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 Virt2SplitKillMap(0), 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 Virt2SplitKillMap.grow(LastVirtReg);
78 ReMatMap.grow(LastVirtReg);
81 int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
82 assert(MRegisterInfo::isVirtualRegister(virtReg));
83 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
84 "attempt to assign stack slot to already spilled register");
85 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(virtReg);
86 int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
88 Virt2StackSlotMap[virtReg] = frameIndex;
93 void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) {
94 assert(MRegisterInfo::isVirtualRegister(virtReg));
95 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
96 "attempt to assign stack slot to already spilled register");
97 assert((frameIndex >= 0 ||
98 (frameIndex >= MF.getFrameInfo()->getObjectIndexBegin())) &&
99 "illegal fixed frame index");
100 Virt2StackSlotMap[virtReg] = frameIndex;
103 int VirtRegMap::assignVirtReMatId(unsigned virtReg) {
104 assert(MRegisterInfo::isVirtualRegister(virtReg));
105 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
106 "attempt to assign re-mat id to already spilled register");
107 Virt2ReMatIdMap[virtReg] = ReMatId;
111 void VirtRegMap::assignVirtReMatId(unsigned virtReg, int id) {
112 assert(MRegisterInfo::isVirtualRegister(virtReg));
113 assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
114 "attempt to assign re-mat id to already spilled register");
115 Virt2ReMatIdMap[virtReg] = id;
118 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
119 MachineInstr *NewMI, ModRef MRInfo) {
120 // Move previous memory references folded to new instruction.
121 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
122 for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
123 E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
124 MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
125 MI2VirtMap.erase(I++);
128 // add new memory reference
129 MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
132 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *MI, ModRef MRInfo) {
133 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(MI);
134 MI2VirtMap.insert(IP, std::make_pair(MI, std::make_pair(VirtReg, MRInfo)));
137 void VirtRegMap::print(std::ostream &OS) const {
138 const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
140 OS << "********** REGISTER MAP **********\n";
141 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
142 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) {
143 if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG)
144 OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n";
148 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
149 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i)
150 if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT)
151 OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n";
155 void VirtRegMap::dump() const {
160 //===----------------------------------------------------------------------===//
161 // Simple Spiller Implementation
162 //===----------------------------------------------------------------------===//
164 Spiller::~Spiller() {}
167 struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller {
168 bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM);
172 bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
173 DOUT << "********** REWRITE MACHINE CODE **********\n";
174 DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
175 const TargetMachine &TM = MF.getTarget();
176 const MRegisterInfo &MRI = *TM.getRegisterInfo();
178 // LoadedRegs - Keep track of which vregs are loaded, so that we only load
179 // each vreg once (in the case where a spilled vreg is used by multiple
180 // operands). This is always smaller than the number of operands to the
181 // current machine instr, so it should be small.
182 std::vector<unsigned> LoadedRegs;
184 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
186 DOUT << MBBI->getBasicBlock()->getName() << ":\n";
187 MachineBasicBlock &MBB = *MBBI;
188 for (MachineBasicBlock::iterator MII = MBB.begin(),
189 E = MBB.end(); MII != E; ++MII) {
190 MachineInstr &MI = *MII;
191 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
192 MachineOperand &MO = MI.getOperand(i);
193 if (MO.isRegister() && MO.getReg())
194 if (MRegisterInfo::isVirtualRegister(MO.getReg())) {
195 unsigned VirtReg = MO.getReg();
196 unsigned PhysReg = VRM.getPhys(VirtReg);
197 if (!VRM.isAssignedReg(VirtReg)) {
198 int StackSlot = VRM.getStackSlot(VirtReg);
199 const TargetRegisterClass* RC =
200 MF.getSSARegMap()->getRegClass(VirtReg);
203 std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
204 == LoadedRegs.end()) {
205 MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
206 LoadedRegs.push_back(VirtReg);
208 DOUT << '\t' << *prior(MII);
212 MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, true,
217 MF.setPhysRegUsed(PhysReg);
218 MI.getOperand(i).setReg(PhysReg);
220 MF.setPhysRegUsed(MO.getReg());
231 //===----------------------------------------------------------------------===//
232 // Local Spiller Implementation
233 //===----------------------------------------------------------------------===//
236 class AvailableSpills;
238 /// LocalSpiller - This spiller does a simple pass over the machine basic
239 /// block to attempt to keep spills in registers as much as possible for
240 /// blocks that have low register pressure (the vreg may be spilled due to
241 /// register pressure in other blocks).
242 class VISIBILITY_HIDDEN LocalSpiller : public Spiller {
244 const MRegisterInfo *MRI;
245 const TargetInstrInfo *TII;
247 bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
248 RegMap = MF.getSSARegMap();
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 bool PrepForUnfoldOpti(MachineBasicBlock &MBB,
267 MachineBasicBlock::iterator &MII,
268 std::vector<MachineInstr*> &MaybeDeadStores,
269 AvailableSpills &Spills, BitVector &RegKills,
270 std::vector<MachineOperand*> &KillOps,
272 void SpillRegToStackSlot(MachineBasicBlock &MBB,
273 MachineBasicBlock::iterator &MII,
274 int Idx, unsigned PhysReg, int StackSlot,
275 const TargetRegisterClass *RC,
276 bool isAvailable, MachineInstr *&LastStore,
277 AvailableSpills &Spills,
278 SmallSet<MachineInstr*, 4> &ReMatDefs,
280 std::vector<MachineOperand*> &KillOps,
282 void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
286 /// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
287 /// top down, keep track of which spills slots or remat are available in each
290 /// Note that not all physregs are created equal here. In particular, some
291 /// physregs are reloads that we are allowed to clobber or ignore at any time.
292 /// Other physregs are values that the register allocated program is using that
293 /// we cannot CHANGE, but we can read if we like. We keep track of this on a
294 /// per-stack-slot / remat id basis as the low bit in the value of the
295 /// SpillSlotsAvailable entries. The predicate 'canClobberPhysReg()' checks
296 /// this bit and addAvailable sets it if.
