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/Statistic.h"
31 #include "llvm/ADT/STLExtras.h"
32 #include "llvm/ADT/SmallSet.h"
36 STATISTIC(NumSpills, "Number of register spills");
37 STATISTIC(NumStores, "Number of stores added");
38 STATISTIC(NumLoads , "Number of loads added");
39 STATISTIC(NumReused, "Number of values reused");
40 STATISTIC(NumDSE , "Number of dead stores elided");
41 STATISTIC(NumDCE , "Number of copies elided");
44 enum SpillerName { simple, local };
46 static cl::opt<SpillerName>
48 cl::desc("Spiller to use: (default: local)"),
50 cl::values(clEnumVal(simple, " simple spiller"),
51 clEnumVal(local, " local spiller"),
56 //===----------------------------------------------------------------------===//
57 // VirtRegMap implementation
58 //===----------------------------------------------------------------------===//
60 VirtRegMap::VirtRegMap(MachineFunction &mf)
61 : TII(*mf.getTarget().getInstrInfo()), MF(mf),
62 Virt2PhysMap(NO_PHYS_REG), Virt2StackSlotMap(NO_STACK_SLOT) {
66 void VirtRegMap::grow() {
67 Virt2PhysMap.grow(MF.getSSARegMap()->getLastVirtReg());
68 Virt2StackSlotMap.grow(MF.getSSARegMap()->getLastVirtReg());
71 int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
72 assert(MRegisterInfo::isVirtualRegister(virtReg));
73 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
74 "attempt to assign stack slot to already spilled register");
75 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(virtReg);
76 int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
78 Virt2StackSlotMap[virtReg] = frameIndex;
83 void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) {
84 assert(MRegisterInfo::isVirtualRegister(virtReg));
85 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
86 "attempt to assign stack slot to already spilled register");
87 Virt2StackSlotMap[virtReg] = frameIndex;
90 void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
91 unsigned OpNo, MachineInstr *NewMI) {
92 // Move previous memory references folded to new instruction.
93 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
94 for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
95 E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
96 MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
97 MI2VirtMap.erase(I++);
101 const TargetInstrDescriptor *TID = OldMI->getInstrDescriptor();
102 if (TID->getOperandConstraint(OpNo, TOI::TIED_TO) != -1 ||
103 TID->findTiedToSrcOperand(OpNo) != -1) {
104 // Folded a two-address operand.
106 } else if (OldMI->getOperand(OpNo).isDef()) {
112 // add new memory reference
113 MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
116 void VirtRegMap::print(std::ostream &OS) const {
117 const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
119 OS << "********** REGISTER MAP **********\n";
120 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
121 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) {
122 if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG)
123 OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n";
127 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
128 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i)
129 if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT)
130 OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n";
134 void VirtRegMap::dump() const {
139 //===----------------------------------------------------------------------===//
140 // Simple Spiller Implementation
141 //===----------------------------------------------------------------------===//
143 Spiller::~Spiller() {}
146 struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller {
147 bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM);
151 bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
152 DOUT << "********** REWRITE MACHINE CODE **********\n";
153 DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
154 const TargetMachine &TM = MF.getTarget();
155 const MRegisterInfo &MRI = *TM.getRegisterInfo();
156 bool *PhysRegsUsed = MF.getUsedPhysregs();
158 // LoadedRegs - Keep track of which vregs are loaded, so that we only load
159 // each vreg once (in the case where a spilled vreg is used by multiple
160 // operands). This is always smaller than the number of operands to the
161 // current machine instr, so it should be small.
