LoopStrengthReduce.cpp revision 9fc5cdf77c812aaa80419036de27576d45894d0d
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 TargetLowering::AddrMode::BaseGV be changed to a ConstantExpr 41// instead 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#define DEBUG_TYPE "loop-reduce" 57#include "llvm/Transforms/Scalar.h" 58#include "llvm/Constants.h" 59#include "llvm/Instructions.h" 60#include "llvm/IntrinsicInst.h" 61#include "llvm/DerivedTypes.h" 62#include "llvm/Analysis/IVUsers.h" 63#include "llvm/Analysis/Dominators.h" 64#include "llvm/Analysis/LoopPass.h" 65#include "llvm/Analysis/ScalarEvolutionExpander.h" 66#include "llvm/Assembly/Writer.h" 67#include "llvm/Transforms/Utils/BasicBlockUtils.h" 68#include "llvm/Transforms/Utils/Local.h" 69#include "llvm/ADT/SmallBitVector.h" 70#include "llvm/ADT/SetVector.h" 71#include "llvm/ADT/DenseSet.h" 72#include "llvm/Support/Debug.h" 73#include "llvm/Support/ValueHandle.h" 74#include "llvm/Support/raw_ostream.h" 75#include "llvm/Target/TargetLowering.h" 76#include <algorithm> 77using namespace llvm; 78 79namespace { 80 81/// RegSortData - This class holds data which is used to order reuse candidates. 82class RegSortData { 83public: 84 /// UsedByIndices - This represents the set of LSRUse indices which reference 85 /// a particular register. 86 SmallBitVector UsedByIndices; 87 88 RegSortData() {} 89 90 void print(raw_ostream &OS) const; 91 void dump() const; 92}; 93 94} 95 96void RegSortData::print(raw_ostream &OS) const { 97 OS << "[NumUses=" << UsedByIndices.count() << ']'; 98} 99 100void RegSortData::dump() const { 101 print(errs()); errs() << '\n'; 102} 103 104namespace { 105 106/// RegUseTracker - Map register candidates to information about how they are 107/// used. 108class RegUseTracker { 109 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy; 110 111 RegUsesTy RegUsesMap; 112 SmallVector<const SCEV *, 16> RegSequence; 113 114public: 115 void CountRegister(const SCEV *Reg, size_t LUIdx); 116 void DropRegister(const SCEV *Reg, size_t LUIdx); 117 void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx); 118 119 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const; 120 121 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const; 122 123 void clear(); 124 125 typedef SmallVectorImpl<const SCEV *>::iterator iterator; 126 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator; 127 iterator begin() { return RegSequence.begin(); } 128 iterator end() { return RegSequence.end(); } 129 const_iterator begin() const { return RegSequence.begin(); } 130 const_iterator end() const { return RegSequence.end(); } 131}; 132 133} 134 135void 136RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) { 137 std::pair<RegUsesTy::iterator, bool> Pair = 138 RegUsesMap.insert(std::make_pair(Reg, RegSortData())); 139 RegSortData &RSD = Pair.first->second; 140 if (Pair.second) 141 RegSequence.push_back(Reg); 142 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1)); 143 RSD.UsedByIndices.set(LUIdx); 144} 145 146void 147RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) { 148 RegUsesTy::iterator It = RegUsesMap.find(Reg); 149 assert(It != RegUsesMap.end()); 150 RegSortData &RSD = It->second; 151 assert(RSD.UsedByIndices.size() > LUIdx); 152 RSD.UsedByIndices.reset(LUIdx); 153} 154 155void 156RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) { 157 assert(LUIdx <= LastLUIdx); 158 159 // Update RegUses. The data structure is not optimized for this purpose; 160 // we must iterate through it and update each of the bit vectors. 