298 class VISIBILITY_HIDDEN AvailableSpills {
299 const MRegisterInfo *MRI;
300 const TargetInstrInfo *TII;
302 // SpillSlotsOrReMatsAvailable - This map keeps track of all of the spilled
303 // or remat'ed virtual register values that are still available, due to being
304 // loaded or stored to, but not invalidated yet.
305 std::map<int, unsigned> SpillSlotsOrReMatsAvailable;
307 // PhysRegsAvailable - This is the inverse of SpillSlotsOrReMatsAvailable,
308 // indicating which stack slot values are currently held by a physreg. This
309 // is used to invalidate entries in SpillSlotsOrReMatsAvailable when a
310 // physreg is modified.
311 std::multimap<unsigned, int> PhysRegsAvailable;
313 void disallowClobberPhysRegOnly(unsigned PhysReg);
315 void ClobberPhysRegOnly(unsigned PhysReg);
317 AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
318 : MRI(mri), TII(tii) {
321 const MRegisterInfo *getRegInfo() const { return MRI; }
323 /// getSpillSlotOrReMatPhysReg - If the specified stack slot or remat is
324 /// available in a physical register, return that PhysReg, otherwise
326 unsigned getSpillSlotOrReMatPhysReg(int Slot) const {
327 std::map<int, unsigned>::const_iterator I =
328 SpillSlotsOrReMatsAvailable.find(Slot);
329 if (I != SpillSlotsOrReMatsAvailable.end()) {
330 return I->second >> 1; // Remove the CanClobber bit.
335 /// addAvailable - Mark that the specified stack slot / remat is available in
336 /// the specified physreg. If CanClobber is true, the physreg can be modified
337 /// at any time without changing the semantics of the program.
338 void addAvailable(int SlotOrReMat, MachineInstr *MI, unsigned Reg,
339 bool CanClobber = true) {
340 // If this stack slot is thought to be available in some other physreg,
341 // remove its record.
342 ModifyStackSlotOrReMat(SlotOrReMat);
344 PhysRegsAvailable.insert(std::make_pair(Reg, SlotOrReMat));
345 SpillSlotsOrReMatsAvailable[SlotOrReMat]= (Reg << 1) | (unsigned)CanClobber;
347 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
348 DOUT << "Remembering RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1;
350 DOUT << "Remembering SS#" << SlotOrReMat;
351 DOUT << " in physreg " << MRI->getName(Reg) << "\n";
354 /// canClobberPhysReg - Return true if the spiller is allowed to change the
355 /// value of the specified stackslot register if it desires. The specified
356 /// stack slot must be available in a physreg for this query to make sense.
357 bool canClobberPhysReg(int SlotOrReMat) const {
358 assert(SpillSlotsOrReMatsAvailable.count(SlotOrReMat) &&
359 "Value not available!");
360 return SpillSlotsOrReMatsAvailable.find(SlotOrReMat)->second & 1;
363 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
364 /// stackslot register. The register is still available but is no longer
365 /// allowed to be modifed.
366 void disallowClobberPhysReg(unsigned PhysReg);
368 /// ClobberPhysReg - This is called when the specified physreg changes
369 /// value. We use this to invalidate any info about stuff that lives in
370 /// it and any of its aliases.
371 void ClobberPhysReg(unsigned PhysReg);
373 /// ModifyStackSlotOrReMat - This method is called when the value in a stack
374 /// slot changes. This removes information about which register the previous
375 /// value for this slot lives in (as the previous value is dead now).
376 void ModifyStackSlotOrReMat(int SlotOrReMat);
380 /// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
381 /// stackslot register. The register is still available but is no longer
382 /// allowed to be modifed.
383 void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
384 std::multimap<unsigned, int>::iterator I =
385 PhysRegsAvailable.lower_bound(PhysReg);
386 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
387 int SlotOrReMat = I->second;
389 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
390 "Bidirectional map mismatch!");
391 SpillSlotsOrReMatsAvailable[SlotOrReMat] &= ~1;
392 DOUT << "PhysReg " << MRI->getName(PhysReg)
393 << " copied, it is available for use but can no longer be modified\n";
397 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
398 /// stackslot register and its aliases. The register and its aliases may
399 /// still available but is no longer allowed to be modifed.
400 void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
401 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
402 disallowClobberPhysRegOnly(*AS);
403 disallowClobberPhysRegOnly(PhysReg);
406 /// ClobberPhysRegOnly - This is called when the specified physreg changes
407 /// value. We use this to invalidate any info about stuff we thing lives in it.
408 void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
409 std::multimap<unsigned, int>::iterator I =
410 PhysRegsAvailable.lower_bound(PhysReg);
411 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
412 int SlotOrReMat = I->second;
413 PhysRegsAvailable.erase(I++);
414 assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
415 "Bidirectional map mismatch!");
416 SpillSlotsOrReMatsAvailable.erase(SlotOrReMat);
417 DOUT << "PhysReg " << MRI->getName(PhysReg)
418 << " clobbered, invalidating ";
419 if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
420 DOUT << "RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1 << "\n";
422 DOUT << "SS#" << SlotOrReMat << "\n";
426 /// ClobberPhysReg - This is called when the specified physreg changes
427 /// value. We use this to invalidate any info about stuff we thing lives in
428 /// it and any of its aliases.
429 void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
430 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
431 ClobberPhysRegOnly(*AS);
432 ClobberPhysRegOnly(PhysReg);
435 /// ModifyStackSlotOrReMat - This method is called when the value in a stack
436 /// slot changes. This removes information about which register the previous
437 /// value for this slot lives in (as the previous value is dead now).
438 void AvailableSpills::ModifyStackSlotOrReMat(int SlotOrReMat) {
439 std::map<int, unsigned>::iterator It =
440 SpillSlotsOrReMatsAvailable.find(SlotOrReMat);
441 if (It == SpillSlotsOrReMatsAvailable.end()) return;
442 unsigned Reg = It->second >> 1;
443 SpillSlotsOrReMatsAvailable.erase(It);
445 // This register may hold the value of multiple stack slots, only remove this
446 // stack slot from the set of values the register contains.
