1 //===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===// 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 transformation analyzes and transforms the induction variables (and 11 // computations derived from them) into forms suitable for efficient execution 12 // on the target. 13 // 14 // This pass performs a strength reduction on array references inside loops that 15 // have as one or more of their components the loop induction variable, it 16 // rewrites expressions to take advantage of scaled-index addressing modes 17 // available on the target, and it performs a variety of other optimizations 18 // related to loop induction variables. 19 // 20 // Terminology note: this code has a lot of handling for "post-increment" or 21 // "post-inc" users. This is not talking about post-increment addressing modes; 22 // it is instead talking about code like this: 23 // 24 // %i = phi [ 0, %entry ], [ %i.next, %latch ] 25 // ... 26 // %i.next = add %i, 1 27 // %c = icmp eq %i.next, %n 28 // 29 // The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however 30 // it's useful to think about these as the same register, with some uses using 31 // the value of the register before the add and some using it after. In this 32 // example, the icmp is a post-increment user, since it uses %i.next, which is 33 // the value of the induction variable after the increment. The other common 34 // case of post-increment users is users outside the loop. 35 // 36 // TODO: More sophistication in the way Formulae are generated and filtered. 37 // 38 // TODO: Handle multiple loops at a time. 39 // 40 // TODO: Should the addressing mode BaseGV be changed to a ConstantExpr instead 41 // of a GlobalValue? 42 // 43 // TODO: When truncation is free, truncate ICmp users' operands to make it a 44 // smaller encoding (on x86 at least). 45 // 46 // TODO: When a negated register is used by an add (such as in a list of 47 // multiple base registers, or as the increment expression in an addrec), 48 // we may not actually need both reg and (-1 * reg) in registers; the 49 // negation can be implemented by using a sub instead of an add. The 50 // lack of support for taking this into consideration when making 51 // register pressure decisions is partly worked around by the "Special" 52 // use kind. 53 // 54 //===----------------------------------------------------------------------===// 55 56 #include "llvm/Transforms/Scalar.h" 57 #include "llvm/ADT/DenseSet.h" 58 #include "llvm/ADT/Hashing.h" 59 #include "llvm/ADT/STLExtras.h" 60 #include "llvm/ADT/SetVector.h" 61 #include "llvm/ADT/SmallBitVector.h" 62 #include "llvm/Analysis/IVUsers.h" 63 #include "llvm/Analysis/LoopPass.h" 64 #include "llvm/Analysis/ScalarEvolutionExpander.h" 65 #include "llvm/Analysis/TargetTransformInfo.h" 66 #include "llvm/IR/Constants.h" 67 #include "llvm/IR/DerivedTypes.h" 68 #include "llvm/IR/Dominators.h" 69 #include "llvm/IR/Instructions.h" 70 #include "llvm/IR/IntrinsicInst.h" 71 #include "llvm/IR/Module.h" 72 #include "llvm/IR/ValueHandle.h" 73 #include "llvm/Support/CommandLine.h" 74 #include "llvm/Support/Debug.h" 75 #include "llvm/Support/raw_ostream.h" 76 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 77 #include "llvm/Transforms/Utils/Local.h" 78 #include <algorithm> 79 using namespace llvm; 80 81 #define DEBUG_TYPE "loop-reduce" 82 83 /// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for 84 /// bail out. This threshold is far beyond the number of users that LSR can 85 /// conceivably solve, so it should not affect generated code, but catches the 86 /// worst cases before LSR burns too much compile time and stack space. 87 static const unsigned MaxIVUsers = 200; 88 89 // Temporary flag to cleanup congruent phis after LSR phi expansion. 90 // It's currently disabled until we can determine whether it's truly useful or 91 // not. The flag should be removed after the v3.0 release. 92 // This is now needed for ivchains. 93 static cl::opt<bool> EnablePhiElim( 94 "enable-lsr-phielim", cl::Hidden, cl::init(true), 95 cl::desc("Enable LSR phi elimination")); 96 97 #ifndef NDEBUG 98 // Stress test IV chain generation. 99 static cl::opt<bool> StressIVChain( 100 "stress-ivchain", cl::Hidden, cl::init(false), 101 cl::desc("Stress test LSR IV chains")); 102 #else 103 static bool StressIVChain = false; 104 #endif 105 106 namespace { 107 108 struct MemAccessTy { 109 /// Used in situations where the accessed memory type is unknown. 110 static const unsigned UnknownAddressSpace = ~0u; 111 112 Type *MemTy; 113 unsigned AddrSpace; 114 115 MemAccessTy() : MemTy(nullptr), AddrSpace(UnknownAddressSpace) {} 116 117 MemAccessTy(Type *Ty, unsigned AS) : 118 MemTy(Ty), AddrSpace(AS) {} 119 120 bool operator==(MemAccessTy Other) const { 121 return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace; 122 } 123 124 bool operator!=(MemAccessTy Other) const { return !(*this == Other); } 125 126 static MemAccessTy getUnknown(LLVMContext &Ctx) { 127 return MemAccessTy(Type::getVoidTy(Ctx), UnknownAddressSpace); 128 } 129 }; 130 131 /// This class holds data which is used to order reuse candidates. 132 class RegSortData { 133 public: 134 /// This represents the set of LSRUse indices which reference 135 /// a particular register. 136 SmallBitVector UsedByIndices; 137 138 void print(raw_ostream &OS) const; 139 void dump() const; 140 }; 141 142 } 143 144 void RegSortData::print(raw_ostream &OS) const { 145 OS << "[NumUses=" << UsedByIndices.count() << ']'; 146 } 147 148 LLVM_DUMP_METHOD 149 void RegSortData::dump() const { 150 print(errs()); errs() << '\n'; 151 } 152 153 namespace { 154 155 /// Map register candidates to information about how they are used. 156 class RegUseTracker { 157 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy; 158 159 RegUsesTy RegUsesMap; 160 SmallVector<const SCEV *, 16> RegSequence; 161 162 public: 163 void countRegister(const SCEV *Reg, size_t LUIdx); 164 void dropRegister(const SCEV *Reg, size_t LUIdx); 165 void swapAndDropUse(size_t LUIdx, size_t LastLUIdx); 166 167 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const; 168 169 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const; 170 171 void clear(); 172 173 typedef SmallVectorImpl<const SCEV *>::iterator iterator; 174 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator; 175 iterator begin() { return RegSequence.begin(); } 176 iterator end() { return RegSequence.end(); } 177 const_iterator begin() const { return RegSequence.begin(); } 178 const_iterator end() const { return RegSequence.end(); } 179 }; 180 181 } 182 183 void 184 RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) { 185 std::pair<RegUsesTy::iterator, bool> Pair = 186 RegUsesMap.insert(std::make_pair(Reg, RegSortData())); 187 RegSortData &RSD = Pair.first->second; 188 if (Pair.second) 189 RegSequence.push_back(Reg); 190 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1)); 191 RSD.UsedByIndices.set(LUIdx); 192 } 193 194 void 195 RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) { 196 RegUsesTy::iterator It = RegUsesMap.find(Reg); 197 assert(It != RegUsesMap.end()); 198 RegSortData &RSD = It->second; 199 assert(RSD.UsedByIndices.size() > LUIdx); 200 RSD.UsedByIndices.reset(LUIdx); 201 } 202 203 void 204 RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) { 205 assert(LUIdx <= LastLUIdx); 206 207 // Update RegUses. The data structure is not optimized for this purpose; 208 // we must iterate through it and update each of the bit vectors. 209 for (auto &Pair : RegUsesMap) { 210 SmallBitVector &UsedByIndices = Pair.second.UsedByIndices; 211 if (LUIdx < UsedByIndices.size()) 212 UsedByIndices[LUIdx] = 213 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0; 214 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx)); 215 } 216 } 217 218 bool 219 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const { 220 RegUsesTy::const_iterator I = RegUsesMap.find(Reg); 221 if (I == RegUsesMap.end()) 222 return false; 223 const SmallBitVector &UsedByIndices = I->second.UsedByIndices; 224 int i = UsedByIndices.find_first(); 225 if (i == -1) return false; 226 if ((size_t)i != LUIdx) return true; 227 return UsedByIndices.find_next(i) != -1; 228 } 229 230 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const { 231 RegUsesTy::const_iterator I = RegUsesMap.find(Reg); 232 assert(I != RegUsesMap.end() && "Unknown register!"); 233 return I->second.UsedByIndices; 234 } 235 236 void RegUseTracker::clear() { 237 RegUsesMap.clear(); 238 RegSequence.clear(); 239 } 240 241 namespace { 242 243 /// This class holds information that describes a formula for computing 244 /// satisfying a use. It may include broken-out immediates and scaled registers. 245 struct Formula { 246 /// Global base address used for complex addressing. 247 GlobalValue *BaseGV; 248 249 /// Base offset for complex addressing. 250 int64_t BaseOffset; 251 252 /// Whether any complex addressing has a base register. 253 bool HasBaseReg; 254 255 /// The scale of any complex addressing. 256 int64_t Scale; 257 258 /// The list of "base" registers for this use. When this is non-empty. The 259 /// canonical representation of a formula is 260 /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and 261 /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty(). 262 /// #1 enforces that the scaled register is always used when at least two 263 /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2. 264 /// #2 enforces that 1 * reg is reg. 265 /// This invariant can be temporarly broken while building a formula. 266 /// However, every formula inserted into the LSRInstance must be in canonical 267 /// form. 268 SmallVector<const SCEV *, 4> BaseRegs; 269 270 /// The 'scaled' register for this use. This should be non-null when Scale is 271 /// not zero. 272 const SCEV *ScaledReg; 273 274 /// An additional constant offset which added near the use. This requires a 275 /// temporary register, but the offset itself can live in an add immediate 276 /// field rather than a register. 277 int64_t UnfoldedOffset; 278 279 Formula() 280 : BaseGV(nullptr), BaseOffset(0), HasBaseReg(false), Scale(0), 281 ScaledReg(nullptr), UnfoldedOffset(0) {} 282 283 void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE); 284 285 bool isCanonical() const; 286 287 void canonicalize(); 288 289 bool unscale(); 290 291 size_t getNumRegs() const; 292 Type *getType() const; 293 294 void deleteBaseReg(const SCEV *&S); 295 296 bool referencesReg(const SCEV *S) const; 297 bool hasRegsUsedByUsesOtherThan(size_t LUIdx, 298 const RegUseTracker &RegUses) const; 299 300 void print(raw_ostream &OS) const; 301 void dump() const; 302 }; 303 304 } 305 306 /// Recursion helper for initialMatch. 307 static void DoInitialMatch(const SCEV *S, Loop *L, 308 SmallVectorImpl<const SCEV *> &Good, 309 SmallVectorImpl<const SCEV *> &Bad, 310 ScalarEvolution &SE) { 311 // Collect expressions which properly dominate the loop header. 312 if (SE.properlyDominates(S, L->getHeader())) { 313 Good.push_back(S); 314 return; 315 } 316 317 // Look at add operands. 318 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 319 for (const SCEV *S : Add->operands()) 320 DoInitialMatch(S, L, Good, Bad, SE); 321 return; 322 } 323 324 // Look at addrec operands. 325 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) 326 if (!AR->getStart()->isZero()) { 327 DoInitialMatch(AR->getStart(), L, Good, Bad, SE); 328 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0), 329 AR->getStepRecurrence(SE), 330 // FIXME: AR->getNoWrapFlags() 331 AR->getLoop(), SCEV::FlagAnyWrap), 332 L, Good, Bad, SE); 333 return; 334 } 335 336 // Handle a multiplication by -1 (negation) if it didn't fold. 337 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) 338 if (Mul->getOperand(0)->isAllOnesValue()) { 339 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end()); 340 const SCEV *NewMul = SE.getMulExpr(Ops); 341 342 SmallVector<const SCEV *, 4> MyGood; 343 SmallVector<const SCEV *, 4> MyBad; 344 DoInitialMatch(NewMul, L, MyGood, MyBad, SE); 345 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue( 346 SE.getEffectiveSCEVType(NewMul->getType()))); 347 for (const SCEV *S : MyGood) 348 Good.push_back(SE.getMulExpr(NegOne, S)); 349 for (const SCEV *S : MyBad) 350 Bad.push_back(SE.getMulExpr(NegOne, S)); 351 return; 352 } 353 354 // Ok, we can't do anything interesting. Just stuff the whole thing into a 355 // register and hope for the best. 356 Bad.push_back(S); 357 } 358 359 /// Incorporate loop-variant parts of S into this Formula, attempting to keep 360 /// all loop-invariant and loop-computable values in a single base register. 361 void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) { 362 SmallVector<const SCEV *, 4> Good; 363 SmallVector<const SCEV *, 4> Bad; 364 DoInitialMatch(S, L, Good, Bad, SE); 365 if (!Good.empty()) { 366 const SCEV *Sum = SE.getAddExpr(Good); 367 if (!Sum->isZero()) 368 BaseRegs.push_back(Sum); 369 HasBaseReg = true; 370 } 371 if (!Bad.empty()) { 372 const SCEV *Sum = SE.getAddExpr(Bad); 373 if (!Sum->isZero()) 374 BaseRegs.push_back(Sum); 375 HasBaseReg = true; 376 } 377 canonicalize(); 378 } 379 380 /// \brief Check whether or not this formula statisfies the canonical 381 /// representation. 382 /// \see Formula::BaseRegs. 383 bool Formula::isCanonical() const { 384 if (ScaledReg) 385 return Scale != 1 || !BaseRegs.empty(); 386 return BaseRegs.size() <= 1; 387 } 388 389 /// \brief Helper method to morph a formula into its canonical representation. 390 /// \see Formula::BaseRegs. 391 /// Every formula having more than one base register, must use the ScaledReg 392 /// field. Otherwise, we would have to do special cases everywhere in LSR 393 /// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ... 394 /// On the other hand, 1*reg should be canonicalized into reg. 395 void Formula::canonicalize() { 396 if (isCanonical()) 397 return; 398 // So far we did not need this case. This is easy to implement but it is 399 // useless to maintain dead code. Beside it could hurt compile time. 400 assert(!BaseRegs.empty() && "1*reg => reg, should not be needed."); 401 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg. 402 ScaledReg = BaseRegs.back(); 403 BaseRegs.pop_back(); 404 Scale = 1; 405 size_t BaseRegsSize = BaseRegs.size(); 406 size_t Try = 0; 407 // If ScaledReg is an invariant, try to find a variant expression. 408 while (Try < BaseRegsSize && !isa<SCEVAddRecExpr>(ScaledReg)) 409 std::swap(ScaledReg, BaseRegs[Try++]); 410 } 411 412 /// \brief Get rid of the scale in the formula. 413 /// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2. 414 /// \return true if it was possible to get rid of the scale, false otherwise. 415 /// \note After this operation the formula may not be in the canonical form. 416 bool Formula::unscale() { 417 if (Scale != 1) 418 return false; 419 Scale = 0; 420 BaseRegs.push_back(ScaledReg); 421 ScaledReg = nullptr; 422 return true; 423 } 424 425 /// Return the total number of register operands used by this formula. This does 426 /// not include register uses implied by non-constant addrec strides. 427 size_t Formula::getNumRegs() const { 428 return !!ScaledReg + BaseRegs.size(); 429 } 430 431 /// Return the type of this formula, if it has one, or null otherwise. This type 432 /// is meaningless except for the bit size. 433 Type *Formula::getType() const { 434 return !BaseRegs.empty() ? BaseRegs.front()->getType() : 435 ScaledReg ? ScaledReg->getType() : 436 BaseGV ? BaseGV->getType() : 437 nullptr; 438 } 439 440 /// Delete the given base reg from the BaseRegs list. 441 void Formula::deleteBaseReg(const SCEV *&S) { 442 if (&S != &BaseRegs.back()) 443 std::swap(S, BaseRegs.back()); 444 BaseRegs.pop_back(); 445 } 446 447 /// Test if this formula references the given register. 448 bool Formula::referencesReg(const SCEV *S) const { 449 return S == ScaledReg || 450 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end(); 451 } 452 453 /// Test whether this formula uses registers which are used by uses other than 454 /// the use with the given index. 455 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx, 456 const RegUseTracker &RegUses) const { 457 if (ScaledReg) 458 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx)) 459 return true; 460 for (const SCEV *BaseReg : BaseRegs) 461 if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx)) 462 return true; 463 return false; 464 } 465 466 void Formula::print(raw_ostream &OS) const { 467 bool First = true; 468 if (BaseGV) { 469 if (!First) OS << " + "; else First = false; 470 BaseGV->printAsOperand(OS, /*PrintType=*/false); 471 } 472 if (BaseOffset != 0) { 473 if (!First) OS << " + "; else First = false; 474 OS << BaseOffset; 475 } 476 for (const SCEV *BaseReg : BaseRegs) { 477 if (!First) OS << " + "; else First = false; 478 OS << "reg(" << *BaseReg << ')'; 479 } 480 if (HasBaseReg && BaseRegs.empty()) { 481 if (!First) OS << " + "; else First = false; 482 OS << "**error: HasBaseReg**"; 483 } else if (!HasBaseReg && !BaseRegs.empty()) { 484 if (!First) OS << " + "; else First = false; 485 OS << "**error: !HasBaseReg**"; 486 } 487 if (Scale != 0) { 488 if (!First) OS << " + "; else First = false; 489 OS << Scale << "*reg("; 490 if (ScaledReg) 491 OS << *ScaledReg; 492 else 493 OS << "<unknown>"; 494 OS << ')'; 495 } 496 if (UnfoldedOffset != 0) { 497 if (!First) OS << " + "; 498 OS << "imm(" << UnfoldedOffset << ')'; 499 } 500 } 501 502 LLVM_DUMP_METHOD 503 void Formula::dump() const { 504 print(errs()); errs() << '\n'; 505 } 506 507 /// Return true if the given addrec can be sign-extended without changing its 508 /// value. 509 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) { 510 Type *WideTy = 511 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1); 512 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy)); 513 } 514 515 /// Return true if the given add can be sign-extended without changing its 516 /// value. 517 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) { 518 Type *WideTy = 519 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1); 520 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy)); 521 } 522 523 /// Return true if the given mul can be sign-extended without changing its 524 /// value. 525 static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) { 526 Type *WideTy = 527 IntegerType::get(SE.getContext(), 528 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands()); 529 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy)); 530 } 531 532 /// Return an expression for LHS /s RHS, if it can be determined and if the 533 /// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits 534 /// is true, expressions like (X * Y) /s Y are simplified to Y, ignoring that 535 /// the multiplication may overflow, which is useful when the result will be 536 /// used in a context where the most significant bits are ignored. 537 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS, 538 ScalarEvolution &SE, 539 bool IgnoreSignificantBits = false) { 540 // Handle the trivial case, which works for any SCEV type. 541 if (LHS == RHS) 542 return SE.getConstant(LHS->getType(), 1); 543 544 // Handle a few RHS special cases. 545 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS); 546 if (RC) { 547 const APInt &RA = RC->getAPInt(); 548 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do 549 // some folding. 550 if (RA.isAllOnesValue()) 551 return SE.getMulExpr(LHS, RC); 552 // Handle x /s 1 as x. 553 if (RA == 1) 554 return LHS; 555 } 556 557 // Check for a division of a constant by a constant. 558 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) { 559 if (!RC) 560 return nullptr; 561 const APInt &LA = C->getAPInt(); 562 const APInt &RA = RC->getAPInt(); 563 if (LA.srem(RA) != 0) 564 return nullptr; 565 return SE.getConstant(LA.sdiv(RA)); 566 } 567 568 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow. 569 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) { 570 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) { 571 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE, 572 IgnoreSignificantBits); 573 if (!Step) return nullptr; 574 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE, 575 IgnoreSignificantBits); 576 if (!Start) return nullptr; 577 // FlagNW is independent of the start value, step direction, and is 578 // preserved with smaller magnitude steps. 579 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW) 580 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap); 581 } 582 return nullptr; 583 } 584 585 // Distribute the sdiv over add operands, if the add doesn't overflow. 586 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) { 587 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) { 588 SmallVector<const SCEV *, 8> Ops; 589 for (const SCEV *S : Add->operands()) { 590 const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits); 591 if (!Op) return nullptr; 592 Ops.push_back(Op); 593 } 594 return SE.getAddExpr(Ops); 595 } 596 return nullptr; 597 } 598 599 // Check for a multiply operand that we can pull RHS out of. 600 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) { 601 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) { 602 SmallVector<const SCEV *, 4> Ops; 603 bool Found = false; 604 for (const SCEV *S : Mul->operands()) { 605 if (!Found) 606 if (const SCEV *Q = getExactSDiv(S, RHS, SE, 607 IgnoreSignificantBits)) { 608 S = Q; 609 Found = true; 610 } 611 Ops.push_back(S); 612 } 613 return Found ? SE.getMulExpr(Ops) : nullptr; 614 } 615 return nullptr; 616 } 617 618 // Otherwise we don't know. 619 return nullptr; 620 } 621 622 /// If S involves the addition of a constant integer value, return that integer 623 /// value, and mutate S to point to a new SCEV with that value excluded. 624 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) { 625 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) { 626 if (C->getAPInt().getMinSignedBits() <= 64) { 627 S = SE.getConstant(C->getType(), 0); 628 return C->getValue()->getSExtValue(); 629 } 630 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 631 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); 632 int64_t Result = ExtractImmediate(NewOps.front(), SE); 633 if (Result != 0) 634 S = SE.getAddExpr(NewOps); 635 return Result; 636 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 637 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); 638 int64_t Result = ExtractImmediate(NewOps.front(), SE); 639 if (Result != 0) 640 S = SE.getAddRecExpr(NewOps, AR->getLoop(), 641 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW) 642 SCEV::FlagAnyWrap); 643 return Result; 644 } 645 return 0; 646 } 647 648 /// If S involves the addition of a GlobalValue address, return that symbol, and 649 /// mutate S to point to a new SCEV with that value excluded. 