162 std::vector<unsigned> LoadedRegs;
164 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
166 DOUT << MBBI->getBasicBlock()->getName() << ":\n";
167 MachineBasicBlock &MBB = *MBBI;
168 for (MachineBasicBlock::iterator MII = MBB.begin(),
169 E = MBB.end(); MII != E; ++MII) {
170 MachineInstr &MI = *MII;
171 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
172 MachineOperand &MO = MI.getOperand(i);
173 if (MO.isRegister() && MO.getReg())
174 if (MRegisterInfo::isVirtualRegister(MO.getReg())) {
175 unsigned VirtReg = MO.getReg();
176 unsigned PhysReg = VRM.getPhys(VirtReg);
177 if (VRM.hasStackSlot(VirtReg)) {
178 int StackSlot = VRM.getStackSlot(VirtReg);
179 const TargetRegisterClass* RC =
180 MF.getSSARegMap()->getRegClass(VirtReg);
183 std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
184 == LoadedRegs.end()) {
185 MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
186 LoadedRegs.push_back(VirtReg);
188 DOUT << '\t' << *prior(MII);
192 MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
196 PhysRegsUsed[PhysReg] = true;
197 MI.getOperand(i).setReg(PhysReg);
199 PhysRegsUsed[MO.getReg()] = true;
210 //===----------------------------------------------------------------------===//
211 // Local Spiller Implementation
212 //===----------------------------------------------------------------------===//
215 /// LocalSpiller - This spiller does a simple pass over the machine basic
216 /// block to attempt to keep spills in registers as much as possible for
217 /// blocks that have low register pressure (the vreg may be spilled due to
218 /// register pressure in other blocks).
219 class VISIBILITY_HIDDEN LocalSpiller : public Spiller {
220 const MRegisterInfo *MRI;
221 const TargetInstrInfo *TII;
223 bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
224 MRI = MF.getTarget().getRegisterInfo();
225 TII = MF.getTarget().getInstrInfo();
226 DOUT << "\n**** Local spiller rewriting function '"
227 << MF.getFunction()->getName() << "':\n";
229 for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
231 RewriteMBB(*MBB, VRM);
235 void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
236 void ClobberPhysReg(unsigned PR, std::map<int, unsigned> &SpillSlots,
237 std::multimap<unsigned, int> &PhysRegs);
238 void ClobberPhysRegOnly(unsigned PR, std::map<int, unsigned> &SpillSlots,
239 std::multimap<unsigned, int> &PhysRegs);
240 void ModifyStackSlot(int Slot, std::map<int, unsigned> &SpillSlots,
241 std::multimap<unsigned, int> &PhysRegs);
245 /// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
246 /// top down, keep track of which spills slots are available in each register.
248 /// Note that not all physregs are created equal here. In particular, some
249 /// physregs are reloads that we are allowed to clobber or ignore at any time.
250 /// Other physregs are values that the register allocated program is using that
251 /// we cannot CHANGE, but we can read if we like. We keep track of this on a
252 /// per-stack-slot basis as the low bit in the value of the SpillSlotsAvailable
253 /// entries. The predicate 'canClobberPhysReg()' checks this bit and
254 /// addAvailable sets it if.
256 class VISIBILITY_HIDDEN AvailableSpills {
257 const MRegisterInfo *MRI;
258 const TargetInstrInfo *TII;
260 // SpillSlotsAvailable - This map keeps track of all of the spilled virtual
261 // register values that are still available, due to being loaded or stored to,
262 // but not invalidated yet.
263 std::map<int, unsigned> SpillSlotsAvailable;
265 // PhysRegsAvailable - This is the inverse of SpillSlotsAvailable, indicating
266 // which stack slot values are currently held by a physreg. This is used to
267 // invalidate entries in SpillSlotsAvailable when a physreg is modified.
268 std::multimap<unsigned, int> PhysRegsAvailable;
270 void disallowClobberPhysRegOnly(unsigned PhysReg);
272 void ClobberPhysRegOnly(unsigned PhysReg);
274 AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
275 : MRI(mri), TII(tii) {
278 /// getSpillSlotPhysReg - If the specified stack slot is available in a
279 /// physical register, return that PhysReg, otherwise return 0.
280 unsigned getSpillSlotPhysReg(int Slot) const {
281 std::map<int, unsigned>::const_iterator I = SpillSlotsAvailable.find(Slot);
282 if (I != SpillSlotsAvailable.end())
283 return I->second >> 1; // Remove the CanClobber bit.
287 const MRegisterInfo *getRegInfo() const { return MRI; }
289 /// addAvailable - Mark that the specified stack slot is available in the
290 /// specified physreg. If CanClobber is true, the physreg can be modified at
291 /// any time without changing the semantics of the program.