447 std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
449 assert(I != PhysRegsAvailable.end() && I->first == Reg &&
450 "Map inverse broken!");
451 if (I->second == SlotOrReMat) break;
453 PhysRegsAvailable.erase(I);
458 /// InvalidateKills - MI is going to be deleted. If any of its operands are
459 /// marked kill, then invalidate the information.
460 static void InvalidateKills(MachineInstr &MI, BitVector &RegKills,
461 std::vector<MachineOperand*> &KillOps,
462 SmallVector<unsigned, 2> *KillRegs = NULL) {
463 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
464 MachineOperand &MO = MI.getOperand(i);
465 if (!MO.isRegister() || !MO.isUse() || !MO.isKill())
467 unsigned Reg = MO.getReg();
469 KillRegs->push_back(Reg);
470 if (KillOps[Reg] == &MO) {
477 /// InvalidateRegDef - If the def operand of the specified def MI is now dead
478 /// (since it's spill instruction is removed), mark it isDead. Also checks if
479 /// the def MI has other definition operands that are not dead. Returns it by
481 static bool InvalidateRegDef(MachineBasicBlock::iterator I,
482 MachineInstr &NewDef, unsigned Reg,
484 // Due to remat, it's possible this reg isn't being reused. That is,
485 // the def of this reg (by prev MI) is now dead.
486 MachineInstr *DefMI = I;
487 MachineOperand *DefOp = NULL;
488 for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) {
489 MachineOperand &MO = DefMI->getOperand(i);
490 if (MO.isRegister() && MO.isDef()) {
491 if (MO.getReg() == Reg)
493 else if (!MO.isDead())
500 bool FoundUse = false, Done = false;
501 MachineBasicBlock::iterator E = NewDef;
503 for (; !Done && I != E; ++I) {
504 MachineInstr *NMI = I;
505 for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) {
506 MachineOperand &MO = NMI->getOperand(j);
507 if (!MO.isRegister() || MO.getReg() != Reg)
511 Done = true; // Stop after scanning all the operands of this MI.
522 /// UpdateKills - Track and update kill info. If a MI reads a register that is
523 /// marked kill, then it must be due to register reuse. Transfer the kill info
525 static void UpdateKills(MachineInstr &MI, BitVector &RegKills,
526 std::vector<MachineOperand*> &KillOps) {
527 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
528 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
529 MachineOperand &MO = MI.getOperand(i);
530 if (!MO.isRegister() || !MO.isUse())
532 unsigned Reg = MO.getReg();
537 // That can't be right. Register is killed but not re-defined and it's
538 // being reused. Let's fix that.
539 KillOps[Reg]->unsetIsKill();
540 if (i < TID->numOperands &&
541 TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
542 // Unless it's a two-address operand, this is the new kill.
552 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
553 const MachineOperand &MO = MI.getOperand(i);
554 if (!MO.isRegister() || !MO.isDef())
556 unsigned Reg = MO.getReg();
563 // ReusedOp - For each reused operand, we keep track of a bit of information, in
564 // case we need to rollback upon processing a new operand. See comments below.
567 // The MachineInstr operand that reused an available value.
570 // StackSlotOrReMat - The spill slot or remat id of the value being reused.
571 unsigned StackSlotOrReMat;
573 // PhysRegReused - The physical register the value was available in.
574 unsigned PhysRegReused;
576 // AssignedPhysReg - The physreg that was assigned for use by the reload.
577 unsigned AssignedPhysReg;
579 // VirtReg - The virtual register itself.
582 ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
584 : Operand(o), StackSlotOrReMat(ss), PhysRegReused(prr),
585 AssignedPhysReg(apr), VirtReg(vreg) {}
588 /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
589 /// is reused instead of reloaded.
590 class VISIBILITY_HIDDEN ReuseInfo {
592 std::vector<ReusedOp> Reuses;
593 BitVector PhysRegsClobbered;
595 ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
596 PhysRegsClobbered.resize(mri->getNumRegs());
599 bool hasReuses() const {
600 return !Reuses.empty();
603 /// addReuse - If we choose to reuse a virtual register that is already
604 /// available instead of reloading it, remember that we did so.
605 void addReuse(unsigned OpNo, unsigned StackSlotOrReMat,
606 unsigned PhysRegReused, unsigned AssignedPhysReg,
608 // If the reload is to the assigned register anyway, no undo will be
610 if (PhysRegReused == AssignedPhysReg) return;
612 // Otherwise, remember this.
613 Reuses.push_back(ReusedOp(OpNo, StackSlotOrReMat, PhysRegReused,
614 AssignedPhysReg, VirtReg));
617 void markClobbered(unsigned PhysReg) {
618 PhysRegsClobbered.set(PhysReg);
621 bool isClobbered(unsigned PhysReg) const {
622 return PhysRegsClobbered.test(PhysReg);
625 /// GetRegForReload - We are about to emit a reload into PhysReg. If there
626 /// is some other operand that is using the specified register, either pick
627 /// a new register to use, or evict the previous reload and use this reg.
628 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
629 AvailableSpills &Spills,
630 std::vector<MachineInstr*> &MaybeDeadStores,
631 SmallSet<unsigned, 8> &Rejected,
633 std::vector<MachineOperand*> &KillOps,
635 if (Reuses.empty()) return PhysReg; // This is most often empty.
637 for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
638 ReusedOp &Op = Reuses[ro];
639 // If we find some other reuse that was supposed to use this register
640 // exactly for its reload, we can change this reload to use ITS reload
641 // register. That is, unless its reload register has already been
642 // considered and subsequently rejected because it has also been reused
643 // by another operand.
644 if (Op.PhysRegReused == PhysReg &&
645 Rejected.count(Op.AssignedPhysReg) == 0) {
646 // Yup, use the reload register that we didn't use before.
