VirtRegMap.cpp revision ad7ccf34b5de14bd2b9ddc8072d14582a2ce29d9
1//===-- llvm/CodeGen/VirtRegMap.cpp - Virtual Register Map ----------------===// 2// 3// The LLVM Compiler Infrastructure 4// 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. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the VirtRegMap class. 11// 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 15// code as necessary. 16// 17//===----------------------------------------------------------------------===// 18 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" 34#include <algorithm> 35using namespace llvm; 36 37STATISTIC(NumSpills, "Number of register spills"); 38STATISTIC(NumReMats, "Number of re-materialization"); 39STATISTIC(NumStores, "Number of stores added"); 40STATISTIC(NumLoads , "Number of loads added"); 41STATISTIC(NumReused, "Number of values reused"); 42STATISTIC(NumDSE , "Number of dead stores elided"); 43STATISTIC(NumDCE , "Number of copies elided"); 44 45namespace { 46 enum SpillerName { simple, local }; 47 48 static cl::opt<SpillerName> 49 SpillerOpt("spiller", 50 cl::desc("Spiller to use: (default: local)"), 51 cl::Prefix, 52 cl::values(clEnumVal(simple, " simple spiller"), 53 clEnumVal(local, " local spiller"), 54 clEnumValEnd), 55 cl::init(local)); 56} 57 58//===----------------------------------------------------------------------===// 59// VirtRegMap implementation 60//===----------------------------------------------------------------------===// 61 62VirtRegMap::VirtRegMap(MachineFunction &mf) 63 : TII(*mf.getTarget().getInstrInfo()), MF(mf), 64 Virt2PhysMap(NO_PHYS_REG), Virt2StackSlotMap(NO_STACK_SLOT), 65 ReMatId(MAX_STACK_SLOT+1) { 66 grow(); 67} 68 69void VirtRegMap::grow() { 70 Virt2PhysMap.grow(MF.getSSARegMap()->getLastVirtReg()); 71 Virt2StackSlotMap.grow(MF.getSSARegMap()->getLastVirtReg()); 72} 73 74int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) { 75 assert(MRegisterInfo::isVirtualRegister(virtReg)); 76 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT && 77 "attempt to assign stack slot to already spilled register"); 78 const TargetRegisterClass* RC = MF.getSSARegMap()->getRegClass(virtReg); 79 int frameIndex = MF.getFrameInfo()->CreateStackObject(RC->getSize(), 80 RC->getAlignment()); 81 Virt2StackSlotMap[virtReg] = frameIndex; 82 ++NumSpills; 83 return frameIndex; 84} 85 86void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int frameIndex) { 87 assert(MRegisterInfo::isVirtualRegister(virtReg)); 88 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT && 89 "attempt to assign stack slot to already spilled register"); 90 Virt2StackSlotMap[virtReg] = frameIndex; 91} 92 93int VirtRegMap::assignVirtReMatId(unsigned virtReg) { 94 assert(MRegisterInfo::isVirtualRegister(virtReg)); 95 assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT && 96 "attempt to assign re-mat id to already spilled register"); 97 Virt2StackSlotMap[virtReg] = ReMatId; 98 ++NumReMats; 99 return ReMatId++; 100} 101 102void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI, 103 unsigned OpNo, MachineInstr *NewMI) { 104 // Move previous memory references folded to new instruction. 105 MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI); 106 for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI), 107 E = MI2VirtMap.end(); I != E && I->first == OldMI; ) { 108 MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second)); 109 MI2VirtMap.erase(I++); 110 } 111 112 ModRef MRInfo; 113 const TargetInstrDescriptor *TID = OldMI->getInstrDescriptor(); 114 if (TID->getOperandConstraint(OpNo, TOI::TIED_TO) != -1 || 115 TID->findTiedToSrcOperand(OpNo) != -1) { 116 // Folded a two-address operand. 117 MRInfo = isModRef; 118 } else if (OldMI->getOperand(OpNo).isDef()) { 119 MRInfo = isMod; 120 } else { 121 MRInfo = isRef; 122 } 123 124 // add new memory reference 125 MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo))); 126} 127 128void VirtRegMap::print(std::ostream &OS) const { 129 const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo(); 130 131 OS << "********** REGISTER MAP **********\n"; 132 for (unsigned i = MRegisterInfo::FirstVirtualRegister, 133 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) { 134 if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG) 135 OS << "[reg" << i << " -> " << MRI->getName(Virt2PhysMap[i]) << "]\n"; 136 137 } 138 139 for (unsigned i = MRegisterInfo::FirstVirtualRegister, 140 e = MF.getSSARegMap()->getLastVirtReg(); i <= e; ++i) 141 if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT) 142 OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n"; 143 OS << '\n'; 144} 145 146void VirtRegMap::dump() const { 147 print(DOUT); 148} 149 150 151//===----------------------------------------------------------------------===// 152// Simple Spiller Implementation 153//===----------------------------------------------------------------------===// 154 155Spiller::~Spiller() {} 156 157namespace { 158 struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller { 159 bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM); 160 }; 161} 162 163bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) { 164 DOUT << "********** REWRITE MACHINE CODE **********\n"; 165 DOUT << "********** Function: " << MF.getFunction()->getName() << '\n'; 166 const TargetMachine &TM = MF.getTarget(); 167 const MRegisterInfo &MRI = *TM.getRegisterInfo(); 168 bool *PhysRegsUsed = MF.getUsedPhysregs(); 169 170 // LoadedRegs - Keep track of which vregs are loaded, so that we only load 171 // each vreg once (in the case where a spilled vreg is used by multiple 172 // operands). This is always smaller than the number of operands to the 173 // current machine instr, so it should be small. 