292 void addAvailable(int Slot, unsigned Reg, bool CanClobber = true) {
293 // If this stack slot is thought to be available in some other physreg,
294 // remove its record.
295 ModifyStackSlot(Slot);
297 PhysRegsAvailable.insert(std::make_pair(Reg, Slot));
298 SpillSlotsAvailable[Slot] = (Reg << 1) | (unsigned)CanClobber;
300 DOUT << "Remembering SS#" << Slot << " in physreg "
301 << MRI->getName(Reg) << "\n";
304 /// canClobberPhysReg - Return true if the spiller is allowed to change the
305 /// value of the specified stackslot register if it desires. The specified
306 /// stack slot must be available in a physreg for this query to make sense.
307 bool canClobberPhysReg(int Slot) const {
308 assert(SpillSlotsAvailable.count(Slot) && "Slot not available!");
309 return SpillSlotsAvailable.find(Slot)->second & 1;
312 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
313 /// stackslot register. The register is still available but is no longer
314 /// allowed to be modifed.
315 void disallowClobberPhysReg(unsigned PhysReg);
317 /// ClobberPhysReg - This is called when the specified physreg changes
318 /// value. We use this to invalidate any info about stuff we thing lives in
319 /// it and any of its aliases.
320 void ClobberPhysReg(unsigned PhysReg);
322 /// ModifyStackSlot - This method is called when the value in a stack slot
323 /// changes. This removes information about which register the previous value
324 /// for this slot lives in (as the previous value is dead now).
325 void ModifyStackSlot(int Slot);
329 /// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
330 /// stackslot register. The register is still available but is no longer
331 /// allowed to be modifed.
332 void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
333 std::multimap<unsigned, int>::iterator I =
334 PhysRegsAvailable.lower_bound(PhysReg);
335 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
336 int Slot = I->second;
338 assert((SpillSlotsAvailable[Slot] >> 1) == PhysReg &&
339 "Bidirectional map mismatch!");
340 SpillSlotsAvailable[Slot] &= ~1;
341 DOUT << "PhysReg " << MRI->getName(PhysReg)
342 << " copied, it is available for use but can no longer be modified\n";
346 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified
347 /// stackslot register and its aliases. The register and its aliases may
348 /// still available but is no longer allowed to be modifed.
349 void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
350 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
351 disallowClobberPhysRegOnly(*AS);
352 disallowClobberPhysRegOnly(PhysReg);
355 /// ClobberPhysRegOnly - This is called when the specified physreg changes
356 /// value. We use this to invalidate any info about stuff we thing lives in it.
357 void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
358 std::multimap<unsigned, int>::iterator I =
359 PhysRegsAvailable.lower_bound(PhysReg);
360 while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
361 int Slot = I->second;
362 PhysRegsAvailable.erase(I++);
363 assert((SpillSlotsAvailable[Slot] >> 1) == PhysReg &&
364 "Bidirectional map mismatch!");
365 SpillSlotsAvailable.erase(Slot);
366 DOUT << "PhysReg " << MRI->getName(PhysReg)
367 << " clobbered, invalidating SS#" << Slot << "\n";
371 /// ClobberPhysReg - This is called when the specified physreg changes
372 /// value. We use this to invalidate any info about stuff we thing lives in
373 /// it and any of its aliases.
374 void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
375 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
376 ClobberPhysRegOnly(*AS);
377 ClobberPhysRegOnly(PhysReg);
380 /// ModifyStackSlot - This method is called when the value in a stack slot
381 /// changes. This removes information about which register the previous value
382 /// for this slot lives in (as the previous value is dead now).
383 void AvailableSpills::ModifyStackSlot(int Slot) {
384 std::map<int, unsigned>::iterator It = SpillSlotsAvailable.find(Slot);
385 if (It == SpillSlotsAvailable.end()) return;
386 unsigned Reg = It->second >> 1;
387 SpillSlotsAvailable.erase(It);
389 // This register may hold the value of multiple stack slots, only remove this
390 // stack slot from the set of values the register contains.
