TwoAddressInstructionPass.cpp revision f4a5a613faa1a0eca6b884a6dfe83e8b1eb957b2
1//===-- TwoAddressInstructionPass.cpp - Two-Address instruction pass ------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the TwoAddress instruction pass which is used 11// by most register allocators. Two-Address instructions are rewritten 12// from: 13// 14// A = B op C 15// 16// to: 17// 18// A = B 19// A op= C 20// 21// Note that if a register allocator chooses to use this pass, that it 22// has to be capable of handling the non-SSA nature of these rewritten 23// virtual registers. 24// 25// It is also worth noting that the duplicate operand of the two 26// address instruction is removed. 27// 28//===----------------------------------------------------------------------===// 29 30#define DEBUG_TYPE "twoaddrinstr" 31#include "llvm/CodeGen/Passes.h" 32#include "llvm/Function.h" 33#include "llvm/CodeGen/LiveIntervalAnalysis.h" 34#include "llvm/CodeGen/LiveVariables.h" 35#include "llvm/CodeGen/MachineFunctionPass.h" 36#include "llvm/CodeGen/MachineInstr.h" 37#include "llvm/CodeGen/MachineInstrBuilder.h" 38#include "llvm/CodeGen/MachineRegisterInfo.h" 39#include "llvm/Analysis/AliasAnalysis.h" 40#include "llvm/MC/MCInstrItineraries.h" 41#include "llvm/Target/TargetRegisterInfo.h" 42#include "llvm/Target/TargetInstrInfo.h" 43#include "llvm/Target/TargetMachine.h" 44#include "llvm/Target/TargetOptions.h" 45#include "llvm/Support/Debug.h" 46#include "llvm/Support/ErrorHandling.h" 47#include "llvm/ADT/BitVector.h" 48#include "llvm/ADT/DenseMap.h" 49#include "llvm/ADT/SmallSet.h" 50#include "llvm/ADT/Statistic.h" 51#include "llvm/ADT/STLExtras.h" 52using namespace llvm; 53 54STATISTIC(NumTwoAddressInstrs, "Number of two-address instructions"); 55STATISTIC(NumCommuted , "Number of instructions commuted to coalesce"); 56STATISTIC(NumAggrCommuted , "Number of instructions aggressively commuted"); 57STATISTIC(NumConvertedTo3Addr, "Number of instructions promoted to 3-address"); 58STATISTIC(Num3AddrSunk, "Number of 3-address instructions sunk"); 59STATISTIC(NumReSchedUps, "Number of instructions re-scheduled up"); 60STATISTIC(NumReSchedDowns, "Number of instructions re-scheduled down"); 61 62namespace { 63 class TwoAddressInstructionPass : public MachineFunctionPass { 64 MachineFunction *MF; 65 const TargetInstrInfo *TII; 66 const TargetRegisterInfo *TRI; 67 const InstrItineraryData *InstrItins; 68 MachineRegisterInfo *MRI; 69 LiveVariables *LV; 70 SlotIndexes *Indexes; 71 LiveIntervals *LIS; 72 AliasAnalysis *AA; 73 CodeGenOpt::Level OptLevel; 74 75 // DistanceMap - Keep track the distance of a MI from the start of the 76 // current basic block. 77 DenseMap<MachineInstr*, unsigned> DistanceMap; 78 79 // SrcRegMap - A map from virtual registers to physical registers which 80 // are likely targets to be coalesced to due to copies from physical 81 // registers to virtual registers. e.g. v1024 = move r0. 82 DenseMap<unsigned, unsigned> SrcRegMap; 83 84 // DstRegMap - A map from virtual registers to physical registers which 85 // are likely targets to be coalesced to due to copies to physical 86 // registers from virtual registers. e.g. r1 = move v1024. 87 DenseMap<unsigned, unsigned> DstRegMap; 88 89 /// RegSequences - Keep track the list of REG_SEQUENCE instructions seen 90 /// during the initial walk of the machine function. 91 SmallVector<MachineInstr*, 16> RegSequences; 92 93 bool Sink3AddrInstruction(MachineBasicBlock *MBB, MachineInstr *MI, 94 unsigned Reg, 95 MachineBasicBlock::iterator OldPos); 96 97 bool NoUseAfterLastDef(unsigned Reg, MachineBasicBlock *MBB, unsigned Dist, 98 unsigned &LastDef); 99 100 bool isProfitableToCommute(unsigned regA, unsigned regB, unsigned regC, 101 MachineInstr *MI, MachineBasicBlock *MBB, 102 unsigned Dist); 103 104 bool CommuteInstruction(MachineBasicBlock::iterator &mi, 105 MachineFunction::iterator &mbbi, 106 unsigned RegB, unsigned RegC, unsigned Dist); 107 108 bool isProfitableToConv3Addr(unsigned RegA, unsigned RegB); 109 110 bool ConvertInstTo3Addr(MachineBasicBlock::iterator &mi, 111 MachineBasicBlock::iterator &nmi, 112 MachineFunction::iterator &mbbi, 113 unsigned RegA, unsigned RegB, unsigned Dist); 114 115 bool isDefTooClose(unsigned Reg, unsigned Dist, 116 MachineInstr *MI, MachineBasicBlock *MBB); 117 118 bool RescheduleMIBelowKill(MachineBasicBlock *MBB, 119 MachineBasicBlock::iterator &mi, 120 MachineBasicBlock::iterator &nmi, 121 unsigned Reg); 122 bool RescheduleKillAboveMI(MachineBasicBlock *MBB, 123 MachineBasicBlock::iterator &mi, 124 MachineBasicBlock::iterator &nmi, 125 unsigned Reg); 126 127 bool TryInstructionTransform(MachineBasicBlock::iterator &mi, 128 MachineBasicBlock::iterator &nmi, 129 MachineFunction::iterator &mbbi, 130 unsigned SrcIdx, unsigned DstIdx, 131 unsigned Dist, 132 SmallPtrSet<MachineInstr*, 8> &Processed); 133 134 void ScanUses(unsigned DstReg, MachineBasicBlock *MBB, 135 SmallPtrSet<MachineInstr*, 8> &Processed); 136 137 void ProcessCopy(MachineInstr *MI, MachineBasicBlock *MBB, 138 SmallPtrSet<MachineInstr*, 8> &Processed); 139 140 typedef SmallVector<std::pair<unsigned, unsigned>, 4> TiedPairList; 141 typedef SmallDenseMap<unsigned, TiedPairList> TiedOperandMap; 142 bool collectTiedOperands(MachineInstr *MI, TiedOperandMap&); 143 void processTiedPairs(MachineInstr *MI, TiedPairList&, unsigned &Dist); 144 145 /// EliminateRegSequences - Eliminate REG_SEQUENCE instructions as part 146 /// of the de-ssa process. This replaces sources of REG_SEQUENCE as 147 /// sub-register references of the register defined by REG_SEQUENCE. 148 bool EliminateRegSequences(); 149 150 public: 151 static char ID; // Pass identification, replacement for typeid 152 TwoAddressInstructionPass() : MachineFunctionPass(ID) { 153 initializeTwoAddressInstructionPassPass(*PassRegistry::getPassRegistry()); 154 } 155 156 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 157 AU.setPreservesCFG(); 158 AU.addRequired<AliasAnalysis>(); 159 AU.addPreserved<LiveVariables>(); 160 AU.addPreserved<SlotIndexes>(); 161 AU.addPreserved<LiveIntervals>(); 162 AU.addPreservedID(MachineLoopInfoID); 163 AU.addPreservedID(MachineDominatorsID); 164 MachineFunctionPass::getAnalysisUsage(AU); 165 } 166 167 /// runOnMachineFunction - Pass entry point. 168 bool runOnMachineFunction(MachineFunction&); 169 }; 170} 171 172char TwoAddressInstructionPass::ID = 0; 173INITIALIZE_PASS_BEGIN(TwoAddressInstructionPass, "twoaddressinstruction", 174 "Two-Address instruction pass", false, false) 175INITIALIZE_AG_DEPENDENCY(AliasAnalysis) 176INITIALIZE_PASS_END(TwoAddressInstructionPass, "twoaddressinstruction", 177 "Two-Address instruction pass", false, false) 178 179char &llvm::TwoAddressInstructionPassID = TwoAddressInstructionPass::ID; 180 181/// Sink3AddrInstruction - A two-address instruction has been converted to a 182/// three-address instruction to avoid clobbering a register. Try to sink it 183/// past the instruction that would kill the above mentioned register to reduce 184/// register pressure. 185bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB, 186 MachineInstr *MI, unsigned SavedReg, 187 MachineBasicBlock::iterator OldPos) { 188 // FIXME: Shouldn't we be trying to do this before we three-addressify the 189 // instruction? After this transformation is done, we no longer need 190 // the instruction to be in three-address form. 191 192 // Check if it's safe to move this instruction. 