174 std::vector<unsigned> LoadedRegs; 175 176 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end(); 177 MBBI != E; ++MBBI) { 178 DOUT << MBBI->getBasicBlock()->getName() << ":\n"; 179 MachineBasicBlock &MBB = *MBBI; 180 for (MachineBasicBlock::iterator MII = MBB.begin(), 181 E = MBB.end(); MII != E; ++MII) { 182 MachineInstr &MI = *MII; 183 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { 184 MachineOperand &MO = MI.getOperand(i); 185 if (MO.isRegister() && MO.getReg()) 186 if (MRegisterInfo::isVirtualRegister(MO.getReg())) { 187 unsigned VirtReg = MO.getReg(); 188 unsigned PhysReg = VRM.getPhys(VirtReg); 189 if (VRM.hasStackSlot(VirtReg)) { 190 int StackSlot = VRM.getStackSlot(VirtReg); 191 const TargetRegisterClass* RC = 192 MF.getSSARegMap()->getRegClass(VirtReg); 193 194 if (MO.isUse() && 195 std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg) 196 == LoadedRegs.end()) { 197 MRI.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC); 198 LoadedRegs.push_back(VirtReg); 199 ++NumLoads; 200 DOUT << '\t' << *prior(MII); 201 } 202 203 if (MO.isDef()) { 204 MRI.storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC); 205 ++NumStores; 206 } 207 } 208 PhysRegsUsed[PhysReg] = true; 209 MI.getOperand(i).setReg(PhysReg); 210 } else { 211 PhysRegsUsed[MO.getReg()] = true; 212 } 213 } 214 215 DOUT << '\t' << MI; 216 LoadedRegs.clear(); 217 } 218 } 219 return true; 220} 221 222//===----------------------------------------------------------------------===// 223// Local Spiller Implementation 224//===----------------------------------------------------------------------===// 225 226namespace { 227 /// LocalSpiller - This spiller does a simple pass over the machine basic 228 /// block to attempt to keep spills in registers as much as possible for 229 /// blocks that have low register pressure (the vreg may be spilled due to 230 /// register pressure in other blocks). 231 class VISIBILITY_HIDDEN LocalSpiller : public Spiller { 232 const MRegisterInfo *MRI; 233 const TargetInstrInfo *TII; 234 public: 235 bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) { 236 MRI = MF.getTarget().getRegisterInfo(); 237 TII = MF.getTarget().getInstrInfo(); 238 DOUT << "\n**** Local spiller rewriting function '" 239 << MF.getFunction()->getName() << "':\n"; 240 241 std::vector<MachineInstr *> ReMatedMIs; 242 for (MachineFunction::iterator MBB = MF.begin(), E = MF.end(); 243 MBB != E; ++MBB) 244 RewriteMBB(*MBB, VRM, ReMatedMIs); 245 for (unsigned i = 0, e = ReMatedMIs.size(); i != e; ++i) 246 delete ReMatedMIs[i]; 247 return true; 248 } 249 private: 250 void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM, 251 std::vector<MachineInstr*> &ReMatedMIs); 252 }; 253} 254 255/// AvailableSpills - As the local spiller is scanning and rewriting an MBB from 256/// top down, keep track of which spills slots are available in each register. 257/// 258/// Note that not all physregs are created equal here. In particular, some 259/// physregs are reloads that we are allowed to clobber or ignore at any time. 260/// Other physregs are values that the register allocated program is using that 261/// we cannot CHANGE, but we can read if we like. We keep track of this on a 262/// per-stack-slot basis as the low bit in the value of the SpillSlotsAvailable 263/// entries. The predicate 'canClobberPhysReg()' checks this bit and 264/// addAvailable sets it if. 265namespace { 266class VISIBILITY_HIDDEN AvailableSpills { 267 const MRegisterInfo *MRI; 268 const TargetInstrInfo *TII; 269 270 // SpillSlotsAvailable - This map keeps track of all of the spilled virtual 271 // register values that are still available, due to being loaded or stored to, 272 // but not invalidated yet. It also tracks the instructions that defined 273 // or used the register. 274 typedef std::pair<unsigned, std::vector<MachineInstr*> > SSInfo; 275 std::map<int, SSInfo> SpillSlotsAvailable; 276 277 // PhysRegsAvailable - This is the inverse of SpillSlotsAvailable, indicating 278 // which stack slot values are currently held by a physreg. This is used to 279 // invalidate entries in SpillSlotsAvailable when a physreg is modified. 280 std::multimap<unsigned, int> PhysRegsAvailable; 281 282 void disallowClobberPhysRegOnly(unsigned PhysReg); 283 284 void ClobberPhysRegOnly(unsigned PhysReg); 285public: 286 AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii) 287 : MRI(mri), TII(tii) { 288 } 289 290 const MRegisterInfo *getRegInfo() const { return MRI; } 291 292 /// getSpillSlotPhysReg - If the specified stack slot is available in a 293 /// physical register, return that PhysReg, otherwise return 0. It also 294 /// returns by reference the instruction that either defines or last uses 295 /// the register. 296 unsigned getSpillSlotPhysReg(int Slot, MachineInstr *&SSMI) const { 297 std::map<int, SSInfo>::const_iterator I = SpillSlotsAvailable.find(Slot); 298 if (I != SpillSlotsAvailable.end()) { 299 if (!I->second.second.empty()) 300 SSMI = I->second.second.back(); 301 return I->second.first >> 1; // Remove the CanClobber bit. 302 } 303 return 0; 304 } 305 306 /// addLastUse - Add the last use information of all stack slots whose 307 /// values are available in the specific register. 