391 std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
393 assert(I != PhysRegsAvailable.end() && I->first == Reg &&
394 "Map inverse broken!");
395 if (I->second == Slot) break;
397 PhysRegsAvailable.erase(I);
402 // ReusedOp - For each reused operand, we keep track of a bit of information, in
403 // case we need to rollback upon processing a new operand. See comments below.
406 // The MachineInstr operand that reused an available value.
409 // StackSlot - The spill slot of the value being reused.
412 // PhysRegReused - The physical register the value was available in.
413 unsigned PhysRegReused;
415 // AssignedPhysReg - The physreg that was assigned for use by the reload.
416 unsigned AssignedPhysReg;
418 // VirtReg - The virtual register itself.
421 ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
423 : Operand(o), StackSlot(ss), PhysRegReused(prr), AssignedPhysReg(apr),
427 /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
428 /// is reused instead of reloaded.
429 class VISIBILITY_HIDDEN ReuseInfo {
431 std::vector<ReusedOp> Reuses;
432 bool *PhysRegsClobbered;
434 ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
435 PhysRegsClobbered = new bool[mri->getNumRegs()];
436 std::fill(PhysRegsClobbered, PhysRegsClobbered+mri->getNumRegs(), false);
439 delete[] PhysRegsClobbered;
442 bool hasReuses() const {
443 return !Reuses.empty();
446 /// addReuse - If we choose to reuse a virtual register that is already
447 /// available instead of reloading it, remember that we did so.
448 void addReuse(unsigned OpNo, unsigned StackSlot,
449 unsigned PhysRegReused, unsigned AssignedPhysReg,
451 // If the reload is to the assigned register anyway, no undo will be
453 if (PhysRegReused == AssignedPhysReg) return;
455 // Otherwise, remember this.
456 Reuses.push_back(ReusedOp(OpNo, StackSlot, PhysRegReused,
457 AssignedPhysReg, VirtReg));
460 void markClobbered(unsigned PhysReg) {
461 PhysRegsClobbered[PhysReg] = true;
464 bool isClobbered(unsigned PhysReg) const {
465 return PhysRegsClobbered[PhysReg];
468 /// GetRegForReload - We are about to emit a reload into PhysReg. If there
469 /// is some other operand that is using the specified register, either pick
470 /// a new register to use, or evict the previous reload and use this reg.
471 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
472 AvailableSpills &Spills,
473 std::map<int, MachineInstr*> &MaybeDeadStores,
474 SmallSet<unsigned, 8> &Rejected) {
475 if (Reuses.empty()) return PhysReg; // This is most often empty.
477 for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
478 ReusedOp &Op = Reuses[ro];
479 // If we find some other reuse that was supposed to use this register
480 // exactly for its reload, we can change this reload to use ITS reload
481 // register. That is, unless its reload register has already been
482 // considered and subsequently rejected because it has also been reused
483 // by another operand.
484 if (Op.PhysRegReused == PhysReg &&
485 Rejected.count(Op.AssignedPhysReg) == 0) {
486 // Yup, use the reload register that we didn't use before.
487 unsigned NewReg = Op.AssignedPhysReg;
488 Rejected.insert(PhysReg);
489 return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected);
491 // Otherwise, we might also have a problem if a previously reused
492 // value aliases the new register. If so, codegen the previous reload
494 unsigned PRRU = Op.PhysRegReused;
495 const MRegisterInfo *MRI = Spills.getRegInfo();
496 if (MRI->areAliases(PRRU, PhysReg)) {
497 // Okay, we found out that an alias of a reused register
498 // was used. This isn't good because it means we have
499 // to undo a previous reuse.
500 MachineBasicBlock *MBB = MI->getParent();
501 const TargetRegisterClass *AliasRC =
502 MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg);
504 // Copy Op out of the vector and remove it, we're going to insert an
505 // explicit load for it.
507 Reuses.erase(Reuses.begin()+ro);
509 // Ok, we're going to try to reload the assigned physreg into the
510 // slot that we were supposed to in the first place. However, that
511 // register could hold a reuse. Check to see if it conflicts or
512 // would prefer us to use a different register.