193 bool SeenStore = true; // Be conservative. 194 if (!MI->isSafeToMove(TII, AA, SeenStore)) 195 return false; 196 197 unsigned DefReg = 0; 198 SmallSet<unsigned, 4> UseRegs; 199 200 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 201 const MachineOperand &MO = MI->getOperand(i); 202 if (!MO.isReg()) 203 continue; 204 unsigned MOReg = MO.getReg(); 205 if (!MOReg) 206 continue; 207 if (MO.isUse() && MOReg != SavedReg) 208 UseRegs.insert(MO.getReg()); 209 if (!MO.isDef()) 210 continue; 211 if (MO.isImplicit()) 212 // Don't try to move it if it implicitly defines a register. 213 return false; 214 if (DefReg) 215 // For now, don't move any instructions that define multiple registers. 216 return false; 217 DefReg = MO.getReg(); 218 } 219 220 // Find the instruction that kills SavedReg. 221 MachineInstr *KillMI = NULL; 222 for (MachineRegisterInfo::use_nodbg_iterator 223 UI = MRI->use_nodbg_begin(SavedReg), 224 UE = MRI->use_nodbg_end(); UI != UE; ++UI) { 225 MachineOperand &UseMO = UI.getOperand(); 226 if (!UseMO.isKill()) 227 continue; 228 KillMI = UseMO.getParent(); 229 break; 230 } 231 232 // If we find the instruction that kills SavedReg, and it is in an 233 // appropriate location, we can try to sink the current instruction 234 // past it. 235 if (!KillMI || KillMI->getParent() != MBB || KillMI == MI || 236 KillMI == OldPos || KillMI->isTerminator()) 237 return false; 238 239 // If any of the definitions are used by another instruction between the 240 // position and the kill use, then it's not safe to sink it. 241 // 242 // FIXME: This can be sped up if there is an easy way to query whether an 243 // instruction is before or after another instruction. Then we can use 244 // MachineRegisterInfo def / use instead. 245 MachineOperand *KillMO = NULL; 246 MachineBasicBlock::iterator KillPos = KillMI; 247 ++KillPos; 248 249 unsigned NumVisited = 0; 250 for (MachineBasicBlock::iterator I = llvm::next(OldPos); I != KillPos; ++I) { 251 MachineInstr *OtherMI = I; 252 // DBG_VALUE cannot be counted against the limit. 253 if (OtherMI->isDebugValue()) 254 continue; 255 if (NumVisited > 30) // FIXME: Arbitrary limit to reduce compile time cost. 256 return false; 257 ++NumVisited; 258 for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) { 259 MachineOperand &MO = OtherMI->getOperand(i); 260 if (!MO.isReg()) 261 continue; 262 unsigned MOReg = MO.getReg(); 263 if (!MOReg) 264 continue; 265 if (DefReg == MOReg) 266 return false; 267 268 if (MO.isKill()) { 269 if (OtherMI == KillMI && MOReg == SavedReg) 270 // Save the operand that kills the register. We want to unset the kill 271 // marker if we can sink MI past it. 272 KillMO = &MO; 273 else if (UseRegs.count(MOReg)) 274 // One of the uses is killed before the destination. 275 return false; 276 } 277 } 278 } 279 assert(KillMO && "Didn't find kill"); 280 281 // Update kill and LV information. 282 KillMO->setIsKill(false); 283 KillMO = MI->findRegisterUseOperand(SavedReg, false, TRI); 284 KillMO->setIsKill(true); 285 286 if (LV) 287 LV->replaceKillInstruction(SavedReg, KillMI, MI); 288 289 // Move instruction to its destination. 290 MBB->remove(MI); 291 MBB->insert(KillPos, MI); 292 293 if (LIS) 294 LIS->handleMove(MI); 295 296 ++Num3AddrSunk; 297 return true; 298} 299 300/// NoUseAfterLastDef - Return true if there are no intervening uses between the 301/// last instruction in the MBB that defines the specified register and the 302/// two-address instruction which is being processed. It also returns the last 303/// def location by reference 304bool TwoAddressInstructionPass::NoUseAfterLastDef(unsigned Reg, 305 MachineBasicBlock *MBB, unsigned Dist, 306 unsigned &LastDef) { 307 LastDef = 0; 308 unsigned LastUse = Dist; 309 for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(Reg), 310 E = MRI->reg_end(); I != E; ++I) { 311 MachineOperand &MO = I.getOperand(); 312 MachineInstr *MI = MO.getParent(); 313 if (MI->getParent() != MBB || MI->isDebugValue()) 314 continue; 315 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI); 316 if (DI == DistanceMap.end()) 317 continue; 318 if (MO.isUse() && DI->second < LastUse) 319 LastUse = DI->second; 320 if (MO.isDef() && DI->second > LastDef) 321 LastDef = DI->second; 322 } 323 324 return !(LastUse > LastDef && LastUse < Dist); 325} 326 327/// isCopyToReg - Return true if the specified MI is a copy instruction or 328/// a extract_subreg instruction. It also returns the source and destination 329/// registers and whether they are physical registers by reference. 330static bool isCopyToReg(MachineInstr &MI, const TargetInstrInfo *TII, 331 unsigned &SrcReg, unsigned &DstReg, 332 bool &IsSrcPhys, bool &IsDstPhys) { 333 SrcReg = 0; 334 DstReg = 0; 335 if (MI.isCopy()) { 336 DstReg = MI.getOperand(0).getReg(); 337 SrcReg = MI.getOperand(1).getReg(); 338 } else if (MI.isInsertSubreg() || MI.isSubregToReg()) { 339 DstReg = MI.getOperand(0).getReg(); 340 SrcReg = MI.getOperand(2).getReg(); 341 } else 342 return false; 343 344 IsSrcPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg); 345 IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg); 346 return true; 347} 348 349/// isKilled - Test if the given register value, which is used by the given 350/// instruction, is killed by the given instruction. This looks through 351/// coalescable copies to see if the original value is potentially not killed. 352/// 353/// For example, in this code: 354/// 355/// %reg1034 = copy %reg1024 356/// %reg1035 = copy %reg1025<kill> 357/// %reg1036 = add %reg1034<kill>, %reg1035<kill> 358/// 359/// %reg1034 is not considered to be killed, since it is copied from a 360/// register which is not killed. Treating it as not killed lets the 361/// normal heuristics commute the (two-address) add, which lets 362/// coalescing eliminate the extra copy. 363/// 364static bool isKilled(MachineInstr &MI, unsigned Reg, 365 const MachineRegisterInfo *MRI, 366 const TargetInstrInfo *TII) { 367 MachineInstr *DefMI = &MI; 368 for (;;) { 369 if (!DefMI->killsRegister(Reg)) 370 return false; 371 if (TargetRegisterInfo::isPhysicalRegister(Reg)) 372 return true; 373 MachineRegisterInfo::def_iterator Begin = MRI->def_begin(Reg); 374 // If there are multiple defs, we can't do a simple analysis, so just 375 // go with what the kill flag says. 376 if (llvm::next(Begin) != MRI->def_end()) 377 return true; 378 DefMI = &*Begin; 379 bool IsSrcPhys, IsDstPhys; 380 unsigned SrcReg, DstReg; 381 // If the def is something other than a copy, then it isn't going to 382 // be coalesced, so follow the kill flag. 383 if (!isCopyToReg(*DefMI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys)) 384 return true; 385 Reg = SrcReg; 386 } 387} 388 389/// isTwoAddrUse - Return true if the specified MI uses the specified register 390/// as a two-address use. If so, return the destination register by reference. 