647 unsigned NewReg = Op.AssignedPhysReg;
648 Rejected.insert(PhysReg);
649 return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected,
650 RegKills, KillOps, VRM);
652 // Otherwise, we might also have a problem if a previously reused
653 // value aliases the new register. If so, codegen the previous reload
655 unsigned PRRU = Op.PhysRegReused;
656 const MRegisterInfo *MRI = Spills.getRegInfo();
657 if (MRI->areAliases(PRRU, PhysReg)) {
658 // Okay, we found out that an alias of a reused register
659 // was used. This isn't good because it means we have
660 // to undo a previous reuse.
661 MachineBasicBlock *MBB = MI->getParent();
662 const TargetRegisterClass *AliasRC =
663 MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
665 // Copy Op out of the vector and remove it, we're going to insert an
666 // explicit load for it.
668 Reuses.erase(Reuses.begin()+ro);
670 // Ok, we're going to try to reload the assigned physreg into the
671 // slot that we were supposed to in the first place. However, that
672 // register could hold a reuse. Check to see if it conflicts or
673 // would prefer us to use a different register.
674 unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
675 MI, Spills, MaybeDeadStores,
676 Rejected, RegKills, KillOps, VRM);
678 if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) {
679 MRI->reMaterialize(*MBB, MI, NewPhysReg,
680 VRM.getReMaterializedMI(NewOp.VirtReg));
683 MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg,
684 NewOp.StackSlotOrReMat, AliasRC);
685 // Any stores to this stack slot are not dead anymore.
686 MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL;
689 Spills.ClobberPhysReg(NewPhysReg);
690 Spills.ClobberPhysReg(NewOp.PhysRegReused);
692 MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
694 Spills.addAvailable(NewOp.StackSlotOrReMat, MI, NewPhysReg);
695 MachineBasicBlock::iterator MII = MI;
697 UpdateKills(*MII, RegKills, KillOps);
698 DOUT << '\t' << *MII;
700 DOUT << "Reuse undone!\n";
703 // Finally, PhysReg is now available, go ahead and use it.
711 /// GetRegForReload - Helper for the above GetRegForReload(). Add a
712 /// 'Rejected' set to remember which registers have been considered and
713 /// rejected for the reload. This avoids infinite looping in case like
716 /// t2 <- assigned r0 for use by the reload but ended up reuse r1
717 /// t3 <- assigned r1 for use by the reload but ended up reuse r0
719 /// sees r1 is taken by t2, tries t2's reload register r0
720 /// sees r0 is taken by t3, tries t3's reload register r1
721 /// sees r1 is taken by t2, tries t2's reload register r0 ...
722 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
723 AvailableSpills &Spills,
724 std::vector<MachineInstr*> &MaybeDeadStores,
726 std::vector<MachineOperand*> &KillOps,
728 SmallSet<unsigned, 8> Rejected;
729 return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected,
730 RegKills, KillOps, VRM);
735 /// PrepForUnfoldOpti - Turn a store folding instruction into a load folding
736 /// instruction. e.g.
738 /// movl %eax, -32(%ebp)
739 /// movl -36(%ebp), %eax
740 /// orl %eax, -32(%ebp)
743 /// orl -36(%ebp), %eax
744 /// mov %eax, -32(%ebp)
745 /// This enables unfolding optimization for a subsequent instruction which will
746 /// also eliminate the newly introduced store instruction.
747 bool LocalSpiller::PrepForUnfoldOpti(MachineBasicBlock &MBB,
748 MachineBasicBlock::iterator &MII,
749 std::vector<MachineInstr*> &MaybeDeadStores,
750 AvailableSpills &Spills,
752 std::vector<MachineOperand*> &KillOps,
754 MachineFunction &MF = *MBB.getParent();
755 MachineInstr &MI = *MII;
756 unsigned UnfoldedOpc = 0;
757 unsigned UnfoldPR = 0;
758 unsigned UnfoldVR = 0;
759 int FoldedSS = VirtRegMap::NO_STACK_SLOT;
760 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
761 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
762 // Only transform a MI that folds a single register.
765 UnfoldVR = I->second.first;
766 VirtRegMap::ModRef MR = I->second.second;
767 if (VRM.isAssignedReg(UnfoldVR))
769 // If this reference is not a use, any previous store is now dead.
770 // Otherwise, the store to this stack slot is not dead anymore.
771 FoldedSS = VRM.getStackSlot(UnfoldVR);
772 MachineInstr* DeadStore = MaybeDeadStores[FoldedSS];
773 if (DeadStore && (MR & VirtRegMap::isModRef)) {
774 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(FoldedSS);
776 DeadStore->findRegisterUseOperandIdx(PhysReg, true) == -1)
779 UnfoldedOpc = MRI->getOpcodeAfterMemoryUnfold(MI.getOpcode(),
787 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
788 MachineOperand &MO = MI.getOperand(i);
789 if (!MO.isRegister() || MO.getReg() == 0 || !MO.isUse())
791 unsigned VirtReg = MO.getReg();
792 if (MRegisterInfo::isPhysicalRegister(VirtReg) || MO.getSubReg())
794 if (VRM.isAssignedReg(VirtReg)) {
795 unsigned PhysReg = VRM.getPhys(VirtReg);
796 if (PhysReg && MRI->regsOverlap(PhysReg, UnfoldPR))
798 } else if (VRM.isReMaterialized(VirtReg))
800 int SS = VRM.getStackSlot(VirtReg);
801 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
803 if (MRI->regsOverlap(PhysReg, UnfoldPR))
807 PhysReg = VRM.getPhys(VirtReg);
808 if (!MRI->regsOverlap(PhysReg, UnfoldPR))
811 // Ok, we'll need to reload the value into a register which makes
812 // it impossible to perform the store unfolding optimization later.