308 void addLastUse(unsigned PhysReg, MachineInstr *Use) { 309 std::multimap<unsigned, int>::iterator I = 310 PhysRegsAvailable.lower_bound(PhysReg); 311 while (I != PhysRegsAvailable.end() && I->first == PhysReg) { 312 int Slot = I->second; 313 I++; 314 315 std::map<int, SSInfo>::iterator II = SpillSlotsAvailable.find(Slot); 316 assert(II != SpillSlotsAvailable.end() && "Slot not available!"); 317 unsigned Val = II->second.first; 318 assert((Val >> 1) == PhysReg && "Bidirectional map mismatch!"); 319 II->second.second.push_back(Use); 320 } 321 } 322 323 /// removeLastUse - Remove the last use information of all stack slots whose 324 /// values are available in the specific register. 325 void removeLastUse(unsigned PhysReg, MachineInstr *Use) { 326 std::multimap<unsigned, int>::iterator I = 327 PhysRegsAvailable.lower_bound(PhysReg); 328 while (I != PhysRegsAvailable.end() && I->first == PhysReg) { 329 int Slot = I->second; 330 I++; 331 332 std::map<int, SSInfo>::iterator II = SpillSlotsAvailable.find(Slot); 333 assert(II != SpillSlotsAvailable.end() && "Slot not available!"); 334 unsigned Val = II->second.first; 335 assert((Val >> 1) == PhysReg && "Bidirectional map mismatch!"); 336 if (II->second.second.back() == Use) 337 II->second.second.pop_back(); 338 } 339 } 340 341 /// addAvailable - Mark that the specified stack slot is available in the 342 /// specified physreg. If CanClobber is true, the physreg can be modified at 343 /// any time without changing the semantics of the program. 344 void addAvailable(int Slot, MachineInstr *MI, unsigned Reg, 345 bool CanClobber = true) { 346 // If this stack slot is thought to be available in some other physreg, 347 // remove its record. 348 ModifyStackSlot(Slot); 349 350 PhysRegsAvailable.insert(std::make_pair(Reg, Slot)); 351 std::vector<MachineInstr*> DefUses; 352 DefUses.push_back(MI); 353 SpillSlotsAvailable[Slot] = 354 std::make_pair((Reg << 1) | (unsigned)CanClobber, DefUses); 355 356 if (Slot > VirtRegMap::MAX_STACK_SLOT) 357 DOUT << "Remembering RM#" << Slot-VirtRegMap::MAX_STACK_SLOT-1; 358 else 359 DOUT << "Remembering SS#" << Slot; 360 DOUT << " in physreg " << MRI->getName(Reg) << "\n"; 361 } 362 363 /// canClobberPhysReg - Return true if the spiller is allowed to change the 364 /// value of the specified stackslot register if it desires. The specified 365 /// stack slot must be available in a physreg for this query to make sense. 366 bool canClobberPhysReg(int Slot) const { 367 assert(SpillSlotsAvailable.count(Slot) && "Slot not available!"); 368 return SpillSlotsAvailable.find(Slot)->second.first & 1; 369 } 370 371 /// disallowClobberPhysReg - Unset the CanClobber bit of the specified 372 /// stackslot register. The register is still available but is no longer 373 /// allowed to be modifed. 374 void disallowClobberPhysReg(unsigned PhysReg); 375 376 /// ClobberPhysReg - This is called when the specified physreg changes 377 /// value. We use this to invalidate any info about stuff we thing lives in 378 /// it and any of its aliases. 379 void ClobberPhysReg(unsigned PhysReg); 380 381 /// ModifyStackSlot - This method is called when the value in a stack slot 382 /// changes. This removes information about which register the previous value 383 /// for this slot lives in (as the previous value is dead now). 384 void ModifyStackSlot(int Slot); 385}; 386} 387 388/// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified 389/// stackslot register. The register is still available but is no longer 390/// allowed to be modifed. 391void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) { 392 std::multimap<unsigned, int>::iterator I = 393 PhysRegsAvailable.lower_bound(PhysReg); 394 while (I != PhysRegsAvailable.end() && I->first == PhysReg) { 395 int Slot = I->second; 396 I++; 397 assert((SpillSlotsAvailable[Slot].first >> 1) == PhysReg && 398 "Bidirectional map mismatch!"); 399 SpillSlotsAvailable[Slot].first &= ~1; 400 DOUT << "PhysReg " << MRI->getName(PhysReg) 401 << " copied, it is available for use but can no longer be modified\n"; 402 } 403} 404 405/// disallowClobberPhysReg - Unset the CanClobber bit of the specified 406/// stackslot register and its aliases. The register and its aliases may 407/// still available but is no longer allowed to be modifed. 408void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) { 409 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS) 410 disallowClobberPhysRegOnly(*AS); 411 disallowClobberPhysRegOnly(PhysReg); 412} 413 414/// ClobberPhysRegOnly - This is called when the specified physreg changes 415/// value. We use this to invalidate any info about stuff we thing lives in it. 416void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) { 417 std::multimap<unsigned, int>::iterator I = 418 PhysRegsAvailable.lower_bound(PhysReg); 419 while (I != PhysRegsAvailable.end() && I->first == PhysReg) { 420 int Slot = I->second; 421 PhysRegsAvailable.erase(I++); 422 assert((SpillSlotsAvailable[Slot].first >> 1) == PhysReg && 423 "Bidirectional map mismatch!"); 424 SpillSlotsAvailable.erase(Slot); 425 DOUT << "PhysReg " << MRI->getName(PhysReg) 426 << " clobbered, invalidating "; 427 if (Slot > VirtRegMap::MAX_STACK_SLOT) 428 DOUT << "RM#" << Slot-VirtRegMap::MAX_STACK_SLOT-1 << "\n"; 429 else 430 DOUT << "SS#" << Slot << "\n"; 431 } 432} 433 434/// ClobberPhysReg - This is called when the specified physreg changes 435/// value. We use this to invalidate any info about stuff we thing lives in 436/// it and any of its aliases. 