
821 SmallVector<unsigned, 2> Ops;
823 MachineInstr *FoldedMI = MRI->foldMemoryOperand(NewMI, Ops, SS);
825 if (!VRM.hasPhys(UnfoldVR))
826 VRM.assignVirt2Phys(UnfoldVR, UnfoldPR);
827 VRM.virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef);
828 MII = MBB.insert(MII, FoldedMI);
829 VRM.RemoveMachineInstrFromMaps(&MI);
839 /// findSuperReg - Find the SubReg's super-register of given register class
840 /// where its SubIdx sub-register is SubReg.
841 static unsigned findSuperReg(const TargetRegisterClass *RC, unsigned SubReg,
842 unsigned SubIdx, const MRegisterInfo *MRI) {
843 for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
846 if (MRI->getSubReg(Reg, SubIdx) == SubReg)
852 /// SpillRegToStackSlot - Spill a register to a specified stack slot. Check if
853 /// the last store to the same slot is now dead. If so, remove the last store.
854 void LocalSpiller::SpillRegToStackSlot(MachineBasicBlock &MBB,
855 MachineBasicBlock::iterator &MII,
856 int Idx, unsigned PhysReg, int StackSlot,
857 const TargetRegisterClass *RC,
858 bool isAvailable, MachineInstr *&LastStore,
859 AvailableSpills &Spills,
860 SmallSet<MachineInstr*, 4> &ReMatDefs,
862 std::vector<MachineOperand*> &KillOps,
864 MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
865 DOUT << "Store:\t" << *next(MII);
867 // If there is a dead store to this stack slot, nuke it now.
869 DOUT << "Removed dead store:\t" << *LastStore;
871 SmallVector<unsigned, 2> KillRegs;
872 InvalidateKills(*LastStore, RegKills, KillOps, &KillRegs);
873 MachineBasicBlock::iterator PrevMII = LastStore;
874 bool CheckDef = PrevMII != MBB.begin();
877 MBB.erase(LastStore);
878 VRM.RemoveMachineInstrFromMaps(LastStore);
880 // Look at defs of killed registers on the store. Mark the defs
881 // as dead since the store has been deleted and they aren't
883 for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
884 bool HasOtherDef = false;
885 if (InvalidateRegDef(PrevMII, *MII, KillRegs[j], HasOtherDef)) {
886 MachineInstr *DeadDef = PrevMII;
887 if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
888 // FIXME: This assumes a remat def does not have side
891 VRM.RemoveMachineInstrFromMaps(DeadDef);
899 LastStore = next(MII);
901 // If the stack slot value was previously available in some other
902 // register, change it now. Otherwise, make the register available,
904 Spills.ModifyStackSlotOrReMat(StackSlot);
905 Spills.ClobberPhysReg(PhysReg);
906 Spills.addAvailable(StackSlot, LastStore, PhysReg, isAvailable);
910 /// rewriteMBB - Keep track of which spills are available even after the
911 /// register allocator is done with them. If possible, avid reloading vregs.
912 void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
913 DOUT << MBB.getBasicBlock()->getName() << ":\n";
915 MachineFunction &MF = *MBB.getParent();
917 // Spills - Keep track of which spilled values are available in physregs so
918 // that we can choose to reuse the physregs instead of emitting reloads.
919 AvailableSpills Spills(MRI, TII);
921 // MaybeDeadStores - When we need to write a value back into a stack slot,
922 // keep track of the inserted store. If the stack slot value is never read
923 // (because the value was used from some available register, for example), and
924 // subsequently stored to, the original store is dead. This map keeps track
925 // of inserted stores that are not used. If we see a subsequent store to the
926 // same stack slot, the original store is deleted.
927 std::vector<MachineInstr*> MaybeDeadStores;
928 MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL);
930 // ReMatDefs - These are rematerializable def MIs which are not deleted.
931 SmallSet<MachineInstr*, 4> ReMatDefs;
933 // Keep track of kill information.