391static bool isTwoAddrUse(MachineInstr &MI, unsigned Reg, unsigned &DstReg) { 392 const MCInstrDesc &MCID = MI.getDesc(); 393 unsigned NumOps = MI.isInlineAsm() 394 ? MI.getNumOperands() : MCID.getNumOperands(); 395 for (unsigned i = 0; i != NumOps; ++i) { 396 const MachineOperand &MO = MI.getOperand(i); 397 if (!MO.isReg() || !MO.isUse() || MO.getReg() != Reg) 398 continue; 399 unsigned ti; 400 if (MI.isRegTiedToDefOperand(i, &ti)) { 401 DstReg = MI.getOperand(ti).getReg(); 402 return true; 403 } 404 } 405 return false; 406} 407 408/// findOnlyInterestingUse - Given a register, if has a single in-basic block 409/// use, return the use instruction if it's a copy or a two-address use. 410static 411MachineInstr *findOnlyInterestingUse(unsigned Reg, MachineBasicBlock *MBB, 412 MachineRegisterInfo *MRI, 413 const TargetInstrInfo *TII, 414 bool &IsCopy, 415 unsigned &DstReg, bool &IsDstPhys) { 416 if (!MRI->hasOneNonDBGUse(Reg)) 417 // None or more than one use. 418 return 0; 419 MachineInstr &UseMI = *MRI->use_nodbg_begin(Reg); 420 if (UseMI.getParent() != MBB) 421 return 0; 422 unsigned SrcReg; 423 bool IsSrcPhys; 424 if (isCopyToReg(UseMI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys)) { 425 IsCopy = true; 426 return &UseMI; 427 } 428 IsDstPhys = false; 429 if (isTwoAddrUse(UseMI, Reg, DstReg)) { 430 IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg); 431 return &UseMI; 432 } 433 return 0; 434} 435 436/// getMappedReg - Return the physical register the specified virtual register 437/// might be mapped to. 438static unsigned 439getMappedReg(unsigned Reg, DenseMap<unsigned, unsigned> &RegMap) { 440 while (TargetRegisterInfo::isVirtualRegister(Reg)) { 441 DenseMap<unsigned, unsigned>::iterator SI = RegMap.find(Reg); 442 if (SI == RegMap.end()) 443 return 0; 444 Reg = SI->second; 445 } 446 if (TargetRegisterInfo::isPhysicalRegister(Reg)) 447 return Reg; 448 return 0; 449} 450 451/// regsAreCompatible - Return true if the two registers are equal or aliased. 452/// 453static bool 454regsAreCompatible(unsigned RegA, unsigned RegB, const TargetRegisterInfo *TRI) { 455 if (RegA == RegB) 456 return true; 457 if (!RegA || !RegB) 458 return false; 459 return TRI->regsOverlap(RegA, RegB); 460} 461 462 463/// isProfitableToCommute - Return true if it's potentially profitable to commute 464/// the two-address instruction that's being processed. 465bool 466TwoAddressInstructionPass::isProfitableToCommute(unsigned regA, unsigned regB, 467 unsigned regC, 468 MachineInstr *MI, MachineBasicBlock *MBB, 469 unsigned Dist) { 470 if (OptLevel == CodeGenOpt::None) 471 return false; 472 473 // Determine if it's profitable to commute this two address instruction. In 474 // general, we want no uses between this instruction and the definition of 475 // the two-address register. 476 // e.g. 477 // %reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1 478 // %reg1029<def> = MOV8rr %reg1028 479 // %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead> 480 // insert => %reg1030<def> = MOV8rr %reg1028 481 // %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead> 482 // In this case, it might not be possible to coalesce the second MOV8rr 483 // instruction if the first one is coalesced. So it would be profitable to 484 // commute it: 485 // %reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1 486 // %reg1029<def> = MOV8rr %reg1028 487 // %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead> 488 // insert => %reg1030<def> = MOV8rr %reg1029 489 // %reg1030<def> = ADD8rr %reg1029<kill>, %reg1028<kill>, %EFLAGS<imp-def,dead> 490 491 if (!MI->killsRegister(regC)) 492 return false; 493 494 // Ok, we have something like: 495 // %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead> 496 // let's see if it's worth commuting it. 497 498 // Look for situations like this: 499 // %reg1024<def> = MOV r1 500 // %reg1025<def> = MOV r0 501 // %reg1026<def> = ADD %reg1024, %reg1025 502 // r0 = MOV %reg1026 503 // Commute the ADD to hopefully eliminate an otherwise unavoidable copy. 504 unsigned ToRegA = getMappedReg(regA, DstRegMap); 505 if (ToRegA) { 506 unsigned FromRegB = getMappedReg(regB, SrcRegMap); 507 unsigned FromRegC = getMappedReg(regC, SrcRegMap); 508 bool BComp = !FromRegB || regsAreCompatible(FromRegB, ToRegA, TRI); 509 bool CComp = !FromRegC || regsAreCompatible(FromRegC, ToRegA, TRI); 510 if (BComp != CComp) 511 return !BComp && CComp; 512 } 513 514 // If there is a use of regC between its last def (could be livein) and this 515 // instruction, then bail. 516 unsigned LastDefC = 0; 517 if (!NoUseAfterLastDef(regC, MBB, Dist, LastDefC)) 518 return false; 519 520 // If there is a use of regB between its last def (could be livein) and this 521 // instruction, then go ahead and make this transformation. 522 unsigned LastDefB = 0; 523 if (!NoUseAfterLastDef(regB, MBB, Dist, LastDefB)) 524 return true; 525 526 // Since there are no intervening uses for both registers, then commute 527 // if the def of regC is closer. Its live interval is shorter. 528 return LastDefB && LastDefC && LastDefC > LastDefB; 529} 530 531/// CommuteInstruction - Commute a two-address instruction and update the basic 532/// block, distance map, and live variables if needed. Return true if it is 533/// successful. 534bool 535TwoAddressInstructionPass::CommuteInstruction(MachineBasicBlock::iterator &mi, 536 MachineFunction::iterator &mbbi, 537 unsigned RegB, unsigned RegC, unsigned Dist) { 538 MachineInstr *MI = mi; 539 DEBUG(dbgs() << "2addr: COMMUTING : " << *MI); 540 MachineInstr *NewMI = TII->commuteInstruction(MI); 541 542 if (NewMI == 0) { 543 DEBUG(dbgs() << "2addr: COMMUTING FAILED!\n"); 544 return false; 545 } 546 547 DEBUG(dbgs() << "2addr: COMMUTED TO: " << *NewMI); 548 // If the instruction changed to commute it, update livevar. 549 if (NewMI != MI) { 550 if (LV) 551 // Update live variables 552 LV->replaceKillInstruction(RegC, MI, NewMI); 553 if (Indexes) 554 Indexes->replaceMachineInstrInMaps(MI, NewMI); 555 556 mbbi->insert(mi, NewMI); // Insert the new inst 557 mbbi->erase(mi); // Nuke the old inst. 558 mi = NewMI; 559 DistanceMap.insert(std::make_pair(NewMI, Dist)); 560 } 561 562 // Update source register map. 563 unsigned FromRegC = getMappedReg(RegC, SrcRegMap); 564 if (FromRegC) { 565 unsigned RegA = MI->getOperand(0).getReg(); 566 SrcRegMap[RegA] = FromRegC; 567 } 568 569 return true; 570} 571 572/// isProfitableToConv3Addr - Return true if it is profitable to convert the 573/// given 2-address instruction to a 3-address one. 574bool 575TwoAddressInstructionPass::isProfitableToConv3Addr(unsigned RegA,unsigned RegB){ 576 // Look for situations like this: 577 // %reg1024<def> = MOV r1 578 // %reg1025<def> = MOV r0 579 // %reg1026<def> = ADD %reg1024, %reg1025 580 // r2 = MOV %reg1026 581 // Turn ADD into a 3-address instruction to avoid a copy. 582 unsigned FromRegB = getMappedReg(RegB, SrcRegMap); 583 if (!FromRegB) 584 return false; 585 unsigned ToRegA = getMappedReg(RegA, DstRegMap); 586 return (ToRegA && !regsAreCompatible(FromRegB, ToRegA, TRI)); 587} 588 589/// ConvertInstTo3Addr - Convert the specified two-address instruction into a 590/// three address one. Return true if this transformation was successful. 591bool 592TwoAddressInstructionPass::ConvertInstTo3Addr(MachineBasicBlock::iterator &mi, 593 MachineBasicBlock::iterator &nmi, 594 MachineFunction::iterator &mbbi, 595 unsigned RegA, unsigned RegB, 596 unsigned Dist) { 597 MachineInstr *NewMI = TII->convertToThreeAddress(mbbi, mi, LV); 598 if (NewMI) { 599 DEBUG(dbgs() << "2addr: CONVERTING 2-ADDR: " << *mi); 600 DEBUG(dbgs() << "2addr: TO 3-ADDR: " << *NewMI); 601 bool Sunk = false; 602 603 if (Indexes) 604 Indexes->replaceMachineInstrInMaps(mi, NewMI); 605 606 if (NewMI->findRegisterUseOperand(RegB, false, TRI)) 607 // FIXME: Temporary workaround. If the new instruction doesn't 608 // uses RegB, convertToThreeAddress must have created more 609 // then one instruction. 