437void AvailableSpills::ClobberPhysReg(unsigned PhysReg) { 438 for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS) 439 ClobberPhysRegOnly(*AS); 440 ClobberPhysRegOnly(PhysReg); 441} 442 443/// ModifyStackSlot - This method is called when the value in a stack slot 444/// changes. This removes information about which register the previous value 445/// for this slot lives in (as the previous value is dead now). 446void AvailableSpills::ModifyStackSlot(int Slot) { 447 std::map<int, SSInfo>::iterator It = SpillSlotsAvailable.find(Slot); 448 if (It == SpillSlotsAvailable.end()) return; 449 unsigned Reg = It->second.first >> 1; 450 SpillSlotsAvailable.erase(It); 451 452 // This register may hold the value of multiple stack slots, only remove this 453 // stack slot from the set of values the register contains. 454 std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg); 455 for (; ; ++I) { 456 assert(I != PhysRegsAvailable.end() && I->first == Reg && 457 "Map inverse broken!"); 458 if (I->second == Slot) break; 459 } 460 PhysRegsAvailable.erase(I); 461} 462 463 464 465// ReusedOp - For each reused operand, we keep track of a bit of information, in 466// case we need to rollback upon processing a new operand. See comments below. 467namespace { 468 struct ReusedOp { 469 // The MachineInstr operand that reused an available value. 470 unsigned Operand; 471 472 // StackSlot - The spill slot of the value being reused. 473 unsigned StackSlot; 474 475 // PhysRegReused - The physical register the value was available in. 476 unsigned PhysRegReused; 477 478 // AssignedPhysReg - The physreg that was assigned for use by the reload. 479 unsigned AssignedPhysReg; 480 481 // VirtReg - The virtual register itself. 482 unsigned VirtReg; 483 484 ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr, 485 unsigned vreg) 486 : Operand(o), StackSlot(ss), PhysRegReused(prr), AssignedPhysReg(apr), 487 VirtReg(vreg) {} 488 }; 489 490 /// ReuseInfo - This maintains a collection of ReuseOp's for each operand that 491 /// is reused instead of reloaded. 492 class VISIBILITY_HIDDEN ReuseInfo { 493 MachineInstr &MI; 494 std::vector<ReusedOp> Reuses; 495 BitVector PhysRegsClobbered; 496 public: 497 ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) { 498 PhysRegsClobbered.resize(mri->getNumRegs()); 499 } 500 501 bool hasReuses() const { 502 return !Reuses.empty(); 503 } 504 505 /// addReuse - If we choose to reuse a virtual register that is already 506 /// available instead of reloading it, remember that we did so. 507 void addReuse(unsigned OpNo, unsigned StackSlot, 508 unsigned PhysRegReused, unsigned AssignedPhysReg, 509 unsigned VirtReg) { 510 // If the reload is to the assigned register anyway, no undo will be 511 // required. 512 if (PhysRegReused == AssignedPhysReg) return; 513 514 // Otherwise, remember this. 515 Reuses.push_back(ReusedOp(OpNo, StackSlot, PhysRegReused, 516 AssignedPhysReg, VirtReg)); 517 } 518 519 void markClobbered(unsigned PhysReg) { 520 PhysRegsClobbered.set(PhysReg); 521 } 522 523 bool isClobbered(unsigned PhysReg) const { 524 return PhysRegsClobbered.test(PhysReg); 525 } 526 527 /// GetRegForReload - We are about to emit a reload into PhysReg. If there 528 /// is some other operand that is using the specified register, either pick 529 /// a new register to use, or evict the previous reload and use this reg. 530 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI, 531 AvailableSpills &Spills, 532 std::map<int, MachineInstr*> &MaybeDeadStores, 533 SmallSet<unsigned, 8> &Rejected) { 534 if (Reuses.empty()) return PhysReg; // This is most often empty. 535 536 for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) { 537 ReusedOp &Op = Reuses[ro]; 538 // If we find some other reuse that was supposed to use this register 539 // exactly for its reload, we can change this reload to use ITS reload 540 // register. That is, unless its reload register has already been 541 // considered and subsequently rejected because it has also been reused 542 // by another operand. 543 if (Op.PhysRegReused == PhysReg && 544 Rejected.count(Op.AssignedPhysReg) == 0) { 545 // Yup, use the reload register that we didn't use before. 546 unsigned NewReg = Op.AssignedPhysReg; 547 Rejected.insert(PhysReg); 548 return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected); 549 } else { 550 // Otherwise, we might also have a problem if a previously reused 551 // value aliases the new register. If so, codegen the previous reload 552 // and use this one. 553 unsigned PRRU = Op.PhysRegReused; 554 const MRegisterInfo *MRI = Spills.getRegInfo(); 555 if (MRI->areAliases(PRRU, PhysReg)) { 556 // Okay, we found out that an alias of a reused register 557 // was used. This isn't good because it means we have 558 // to undo a previous reuse. 