813 // Let's see if it is possible to fold the load if the store is
814 // unfolded. This allows us to perform the store unfolding
816 SmallVector<MachineInstr*, 4> NewMIs;
817 if (MRI->unfoldMemoryOperand(MF, &MI, UnfoldVR, false, false, NewMIs)) {
818 assert(NewMIs.size() == 1);
819 MachineInstr *NewMI = NewMIs.back();
821 int Idx = NewMI->findRegisterUseOperandIdx(VirtReg);
823 SmallVector<unsigned, 2> Ops;
825 MachineInstr *FoldedMI = MRI->foldMemoryOperand(NewMI, Ops, SS);
827 if (!VRM.hasPhys(UnfoldVR))
828 VRM.assignVirt2Phys(UnfoldVR, UnfoldPR);
829 VRM.virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef);
830 MII = MBB.insert(MII, FoldedMI);
831 VRM.RemoveMachineInstrFromMaps(&MI);
841 /// findSuperReg - Find the SubReg's super-register of given register class
842 /// where its SubIdx sub-register is SubReg.
843 static unsigned findSuperReg(const TargetRegisterClass *RC, unsigned SubReg,
844 unsigned SubIdx, const MRegisterInfo *MRI) {
845 for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
848 if (MRI->getSubReg(Reg, SubIdx) == SubReg)
854 /// SpillRegToStackSlot - Spill a register to a specified stack slot. Check if
855 /// the last store to the same slot is now dead. If so, remove the last store.
856 void LocalSpiller::SpillRegToStackSlot(MachineBasicBlock &MBB,
857 MachineBasicBlock::iterator &MII,
858 int Idx, unsigned PhysReg, int StackSlot,
859 const TargetRegisterClass *RC,
860 bool isAvailable, MachineInstr *&LastStore,
861 AvailableSpills &Spills,
862 SmallSet<MachineInstr*, 4> &ReMatDefs,
864 std::vector<MachineOperand*> &KillOps,
866 MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, true, StackSlot, RC);
867 DOUT << "Store:\t" << *next(MII);
869 // If there is a dead store to this stack slot, nuke it now.
871 DOUT << "Removed dead store:\t" << *LastStore;
873 SmallVector<unsigned, 2> KillRegs;
874 InvalidateKills(*LastStore, RegKills, KillOps, &KillRegs);
875 MachineBasicBlock::iterator PrevMII = LastStore;
876 bool CheckDef = PrevMII != MBB.begin();
879 MBB.erase(LastStore);
880 VRM.RemoveMachineInstrFromMaps(LastStore);
882 // Look at defs of killed registers on the store. Mark the defs
883 // as dead since the store has been deleted and they aren't
885 for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
886 bool HasOtherDef = false;
887 if (InvalidateRegDef(PrevMII, *MII, KillRegs[j], HasOtherDef)) {
888 MachineInstr *DeadDef = PrevMII;
889 if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
890 // FIXME: This assumes a remat def does not have side
893 VRM.RemoveMachineInstrFromMaps(DeadDef);
901 LastStore = next(MII);
903 // If the stack slot value was previously available in some other
904 // register, change it now. Otherwise, make the register available,
906 Spills.ModifyStackSlotOrReMat(StackSlot);
907 Spills.ClobberPhysReg(PhysReg);
908 Spills.addAvailable(StackSlot, LastStore, PhysReg, isAvailable);
912 /// rewriteMBB - Keep track of which spills are available even after the
913 /// register allocator is done with them. If possible, avid reloading vregs.
914 void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
915 DOUT << MBB.getBasicBlock()->getName() << ":\n";
917 MachineFunction &MF = *MBB.getParent();
919 // Spills - Keep track of which spilled values are available in physregs so
920 // that we can choose to reuse the physregs instead of emitting reloads.
921 AvailableSpills Spills(MRI, TII);
923 // MaybeDeadStores - When we need to write a value back into a stack slot,
924 // keep track of the inserted store. If the stack slot value is never read
925 // (because the value was used from some available register, for example), and
926 // subsequently stored to, the original store is dead. This map keeps track
927 // of inserted stores that are not used. If we see a subsequent store to the
928 // same stack slot, the original store is deleted.
929 std::vector<MachineInstr*> MaybeDeadStores;
930 MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL);
932 // ReMatDefs - These are rematerializable def MIs which are not deleted.
933 SmallSet<MachineInstr*, 4> ReMatDefs;
935 // Keep track of kill information.
936 BitVector RegKills(MRI->getNumRegs());
937 std::vector<MachineOperand*> KillOps;
938 KillOps.resize(MRI->getNumRegs(), NULL);
940 for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
942 MachineBasicBlock::iterator NextMII = MII; ++NextMII;
944 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
946 bool BackTracked = false;
947 if (PrepForUnfoldOpti(MBB, MII,
948 MaybeDeadStores, Spills, RegKills, KillOps, VRM))
951 MachineInstr &MI = *MII;
952 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
954 // Insert restores here if asked to.
955 if (VRM.isRestorePt(&MI)) {
956 std::vector<unsigned> &RestoreRegs = VRM.getRestorePtRestores(&MI);
957 for (unsigned i = 0, e = RestoreRegs.size(); i != e; ++i) {
958 unsigned VirtReg = RestoreRegs[i];
959 if (!VRM.getPreSplitReg(VirtReg))
960 continue; // Split interval spilled again.
961 unsigned Phys = VRM.getPhys(VirtReg);
962 MF.setPhysRegUsed(Phys);
963 if (VRM.isReMaterialized(VirtReg)) {
964 MRI->reMaterialize(MBB, &MI, Phys,
965 VRM.getReMaterializedMI(VirtReg));
968 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
969 MRI->loadRegFromStackSlot(MBB, &MI, Phys, VRM.getStackSlot(VirtReg), RC);
972 // This invalidates Phys.
973 Spills.ClobberPhysReg(Phys);
974 UpdateKills(*prior(MII), RegKills, KillOps);
975 DOUT << '\t' << *prior(MII);
979 // Insert spills here if asked to.
980 if (VRM.isSpillPt(&MI)) {
981 std::vector<std::pair<unsigned,bool> > &SpillRegs =
982 VRM.getSpillPtSpills(&MI);
983 for (unsigned i = 0, e = SpillRegs.size(); i != e; ++i) {
984 unsigned VirtReg = SpillRegs[i].first;
985 bool isKill = SpillRegs[i].second;
986 if (!VRM.getPreSplitReg(VirtReg))
987 continue; // Split interval spilled again.