161 for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end(); 162 I != E; ++I) { 163 SmallBitVector &UsedByIndices = I->second.UsedByIndices; 164 if (LUIdx < UsedByIndices.size()) 165 UsedByIndices[LUIdx] = 166 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0; 167 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx)); 168 } 169} 170 171bool 172RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const { 173 RegUsesTy::const_iterator I = RegUsesMap.find(Reg); 174 if (I == RegUsesMap.end()) 175 return false; 176 const SmallBitVector &UsedByIndices = I->second.UsedByIndices; 177 int i = UsedByIndices.find_first(); 178 if (i == -1) return false; 179 if ((size_t)i != LUIdx) return true; 180 return UsedByIndices.find_next(i) != -1; 181} 182 183const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const { 184 RegUsesTy::const_iterator I = RegUsesMap.find(Reg); 185 assert(I != RegUsesMap.end() && "Unknown register!"); 186 return I->second.UsedByIndices; 187} 188 189void RegUseTracker::clear() { 190 RegUsesMap.clear(); 191 RegSequence.clear(); 192} 193 194namespace { 195 196/// Formula - This class holds information that describes a formula for 197/// computing satisfying a use. It may include broken-out immediates and scaled 198/// registers. 199struct Formula { 200 /// AM - This is used to represent complex addressing, as well as other kinds 201 /// of interesting uses. 202 TargetLowering::AddrMode AM; 203 204 /// BaseRegs - The list of "base" registers for this use. When this is 205 /// non-empty, AM.HasBaseReg should be set to true. 206 SmallVector<const SCEV *, 2> BaseRegs; 207 208 /// ScaledReg - The 'scaled' register for this use. This should be non-null 209 /// when AM.Scale is not zero. 210 const SCEV *ScaledReg; 211 212 Formula() : ScaledReg(0) {} 213 214 void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE); 215 216 unsigned getNumRegs() const; 217 const Type *getType() const; 218 219 void DeleteBaseReg(const SCEV *&S); 220 221 bool referencesReg(const SCEV *S) const; 222 bool hasRegsUsedByUsesOtherThan(size_t LUIdx, 223 const RegUseTracker &RegUses) const; 224 225 void print(raw_ostream &OS) const; 226 void dump() const; 227}; 228 229} 230 231/// DoInitialMatch - Recursion helper for InitialMatch. 232static void DoInitialMatch(const SCEV *S, Loop *L, 233 SmallVectorImpl<const SCEV *> &Good, 234 SmallVectorImpl<const SCEV *> &Bad, 235 ScalarEvolution &SE) { 236 // Collect expressions which properly dominate the loop header. 237 if (SE.properlyDominates(S, L->getHeader())) { 238 Good.push_back(S); 239 return; 240 } 241 242 // Look at add operands. 243 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 244 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 245 I != E; ++I) 246 DoInitialMatch(*I, L, Good, Bad, SE); 247 return; 248 } 249 250 // Look at addrec operands. 251 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) 252 if (!AR->getStart()->isZero()) { 253 DoInitialMatch(AR->getStart(), L, Good, Bad, SE); 254 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0), 255 AR->getStepRecurrence(SE), 256 AR->getLoop()), 257 L, Good, Bad, SE); 258 return; 259 } 260 261 // Handle a multiplication by -1 (negation) if it didn't fold. 262 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) 263 if (Mul->getOperand(0)->isAllOnesValue()) { 264 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end()); 265 const SCEV *NewMul = SE.getMulExpr(Ops); 266 267 SmallVector<const SCEV *, 4> MyGood; 268 SmallVector<const SCEV *, 4> MyBad; 269 DoInitialMatch(NewMul, L, MyGood, MyBad, SE); 270 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue( 271 SE.getEffectiveSCEVType(NewMul->getType()))); 272 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(), 273 E = MyGood.end(); I != E; ++I) 274 Good.push_back(SE.getMulExpr(NegOne, *I)); 275 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(), 276 E = MyBad.end(); I != E; ++I) 277 Bad.push_back(SE.getMulExpr(NegOne, *I)); 278 return; 279 } 280 281 // Ok, we can't do anything interesting. Just stuff the whole thing into a 282 // register and hope for the best. 283 Bad.push_back(S); 284} 285 286/// InitialMatch - Incorporate loop-variant parts of S into this Formula, 287/// attempting to keep all loop-invariant and loop-computable values in a 288/// single base register. 