559 MachineBasicBlock *MBB = MI->getParent(); 560 const TargetRegisterClass *AliasRC = 561 MBB->getParent()->getSSARegMap()->getRegClass(Op.VirtReg); 562 563 // Copy Op out of the vector and remove it, we're going to insert an 564 // explicit load for it. 565 ReusedOp NewOp = Op; 566 Reuses.erase(Reuses.begin()+ro); 567 568 // Ok, we're going to try to reload the assigned physreg into the 569 // slot that we were supposed to in the first place. However, that 570 // register could hold a reuse. Check to see if it conflicts or 571 // would prefer us to use a different register. 572 unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg, 573 MI, Spills, MaybeDeadStores, Rejected); 574 575 MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg, 576 NewOp.StackSlot, AliasRC); 577 Spills.ClobberPhysReg(NewPhysReg); 578 Spills.ClobberPhysReg(NewOp.PhysRegReused); 579 580 // Any stores to this stack slot are not dead anymore. 581 MaybeDeadStores.erase(NewOp.StackSlot); 582 583 MI->getOperand(NewOp.Operand).setReg(NewPhysReg); 584 585 Spills.addAvailable(NewOp.StackSlot, MI, NewPhysReg); 586 ++NumLoads; 587 DEBUG(MachineBasicBlock::iterator MII = MI; 588 DOUT << '\t' << *prior(MII)); 589 590 DOUT << "Reuse undone!\n"; 591 --NumReused; 592 593 // Finally, PhysReg is now available, go ahead and use it. 594 return PhysReg; 595 } 596 } 597 } 598 return PhysReg; 599 } 600 601 /// GetRegForReload - Helper for the above GetRegForReload(). Add a 602 /// 'Rejected' set to remember which registers have been considered and 603 /// rejected for the reload. This avoids infinite looping in case like 604 /// this: 605 /// t1 := op t2, t3 606 /// t2 <- assigned r0 for use by the reload but ended up reuse r1 607 /// t3 <- assigned r1 for use by the reload but ended up reuse r0 608 /// t1 <- desires r1 609 /// sees r1 is taken by t2, tries t2's reload register r0 610 /// sees r0 is taken by t3, tries t3's reload register r1 611 /// sees r1 is taken by t2, tries t2's reload register r0 ... 612 unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI, 613 AvailableSpills &Spills, 614 std::map<int, MachineInstr*> &MaybeDeadStores) { 615 SmallSet<unsigned, 8> Rejected; 616 return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected); 617 } 618 }; 619} 620 621 622/// rewriteMBB - Keep track of which spills are available even after the 623/// register allocator is done with them. If possible, avoid reloading vregs. 624void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM, 625 std::vector<MachineInstr*> &ReMatedMIs) { 626 627 DOUT << MBB.getBasicBlock()->getName() << ":\n"; 628 629 // Spills - Keep track of which spilled values are available in physregs so 630 // that we can choose to reuse the physregs instead of emitting reloads. 631 AvailableSpills Spills(MRI, TII); 632 633 // MaybeDeadStores - When we need to write a value back into a stack slot, 634 // keep track of the inserted store. If the stack slot value is never read 635 // (because the value was used from some available register, for example), and 636 // subsequently stored to, the original store is dead. This map keeps track 637 // of inserted stores that are not used. If we see a subsequent store to the 638 // same stack slot, the original store is deleted. 639 std::map<int, MachineInstr*> MaybeDeadStores; 640 641 bool *PhysRegsUsed = MBB.getParent()->getUsedPhysregs(); 642 643 for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end(); 644 MII != E; ) { 645 MachineInstr &MI = *MII; 646 MachineBasicBlock::iterator NextMII = MII; ++NextMII; 647 648 /// ReusedOperands - Keep track of operand reuse in case we need to undo 649 /// reuse. 650 ReuseInfo ReusedOperands(MI, MRI); 651 652 // Loop over all of the implicit defs, clearing them from our available 653 // sets. 654 const TargetInstrDescriptor *TID = MI.getInstrDescriptor(); 655 656 // If this instruction is being rematerialized, just remove it! 657 if (TID->Flags & M_REMATERIALIZIBLE) { 658 bool Remove = true; 659 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { 660 MachineOperand &MO = MI.getOperand(i); 661 if (!MO.isRegister() || MO.getReg() == 0) 662 continue; // Ignore non-register operands. 663 if (MO.isDef() && !VRM.isReMaterialized(MO.getReg())) { 664 Remove = false; 665 break; 666 } 667 } 668 if (Remove) { 669 VRM.RemoveFromFoldedVirtMap(&MI); 670 ReMatedMIs.push_back(MI.removeFromParent()); 671 MII = NextMII; 672 continue; 673 } 674 } 675 676 const unsigned *ImpDef = TID->ImplicitDefs; 677 if (ImpDef) { 678 for ( ; *ImpDef; ++ImpDef) { 679 PhysRegsUsed[*ImpDef] = true; 680 ReusedOperands.markClobbered(*ImpDef); 681 Spills.ClobberPhysReg(*ImpDef); 682 } 683 } 684 685 // Process all of the spilled uses and all non spilled reg references. 686 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { 687 MachineOperand &MO = MI.getOperand(i); 688 if (!MO.isRegister() || MO.getReg() == 0) 689 continue; // Ignore non-register operands. 690 691 if (MRegisterInfo::isPhysicalRegister(MO.getReg())) { 692 // Ignore physregs for spilling, but remember that it is used by this 693 // function. 694 PhysRegsUsed[MO.getReg()] = true; 695 ReusedOperands.markClobbered(MO.getReg()); 696 continue; 697 } 698 699 assert(MRegisterInfo::isVirtualRegister(MO.getReg()) && 700 "Not a virtual or a physical register?"); 701 702 unsigned VirtReg = MO.getReg(); 703 if (!VRM.hasStackSlot(VirtReg)) { 704 // This virtual register was assigned a physreg! 