650 static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) { 651 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { 652 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) { 653 S = SE.getConstant(GV->getType(), 0); 654 return GV; 655 } 656 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 657 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); 658 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE); 659 if (Result) 660 S = SE.getAddExpr(NewOps); 661 return Result; 662 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 663 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); 664 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE); 665 if (Result) 666 S = SE.getAddRecExpr(NewOps, AR->getLoop(), 667 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW) 668 SCEV::FlagAnyWrap); 669 return Result; 670 } 671 return nullptr; 672 } 673 674 /// Returns true if the specified instruction is using the specified value as an 675 /// address. 676 static bool isAddressUse(Instruction *Inst, Value *OperandVal) { 677 bool isAddress = isa<LoadInst>(Inst); 678 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 679 if (SI->getOperand(1) == OperandVal) 680 isAddress = true; 681 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 682 // Addressing modes can also be folded into prefetches and a variety 683 // of intrinsics. 684 switch (II->getIntrinsicID()) { 685 default: break; 686 case Intrinsic::prefetch: 687 if (II->getArgOperand(0) == OperandVal) 688 isAddress = true; 689 break; 690 } 691 } 692 return isAddress; 693 } 694 695 /// Return the type of the memory being accessed. 696 static MemAccessTy getAccessType(const Instruction *Inst) { 697 MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace); 698 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 699 AccessTy.MemTy = SI->getOperand(0)->getType(); 700 AccessTy.AddrSpace = SI->getPointerAddressSpace(); 701 } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) { 702 AccessTy.AddrSpace = LI->getPointerAddressSpace(); 703 } 704 705 // All pointers have the same requirements, so canonicalize them to an 706 // arbitrary pointer type to minimize variation. 707 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy)) 708 AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1), 709 PTy->getAddressSpace()); 710 711 return AccessTy; 712 } 713 714 /// Return true if this AddRec is already a phi in its loop. 715 static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) { 716 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin(); 717 PHINode *PN = dyn_cast<PHINode>(I); ++I) { 718 if (SE.isSCEVable(PN->getType()) && 719 (SE.getEffectiveSCEVType(PN->getType()) == 720 SE.getEffectiveSCEVType(AR->getType())) && 721 SE.getSCEV(PN) == AR) 722 return true; 723 } 724 return false; 725 } 726 727 /// Check if expanding this expression is likely to incur significant cost. This 728 /// is tricky because SCEV doesn't track which expressions are actually computed 729 /// by the current IR. 730 /// 731 /// We currently allow expansion of IV increments that involve adds, 732 /// multiplication by constants, and AddRecs from existing phis. 733 /// 734 /// TODO: Allow UDivExpr if we can find an existing IV increment that is an 735 /// obvious multiple of the UDivExpr. 736 static bool isHighCostExpansion(const SCEV *S, 737 SmallPtrSetImpl<const SCEV*> &Processed, 738 ScalarEvolution &SE) { 739 // Zero/One operand expressions 740 switch (S->getSCEVType()) { 741 case scUnknown: 742 case scConstant: 743 return false; 744 case scTruncate: 745 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(), 746 Processed, SE); 747 case scZeroExtend: 748 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(), 749 Processed, SE); 750 case scSignExtend: 751 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(), 752 Processed, SE); 753 } 754 755 if (!Processed.insert(S).second) 756 return false; 757 758 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 759 for (const SCEV *S : Add->operands()) { 760 if (isHighCostExpansion(S, Processed, SE)) 761 return true; 762 } 763 return false; 764 } 765 766 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) { 767 if (Mul->getNumOperands() == 2) { 768 // Multiplication by a constant is ok 769 if (isa<SCEVConstant>(Mul->getOperand(0))) 770 return isHighCostExpansion(Mul->getOperand(1), Processed, SE); 771 772 // If we have the value of one operand, check if an existing 773 // multiplication already generates this expression. 774 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) { 775 Value *UVal = U->getValue(); 776 for (User *UR : UVal->users()) { 777 // If U is a constant, it may be used by a ConstantExpr. 778 Instruction *UI = dyn_cast<Instruction>(UR); 779 if (UI && UI->getOpcode() == Instruction::Mul && 780 SE.isSCEVable(UI->getType())) { 781 return SE.getSCEV(UI) == Mul; 782 } 783 } 784 } 785 } 786 } 787 788 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 789 if (isExistingPhi(AR, SE)) 790 return false; 791 } 792 793 // Fow now, consider any other type of expression (div/mul/min/max) high cost. 794 return true; 795 } 796 797 /// If any of the instructions is the specified set are trivially dead, delete 798 /// them and see if this makes any of their operands subsequently dead. 799 static bool 800 DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) { 801 bool Changed = false; 802 803 while (!DeadInsts.empty()) { 804 Value *V = DeadInsts.pop_back_val(); 805 Instruction *I = dyn_cast_or_null<Instruction>(V); 806 807 if (!I || !isInstructionTriviallyDead(I)) 808 continue; 809 810 for (Use &O : I->operands()) 811 if (Instruction *U = dyn_cast<Instruction>(O)) { 812 O = nullptr; 813 if (U->use_empty()) 814 DeadInsts.emplace_back(U); 815 } 816 817 I->eraseFromParent(); 818 Changed = true; 819 } 820 821 return Changed; 822 } 823 824 namespace { 825 class LSRUse; 826 } 827 828 /// \brief Check if the addressing mode defined by \p F is completely 829 /// folded in \p LU at isel time. 830 /// This includes address-mode folding and special icmp tricks. 831 /// This function returns true if \p LU can accommodate what \p F 832 /// defines and up to 1 base + 1 scaled + offset. 833 /// In other words, if \p F has several base registers, this function may 834 /// still return true. Therefore, users still need to account for 835 /// additional base registers and/or unfolded offsets to derive an 836 /// accurate cost model. 837 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, 838 const LSRUse &LU, const Formula &F); 839 // Get the cost of the scaling factor used in F for LU. 840 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI, 841 const LSRUse &LU, const Formula &F); 842 843 namespace { 844 845 /// This class is used to measure and compare candidate formulae. 846 class Cost { 847 /// TODO: Some of these could be merged. Also, a lexical ordering 848 /// isn't always optimal. 849 unsigned NumRegs; 850 unsigned AddRecCost; 851 unsigned NumIVMuls; 852 unsigned NumBaseAdds; 853 unsigned ImmCost; 854 unsigned SetupCost; 855 unsigned ScaleCost; 856 857 public: 858 Cost() 859 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0), 860 SetupCost(0), ScaleCost(0) {} 861 862 bool operator<(const Cost &Other) const; 863 864 void Lose(); 865 866 #ifndef NDEBUG 867 // Once any of the metrics loses, they must all remain losers. 868 bool isValid() { 869 return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds 870 | ImmCost | SetupCost | ScaleCost) != ~0u) 871 || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds 872 & ImmCost & SetupCost & ScaleCost) == ~0u); 873 } 874 #endif 875 876 bool isLoser() { 877 assert(isValid() && "invalid cost"); 878 return NumRegs == ~0u; 879 } 880 881 void RateFormula(const TargetTransformInfo &TTI, 882 const Formula &F, 883 SmallPtrSetImpl<const SCEV *> &Regs, 884 const DenseSet<const SCEV *> &VisitedRegs, 885 const Loop *L, 886 const SmallVectorImpl<int64_t> &Offsets, 887 ScalarEvolution &SE, DominatorTree &DT, 888 const LSRUse &LU, 889 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr); 890 891 void print(raw_ostream &OS) const; 892 void dump() const; 893 894 private: 895 void RateRegister(const SCEV *Reg, 896 SmallPtrSetImpl<const SCEV *> &Regs, 897 const Loop *L, 898 ScalarEvolution &SE, DominatorTree &DT); 899 void RatePrimaryRegister(const SCEV *Reg, 900 SmallPtrSetImpl<const SCEV *> &Regs, 901 const Loop *L, 902 ScalarEvolution &SE, DominatorTree &DT, 903 SmallPtrSetImpl<const SCEV *> *LoserRegs); 904 }; 905 906 } 907 908 /// Tally up interesting quantities from the given register. 909 void Cost::RateRegister(const SCEV *Reg, 910 SmallPtrSetImpl<const SCEV *> &Regs, 911 const Loop *L, 912 ScalarEvolution &SE, DominatorTree &DT) { 913 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) { 914 // If this is an addrec for another loop, don't second-guess its addrec phi 915 // nodes. LSR isn't currently smart enough to reason about more than one 916 // loop at a time. LSR has already run on inner loops, will not run on outer 917 // loops, and cannot be expected to change sibling loops. 918 if (AR->getLoop() != L) { 919 // If the AddRec exists, consider it's register free and leave it alone. 920 if (isExistingPhi(AR, SE)) 921 return; 922 923 // Otherwise, do not consider this formula at all. 924 Lose(); 925 return; 926 } 927 AddRecCost += 1; /// TODO: This should be a function of the stride. 928 929 // Add the step value register, if it needs one. 930 // TODO: The non-affine case isn't precisely modeled here. 931 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) { 932 if (!Regs.count(AR->getOperand(1))) { 933 RateRegister(AR->getOperand(1), Regs, L, SE, DT); 934 if (isLoser()) 935 return; 936 } 937 } 938 } 939 ++NumRegs; 940 941 // Rough heuristic; favor registers which don't require extra setup 942 // instructions in the preheader. 943 if (!isa<SCEVUnknown>(Reg) && 944 !isa<SCEVConstant>(Reg) && 945 !(isa<SCEVAddRecExpr>(Reg) && 946 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) || 947 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart())))) 948 ++SetupCost; 949 950 NumIVMuls += isa<SCEVMulExpr>(Reg) && 951 SE.hasComputableLoopEvolution(Reg, L); 952 } 953 954 /// Record this register in the set. If we haven't seen it before, rate 955 /// it. Optional LoserRegs provides a way to declare any formula that refers to 956 /// one of those regs an instant loser. 957 void Cost::RatePrimaryRegister(const SCEV *Reg, 958 SmallPtrSetImpl<const SCEV *> &Regs, 959 const Loop *L, 960 ScalarEvolution &SE, DominatorTree &DT, 961 SmallPtrSetImpl<const SCEV *> *LoserRegs) { 962 if (LoserRegs && LoserRegs->count(Reg)) { 963 Lose(); 964 return; 965 } 966 if (Regs.insert(Reg).second) { 967 RateRegister(Reg, Regs, L, SE, DT); 968 if (LoserRegs && isLoser()) 969 LoserRegs->insert(Reg); 970 } 971 } 972 973 void Cost::RateFormula(const TargetTransformInfo &TTI, 974 const Formula &F, 975 SmallPtrSetImpl<const SCEV *> &Regs, 976 const DenseSet<const SCEV *> &VisitedRegs, 977 const Loop *L, 978 const SmallVectorImpl<int64_t> &Offsets, 979 ScalarEvolution &SE, DominatorTree &DT, 980 const LSRUse &LU, 981 SmallPtrSetImpl<const SCEV *> *LoserRegs) { 982 assert(F.isCanonical() && "Cost is accurate only for canonical formula"); 983 // Tally up the registers. 984 if (const SCEV *ScaledReg = F.ScaledReg) { 985 if (VisitedRegs.count(ScaledReg)) { 986 Lose(); 987 return; 988 } 989 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs); 990 if (isLoser()) 991 return; 992 } 993 for (const SCEV *BaseReg : F.BaseRegs) { 994 if (VisitedRegs.count(BaseReg)) { 995 Lose(); 996 return; 997 } 998 RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs); 999 if (isLoser()) 1000 return; 1001 } 1002 1003 // Determine how many (unfolded) adds we'll need inside the loop. 1004 size_t NumBaseParts = F.getNumRegs(); 1005 if (NumBaseParts > 1) 1006 // Do not count the base and a possible second register if the target 1007 // allows to fold 2 registers. 1008 NumBaseAdds += 1009 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(TTI, LU, F))); 1010 NumBaseAdds += (F.UnfoldedOffset != 0); 1011 1012 // Accumulate non-free scaling amounts. 1013 ScaleCost += getScalingFactorCost(TTI, LU, F); 1014 1015 // Tally up the non-zero immediates. 1016 for (int64_t O : Offsets) { 1017 int64_t Offset = (uint64_t)O + F.BaseOffset; 1018 if (F.BaseGV) 1019 ImmCost += 64; // Handle symbolic values conservatively. 1020 // TODO: This should probably be the pointer size. 1021 else if (Offset != 0) 1022 ImmCost += APInt(64, Offset, true).getMinSignedBits(); 1023 } 1024 assert(isValid() && "invalid cost"); 1025 } 1026 1027 /// Set this cost to a losing value. 1028 void Cost::Lose() { 1029 NumRegs = ~0u; 1030 AddRecCost = ~0u; 1031 NumIVMuls = ~0u; 1032 NumBaseAdds = ~0u; 1033 ImmCost = ~0u; 1034 SetupCost = ~0u; 1035 ScaleCost = ~0u; 1036 } 1037 1038 /// Choose the lower cost. 1039 bool Cost::operator<(const Cost &Other) const { 1040 return std::tie(NumRegs, AddRecCost, NumIVMuls, NumBaseAdds, ScaleCost, 1041 ImmCost, SetupCost) < 1042 std::tie(Other.NumRegs, Other.AddRecCost, Other.NumIVMuls, 1043 Other.NumBaseAdds, Other.ScaleCost, Other.ImmCost, 1044 Other.SetupCost); 1045 } 1046 1047 void Cost::print(raw_ostream &OS) const { 1048 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s"); 1049 if (AddRecCost != 0) 1050 OS << ", with addrec cost " << AddRecCost; 1051 if (NumIVMuls != 0) 1052 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s"); 1053 if (NumBaseAdds != 0) 1054 OS << ", plus " << NumBaseAdds << " base add" 1055 << (NumBaseAdds == 1 ? "" : "s"); 1056 if (ScaleCost != 0) 1057 OS << ", plus " << ScaleCost << " scale cost"; 1058 if (ImmCost != 0) 1059 OS << ", plus " << ImmCost << " imm cost"; 1060 if (SetupCost != 0) 1061 OS << ", plus " << SetupCost << " setup cost"; 1062 } 1063 1064 LLVM_DUMP_METHOD 1065 void Cost::dump() const { 1066 print(errs()); errs() << '\n'; 1067 } 1068 1069 namespace { 1070 1071 /// An operand value in an instruction which is to be replaced with some 1072 /// equivalent, possibly strength-reduced, replacement. 1073 struct LSRFixup { 1074 /// The instruction which will be updated. 1075 Instruction *UserInst; 1076 1077 /// The operand of the instruction which will be replaced. The operand may be 1078 /// used more than once; every instance will be replaced. 1079 Value *OperandValToReplace; 1080 1081 /// If this user is to use the post-incremented value of an induction 1082 /// variable, this variable is non-null and holds the loop associated with the 1083 /// induction variable. 1084 PostIncLoopSet PostIncLoops; 1085 1086 /// The index of the LSRUse describing the expression which this fixup needs, 1087 /// minus an offset (below). 1088 size_t LUIdx; 1089 1090 /// A constant offset to be added to the LSRUse expression. This allows 1091 /// multiple fixups to share the same LSRUse with different offsets, for 1092 /// example in an unrolled loop. 1093 int64_t Offset; 1094 1095 bool isUseFullyOutsideLoop(const Loop *L) const; 1096 1097 LSRFixup(); 1098 1099 void print(raw_ostream &OS) const; 1100 void dump() const; 1101 }; 1102 1103 } 1104 1105 LSRFixup::LSRFixup() 1106 : UserInst(nullptr), OperandValToReplace(nullptr), LUIdx(~size_t(0)), 1107 Offset(0) {} 1108 1109 /// Test whether this fixup always uses its value outside of the given loop. 1110 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const { 1111 // PHI nodes use their value in their incoming blocks. 1112 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) { 1113 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 1114 if (PN->getIncomingValue(i) == OperandValToReplace && 1115 L->contains(PN->getIncomingBlock(i))) 1116 return false; 1117 return true; 1118 } 1119 1120 return !L->contains(UserInst); 1121 } 1122 1123 void LSRFixup::print(raw_ostream &OS) const { 1124 OS << "UserInst="; 1125 // Store is common and interesting enough to be worth special-casing. 1126 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) { 1127 OS << "store "; 1128 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false); 1129 } else if (UserInst->getType()->isVoidTy()) 1130 OS << UserInst->getOpcodeName(); 1131 else 1132 UserInst->printAsOperand(OS, /*PrintType=*/false); 1133 1134 OS << ", OperandValToReplace="; 1135 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false); 1136 1137 for (const Loop *PIL : PostIncLoops) { 1138 OS << ", PostIncLoop="; 1139 PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false); 1140 } 1141 1142 if (LUIdx != ~size_t(0)) 1143 OS << ", LUIdx=" << LUIdx; 1144 1145 if (Offset != 0) 1146 OS << ", Offset=" << Offset; 1147 } 1148 1149 LLVM_DUMP_METHOD 1150 void LSRFixup::dump() const { 1151 print(errs()); errs() << '\n'; 1152 } 1153 1154 namespace { 1155 1156 /// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted 1157 /// SmallVectors of const SCEV*. 1158 struct UniquifierDenseMapInfo { 1159 static SmallVector<const SCEV *, 4> getEmptyKey() { 1160 SmallVector<const SCEV *, 4> V; 1161 V.push_back(reinterpret_cast<const SCEV *>(-1)); 1162 return V; 1163 } 1164 1165 static SmallVector<const SCEV *, 4> getTombstoneKey() { 1166 SmallVector<const SCEV *, 4> V; 1167 V.push_back(reinterpret_cast<const SCEV *>(-2)); 1168 return V; 1169 } 1170 1171 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) { 1172 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end())); 1173 } 1174 1175 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS, 1176 const SmallVector<const SCEV *, 4> &RHS) { 1177 return LHS == RHS; 1178 } 1179 }; 1180 1181 /// This class holds the state that LSR keeps for each use in IVUsers, as well 1182 /// as uses invented by LSR itself. It includes information about what kinds of 1183 /// things can be folded into the user, information about the user itself, and 1184 /// information about how the use may be satisfied. TODO: Represent multiple 1185 /// users of the same expression in common? 1186 class LSRUse { 1187 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier; 1188 1189 public: 1190 /// An enum for a kind of use, indicating what types of scaled and immediate 1191 /// operands it might support. 1192 enum KindType { 1193 Basic, ///< A normal use, with no folding. 1194 Special, ///< A special case of basic, allowing -1 scales. 1195 Address, ///< An address use; folding according to TargetLowering 1196 ICmpZero ///< An equality icmp with both operands folded into one. 1197 // TODO: Add a generic icmp too? 1198 }; 1199 1200 typedef PointerIntPair<const SCEV *, 2, KindType> SCEVUseKindPair; 1201 1202 KindType Kind; 1203 MemAccessTy AccessTy; 1204 1205 SmallVector<int64_t, 8> Offsets; 1206 int64_t MinOffset; 1207 int64_t MaxOffset; 1208 1209 /// This records whether all of the fixups using this LSRUse are outside of 1210 /// the loop, in which case some special-case heuristics may be used. 1211 bool AllFixupsOutsideLoop; 1212 1213 /// RigidFormula is set to true to guarantee that this use will be associated 1214 /// with a single formula--the one that initially matched. Some SCEV 1215 /// expressions cannot be expanded. This allows LSR to consider the registers 1216 /// used by those expressions without the need to expand them later after 1217 /// changing the formula. 1218 bool RigidFormula; 1219 1220 /// This records the widest use type for any fixup using this 1221 /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max 1222 /// fixup widths to be equivalent, because the narrower one may be relying on 1223 /// the implicit truncation to truncate away bogus bits. 1224 Type *WidestFixupType; 1225 1226 /// A list of ways to build a value that can satisfy this user. After the 1227 /// list is populated, one of these is selected heuristically and used to 1228 /// formulate a replacement for OperandValToReplace in UserInst. 1229 SmallVector<Formula, 12> Formulae; 1230 1231 /// The set of register candidates used by all formulae in this LSRUse. 1232 SmallPtrSet<const SCEV *, 4> Regs; 1233 1234 LSRUse(KindType K, MemAccessTy AT) 1235 : Kind(K), AccessTy(AT), MinOffset(INT64_MAX), MaxOffset(INT64_MIN), 1236 AllFixupsOutsideLoop(true), RigidFormula(false), 1237 WidestFixupType(nullptr) {} 1238 1239 bool HasFormulaWithSameRegs(const Formula &F) const; 1240 bool InsertFormula(const Formula &F); 1241 void DeleteFormula(Formula &F); 1242 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses); 1243 1244 void print(raw_ostream &OS) const; 1245 void dump() const; 1246 }; 1247 1248 } 1249 1250 /// Test whether this use as a formula which has the same registers as the given 1251 /// formula. 1252 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const { 1253 SmallVector<const SCEV *, 4> Key = F.BaseRegs; 1254 if (F.ScaledReg) Key.push_back(F.ScaledReg); 1255 // Unstable sort by host order ok, because this is only used for uniquifying. 1256 std::sort(Key.begin(), Key.end()); 1257 return Uniquifier.count(Key); 1258 } 1259 1260 /// If the given formula has not yet been inserted, add it to the list, and 1261 /// return true. Return false otherwise. The formula must be in canonical form. 1262 bool LSRUse::InsertFormula(const Formula &F) { 1263 assert(F.isCanonical() && "Invalid canonical representation"); 1264 1265 if (!Formulae.empty() && RigidFormula) 1266 return false; 1267 1268 SmallVector<const SCEV *, 4> Key = F.BaseRegs; 1269 if (F.ScaledReg) Key.push_back(F.ScaledReg); 1270 // Unstable sort by host order ok, because this is only used for uniquifying. 1271 std::sort(Key.begin(), Key.end()); 1272 1273 if (!Uniquifier.insert(Key).second) 1274 return false; 1275 1276 // Using a register to hold the value of 0 is not profitable. 1277 assert((!F.ScaledReg || !F.ScaledReg->isZero()) && 1278 "Zero allocated in a scaled register!"); 1279 #ifndef NDEBUG 1280 for (const SCEV *BaseReg : F.BaseRegs) 1281 assert(!BaseReg->isZero() && "Zero allocated in a base register!"); 1282 #endif 1283 1284 // Add the formula to the list. 1285 Formulae.push_back(F); 1286 1287 // Record registers now being used by this use. 1288 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); 1289 if (F.ScaledReg) 1290 Regs.insert(F.ScaledReg); 1291 1292 return true; 1293 } 1294 1295 /// Remove the given formula from this use's list. 1296 void LSRUse::DeleteFormula(Formula &F) { 1297 if (&F != &Formulae.back()) 1298 std::swap(F, Formulae.back()); 1299 Formulae.pop_back(); 1300 } 1301 1302 /// Recompute the Regs field, and update RegUses. 1303 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) { 1304 // Now that we've filtered out some formulae, recompute the Regs set. 1305 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs); 1306 Regs.clear(); 1307 for (const Formula &F : Formulae) { 1308 if (F.ScaledReg) Regs.insert(F.ScaledReg); 1309 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); 1310 } 1311 1312 // Update the RegTracker. 