610 Sunk = Sink3AddrInstruction(mbbi, NewMI, RegB, mi); 611 612 mbbi->erase(mi); // Nuke the old inst. 613 614 if (!Sunk) { 615 DistanceMap.insert(std::make_pair(NewMI, Dist)); 616 mi = NewMI; 617 nmi = llvm::next(mi); 618 } 619 620 // Update source and destination register maps. 621 SrcRegMap.erase(RegA); 622 DstRegMap.erase(RegB); 623 return true; 624 } 625 626 return false; 627} 628 629/// ScanUses - Scan forward recursively for only uses, update maps if the use 630/// is a copy or a two-address instruction. 631void 632TwoAddressInstructionPass::ScanUses(unsigned DstReg, MachineBasicBlock *MBB, 633 SmallPtrSet<MachineInstr*, 8> &Processed) { 634 SmallVector<unsigned, 4> VirtRegPairs; 635 bool IsDstPhys; 636 bool IsCopy = false; 637 unsigned NewReg = 0; 638 unsigned Reg = DstReg; 639 while (MachineInstr *UseMI = findOnlyInterestingUse(Reg, MBB, MRI, TII,IsCopy, 640 NewReg, IsDstPhys)) { 641 if (IsCopy && !Processed.insert(UseMI)) 642 break; 643 644 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UseMI); 645 if (DI != DistanceMap.end()) 646 // Earlier in the same MBB.Reached via a back edge. 647 break; 648 649 if (IsDstPhys) { 650 VirtRegPairs.push_back(NewReg); 651 break; 652 } 653 bool isNew = SrcRegMap.insert(std::make_pair(NewReg, Reg)).second; 654 if (!isNew) 655 assert(SrcRegMap[NewReg] == Reg && "Can't map to two src registers!"); 656 VirtRegPairs.push_back(NewReg); 657 Reg = NewReg; 658 } 659 660 if (!VirtRegPairs.empty()) { 661 unsigned ToReg = VirtRegPairs.back(); 662 VirtRegPairs.pop_back(); 663 while (!VirtRegPairs.empty()) { 664 unsigned FromReg = VirtRegPairs.back(); 665 VirtRegPairs.pop_back(); 666 bool isNew = DstRegMap.insert(std::make_pair(FromReg, ToReg)).second; 667 if (!isNew) 668 assert(DstRegMap[FromReg] == ToReg &&"Can't map to two dst registers!"); 669 ToReg = FromReg; 670 } 671 bool isNew = DstRegMap.insert(std::make_pair(DstReg, ToReg)).second; 672 if (!isNew) 673 assert(DstRegMap[DstReg] == ToReg && "Can't map to two dst registers!"); 674 } 675} 676 677/// ProcessCopy - If the specified instruction is not yet processed, process it 678/// if it's a copy. For a copy instruction, we find the physical registers the 679/// source and destination registers might be mapped to. These are kept in 680/// point-to maps used to determine future optimizations. e.g. 681/// v1024 = mov r0 682/// v1025 = mov r1 683/// v1026 = add v1024, v1025 684/// r1 = mov r1026 685/// If 'add' is a two-address instruction, v1024, v1026 are both potentially 686/// coalesced to r0 (from the input side). v1025 is mapped to r1. v1026 is 687/// potentially joined with r1 on the output side. It's worthwhile to commute 688/// 'add' to eliminate a copy. 689void TwoAddressInstructionPass::ProcessCopy(MachineInstr *MI, 690 MachineBasicBlock *MBB, 691 SmallPtrSet<MachineInstr*, 8> &Processed) { 692 if (Processed.count(MI)) 693 return; 694 695 bool IsSrcPhys, IsDstPhys; 696 unsigned SrcReg, DstReg; 697 if (!isCopyToReg(*MI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys)) 698 return; 699 700 if (IsDstPhys && !IsSrcPhys) 701 DstRegMap.insert(std::make_pair(SrcReg, DstReg)); 702 else if (!IsDstPhys && IsSrcPhys) { 703 bool isNew = SrcRegMap.insert(std::make_pair(DstReg, SrcReg)).second; 704 if (!isNew) 705 assert(SrcRegMap[DstReg] == SrcReg && 706 "Can't map to two src physical registers!"); 707 708 ScanUses(DstReg, MBB, Processed); 709 } 710 711 Processed.insert(MI); 712 return; 713} 714 715/// RescheduleMIBelowKill - If there is one more local instruction that reads 716/// 'Reg' and it kills 'Reg, consider moving the instruction below the kill 717/// instruction in order to eliminate the need for the copy. 718bool 719TwoAddressInstructionPass::RescheduleMIBelowKill(MachineBasicBlock *MBB, 720 MachineBasicBlock::iterator &mi, 721 MachineBasicBlock::iterator &nmi, 722 unsigned Reg) { 723 // Bail immediately if we don't have LV available. We use it to find kills 724 // efficiently. 725 if (!LV) 726 return false; 727 728 MachineInstr *MI = &*mi; 729 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI); 730 if (DI == DistanceMap.end()) 731 // Must be created from unfolded load. Don't waste time trying this. 732 return false; 733 734 MachineInstr *KillMI = LV->getVarInfo(Reg).findKill(MBB); 735 if (!KillMI || MI == KillMI || KillMI->isCopy() || KillMI->isCopyLike()) 736 // Don't mess with copies, they may be coalesced later. 737 return false; 738 739 if (KillMI->hasUnmodeledSideEffects() || KillMI->isCall() || 740 KillMI->isBranch() || KillMI->isTerminator()) 741 // Don't move pass calls, etc. 742 return false; 743 744 unsigned DstReg; 745 if (isTwoAddrUse(*KillMI, Reg, DstReg)) 746 return false; 747 748 bool SeenStore = true; 749 if (!MI->isSafeToMove(TII, AA, SeenStore)) 750 return false; 751 752 if (TII->getInstrLatency(InstrItins, MI) > 1) 753 // FIXME: Needs more sophisticated heuristics. 754 return false; 755 756 SmallSet<unsigned, 2> Uses; 757 SmallSet<unsigned, 2> Kills; 758 SmallSet<unsigned, 2> Defs; 759 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 760 const MachineOperand &MO = MI->getOperand(i); 761 if (!MO.isReg()) 762 continue; 763 unsigned MOReg = MO.getReg(); 764 if (!MOReg) 765 continue; 766 if (MO.isDef()) 767 Defs.insert(MOReg); 768 else { 769 Uses.insert(MOReg); 770 if (MO.isKill() && MOReg != Reg) 771 Kills.insert(MOReg); 772 } 773 } 774 775 // Move the copies connected to MI down as well. 776 MachineBasicBlock::iterator From = MI; 777 MachineBasicBlock::iterator To = llvm::next(From); 778 while (To->isCopy() && Defs.count(To->getOperand(1).getReg())) { 779 Defs.insert(To->getOperand(0).getReg()); 780 ++To; 781 } 782 783 // Check if the reschedule will not break depedencies. 784 unsigned NumVisited = 0; 785 MachineBasicBlock::iterator KillPos = KillMI; 786 ++KillPos; 787 for (MachineBasicBlock::iterator I = To; I != KillPos; ++I) { 788 MachineInstr *OtherMI = I; 789 // DBG_VALUE cannot be counted against the limit. 790 if (OtherMI->isDebugValue()) 791 continue; 792 if (NumVisited > 10) // FIXME: Arbitrary limit to reduce compile time cost. 793 return false; 794 ++NumVisited; 795 if (OtherMI->hasUnmodeledSideEffects() || OtherMI->isCall() || 796 OtherMI->isBranch() || OtherMI->isTerminator()) 797 // Don't move pass calls, etc. 798 return false; 799 for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) { 800 const MachineOperand &MO = OtherMI->getOperand(i); 801 if (!MO.isReg()) 802 continue; 803 unsigned MOReg = MO.getReg(); 804 if (!MOReg) 805 continue; 806 if (MO.isDef()) { 807 if (Uses.count(MOReg)) 808 // Physical register use would be clobbered. 809 return false; 810 if (!MO.isDead() && Defs.count(MOReg)) 811 // May clobber a physical register def. 812 // FIXME: This may be too conservative. It's ok if the instruction 813 // is sunken completely below the use. 814 return false; 815 } else { 816 if (Defs.count(MOReg)) 817 return false; 818 if (MOReg != Reg && 819 ((MO.isKill() && Uses.count(MOReg)) || Kills.count(MOReg))) 820 // Don't want to extend other live ranges and update kills. 