988 const TargetRegisterClass *RC = RegMap->getRegClass(VirtReg);
989 unsigned Phys = VRM.getPhys(VirtReg);
990 int StackSlot = VRM.getStackSlot(VirtReg);
991 MRI->storeRegToStackSlot(MBB, next(MII), Phys, isKill, StackSlot, RC);
992 MachineInstr *StoreMI = next(MII);
993 DOUT << "Store:\t" << StoreMI;
994 VRM.virtFolded(VirtReg, StoreMI, VirtRegMap::isMod);
999 /// ReusedOperands - Keep track of operand reuse in case we need to undo
1001 ReuseInfo ReusedOperands(MI, MRI);
1002 // Process all of the spilled uses and all non spilled reg references.
1003 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
1004 MachineOperand &MO = MI.getOperand(i);
1005 if (!MO.isRegister() || MO.getReg() == 0)
1006 continue; // Ignore non-register operands.
1008 unsigned VirtReg = MO.getReg();
1009 if (MRegisterInfo::isPhysicalRegister(VirtReg)) {
1010 // Ignore physregs for spilling, but remember that it is used by this
1012 MF.setPhysRegUsed(VirtReg);
1016 assert(MRegisterInfo::isVirtualRegister(VirtReg) &&
1017 "Not a virtual or a physical register?");
1019 unsigned SubIdx = MO.getSubReg();
1020 if (VRM.isAssignedReg(VirtReg)) {
1021 // This virtual register was assigned a physreg!
1022 unsigned Phys = VRM.getPhys(VirtReg);
1023 MF.setPhysRegUsed(Phys);
1025 ReusedOperands.markClobbered(Phys);
1026 unsigned RReg = SubIdx ? MRI->getSubReg(Phys, SubIdx) : Phys;
1027 MI.getOperand(i).setReg(RReg);
1031 // This virtual register is now known to be a spilled value.
1033 continue; // Handle defs in the loop below (handle use&def here though)
1035 bool DoReMat = VRM.isReMaterialized(VirtReg);
1036 int SSorRMId = DoReMat
1037 ? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
1038 int ReuseSlot = SSorRMId;
1040 // Check to see if this stack slot is available.
1041 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
1043 // If this is a sub-register use, make sure the reuse register is in the
1044 // right register class. For example, for x86 not all of the 32-bit
1045 // registers have accessible sub-registers.
1046 // Similarly so for EXTRACT_SUBREG. Consider this:
1048 // MOV32_mr fi#1, EDI
1050 // = EXTRACT_SUBREG fi#1
1051 // fi#1 is available in EDI, but it cannot be reused because it's not in
1052 // the right register file.
1054 (SubIdx || MI.getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)) {
1055 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
1056 if (!RC->contains(PhysReg))
1061 // This spilled operand might be part of a two-address operand. If this
1062 // is the case, then changing it will necessarily require changing the
1063 // def part of the instruction as well. However, in some cases, we
1064 // aren't allowed to modify the reused register. If none of these cases
1066 bool CanReuse = true;
1067 int ti = TID->getOperandConstraint(i, TOI::TIED_TO);
1069 MI.getOperand(ti).isRegister() &&
1070 MI.getOperand(ti).getReg() == VirtReg) {
1071 // Okay, we have a two address operand. We can reuse this physreg as
1072 // long as we are allowed to clobber the value and there isn't an
1073 // earlier def that has already clobbered the physreg.
1074 CanReuse = Spills.canClobberPhysReg(ReuseSlot) &&
1075 !ReusedOperands.isClobbered(PhysReg);
1079 // If this stack slot value is already available, reuse it!
1080 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
1081 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
1083 DOUT << "Reusing SS#" << ReuseSlot;
1084 DOUT << " from physreg "
1085 << MRI->getName(PhysReg) << " for vreg"
1086 << VirtReg <<" instead of reloading into physreg "
1087 << MRI->getName(VRM.getPhys(VirtReg)) << "\n";
1088 unsigned RReg = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
1089 MI.getOperand(i).setReg(RReg);
1091 // The only technical detail we have is that we don't know that
1092 // PhysReg won't be clobbered by a reloaded stack slot that occurs
1093 // later in the instruction. In particular, consider 'op V1, V2'.
1094 // If V1 is available in physreg R0, we would choose to reuse it
1095 // here, instead of reloading it into the register the allocator
1096 // indicated (say R1). However, V2 might have to be reloaded
1097 // later, and it might indicate that it needs to live in R0. When
1098 // this occurs, we need to have information available that
1099 // indicates it is safe to use R1 for the reload instead of R0.
1101 // To further complicate matters, we might conflict with an alias,
1102 // or R0 and R1 might not be compatible with each other. In this
1103 // case, we actually insert a reload for V1 in R1, ensuring that
1104 // we can get at R0 or its alias.
1105 ReusedOperands.addReuse(i, ReuseSlot, PhysReg,
1106 VRM.getPhys(VirtReg), VirtReg);
1108 // Only mark it clobbered if this is a use&def operand.
1109 ReusedOperands.markClobbered(PhysReg);
1112 if (MI.getOperand(i).isKill() &&
1113 ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) {
1114 // This was the last use and the spilled value is still available
1115 // for reuse. That means the spill was unnecessary!
1116 MachineInstr* DeadStore = MaybeDeadStores[ReuseSlot];
1118 DOUT << "Removed dead store:\t" << *DeadStore;
1119 InvalidateKills(*DeadStore, RegKills, KillOps);
1120 VRM.RemoveMachineInstrFromMaps(DeadStore);
1121 MBB.erase(DeadStore);
1122 MaybeDeadStores[ReuseSlot] = NULL;
1129 // Otherwise we have a situation where we have a two-address instruction
1130 // whose mod/ref operand needs to be reloaded. This reload is already
1131 // available in some register "PhysReg", but if we used PhysReg as the
1132 // operand to our 2-addr instruction, the instruction would modify
1133 // PhysReg. This isn't cool if something later uses PhysReg and expects
1134 // to get its initial value.