1313 for (const SCEV *S : OldRegs) 1314 if (!Regs.count(S)) 1315 RegUses.dropRegister(S, LUIdx); 1316 } 1317 1318 void LSRUse::print(raw_ostream &OS) const { 1319 OS << "LSR Use: Kind="; 1320 switch (Kind) { 1321 case Basic: OS << "Basic"; break; 1322 case Special: OS << "Special"; break; 1323 case ICmpZero: OS << "ICmpZero"; break; 1324 case Address: 1325 OS << "Address of "; 1326 if (AccessTy.MemTy->isPointerTy()) 1327 OS << "pointer"; // the full pointer type could be really verbose 1328 else { 1329 OS << *AccessTy.MemTy; 1330 } 1331 1332 OS << " in addrspace(" << AccessTy.AddrSpace << ')'; 1333 } 1334 1335 OS << ", Offsets={"; 1336 bool NeedComma = false; 1337 for (int64_t O : Offsets) { 1338 if (NeedComma) OS << ','; 1339 OS << O; 1340 NeedComma = true; 1341 } 1342 OS << '}'; 1343 1344 if (AllFixupsOutsideLoop) 1345 OS << ", all-fixups-outside-loop"; 1346 1347 if (WidestFixupType) 1348 OS << ", widest fixup type: " << *WidestFixupType; 1349 } 1350 1351 LLVM_DUMP_METHOD 1352 void LSRUse::dump() const { 1353 print(errs()); errs() << '\n'; 1354 } 1355 1356 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, 1357 LSRUse::KindType Kind, MemAccessTy AccessTy, 1358 GlobalValue *BaseGV, int64_t BaseOffset, 1359 bool HasBaseReg, int64_t Scale) { 1360 switch (Kind) { 1361 case LSRUse::Address: 1362 return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset, 1363 HasBaseReg, Scale, AccessTy.AddrSpace); 1364 1365 case LSRUse::ICmpZero: 1366 // There's not even a target hook for querying whether it would be legal to 1367 // fold a GV into an ICmp. 1368 if (BaseGV) 1369 return false; 1370 1371 // ICmp only has two operands; don't allow more than two non-trivial parts. 1372 if (Scale != 0 && HasBaseReg && BaseOffset != 0) 1373 return false; 1374 1375 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by 1376 // putting the scaled register in the other operand of the icmp. 1377 if (Scale != 0 && Scale != -1) 1378 return false; 1379 1380 // If we have low-level target information, ask the target if it can fold an 1381 // integer immediate on an icmp. 1382 if (BaseOffset != 0) { 1383 // We have one of: 1384 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset 1385 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset 1386 // Offs is the ICmp immediate. 1387 if (Scale == 0) 1388 // The cast does the right thing with INT64_MIN. 1389 BaseOffset = -(uint64_t)BaseOffset; 1390 return TTI.isLegalICmpImmediate(BaseOffset); 1391 } 1392 1393 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg 1394 return true; 1395 1396 case LSRUse::Basic: 1397 // Only handle single-register values. 1398 return !BaseGV && Scale == 0 && BaseOffset == 0; 1399 1400 case LSRUse::Special: 1401 // Special case Basic to handle -1 scales. 1402 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0; 1403 } 1404 1405 llvm_unreachable("Invalid LSRUse Kind!"); 1406 } 1407 1408 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, 1409 int64_t MinOffset, int64_t MaxOffset, 1410 LSRUse::KindType Kind, MemAccessTy AccessTy, 1411 GlobalValue *BaseGV, int64_t BaseOffset, 1412 bool HasBaseReg, int64_t Scale) { 1413 // Check for overflow. 1414 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) != 1415 (MinOffset > 0)) 1416 return false; 1417 MinOffset = (uint64_t)BaseOffset + MinOffset; 1418 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) != 1419 (MaxOffset > 0)) 1420 return false; 1421 MaxOffset = (uint64_t)BaseOffset + MaxOffset; 1422 1423 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset, 1424 HasBaseReg, Scale) && 1425 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset, 1426 HasBaseReg, Scale); 1427 } 1428 1429 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, 1430 int64_t MinOffset, int64_t MaxOffset, 1431 LSRUse::KindType Kind, MemAccessTy AccessTy, 1432 const Formula &F) { 1433 // For the purpose of isAMCompletelyFolded either having a canonical formula 1434 // or a scale not equal to zero is correct. 1435 // Problems may arise from non canonical formulae having a scale == 0. 1436 // Strictly speaking it would best to just rely on canonical formulae. 1437 // However, when we generate the scaled formulae, we first check that the 1438 // scaling factor is profitable before computing the actual ScaledReg for 1439 // compile time sake. 1440 assert((F.isCanonical() || F.Scale != 0)); 1441 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, 1442 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale); 1443 } 1444 1445 /// Test whether we know how to expand the current formula. 1446 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset, 1447 int64_t MaxOffset, LSRUse::KindType Kind, 1448 MemAccessTy AccessTy, GlobalValue *BaseGV, 1449 int64_t BaseOffset, bool HasBaseReg, int64_t Scale) { 1450 // We know how to expand completely foldable formulae. 1451 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV, 1452 BaseOffset, HasBaseReg, Scale) || 1453 // Or formulae that use a base register produced by a sum of base 1454 // registers. 1455 (Scale == 1 && 1456 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, 1457 BaseGV, BaseOffset, true, 0)); 1458 } 1459 1460 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset, 1461 int64_t MaxOffset, LSRUse::KindType Kind, 1462 MemAccessTy AccessTy, const Formula &F) { 1463 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV, 1464 F.BaseOffset, F.HasBaseReg, F.Scale); 1465 } 1466 1467 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, 1468 const LSRUse &LU, const Formula &F) { 1469 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, 1470 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg, 1471 F.Scale); 1472 } 1473 1474 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI, 1475 const LSRUse &LU, const Formula &F) { 1476 if (!F.Scale) 1477 return 0; 1478 1479 // If the use is not completely folded in that instruction, we will have to 1480 // pay an extra cost only for scale != 1. 1481 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, 1482 LU.AccessTy, F)) 1483 return F.Scale != 1; 1484 1485 switch (LU.Kind) { 1486 case LSRUse::Address: { 1487 // Check the scaling factor cost with both the min and max offsets. 1488 int ScaleCostMinOffset = TTI.getScalingFactorCost( 1489 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg, 1490 F.Scale, LU.AccessTy.AddrSpace); 1491 int ScaleCostMaxOffset = TTI.getScalingFactorCost( 1492 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg, 1493 F.Scale, LU.AccessTy.AddrSpace); 1494 1495 assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && 1496 "Legal addressing mode has an illegal cost!"); 1497 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset); 1498 } 1499 case LSRUse::ICmpZero: 1500 case LSRUse::Basic: 1501 case LSRUse::Special: 1502 // The use is completely folded, i.e., everything is folded into the 1503 // instruction. 1504 return 0; 1505 } 1506 1507 llvm_unreachable("Invalid LSRUse Kind!"); 1508 } 1509 1510 static bool isAlwaysFoldable(const TargetTransformInfo &TTI, 1511 LSRUse::KindType Kind, MemAccessTy AccessTy, 1512 GlobalValue *BaseGV, int64_t BaseOffset, 1513 bool HasBaseReg) { 1514 // Fast-path: zero is always foldable. 1515 if (BaseOffset == 0 && !BaseGV) return true; 1516 1517 // Conservatively, create an address with an immediate and a 1518 // base and a scale. 1519 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1; 1520 1521 // Canonicalize a scale of 1 to a base register if the formula doesn't 1522 // already have a base register. 1523 if (!HasBaseReg && Scale == 1) { 1524 Scale = 0; 1525 HasBaseReg = true; 1526 } 1527 1528 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset, 1529 HasBaseReg, Scale); 1530 } 1531 1532 static bool isAlwaysFoldable(const TargetTransformInfo &TTI, 1533 ScalarEvolution &SE, int64_t MinOffset, 1534 int64_t MaxOffset, LSRUse::KindType Kind, 1535 MemAccessTy AccessTy, const SCEV *S, 1536 bool HasBaseReg) { 1537 // Fast-path: zero is always foldable. 1538 if (S->isZero()) return true; 1539 1540 // Conservatively, create an address with an immediate and a 1541 // base and a scale. 1542 int64_t BaseOffset = ExtractImmediate(S, SE); 1543 GlobalValue *BaseGV = ExtractSymbol(S, SE); 1544 1545 // If there's anything else involved, it's not foldable. 1546 if (!S->isZero()) return false; 1547 1548 // Fast-path: zero is always foldable. 1549 if (BaseOffset == 0 && !BaseGV) return true; 1550 1551 // Conservatively, create an address with an immediate and a 1552 // base and a scale. 1553 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1; 1554 1555 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV, 1556 BaseOffset, HasBaseReg, Scale); 1557 } 1558 1559 namespace { 1560 1561 /// An individual increment in a Chain of IV increments. Relate an IV user to 1562 /// an expression that computes the IV it uses from the IV used by the previous 1563 /// link in the Chain. 1564 /// 1565 /// For the head of a chain, IncExpr holds the absolute SCEV expression for the 1566 /// original IVOperand. The head of the chain's IVOperand is only valid during 1567 /// chain collection, before LSR replaces IV users. During chain generation, 1568 /// IncExpr can be used to find the new IVOperand that computes the same 1569 /// expression. 1570 struct IVInc { 1571 Instruction *UserInst; 1572 Value* IVOperand; 1573 const SCEV *IncExpr; 1574 1575 IVInc(Instruction *U, Value *O, const SCEV *E): 1576 UserInst(U), IVOperand(O), IncExpr(E) {} 1577 }; 1578 1579 // The list of IV increments in program order. We typically add the head of a 1580 // chain without finding subsequent links. 1581 struct IVChain { 1582 SmallVector<IVInc,1> Incs; 1583 const SCEV *ExprBase; 1584 1585 IVChain() : ExprBase(nullptr) {} 1586 1587 IVChain(const IVInc &Head, const SCEV *Base) 1588 : Incs(1, Head), ExprBase(Base) {} 1589 1590 typedef SmallVectorImpl<IVInc>::const_iterator const_iterator; 1591 1592 // Return the first increment in the chain. 1593 const_iterator begin() const { 1594 assert(!Incs.empty()); 1595 return std::next(Incs.begin()); 1596 } 1597 const_iterator end() const { 1598 return Incs.end(); 1599 } 1600 1601 // Returns true if this chain contains any increments. 1602 bool hasIncs() const { return Incs.size() >= 2; } 1603 1604 // Add an IVInc to the end of this chain. 1605 void add(const IVInc &X) { Incs.push_back(X); } 1606 1607 // Returns the last UserInst in the chain. 1608 Instruction *tailUserInst() const { return Incs.back().UserInst; } 1609 1610 // Returns true if IncExpr can be profitably added to this chain. 1611 bool isProfitableIncrement(const SCEV *OperExpr, 1612 const SCEV *IncExpr, 1613 ScalarEvolution&); 1614 }; 1615 1616 /// Helper for CollectChains to track multiple IV increment uses. Distinguish 1617 /// between FarUsers that definitely cross IV increments and NearUsers that may 1618 /// be used between IV increments. 1619 struct ChainUsers { 1620 SmallPtrSet<Instruction*, 4> FarUsers; 1621 SmallPtrSet<Instruction*, 4> NearUsers; 1622 }; 1623 1624 /// This class holds state for the main loop strength reduction logic. 1625 class LSRInstance { 1626 IVUsers &IU; 1627 ScalarEvolution &SE; 1628 DominatorTree &DT; 1629 LoopInfo &LI; 1630 const TargetTransformInfo &TTI; 1631 Loop *const L; 1632 bool Changed; 1633 1634 /// This is the insert position that the current loop's induction variable 1635 /// increment should be placed. In simple loops, this is the latch block's 1636 /// terminator. But in more complicated cases, this is a position which will 1637 /// dominate all the in-loop post-increment users. 1638 Instruction *IVIncInsertPos; 1639 1640 /// Interesting factors between use strides. 1641 SmallSetVector<int64_t, 8> Factors; 1642 1643 /// Interesting use types, to facilitate truncation reuse. 1644 SmallSetVector<Type *, 4> Types; 1645 1646 /// The list of operands which are to be replaced. 1647 SmallVector<LSRFixup, 16> Fixups; 1648 1649 /// The list of interesting uses. 1650 SmallVector<LSRUse, 16> Uses; 1651 1652 /// Track which uses use which register candidates. 1653 RegUseTracker RegUses; 1654 1655 // Limit the number of chains to avoid quadratic behavior. We don't expect to 1656 // have more than a few IV increment chains in a loop. Missing a Chain falls 1657 // back to normal LSR behavior for those uses. 1658 static const unsigned MaxChains = 8; 1659 1660 /// IV users can form a chain of IV increments. 1661 SmallVector<IVChain, MaxChains> IVChainVec; 1662 1663 /// IV users that belong to profitable IVChains. 1664 SmallPtrSet<Use*, MaxChains> IVIncSet; 1665 1666 void OptimizeShadowIV(); 1667 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse); 1668 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse); 1669 void OptimizeLoopTermCond(); 1670 1671 void ChainInstruction(Instruction *UserInst, Instruction *IVOper, 1672 SmallVectorImpl<ChainUsers> &ChainUsersVec); 1673 void FinalizeChain(IVChain &Chain); 1674 void CollectChains(); 1675 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter, 1676 SmallVectorImpl<WeakVH> &DeadInsts); 1677 1678 void CollectInterestingTypesAndFactors(); 1679 void CollectFixupsAndInitialFormulae(); 1680 1681 LSRFixup &getNewFixup() { 1682 Fixups.push_back(LSRFixup()); 1683 return Fixups.back(); 1684 } 1685 1686 // Support for sharing of LSRUses between LSRFixups. 1687 typedef DenseMap<LSRUse::SCEVUseKindPair, size_t> UseMapTy; 1688 UseMapTy UseMap; 1689 1690 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg, 1691 LSRUse::KindType Kind, MemAccessTy AccessTy); 1692 1693 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind, 1694 MemAccessTy AccessTy); 1695 1696 void DeleteUse(LSRUse &LU, size_t LUIdx); 1697 1698 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU); 1699 1700 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); 1701 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); 1702 void CountRegisters(const Formula &F, size_t LUIdx); 1703 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F); 1704 1705 void CollectLoopInvariantFixupsAndFormulae(); 1706 1707 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base, 1708 unsigned Depth = 0); 1709 1710 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx, 1711 const Formula &Base, unsigned Depth, 1712 size_t Idx, bool IsScaledReg = false); 1713 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base); 1714 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx, 1715 const Formula &Base, size_t Idx, 1716 bool IsScaledReg = false); 1717 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); 1718 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx, 1719 const Formula &Base, 1720 const SmallVectorImpl<int64_t> &Worklist, 1721 size_t Idx, bool IsScaledReg = false); 1722 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); 1723 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base); 1724 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base); 1725 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base); 1726 void GenerateCrossUseConstantOffsets(); 1727 void GenerateAllReuseFormulae(); 1728 1729 void FilterOutUndesirableDedicatedRegisters(); 1730 1731 size_t EstimateSearchSpaceComplexity() const; 1732 void NarrowSearchSpaceByDetectingSupersets(); 1733 void NarrowSearchSpaceByCollapsingUnrolledCode(); 1734 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(); 1735 void NarrowSearchSpaceByPickingWinnerRegs(); 1736 void NarrowSearchSpaceUsingHeuristics(); 1737 1738 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution, 1739 Cost &SolutionCost, 1740 SmallVectorImpl<const Formula *> &Workspace, 1741 const Cost &CurCost, 1742 const SmallPtrSet<const SCEV *, 16> &CurRegs, 1743 DenseSet<const SCEV *> &VisitedRegs) const; 1744 void Solve(SmallVectorImpl<const Formula *> &Solution) const; 1745 1746 BasicBlock::iterator 1747 HoistInsertPosition(BasicBlock::iterator IP, 1748 const SmallVectorImpl<Instruction *> &Inputs) const; 1749 BasicBlock::iterator 1750 AdjustInsertPositionForExpand(BasicBlock::iterator IP, 1751 const LSRFixup &LF, 1752 const LSRUse &LU, 1753 SCEVExpander &Rewriter) const; 1754 1755 Value *Expand(const LSRFixup &LF, 1756 const Formula &F, 1757 BasicBlock::iterator IP, 1758 SCEVExpander &Rewriter, 1759 SmallVectorImpl<WeakVH> &DeadInsts) const; 1760 void RewriteForPHI(PHINode *PN, const LSRFixup &LF, 1761 const Formula &F, 1762 SCEVExpander &Rewriter, 1763 SmallVectorImpl<WeakVH> &DeadInsts) const; 1764 void Rewrite(const LSRFixup &LF, 1765 const Formula &F, 1766 SCEVExpander &Rewriter, 1767 SmallVectorImpl<WeakVH> &DeadInsts) const; 1768 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution); 1769 1770 public: 1771 LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT, 1772 LoopInfo &LI, const TargetTransformInfo &TTI); 1773 1774 bool getChanged() const { return Changed; } 1775 1776 void print_factors_and_types(raw_ostream &OS) const; 1777 void print_fixups(raw_ostream &OS) const; 1778 void print_uses(raw_ostream &OS) const; 1779 void print(raw_ostream &OS) const; 1780 void dump() const; 1781 }; 1782 1783 } 1784 1785 /// If IV is used in a int-to-float cast inside the loop then try to eliminate 1786 /// the cast operation. 1787 void LSRInstance::OptimizeShadowIV() { 1788 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); 1789 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) 1790 return; 1791 1792 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); 1793 UI != E; /* empty */) { 1794 IVUsers::const_iterator CandidateUI = UI; 1795 ++UI; 1796 Instruction *ShadowUse = CandidateUI->getUser(); 1797 Type *DestTy = nullptr; 1798 bool IsSigned = false; 1799 1800 /* If shadow use is a int->float cast then insert a second IV 1801 to eliminate this cast. 1802 1803 for (unsigned i = 0; i < n; ++i) 1804 foo((double)i); 1805 1806 is transformed into 1807 1808 double d = 0.0; 1809 for (unsigned i = 0; i < n; ++i, ++d) 1810 foo(d); 1811 */ 1812 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) { 1813 IsSigned = false; 1814 DestTy = UCast->getDestTy(); 1815 } 1816 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) { 1817 IsSigned = true; 1818 DestTy = SCast->getDestTy(); 1819 } 1820 if (!DestTy) continue; 1821 1822 // If target does not support DestTy natively then do not apply 1823 // this transformation. 1824 if (!TTI.isTypeLegal(DestTy)) continue; 1825 1826 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0)); 1827 if (!PH) continue; 1828 if (PH->getNumIncomingValues() != 2) continue; 1829 1830 Type *SrcTy = PH->getType(); 1831 int Mantissa = DestTy->getFPMantissaWidth(); 1832 if (Mantissa == -1) continue; 1833 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa) 1834 continue; 1835 1836 unsigned Entry, Latch; 1837 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) { 1838 Entry = 0; 1839 Latch = 1; 1840 } else { 1841 Entry = 1; 1842 Latch = 0; 1843 } 1844 1845 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry)); 1846 if (!Init) continue; 1847 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ? 1848 (double)Init->getSExtValue() : 1849 (double)Init->getZExtValue()); 1850 1851 BinaryOperator *Incr = 1852 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch)); 1853 if (!Incr) continue; 1854 if (Incr->getOpcode() != Instruction::Add 1855 && Incr->getOpcode() != Instruction::Sub) 1856 continue; 1857 1858 /* Initialize new IV, double d = 0.0 in above example. */ 1859 ConstantInt *C = nullptr; 1860 if (Incr->getOperand(0) == PH) 1861 C = dyn_cast<ConstantInt>(Incr->getOperand(1)); 1862 else if (Incr->getOperand(1) == PH) 1863 C = dyn_cast<ConstantInt>(Incr->getOperand(0)); 1864 else 1865 continue; 1866 1867 if (!C) continue; 1868 1869 // Ignore negative constants, as the code below doesn't handle them 1870 // correctly. TODO: Remove this restriction. 1871 if (!C->getValue().isStrictlyPositive()) continue; 1872 1873 /* Add new PHINode. */ 1874 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH); 1875 1876 /* create new increment. '++d' in above example. */ 1877 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue()); 1878 BinaryOperator *NewIncr = 1879 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ? 1880 Instruction::FAdd : Instruction::FSub, 1881 NewPH, CFP, "IV.S.next.", Incr); 1882 1883 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry)); 1884 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch)); 1885 1886 /* Remove cast operation */ 1887 ShadowUse->replaceAllUsesWith(NewPH); 1888 ShadowUse->eraseFromParent(); 1889 Changed = true; 1890 break; 1891 } 1892 } 1893 1894 /// If Cond has an operand that is an expression of an IV, set the IV user and 1895 /// stride information and return true, otherwise return false. 1896 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) { 1897 for (IVStrideUse &U : IU) 1898 if (U.getUser() == Cond) { 1899 // NOTE: we could handle setcc instructions with multiple uses here, but 1900 // InstCombine does it as well for simple uses, it's not clear that it 1901 // occurs enough in real life to handle. 1902 CondUse = &U; 1903 return true; 1904 } 1905 return false; 1906 } 1907 1908 /// Rewrite the loop's terminating condition if it uses a max computation. 1909 /// 1910 /// This is a narrow solution to a specific, but acute, problem. For loops 1911 /// like this: 1912 /// 1913 /// i = 0; 1914 /// do { 1915 /// p[i] = 0.0; 1916 /// } while (++i < n); 1917 /// 1918 /// the trip count isn't just 'n', because 'n' might not be positive. And 1919 /// unfortunately this can come up even for loops where the user didn't use 1920 /// a C do-while loop. For example, seemingly well-behaved top-test loops 1921 /// will commonly be lowered like this: 1922 // 1923 /// if (n > 0) { 1924 /// i = 0; 1925 /// do { 1926 /// p[i] = 0.0; 1927 /// } while (++i < n); 1928 /// } 1929 /// 1930 /// and then it's possible for subsequent optimization to obscure the if 1931 /// test in such a way that indvars can't find it. 1932 /// 1933 /// When indvars can't find the if test in loops like this, it creates a 1934 /// max expression, which allows it to give the loop a canonical 1935 /// induction variable: 1936 /// 1937 /// i = 0; 1938 /// max = n < 1 ? 1 : n; 1939 /// do { 1940 /// p[i] = 0.0; 1941 /// } while (++i != max); 1942 /// 1943 /// Canonical induction variables are necessary because the loop passes 1944 /// are designed around them. The most obvious example of this is the 1945 /// LoopInfo analysis, which doesn't remember trip count values. It 1946 /// expects to be able to rediscover the trip count each time it is 1947 /// needed, and it does this using a simple analysis that only succeeds if 1948 /// the loop has a canonical induction variable. 1949 /// 1950 /// However, when it comes time to generate code, the maximum operation 1951 /// can be quite costly, especially if it's inside of an outer loop. 1952 /// 1953 /// This function solves this problem by detecting this type of loop and 1954 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting 1955 /// the instructions for the maximum computation. 