934 BitVector RegKills(MRI->getNumRegs());
935 std::vector<MachineOperand*> KillOps;
936 KillOps.resize(MRI->getNumRegs(), NULL);
938 for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
940 MachineBasicBlock::iterator NextMII = MII; ++NextMII;
942 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
944 bool BackTracked = false;
945 if (PrepForUnfoldOpti(MBB, MII,
946 MaybeDeadStores, Spills, RegKills, KillOps, VRM))
949 MachineInstr &MI = *MII;
950 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
952 // Insert restores here if asked to.
953 if (VRM.isRestorePt(&MI)) {
954 std::vector<unsigned> &RestoreRegs = VRM.getRestorePtRestores(&MI);
955 for (unsigned i = 0, e = RestoreRegs.size(); i != e; ++i) {
956 unsigned VirtReg = RestoreRegs[i];
957 if (!VRM.getPreSplitReg(VirtReg))
958 continue; // Split interval spilled again.
959 unsigned Phys = VRM.getPhys(VirtReg);
960 MF.setPhysRegUsed(Phys);
961 if (VRM.isReMaterialized(VirtReg)) {
962 MRI->reMaterialize(MBB, &MI, Phys,
963 VRM.getReMaterializedMI(VirtReg));
966 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
967 MRI->loadRegFromStackSlot(MBB, &MI, Phys, VRM.getStackSlot(VirtReg), RC);
970 // This invalidates Phys.
971 Spills.ClobberPhysReg(Phys);
972 UpdateKills(*prior(MII), RegKills, KillOps);
973 DOUT << '\t' << *prior(MII);
977 // Insert spills here if asked to.
978 if (VRM.isSpillPt(&MI)) {
979 std::vector<unsigned> &SpillRegs = VRM.getSpillPtSpills(&MI);
980 for (unsigned i = 0, e = SpillRegs.size(); i != e; ++i) {
981 unsigned VirtReg = SpillRegs[i];
982 if (!VRM.getPreSplitReg(VirtReg))
983 continue; // Split interval spilled again.
984 const TargetRegisterClass *RC = RegMap->getRegClass(VirtReg);
985 unsigned Phys = VRM.getPhys(VirtReg);
986 int StackSlot = VRM.getStackSlot(VirtReg);
987 MRI->storeRegToStackSlot(MBB, next(MII), Phys, StackSlot, RC);
988 DOUT << "Store:\t" << *next(MII);
989 VRM.virtFolded(VirtReg, next(MII), VirtRegMap::isMod);
994 /// ReusedOperands - Keep track of operand reuse in case we need to undo
996 ReuseInfo ReusedOperands(MI, MRI);
997 // Process all of the spilled uses and all non spilled reg references.
998 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
999 MachineOperand &MO = MI.getOperand(i);
1000 if (!MO.isRegister() || MO.getReg() == 0)
1001 continue; // Ignore non-register operands.
1003 unsigned VirtReg = MO.getReg();
1004 if (MRegisterInfo::isPhysicalRegister(VirtReg)) {
1005 // Ignore physregs for spilling, but remember that it is used by this
1007 MF.setPhysRegUsed(VirtReg);
1011 assert(MRegisterInfo::isVirtualRegister(VirtReg) &&
1012 "Not a virtual or a physical register?");
1014 // Assumes this is the last use of a split interval. IsKill will be unset
1015 // if reg is use later unless it's a two-address operand.
1016 if (MO.isUse() && VRM.getPreSplitReg(VirtReg) &&
1017 TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
1018 MI.getOperand(i).setIsKill();
1020 unsigned SubIdx = MO.getSubReg();
1021 if (VRM.isAssignedReg(VirtReg)) {
1022 // This virtual register was assigned a physreg!
1023 unsigned Phys = VRM.getPhys(VirtReg);
1024 MF.setPhysRegUsed(Phys);
1026 ReusedOperands.markClobbered(Phys);
1027 unsigned RReg = SubIdx ? MRI->getSubReg(Phys, SubIdx) : Phys;
1028 MI.getOperand(i).setReg(RReg);
1032 // This virtual register is now known to be a spilled value.