705 unsigned Phys = VRM.getPhys(VirtReg); 706 PhysRegsUsed[Phys] = true; 707 if (MO.isDef()) 708 ReusedOperands.markClobbered(Phys); 709 MI.getOperand(i).setReg(Phys); 710 continue; 711 } 712 713 // This virtual register is now known to be a spilled value. 714 if (!MO.isUse()) 715 continue; // Handle defs in the loop below (handle use&def here though) 716 717 bool doReMat = VRM.isReMaterialized(VirtReg); 718 int StackSlot = VRM.getStackSlot(VirtReg); 719 unsigned PhysReg; 720 721 // Check to see if this stack slot is available. 722 MachineInstr *SSMI = NULL; 723 if ((PhysReg = Spills.getSpillSlotPhysReg(StackSlot, SSMI))) { 724 // This spilled operand might be part of a two-address operand. If this 725 // is the case, then changing it will necessarily require changing the 726 // def part of the instruction as well. However, in some cases, we 727 // aren't allowed to modify the reused register. If none of these cases 728 // apply, reuse it. 729 bool CanReuse = true; 730 int ti = TID->getOperandConstraint(i, TOI::TIED_TO); 731 if (ti != -1 && 732 MI.getOperand(ti).isReg() && 733 MI.getOperand(ti).getReg() == VirtReg) { 734 // Okay, we have a two address operand. We can reuse this physreg as 735 // long as we are allowed to clobber the value and there isn't an 736 // earlier def that has already clobbered the physreg. 737 CanReuse = Spills.canClobberPhysReg(StackSlot) && 738 !ReusedOperands.isClobbered(PhysReg); 739 } 740 741 if (CanReuse) { 742 // If this stack slot value is already available, reuse it! 743 if (StackSlot > VirtRegMap::MAX_STACK_SLOT) 744 DOUT << "Reusing RM#" << StackSlot-VirtRegMap::MAX_STACK_SLOT-1; 745 else 746 DOUT << "Reusing SS#" << StackSlot; 747 DOUT << " from physreg " 748 << MRI->getName(PhysReg) << " for vreg" 749 << VirtReg <<" instead of reloading into physreg " 750 << MRI->getName(VRM.getPhys(VirtReg)) << "\n"; 751 MI.getOperand(i).setReg(PhysReg); 752 753 // Extend the live range of the MI that last kill the register if 754 // necessary. 755 bool WasKill = false; 756 if (SSMI) { 757 int UIdx = SSMI->findRegisterUseOperand(PhysReg, true); 758 if (UIdx != -1) { 759 MachineOperand &MOK = SSMI->getOperand(UIdx); 760 WasKill = MOK.isKill(); 761 MOK.unsetIsKill(); 762 } 763 } 764 if (ti == -1) { 765 // Unless it's the use of a two-address code, transfer the kill 766 // of the reused register to this use. 767 if (WasKill) 768 MI.getOperand(i).setIsKill(); 769 Spills.addLastUse(PhysReg, &MI); 770 } 771 772 // The only technical detail we have is that we don't know that 773 // PhysReg won't be clobbered by a reloaded stack slot that occurs 774 // later in the instruction. In particular, consider 'op V1, V2'. 775 // If V1 is available in physreg R0, we would choose to reuse it 776 // here, instead of reloading it into the register the allocator 777 // indicated (say R1). However, V2 might have to be reloaded 778 // later, and it might indicate that it needs to live in R0. When 779 // this occurs, we need to have information available that 780 // indicates it is safe to use R1 for the reload instead of R0. 781 // 782 // To further complicate matters, we might conflict with an alias, 783 // or R0 and R1 might not be compatible with each other. In this 784 // case, we actually insert a reload for V1 in R1, ensuring that 785 // we can get at R0 or its alias. 786 ReusedOperands.addReuse(i, StackSlot, PhysReg, 787 VRM.getPhys(VirtReg), VirtReg); 788 if (ti != -1) 789 // Only mark it clobbered if this is a use&def operand. 790 ReusedOperands.markClobbered(PhysReg); 791 ++NumReused; 792 continue; 793 } 794 795 // Otherwise we have a situation where we have a two-address instruction 796 // whose mod/ref operand needs to be reloaded. This reload is already 797 // available in some register "PhysReg", but if we used PhysReg as the 798 // operand to our 2-addr instruction, the instruction would modify 799 // PhysReg. This isn't cool if something later uses PhysReg and expects 800 // to get its initial value. 801 // 802 // To avoid this problem, and to avoid doing a load right after a store, 803 // we emit a copy from PhysReg into the designated register for this 804 // operand. 805 unsigned DesignatedReg = VRM.getPhys(VirtReg); 806 assert(DesignatedReg && "Must map virtreg to physreg!"); 807 808 // Note that, if we reused a register for a previous operand, the 809 // register we want to reload into might not actually be 810 // available. If this occurs, use the register indicated by the 811 // reuser. 812 if (ReusedOperands.hasReuses()) 813 DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI, 814 Spills, MaybeDeadStores); 815 816 // If the mapped designated register is actually the physreg we have 817 // incoming, we don't need to inserted a dead copy. 818 if (DesignatedReg == PhysReg) { 819 // If this stack slot value is already available, reuse it! 820 if (StackSlot > VirtRegMap::MAX_STACK_SLOT) 821 DOUT << "Reusing RM#" << StackSlot-VirtRegMap::MAX_STACK_SLOT-1; 822 else 823 DOUT << "Reusing SS#" << StackSlot; 824 DOUT << " from physreg " << MRI->getName(PhysReg) << " for vreg" 825 << VirtReg 826 << " instead of reloading into same physreg.\n"; 827 MI.getOperand(i).setReg(PhysReg); 828 ReusedOperands.markClobbered(PhysReg); 829 ++NumReused; 830 continue; 831 } 832 833 const TargetRegisterClass* RC = 834 MBB.getParent()->getSSARegMap()->getRegClass(VirtReg); 835 836 PhysRegsUsed[DesignatedReg] = true; 837 ReusedOperands.markClobbered(DesignatedReg); 838 MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC); 839 840 // Extend the live range of the MI that last kill the register if 841 // necessary. 