1956 /// 1957 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) { 1958 // Check that the loop matches the pattern we're looking for. 1959 if (Cond->getPredicate() != CmpInst::ICMP_EQ && 1960 Cond->getPredicate() != CmpInst::ICMP_NE) 1961 return Cond; 1962 1963 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1)); 1964 if (!Sel || !Sel->hasOneUse()) return Cond; 1965 1966 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); 1967 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) 1968 return Cond; 1969 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1); 1970 1971 // Add one to the backedge-taken count to get the trip count. 1972 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount); 1973 if (IterationCount != SE.getSCEV(Sel)) return Cond; 1974 1975 // Check for a max calculation that matches the pattern. There's no check 1976 // for ICMP_ULE here because the comparison would be with zero, which 1977 // isn't interesting. 1978 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE; 1979 const SCEVNAryExpr *Max = nullptr; 1980 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) { 1981 Pred = ICmpInst::ICMP_SLE; 1982 Max = S; 1983 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) { 1984 Pred = ICmpInst::ICMP_SLT; 1985 Max = S; 1986 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) { 1987 Pred = ICmpInst::ICMP_ULT; 1988 Max = U; 1989 } else { 1990 // No match; bail. 1991 return Cond; 1992 } 1993 1994 // To handle a max with more than two operands, this optimization would 1995 // require additional checking and setup. 1996 if (Max->getNumOperands() != 2) 1997 return Cond; 1998 1999 const SCEV *MaxLHS = Max->getOperand(0); 2000 const SCEV *MaxRHS = Max->getOperand(1); 2001 2002 // ScalarEvolution canonicalizes constants to the left. For < and >, look 2003 // for a comparison with 1. For <= and >=, a comparison with zero. 2004 if (!MaxLHS || 2005 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One))) 2006 return Cond; 2007 2008 // Check the relevant induction variable for conformance to 2009 // the pattern. 2010 const SCEV *IV = SE.getSCEV(Cond->getOperand(0)); 2011 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV); 2012 if (!AR || !AR->isAffine() || 2013 AR->getStart() != One || 2014 AR->getStepRecurrence(SE) != One) 2015 return Cond; 2016 2017 assert(AR->getLoop() == L && 2018 "Loop condition operand is an addrec in a different loop!"); 2019 2020 // Check the right operand of the select, and remember it, as it will 2021 // be used in the new comparison instruction. 2022 Value *NewRHS = nullptr; 2023 if (ICmpInst::isTrueWhenEqual(Pred)) { 2024 // Look for n+1, and grab n. 2025 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1))) 2026 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1))) 2027 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS) 2028 NewRHS = BO->getOperand(0); 2029 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2))) 2030 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1))) 2031 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS) 2032 NewRHS = BO->getOperand(0); 2033 if (!NewRHS) 2034 return Cond; 2035 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS) 2036 NewRHS = Sel->getOperand(1); 2037 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS) 2038 NewRHS = Sel->getOperand(2); 2039 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS)) 2040 NewRHS = SU->getValue(); 2041 else 2042 // Max doesn't match expected pattern. 2043 return Cond; 2044 2045 // Determine the new comparison opcode. It may be signed or unsigned, 2046 // and the original comparison may be either equality or inequality. 2047 if (Cond->getPredicate() == CmpInst::ICMP_EQ) 2048 Pred = CmpInst::getInversePredicate(Pred); 2049 2050 // Ok, everything looks ok to change the condition into an SLT or SGE and 2051 // delete the max calculation. 2052 ICmpInst *NewCond = 2053 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp"); 2054 2055 // Delete the max calculation instructions. 2056 Cond->replaceAllUsesWith(NewCond); 2057 CondUse->setUser(NewCond); 2058 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0)); 2059 Cond->eraseFromParent(); 2060 Sel->eraseFromParent(); 2061 if (Cmp->use_empty()) 2062 Cmp->eraseFromParent(); 2063 return NewCond; 2064 } 2065 2066 /// Change loop terminating condition to use the postinc iv when possible. 2067 void 2068 LSRInstance::OptimizeLoopTermCond() { 2069 SmallPtrSet<Instruction *, 4> PostIncs; 2070 2071 BasicBlock *LatchBlock = L->getLoopLatch(); 2072 SmallVector<BasicBlock*, 8> ExitingBlocks; 2073 L->getExitingBlocks(ExitingBlocks); 2074 2075 for (BasicBlock *ExitingBlock : ExitingBlocks) { 2076 2077 // Get the terminating condition for the loop if possible. If we 2078 // can, we want to change it to use a post-incremented version of its 2079 // induction variable, to allow coalescing the live ranges for the IV into 2080 // one register value. 2081 2082 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator()); 2083 if (!TermBr) 2084 continue; 2085 // FIXME: Overly conservative, termination condition could be an 'or' etc.. 2086 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition())) 2087 continue; 2088 2089 // Search IVUsesByStride to find Cond's IVUse if there is one. 2090 IVStrideUse *CondUse = nullptr; 2091 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition()); 2092 if (!FindIVUserForCond(Cond, CondUse)) 2093 continue; 2094 2095 // If the trip count is computed in terms of a max (due to ScalarEvolution 2096 // being unable to find a sufficient guard, for example), change the loop 2097 // comparison to use SLT or ULT instead of NE. 2098 // One consequence of doing this now is that it disrupts the count-down 2099 // optimization. That's not always a bad thing though, because in such 2100 // cases it may still be worthwhile to avoid a max. 2101 Cond = OptimizeMax(Cond, CondUse); 2102 2103 // If this exiting block dominates the latch block, it may also use 2104 // the post-inc value if it won't be shared with other uses. 2105 // Check for dominance. 2106 if (!DT.dominates(ExitingBlock, LatchBlock)) 2107 continue; 2108 2109 // Conservatively avoid trying to use the post-inc value in non-latch 2110 // exits if there may be pre-inc users in intervening blocks. 2111 if (LatchBlock != ExitingBlock) 2112 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) 2113 // Test if the use is reachable from the exiting block. This dominator 2114 // query is a conservative approximation of reachability. 2115 if (&*UI != CondUse && 2116 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) { 2117 // Conservatively assume there may be reuse if the quotient of their 2118 // strides could be a legal scale. 2119 const SCEV *A = IU.getStride(*CondUse, L); 2120 const SCEV *B = IU.getStride(*UI, L); 2121 if (!A || !B) continue; 2122 if (SE.getTypeSizeInBits(A->getType()) != 2123 SE.getTypeSizeInBits(B->getType())) { 2124 if (SE.getTypeSizeInBits(A->getType()) > 2125 SE.getTypeSizeInBits(B->getType())) 2126 B = SE.getSignExtendExpr(B, A->getType()); 2127 else 2128 A = SE.getSignExtendExpr(A, B->getType()); 2129 } 2130 if (const SCEVConstant *D = 2131 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) { 2132 const ConstantInt *C = D->getValue(); 2133 // Stride of one or negative one can have reuse with non-addresses. 2134 if (C->isOne() || C->isAllOnesValue()) 2135 goto decline_post_inc; 2136 // Avoid weird situations. 2137 if (C->getValue().getMinSignedBits() >= 64 || 2138 C->getValue().isMinSignedValue()) 2139 goto decline_post_inc; 2140 // Check for possible scaled-address reuse. 2141 MemAccessTy AccessTy = getAccessType(UI->getUser()); 2142 int64_t Scale = C->getSExtValue(); 2143 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr, 2144 /*BaseOffset=*/0, 2145 /*HasBaseReg=*/false, Scale, 2146 AccessTy.AddrSpace)) 2147 goto decline_post_inc; 2148 Scale = -Scale; 2149 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr, 2150 /*BaseOffset=*/0, 2151 /*HasBaseReg=*/false, Scale, 2152 AccessTy.AddrSpace)) 2153 goto decline_post_inc; 2154 } 2155 } 2156 2157 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: " 2158 << *Cond << '\n'); 2159 2160 // It's possible for the setcc instruction to be anywhere in the loop, and 2161 // possible for it to have multiple users. If it is not immediately before 2162 // the exiting block branch, move it. 2163 if (&*++BasicBlock::iterator(Cond) != TermBr) { 2164 if (Cond->hasOneUse()) { 2165 Cond->moveBefore(TermBr); 2166 } else { 2167 // Clone the terminating condition and insert into the loopend. 2168 ICmpInst *OldCond = Cond; 2169 Cond = cast<ICmpInst>(Cond->clone()); 2170 Cond->setName(L->getHeader()->getName() + ".termcond"); 2171 ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond); 2172 2173 // Clone the IVUse, as the old use still exists! 2174 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace()); 2175 TermBr->replaceUsesOfWith(OldCond, Cond); 2176 } 2177 } 2178 2179 // If we get to here, we know that we can transform the setcc instruction to 2180 // use the post-incremented version of the IV, allowing us to coalesce the 2181 // live ranges for the IV correctly. 2182 CondUse->transformToPostInc(L); 2183 Changed = true; 2184 2185 PostIncs.insert(Cond); 2186 decline_post_inc:; 2187 } 2188 2189 // Determine an insertion point for the loop induction variable increment. It 2190 // must dominate all the post-inc comparisons we just set up, and it must 2191 // dominate the loop latch edge. 2192 IVIncInsertPos = L->getLoopLatch()->getTerminator(); 2193 for (Instruction *Inst : PostIncs) { 2194 BasicBlock *BB = 2195 DT.findNearestCommonDominator(IVIncInsertPos->getParent(), 2196 Inst->getParent()); 2197 if (BB == Inst->getParent()) 2198 IVIncInsertPos = Inst; 2199 else if (BB != IVIncInsertPos->getParent()) 2200 IVIncInsertPos = BB->getTerminator(); 2201 } 2202 } 2203 2204 /// Determine if the given use can accommodate a fixup at the given offset and 2205 /// other details. If so, update the use and return true. 2206 bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, 2207 bool HasBaseReg, LSRUse::KindType Kind, 2208 MemAccessTy AccessTy) { 2209 int64_t NewMinOffset = LU.MinOffset; 2210 int64_t NewMaxOffset = LU.MaxOffset; 2211 MemAccessTy NewAccessTy = AccessTy; 2212 2213 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to 2214 // something conservative, however this can pessimize in the case that one of 2215 // the uses will have all its uses outside the loop, for example. 2216 if (LU.Kind != Kind) 2217 return false; 2218 2219 // Check for a mismatched access type, and fall back conservatively as needed. 2220 // TODO: Be less conservative when the type is similar and can use the same 2221 // addressing modes. 2222 if (Kind == LSRUse::Address) { 2223 if (AccessTy != LU.AccessTy) 2224 NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext()); 2225 } 2226 2227 // Conservatively assume HasBaseReg is true for now. 2228 if (NewOffset < LU.MinOffset) { 2229 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr, 2230 LU.MaxOffset - NewOffset, HasBaseReg)) 2231 return false; 2232 NewMinOffset = NewOffset; 2233 } else if (NewOffset > LU.MaxOffset) { 2234 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr, 2235 NewOffset - LU.MinOffset, HasBaseReg)) 2236 return false; 2237 NewMaxOffset = NewOffset; 2238 } 2239 2240 // Update the use. 2241 LU.MinOffset = NewMinOffset; 2242 LU.MaxOffset = NewMaxOffset; 2243 LU.AccessTy = NewAccessTy; 2244 if (NewOffset != LU.Offsets.back()) 2245 LU.Offsets.push_back(NewOffset); 2246 return true; 2247 } 2248 2249 /// Return an LSRUse index and an offset value for a fixup which needs the given 2250 /// expression, with the given kind and optional access type. Either reuse an 2251 /// existing use or create a new one, as needed. 2252 std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr, 2253 LSRUse::KindType Kind, 2254 MemAccessTy AccessTy) { 2255 const SCEV *Copy = Expr; 2256 int64_t Offset = ExtractImmediate(Expr, SE); 2257 2258 // Basic uses can't accept any offset, for example. 2259 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr, 2260 Offset, /*HasBaseReg=*/ true)) { 2261 Expr = Copy; 2262 Offset = 0; 2263 } 2264 2265 std::pair<UseMapTy::iterator, bool> P = 2266 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0)); 2267 if (!P.second) { 2268 // A use already existed with this base. 2269 size_t LUIdx = P.first->second; 2270 LSRUse &LU = Uses[LUIdx]; 2271 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy)) 2272 // Reuse this use. 2273 return std::make_pair(LUIdx, Offset); 2274 } 2275 2276 // Create a new use. 2277 size_t LUIdx = Uses.size(); 2278 P.first->second = LUIdx; 2279 Uses.push_back(LSRUse(Kind, AccessTy)); 2280 LSRUse &LU = Uses[LUIdx]; 2281 2282 // We don't need to track redundant offsets, but we don't need to go out 2283 // of our way here to avoid them. 2284 if (LU.Offsets.empty() || Offset != LU.Offsets.back()) 2285 LU.Offsets.push_back(Offset); 2286 2287 LU.MinOffset = Offset; 2288 LU.MaxOffset = Offset; 2289 return std::make_pair(LUIdx, Offset); 2290 } 2291 2292 /// Delete the given use from the Uses list. 2293 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) { 2294 if (&LU != &Uses.back()) 2295 std::swap(LU, Uses.back()); 2296 Uses.pop_back(); 2297 2298 // Update RegUses. 2299 RegUses.swapAndDropUse(LUIdx, Uses.size()); 2300 } 2301 2302 /// Look for a use distinct from OrigLU which is has a formula that has the same 2303 /// registers as the given formula. 2304 LSRUse * 2305 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF, 2306 const LSRUse &OrigLU) { 2307 // Search all uses for the formula. This could be more clever. 2308 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2309 LSRUse &LU = Uses[LUIdx]; 2310 // Check whether this use is close enough to OrigLU, to see whether it's 2311 // worthwhile looking through its formulae. 2312 // Ignore ICmpZero uses because they may contain formulae generated by 2313 // GenerateICmpZeroScales, in which case adding fixup offsets may 2314 // be invalid. 2315 if (&LU != &OrigLU && 2316 LU.Kind != LSRUse::ICmpZero && 2317 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy && 2318 LU.WidestFixupType == OrigLU.WidestFixupType && 2319 LU.HasFormulaWithSameRegs(OrigF)) { 2320 // Scan through this use's formulae. 2321 for (const Formula &F : LU.Formulae) { 2322 // Check to see if this formula has the same registers and symbols 2323 // as OrigF. 2324 if (F.BaseRegs == OrigF.BaseRegs && 2325 F.ScaledReg == OrigF.ScaledReg && 2326 F.BaseGV == OrigF.BaseGV && 2327 F.Scale == OrigF.Scale && 2328 F.UnfoldedOffset == OrigF.UnfoldedOffset) { 2329 if (F.BaseOffset == 0) 2330 return &LU; 2331 // This is the formula where all the registers and symbols matched; 2332 // there aren't going to be any others. Since we declined it, we 2333 // can skip the rest of the formulae and proceed to the next LSRUse. 2334 break; 2335 } 2336 } 2337 } 2338 } 2339 2340 // Nothing looked good. 2341 return nullptr; 2342 } 2343 2344 void LSRInstance::CollectInterestingTypesAndFactors() { 2345 SmallSetVector<const SCEV *, 4> Strides; 2346 2347 // Collect interesting types and strides. 2348 SmallVector<const SCEV *, 4> Worklist; 2349 for (const IVStrideUse &U : IU) { 2350 const SCEV *Expr = IU.getExpr(U); 2351 2352 // Collect interesting types. 2353 Types.insert(SE.getEffectiveSCEVType(Expr->getType())); 2354 2355 // Add strides for mentioned loops. 2356 Worklist.push_back(Expr); 2357 do { 2358 const SCEV *S = Worklist.pop_back_val(); 2359 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 2360 if (AR->getLoop() == L) 2361 Strides.insert(AR->getStepRecurrence(SE)); 2362 Worklist.push_back(AR->getStart()); 2363 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 2364 Worklist.append(Add->op_begin(), Add->op_end()); 2365 } 2366 } while (!Worklist.empty()); 2367 } 2368 2369 // Compute interesting factors from the set of interesting strides. 2370 for (SmallSetVector<const SCEV *, 4>::const_iterator 2371 I = Strides.begin(), E = Strides.end(); I != E; ++I) 2372 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter = 2373 std::next(I); NewStrideIter != E; ++NewStrideIter) { 2374 const SCEV *OldStride = *I; 2375 const SCEV *NewStride = *NewStrideIter; 2376 2377 if (SE.getTypeSizeInBits(OldStride->getType()) != 2378 SE.getTypeSizeInBits(NewStride->getType())) { 2379 if (SE.getTypeSizeInBits(OldStride->getType()) > 2380 SE.getTypeSizeInBits(NewStride->getType())) 2381 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType()); 2382 else 2383 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType()); 2384 } 2385 if (const SCEVConstant *Factor = 2386 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride, 2387 SE, true))) { 2388 if (Factor->getAPInt().getMinSignedBits() <= 64) 2389 Factors.insert(Factor->getAPInt().getSExtValue()); 2390 } else if (const SCEVConstant *Factor = 2391 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride, 2392 NewStride, 2393 SE, true))) { 2394 if (Factor->getAPInt().getMinSignedBits() <= 64) 2395 Factors.insert(Factor->getAPInt().getSExtValue()); 2396 } 2397 } 2398 2399 // If all uses use the same type, don't bother looking for truncation-based 2400 // reuse. 2401 if (Types.size() == 1) 2402 Types.clear(); 2403 2404 DEBUG(print_factors_and_types(dbgs())); 2405 } 2406 2407 /// Helper for CollectChains that finds an IV operand (computed by an AddRec in 2408 /// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to 2409 /// IVStrideUses, we could partially skip this. 2410 static User::op_iterator 2411 findIVOperand(User::op_iterator OI, User::op_iterator OE, 2412 Loop *L, ScalarEvolution &SE) { 2413 for(; OI != OE; ++OI) { 2414 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) { 2415 if (!SE.isSCEVable(Oper->getType())) 2416 continue; 2417 2418 if (const SCEVAddRecExpr *AR = 2419 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) { 2420 if (AR->getLoop() == L) 2421 break; 2422 } 2423 } 2424 } 2425 return OI; 2426 } 2427 2428 /// IVChain logic must consistenctly peek base TruncInst operands, so wrap it in 2429 /// a convenient helper. 2430 static Value *getWideOperand(Value *Oper) { 2431 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper)) 2432 return Trunc->getOperand(0); 2433 return Oper; 2434 } 2435 2436 /// Return true if we allow an IV chain to include both types. 2437 static bool isCompatibleIVType(Value *LVal, Value *RVal) { 2438 Type *LType = LVal->getType(); 2439 Type *RType = RVal->getType(); 2440 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy()); 2441 } 2442 2443 /// Return an approximation of this SCEV expression's "base", or NULL for any 2444 /// constant. Returning the expression itself is conservative. Returning a 2445 /// deeper subexpression is more precise and valid as long as it isn't less 2446 /// complex than another subexpression. For expressions involving multiple 2447 /// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids 2448 /// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i], 2449 /// IVInc==b-a. 2450 /// 2451 /// Since SCEVUnknown is the rightmost type, and pointers are the rightmost 2452 /// SCEVUnknown, we simply return the rightmost SCEV operand. 2453 static const SCEV *getExprBase(const SCEV *S) { 2454 switch (S->getSCEVType()) { 2455 default: // uncluding scUnknown. 2456 return S; 2457 case scConstant: 2458 return nullptr; 2459 case scTruncate: 2460 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand()); 2461 case scZeroExtend: 2462 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand()); 2463 case scSignExtend: 2464 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand()); 2465 case scAddExpr: { 2466 // Skip over scaled operands (scMulExpr) to follow add operands as long as 2467 // there's nothing more complex. 2468 // FIXME: not sure if we want to recognize negation. 2469 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S); 2470 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()), 2471 E(Add->op_begin()); I != E; ++I) { 2472 const SCEV *SubExpr = *I; 2473 if (SubExpr->getSCEVType() == scAddExpr) 2474 return getExprBase(SubExpr); 2475 2476 if (SubExpr->getSCEVType() != scMulExpr) 2477 return SubExpr; 2478 } 2479 return S; // all operands are scaled, be conservative. 2480 } 2481 case scAddRecExpr: 2482 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart()); 2483 } 2484 } 2485 2486 /// Return true if the chain increment is profitable to expand into a loop 2487 /// invariant value, which may require its own register. A profitable chain 2488 /// increment will be an offset relative to the same base. We allow such offsets 2489 /// to potentially be used as chain increment as long as it's not obviously 2490 /// expensive to expand using real instructions. 2491 bool IVChain::isProfitableIncrement(const SCEV *OperExpr, 2492 const SCEV *IncExpr, 2493 ScalarEvolution &SE) { 2494 // Aggressively form chains when -stress-ivchain. 2495 if (StressIVChain) 2496 return true; 2497 2498 // Do not replace a constant offset from IV head with a nonconstant IV 2499 // increment. 2500 if (!isa<SCEVConstant>(IncExpr)) { 2501 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand)); 2502 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr))) 2503 return 0; 2504 } 2505 2506 SmallPtrSet<const SCEV*, 8> Processed; 2507 return !isHighCostExpansion(IncExpr, Processed, SE); 2508 } 2509 2510 /// Return true if the number of registers needed for the chain is estimated to 2511 /// be less than the number required for the individual IV users. First prohibit 2512 /// any IV users that keep the IV live across increments (the Users set should 2513 /// be empty). Next count the number and type of increments in the chain. 2514 /// 2515 /// Chaining IVs can lead to considerable code bloat if ISEL doesn't 2516 /// effectively use postinc addressing modes. Only consider it profitable it the 2517 /// increments can be computed in fewer registers when chained. 2518 /// 2519 /// TODO: Consider IVInc free if it's already used in another chains. 2520 static bool 2521 isProfitableChain(IVChain &Chain, SmallPtrSetImpl<Instruction*> &Users, 2522 ScalarEvolution &SE, const TargetTransformInfo &TTI) { 2523 if (StressIVChain) 2524 return true; 2525 2526 if (!Chain.hasIncs()) 2527 return false; 2528 2529 if (!Users.empty()) { 2530 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n"; 2531 for (Instruction *Inst : Users) { 2532 dbgs() << " " << *Inst << "\n"; 2533 }); 2534 return false; 2535 } 2536 assert(!Chain.Incs.empty() && "empty IV chains are not allowed"); 2537 2538 // The chain itself may require a register, so intialize cost to 1. 2539 int cost = 1; 2540 2541 // A complete chain likely eliminates the need for keeping the original IV in 2542 // a register. LSR does not currently know how to form a complete chain unless 2543 // the header phi already exists. 