513 unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
514 MI, Spills, MaybeDeadStores, Rejected);
516 MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg,
517 NewOp.StackSlot, AliasRC);
518 Spills.ClobberPhysReg(NewPhysReg);
519 Spills.ClobberPhysReg(NewOp.PhysRegReused);
521 // Any stores to this stack slot are not dead anymore.
522 MaybeDeadStores.erase(NewOp.StackSlot);
524 MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
526 Spills.addAvailable(NewOp.StackSlot, NewPhysReg);
528 DEBUG(MachineBasicBlock::iterator MII = MI;
529 DOUT << '\t' << *prior(MII));
531 DOUT << "Reuse undone!\n";
534 // Finally, PhysReg is now available, go ahead and use it.
542 /// GetRegForReload - Helper for the above GetRegForReload(). Add a
543 /// 'Rejected' set to remember which registers have been considered and
544 /// rejected for the reload. This avoids infinite looping in case like
547 /// t2 <- assigned r0 for use by the reload but ended up reuse r1
548 /// t3 <- assigned r1 for use by the reload but ended up reuse r0
550 /// sees r1 is taken by t2, tries t2's reload register r0
551 /// sees r0 is taken by t3, tries t3's reload register r1
552 /// sees r1 is taken by t2, tries t2's reload register r0 ...
553 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
554 AvailableSpills &Spills,
555 std::map<int, MachineInstr*> &MaybeDeadStores) {
556 SmallSet<unsigned, 8> Rejected;
557 return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected);
563 /// rewriteMBB - Keep track of which spills are available even after the
564 /// register allocator is done with them. If possible, avoid reloading vregs.
565 void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
567 DOUT << MBB.getBasicBlock()->getName() << ":\n";
569 // Spills - Keep track of which spilled values are available in physregs so
570 // that we can choose to reuse the physregs instead of emitting reloads.
571 AvailableSpills Spills(MRI, TII);
573 // MaybeDeadStores - When we need to write a value back into a stack slot,
574 // keep track of the inserted store. If the stack slot value is never read
575 // (because the value was used from some available register, for example), and
576 // subsequently stored to, the original store is dead. This map keeps track
577 // of inserted stores that are not used. If we see a subsequent store to the
578 // same stack slot, the original store is deleted.
579 std::map<int, MachineInstr*> MaybeDeadStores;
581 bool *PhysRegsUsed = MBB.getParent()->getUsedPhysregs();
583 for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
585 MachineInstr &MI = *MII;
586 MachineBasicBlock::iterator NextMII = MII; ++NextMII;
588 /// ReusedOperands - Keep track of operand reuse in case we need to undo
590 ReuseInfo ReusedOperands(MI, MRI);
592 // Loop over all of the implicit defs, clearing them from our available
594 const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
595 const unsigned *ImpDef = TID->ImplicitDefs;
597 for ( ; *ImpDef; ++ImpDef) {
598 PhysRegsUsed[*ImpDef] = true;
599 ReusedOperands.markClobbered(*ImpDef);
600 Spills.ClobberPhysReg(*ImpDef);
604 // Process all of the spilled uses and all non spilled reg references.
605 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
606 MachineOperand &MO = MI.getOperand(i);
607 if (!MO.isRegister() || MO.getReg() == 0)
608 continue; // Ignore non-register operands.
610 if (MRegisterInfo::isPhysicalRegister(MO.getReg())) {
611 // Ignore physregs for spilling, but remember that it is used by this
613 PhysRegsUsed[MO.getReg()] = true;
614 ReusedOperands.markClobbered(MO.getReg());
618 assert(MRegisterInfo::isVirtualRegister(MO.getReg()) &&
619 "Not a virtual or a physical register?");
621 unsigned VirtReg = MO.getReg();
622 if (!VRM.hasStackSlot(VirtReg)) {
623 // This virtual register was assigned a physreg!