289void Formula::InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) { 290 SmallVector<const SCEV *, 4> Good; 291 SmallVector<const SCEV *, 4> Bad; 292 DoInitialMatch(S, L, Good, Bad, SE); 293 if (!Good.empty()) { 294 const SCEV *Sum = SE.getAddExpr(Good); 295 if (!Sum->isZero()) 296 BaseRegs.push_back(Sum); 297 AM.HasBaseReg = true; 298 } 299 if (!Bad.empty()) { 300 const SCEV *Sum = SE.getAddExpr(Bad); 301 if (!Sum->isZero()) 302 BaseRegs.push_back(Sum); 303 AM.HasBaseReg = true; 304 } 305} 306 307/// getNumRegs - Return the total number of register operands used by this 308/// formula. This does not include register uses implied by non-constant 309/// addrec strides. 310unsigned Formula::getNumRegs() const { 311 return !!ScaledReg + BaseRegs.size(); 312} 313 314/// getType - Return the type of this formula, if it has one, or null 315/// otherwise. This type is meaningless except for the bit size. 316const Type *Formula::getType() const { 317 return !BaseRegs.empty() ? BaseRegs.front()->getType() : 318 ScaledReg ? ScaledReg->getType() : 319 AM.BaseGV ? AM.BaseGV->getType() : 320 0; 321} 322 323/// DeleteBaseReg - Delete the given base reg from the BaseRegs list. 324void Formula::DeleteBaseReg(const SCEV *&S) { 325 if (&S != &BaseRegs.back()) 326 std::swap(S, BaseRegs.back()); 327 BaseRegs.pop_back(); 328} 329 330/// referencesReg - Test if this formula references the given register. 331bool Formula::referencesReg(const SCEV *S) const { 332 return S == ScaledReg || 333 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end(); 334} 335 336/// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers 337/// which are used by uses other than the use with the given index. 338bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx, 339 const RegUseTracker &RegUses) const { 340 if (ScaledReg) 341 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx)) 342 return true; 343 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(), 344 E = BaseRegs.end(); I != E; ++I) 345 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx)) 346 return true; 347 return false; 348} 349 350void Formula::print(raw_ostream &OS) const { 351 bool First = true; 352 if (AM.BaseGV) { 353 if (!First) OS << " + "; else First = false; 354 WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false); 355 } 356 if (AM.BaseOffs != 0) { 357 if (!First) OS << " + "; else First = false; 358 OS << AM.BaseOffs; 359 } 360 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(), 361 E = BaseRegs.end(); I != E; ++I) { 362 if (!First) OS << " + "; else First = false; 363 OS << "reg(" << **I << ')'; 364 } 365 if (AM.HasBaseReg && BaseRegs.empty()) { 366 if (!First) OS << " + "; else First = false; 367 OS << "**error: HasBaseReg**"; 368 } else if (!AM.HasBaseReg && !BaseRegs.empty()) { 369 if (!First) OS << " + "; else First = false; 370 OS << "**error: !HasBaseReg**"; 371 } 372 if (AM.Scale != 0) { 373 if (!First) OS << " + "; else First = false; 374 OS << AM.Scale << "*reg("; 375 if (ScaledReg) 376 OS << *ScaledReg; 377 else 378 OS << "<unknown>"; 379 OS << ')'; 380 } 381} 382 383void Formula::dump() const { 384 print(errs()); errs() << '\n'; 385} 386 387/// isAddRecSExtable - Return true if the given addrec can be sign-extended 388/// without changing its value. 389static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) { 390 const Type *WideTy = 391 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1); 392 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy)); 393} 394 395/// isAddSExtable - Return true if the given add can be sign-extended 396/// without changing its value. 397static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) { 398 const Type *WideTy = 399 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1); 400 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy)); 401} 402 403/// isMulSExtable - Return true if the given mul can be sign-extended 404/// without changing its value. 