2544 if (isa<PHINode>(Chain.tailUserInst()) 2545 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) { 2546 --cost; 2547 } 2548 const SCEV *LastIncExpr = nullptr; 2549 unsigned NumConstIncrements = 0; 2550 unsigned NumVarIncrements = 0; 2551 unsigned NumReusedIncrements = 0; 2552 for (const IVInc &Inc : Chain) { 2553 if (Inc.IncExpr->isZero()) 2554 continue; 2555 2556 // Incrementing by zero or some constant is neutral. We assume constants can 2557 // be folded into an addressing mode or an add's immediate operand. 2558 if (isa<SCEVConstant>(Inc.IncExpr)) { 2559 ++NumConstIncrements; 2560 continue; 2561 } 2562 2563 if (Inc.IncExpr == LastIncExpr) 2564 ++NumReusedIncrements; 2565 else 2566 ++NumVarIncrements; 2567 2568 LastIncExpr = Inc.IncExpr; 2569 } 2570 // An IV chain with a single increment is handled by LSR's postinc 2571 // uses. However, a chain with multiple increments requires keeping the IV's 2572 // value live longer than it needs to be if chained. 2573 if (NumConstIncrements > 1) 2574 --cost; 2575 2576 // Materializing increment expressions in the preheader that didn't exist in 2577 // the original code may cost a register. For example, sign-extended array 2578 // indices can produce ridiculous increments like this: 2579 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64))) 2580 cost += NumVarIncrements; 2581 2582 // Reusing variable increments likely saves a register to hold the multiple of 2583 // the stride. 2584 cost -= NumReusedIncrements; 2585 2586 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost 2587 << "\n"); 2588 2589 return cost < 0; 2590 } 2591 2592 /// Add this IV user to an existing chain or make it the head of a new chain. 2593 void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper, 2594 SmallVectorImpl<ChainUsers> &ChainUsersVec) { 2595 // When IVs are used as types of varying widths, they are generally converted 2596 // to a wider type with some uses remaining narrow under a (free) trunc. 2597 Value *const NextIV = getWideOperand(IVOper); 2598 const SCEV *const OperExpr = SE.getSCEV(NextIV); 2599 const SCEV *const OperExprBase = getExprBase(OperExpr); 2600 2601 // Visit all existing chains. Check if its IVOper can be computed as a 2602 // profitable loop invariant increment from the last link in the Chain. 2603 unsigned ChainIdx = 0, NChains = IVChainVec.size(); 2604 const SCEV *LastIncExpr = nullptr; 2605 for (; ChainIdx < NChains; ++ChainIdx) { 2606 IVChain &Chain = IVChainVec[ChainIdx]; 2607 2608 // Prune the solution space aggressively by checking that both IV operands 2609 // are expressions that operate on the same unscaled SCEVUnknown. This 2610 // "base" will be canceled by the subsequent getMinusSCEV call. Checking 2611 // first avoids creating extra SCEV expressions. 2612 if (!StressIVChain && Chain.ExprBase != OperExprBase) 2613 continue; 2614 2615 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand); 2616 if (!isCompatibleIVType(PrevIV, NextIV)) 2617 continue; 2618 2619 // A phi node terminates a chain. 2620 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst())) 2621 continue; 2622 2623 // The increment must be loop-invariant so it can be kept in a register. 2624 const SCEV *PrevExpr = SE.getSCEV(PrevIV); 2625 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr); 2626 if (!SE.isLoopInvariant(IncExpr, L)) 2627 continue; 2628 2629 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) { 2630 LastIncExpr = IncExpr; 2631 break; 2632 } 2633 } 2634 // If we haven't found a chain, create a new one, unless we hit the max. Don't 2635 // bother for phi nodes, because they must be last in the chain. 2636 if (ChainIdx == NChains) { 2637 if (isa<PHINode>(UserInst)) 2638 return; 2639 if (NChains >= MaxChains && !StressIVChain) { 2640 DEBUG(dbgs() << "IV Chain Limit\n"); 2641 return; 2642 } 2643 LastIncExpr = OperExpr; 2644 // IVUsers may have skipped over sign/zero extensions. We don't currently 2645 // attempt to form chains involving extensions unless they can be hoisted 2646 // into this loop's AddRec. 2647 if (!isa<SCEVAddRecExpr>(LastIncExpr)) 2648 return; 2649 ++NChains; 2650 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr), 2651 OperExprBase)); 2652 ChainUsersVec.resize(NChains); 2653 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst 2654 << ") IV=" << *LastIncExpr << "\n"); 2655 } else { 2656 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst 2657 << ") IV+" << *LastIncExpr << "\n"); 2658 // Add this IV user to the end of the chain. 2659 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr)); 2660 } 2661 IVChain &Chain = IVChainVec[ChainIdx]; 2662 2663 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers; 2664 // This chain's NearUsers become FarUsers. 2665 if (!LastIncExpr->isZero()) { 2666 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(), 2667 NearUsers.end()); 2668 NearUsers.clear(); 2669 } 2670 2671 // All other uses of IVOperand become near uses of the chain. 2672 // We currently ignore intermediate values within SCEV expressions, assuming 2673 // they will eventually be used be the current chain, or can be computed 2674 // from one of the chain increments. To be more precise we could 2675 // transitively follow its user and only add leaf IV users to the set. 2676 for (User *U : IVOper->users()) { 2677 Instruction *OtherUse = dyn_cast<Instruction>(U); 2678 if (!OtherUse) 2679 continue; 2680 // Uses in the chain will no longer be uses if the chain is formed. 2681 // Include the head of the chain in this iteration (not Chain.begin()). 2682 IVChain::const_iterator IncIter = Chain.Incs.begin(); 2683 IVChain::const_iterator IncEnd = Chain.Incs.end(); 2684 for( ; IncIter != IncEnd; ++IncIter) { 2685 if (IncIter->UserInst == OtherUse) 2686 break; 2687 } 2688 if (IncIter != IncEnd) 2689 continue; 2690 2691 if (SE.isSCEVable(OtherUse->getType()) 2692 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse)) 2693 && IU.isIVUserOrOperand(OtherUse)) { 2694 continue; 2695 } 2696 NearUsers.insert(OtherUse); 2697 } 2698 2699 // Since this user is part of the chain, it's no longer considered a use 2700 // of the chain. 2701 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst); 2702 } 2703 2704 /// Populate the vector of Chains. 2705 /// 2706 /// This decreases ILP at the architecture level. Targets with ample registers, 2707 /// multiple memory ports, and no register renaming probably don't want 2708 /// this. However, such targets should probably disable LSR altogether. 2709 /// 2710 /// The job of LSR is to make a reasonable choice of induction variables across 2711 /// the loop. Subsequent passes can easily "unchain" computation exposing more 2712 /// ILP *within the loop* if the target wants it. 2713 /// 2714 /// Finding the best IV chain is potentially a scheduling problem. Since LSR 2715 /// will not reorder memory operations, it will recognize this as a chain, but 2716 /// will generate redundant IV increments. Ideally this would be corrected later 2717 /// by a smart scheduler: 2718 /// = A[i] 2719 /// = A[i+x] 2720 /// A[i] = 2721 /// A[i+x] = 2722 /// 2723 /// TODO: Walk the entire domtree within this loop, not just the path to the 2724 /// loop latch. This will discover chains on side paths, but requires 2725 /// maintaining multiple copies of the Chains state. 2726 void LSRInstance::CollectChains() { 2727 DEBUG(dbgs() << "Collecting IV Chains.\n"); 2728 SmallVector<ChainUsers, 8> ChainUsersVec; 2729 2730 SmallVector<BasicBlock *,8> LatchPath; 2731 BasicBlock *LoopHeader = L->getHeader(); 2732 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch()); 2733 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) { 2734 LatchPath.push_back(Rung->getBlock()); 2735 } 2736 LatchPath.push_back(LoopHeader); 2737 2738 // Walk the instruction stream from the loop header to the loop latch. 2739 for (BasicBlock *BB : reverse(LatchPath)) { 2740 for (Instruction &I : *BB) { 2741 // Skip instructions that weren't seen by IVUsers analysis. 2742 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I)) 2743 continue; 2744 2745 // Ignore users that are part of a SCEV expression. This way we only 2746 // consider leaf IV Users. This effectively rediscovers a portion of 2747 // IVUsers analysis but in program order this time. 2748 if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I))) 2749 continue; 2750 2751 // Remove this instruction from any NearUsers set it may be in. 2752 for (unsigned ChainIdx = 0, NChains = IVChainVec.size(); 2753 ChainIdx < NChains; ++ChainIdx) { 2754 ChainUsersVec[ChainIdx].NearUsers.erase(&I); 2755 } 2756 // Search for operands that can be chained. 2757 SmallPtrSet<Instruction*, 4> UniqueOperands; 2758 User::op_iterator IVOpEnd = I.op_end(); 2759 User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE); 2760 while (IVOpIter != IVOpEnd) { 2761 Instruction *IVOpInst = cast<Instruction>(*IVOpIter); 2762 if (UniqueOperands.insert(IVOpInst).second) 2763 ChainInstruction(&I, IVOpInst, ChainUsersVec); 2764 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE); 2765 } 2766 } // Continue walking down the instructions. 2767 } // Continue walking down the domtree. 2768 // Visit phi backedges to determine if the chain can generate the IV postinc. 2769 for (BasicBlock::iterator I = L->getHeader()->begin(); 2770 PHINode *PN = dyn_cast<PHINode>(I); ++I) { 2771 if (!SE.isSCEVable(PN->getType())) 2772 continue; 2773 2774 Instruction *IncV = 2775 dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch())); 2776 if (IncV) 2777 ChainInstruction(PN, IncV, ChainUsersVec); 2778 } 2779 // Remove any unprofitable chains. 2780 unsigned ChainIdx = 0; 2781 for (unsigned UsersIdx = 0, NChains = IVChainVec.size(); 2782 UsersIdx < NChains; ++UsersIdx) { 2783 if (!isProfitableChain(IVChainVec[UsersIdx], 2784 ChainUsersVec[UsersIdx].FarUsers, SE, TTI)) 2785 continue; 2786 // Preserve the chain at UsesIdx. 2787 if (ChainIdx != UsersIdx) 2788 IVChainVec[ChainIdx] = IVChainVec[UsersIdx]; 2789 FinalizeChain(IVChainVec[ChainIdx]); 2790 ++ChainIdx; 2791 } 2792 IVChainVec.resize(ChainIdx); 2793 } 2794 2795 void LSRInstance::FinalizeChain(IVChain &Chain) { 2796 assert(!Chain.Incs.empty() && "empty IV chains are not allowed"); 2797 DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n"); 2798 2799 for (const IVInc &Inc : Chain) { 2800 DEBUG(dbgs() << " Inc: " << Inc.UserInst << "\n"); 2801 auto UseI = std::find(Inc.UserInst->op_begin(), Inc.UserInst->op_end(), 2802 Inc.IVOperand); 2803 assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand"); 2804 IVIncSet.insert(UseI); 2805 } 2806 } 2807 2808 /// Return true if the IVInc can be folded into an addressing mode. 2809 static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst, 2810 Value *Operand, const TargetTransformInfo &TTI) { 2811 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr); 2812 if (!IncConst || !isAddressUse(UserInst, Operand)) 2813 return false; 2814 2815 if (IncConst->getAPInt().getMinSignedBits() > 64) 2816 return false; 2817 2818 MemAccessTy AccessTy = getAccessType(UserInst); 2819 int64_t IncOffset = IncConst->getValue()->getSExtValue(); 2820 if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr, 2821 IncOffset, /*HaseBaseReg=*/false)) 2822 return false; 2823 2824 return true; 2825 } 2826 2827 /// Generate an add or subtract for each IVInc in a chain to materialize the IV 2828 /// user's operand from the previous IV user's operand. 2829 void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter, 2830 SmallVectorImpl<WeakVH> &DeadInsts) { 2831 // Find the new IVOperand for the head of the chain. It may have been replaced 2832 // by LSR. 2833 const IVInc &Head = Chain.Incs[0]; 2834 User::op_iterator IVOpEnd = Head.UserInst->op_end(); 2835 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user. 2836 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(), 2837 IVOpEnd, L, SE); 2838 Value *IVSrc = nullptr; 2839 while (IVOpIter != IVOpEnd) { 2840 IVSrc = getWideOperand(*IVOpIter); 2841 2842 // If this operand computes the expression that the chain needs, we may use 2843 // it. (Check this after setting IVSrc which is used below.) 2844 // 2845 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too 2846 // narrow for the chain, so we can no longer use it. We do allow using a 2847 // wider phi, assuming the LSR checked for free truncation. In that case we 2848 // should already have a truncate on this operand such that 2849 // getSCEV(IVSrc) == IncExpr. 2850 if (SE.getSCEV(*IVOpIter) == Head.IncExpr 2851 || SE.getSCEV(IVSrc) == Head.IncExpr) { 2852 break; 2853 } 2854 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE); 2855 } 2856 if (IVOpIter == IVOpEnd) { 2857 // Gracefully give up on this chain. 2858 DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n"); 2859 return; 2860 } 2861 2862 DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n"); 2863 Type *IVTy = IVSrc->getType(); 2864 Type *IntTy = SE.getEffectiveSCEVType(IVTy); 2865 const SCEV *LeftOverExpr = nullptr; 2866 for (const IVInc &Inc : Chain) { 2867 Instruction *InsertPt = Inc.UserInst; 2868 if (isa<PHINode>(InsertPt)) 2869 InsertPt = L->getLoopLatch()->getTerminator(); 2870 2871 // IVOper will replace the current IV User's operand. IVSrc is the IV 2872 // value currently held in a register. 2873 Value *IVOper = IVSrc; 2874 if (!Inc.IncExpr->isZero()) { 2875 // IncExpr was the result of subtraction of two narrow values, so must 2876 // be signed. 2877 const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy); 2878 LeftOverExpr = LeftOverExpr ? 2879 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr; 2880 } 2881 if (LeftOverExpr && !LeftOverExpr->isZero()) { 2882 // Expand the IV increment. 2883 Rewriter.clearPostInc(); 2884 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt); 2885 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc), 2886 SE.getUnknown(IncV)); 2887 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt); 2888 2889 // If an IV increment can't be folded, use it as the next IV value. 2890 if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) { 2891 assert(IVTy == IVOper->getType() && "inconsistent IV increment type"); 2892 IVSrc = IVOper; 2893 LeftOverExpr = nullptr; 2894 } 2895 } 2896 Type *OperTy = Inc.IVOperand->getType(); 2897 if (IVTy != OperTy) { 2898 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && 2899 "cannot extend a chained IV"); 2900 IRBuilder<> Builder(InsertPt); 2901 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain"); 2902 } 2903 Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper); 2904 DeadInsts.emplace_back(Inc.IVOperand); 2905 } 2906 // If LSR created a new, wider phi, we may also replace its postinc. We only 2907 // do this if we also found a wide value for the head of the chain. 2908 if (isa<PHINode>(Chain.tailUserInst())) { 2909 for (BasicBlock::iterator I = L->getHeader()->begin(); 2910 PHINode *Phi = dyn_cast<PHINode>(I); ++I) { 2911 if (!isCompatibleIVType(Phi, IVSrc)) 2912 continue; 2913 Instruction *PostIncV = dyn_cast<Instruction>( 2914 Phi->getIncomingValueForBlock(L->getLoopLatch())); 2915 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc))) 2916 continue; 2917 Value *IVOper = IVSrc; 2918 Type *PostIncTy = PostIncV->getType(); 2919 if (IVTy != PostIncTy) { 2920 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types"); 2921 IRBuilder<> Builder(L->getLoopLatch()->getTerminator()); 2922 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc()); 2923 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain"); 2924 } 2925 Phi->replaceUsesOfWith(PostIncV, IVOper); 2926 DeadInsts.emplace_back(PostIncV); 2927 } 2928 } 2929 } 2930 2931 void LSRInstance::CollectFixupsAndInitialFormulae() { 2932 for (const IVStrideUse &U : IU) { 2933 Instruction *UserInst = U.getUser(); 2934 // Skip IV users that are part of profitable IV Chains. 2935 User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(), 2936 U.getOperandValToReplace()); 2937 assert(UseI != UserInst->op_end() && "cannot find IV operand"); 2938 if (IVIncSet.count(UseI)) 2939 continue; 2940 2941 // Record the uses. 2942 LSRFixup &LF = getNewFixup(); 2943 LF.UserInst = UserInst; 2944 LF.OperandValToReplace = U.getOperandValToReplace(); 2945 LF.PostIncLoops = U.getPostIncLoops(); 2946 2947 LSRUse::KindType Kind = LSRUse::Basic; 2948 MemAccessTy AccessTy; 2949 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) { 2950 Kind = LSRUse::Address; 2951 AccessTy = getAccessType(LF.UserInst); 2952 } 2953 2954 const SCEV *S = IU.getExpr(U); 2955 2956 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as 2957 // (N - i == 0), and this allows (N - i) to be the expression that we work 2958 // with rather than just N or i, so we can consider the register 2959 // requirements for both N and i at the same time. Limiting this code to 2960 // equality icmps is not a problem because all interesting loops use 2961 // equality icmps, thanks to IndVarSimplify. 2962 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst)) 2963 if (CI->isEquality()) { 2964 // Swap the operands if needed to put the OperandValToReplace on the 2965 // left, for consistency. 2966 Value *NV = CI->getOperand(1); 2967 if (NV == LF.OperandValToReplace) { 2968 CI->setOperand(1, CI->getOperand(0)); 2969 CI->setOperand(0, NV); 2970 NV = CI->getOperand(1); 2971 Changed = true; 2972 } 2973 2974 // x == y --> x - y == 0 2975 const SCEV *N = SE.getSCEV(NV); 2976 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) { 2977 // S is normalized, so normalize N before folding it into S 2978 // to keep the result normalized. 2979 N = TransformForPostIncUse(Normalize, N, CI, nullptr, 2980 LF.PostIncLoops, SE, DT); 2981 Kind = LSRUse::ICmpZero; 2982 S = SE.getMinusSCEV(N, S); 2983 } 2984 2985 // -1 and the negations of all interesting strides (except the negation 2986 // of -1) are now also interesting. 2987 for (size_t i = 0, e = Factors.size(); i != e; ++i) 2988 if (Factors[i] != -1) 2989 Factors.insert(-(uint64_t)Factors[i]); 2990 Factors.insert(-1); 2991 } 2992 2993 // Set up the initial formula for this use. 2994 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy); 2995 LF.LUIdx = P.first; 2996 LF.Offset = P.second; 2997 LSRUse &LU = Uses[LF.LUIdx]; 2998 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L); 2999 if (!LU.WidestFixupType || 3000 SE.getTypeSizeInBits(LU.WidestFixupType) < 3001 SE.getTypeSizeInBits(LF.OperandValToReplace->getType())) 3002 LU.WidestFixupType = LF.OperandValToReplace->getType(); 3003 3004 // If this is the first use of this LSRUse, give it a formula. 3005 if (LU.Formulae.empty()) { 3006 InsertInitialFormula(S, LU, LF.LUIdx); 3007 CountRegisters(LU.Formulae.back(), LF.LUIdx); 3008 } 3009 } 3010 3011 DEBUG(print_fixups(dbgs())); 3012 } 3013 3014 /// Insert a formula for the given expression into the given use, separating out 3015 /// loop-variant portions from loop-invariant and loop-computable portions. 3016 void 3017 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) { 3018 // Mark uses whose expressions cannot be expanded. 3019 if (!isSafeToExpand(S, SE)) 3020 LU.RigidFormula = true; 3021 3022 Formula F; 3023 F.initialMatch(S, L, SE); 3024 bool Inserted = InsertFormula(LU, LUIdx, F); 3025 assert(Inserted && "Initial formula already exists!"); (void)Inserted; 3026 } 3027 3028 /// Insert a simple single-register formula for the given expression into the 3029 /// given use. 3030 void 3031 LSRInstance::InsertSupplementalFormula(const SCEV *S, 3032 LSRUse &LU, size_t LUIdx) { 3033 Formula F; 3034 F.BaseRegs.push_back(S); 3035 F.HasBaseReg = true; 3036 bool Inserted = InsertFormula(LU, LUIdx, F); 3037 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted; 3038 } 3039 3040 /// Note which registers are used by the given formula, updating RegUses. 3041 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) { 3042 if (F.ScaledReg) 3043 RegUses.countRegister(F.ScaledReg, LUIdx); 3044 for (const SCEV *BaseReg : F.BaseRegs) 3045 RegUses.countRegister(BaseReg, LUIdx); 3046 } 3047 3048 /// If the given formula has not yet been inserted, add it to the list, and 3049 /// return true. Return false otherwise. 3050 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) { 3051 // Do not insert formula that we will not be able to expand. 3052 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && 3053 "Formula is illegal"); 3054 if (!LU.InsertFormula(F)) 3055 return false; 3056 3057 CountRegisters(F, LUIdx); 3058 return true; 3059 } 3060 3061 /// Check for other uses of loop-invariant values which we're tracking. These 3062 /// other uses will pin these values in registers, making them less profitable 3063 /// for elimination. 3064 /// TODO: This currently misses non-constant addrec step registers. 3065 /// TODO: Should this give more weight to users inside the loop? 3066 void 3067 LSRInstance::CollectLoopInvariantFixupsAndFormulae() { 3068 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end()); 3069 SmallPtrSet<const SCEV *, 32> Visited; 3070 3071 while (!Worklist.empty()) { 3072 const SCEV *S = Worklist.pop_back_val(); 3073 3074 // Don't process the same SCEV twice 3075 if (!Visited.insert(S).second) 3076 continue; 3077 3078 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) 3079 Worklist.append(N->op_begin(), N->op_end()); 3080 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S)) 3081 Worklist.push_back(C->getOperand()); 3082 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) { 3083 Worklist.push_back(D->getLHS()); 3084 Worklist.push_back(D->getRHS()); 3085 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) { 3086 const Value *V = US->getValue(); 3087 if (const Instruction *Inst = dyn_cast<Instruction>(V)) { 3088 // Look for instructions defined outside the loop. 3089 if (L->contains(Inst)) continue; 3090 } else if (isa<UndefValue>(V)) 3091 // Undef doesn't have a live range, so it doesn't matter. 3092 continue; 3093 for (const Use &U : V->uses()) { 3094 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser()); 3095 // Ignore non-instructions. 3096 if (!UserInst) 3097 continue; 3098 // Ignore instructions in other functions (as can happen with 3099 // Constants). 3100 if (UserInst->getParent()->getParent() != L->getHeader()->getParent()) 3101 continue; 3102 // Ignore instructions not dominated by the loop. 3103 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ? 3104 UserInst->getParent() : 3105 cast<PHINode>(UserInst)->getIncomingBlock( 3106 PHINode::getIncomingValueNumForOperand(U.getOperandNo())); 3107 if (!DT.dominates(L->getHeader(), UseBB)) 3108 continue; 3109 // Don't bother if the instruction is in a BB which ends in an EHPad. 3110 if (UseBB->getTerminator()->isEHPad()) 3111 continue; 3112 // Ignore uses which are part of other SCEV expressions, to avoid 3113 // analyzing them multiple times. 