624 unsigned Phys = VRM.getPhys(VirtReg);
625 PhysRegsUsed[Phys] = true;
627 ReusedOperands.markClobbered(Phys);
628 MI.getOperand(i).setReg(Phys);
632 // This virtual register is now known to be a spilled value.
634 continue; // Handle defs in the loop below (handle use&def here though)
636 int StackSlot = VRM.getStackSlot(VirtReg);
639 // Check to see if this stack slot is available.
640 if ((PhysReg = Spills.getSpillSlotPhysReg(StackSlot))) {
642 // This spilled operand might be part of a two-address operand. If this
643 // is the case, then changing it will necessarily require changing the
644 // def part of the instruction as well. However, in some cases, we
645 // aren't allowed to modify the reused register. If none of these cases
647 bool CanReuse = true;
648 int ti = TID->getOperandConstraint(i, TOI::TIED_TO);
650 MI.getOperand(ti).isReg() &&
651 MI.getOperand(ti).getReg() == VirtReg) {
652 // Okay, we have a two address operand. We can reuse this physreg as
653 // long as we are allowed to clobber the value and there isn't an
654 // earlier def that has already clobbered the physreg.
655 CanReuse = Spills.canClobberPhysReg(StackSlot) &&
656 !ReusedOperands.isClobbered(PhysReg);
660 // If this stack slot value is already available, reuse it!
661 DOUT << "Reusing SS#" << StackSlot << " from physreg "
662 << MRI->getName(PhysReg) << " for vreg"
663 << VirtReg <<" instead of reloading into physreg "
664 << MRI->getName(VRM.getPhys(VirtReg)) << "\n";
665 MI.getOperand(i).setReg(PhysReg);
667 // The only technical detail we have is that we don't know that
668 // PhysReg won't be clobbered by a reloaded stack slot that occurs
669 // later in the instruction. In particular, consider 'op V1, V2'.
670 // If V1 is available in physreg R0, we would choose to reuse it
671 // here, instead of reloading it into the register the allocator
672 // indicated (say R1). However, V2 might have to be reloaded
673 // later, and it might indicate that it needs to live in R0. When
674 // this occurs, we need to have information available that
675 // indicates it is safe to use R1 for the reload instead of R0.
677 // To further complicate matters, we might conflict with an alias,
678 // or R0 and R1 might not be compatible with each other. In this
679 // case, we actually insert a reload for V1 in R1, ensuring that
680 // we can get at R0 or its alias.
681 ReusedOperands.addReuse(i, StackSlot, PhysReg,
682 VRM.getPhys(VirtReg), VirtReg);
684 // Only mark it clobbered if this is a use&def operand.
685 ReusedOperands.markClobbered(PhysReg);
690 // Otherwise we have a situation where we have a two-address instruction
691 // whose mod/ref operand needs to be reloaded. This reload is already
692 // available in some register "PhysReg", but if we used PhysReg as the
693 // operand to our 2-addr instruction, the instruction would modify
694 // PhysReg. This isn't cool if something later uses PhysReg and expects
695 // to get its initial value.
697 // To avoid this problem, and to avoid doing a load right after a store,
698 // we emit a copy from PhysReg into the designated register for this
700 unsigned DesignatedReg = VRM.getPhys(VirtReg);
701 assert(DesignatedReg && "Must map virtreg to physreg!");
703 // Note that, if we reused a register for a previous operand, the
704 // register we want to reload into might not actually be
705 // available. If this occurs, use the register indicated by the
707 if (ReusedOperands.hasReuses())
708 DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
709 Spills, MaybeDeadStores);
711 // If the mapped designated register is actually the physreg we have
712 // incoming, we don't need to inserted a dead copy.
713 if (DesignatedReg == PhysReg) {
714 // If this stack slot value is already available, reuse it!
715 DOUT << "Reusing SS#" << StackSlot << " from physreg "
716 << MRI->getName(PhysReg) << " for vreg"
718 << " instead of reloading into same physreg.\n";
719 MI.getOperand(i).setReg(PhysReg);
720 ReusedOperands.markClobbered(PhysReg);
725 const TargetRegisterClass* RC =
726 MBB.getParent()->getSSARegMap()->getRegClass(VirtReg);
728 PhysRegsUsed[DesignatedReg] = true;
729 ReusedOperands.markClobbered(DesignatedReg);
730 MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC);
732 // This invalidates DesignatedReg.