821 return false; 822 if (MOReg == Reg && !MO.isKill()) 823 // We can't schedule across a use of the register in question. 824 return false; 825 // Ensure that if this is register in question, its the kill we expect. 826 assert((MOReg != Reg || OtherMI == KillMI) && 827 "Found multiple kills of a register in a basic block"); 828 } 829 } 830 } 831 832 // Move debug info as well. 833 while (From != MBB->begin() && llvm::prior(From)->isDebugValue()) 834 --From; 835 836 // Copies following MI may have been moved as well. 837 nmi = To; 838 MBB->splice(KillPos, MBB, From, To); 839 DistanceMap.erase(DI); 840 841 // Update live variables 842 LV->removeVirtualRegisterKilled(Reg, KillMI); 843 LV->addVirtualRegisterKilled(Reg, MI); 844 if (LIS) 845 LIS->handleMove(MI); 846 847 DEBUG(dbgs() << "\trescheduled below kill: " << *KillMI); 848 return true; 849} 850 851/// isDefTooClose - Return true if the re-scheduling will put the given 852/// instruction too close to the defs of its register dependencies. 853bool TwoAddressInstructionPass::isDefTooClose(unsigned Reg, unsigned Dist, 854 MachineInstr *MI, 855 MachineBasicBlock *MBB) { 856 for (MachineRegisterInfo::def_iterator DI = MRI->def_begin(Reg), 857 DE = MRI->def_end(); DI != DE; ++DI) { 858 MachineInstr *DefMI = &*DI; 859 if (DefMI->getParent() != MBB || DefMI->isCopy() || DefMI->isCopyLike()) 860 continue; 861 if (DefMI == MI) 862 return true; // MI is defining something KillMI uses 863 DenseMap<MachineInstr*, unsigned>::iterator DDI = DistanceMap.find(DefMI); 864 if (DDI == DistanceMap.end()) 865 return true; // Below MI 866 unsigned DefDist = DDI->second; 867 assert(Dist > DefDist && "Visited def already?"); 868 if (TII->getInstrLatency(InstrItins, DefMI) > (Dist - DefDist)) 869 return true; 870 } 871 return false; 872} 873 874/// RescheduleKillAboveMI - If there is one more local instruction that reads 875/// 'Reg' and it kills 'Reg, consider moving the kill instruction above the 876/// current two-address instruction in order to eliminate the need for the 877/// copy. 878bool 879TwoAddressInstructionPass::RescheduleKillAboveMI(MachineBasicBlock *MBB, 880 MachineBasicBlock::iterator &mi, 881 MachineBasicBlock::iterator &nmi, 882 unsigned Reg) { 883 // Bail immediately if we don't have LV available. We use it to find kills 884 // efficiently. 885 if (!LV) 886 return false; 887 888 MachineInstr *MI = &*mi; 889 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI); 890 if (DI == DistanceMap.end()) 891 // Must be created from unfolded load. Don't waste time trying this. 892 return false; 893 894 MachineInstr *KillMI = LV->getVarInfo(Reg).findKill(MBB); 895 if (!KillMI || MI == KillMI || KillMI->isCopy() || KillMI->isCopyLike()) 896 // Don't mess with copies, they may be coalesced later. 897 return false; 898 899 unsigned DstReg; 900 if (isTwoAddrUse(*KillMI, Reg, DstReg)) 901 return false; 902 903 bool SeenStore = true; 904 if (!KillMI->isSafeToMove(TII, AA, SeenStore)) 905 return false; 906 907 SmallSet<unsigned, 2> Uses; 908 SmallSet<unsigned, 2> Kills; 909 SmallSet<unsigned, 2> Defs; 910 SmallSet<unsigned, 2> LiveDefs; 911 for (unsigned i = 0, e = KillMI->getNumOperands(); i != e; ++i) { 912 const MachineOperand &MO = KillMI->getOperand(i); 913 if (!MO.isReg()) 914 continue; 915 unsigned MOReg = MO.getReg(); 916 if (MO.isUse()) { 917 if (!MOReg) 918 continue; 919 if (isDefTooClose(MOReg, DI->second, MI, MBB)) 920 return false; 921 if (MOReg == Reg && !MO.isKill()) 922 return false; 923 Uses.insert(MOReg); 924 if (MO.isKill() && MOReg != Reg) 925 Kills.insert(MOReg); 926 } else if (TargetRegisterInfo::isPhysicalRegister(MOReg)) { 927 Defs.insert(MOReg); 928 if (!MO.isDead()) 929 LiveDefs.insert(MOReg); 930 } 931 } 932 933 // Check if the reschedule will not break depedencies. 934 unsigned NumVisited = 0; 935 MachineBasicBlock::iterator KillPos = KillMI; 936 for (MachineBasicBlock::iterator I = mi; I != KillPos; ++I) { 937 MachineInstr *OtherMI = I; 938 // DBG_VALUE cannot be counted against the limit. 939 if (OtherMI->isDebugValue()) 940 continue; 941 if (NumVisited > 10) // FIXME: Arbitrary limit to reduce compile time cost. 942 return false; 943 ++NumVisited; 944 if (OtherMI->hasUnmodeledSideEffects() || OtherMI->isCall() || 945 OtherMI->isBranch() || OtherMI->isTerminator()) 946 // Don't move pass calls, etc. 947 return false; 948 SmallVector<unsigned, 2> OtherDefs; 949 for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) { 950 const MachineOperand &MO = OtherMI->getOperand(i); 951 if (!MO.isReg()) 952 continue; 953 unsigned MOReg = MO.getReg(); 954 if (!MOReg) 955 continue; 956 if (MO.isUse()) { 957 if (Defs.count(MOReg)) 958 // Moving KillMI can clobber the physical register if the def has 959 // not been seen. 960 return false; 961 if (Kills.count(MOReg)) 962 // Don't want to extend other live ranges and update kills. 963 return false; 964 if (OtherMI != MI && MOReg == Reg && !MO.isKill()) 965 // We can't schedule across a use of the register in question. 966 return false; 967 } else { 968 OtherDefs.push_back(MOReg); 969 } 970 } 971 972 for (unsigned i = 0, e = OtherDefs.size(); i != e; ++i) { 973 unsigned MOReg = OtherDefs[i]; 974 if (Uses.count(MOReg)) 975 return false; 976 if (TargetRegisterInfo::isPhysicalRegister(MOReg) && 977 LiveDefs.count(MOReg)) 978 return false; 979 // Physical register def is seen. 980 Defs.erase(MOReg); 981 } 982 } 983 984 // Move the old kill above MI, don't forget to move debug info as well. 985 MachineBasicBlock::iterator InsertPos = mi; 986 while (InsertPos != MBB->begin() && llvm::prior(InsertPos)->isDebugValue()) 987 --InsertPos; 988 MachineBasicBlock::iterator From = KillMI; 989 MachineBasicBlock::iterator To = llvm::next(From); 990 while (llvm::prior(From)->isDebugValue()) 991 --From; 992 MBB->splice(InsertPos, MBB, From, To); 993 994 nmi = llvm::prior(InsertPos); // Backtrack so we process the moved instr. 995 DistanceMap.erase(DI); 996 997 // Update live variables 998 LV->removeVirtualRegisterKilled(Reg, KillMI); 999 LV->addVirtualRegisterKilled(Reg, MI); 1000 if (LIS) 1001 LIS->handleMove(KillMI); 1002 1003 DEBUG(dbgs() << "\trescheduled kill: " << *KillMI); 1004 return true; 1005} 1006 1007/// TryInstructionTransform - For the case where an instruction has a single 1008/// pair of tied register operands, attempt some transformations that may 1009/// either eliminate the tied operands or improve the opportunities for 1010/// coalescing away the register copy. Returns true if no copy needs to be 1011/// inserted to untie mi's operands (either because they were untied, or 1012/// because mi was rescheduled, and will be visited again later). 1013bool TwoAddressInstructionPass:: 1014TryInstructionTransform(MachineBasicBlock::iterator &mi, 1015 MachineBasicBlock::iterator &nmi, 1016 MachineFunction::iterator &mbbi, 1017 unsigned SrcIdx, unsigned DstIdx, unsigned Dist, 1018 SmallPtrSet<MachineInstr*, 8> &Processed) { 1019 if (OptLevel == CodeGenOpt::None) 1020 return false; 1021 1022 MachineInstr &MI = *mi; 1023 unsigned regA = MI.getOperand(DstIdx).getReg(); 1024 unsigned regB = MI.getOperand(SrcIdx).getReg(); 1025 1026 assert(TargetRegisterInfo::isVirtualRegister(regB) && 1027 "cannot make instruction into two-address form"); 1028 bool regBKilled = isKilled(MI, regB, MRI, TII); 1029 1030 if (TargetRegisterInfo::isVirtualRegister(regA)) 1031 ScanUses(regA, &*mbbi, Processed); 1032 1033 // Check if it is profitable to commute the operands. 