1136 // To avoid this problem, and to avoid doing a load right after a store,
1137 // we emit a copy from PhysReg into the designated register for this
1139 unsigned DesignatedReg = VRM.getPhys(VirtReg);
1140 assert(DesignatedReg && "Must map virtreg to physreg!");
1142 // Note that, if we reused a register for a previous operand, the
1143 // register we want to reload into might not actually be
1144 // available. If this occurs, use the register indicated by the
1146 if (ReusedOperands.hasReuses())
1147 DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
1148 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
1150 // If the mapped designated register is actually the physreg we have
1151 // incoming, we don't need to inserted a dead copy.
1152 if (DesignatedReg == PhysReg) {
1153 // If this stack slot value is already available, reuse it!
1154 if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
1155 DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
1157 DOUT << "Reusing SS#" << ReuseSlot;
1158 DOUT << " from physreg " << MRI->getName(PhysReg) << " for vreg"
1160 << " instead of reloading into same physreg.\n";
1161 unsigned RReg = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
1162 MI.getOperand(i).setReg(RReg);
1163 ReusedOperands.markClobbered(RReg);
1168 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
1169 MF.setPhysRegUsed(DesignatedReg);
1170 ReusedOperands.markClobbered(DesignatedReg);
1171 MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC, RC);
1173 MachineInstr *CopyMI = prior(MII);
1174 UpdateKills(*CopyMI, RegKills, KillOps);
1176 // This invalidates DesignatedReg.
1177 Spills.ClobberPhysReg(DesignatedReg);
1179 Spills.addAvailable(ReuseSlot, &MI, DesignatedReg);
1181 SubIdx ? MRI->getSubReg(DesignatedReg, SubIdx) : DesignatedReg;
1182 MI.getOperand(i).setReg(RReg);
1183 DOUT << '\t' << *prior(MII);
1188 // Otherwise, reload it and remember that we have it.
1189 PhysReg = VRM.getPhys(VirtReg);
1190 assert(PhysReg && "Must map virtreg to physreg!");
1192 // Note that, if we reused a register for a previous operand, the
1193 // register we want to reload into might not actually be
1194 // available. If this occurs, use the register indicated by the
1196 if (ReusedOperands.hasReuses())
1197 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
1198 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
1200 MF.setPhysRegUsed(PhysReg);
1201 ReusedOperands.markClobbered(PhysReg);
1203 MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg));
1206 const TargetRegisterClass* RC = RegMap->getRegClass(VirtReg);
1207 MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, SSorRMId, RC);
1210 // This invalidates PhysReg.
1211 Spills.ClobberPhysReg(PhysReg);
1213 // Any stores to this stack slot are not dead anymore.
1215 MaybeDeadStores[SSorRMId] = NULL;
1216 Spills.addAvailable(SSorRMId, &MI, PhysReg);
1217 // Assumes this is the last use. IsKill will be unset if reg is reused
1218 // unless it's a two-address operand.
1219 if (TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
1220 MI.getOperand(i).setIsKill();
1221 unsigned RReg = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
1222 MI.getOperand(i).setReg(RReg);
1223 UpdateKills(*prior(MII), RegKills, KillOps);
1224 DOUT << '\t' << *prior(MII);
1230 // If we have folded references to memory operands, make sure we clear all
1231 // physical registers that may contain the value of the spilled virtual
1233 SmallSet<int, 2> FoldedSS;
1234 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
1235 unsigned VirtReg = I->second.first;
1236 VirtRegMap::ModRef MR = I->second.second;
1237 DOUT << "Folded vreg: " << VirtReg << " MR: " << MR;
1239 int SS = VRM.getStackSlot(VirtReg);
1240 if (SS == VirtRegMap::NO_STACK_SLOT)
1242 FoldedSS.insert(SS);
1243 DOUT << " - StackSlot: " << SS << "\n";
1245 // If this folded instruction is just a use, check to see if it's a
1246 // straight load from the virt reg slot.
1247 if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
1249 unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx);
1250 if (DestReg && FrameIdx == SS) {
1251 // If this spill slot is available, turn it into a copy (or nothing)
1252 // instead of leaving it as a load!
1253 if (unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SS)) {
1254 DOUT << "Promoted Load To Copy: " << MI;
1255 if (DestReg != InReg) {
1256 const TargetRegisterClass *RC = RegMap->getRegClass(VirtReg);
1257 MRI->copyRegToReg(MBB, &MI, DestReg, InReg, RC, RC);
1258 // Revisit the copy so we make sure to notice the effects of the
1259 // operation on the destreg (either needing to RA it if it's
1260 // virtual or needing to clobber any values if it's physical).
1262 --NextMII; // backtrack to the copy.
1265 DOUT << "Removing now-noop copy: " << MI;
1267 VRM.RemoveMachineInstrFromMaps(&MI);
1270 goto ProcessNextInst;
1273 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
1274 SmallVector<MachineInstr*, 4> NewMIs;
1276 MRI->unfoldMemoryOperand(MF, &MI, PhysReg, false, false, NewMIs)) {
1277 MBB.insert(MII, NewMIs[0]);
1278 VRM.RemoveMachineInstrFromMaps(&MI);
1281 --NextMII; // backtrack to the unfolded instruction.
1283 goto ProcessNextInst;
1288 // If this reference is not a use, any previous store is now dead.
1289 // Otherwise, the store to this stack slot is not dead anymore.
1290 MachineInstr* DeadStore = MaybeDeadStores[SS];
1292 bool isDead = !(MR & VirtRegMap::isRef);
1293 MachineInstr *NewStore = NULL;
1294 if (MR & VirtRegMap::isModRef) {
1295 unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
1296 SmallVector<MachineInstr*, 4> NewMIs;
1297 // We can reuse this physreg as long as we are allowed to clobber
1298 // the value and there isn't an earlier def that has already clobbered the
1301 DeadStore->findRegisterUseOperandIdx(PhysReg, true) != -1 &&
1302 MRI->unfoldMemoryOperand(MF, &MI, PhysReg, false, true, NewMIs)) {
1303 MBB.insert(MII, NewMIs[0]);
1304 NewStore = NewMIs[1];
1305 MBB.insert(MII, NewStore);
1306 VRM.RemoveMachineInstrFromMaps(&MI);
1310 --NextMII; // backtrack to the unfolded instruction.