1034 continue; // Handle defs in the loop below (handle use&def here though)
1036 bool DoReMat = VRM.isReMaterialized(VirtReg);
1037 int SSorRMId = DoReMat
1038 ? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
1039 int ReuseSlot = SSorRMId;
1041 // Check to see if this stack slot is available.
1042 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
1044 // If this is a sub-register use, make sure the reuse register is in the
1045 // right register class. For example, for x86 not all of the 32-bit
1046 // registers have accessible sub-registers.
1047 // Similarly so for EXTRACT_SUBREG. Consider this:
1049 // MOV32_mr fi#1, EDI
1051 // = EXTRACT_SUBREG fi#1
1052 // fi#1 is available in EDI, but it cannot be reused because it's not in
1053 // the right register file.
1055 (SubIdx || MI.getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)) {
1056 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
1057 if (!RC->contains(PhysReg))
1062 // This spilled operand might be part of a two-address operand. If this
1063 // is the case, then changing it will necessarily require changing the
1064 // def part of the instruction as well. However, in some cases, we
1065 // aren't allowed to modify the reused register. If none of these cases
1067 bool CanReuse = true;
1068 int ti = TID->getOperandConstraint(i, TOI::TIED_TO);
1070 MI.getOperand(ti).isRegister() &&
1071 MI.getOperand(ti).getReg() == VirtReg) {
1072 // Okay, we have a two address operand. We can reuse this physreg as
1073 // long as we are allowed to clobber the value and there isn't an
1074 // earlier def that has already clobbered the physreg.
1075 CanReuse = Spills.canClobberPhysReg(ReuseSlot) &&
1076 !ReusedOperands.isClobbered(PhysReg);
1080 // If this stack slot value is already available, reuse it!
1081 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
1082 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
1084 DOUT << "Reusing SS#" << ReuseSlot;
1085 DOUT << " from physreg "
1086 << MRI->getName(PhysReg) << " for vreg"
1087 << VirtReg <<" instead of reloading into physreg "
1088 << MRI->getName(VRM.getPhys(VirtReg)) << "\n";
1089 unsigned RReg = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
1090 MI.getOperand(i).setReg(RReg);
1092 // The only technical detail we have is that we don't know that
1093 // PhysReg won't be clobbered by a reloaded stack slot that occurs
1094 // later in the instruction. In particular, consider 'op V1, V2'.
1095 // If V1 is available in physreg R0, we would choose to reuse it
1096 // here, instead of reloading it into the register the allocator
1097 // indicated (say R1). However, V2 might have to be reloaded
1098 // later, and it might indicate that it needs to live in R0. When
1099 // this occurs, we need to have information available that
1100 // indicates it is safe to use R1 for the reload instead of R0.
1102 // To further complicate matters, we might conflict with an alias,
1103 // or R0 and R1 might not be compatible with each other. In this
1104 // case, we actually insert a reload for V1 in R1, ensuring that
1105 // we can get at R0 or its alias.
1106 ReusedOperands.addReuse(i, ReuseSlot, PhysReg,
1107 VRM.getPhys(VirtReg), VirtReg);
1109 // Only mark it clobbered if this is a use&def operand.
1110 ReusedOperands.markClobbered(PhysReg);
1113 if (MI.getOperand(i).isKill() &&
1114 ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) {
1115 // This was the last use and the spilled value is still available
1116 // for reuse. That means the spill was unnecessary!
1117 MachineInstr* DeadStore = MaybeDeadStores[ReuseSlot];
1119 DOUT << "Removed dead store:\t" << *DeadStore;
1120 InvalidateKills(*DeadStore, RegKills, KillOps);
1121 VRM.RemoveMachineInstrFromMaps(DeadStore);
1122 MBB.erase(DeadStore);
1123 MaybeDeadStores[ReuseSlot] = NULL;
1130 // Otherwise we have a situation where we have a two-address instruction
1131 // whose mod/ref operand needs to be reloaded. This reload is already
1132 // available in some register "PhysReg", but if we used PhysReg as the
1133 // operand to our 2-addr instruction, the instruction would modify
1134 // PhysReg. This isn't cool if something later uses PhysReg and expects
1135 // to get its initial value.