1034 unsigned SrcOp1, SrcOp2; 1035 unsigned regC = 0; 1036 unsigned regCIdx = ~0U; 1037 bool TryCommute = false; 1038 bool AggressiveCommute = false; 1039 if (MI.isCommutable() && MI.getNumOperands() >= 3 && 1040 TII->findCommutedOpIndices(&MI, SrcOp1, SrcOp2)) { 1041 if (SrcIdx == SrcOp1) 1042 regCIdx = SrcOp2; 1043 else if (SrcIdx == SrcOp2) 1044 regCIdx = SrcOp1; 1045 1046 if (regCIdx != ~0U) { 1047 regC = MI.getOperand(regCIdx).getReg(); 1048 if (!regBKilled && isKilled(MI, regC, MRI, TII)) 1049 // If C dies but B does not, swap the B and C operands. 1050 // This makes the live ranges of A and C joinable. 1051 TryCommute = true; 1052 else if (isProfitableToCommute(regA, regB, regC, &MI, mbbi, Dist)) { 1053 TryCommute = true; 1054 AggressiveCommute = true; 1055 } 1056 } 1057 } 1058 1059 // If it's profitable to commute, try to do so. 1060 if (TryCommute && CommuteInstruction(mi, mbbi, regB, regC, Dist)) { 1061 ++NumCommuted; 1062 if (AggressiveCommute) 1063 ++NumAggrCommuted; 1064 return false; 1065 } 1066 1067 // If there is one more use of regB later in the same MBB, consider 1068 // re-schedule this MI below it. 1069 if (RescheduleMIBelowKill(mbbi, mi, nmi, regB)) { 1070 ++NumReSchedDowns; 1071 return true; 1072 } 1073 1074 if (MI.isConvertibleTo3Addr()) { 1075 // This instruction is potentially convertible to a true 1076 // three-address instruction. Check if it is profitable. 1077 if (!regBKilled || isProfitableToConv3Addr(regA, regB)) { 1078 // Try to convert it. 1079 if (ConvertInstTo3Addr(mi, nmi, mbbi, regA, regB, Dist)) { 1080 ++NumConvertedTo3Addr; 1081 return true; // Done with this instruction. 1082 } 1083 } 1084 } 1085 1086 // If there is one more use of regB later in the same MBB, consider 1087 // re-schedule it before this MI if it's legal. 1088 if (RescheduleKillAboveMI(mbbi, mi, nmi, regB)) { 1089 ++NumReSchedUps; 1090 return true; 1091 } 1092 1093 // If this is an instruction with a load folded into it, try unfolding 1094 // the load, e.g. avoid this: 1095 // movq %rdx, %rcx 1096 // addq (%rax), %rcx 1097 // in favor of this: 1098 // movq (%rax), %rcx 1099 // addq %rdx, %rcx 1100 // because it's preferable to schedule a load than a register copy. 1101 if (MI.mayLoad() && !regBKilled) { 1102 // Determine if a load can be unfolded. 1103 unsigned LoadRegIndex; 1104 unsigned NewOpc = 1105 TII->getOpcodeAfterMemoryUnfold(MI.getOpcode(), 1106 /*UnfoldLoad=*/true, 1107 /*UnfoldStore=*/false, 1108 &LoadRegIndex); 1109 if (NewOpc != 0) { 1110 const MCInstrDesc &UnfoldMCID = TII->get(NewOpc); 1111 if (UnfoldMCID.getNumDefs() == 1) { 1112 // Unfold the load. 1113 DEBUG(dbgs() << "2addr: UNFOLDING: " << MI); 1114 const TargetRegisterClass *RC = 1115 TRI->getAllocatableClass( 1116 TII->getRegClass(UnfoldMCID, LoadRegIndex, TRI, *MF)); 1117 unsigned Reg = MRI->createVirtualRegister(RC); 1118 SmallVector<MachineInstr *, 2> NewMIs; 1119 if (!TII->unfoldMemoryOperand(*MF, &MI, Reg, 1120 /*UnfoldLoad=*/true,/*UnfoldStore=*/false, 1121 NewMIs)) { 1122 DEBUG(dbgs() << "2addr: ABANDONING UNFOLD\n"); 1123 return false; 1124 } 1125 assert(NewMIs.size() == 2 && 1126 "Unfolded a load into multiple instructions!"); 1127 // The load was previously folded, so this is the only use. 1128 NewMIs[1]->addRegisterKilled(Reg, TRI); 1129 1130 // Tentatively insert the instructions into the block so that they 1131 // look "normal" to the transformation logic. 1132 mbbi->insert(mi, NewMIs[0]); 1133 mbbi->insert(mi, NewMIs[1]); 1134 1135 DEBUG(dbgs() << "2addr: NEW LOAD: " << *NewMIs[0] 1136 << "2addr: NEW INST: " << *NewMIs[1]); 1137 1138 // Transform the instruction, now that it no longer has a load. 1139 unsigned NewDstIdx = NewMIs[1]->findRegisterDefOperandIdx(regA); 1140 unsigned NewSrcIdx = NewMIs[1]->findRegisterUseOperandIdx(regB); 1141 MachineBasicBlock::iterator NewMI = NewMIs[1]; 1142 bool TransformSuccess = 1143 TryInstructionTransform(NewMI, mi, mbbi, 1144 NewSrcIdx, NewDstIdx, Dist, Processed); 1145 if (TransformSuccess || 1146 NewMIs[1]->getOperand(NewSrcIdx).isKill()) { 1147 // Success, or at least we made an improvement. Keep the unfolded 1148 // instructions and discard the original. 1149 if (LV) { 1150 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { 1151 MachineOperand &MO = MI.getOperand(i); 1152 if (MO.isReg() && 1153 TargetRegisterInfo::isVirtualRegister(MO.getReg())) { 1154 if (MO.isUse()) { 1155 if (MO.isKill()) { 1156 if (NewMIs[0]->killsRegister(MO.getReg())) 1157 LV->replaceKillInstruction(MO.getReg(), &MI, NewMIs[0]); 1158 else { 1159 assert(NewMIs[1]->killsRegister(MO.getReg()) && 1160 "Kill missing after load unfold!"); 1161 LV->replaceKillInstruction(MO.getReg(), &MI, NewMIs[1]); 1162 } 1163 } 1164 } else if (LV->removeVirtualRegisterDead(MO.getReg(), &MI)) { 1165 if (NewMIs[1]->registerDefIsDead(MO.getReg())) 1166 LV->addVirtualRegisterDead(MO.getReg(), NewMIs[1]); 1167 else { 1168 assert(NewMIs[0]->registerDefIsDead(MO.getReg()) && 1169 "Dead flag missing after load unfold!"); 1170 LV->addVirtualRegisterDead(MO.getReg(), NewMIs[0]); 1171 } 1172 } 1173 } 1174 } 1175 LV->addVirtualRegisterKilled(Reg, NewMIs[1]); 1176 } 1177 MI.eraseFromParent(); 1178 mi = NewMIs[1]; 1179 if (TransformSuccess) 1180 return true; 1181 } else { 1182 // Transforming didn't eliminate the tie and didn't lead to an 1183 // improvement. Clean up the unfolded instructions and keep the 1184 // original. 1185 DEBUG(dbgs() << "2addr: ABANDONING UNFOLD\n"); 1186 NewMIs[0]->eraseFromParent(); 1187 NewMIs[1]->eraseFromParent(); 1188 } 1189 } 1190 } 1191 } 1192 1193 return false; 1194} 1195 1196// Collect tied operands of MI that need to be handled. 1197// Rewrite trivial cases immediately. 1198// Return true if any tied operands where found, including the trivial ones. 1199bool TwoAddressInstructionPass:: 1200collectTiedOperands(MachineInstr *MI, TiedOperandMap &TiedOperands) { 1201 const MCInstrDesc &MCID = MI->getDesc(); 1202 bool AnyOps = false; 1203 unsigned NumOps = MI->getNumOperands(); 1204 1205 for (unsigned SrcIdx = 0; SrcIdx < NumOps; ++SrcIdx) { 1206 unsigned DstIdx = 0; 1207 if (!MI->isRegTiedToDefOperand(SrcIdx, &DstIdx)) 1208 continue; 1209 AnyOps = true; 1210 MachineOperand &SrcMO = MI->getOperand(SrcIdx); 1211 MachineOperand &DstMO = MI->getOperand(DstIdx); 1212 unsigned SrcReg = SrcMO.getReg(); 1213 unsigned DstReg = DstMO.getReg(); 1214 // Tied constraint already satisfied? 1215 if (SrcReg == DstReg) 1216 continue; 1217 1218 assert(SrcReg && SrcMO.isUse() && "two address instruction invalid"); 1219 1220 // Deal with <undef> uses immediately - simply rewrite the src operand. 1221 if (SrcMO.isUndef()) { 1222 // Constrain the DstReg register class if required. 1223 if (TargetRegisterInfo::isVirtualRegister(DstReg)) 1224 if (const TargetRegisterClass *RC = TII->getRegClass(MCID, SrcIdx, 1225 TRI, *MF)) 1226 MRI->constrainRegClass(DstReg, RC); 1227 SrcMO.setReg(DstReg); 1228 DEBUG(dbgs() << "\t\trewrite undef:\t" << *MI); 1229 continue; 1230 } 1231 TiedOperands[SrcReg].push_back(std::make_pair(SrcIdx, DstIdx)); 1232 } 1233 return AnyOps; 1234} 1235 1236// Process a list of tied MI operands that all use the same source register. 1237// The tied pairs are of the form (SrcIdx, DstIdx). 