842 bool WasKill = false; 843 if (SSMI) { 844 int UIdx = SSMI->findRegisterUseOperand(PhysReg, true); 845 if (UIdx != -1) { 846 MachineOperand &MOK = SSMI->getOperand(UIdx); 847 WasKill = MOK.isKill(); 848 MOK.unsetIsKill(); 849 } 850 } 851 MachineInstr *CopyMI = prior(MII); 852 if (WasKill) { 853 // Transfer kill to the next use. 854 int UIdx = CopyMI->findRegisterUseOperand(PhysReg); 855 assert(UIdx != -1); 856 MachineOperand &MOU = CopyMI->getOperand(UIdx); 857 MOU.setIsKill(); 858 } 859 Spills.addLastUse(PhysReg, CopyMI); 860 861 // This invalidates DesignatedReg. 862 Spills.ClobberPhysReg(DesignatedReg); 863 864 Spills.addAvailable(StackSlot, &MI, DesignatedReg); 865 MI.getOperand(i).setReg(DesignatedReg); 866 DOUT << '\t' << *prior(MII); 867 ++NumReused; 868 continue; 869 } 870 871 // Otherwise, reload it and remember that we have it. 872 PhysReg = VRM.getPhys(VirtReg); 873 assert(PhysReg && "Must map virtreg to physreg!"); 874 const TargetRegisterClass* RC = 875 MBB.getParent()->getSSARegMap()->getRegClass(VirtReg); 876 877 // Note that, if we reused a register for a previous operand, the 878 // register we want to reload into might not actually be 879 // available. If this occurs, use the register indicated by the 880 // reuser. 881 if (ReusedOperands.hasReuses()) 882 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI, 883 Spills, MaybeDeadStores); 884 885 PhysRegsUsed[PhysReg] = true; 886 ReusedOperands.markClobbered(PhysReg); 887 if (doReMat) 888 MRI->reMaterialize(MBB, &MI, PhysReg, VRM.getReMaterializedMI(VirtReg)); 889 else 890 MRI->loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC); 891 // This invalidates PhysReg. 892 Spills.ClobberPhysReg(PhysReg); 893 894 // Any stores to this stack slot are not dead anymore. 895 if (!doReMat) 896 MaybeDeadStores.erase(StackSlot); 897 Spills.addAvailable(StackSlot, &MI, PhysReg); 898 // Assumes this is the last use. IsKill will be unset if reg is reused 899 // unless it's a two-address operand. 900 if (TID->getOperandConstraint(i, TOI::TIED_TO) == -1) 901 MI.getOperand(i).setIsKill(); 902 ++NumLoads; 903 MI.getOperand(i).setReg(PhysReg); 904 DOUT << '\t' << *prior(MII); 905 } 906 907 DOUT << '\t' << MI; 908 909 // If we have folded references to memory operands, make sure we clear all 910 // physical registers that may contain the value of the spilled virtual 911 // register 912 VirtRegMap::MI2VirtMapTy::const_iterator I, End; 913 for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) { 914 DOUT << "Folded vreg: " << I->second.first << " MR: " 915 << I->second.second; 916 unsigned VirtReg = I->second.first; 917 VirtRegMap::ModRef MR = I->second.second; 918 if (!VRM.hasStackSlot(VirtReg)) { 919 DOUT << ": No stack slot!\n"; 920 continue; 921 } 922 int SS = VRM.getStackSlot(VirtReg); 923 DOUT << " - StackSlot: " << SS << "\n"; 924 925 // If this folded instruction is just a use, check to see if it's a 926 // straight load from the virt reg slot. 927 if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) { 928 int FrameIdx; 929 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) { 930 if (FrameIdx == SS) { 931 // If this spill slot is available, turn it into a copy (or nothing) 932 // instead of leaving it as a load! 933 MachineInstr *SSMI = NULL; 934 if (unsigned InReg = Spills.getSpillSlotPhysReg(SS, SSMI)) { 935 DOUT << "Promoted Load To Copy: " << MI; 936 MachineFunction &MF = *MBB.getParent(); 937 if (DestReg != InReg) { 938 MRI->copyRegToReg(MBB, &MI, DestReg, InReg, 939 MF.getSSARegMap()->getRegClass(VirtReg)); 940 // Revisit the copy so we make sure to notice the effects of the 941 // operation on the destreg (either needing to RA it if it's 942 // virtual or needing to clobber any values if it's physical). 943 NextMII = &MI; 944 --NextMII; // backtrack to the copy. 945 } else 946 DOUT << "Removing now-noop copy: " << MI; 947 948 // Either way, the live range of the last kill of InReg has been 949 // extended. Remove its kill. 950 bool WasKill = false; 951 if (SSMI) { 952 int UIdx = SSMI->findRegisterUseOperand(InReg, true); 953 if (UIdx != -1) { 954 MachineOperand &MOK = SSMI->getOperand(UIdx); 955 WasKill = MOK.isKill(); 956 MOK.unsetIsKill(); 957 } 958 } 959 if (NextMII != MBB.end()) { 960 // If NextMII uses InReg and the use is not a two address 961 // operand, mark it killed. 962 int UIdx = NextMII->findRegisterUseOperand(InReg); 963 if (UIdx != -1) { 964 MachineOperand &MOU = NextMII->getOperand(UIdx); 965 if (WasKill) { 966 const TargetInstrDescriptor *NTID = 967 NextMII->getInstrDescriptor(); 968 if (NTID->getOperandConstraint(UIdx, TOI::TIED_TO) == -1) 969 MOU.setIsKill(); 970 } 971 Spills.addLastUse(InReg, &(*NextMII)); 972 } 973 } 974 975 VRM.RemoveFromFoldedVirtMap(&MI); 976 MBB.erase(&MI); 977 goto ProcessNextInst; 978 } 979 } 980 } 981 } 982 983 // If this reference is not a use, any previous store is now dead. 984 // Otherwise, the store to this stack slot is not dead anymore. 