1137 // To avoid this problem, and to avoid doing a load right after a store,
1138 // we emit a copy from PhysReg into the designated register for this
1140 unsigned DesignatedReg = VRM.getPhys(VirtReg);
1141 assert(DesignatedReg && "Must map virtreg to physreg!");
1143 // Note that, if we reused a register for a previous operand, the
1144 // register we want to reload into might not actually be
1145 // available. If this occurs, use the register indicated by the
1147 if (ReusedOperands.hasReuses())
1148 DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
1149 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
1151 // If the mapped designated register is actually the physreg we have
1152 // incoming, we don't need to inserted a dead copy.
1153 if (DesignatedReg == PhysReg) {
1154 // If this stack slot value is already available, reuse it!
1155 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
1156 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
1158 DOUT << "Reusing SS#" << ReuseSlot;
1159 DOUT << " from physreg " << MRI->getName(PhysReg) << " for vreg"
1161 << " instead of reloading into same physreg.\n";
1162 unsigned RReg = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
1163 MI.getOperand(i).setReg(RReg);
1164 ReusedOperands.markClobbered(RReg);
1169 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
1170 MF.setPhysRegUsed(DesignatedReg);
1171 ReusedOperands.markClobbered(DesignatedReg);
1172 MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC, RC);
1174 MachineInstr *CopyMI = prior(MII);
1175 UpdateKills(*CopyMI, RegKills, KillOps);
1177 // This invalidates DesignatedReg.
1178 Spills.ClobberPhysReg(DesignatedReg);
1180 Spills.addAvailable(ReuseSlot, &MI, DesignatedReg);
1182 SubIdx ? MRI->getSubReg(DesignatedReg, SubIdx) : DesignatedReg;
1183 MI.getOperand(i).setReg(RReg);
1184 DOUT << '\t' << *prior(MII);
1189 // Otherwise, reload it and remember that we have it.
1190 PhysReg = VRM.getPhys(VirtReg);
1191 assert(PhysReg && "Must map virtreg to physreg!");
1193 // Note that, if we reused a register for a previous operand, the
1194 // register we want to reload into might not actually be
1195 // available. If this occurs, use the register indicated by the
1197 if (ReusedOperands.hasReuses())
1198 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
1199 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
1201 MF.setPhysRegUsed(PhysReg);
1202 ReusedOperands.markClobbered(PhysReg);
1204 MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg));
1207 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
1208 MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, SSorRMId, RC);
1211 // This invalidates PhysReg.
1212 Spills.ClobberPhysReg(PhysReg);
1214 // Any stores to this stack slot are not dead anymore.
1216 MaybeDeadStores[SSorRMId] = NULL;
1217 Spills.addAvailable(SSorRMId, &MI, PhysReg);
1218 // Assumes this is the last use. IsKill will be unset if reg is reused
1219 // unless it's a two-address operand.
1220 if (TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
1221 MI.getOperand(i).setIsKill();
1222 unsigned RReg = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
1223 MI.getOperand(i).setReg(RReg);
1224 UpdateKills(*prior(MII), RegKills, KillOps);
1225 DOUT << '\t' << *prior(MII);
1231 // If we have folded references to memory operands, make sure we clear all
1232 // physical registers that may contain the value of the spilled virtual
1234 SmallSet<int, 2> FoldedSS;
1235 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
1236 unsigned VirtReg = I->second.first;
1237 VirtRegMap::ModRef MR = I->second.second;
1238 DOUT << "Folded vreg: " << VirtReg << " MR: " << MR;
1240 int SS = VRM.getStackSlot(VirtReg);
1241 if (SS == VirtRegMap::NO_STACK_SLOT)
1243 FoldedSS.insert(SS);
1244 DOUT << " - StackSlot: " << SS << "\n";
1246 // If this folded instruction is just a use, check to see if it's a
1247 // straight load from the virt reg slot.