1238void 1239TwoAddressInstructionPass::processTiedPairs(MachineInstr *MI, 1240 TiedPairList &TiedPairs, 1241 unsigned &Dist) { 1242 bool IsEarlyClobber = false; 1243 bool RemovedKillFlag = false; 1244 bool AllUsesCopied = true; 1245 unsigned LastCopiedReg = 0; 1246 unsigned RegB = 0; 1247 for (unsigned tpi = 0, tpe = TiedPairs.size(); tpi != tpe; ++tpi) { 1248 unsigned SrcIdx = TiedPairs[tpi].first; 1249 unsigned DstIdx = TiedPairs[tpi].second; 1250 1251 const MachineOperand &DstMO = MI->getOperand(DstIdx); 1252 unsigned RegA = DstMO.getReg(); 1253 IsEarlyClobber |= DstMO.isEarlyClobber(); 1254 1255 // Grab RegB from the instruction because it may have changed if the 1256 // instruction was commuted. 1257 RegB = MI->getOperand(SrcIdx).getReg(); 1258 1259 if (RegA == RegB) { 1260 // The register is tied to multiple destinations (or else we would 1261 // not have continued this far), but this use of the register 1262 // already matches the tied destination. Leave it. 1263 AllUsesCopied = false; 1264 continue; 1265 } 1266 LastCopiedReg = RegA; 1267 1268 assert(TargetRegisterInfo::isVirtualRegister(RegB) && 1269 "cannot make instruction into two-address form"); 1270 1271#ifndef NDEBUG 1272 // First, verify that we don't have a use of "a" in the instruction 1273 // (a = b + a for example) because our transformation will not 1274 // work. This should never occur because we are in SSA form. 1275 for (unsigned i = 0; i != MI->getNumOperands(); ++i) 1276 assert(i == DstIdx || 1277 !MI->getOperand(i).isReg() || 1278 MI->getOperand(i).getReg() != RegA); 1279#endif 1280 1281 // Emit a copy. 1282 BuildMI(*MI->getParent(), MI, MI->getDebugLoc(), 1283 TII->get(TargetOpcode::COPY), RegA).addReg(RegB); 1284 1285 // Update DistanceMap. 1286 MachineBasicBlock::iterator PrevMI = MI; 1287 --PrevMI; 1288 DistanceMap.insert(std::make_pair(PrevMI, Dist)); 1289 DistanceMap[MI] = ++Dist; 1290 1291 SlotIndex CopyIdx; 1292 if (Indexes) 1293 CopyIdx = Indexes->insertMachineInstrInMaps(PrevMI).getRegSlot(); 1294 1295 DEBUG(dbgs() << "\t\tprepend:\t" << *PrevMI); 1296 1297 MachineOperand &MO = MI->getOperand(SrcIdx); 1298 assert(MO.isReg() && MO.getReg() == RegB && MO.isUse() && 1299 "inconsistent operand info for 2-reg pass"); 1300 if (MO.isKill()) { 1301 MO.setIsKill(false); 1302 RemovedKillFlag = true; 1303 } 1304 1305 // Make sure regA is a legal regclass for the SrcIdx operand. 1306 if (TargetRegisterInfo::isVirtualRegister(RegA) && 1307 TargetRegisterInfo::isVirtualRegister(RegB)) 1308 MRI->constrainRegClass(RegA, MRI->getRegClass(RegB)); 1309 1310 MO.setReg(RegA); 1311 1312 // Propagate SrcRegMap. 1313 SrcRegMap[RegA] = RegB; 1314 } 1315 1316 1317 if (AllUsesCopied) { 1318 if (!IsEarlyClobber) { 1319 // Replace other (un-tied) uses of regB with LastCopiedReg. 1320 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 1321 MachineOperand &MO = MI->getOperand(i); 1322 if (MO.isReg() && MO.getReg() == RegB && MO.isUse()) { 1323 if (MO.isKill()) { 1324 MO.setIsKill(false); 1325 RemovedKillFlag = true; 1326 } 1327 MO.setReg(LastCopiedReg); 1328 } 1329 } 1330 } 1331 1332 // Update live variables for regB. 1333 if (RemovedKillFlag && LV && LV->getVarInfo(RegB).removeKill(MI)) { 1334 MachineBasicBlock::iterator PrevMI = MI; 1335 --PrevMI; 1336 LV->addVirtualRegisterKilled(RegB, PrevMI); 1337 } 1338 1339 } else if (RemovedKillFlag) { 1340 // Some tied uses of regB matched their destination registers, so 1341 // regB is still used in this instruction, but a kill flag was 1342 // removed from a different tied use of regB, so now we need to add 1343 // a kill flag to one of the remaining uses of regB. 1344 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 1345 MachineOperand &MO = MI->getOperand(i); 1346 if (MO.isReg() && MO.getReg() == RegB && MO.isUse()) { 1347 MO.setIsKill(true); 1348 break; 1349 } 1350 } 1351 } 1352} 1353 1354/// runOnMachineFunction - Reduce two-address instructions to two operands. 1355/// 1356bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &Func) { 1357 MF = &Func; 1358 const TargetMachine &TM = MF->getTarget(); 1359 MRI = &MF->getRegInfo(); 1360 TII = TM.getInstrInfo(); 1361 TRI = TM.getRegisterInfo(); 1362 InstrItins = TM.getInstrItineraryData(); 1363 Indexes = getAnalysisIfAvailable<SlotIndexes>(); 1364 LV = getAnalysisIfAvailable<LiveVariables>(); 1365 LIS = getAnalysisIfAvailable<LiveIntervals>(); 1366 AA = &getAnalysis<AliasAnalysis>(); 1367 OptLevel = TM.getOptLevel(); 1368 1369 bool MadeChange = false; 1370 1371 DEBUG(dbgs() << "********** REWRITING TWO-ADDR INSTRS **********\n"); 1372 DEBUG(dbgs() << "********** Function: " 1373 << MF->getName() << '\n'); 1374 1375 // This pass takes the function out of SSA form. 1376 MRI->leaveSSA(); 1377 1378 TiedOperandMap TiedOperands; 1379 1380 SmallPtrSet<MachineInstr*, 8> Processed; 1381 for (MachineFunction::iterator mbbi = MF->begin(), mbbe = MF->end(); 1382 mbbi != mbbe; ++mbbi) { 1383 unsigned Dist = 0; 1384 DistanceMap.clear(); 1385 SrcRegMap.clear(); 1386 DstRegMap.clear(); 1387 Processed.clear(); 1388 for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end(); 1389 mi != me; ) { 1390 MachineBasicBlock::iterator nmi = llvm::next(mi); 1391 if (mi->isDebugValue()) { 1392 mi = nmi; 1393 continue; 1394 } 1395 1396 // Remember REG_SEQUENCE instructions, we'll deal with them later. 1397 if (mi->isRegSequence()) 1398 RegSequences.push_back(&*mi); 1399 1400 DistanceMap.insert(std::make_pair(mi, ++Dist)); 1401 1402 ProcessCopy(&*mi, &*mbbi, Processed); 1403 1404 // First scan through all the tied register uses in this instruction 1405 // and record a list of pairs of tied operands for each register. 1406 if (!collectTiedOperands(mi, TiedOperands)) { 1407 mi = nmi; 1408 continue; 1409 } 1410 1411 ++NumTwoAddressInstrs; 1412 MadeChange = true; 1413 DEBUG(dbgs() << '\t' << *mi); 1414 1415 // If the instruction has a single pair of tied operands, try some 1416 // transformations that may either eliminate the tied operands or 1417 // improve the opportunities for coalescing away the register copy. 1418 if (TiedOperands.size() == 1) { 1419 SmallVector<std::pair<unsigned, unsigned>, 4> &TiedPairs 1420 = TiedOperands.begin()->second; 1421 if (TiedPairs.size() == 1) { 1422 unsigned SrcIdx = TiedPairs[0].first; 1423 unsigned DstIdx = TiedPairs[0].second; 1424 unsigned SrcReg = mi->getOperand(SrcIdx).getReg(); 1425 unsigned DstReg = mi->getOperand(DstIdx).getReg(); 1426 if (SrcReg != DstReg && 1427 TryInstructionTransform(mi, nmi, mbbi, SrcIdx, DstIdx, Dist, 1428 Processed)) { 1429 // The tied operands have been eliminated or shifted further down the 1430 // block to ease elimination. Continue processing with 'nmi'. 1431 TiedOperands.clear(); 1432 mi = nmi; 1433 continue; 1434 } 1435 } 1436 } 1437 1438 // Now iterate over the information collected above. 1439 for (TiedOperandMap::iterator OI = TiedOperands.begin(), 1440 OE = TiedOperands.end(); OI != OE; ++OI) { 1441 processTiedPairs(mi, OI->second, Dist); 1442 DEBUG(dbgs() << "\t\trewrite to:\t" << *mi); 1443 } 1444 1445 // Rewrite INSERT_SUBREG as COPY now that we no longer need SSA form. 1446 if (mi->isInsertSubreg()) { 1447 // From %reg = INSERT_SUBREG %reg, %subreg, subidx 1448 // To %reg:subidx = COPY %subreg 1449 unsigned SubIdx = mi->getOperand(3).getImm(); 1450 mi->RemoveOperand(3); 1451 assert(mi->getOperand(0).getSubReg() == 0 && "Unexpected subreg idx"); 1452 mi->getOperand(0).setSubReg(SubIdx); 1453 mi->getOperand(0).setIsUndef(mi->getOperand(1).isUndef()); 1454 mi->RemoveOperand(1); 1455 mi->setDesc(TII->get(TargetOpcode::COPY)); 1456 DEBUG(dbgs() << "\t\tconvert to:\t" << *mi); 1457 } 1458 1459 // Clear TiedOperands here instead of at the top of the loop 1460 // since most instructions do not have tied operands. 