985 std::map<int, MachineInstr*>::iterator MDSI = MaybeDeadStores.find(SS); 986 if (MDSI != MaybeDeadStores.end()) { 987 if (MR & VirtRegMap::isRef) // Previous store is not dead. 988 MaybeDeadStores.erase(MDSI); 989 else { 990 // If we get here, the store is dead, nuke it now. 991 assert(VirtRegMap::isMod && "Can't be modref!"); 992 DOUT << "Removed dead store:\t" << *MDSI->second; 993 MBB.erase(MDSI->second); 994 VRM.RemoveFromFoldedVirtMap(MDSI->second); 995 MaybeDeadStores.erase(MDSI); 996 ++NumDSE; 997 } 998 } 999 1000 // If the spill slot value is available, and this is a new definition of 1001 // the value, the value is not available anymore. 1002 if (MR & VirtRegMap::isMod) { 1003 // Notice that the value in this stack slot has been modified. 1004 Spills.ModifyStackSlot(SS); 1005 1006 // If this is *just* a mod of the value, check to see if this is just a 1007 // store to the spill slot (i.e. the spill got merged into the copy). If 1008 // so, realize that the vreg is available now, and add the store to the 1009 // MaybeDeadStore info. 1010 int StackSlot; 1011 if (!(MR & VirtRegMap::isRef)) { 1012 if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) { 1013 assert(MRegisterInfo::isPhysicalRegister(SrcReg) && 1014 "Src hasn't been allocated yet?"); 1015 // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark 1016 // this as a potentially dead store in case there is a subsequent 1017 // store into the stack slot without a read from it. 1018 MaybeDeadStores[StackSlot] = &MI; 1019 1020 // If the stack slot value was previously available in some other 1021 // register, change it now. Otherwise, make the register available, 1022 // in PhysReg. 1023 Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/); 1024 } 1025 } 1026 } 1027 } 1028 1029 // Process all of the spilled defs. 1030 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { 1031 MachineOperand &MO = MI.getOperand(i); 1032 if (MO.isRegister() && MO.getReg() && MO.isDef()) { 1033 unsigned VirtReg = MO.getReg(); 1034 1035 if (!MRegisterInfo::isVirtualRegister(VirtReg)) { 1036 // Check to see if this is a noop copy. If so, eliminate the 1037 // instruction before considering the dest reg to be changed. 1038 unsigned Src, Dst; 1039 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) { 1040 ++NumDCE; 1041 DOUT << "Removing now-noop copy: " << MI; 1042 Spills.removeLastUse(Src, &MI); 1043 MBB.erase(&MI); 1044 VRM.RemoveFromFoldedVirtMap(&MI); 1045 Spills.disallowClobberPhysReg(VirtReg); 1046 goto ProcessNextInst; 1047 } 1048 1049 // If it's not a no-op copy, it clobbers the value in the destreg. 1050 Spills.ClobberPhysReg(VirtReg); 1051 ReusedOperands.markClobbered(VirtReg); 1052 1053 // Check to see if this instruction is a load from a stack slot into 1054 // a register. If so, this provides the stack slot value in the reg. 1055 int FrameIdx; 1056 if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) { 1057 assert(DestReg == VirtReg && "Unknown load situation!"); 1058 1059 // Otherwise, if it wasn't available, remember that it is now! 1060 Spills.addAvailable(FrameIdx, &MI, DestReg); 1061 goto ProcessNextInst; 1062 } 1063 1064 continue; 1065 } 1066 1067 // The only vregs left are stack slot definitions. 1068 int StackSlot = VRM.getStackSlot(VirtReg); 1069 const TargetRegisterClass *RC = 1070 MBB.getParent()->getSSARegMap()->getRegClass(VirtReg); 1071 1072 // If this def is part of a two-address operand, make sure to execute 1073 // the store from the correct physical register. 1074 unsigned PhysReg; 1075 int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i); 1076 if (TiedOp != -1) 1077 PhysReg = MI.getOperand(TiedOp).getReg(); 1078 else { 1079 PhysReg = VRM.getPhys(VirtReg); 1080 if (ReusedOperands.isClobbered(PhysReg)) { 1081 // Another def has taken the assigned physreg. It must have been a 1082 // use&def which got it due to reuse. Undo the reuse! 1083 PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI, 1084 Spills, MaybeDeadStores); 1085 } 1086 } 1087 1088 PhysRegsUsed[PhysReg] = true; 1089 ReusedOperands.markClobbered(PhysReg); 1090 MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC); 1091 DOUT << "Store:\t" << *next(MII); 1092 MI.getOperand(i).setReg(PhysReg); 1093 1094 // If there is a dead store to this stack slot, nuke it now. 1095 MachineInstr *&LastStore = MaybeDeadStores[StackSlot]; 1096 if (LastStore) { 1097 DOUT << "Removed dead store:\t" << *LastStore; 1098 ++NumDSE; 1099 MBB.erase(LastStore); 1100 VRM.RemoveFromFoldedVirtMap(LastStore); 1101 } 1102 LastStore = next(MII); 1103 1104 // If the stack slot value was previously available in some other 1105 // register, change it now. Otherwise, make the register available, 1106 // in PhysReg. 1107 Spills.ModifyStackSlot(StackSlot); 1108 Spills.ClobberPhysReg(PhysReg); 1109 Spills.addAvailable(StackSlot, LastStore, PhysReg); 1110 ++NumStores; 1111 1112 // Check to see if this is a noop copy. If so, eliminate the 1113 // instruction before considering the dest reg to be changed. 1114 { 1115 unsigned Src, Dst; 1116 if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) { 1117 ++NumDCE; 1118 DOUT << "Removing now-noop copy: " << MI; 1119 MBB.erase(&MI); 1120 VRM.RemoveFromFoldedVirtMap(&MI); 1121 goto ProcessNextInst; 1122 } 1123 } 1124 } 1125 } 1126 ProcessNextInst: 1127 MII = NextMII; 1128 } 1129} 1130 1131 1132 1133llvm::Spiller* llvm::createSpiller() { 1134 switch (SpillerOpt) { 1135 default: assert(0 && "Unreachable!"); 1136 case local: 1137 return new LocalSpiller(); 1138 case simple: 1139 return new SimpleSpiller(); 1140 } 1141} 1142