3114 if (SE.isSCEVable(UserInst->getType())) { 3115 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst)); 3116 // If the user is a no-op, look through to its uses. 3117 if (!isa<SCEVUnknown>(UserS)) 3118 continue; 3119 if (UserS == US) { 3120 Worklist.push_back( 3121 SE.getUnknown(const_cast<Instruction *>(UserInst))); 3122 continue; 3123 } 3124 } 3125 // Ignore icmp instructions which are already being analyzed. 3126 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) { 3127 unsigned OtherIdx = !U.getOperandNo(); 3128 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx)); 3129 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L)) 3130 continue; 3131 } 3132 3133 LSRFixup &LF = getNewFixup(); 3134 LF.UserInst = const_cast<Instruction *>(UserInst); 3135 LF.OperandValToReplace = U; 3136 std::pair<size_t, int64_t> P = getUse( 3137 S, LSRUse::Basic, MemAccessTy()); 3138 LF.LUIdx = P.first; 3139 LF.Offset = P.second; 3140 LSRUse &LU = Uses[LF.LUIdx]; 3141 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L); 3142 if (!LU.WidestFixupType || 3143 SE.getTypeSizeInBits(LU.WidestFixupType) < 3144 SE.getTypeSizeInBits(LF.OperandValToReplace->getType())) 3145 LU.WidestFixupType = LF.OperandValToReplace->getType(); 3146 InsertSupplementalFormula(US, LU, LF.LUIdx); 3147 CountRegisters(LU.Formulae.back(), Uses.size() - 1); 3148 break; 3149 } 3150 } 3151 } 3152 } 3153 3154 /// Split S into subexpressions which can be pulled out into separate 3155 /// registers. If C is non-null, multiply each subexpression by C. 3156 /// 3157 /// Return remainder expression after factoring the subexpressions captured by 3158 /// Ops. If Ops is complete, return NULL. 3159 static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C, 3160 SmallVectorImpl<const SCEV *> &Ops, 3161 const Loop *L, 3162 ScalarEvolution &SE, 3163 unsigned Depth = 0) { 3164 // Arbitrarily cap recursion to protect compile time. 3165 if (Depth >= 3) 3166 return S; 3167 3168 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 3169 // Break out add operands. 3170 for (const SCEV *S : Add->operands()) { 3171 const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1); 3172 if (Remainder) 3173 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder); 3174 } 3175 return nullptr; 3176 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 3177 // Split a non-zero base out of an addrec. 3178 if (AR->getStart()->isZero()) 3179 return S; 3180 3181 const SCEV *Remainder = CollectSubexprs(AR->getStart(), 3182 C, Ops, L, SE, Depth+1); 3183 // Split the non-zero AddRec unless it is part of a nested recurrence that 3184 // does not pertain to this loop. 3185 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) { 3186 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder); 3187 Remainder = nullptr; 3188 } 3189 if (Remainder != AR->getStart()) { 3190 if (!Remainder) 3191 Remainder = SE.getConstant(AR->getType(), 0); 3192 return SE.getAddRecExpr(Remainder, 3193 AR->getStepRecurrence(SE), 3194 AR->getLoop(), 3195 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW) 3196 SCEV::FlagAnyWrap); 3197 } 3198 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) { 3199 // Break (C * (a + b + c)) into C*a + C*b + C*c. 3200 if (Mul->getNumOperands() != 2) 3201 return S; 3202 if (const SCEVConstant *Op0 = 3203 dyn_cast<SCEVConstant>(Mul->getOperand(0))) { 3204 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0; 3205 const SCEV *Remainder = 3206 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1); 3207 if (Remainder) 3208 Ops.push_back(SE.getMulExpr(C, Remainder)); 3209 return nullptr; 3210 } 3211 } 3212 return S; 3213 } 3214 3215 /// \brief Helper function for LSRInstance::GenerateReassociations. 3216 void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx, 3217 const Formula &Base, 3218 unsigned Depth, size_t Idx, 3219 bool IsScaledReg) { 3220 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx]; 3221 SmallVector<const SCEV *, 8> AddOps; 3222 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE); 3223 if (Remainder) 3224 AddOps.push_back(Remainder); 3225 3226 if (AddOps.size() == 1) 3227 return; 3228 3229 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(), 3230 JE = AddOps.end(); 3231 J != JE; ++J) { 3232 3233 // Loop-variant "unknown" values are uninteresting; we won't be able to 3234 // do anything meaningful with them. 3235 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L)) 3236 continue; 3237 3238 // Don't pull a constant into a register if the constant could be folded 3239 // into an immediate field. 3240 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind, 3241 LU.AccessTy, *J, Base.getNumRegs() > 1)) 3242 continue; 3243 3244 // Collect all operands except *J. 3245 SmallVector<const SCEV *, 8> InnerAddOps( 3246 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J); 3247 InnerAddOps.append(std::next(J), 3248 ((const SmallVector<const SCEV *, 8> &)AddOps).end()); 3249 3250 // Don't leave just a constant behind in a register if the constant could 3251 // be folded into an immediate field. 3252 if (InnerAddOps.size() == 1 && 3253 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind, 3254 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1)) 3255 continue; 3256 3257 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps); 3258 if (InnerSum->isZero()) 3259 continue; 3260 Formula F = Base; 3261 3262 // Add the remaining pieces of the add back into the new formula. 3263 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum); 3264 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 && 3265 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset + 3266 InnerSumSC->getValue()->getZExtValue())) { 3267 F.UnfoldedOffset = 3268 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue(); 3269 if (IsScaledReg) 3270 F.ScaledReg = nullptr; 3271 else 3272 F.BaseRegs.erase(F.BaseRegs.begin() + Idx); 3273 } else if (IsScaledReg) 3274 F.ScaledReg = InnerSum; 3275 else 3276 F.BaseRegs[Idx] = InnerSum; 3277 3278 // Add J as its own register, or an unfolded immediate. 3279 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J); 3280 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 && 3281 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset + 3282 SC->getValue()->getZExtValue())) 3283 F.UnfoldedOffset = 3284 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue(); 3285 else 3286 F.BaseRegs.push_back(*J); 3287 // We may have changed the number of register in base regs, adjust the 3288 // formula accordingly. 3289 F.canonicalize(); 3290 3291 if (InsertFormula(LU, LUIdx, F)) 3292 // If that formula hadn't been seen before, recurse to find more like 3293 // it. 3294 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth + 1); 3295 } 3296 } 3297 3298 /// Split out subexpressions from adds and the bases of addrecs. 3299 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx, 3300 Formula Base, unsigned Depth) { 3301 assert(Base.isCanonical() && "Input must be in the canonical form"); 3302 // Arbitrarily cap recursion to protect compile time. 3303 if (Depth >= 3) 3304 return; 3305 3306 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) 3307 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i); 3308 3309 if (Base.Scale == 1) 3310 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, 3311 /* Idx */ -1, /* IsScaledReg */ true); 3312 } 3313 3314 /// Generate a formula consisting of all of the loop-dominating registers added 3315 /// into a single register. 3316 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx, 3317 Formula Base) { 3318 // This method is only interesting on a plurality of registers. 3319 if (Base.BaseRegs.size() + (Base.Scale == 1) <= 1) 3320 return; 3321 3322 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before 3323 // processing the formula. 3324 Base.unscale(); 3325 Formula F = Base; 3326 F.BaseRegs.clear(); 3327 SmallVector<const SCEV *, 4> Ops; 3328 for (const SCEV *BaseReg : Base.BaseRegs) { 3329 if (SE.properlyDominates(BaseReg, L->getHeader()) && 3330 !SE.hasComputableLoopEvolution(BaseReg, L)) 3331 Ops.push_back(BaseReg); 3332 else 3333 F.BaseRegs.push_back(BaseReg); 3334 } 3335 if (Ops.size() > 1) { 3336 const SCEV *Sum = SE.getAddExpr(Ops); 3337 // TODO: If Sum is zero, it probably means ScalarEvolution missed an 3338 // opportunity to fold something. For now, just ignore such cases 3339 // rather than proceed with zero in a register. 3340 if (!Sum->isZero()) { 3341 F.BaseRegs.push_back(Sum); 3342 F.canonicalize(); 3343 (void)InsertFormula(LU, LUIdx, F); 3344 } 3345 } 3346 } 3347 3348 /// \brief Helper function for LSRInstance::GenerateSymbolicOffsets. 3349 void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx, 3350 const Formula &Base, size_t Idx, 3351 bool IsScaledReg) { 3352 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx]; 3353 GlobalValue *GV = ExtractSymbol(G, SE); 3354 if (G->isZero() || !GV) 3355 return; 3356 Formula F = Base; 3357 F.BaseGV = GV; 3358 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F)) 3359 return; 3360 if (IsScaledReg) 3361 F.ScaledReg = G; 3362 else 3363 F.BaseRegs[Idx] = G; 3364 (void)InsertFormula(LU, LUIdx, F); 3365 } 3366 3367 /// Generate reuse formulae using symbolic offsets. 3368 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, 3369 Formula Base) { 3370 // We can't add a symbolic offset if the address already contains one. 3371 if (Base.BaseGV) return; 3372 3373 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) 3374 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i); 3375 if (Base.Scale == 1) 3376 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1, 3377 /* IsScaledReg */ true); 3378 } 3379 3380 /// \brief Helper function for LSRInstance::GenerateConstantOffsets. 3381 void LSRInstance::GenerateConstantOffsetsImpl( 3382 LSRUse &LU, unsigned LUIdx, const Formula &Base, 3383 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) { 3384 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx]; 3385 for (int64_t Offset : Worklist) { 3386 Formula F = Base; 3387 F.BaseOffset = (uint64_t)Base.BaseOffset - Offset; 3388 if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind, 3389 LU.AccessTy, F)) { 3390 // Add the offset to the base register. 3391 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G); 3392 // If it cancelled out, drop the base register, otherwise update it. 3393 if (NewG->isZero()) { 3394 if (IsScaledReg) { 3395 F.Scale = 0; 3396 F.ScaledReg = nullptr; 3397 } else 3398 F.deleteBaseReg(F.BaseRegs[Idx]); 3399 F.canonicalize(); 3400 } else if (IsScaledReg) 3401 F.ScaledReg = NewG; 3402 else 3403 F.BaseRegs[Idx] = NewG; 3404 3405 (void)InsertFormula(LU, LUIdx, F); 3406 } 3407 } 3408 3409 int64_t Imm = ExtractImmediate(G, SE); 3410 if (G->isZero() || Imm == 0) 3411 return; 3412 Formula F = Base; 3413 F.BaseOffset = (uint64_t)F.BaseOffset + Imm; 3414 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F)) 3415 return; 3416 if (IsScaledReg) 3417 F.ScaledReg = G; 3418 else 3419 F.BaseRegs[Idx] = G; 3420 (void)InsertFormula(LU, LUIdx, F); 3421 } 3422 3423 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets. 3424 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, 3425 Formula Base) { 3426 // TODO: For now, just add the min and max offset, because it usually isn't 3427 // worthwhile looking at everything inbetween. 3428 SmallVector<int64_t, 2> Worklist; 3429 Worklist.push_back(LU.MinOffset); 3430 if (LU.MaxOffset != LU.MinOffset) 3431 Worklist.push_back(LU.MaxOffset); 3432 3433 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) 3434 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i); 3435 if (Base.Scale == 1) 3436 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1, 3437 /* IsScaledReg */ true); 3438 } 3439 3440 /// For ICmpZero, check to see if we can scale up the comparison. For example, x 3441 /// == y -> x*c == y*c. 3442 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, 3443 Formula Base) { 3444 if (LU.Kind != LSRUse::ICmpZero) return; 3445 3446 // Determine the integer type for the base formula. 3447 Type *IntTy = Base.getType(); 3448 if (!IntTy) return; 3449 if (SE.getTypeSizeInBits(IntTy) > 64) return; 3450 3451 // Don't do this if there is more than one offset. 3452 if (LU.MinOffset != LU.MaxOffset) return; 3453 3454 assert(!Base.BaseGV && "ICmpZero use is not legal!"); 3455 3456 // Check each interesting stride. 3457 for (int64_t Factor : Factors) { 3458 // Check that the multiplication doesn't overflow. 3459 if (Base.BaseOffset == INT64_MIN && Factor == -1) 3460 continue; 3461 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor; 3462 if (NewBaseOffset / Factor != Base.BaseOffset) 3463 continue; 3464 // If the offset will be truncated at this use, check that it is in bounds. 3465 if (!IntTy->isPointerTy() && 3466 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset)) 3467 continue; 3468 3469 // Check that multiplying with the use offset doesn't overflow. 3470 int64_t Offset = LU.MinOffset; 3471 if (Offset == INT64_MIN && Factor == -1) 3472 continue; 3473 Offset = (uint64_t)Offset * Factor; 3474 if (Offset / Factor != LU.MinOffset) 3475 continue; 3476 // If the offset will be truncated at this use, check that it is in bounds. 3477 if (!IntTy->isPointerTy() && 3478 !ConstantInt::isValueValidForType(IntTy, Offset)) 3479 continue; 3480 3481 Formula F = Base; 3482 F.BaseOffset = NewBaseOffset; 3483 3484 // Check that this scale is legal. 3485 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F)) 3486 continue; 3487 3488 // Compensate for the use having MinOffset built into it. 3489 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset; 3490 3491 const SCEV *FactorS = SE.getConstant(IntTy, Factor); 3492 3493 // Check that multiplying with each base register doesn't overflow. 3494 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) { 3495 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS); 3496 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i]) 3497 goto next; 3498 } 3499 3500 // Check that multiplying with the scaled register doesn't overflow. 3501 if (F.ScaledReg) { 3502 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS); 3503 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg) 3504 continue; 3505 } 3506 3507 // Check that multiplying with the unfolded offset doesn't overflow. 3508 if (F.UnfoldedOffset != 0) { 3509 if (F.UnfoldedOffset == INT64_MIN && Factor == -1) 3510 continue; 3511 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor; 3512 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset) 3513 continue; 3514 // If the offset will be truncated, check that it is in bounds. 3515 if (!IntTy->isPointerTy() && 3516 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset)) 3517 continue; 3518 } 3519 3520 // If we make it here and it's legal, add it. 3521 (void)InsertFormula(LU, LUIdx, F); 3522 next:; 3523 } 3524 } 3525 3526 /// Generate stride factor reuse formulae by making use of scaled-offset address 3527 /// modes, for example. 3528 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) { 3529 // Determine the integer type for the base formula. 3530 Type *IntTy = Base.getType(); 3531 if (!IntTy) return; 3532 3533 // If this Formula already has a scaled register, we can't add another one. 3534 // Try to unscale the formula to generate a better scale. 3535 if (Base.Scale != 0 && !Base.unscale()) 3536 return; 3537 3538 assert(Base.Scale == 0 && "unscale did not did its job!"); 3539 3540 // Check each interesting stride. 3541 for (int64_t Factor : Factors) { 3542 Base.Scale = Factor; 3543 Base.HasBaseReg = Base.BaseRegs.size() > 1; 3544 // Check whether this scale is going to be legal. 3545 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, 3546 Base)) { 3547 // As a special-case, handle special out-of-loop Basic users specially. 3548 // TODO: Reconsider this special case. 3549 if (LU.Kind == LSRUse::Basic && 3550 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special, 3551 LU.AccessTy, Base) && 3552 LU.AllFixupsOutsideLoop) 3553 LU.Kind = LSRUse::Special; 3554 else 3555 continue; 3556 } 3557 // For an ICmpZero, negating a solitary base register won't lead to 3558 // new solutions. 3559 if (LU.Kind == LSRUse::ICmpZero && 3560 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV) 3561 continue; 3562 // For each addrec base reg, apply the scale, if possible. 3563 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) 3564 if (const SCEVAddRecExpr *AR = 3565 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) { 3566 const SCEV *FactorS = SE.getConstant(IntTy, Factor); 3567 if (FactorS->isZero()) 3568 continue; 3569 // Divide out the factor, ignoring high bits, since we'll be 3570 // scaling the value back up in the end. 3571 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) { 3572 // TODO: This could be optimized to avoid all the copying. 3573 Formula F = Base; 3574 F.ScaledReg = Quotient; 3575 F.deleteBaseReg(F.BaseRegs[i]); 3576 // The canonical representation of 1*reg is reg, which is already in 3577 // Base. In that case, do not try to insert the formula, it will be 3578 // rejected anyway. 3579 if (F.Scale == 1 && F.BaseRegs.empty()) 3580 continue; 3581 (void)InsertFormula(LU, LUIdx, F); 3582 } 3583 } 3584 } 3585 } 3586 3587 /// Generate reuse formulae from different IV types. 3588 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) { 3589 // Don't bother truncating symbolic values. 3590 if (Base.BaseGV) return; 3591 3592 // Determine the integer type for the base formula. 3593 Type *DstTy = Base.getType(); 3594 if (!DstTy) return; 3595 DstTy = SE.getEffectiveSCEVType(DstTy); 3596 3597 for (Type *SrcTy : Types) { 3598 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) { 3599 Formula F = Base; 3600 3601 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy); 3602 for (const SCEV *&BaseReg : F.BaseRegs) 3603 BaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy); 3604 3605 // TODO: This assumes we've done basic processing on all uses and 3606 // have an idea what the register usage is. 3607 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses)) 3608 continue; 3609 3610 (void)InsertFormula(LU, LUIdx, F); 3611 } 3612 } 3613 } 3614 3615 namespace { 3616 3617 /// Helper class for GenerateCrossUseConstantOffsets. It's used to defer 3618 /// modifications so that the search phase doesn't have to worry about the data 3619 /// structures moving underneath it. 3620 struct WorkItem { 3621 size_t LUIdx; 3622 int64_t Imm; 3623 const SCEV *OrigReg; 3624 3625 WorkItem(size_t LI, int64_t I, const SCEV *R) 3626 : LUIdx(LI), Imm(I), OrigReg(R) {} 3627 3628 void print(raw_ostream &OS) const; 3629 void dump() const; 3630 }; 3631 3632 } 3633 3634 void WorkItem::print(raw_ostream &OS) const { 3635 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx 3636 << " , add offset " << Imm; 3637 } 3638 3639 LLVM_DUMP_METHOD 3640 void WorkItem::dump() const { 3641 print(errs()); errs() << '\n'; 3642 } 3643 3644 /// Look for registers which are a constant distance apart and try to form reuse 3645 /// opportunities between them. 3646 void LSRInstance::GenerateCrossUseConstantOffsets() { 3647 // Group the registers by their value without any added constant offset. 3648 typedef std::map<int64_t, const SCEV *> ImmMapTy; 3649 DenseMap<const SCEV *, ImmMapTy> Map; 3650 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap; 3651 SmallVector<const SCEV *, 8> Sequence; 3652 for (const SCEV *Use : RegUses) { 3653 const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify. 3654 int64_t Imm = ExtractImmediate(Reg, SE); 3655 auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy())); 3656 if (Pair.second) 3657 Sequence.push_back(Reg); 3658 Pair.first->second.insert(std::make_pair(Imm, Use)); 3659 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use); 3660 } 3661 3662 // Now examine each set of registers with the same base value. Build up 3663 // a list of work to do and do the work in a separate step so that we're 3664 // not adding formulae and register counts while we're searching. 3665 SmallVector<WorkItem, 32> WorkItems; 3666 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems; 3667 for (const SCEV *Reg : Sequence) { 3668 const ImmMapTy &Imms = Map.find(Reg)->second; 3669 3670 // It's not worthwhile looking for reuse if there's only one offset. 3671 if (Imms.size() == 1) 3672 continue; 3673 3674 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':'; 3675 for (const auto &Entry : Imms) 3676 dbgs() << ' ' << Entry.first; 3677 dbgs() << '\n'); 3678 3679 // Examine each offset. 3680 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end(); 3681 J != JE; ++J) { 3682 const SCEV *OrigReg = J->second; 3683 3684 int64_t JImm = J->first; 3685 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg); 3686 3687 if (!isa<SCEVConstant>(OrigReg) && 3688 UsedByIndicesMap[Reg].count() == 1) { 3689 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n'); 3690 continue; 3691 } 3692 3693 // Conservatively examine offsets between this orig reg a few selected 3694 // other orig regs. 3695 ImmMapTy::const_iterator OtherImms[] = { 3696 Imms.begin(), std::prev(Imms.end()), 3697 Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) / 3698 2) 3699 }; 3700 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) { 3701 ImmMapTy::const_iterator M = OtherImms[i]; 3702 if (M == J || M == JE) continue; 3703 3704 // Compute the difference between the two. 3705 int64_t Imm = (uint64_t)JImm - M->first; 3706 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1; 3707 LUIdx = UsedByIndices.find_next(LUIdx)) 3708 // Make a memo of this use, offset, and register tuple. 3709 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second) 3710 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg)); 3711 } 3712 } 3713 } 3714 3715 Map.clear(); 3716 Sequence.clear(); 3717 UsedByIndicesMap.clear(); 3718 UniqueItems.clear(); 3719 3720 // Now iterate through the worklist and add new formulae. 3721 for (const WorkItem &WI : WorkItems) { 3722 size_t LUIdx = WI.LUIdx; 3723 LSRUse &LU = Uses[LUIdx]; 3724 int64_t Imm = WI.Imm; 3725 const SCEV *OrigReg = WI.OrigReg; 3726 3727 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType()); 3728 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm)); 3729 unsigned BitWidth = SE.getTypeSizeInBits(IntTy); 3730 3731 // TODO: Use a more targeted data structure. 3732 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) { 3733 Formula F = LU.Formulae[L]; 3734 // FIXME: The code for the scaled and unscaled registers looks 3735 // very similar but slightly different. Investigate if they 3736 // could be merged. That way, we would not have to unscale the 3737 // Formula. 3738 F.unscale(); 3739 // Use the immediate in the scaled register. 3740 if (F.ScaledReg == OrigReg) { 3741 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale; 3742 // Don't create 50 + reg(-50). 