733 Spills.ClobberPhysReg(DesignatedReg);
735 Spills.addAvailable(StackSlot, DesignatedReg);
736 MI.getOperand(i).setReg(DesignatedReg);
737 DOUT << '\t' << *prior(MII);
742 // Otherwise, reload it and remember that we have it.
743 PhysReg = VRM.getPhys(VirtReg);
744 assert(PhysReg && "Must map virtreg to physreg!");
745 const TargetRegisterClass* RC =
746 MBB.getParent()->getSSARegMap()->getRegClass(VirtReg);
748 // Note that, if we reused a register for a previous operand, the
749 // register we want to reload into might not actually be
750 // available. If this occurs, use the register indicated by the
752 if (ReusedOperands.hasReuses())
753 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
754 Spills, MaybeDeadStores);
756 PhysRegsUsed[PhysReg] = true;
757 ReusedOperands.markClobbered(PhysReg);
758 MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
759 // This invalidates PhysReg.
760 Spills.ClobberPhysReg(PhysReg);
762 // Any stores to this stack slot are not dead anymore.
763 MaybeDeadStores.erase(StackSlot);
764 Spills.addAvailable(StackSlot, PhysReg);
766 MI.getOperand(i).setReg(PhysReg);
767 DOUT << '\t' << *prior(MII);
772 // If we have folded references to memory operands, make sure we clear all
773 // physical registers that may contain the value of the spilled virtual
775 VirtRegMap::MI2VirtMapTy::const_iterator I, End;
776 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
777 DOUT << "Folded vreg: " << I->second.first << " MR: "
779 unsigned VirtReg = I->second.first;
780 VirtRegMap::ModRef MR = I->second.second;
781 if (!VRM.hasStackSlot(VirtReg)) {
782 DOUT << ": No stack slot!\n";
785 int SS = VRM.getStackSlot(VirtReg);
786 DOUT << " - StackSlot: " << SS << "\n";
788 // If this folded instruction is just a use, check to see if it's a
789 // straight load from the virt reg slot.
790 if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
792 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
793 if (FrameIdx == SS) {
794 // If this spill slot is available, turn it into a copy (or nothing)
795 // instead of leaving it as a load!
796 if (unsigned InReg = Spills.getSpillSlotPhysReg(SS)) {
797 DOUT << "Promoted Load To Copy: " << MI;
798 MachineFunction &MF = *MBB.getParent();
799 if (DestReg != InReg) {
800 MRI->copyRegToReg(MBB, &MI, DestReg, InReg,
801 MF.getSSARegMap()->getRegClass(VirtReg));
802 // Revisit the copy so we make sure to notice the effects of the
803 // operation on the destreg (either needing to RA it if it's
804 // virtual or needing to clobber any values if it's physical).
806 --NextMII; // backtrack to the copy.
808 VRM.RemoveFromFoldedVirtMap(&MI);
810 goto ProcessNextInst;
816 // If this reference is not a use, any previous store is now dead.
817 // Otherwise, the store to this stack slot is not dead anymore.
818 std::map<int, MachineInstr*>::iterator MDSI = MaybeDeadStores.find(SS);
819 if (MDSI != MaybeDeadStores.end()) {
820 if (MR & VirtRegMap::isRef) // Previous store is not dead.
821 MaybeDeadStores.erase(MDSI);
823 // If we get here, the store is dead, nuke it now.
824 assert(VirtRegMap::isMod && "Can't be modref!");
825 DOUT << "Removed dead store:\t" << *MDSI->second;
826 MBB.erase(MDSI->second);
827 VRM.RemoveFromFoldedVirtMap(MDSI->second);
828 MaybeDeadStores.erase(MDSI);
833 // If the spill slot value is available, and this is a new definition of
834 // the value, the value is not available anymore.
835 if (MR & VirtRegMap::isMod) {
836 // Notice that the value in this stack slot has been modified.