1461 TiedOperands.clear(); 1462 mi = nmi; 1463 } 1464 } 1465 1466 // Eliminate REG_SEQUENCE instructions. Their whole purpose was to preseve 1467 // SSA form. It's now safe to de-SSA. 1468 MadeChange |= EliminateRegSequences(); 1469 1470 return MadeChange; 1471} 1472 1473static void UpdateRegSequenceSrcs(unsigned SrcReg, 1474 unsigned DstReg, unsigned SubIdx, 1475 MachineRegisterInfo *MRI, 1476 const TargetRegisterInfo &TRI) { 1477 for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(SrcReg), 1478 RE = MRI->reg_end(); RI != RE; ) { 1479 MachineOperand &MO = RI.getOperand(); 1480 ++RI; 1481 MO.substVirtReg(DstReg, SubIdx, TRI); 1482 } 1483} 1484 1485// Find the first def of Reg, assuming they are all in the same basic block. 1486static MachineInstr *findFirstDef(unsigned Reg, MachineRegisterInfo *MRI) { 1487 SmallPtrSet<MachineInstr*, 8> Defs; 1488 MachineInstr *First = 0; 1489 for (MachineRegisterInfo::def_iterator RI = MRI->def_begin(Reg); 1490 MachineInstr *MI = RI.skipInstruction(); Defs.insert(MI)) 1491 First = MI; 1492 if (!First) 1493 return 0; 1494 1495 MachineBasicBlock *MBB = First->getParent(); 1496 MachineBasicBlock::iterator A = First, B = First; 1497 bool Moving; 1498 do { 1499 Moving = false; 1500 if (A != MBB->begin()) { 1501 Moving = true; 1502 --A; 1503 if (Defs.erase(A)) First = A; 1504 } 1505 if (B != MBB->end()) { 1506 Defs.erase(B); 1507 ++B; 1508 Moving = true; 1509 } 1510 } while (Moving && !Defs.empty()); 1511 assert(Defs.empty() && "Instructions outside basic block!"); 1512 return First; 1513} 1514 1515static bool HasOtherRegSequenceUses(unsigned Reg, MachineInstr *RegSeq, 1516 MachineRegisterInfo *MRI) { 1517 for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg), 1518 UE = MRI->use_end(); UI != UE; ++UI) { 1519 MachineInstr *UseMI = &*UI; 1520 if (UseMI != RegSeq && UseMI->isRegSequence()) 1521 return true; 1522 } 1523 return false; 1524} 1525 1526/// EliminateRegSequences - Eliminate REG_SEQUENCE instructions as part 1527/// of the de-ssa process. This replaces sources of REG_SEQUENCE as 1528/// sub-register references of the register defined by REG_SEQUENCE. e.g. 1529/// 1530/// %reg1029<def>, %reg1030<def> = VLD1q16 %reg1024<kill>, ... 1531/// %reg1031<def> = REG_SEQUENCE %reg1029<kill>, 5, %reg1030<kill>, 6 1532/// => 1533/// %reg1031:5<def>, %reg1031:6<def> = VLD1q16 %reg1024<kill>, ... 1534bool TwoAddressInstructionPass::EliminateRegSequences() { 1535 if (RegSequences.empty()) 1536 return false; 1537 1538 for (unsigned i = 0, e = RegSequences.size(); i != e; ++i) { 1539 MachineInstr *MI = RegSequences[i]; 1540 unsigned DstReg = MI->getOperand(0).getReg(); 1541 if (MI->getOperand(0).getSubReg() || 1542 TargetRegisterInfo::isPhysicalRegister(DstReg) || 1543 !(MI->getNumOperands() & 1)) { 1544 DEBUG(dbgs() << "Illegal REG_SEQUENCE instruction:" << *MI); 1545 llvm_unreachable(0); 1546 } 1547 1548 bool IsImpDef = true; 1549 SmallVector<unsigned, 4> RealSrcs; 1550 SmallSet<unsigned, 4> Seen; 1551 for (unsigned i = 1, e = MI->getNumOperands(); i < e; i += 2) { 1552 // Nothing needs to be inserted for <undef> operands. 1553 if (MI->getOperand(i).isUndef()) { 1554 MI->getOperand(i).setReg(0); 1555 continue; 1556 } 1557 unsigned SrcReg = MI->getOperand(i).getReg(); 1558 unsigned SrcSubIdx = MI->getOperand(i).getSubReg(); 1559 unsigned SubIdx = MI->getOperand(i+1).getImm(); 1560 // DefMI of NULL means the value does not have a vreg in this block 1561 // i.e., its a physical register or a subreg. 1562 // In either case we force a copy to be generated. 1563 MachineInstr *DefMI = NULL; 1564 if (!MI->getOperand(i).getSubReg() && 1565 !TargetRegisterInfo::isPhysicalRegister(SrcReg)) { 1566 DefMI = MRI->getUniqueVRegDef(SrcReg); 1567 } 1568 1569 if (DefMI && DefMI->isImplicitDef()) { 1570 DefMI->eraseFromParent(); 1571 continue; 1572 } 1573 IsImpDef = false; 1574 1575 // Remember COPY sources. These might be candidate for coalescing. 1576 if (DefMI && DefMI->isCopy() && DefMI->getOperand(1).getSubReg()) 1577 RealSrcs.push_back(DefMI->getOperand(1).getReg()); 1578 1579 bool isKill = MI->getOperand(i).isKill(); 1580 if (!DefMI || !Seen.insert(SrcReg) || 1581 MI->getParent() != DefMI->getParent() || 1582 !isKill || HasOtherRegSequenceUses(SrcReg, MI, MRI) || 1583 !TRI->getMatchingSuperRegClass(MRI->getRegClass(DstReg), 1584 MRI->getRegClass(SrcReg), SubIdx)) { 1585 // REG_SEQUENCE cannot have duplicated operands, add a copy. 1586 // Also add an copy if the source is live-in the block. We don't want 1587 // to end up with a partial-redef of a livein, e.g. 1588 // BB0: 1589 // reg1051:10<def> = 1590 // ... 1591 // BB1: 1592 // ... = reg1051:10 1593 // BB2: 1594 // reg1051:9<def> = 1595 // LiveIntervalAnalysis won't like it. 1596 // 1597 // If the REG_SEQUENCE doesn't kill its source, keeping live variables 1598 // correctly up to date becomes very difficult. Insert a copy. 1599 1600 // Defer any kill flag to the last operand using SrcReg. Otherwise, we 1601 // might insert a COPY that uses SrcReg after is was killed. 1602 if (isKill) 1603 for (unsigned j = i + 2; j < e; j += 2) 1604 if (MI->getOperand(j).getReg() == SrcReg) { 1605 MI->getOperand(j).setIsKill(); 1606 isKill = false; 1607 break; 1608 } 1609 1610 MachineBasicBlock::iterator InsertLoc = MI; 1611 MachineInstr *CopyMI = BuildMI(*MI->getParent(), InsertLoc, 1612 MI->getDebugLoc(), TII->get(TargetOpcode::COPY)) 1613 .addReg(DstReg, RegState::Define, SubIdx) 1614 .addReg(SrcReg, getKillRegState(isKill), SrcSubIdx); 1615 MI->getOperand(i).setReg(0); 1616 if (LV && isKill && !TargetRegisterInfo::isPhysicalRegister(SrcReg)) 1617 LV->replaceKillInstruction(SrcReg, MI, CopyMI); 1618 DEBUG(dbgs() << "Inserted: " << *CopyMI); 1619 } 1620 } 1621 1622 for (unsigned i = 1, e = MI->getNumOperands(); i < e; i += 2) { 1623 unsigned SrcReg = MI->getOperand(i).getReg(); 1624 if (!SrcReg) continue; 1625 unsigned SubIdx = MI->getOperand(i+1).getImm(); 1626 UpdateRegSequenceSrcs(SrcReg, DstReg, SubIdx, MRI, *TRI); 1627 } 1628 1629 // Set <def,undef> flags on the first DstReg def in the basic block. 1630 // It marks the beginning of the live range. All the other defs are 1631 // read-modify-write. 1632 if (MachineInstr *Def = findFirstDef(DstReg, MRI)) { 1633 for (unsigned i = 0, e = Def->getNumOperands(); i != e; ++i) { 1634 MachineOperand &MO = Def->getOperand(i); 1635 if (MO.isReg() && MO.isDef() && MO.getReg() == DstReg) 1636 MO.setIsUndef(); 1637 } 1638 DEBUG(dbgs() << "First def: " << *Def); 1639 } 1640 1641 if (IsImpDef) { 1642 DEBUG(dbgs() << "Turned: " << *MI << " into an IMPLICIT_DEF"); 1643 MI->setDesc(TII->get(TargetOpcode::IMPLICIT_DEF)); 1644 for (int j = MI->getNumOperands() - 1, ee = 0; j > ee; --j) 1645 MI->RemoveOperand(j); 1646 } else { 1647 DEBUG(dbgs() << "Eliminated: " << *MI); 1648 MI->eraseFromParent(); 1649 } 1650 } 1651 1652 RegSequences.clear(); 1653 return true; 1654} 1655