1248 if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
1250 unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx);
1251 if (DestReg && FrameIdx == SS) {
1252 // If this spill slot is available, turn it into a copy (or nothing)
1253 // instead of leaving it as a load!
1254 if (unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SS)) {
1255 DOUT << "Promoted Load To Copy: " << MI;
1256 if (DestReg != InReg) {
1257 const TargetRegisterClass *RC = RegMap->getRegClass(VirtReg);
1258 MRI->copyRegToReg(MBB, &MI, DestReg, InReg, RC, RC);
1259 // Revisit the copy so we make sure to notice the effects of the
1260 // operation on the destreg (either needing to RA it if it's
1261 // virtual or needing to clobber any values if it's physical).
1263 --NextMII; // backtrack to the copy.
1266 DOUT << "Removing now-noop copy: " << MI;
1268 VRM.RemoveMachineInstrFromMaps(&MI);
1271 goto ProcessNextInst;
1274 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
1275 SmallVector<MachineInstr*, 4> NewMIs;
1277 MRI->unfoldMemoryOperand(MF, &MI, PhysReg, false, false, NewMIs)) {
1278 MBB.insert(MII, NewMIs[0]);
1279 VRM.RemoveMachineInstrFromMaps(&MI);
1282 --NextMII; // backtrack to the unfolded instruction.
1284 goto ProcessNextInst;
1289 // If this reference is not a use, any previous store is now dead.
1290 // Otherwise, the store to this stack slot is not dead anymore.
1291 MachineInstr* DeadStore = MaybeDeadStores[SS];
1293 bool isDead = !(MR & VirtRegMap::isRef);
1294 MachineInstr *NewStore = NULL;
1295 if (MR & VirtRegMap::isModRef) {
1296 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
1297 SmallVector<MachineInstr*, 4> NewMIs;
1298 // We can reuse this physreg as long as we are allowed to clobber
1299 // the value and there isn't an earlier def that has already clobbered the
1302 Spills.canClobberPhysReg(SS) &&
1303 !ReusedOperands.isClobbered(PhysReg) &&
1304 DeadStore->findRegisterUseOperandIdx(PhysReg, true) != -1 &&
1305 MRI->unfoldMemoryOperand(MF, &MI, PhysReg, false, true, NewMIs)) {
1306 MBB.insert(MII, NewMIs[0]);
1307 NewStore = NewMIs[1];
1308 MBB.insert(MII, NewStore);
1309 VRM.RemoveMachineInstrFromMaps(&MI);
1313 --NextMII; // backtrack to the unfolded instruction.
1319 if (isDead) { // Previous store is dead.
1320 // If we get here, the store is dead, nuke it now.
1321 DOUT << "Removed dead store:\t" << *DeadStore;
1322 InvalidateKills(*DeadStore, RegKills, KillOps);
1323 VRM.RemoveMachineInstrFromMaps(DeadStore);
1324 MBB.erase(DeadStore);
1329 MaybeDeadStores[SS] = NULL;
1331 // Treat this store as a spill merged into a copy. That makes the
1332 // stack slot value available.
1333 VRM.virtFolded(VirtReg, NewStore, VirtRegMap::isMod);
1334 goto ProcessNextInst;
1338 // If the spill slot value is available, and this is a new definition of
1339 // the value, the value is not available anymore.
1340 if (MR & VirtRegMap::isMod) {
1341 // Notice that the value in this stack slot has been modified.
1342 Spills.ModifyStackSlotOrReMat(SS);
1344 // If this is *just* a mod of the value, check to see if this is just a
1345 // store to the spill slot (i.e. the spill got merged into the copy). If
1346 // so, realize that the vreg is available now, and add the store to the
1347 // MaybeDeadStore info.
1349 if (!(MR & VirtRegMap::isRef)) {
1350 if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
1351 assert(MRegisterInfo::isPhysicalRegister(SrcReg) &&
1352 "Src hasn't been allocated yet?");
1353 // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
1354 // this as a potentially dead store in case there is a subsequent
1355 // store into the stack slot without a read from it.