3743 if (F.referencesReg(SE.getSCEV( 3744 ConstantInt::get(IntTy, -(uint64_t)Offset)))) 3745 continue; 3746 Formula NewF = F; 3747 NewF.BaseOffset = Offset; 3748 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, 3749 NewF)) 3750 continue; 3751 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg); 3752 3753 // If the new scale is a constant in a register, and adding the constant 3754 // value to the immediate would produce a value closer to zero than the 3755 // immediate itself, then the formula isn't worthwhile. 3756 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg)) 3757 if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) && 3758 (C->getAPInt().abs() * APInt(BitWidth, F.Scale)) 3759 .ule(std::abs(NewF.BaseOffset))) 3760 continue; 3761 3762 // OK, looks good. 3763 NewF.canonicalize(); 3764 (void)InsertFormula(LU, LUIdx, NewF); 3765 } else { 3766 // Use the immediate in a base register. 3767 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) { 3768 const SCEV *BaseReg = F.BaseRegs[N]; 3769 if (BaseReg != OrigReg) 3770 continue; 3771 Formula NewF = F; 3772 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm; 3773 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, 3774 LU.Kind, LU.AccessTy, NewF)) { 3775 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm)) 3776 continue; 3777 NewF = F; 3778 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm; 3779 } 3780 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg); 3781 3782 // If the new formula has a constant in a register, and adding the 3783 // constant value to the immediate would produce a value closer to 3784 // zero than the immediate itself, then the formula isn't worthwhile. 3785 for (const SCEV *NewReg : NewF.BaseRegs) 3786 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg)) 3787 if ((C->getAPInt() + NewF.BaseOffset) 3788 .abs() 3789 .slt(std::abs(NewF.BaseOffset)) && 3790 (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >= 3791 countTrailingZeros<uint64_t>(NewF.BaseOffset)) 3792 goto skip_formula; 3793 3794 // Ok, looks good. 3795 NewF.canonicalize(); 3796 (void)InsertFormula(LU, LUIdx, NewF); 3797 break; 3798 skip_formula:; 3799 } 3800 } 3801 } 3802 } 3803 } 3804 3805 /// Generate formulae for each use. 3806 void 3807 LSRInstance::GenerateAllReuseFormulae() { 3808 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan 3809 // queries are more precise. 3810 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3811 LSRUse &LU = Uses[LUIdx]; 3812 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3813 GenerateReassociations(LU, LUIdx, LU.Formulae[i]); 3814 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3815 GenerateCombinations(LU, LUIdx, LU.Formulae[i]); 3816 } 3817 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3818 LSRUse &LU = Uses[LUIdx]; 3819 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3820 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]); 3821 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3822 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]); 3823 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3824 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]); 3825 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3826 GenerateScales(LU, LUIdx, LU.Formulae[i]); 3827 } 3828 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3829 LSRUse &LU = Uses[LUIdx]; 3830 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3831 GenerateTruncates(LU, LUIdx, LU.Formulae[i]); 3832 } 3833 3834 GenerateCrossUseConstantOffsets(); 3835 3836 DEBUG(dbgs() << "\n" 3837 "After generating reuse formulae:\n"; 3838 print_uses(dbgs())); 3839 } 3840 3841 /// If there are multiple formulae with the same set of registers used 3842 /// by other uses, pick the best one and delete the others. 3843 void LSRInstance::FilterOutUndesirableDedicatedRegisters() { 3844 DenseSet<const SCEV *> VisitedRegs; 3845 SmallPtrSet<const SCEV *, 16> Regs; 3846 SmallPtrSet<const SCEV *, 16> LoserRegs; 3847 #ifndef NDEBUG 3848 bool ChangedFormulae = false; 3849 #endif 3850 3851 // Collect the best formula for each unique set of shared registers. This 3852 // is reset for each use. 3853 typedef DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo> 3854 BestFormulaeTy; 3855 BestFormulaeTy BestFormulae; 3856 3857 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3858 LSRUse &LU = Uses[LUIdx]; 3859 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n'); 3860 3861 bool Any = false; 3862 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); 3863 FIdx != NumForms; ++FIdx) { 3864 Formula &F = LU.Formulae[FIdx]; 3865 3866 // Some formulas are instant losers. For example, they may depend on 3867 // nonexistent AddRecs from other loops. These need to be filtered 3868 // immediately, otherwise heuristics could choose them over others leading 3869 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here 3870 // avoids the need to recompute this information across formulae using the 3871 // same bad AddRec. Passing LoserRegs is also essential unless we remove 3872 // the corresponding bad register from the Regs set. 3873 Cost CostF; 3874 Regs.clear(); 3875 CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, LU.Offsets, SE, DT, LU, 3876 &LoserRegs); 3877 if (CostF.isLoser()) { 3878 // During initial formula generation, undesirable formulae are generated 3879 // by uses within other loops that have some non-trivial address mode or 3880 // use the postinc form of the IV. LSR needs to provide these formulae 3881 // as the basis of rediscovering the desired formula that uses an AddRec 3882 // corresponding to the existing phi. Once all formulae have been 3883 // generated, these initial losers may be pruned. 3884 DEBUG(dbgs() << " Filtering loser "; F.print(dbgs()); 3885 dbgs() << "\n"); 3886 } 3887 else { 3888 SmallVector<const SCEV *, 4> Key; 3889 for (const SCEV *Reg : F.BaseRegs) { 3890 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx)) 3891 Key.push_back(Reg); 3892 } 3893 if (F.ScaledReg && 3894 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx)) 3895 Key.push_back(F.ScaledReg); 3896 // Unstable sort by host order ok, because this is only used for 3897 // uniquifying. 3898 std::sort(Key.begin(), Key.end()); 3899 3900 std::pair<BestFormulaeTy::const_iterator, bool> P = 3901 BestFormulae.insert(std::make_pair(Key, FIdx)); 3902 if (P.second) 3903 continue; 3904 3905 Formula &Best = LU.Formulae[P.first->second]; 3906 3907 Cost CostBest; 3908 Regs.clear(); 3909 CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, LU.Offsets, SE, 3910 DT, LU); 3911 if (CostF < CostBest) 3912 std::swap(F, Best); 3913 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs()); 3914 dbgs() << "\n" 3915 " in favor of formula "; Best.print(dbgs()); 3916 dbgs() << '\n'); 3917 } 3918 #ifndef NDEBUG 3919 ChangedFormulae = true; 3920 #endif 3921 LU.DeleteFormula(F); 3922 --FIdx; 3923 --NumForms; 3924 Any = true; 3925 } 3926 3927 // Now that we've filtered out some formulae, recompute the Regs set. 3928 if (Any) 3929 LU.RecomputeRegs(LUIdx, RegUses); 3930 3931 // Reset this to prepare for the next use. 3932 BestFormulae.clear(); 3933 } 3934 3935 DEBUG(if (ChangedFormulae) { 3936 dbgs() << "\n" 3937 "After filtering out undesirable candidates:\n"; 3938 print_uses(dbgs()); 3939 }); 3940 } 3941 3942 // This is a rough guess that seems to work fairly well. 3943 static const size_t ComplexityLimit = UINT16_MAX; 3944 3945 /// Estimate the worst-case number of solutions the solver might have to 3946 /// consider. It almost never considers this many solutions because it prune the 3947 /// search space, but the pruning isn't always sufficient. 3948 size_t LSRInstance::EstimateSearchSpaceComplexity() const { 3949 size_t Power = 1; 3950 for (const LSRUse &LU : Uses) { 3951 size_t FSize = LU.Formulae.size(); 3952 if (FSize >= ComplexityLimit) { 3953 Power = ComplexityLimit; 3954 break; 3955 } 3956 Power *= FSize; 3957 if (Power >= ComplexityLimit) 3958 break; 3959 } 3960 return Power; 3961 } 3962 3963 /// When one formula uses a superset of the registers of another formula, it 3964 /// won't help reduce register pressure (though it may not necessarily hurt 3965 /// register pressure); remove it to simplify the system. 3966 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() { 3967 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 3968 DEBUG(dbgs() << "The search space is too complex.\n"); 3969 3970 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae " 3971 "which use a superset of registers used by other " 3972 "formulae.\n"); 3973 3974 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3975 LSRUse &LU = Uses[LUIdx]; 3976 bool Any = false; 3977 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { 3978 Formula &F = LU.Formulae[i]; 3979 // Look for a formula with a constant or GV in a register. If the use 3980 // also has a formula with that same value in an immediate field, 3981 // delete the one that uses a register. 3982 for (SmallVectorImpl<const SCEV *>::const_iterator 3983 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) { 3984 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) { 3985 Formula NewF = F; 3986 NewF.BaseOffset += C->getValue()->getSExtValue(); 3987 NewF.BaseRegs.erase(NewF.BaseRegs.begin() + 3988 (I - F.BaseRegs.begin())); 3989 if (LU.HasFormulaWithSameRegs(NewF)) { 3990 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); 3991 LU.DeleteFormula(F); 3992 --i; 3993 --e; 3994 Any = true; 3995 break; 3996 } 3997 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) { 3998 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) 3999 if (!F.BaseGV) { 4000 Formula NewF = F; 4001 NewF.BaseGV = GV; 4002 NewF.BaseRegs.erase(NewF.BaseRegs.begin() + 4003 (I - F.BaseRegs.begin())); 4004 if (LU.HasFormulaWithSameRegs(NewF)) { 4005 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); 4006 dbgs() << '\n'); 4007 LU.DeleteFormula(F); 4008 --i; 4009 --e; 4010 Any = true; 4011 break; 4012 } 4013 } 4014 } 4015 } 4016 } 4017 if (Any) 4018 LU.RecomputeRegs(LUIdx, RegUses); 4019 } 4020 4021 DEBUG(dbgs() << "After pre-selection:\n"; 4022 print_uses(dbgs())); 4023 } 4024 } 4025 4026 /// When there are many registers for expressions like A, A+1, A+2, etc., 4027 /// allocate a single register for them. 4028 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() { 4029 if (EstimateSearchSpaceComplexity() < ComplexityLimit) 4030 return; 4031 4032 DEBUG(dbgs() << "The search space is too complex.\n" 4033 "Narrowing the search space by assuming that uses separated " 4034 "by a constant offset will use the same registers.\n"); 4035 4036 // This is especially useful for unrolled loops. 4037 4038 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 4039 LSRUse &LU = Uses[LUIdx]; 4040 for (const Formula &F : LU.Formulae) { 4041 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1)) 4042 continue; 4043 4044 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU); 4045 if (!LUThatHas) 4046 continue; 4047 4048 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false, 4049 LU.Kind, LU.AccessTy)) 4050 continue; 4051 4052 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n'); 4053 4054 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop; 4055 4056 // Update the relocs to reference the new use. 4057 for (LSRFixup &Fixup : Fixups) { 4058 if (Fixup.LUIdx == LUIdx) { 4059 Fixup.LUIdx = LUThatHas - &Uses.front(); 4060 Fixup.Offset += F.BaseOffset; 4061 // Add the new offset to LUThatHas' offset list. 4062 if (LUThatHas->Offsets.back() != Fixup.Offset) { 4063 LUThatHas->Offsets.push_back(Fixup.Offset); 4064 if (Fixup.Offset > LUThatHas->MaxOffset) 4065 LUThatHas->MaxOffset = Fixup.Offset; 4066 if (Fixup.Offset < LUThatHas->MinOffset) 4067 LUThatHas->MinOffset = Fixup.Offset; 4068 } 4069 DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n'); 4070 } 4071 if (Fixup.LUIdx == NumUses-1) 4072 Fixup.LUIdx = LUIdx; 4073 } 4074 4075 // Delete formulae from the new use which are no longer legal. 4076 bool Any = false; 4077 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) { 4078 Formula &F = LUThatHas->Formulae[i]; 4079 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset, 4080 LUThatHas->Kind, LUThatHas->AccessTy, F)) { 4081 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); 4082 dbgs() << '\n'); 4083 LUThatHas->DeleteFormula(F); 4084 --i; 4085 --e; 4086 Any = true; 4087 } 4088 } 4089 4090 if (Any) 4091 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses); 4092 4093 // Delete the old use. 4094 DeleteUse(LU, LUIdx); 4095 --LUIdx; 4096 --NumUses; 4097 break; 4098 } 4099 } 4100 4101 DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs())); 4102 } 4103 4104 /// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that 4105 /// we've done more filtering, as it may be able to find more formulae to 4106 /// eliminate. 4107 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){ 4108 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 4109 DEBUG(dbgs() << "The search space is too complex.\n"); 4110 4111 DEBUG(dbgs() << "Narrowing the search space by re-filtering out " 4112 "undesirable dedicated registers.\n"); 4113 4114 FilterOutUndesirableDedicatedRegisters(); 4115 4116 DEBUG(dbgs() << "After pre-selection:\n"; 4117 print_uses(dbgs())); 4118 } 4119 } 4120 4121 /// Pick a register which seems likely to be profitable, and then in any use 4122 /// which has any reference to that register, delete all formulae which do not 4123 /// reference that register. 4124 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() { 4125 // With all other options exhausted, loop until the system is simple 4126 // enough to handle. 4127 SmallPtrSet<const SCEV *, 4> Taken; 4128 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 4129 // Ok, we have too many of formulae on our hands to conveniently handle. 4130 // Use a rough heuristic to thin out the list. 4131 DEBUG(dbgs() << "The search space is too complex.\n"); 4132 4133 // Pick the register which is used by the most LSRUses, which is likely 4134 // to be a good reuse register candidate. 4135 const SCEV *Best = nullptr; 4136 unsigned BestNum = 0; 4137 for (const SCEV *Reg : RegUses) { 4138 if (Taken.count(Reg)) 4139 continue; 4140 if (!Best) 4141 Best = Reg; 4142 else { 4143 unsigned Count = RegUses.getUsedByIndices(Reg).count(); 4144 if (Count > BestNum) { 4145 Best = Reg; 4146 BestNum = Count; 4147 } 4148 } 4149 } 4150 4151 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best 4152 << " will yield profitable reuse.\n"); 4153 Taken.insert(Best); 4154 4155 // In any use with formulae which references this register, delete formulae 4156 // which don't reference it. 4157 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 4158 LSRUse &LU = Uses[LUIdx]; 4159 if (!LU.Regs.count(Best)) continue; 4160 4161 bool Any = false; 4162 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { 4163 Formula &F = LU.Formulae[i]; 4164 if (!F.referencesReg(Best)) { 4165 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); 4166 LU.DeleteFormula(F); 4167 --e; 4168 --i; 4169 Any = true; 4170 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?"); 4171 continue; 4172 } 4173 } 4174 4175 if (Any) 4176 LU.RecomputeRegs(LUIdx, RegUses); 4177 } 4178 4179 DEBUG(dbgs() << "After pre-selection:\n"; 4180 print_uses(dbgs())); 4181 } 4182 } 4183 4184 /// If there are an extraordinary number of formulae to choose from, use some 4185 /// rough heuristics to prune down the number of formulae. This keeps the main 4186 /// solver from taking an extraordinary amount of time in some worst-case 4187 /// scenarios. 4188 void LSRInstance::NarrowSearchSpaceUsingHeuristics() { 4189 NarrowSearchSpaceByDetectingSupersets(); 4190 NarrowSearchSpaceByCollapsingUnrolledCode(); 4191 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(); 4192 NarrowSearchSpaceByPickingWinnerRegs(); 4193 } 4194 4195 /// This is the recursive solver. 4196 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution, 4197 Cost &SolutionCost, 4198 SmallVectorImpl<const Formula *> &Workspace, 4199 const Cost &CurCost, 4200 const SmallPtrSet<const SCEV *, 16> &CurRegs, 4201 DenseSet<const SCEV *> &VisitedRegs) const { 4202 // Some ideas: 4203 // - prune more: 4204 // - use more aggressive filtering 4205 // - sort the formula so that the most profitable solutions are found first 4206 // - sort the uses too 4207 // - search faster: 4208 // - don't compute a cost, and then compare. compare while computing a cost 4209 // and bail early. 4210 // - track register sets with SmallBitVector 4211 4212 const LSRUse &LU = Uses[Workspace.size()]; 4213 4214 // If this use references any register that's already a part of the 4215 // in-progress solution, consider it a requirement that a formula must 4216 // reference that register in order to be considered. This prunes out 4217 // unprofitable searching. 4218 SmallSetVector<const SCEV *, 4> ReqRegs; 4219 for (const SCEV *S : CurRegs) 4220 if (LU.Regs.count(S)) 4221 ReqRegs.insert(S); 4222 4223 SmallPtrSet<const SCEV *, 16> NewRegs; 4224 Cost NewCost; 4225 for (const Formula &F : LU.Formulae) { 4226 // Ignore formulae which may not be ideal in terms of register reuse of 4227 // ReqRegs. The formula should use all required registers before 4228 // introducing new ones. 4229 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size()); 4230 for (const SCEV *Reg : ReqRegs) { 4231 if ((F.ScaledReg && F.ScaledReg == Reg) || 4232 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) != 4233 F.BaseRegs.end()) { 4234 --NumReqRegsToFind; 4235 if (NumReqRegsToFind == 0) 4236 break; 4237 } 4238 } 4239 if (NumReqRegsToFind != 0) { 4240 // If none of the formulae satisfied the required registers, then we could 4241 // clear ReqRegs and try again. Currently, we simply give up in this case. 4242 continue; 4243 } 4244 4245 // Evaluate the cost of the current formula. If it's already worse than 4246 // the current best, prune the search at that point. 4247 NewCost = CurCost; 4248 NewRegs = CurRegs; 4249 NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT, 4250 LU); 4251 if (NewCost < SolutionCost) { 4252 Workspace.push_back(&F); 4253 if (Workspace.size() != Uses.size()) { 4254 SolveRecurse(Solution, SolutionCost, Workspace, NewCost, 4255 NewRegs, VisitedRegs); 4256 if (F.getNumRegs() == 1 && Workspace.size() == 1) 4257 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]); 4258 } else { 4259 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs()); 4260 dbgs() << ".\n Regs:"; 4261 for (const SCEV *S : NewRegs) 4262 dbgs() << ' ' << *S; 4263 dbgs() << '\n'); 4264 4265 SolutionCost = NewCost; 4266 Solution = Workspace; 4267 } 4268 Workspace.pop_back(); 4269 } 4270 } 4271 } 4272 4273 /// Choose one formula from each use. Return the results in the given Solution 4274 /// vector. 4275 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const { 4276 SmallVector<const Formula *, 8> Workspace; 4277 Cost SolutionCost; 4278 SolutionCost.Lose(); 4279 Cost CurCost; 4280 SmallPtrSet<const SCEV *, 16> CurRegs; 4281 DenseSet<const SCEV *> VisitedRegs; 4282 Workspace.reserve(Uses.size()); 4283 4284 // SolveRecurse does all the work. 4285 SolveRecurse(Solution, SolutionCost, Workspace, CurCost, 4286 CurRegs, VisitedRegs); 4287 if (Solution.empty()) { 4288 DEBUG(dbgs() << "\nNo Satisfactory Solution\n"); 4289 return; 4290 } 4291 4292 // Ok, we've now made all our decisions. 4293 DEBUG(dbgs() << "\n" 4294 "The chosen solution requires "; SolutionCost.print(dbgs()); 4295 dbgs() << ":\n"; 4296 for (size_t i = 0, e = Uses.size(); i != e; ++i) { 4297 dbgs() << " "; 4298 Uses[i].print(dbgs()); 4299 dbgs() << "\n" 4300 " "; 4301 Solution[i]->print(dbgs()); 4302 dbgs() << '\n'; 4303 }); 4304 4305 assert(Solution.size() == Uses.size() && "Malformed solution!"); 4306 } 4307 4308 /// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as 4309 /// we can go while still being dominated by the input positions. This helps 4310 /// canonicalize the insert position, which encourages sharing. 4311 BasicBlock::iterator 4312 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP, 4313 const SmallVectorImpl<Instruction *> &Inputs) 4314 const { 4315 Instruction *Tentative = &*IP; 4316 for (;;) { 4317 bool AllDominate = true; 4318 Instruction *BetterPos = nullptr; 4319 // Don't bother attempting to insert before a catchswitch, their basic block 4320 // cannot have other non-PHI instructions. 4321 if (isa<CatchSwitchInst>(Tentative)) 4322 return IP; 4323 4324 for (Instruction *Inst : Inputs) { 4325 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) { 4326 AllDominate = false; 4327 break; 4328 } 4329 // Attempt to find an insert position in the middle of the block, 4330 // instead of at the end, so that it can be used for other expansions. 4331 if (Tentative->getParent() == Inst->getParent() && 4332 (!BetterPos || !DT.dominates(Inst, BetterPos))) 4333 BetterPos = &*std::next(BasicBlock::iterator(Inst)); 4334 } 4335 if (!AllDominate) 4336 break; 4337 if (BetterPos) 4338 IP = BetterPos->getIterator(); 4339 else 4340 IP = Tentative->getIterator(); 4341 4342 const Loop *IPLoop = LI.getLoopFor(IP->getParent()); 4343 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0; 4344 4345 BasicBlock *IDom; 4346 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) { 4347 if (!Rung) return IP; 4348 Rung = Rung->getIDom(); 4349 if (!Rung) return IP; 4350 IDom = Rung->getBlock(); 4351 4352 // Don't climb into a loop though. 4353 const Loop *IDomLoop = LI.getLoopFor(IDom); 4354 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0; 4355 if (IDomDepth <= IPLoopDepth && 4356 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop)) 4357 break; 4358 } 4359 4360 Tentative = IDom->getTerminator(); 4361 } 4362 4363 return IP; 4364 } 4365 4366 /// Determine an input position which will be dominated by the operands and 4367 /// which will dominate the result. 4368 BasicBlock::iterator 4369 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP, 4370 const LSRFixup &LF, 4371 const LSRUse &LU, 4372 SCEVExpander &Rewriter) const { 4373 // Collect some instructions which must be dominated by the 4374 // expanding replacement. These must be dominated by any operands that 4375 // will be required in the expansion. 