837 Spills.ModifyStackSlot(SS);
839 // If this is *just* a mod of the value, check to see if this is just a
840 // store to the spill slot (i.e. the spill got merged into the copy). If
841 // so, realize that the vreg is available now, and add the store to the
842 // MaybeDeadStore info.
844 if (!(MR & VirtRegMap::isRef)) {
845 if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
846 assert(MRegisterInfo::isPhysicalRegister(SrcReg) &&
847 "Src hasn't been allocated yet?");
848 // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
849 // this as a potentially dead store in case there is a subsequent
850 // store into the stack slot without a read from it.
851 MaybeDeadStores[StackSlot] = &MI;
853 // If the stack slot value was previously available in some other
854 // register, change it now. Otherwise, make the register available,
856 Spills.addAvailable(StackSlot, SrcReg, false /*don't clobber*/);
862 // Process all of the spilled defs.
863 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
864 MachineOperand &MO = MI.getOperand(i);
865 if (MO.isRegister() && MO.getReg() && MO.isDef()) {
866 unsigned VirtReg = MO.getReg();
868 if (!MRegisterInfo::isVirtualRegister(VirtReg)) {
869 // Check to see if this is a noop copy. If so, eliminate the
870 // instruction before considering the dest reg to be changed.
872 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
874 DOUT << "Removing now-noop copy: " << MI;
876 VRM.RemoveFromFoldedVirtMap(&MI);
877 Spills.disallowClobberPhysReg(VirtReg);
878 goto ProcessNextInst;
881 // If it's not a no-op copy, it clobbers the value in the destreg.
882 Spills.ClobberPhysReg(VirtReg);
883 ReusedOperands.markClobbered(VirtReg);
885 // Check to see if this instruction is a load from a stack slot into
886 // a register. If so, this provides the stack slot value in the reg.
888 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
889 assert(DestReg == VirtReg && "Unknown load situation!");
891 // Otherwise, if it wasn't available, remember that it is now!
892 Spills.addAvailable(FrameIdx, DestReg);
893 goto ProcessNextInst;
899 // The only vregs left are stack slot definitions.
900 int StackSlot = VRM.getStackSlot(VirtReg);
901 const TargetRegisterClass *RC =
902 MBB.getParent()->getSSARegMap()->getRegClass(VirtReg);
904 // If this def is part of a two-address operand, make sure to execute
905 // the store from the correct physical register.
907 int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i);
909 PhysReg = MI.getOperand(TiedOp).getReg();
911 PhysReg = VRM.getPhys(VirtReg);
912 if (ReusedOperands.isClobbered(PhysReg)) {
913 // Another def has taken the assigned physreg. It must have been a
914 // use&def which got it due to reuse. Undo the reuse!
915 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
916 Spills, MaybeDeadStores);
920 PhysRegsUsed[PhysReg] = true;
921 ReusedOperands.markClobbered(PhysReg);
922 MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
923 DOUT << "Store:\t" << *next(MII);
924 MI.getOperand(i).setReg(PhysReg);
926 // Check to see if this is a noop copy. If so, eliminate the
927 // instruction before considering the dest reg to be changed.
930 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
932 DOUT << "Removing now-noop copy: " << MI;
934 VRM.RemoveFromFoldedVirtMap(&MI);
935 goto ProcessNextInst;
939 // If there is a dead store to this stack slot, nuke it now.
940 MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
942 DOUT << "Removed dead store:\t" << *LastStore;
944 MBB.erase(LastStore);
945 VRM.RemoveFromFoldedVirtMap(LastStore);
947 LastStore = next(MII);
949 // If the stack slot value was previously available in some other
950 // register, change it now. Otherwise, make the register available,
952 Spills.ModifyStackSlot(StackSlot);
953 Spills.ClobberPhysReg(PhysReg);
954 Spills.addAvailable(StackSlot, PhysReg);
965 llvm::Spiller* llvm::createSpiller() {
966 switch (SpillerOpt) {
967 default: assert(0 && "Unreachable!");
969 return new LocalSpiller();
971 return new SimpleSpiller();