1356 MaybeDeadStores[StackSlot] = &MI;
1358 // If the stack slot value was previously available in some other
1359 // register, change it now. Otherwise, make the register available,
1361 Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/);
1367 // Process all of the spilled defs.
1368 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
1369 MachineOperand &MO = MI.getOperand(i);
1370 if (!(MO.isRegister() && MO.getReg() && MO.isDef()))
1373 unsigned VirtReg = MO.getReg();
1374 if (!MRegisterInfo::isVirtualRegister(VirtReg)) {
1375 // Check to see if this is a noop copy. If so, eliminate the
1376 // instruction before considering the dest reg to be changed.
1378 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1380 DOUT << "Removing now-noop copy: " << MI;
1383 VRM.RemoveMachineInstrFromMaps(&MI);
1384 Spills.disallowClobberPhysReg(VirtReg);
1385 goto ProcessNextInst;
1388 // If it's not a no-op copy, it clobbers the value in the destreg.
1389 Spills.ClobberPhysReg(VirtReg);
1390 ReusedOperands.markClobbered(VirtReg);
1392 // Check to see if this instruction is a load from a stack slot into
1393 // a register. If so, this provides the stack slot value in the reg.
1395 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
1396 assert(DestReg == VirtReg && "Unknown load situation!");
1398 // If it is a folded reference, then it's not safe to clobber.
1399 bool Folded = FoldedSS.count(FrameIdx);
1400 // Otherwise, if it wasn't available, remember that it is now!
1401 Spills.addAvailable(FrameIdx, &MI, DestReg, !Folded);
1402 goto ProcessNextInst;
1408 unsigned SubIdx = MO.getSubReg();
1409 bool DoReMat = VRM.isReMaterialized(VirtReg);
1411 ReMatDefs.insert(&MI);
1413 // The only vregs left are stack slot definitions.
1414 int StackSlot = VRM.getStackSlot(VirtReg);
1415 const TargetRegisterClass *RC = RegMap->getRegClass(VirtReg);
1417 // If this def is part of a two-address operand, make sure to execute
1418 // the store from the correct physical register.
1420 int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i);
1422 PhysReg = MI.getOperand(TiedOp).getReg();
1424 unsigned SuperReg = findSuperReg(RC, PhysReg, SubIdx, MRI);
1425 assert(SuperReg && MRI->getSubReg(SuperReg, SubIdx) == PhysReg &&
1426 "Can't find corresponding super-register!");
1430 PhysReg = VRM.getPhys(VirtReg);
1431 if (ReusedOperands.isClobbered(PhysReg)) {
1432 // Another def has taken the assigned physreg. It must have been a
1433 // use&def which got it due to reuse. Undo the reuse!
1434 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
1435 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
1439 MF.setPhysRegUsed(PhysReg);
1440 unsigned RReg = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
1441 ReusedOperands.markClobbered(RReg);
1442 MI.getOperand(i).setReg(RReg);
1445 MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
1446 SpillRegToStackSlot(MBB, MII, -1, PhysReg, StackSlot, RC, true,
1447 LastStore, Spills, ReMatDefs, RegKills, KillOps, VRM);
1448 NextMII = next(MII);
1450 // Check to see if this is a noop copy. If so, eliminate the
1451 // instruction before considering the dest reg to be changed.
1454 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1456 DOUT << "Removing now-noop copy: " << MI;
1459 VRM.RemoveMachineInstrFromMaps(&MI);
1460 UpdateKills(*LastStore, RegKills, KillOps);
1461 goto ProcessNextInst;
1467 if (!Erased && !BackTracked) {
1468 for (MachineBasicBlock::iterator II = MI; II != NextMII; ++II)
1469 UpdateKills(*II, RegKills, KillOps);
1475 llvm::Spiller* llvm::createSpiller() {
1476 switch (SpillerOpt) {
1477 default: assert(0 && "Unreachable!");
1479 return new LocalSpiller();
1481 return new SimpleSpiller();