4376 SmallVector<Instruction *, 4> Inputs; 4377 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace)) 4378 Inputs.push_back(I); 4379 if (LU.Kind == LSRUse::ICmpZero) 4380 if (Instruction *I = 4381 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1))) 4382 Inputs.push_back(I); 4383 if (LF.PostIncLoops.count(L)) { 4384 if (LF.isUseFullyOutsideLoop(L)) 4385 Inputs.push_back(L->getLoopLatch()->getTerminator()); 4386 else 4387 Inputs.push_back(IVIncInsertPos); 4388 } 4389 // The expansion must also be dominated by the increment positions of any 4390 // loops it for which it is using post-inc mode. 4391 for (const Loop *PIL : LF.PostIncLoops) { 4392 if (PIL == L) continue; 4393 4394 // Be dominated by the loop exit. 4395 SmallVector<BasicBlock *, 4> ExitingBlocks; 4396 PIL->getExitingBlocks(ExitingBlocks); 4397 if (!ExitingBlocks.empty()) { 4398 BasicBlock *BB = ExitingBlocks[0]; 4399 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i) 4400 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]); 4401 Inputs.push_back(BB->getTerminator()); 4402 } 4403 } 4404 4405 assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() 4406 && !isa<DbgInfoIntrinsic>(LowestIP) && 4407 "Insertion point must be a normal instruction"); 4408 4409 // Then, climb up the immediate dominator tree as far as we can go while 4410 // still being dominated by the input positions. 4411 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs); 4412 4413 // Don't insert instructions before PHI nodes. 4414 while (isa<PHINode>(IP)) ++IP; 4415 4416 // Ignore landingpad instructions. 4417 while (IP->isEHPad()) ++IP; 4418 4419 // Ignore debug intrinsics. 4420 while (isa<DbgInfoIntrinsic>(IP)) ++IP; 4421 4422 // Set IP below instructions recently inserted by SCEVExpander. This keeps the 4423 // IP consistent across expansions and allows the previously inserted 4424 // instructions to be reused by subsequent expansion. 4425 while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP) 4426 ++IP; 4427 4428 return IP; 4429 } 4430 4431 /// Emit instructions for the leading candidate expression for this LSRUse (this 4432 /// is called "expanding"). 4433 Value *LSRInstance::Expand(const LSRFixup &LF, 4434 const Formula &F, 4435 BasicBlock::iterator IP, 4436 SCEVExpander &Rewriter, 4437 SmallVectorImpl<WeakVH> &DeadInsts) const { 4438 const LSRUse &LU = Uses[LF.LUIdx]; 4439 if (LU.RigidFormula) 4440 return LF.OperandValToReplace; 4441 4442 // Determine an input position which will be dominated by the operands and 4443 // which will dominate the result. 4444 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter); 4445 4446 // Inform the Rewriter if we have a post-increment use, so that it can 4447 // perform an advantageous expansion. 4448 Rewriter.setPostInc(LF.PostIncLoops); 4449 4450 // This is the type that the user actually needs. 4451 Type *OpTy = LF.OperandValToReplace->getType(); 4452 // This will be the type that we'll initially expand to. 4453 Type *Ty = F.getType(); 4454 if (!Ty) 4455 // No type known; just expand directly to the ultimate type. 4456 Ty = OpTy; 4457 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy)) 4458 // Expand directly to the ultimate type if it's the right size. 4459 Ty = OpTy; 4460 // This is the type to do integer arithmetic in. 4461 Type *IntTy = SE.getEffectiveSCEVType(Ty); 4462 4463 // Build up a list of operands to add together to form the full base. 4464 SmallVector<const SCEV *, 8> Ops; 4465 4466 // Expand the BaseRegs portion. 4467 for (const SCEV *Reg : F.BaseRegs) { 4468 assert(!Reg->isZero() && "Zero allocated in a base register!"); 4469 4470 // If we're expanding for a post-inc user, make the post-inc adjustment. 4471 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); 4472 Reg = TransformForPostIncUse(Denormalize, Reg, 4473 LF.UserInst, LF.OperandValToReplace, 4474 Loops, SE, DT); 4475 4476 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr, &*IP))); 4477 } 4478 4479 // Expand the ScaledReg portion. 4480 Value *ICmpScaledV = nullptr; 4481 if (F.Scale != 0) { 4482 const SCEV *ScaledS = F.ScaledReg; 4483 4484 // If we're expanding for a post-inc user, make the post-inc adjustment. 4485 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); 4486 ScaledS = TransformForPostIncUse(Denormalize, ScaledS, 4487 LF.UserInst, LF.OperandValToReplace, 4488 Loops, SE, DT); 4489 4490 if (LU.Kind == LSRUse::ICmpZero) { 4491 // Expand ScaleReg as if it was part of the base regs. 4492 if (F.Scale == 1) 4493 Ops.push_back( 4494 SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr, &*IP))); 4495 else { 4496 // An interesting way of "folding" with an icmp is to use a negated 4497 // scale, which we'll implement by inserting it into the other operand 4498 // of the icmp. 4499 assert(F.Scale == -1 && 4500 "The only scale supported by ICmpZero uses is -1!"); 4501 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr, &*IP); 4502 } 4503 } else { 4504 // Otherwise just expand the scaled register and an explicit scale, 4505 // which is expected to be matched as part of the address. 4506 4507 // Flush the operand list to suppress SCEVExpander hoisting address modes. 4508 // Unless the addressing mode will not be folded. 4509 if (!Ops.empty() && LU.Kind == LSRUse::Address && 4510 isAMCompletelyFolded(TTI, LU, F)) { 4511 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, &*IP); 4512 Ops.clear(); 4513 Ops.push_back(SE.getUnknown(FullV)); 4514 } 4515 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr, &*IP)); 4516 if (F.Scale != 1) 4517 ScaledS = 4518 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale)); 4519 Ops.push_back(ScaledS); 4520 } 4521 } 4522 4523 // Expand the GV portion. 4524 if (F.BaseGV) { 4525 // Flush the operand list to suppress SCEVExpander hoisting. 4526 if (!Ops.empty()) { 4527 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, &*IP); 4528 Ops.clear(); 4529 Ops.push_back(SE.getUnknown(FullV)); 4530 } 4531 Ops.push_back(SE.getUnknown(F.BaseGV)); 4532 } 4533 4534 // Flush the operand list to suppress SCEVExpander hoisting of both folded and 4535 // unfolded offsets. LSR assumes they both live next to their uses. 4536 if (!Ops.empty()) { 4537 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, &*IP); 4538 Ops.clear(); 4539 Ops.push_back(SE.getUnknown(FullV)); 4540 } 4541 4542 // Expand the immediate portion. 4543 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset; 4544 if (Offset != 0) { 4545 if (LU.Kind == LSRUse::ICmpZero) { 4546 // The other interesting way of "folding" with an ICmpZero is to use a 4547 // negated immediate. 4548 if (!ICmpScaledV) 4549 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset); 4550 else { 4551 Ops.push_back(SE.getUnknown(ICmpScaledV)); 4552 ICmpScaledV = ConstantInt::get(IntTy, Offset); 4553 } 4554 } else { 4555 // Just add the immediate values. These again are expected to be matched 4556 // as part of the address. 4557 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset))); 4558 } 4559 } 4560 4561 // Expand the unfolded offset portion. 4562 int64_t UnfoldedOffset = F.UnfoldedOffset; 4563 if (UnfoldedOffset != 0) { 4564 // Just add the immediate values. 4565 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, 4566 UnfoldedOffset))); 4567 } 4568 4569 // Emit instructions summing all the operands. 4570 const SCEV *FullS = Ops.empty() ? 4571 SE.getConstant(IntTy, 0) : 4572 SE.getAddExpr(Ops); 4573 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, &*IP); 4574 4575 // We're done expanding now, so reset the rewriter. 4576 Rewriter.clearPostInc(); 4577 4578 // An ICmpZero Formula represents an ICmp which we're handling as a 4579 // comparison against zero. Now that we've expanded an expression for that 4580 // form, update the ICmp's other operand. 4581 if (LU.Kind == LSRUse::ICmpZero) { 4582 ICmpInst *CI = cast<ICmpInst>(LF.UserInst); 4583 DeadInsts.emplace_back(CI->getOperand(1)); 4584 assert(!F.BaseGV && "ICmp does not support folding a global value and " 4585 "a scale at the same time!"); 4586 if (F.Scale == -1) { 4587 if (ICmpScaledV->getType() != OpTy) { 4588 Instruction *Cast = 4589 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false, 4590 OpTy, false), 4591 ICmpScaledV, OpTy, "tmp", CI); 4592 ICmpScaledV = Cast; 4593 } 4594 CI->setOperand(1, ICmpScaledV); 4595 } else { 4596 // A scale of 1 means that the scale has been expanded as part of the 4597 // base regs. 4598 assert((F.Scale == 0 || F.Scale == 1) && 4599 "ICmp does not support folding a global value and " 4600 "a scale at the same time!"); 4601 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy), 4602 -(uint64_t)Offset); 4603 if (C->getType() != OpTy) 4604 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 4605 OpTy, false), 4606 C, OpTy); 4607 4608 CI->setOperand(1, C); 4609 } 4610 } 4611 4612 return FullV; 4613 } 4614 4615 /// Helper for Rewrite. PHI nodes are special because the use of their operands 4616 /// effectively happens in their predecessor blocks, so the expression may need 4617 /// to be expanded in multiple places. 4618 void LSRInstance::RewriteForPHI(PHINode *PN, 4619 const LSRFixup &LF, 4620 const Formula &F, 4621 SCEVExpander &Rewriter, 4622 SmallVectorImpl<WeakVH> &DeadInsts) const { 4623 DenseMap<BasicBlock *, Value *> Inserted; 4624 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 4625 if (PN->getIncomingValue(i) == LF.OperandValToReplace) { 4626 BasicBlock *BB = PN->getIncomingBlock(i); 4627 4628 // If this is a critical edge, split the edge so that we do not insert 4629 // the code on all predecessor/successor paths. We do this unless this 4630 // is the canonical backedge for this loop, which complicates post-inc 4631 // users. 4632 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 && 4633 !isa<IndirectBrInst>(BB->getTerminator())) { 4634 BasicBlock *Parent = PN->getParent(); 4635 Loop *PNLoop = LI.getLoopFor(Parent); 4636 if (!PNLoop || Parent != PNLoop->getHeader()) { 4637 // Split the critical edge. 4638 BasicBlock *NewBB = nullptr; 4639 if (!Parent->isLandingPad()) { 4640 NewBB = SplitCriticalEdge(BB, Parent, 4641 CriticalEdgeSplittingOptions(&DT, &LI) 4642 .setMergeIdenticalEdges() 4643 .setDontDeleteUselessPHIs()); 4644 } else { 4645 SmallVector<BasicBlock*, 2> NewBBs; 4646 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI); 4647 NewBB = NewBBs[0]; 4648 } 4649 // If NewBB==NULL, then SplitCriticalEdge refused to split because all 4650 // phi predecessors are identical. The simple thing to do is skip 4651 // splitting in this case rather than complicate the API. 4652 if (NewBB) { 4653 // If PN is outside of the loop and BB is in the loop, we want to 4654 // move the block to be immediately before the PHI block, not 4655 // immediately after BB. 4656 if (L->contains(BB) && !L->contains(PN)) 4657 NewBB->moveBefore(PN->getParent()); 4658 4659 // Splitting the edge can reduce the number of PHI entries we have. 4660 e = PN->getNumIncomingValues(); 4661 BB = NewBB; 4662 i = PN->getBasicBlockIndex(BB); 4663 } 4664 } 4665 } 4666 4667 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair = 4668 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr))); 4669 if (!Pair.second) 4670 PN->setIncomingValue(i, Pair.first->second); 4671 else { 4672 Value *FullV = Expand(LF, F, BB->getTerminator()->getIterator(), 4673 Rewriter, DeadInsts); 4674 4675 // If this is reuse-by-noop-cast, insert the noop cast. 4676 Type *OpTy = LF.OperandValToReplace->getType(); 4677 if (FullV->getType() != OpTy) 4678 FullV = 4679 CastInst::Create(CastInst::getCastOpcode(FullV, false, 4680 OpTy, false), 4681 FullV, LF.OperandValToReplace->getType(), 4682 "tmp", BB->getTerminator()); 4683 4684 PN->setIncomingValue(i, FullV); 4685 Pair.first->second = FullV; 4686 } 4687 } 4688 } 4689 4690 /// Emit instructions for the leading candidate expression for this LSRUse (this 4691 /// is called "expanding"), and update the UserInst to reference the newly 4692 /// expanded value. 4693 void LSRInstance::Rewrite(const LSRFixup &LF, 4694 const Formula &F, 4695 SCEVExpander &Rewriter, 4696 SmallVectorImpl<WeakVH> &DeadInsts) const { 4697 // First, find an insertion point that dominates UserInst. For PHI nodes, 4698 // find the nearest block which dominates all the relevant uses. 4699 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) { 4700 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts); 4701 } else { 4702 Value *FullV = 4703 Expand(LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts); 4704 4705 // If this is reuse-by-noop-cast, insert the noop cast. 4706 Type *OpTy = LF.OperandValToReplace->getType(); 4707 if (FullV->getType() != OpTy) { 4708 Instruction *Cast = 4709 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false), 4710 FullV, OpTy, "tmp", LF.UserInst); 4711 FullV = Cast; 4712 } 4713 4714 // Update the user. ICmpZero is handled specially here (for now) because 4715 // Expand may have updated one of the operands of the icmp already, and 4716 // its new value may happen to be equal to LF.OperandValToReplace, in 4717 // which case doing replaceUsesOfWith leads to replacing both operands 4718 // with the same value. TODO: Reorganize this. 4719 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero) 4720 LF.UserInst->setOperand(0, FullV); 4721 else 4722 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV); 4723 } 4724 4725 DeadInsts.emplace_back(LF.OperandValToReplace); 4726 } 4727 4728 /// Rewrite all the fixup locations with new values, following the chosen 4729 /// solution. 4730 void LSRInstance::ImplementSolution( 4731 const SmallVectorImpl<const Formula *> &Solution) { 4732 // Keep track of instructions we may have made dead, so that 4733 // we can remove them after we are done working. 4734 SmallVector<WeakVH, 16> DeadInsts; 4735 4736 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(), 4737 "lsr"); 4738 #ifndef NDEBUG 4739 Rewriter.setDebugType(DEBUG_TYPE); 4740 #endif 4741 Rewriter.disableCanonicalMode(); 4742 Rewriter.enableLSRMode(); 4743 Rewriter.setIVIncInsertPos(L, IVIncInsertPos); 4744 4745 // Mark phi nodes that terminate chains so the expander tries to reuse them. 4746 for (const IVChain &Chain : IVChainVec) { 4747 if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst())) 4748 Rewriter.setChainedPhi(PN); 4749 } 4750 4751 // Expand the new value definitions and update the users. 4752 for (const LSRFixup &Fixup : Fixups) { 4753 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts); 4754 4755 Changed = true; 4756 } 4757 4758 for (const IVChain &Chain : IVChainVec) { 4759 GenerateIVChain(Chain, Rewriter, DeadInsts); 4760 Changed = true; 4761 } 4762 // Clean up after ourselves. This must be done before deleting any 4763 // instructions. 4764 Rewriter.clear(); 4765 4766 Changed |= DeleteTriviallyDeadInstructions(DeadInsts); 4767 } 4768 4769 LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, 4770 DominatorTree &DT, LoopInfo &LI, 4771 const TargetTransformInfo &TTI) 4772 : IU(IU), SE(SE), DT(DT), LI(LI), TTI(TTI), L(L), Changed(false), 4773 IVIncInsertPos(nullptr) { 4774 // If LoopSimplify form is not available, stay out of trouble. 4775 if (!L->isLoopSimplifyForm()) 4776 return; 4777 4778 // If there's no interesting work to be done, bail early. 4779 if (IU.empty()) return; 4780 4781 // If there's too much analysis to be done, bail early. We won't be able to 4782 // model the problem anyway. 4783 unsigned NumUsers = 0; 4784 for (const IVStrideUse &U : IU) { 4785 if (++NumUsers > MaxIVUsers) { 4786 (void)U; 4787 DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << U << "\n"); 4788 return; 4789 } 4790 // Bail out if we have a PHI on an EHPad that gets a value from a 4791 // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is 4792 // no good place to stick any instructions. 4793 if (auto *PN = dyn_cast<PHINode>(U.getUser())) { 4794 auto *FirstNonPHI = PN->getParent()->getFirstNonPHI(); 4795 if (isa<FuncletPadInst>(FirstNonPHI) || 4796 isa<CatchSwitchInst>(FirstNonPHI)) 4797 for (BasicBlock *PredBB : PN->blocks()) 4798 if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI())) 4799 return; 4800 } 4801 } 4802 4803 #ifndef NDEBUG 4804 // All dominating loops must have preheaders, or SCEVExpander may not be able 4805 // to materialize an AddRecExpr whose Start is an outer AddRecExpr. 4806 // 4807 // IVUsers analysis should only create users that are dominated by simple loop 4808 // headers. Since this loop should dominate all of its users, its user list 4809 // should be empty if this loop itself is not within a simple loop nest. 4810 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader()); 4811 Rung; Rung = Rung->getIDom()) { 4812 BasicBlock *BB = Rung->getBlock(); 4813 const Loop *DomLoop = LI.getLoopFor(BB); 4814 if (DomLoop && DomLoop->getHeader() == BB) { 4815 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest"); 4816 } 4817 } 4818 #endif // DEBUG 4819 4820 DEBUG(dbgs() << "\nLSR on loop "; 4821 L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false); 4822 dbgs() << ":\n"); 4823 4824 // First, perform some low-level loop optimizations. 4825 OptimizeShadowIV(); 4826 OptimizeLoopTermCond(); 4827 4828 // If loop preparation eliminates all interesting IV users, bail. 4829 if (IU.empty()) return; 4830 4831 // Skip nested loops until we can model them better with formulae. 4832 if (!L->empty()) { 4833 DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n"); 4834 return; 4835 } 4836 4837 // Start collecting data and preparing for the solver. 4838 CollectChains(); 4839 CollectInterestingTypesAndFactors(); 4840 CollectFixupsAndInitialFormulae(); 4841 CollectLoopInvariantFixupsAndFormulae(); 4842 4843 assert(!Uses.empty() && "IVUsers reported at least one use"); 4844 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n"; 4845 print_uses(dbgs())); 4846 4847 // Now use the reuse data to generate a bunch of interesting ways 4848 // to formulate the values needed for the uses. 4849 GenerateAllReuseFormulae(); 4850 4851 FilterOutUndesirableDedicatedRegisters(); 4852 NarrowSearchSpaceUsingHeuristics(); 4853 4854 SmallVector<const Formula *, 8> Solution; 4855 Solve(Solution); 4856 4857 // Release memory that is no longer needed. 4858 Factors.clear(); 4859 Types.clear(); 4860 RegUses.clear(); 4861 4862 if (Solution.empty()) 4863 return; 4864 4865 #ifndef NDEBUG 4866 // Formulae should be legal. 4867 for (const LSRUse &LU : Uses) { 4868 for (const Formula &F : LU.Formulae) 4869 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, 4870 F) && "Illegal formula generated!"); 4871 }; 4872 #endif 4873 4874 // Now that we've decided what we want, make it so. 4875 ImplementSolution(Solution); 4876 } 4877 4878 void LSRInstance::print_factors_and_types(raw_ostream &OS) const { 4879 if (Factors.empty() && Types.empty()) return; 4880 4881 OS << "LSR has identified the following interesting factors and types: "; 4882 bool First = true; 4883 4884 for (int64_t Factor : Factors) { 4885 if (!First) OS << ", "; 4886 First = false; 4887 OS << '*' << Factor; 4888 } 4889 4890 for (Type *Ty : Types) { 4891 if (!First) OS << ", "; 4892 First = false; 4893 OS << '(' << *Ty << ')'; 4894 } 4895 OS << '\n'; 4896 } 4897 4898 void LSRInstance::print_fixups(raw_ostream &OS) const { 4899 OS << "LSR is examining the following fixup sites:\n"; 4900 for (const LSRFixup &LF : Fixups) { 4901 dbgs() << " "; 4902 LF.print(OS); 4903 OS << '\n'; 4904 } 4905 } 4906 4907 void LSRInstance::print_uses(raw_ostream &OS) const { 4908 OS << "LSR is examining the following uses:\n"; 4909 for (const LSRUse &LU : Uses) { 4910 dbgs() << " "; 4911 LU.print(OS); 4912 OS << '\n'; 4913 for (const Formula &F : LU.Formulae) { 4914 OS << " "; 4915 F.print(OS); 4916 OS << '\n'; 4917 } 4918 } 4919 } 4920 4921 void LSRInstance::print(raw_ostream &OS) const { 4922 print_factors_and_types(OS); 4923 print_fixups(OS); 4924 print_uses(OS); 4925 } 4926 4927 LLVM_DUMP_METHOD 4928 void LSRInstance::dump() const { 4929 print(errs()); errs() << '\n'; 4930 } 4931 4932 namespace { 4933 4934 class LoopStrengthReduce : public LoopPass { 4935 public: 4936 static char ID; // Pass ID, replacement for typeid 4937 LoopStrengthReduce(); 4938 4939 private: 4940 bool runOnLoop(Loop *L, LPPassManager &LPM) override; 4941 void getAnalysisUsage(AnalysisUsage &AU) const override; 4942 }; 4943 4944 } 4945 4946 char LoopStrengthReduce::ID = 0; 4947 INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce", 4948 "Loop Strength Reduction", false, false) 4949 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) 4950 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 4951 INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass) 4952 INITIALIZE_PASS_DEPENDENCY(IVUsers) 4953 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) 4954 INITIALIZE_PASS_DEPENDENCY(LoopSimplify) 4955 INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce", 4956 "Loop Strength Reduction", false, false) 4957 4958 4959 Pass *llvm::createLoopStrengthReducePass() { 4960 return new LoopStrengthReduce(); 4961 } 4962 4963 LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) { 4964 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry()); 4965 } 4966 4967 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const { 4968 // We split critical edges, so we change the CFG. However, we do update 4969 // many analyses if they are around. 4970 AU.addPreservedID(LoopSimplifyID); 4971 4972 AU.addRequired<LoopInfoWrapperPass>(); 4973 AU.addPreserved<LoopInfoWrapperPass>(); 4974 AU.addRequiredID(LoopSimplifyID); 4975 AU.addRequired<DominatorTreeWrapperPass>(); 4976 AU.addPreserved<DominatorTreeWrapperPass>(); 4977 AU.addRequired<ScalarEvolutionWrapperPass>(); 4978 AU.addPreserved<ScalarEvolutionWrapperPass>(); 4979 // Requiring LoopSimplify a second time here prevents IVUsers from running 4980 // twice, since LoopSimplify was invalidated by running ScalarEvolution. 4981 AU.addRequiredID(LoopSimplifyID); 4982 AU.addRequired<IVUsers>(); 4983 AU.addPreserved<IVUsers>(); 4984 AU.addRequired<TargetTransformInfoWrapperPass>(); 4985 } 4986 4987 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) { 4988 if (skipLoop(L)) 4989 return false; 4990 4991 auto &IU = getAnalysis<IVUsers>(); 4992 auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE(); 4993 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 4994 auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); 4995 const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI( 4996 *L->getHeader()->getParent()); 4997 bool Changed = false; 4998 4999 // Run the main LSR transformation. 5000 Changed |= LSRInstance(L, IU, SE, DT, LI, TTI).getChanged(); 5001 5002 // Remove any extra phis created by processing inner loops. 5003 Changed |= DeleteDeadPHIs(L->getHeader()); 5004 if (EnablePhiElim && L->isLoopSimplifyForm()) { 5005 SmallVector<WeakVH, 16> DeadInsts; 5006 const DataLayout &DL = L->getHeader()->getModule()->getDataLayout(); 5007 SCEVExpander Rewriter(getAnalysis<ScalarEvolutionWrapperPass>().getSE(), DL, 5008 "lsr"); 5009 #ifndef NDEBUG 5010 Rewriter.setDebugType(DEBUG_TYPE); 5011 #endif 5012 unsigned numFolded = Rewriter.replaceCongruentIVs( 5013 L, &getAnalysis<DominatorTreeWrapperPass>().getDomTree(), DeadInsts, 5014 &getAnalysis<TargetTransformInfoWrapperPass>().getTTI( 5015 *L->getHeader()->getParent())); 5016 if (numFolded) { 5017 Changed = true; 5018 DeleteTriviallyDeadInstructions(DeadInsts); 5019 DeleteDeadPHIs(L->getHeader()); 5020 } 5021 } 5022 return Changed; 5023 } 5024