1316 if (isDead) { // Previous store is dead.
1317 // If we get here, the store is dead, nuke it now.
1318 DOUT << "Removed dead store:\t" << *DeadStore;
1319 InvalidateKills(*DeadStore, RegKills, KillOps);
1320 VRM.RemoveMachineInstrFromMaps(DeadStore);
1321 MBB.erase(DeadStore);
1326 MaybeDeadStores[SS] = NULL;
1328 // Treat this store as a spill merged into a copy. That makes the
1329 // stack slot value available.
1330 VRM.virtFolded(VirtReg, NewStore, VirtRegMap::isMod);
1331 goto ProcessNextInst;
1335 // If the spill slot value is available, and this is a new definition of
1336 // the value, the value is not available anymore.
1337 if (MR & VirtRegMap::isMod) {
1338 // Notice that the value in this stack slot has been modified.
1339 Spills.ModifyStackSlotOrReMat(SS);
1341 // If this is *just* a mod of the value, check to see if this is just a
1342 // store to the spill slot (i.e. the spill got merged into the copy). If
1343 // so, realize that the vreg is available now, and add the store to the
1344 // MaybeDeadStore info.
1346 if (!(MR & VirtRegMap::isRef)) {
1347 if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
1348 assert(MRegisterInfo::isPhysicalRegister(SrcReg) &&
1349 "Src hasn't been allocated yet?");
1350 // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
1351 // this as a potentially dead store in case there is a subsequent
1352 // store into the stack slot without a read from it.
1353 MaybeDeadStores[StackSlot] = &MI;
1355 // If the stack slot value was previously available in some other
1356 // register, change it now. Otherwise, make the register available,
1358 Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/);
1364 // Process all of the spilled defs.
1365 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
1366 MachineOperand &MO = MI.getOperand(i);
1367 if (!(MO.isRegister() && MO.getReg() && MO.isDef()))
1370 unsigned VirtReg = MO.getReg();
1371 if (!MRegisterInfo::isVirtualRegister(VirtReg)) {
1372 // Check to see if this is a noop copy. If so, eliminate the
1373 // instruction before considering the dest reg to be changed.
1375 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1377 DOUT << "Removing now-noop copy: " << MI;
1380 VRM.RemoveMachineInstrFromMaps(&MI);
1381 Spills.disallowClobberPhysReg(VirtReg);
1382 goto ProcessNextInst;
1385 // If it's not a no-op copy, it clobbers the value in the destreg.
1386 Spills.ClobberPhysReg(VirtReg);
1387 ReusedOperands.markClobbered(VirtReg);
1389 // Check to see if this instruction is a load from a stack slot into
1390 // a register. If so, this provides the stack slot value in the reg.
1392 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
1393 assert(DestReg == VirtReg && "Unknown load situation!");
1395 // If it is a folded reference, then it's not safe to clobber.
1396 bool Folded = FoldedSS.count(FrameIdx);
1397 // Otherwise, if it wasn't available, remember that it is now!
1398 Spills.addAvailable(FrameIdx, &MI, DestReg, !Folded);
1399 goto ProcessNextInst;
1405 unsigned SubIdx = MO.getSubReg();
1406 bool DoReMat = VRM.isReMaterialized(VirtReg);
1408 ReMatDefs.insert(&MI);
1410 // The only vregs left are stack slot definitions.
1411 int StackSlot = VRM.getStackSlot(VirtReg);
1412 const TargetRegisterClass *RC = RegMap->getRegClass(VirtReg);
1414 // If this def is part of a two-address operand, make sure to execute
1415 // the store from the correct physical register.
1417 int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i);
1419 PhysReg = MI.getOperand(TiedOp).getReg();
1421 unsigned SuperReg = findSuperReg(RC, PhysReg, SubIdx, MRI);
1422 assert(SuperReg && MRI->getSubReg(SuperReg, SubIdx) == PhysReg &&
1423 "Can't find corresponding super-register!");
1427 PhysReg = VRM.getPhys(VirtReg);
1428 if (ReusedOperands.isClobbered(PhysReg)) {
1429 // Another def has taken the assigned physreg. It must have been a
1430 // use&def which got it due to reuse. Undo the reuse!
1431 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
1432 Spills, MaybeDeadStores, RegKills, KillOps, VRM);
1436 MF.setPhysRegUsed(PhysReg);
1437 unsigned RReg = SubIdx ? MRI->getSubReg(PhysReg, SubIdx) : PhysReg;
1438 ReusedOperands.markClobbered(RReg);
1439 MI.getOperand(i).setReg(RReg);
1442 MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
1443 SpillRegToStackSlot(MBB, MII, -1, PhysReg, StackSlot, RC, true,
1444 LastStore, Spills, ReMatDefs, RegKills, KillOps, VRM);
1445 NextMII = next(MII);
1447 // Check to see if this is a noop copy. If so, eliminate the
1448 // instruction before considering the dest reg to be changed.
1451 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
1453 DOUT << "Removing now-noop copy: " << MI;
1456 VRM.RemoveMachineInstrFromMaps(&MI);
1457 UpdateKills(*LastStore, RegKills, KillOps);
1458 goto ProcessNextInst;
1464 if (!Erased && !BackTracked) {
1465 for (MachineBasicBlock::iterator II = MI; II != NextMII; ++II)
1466 UpdateKills(*II, RegKills, KillOps);
1472 llvm::Spiller* llvm::createSpiller() {
1473 switch (SpillerOpt) {
1474 default: assert(0 && "Unreachable!");
1476 return new LocalSpiller();
1478 return new SimpleSpiller();