405static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) { 406 const Type *WideTy = 407 IntegerType::get(SE.getContext(), 408 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands()); 409 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy)); 410} 411 412/// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined 413/// and if the remainder is known to be zero, or null otherwise. If 414/// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified 415/// to Y, ignoring that the multiplication may overflow, which is useful when 416/// the result will be used in a context where the most significant bits are 417/// ignored. 418static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS, 419 ScalarEvolution &SE, 420 bool IgnoreSignificantBits = false) { 421 // Handle the trivial case, which works for any SCEV type. 422 if (LHS == RHS) 423 return SE.getConstant(LHS->getType(), 1); 424 425 // Handle a few RHS special cases. 426 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS); 427 if (RC) { 428 const APInt &RA = RC->getValue()->getValue(); 429 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do 430 // some folding. 431 if (RA.isAllOnesValue()) 432 return SE.getMulExpr(LHS, RC); 433 // Handle x /s 1 as x. 434 if (RA == 1) 435 return LHS; 436 } 437 438 // Check for a division of a constant by a constant. 439 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) { 440 if (!RC) 441 return 0; 442 const APInt &LA = C->getValue()->getValue(); 443 const APInt &RA = RC->getValue()->getValue(); 444 if (LA.srem(RA) != 0) 445 return 0; 446 return SE.getConstant(LA.sdiv(RA)); 447 } 448 449 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow. 450 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) { 451 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) { 452 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE, 453 IgnoreSignificantBits); 454 if (!Step) return 0; 455 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE, 456 IgnoreSignificantBits); 457 if (!Start) return 0; 458 return SE.getAddRecExpr(Start, Step, AR->getLoop()); 459 } 460 return 0; 461 } 462 463 // Distribute the sdiv over add operands, if the add doesn't overflow. 464 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) { 465 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) { 466 SmallVector<const SCEV *, 8> Ops; 467 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 468 I != E; ++I) { 469 const SCEV *Op = getExactSDiv(*I, RHS, SE, 470 IgnoreSignificantBits); 471 if (!Op) return 0; 472 Ops.push_back(Op); 473 } 474 return SE.getAddExpr(Ops); 475 } 476 return 0; 477 } 478 479 // Check for a multiply operand that we can pull RHS out of. 480 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) { 481 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) { 482 SmallVector<const SCEV *, 4> Ops; 483 bool Found = false; 484 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end(); 485 I != E; ++I) { 486 const SCEV *S = *I; 487 if (!Found) 488 if (const SCEV *Q = getExactSDiv(S, RHS, SE, 489 IgnoreSignificantBits)) { 490 S = Q; 491 Found = true; 492 } 493 Ops.push_back(S); 494 } 495 return Found ? SE.getMulExpr(Ops) : 0; 496 } 497 return 0; 498 } 499 500 // Otherwise we don't know. 501 return 0; 502} 503 504/// ExtractImmediate - If S involves the addition of a constant integer value, 505/// return that integer value, and mutate S to point to a new SCEV with that 506/// value excluded. 507static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) { 508 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) { 509 if (C->getValue()->getValue().getMinSignedBits() <= 64) { 510 S = SE.getConstant(C->getType(), 0); 511 return C->getValue()->getSExtValue(); 512 } 513 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 514 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); 515 int64_t Result = ExtractImmediate(NewOps.front(), SE); 516 if (Result != 0) 517 S = SE.getAddExpr(NewOps); 518 return Result; 519 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 520 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); 521 int64_t Result = ExtractImmediate(NewOps.front(), SE); 522 if (Result != 0) 523 S = SE.getAddRecExpr(NewOps, AR->getLoop()); 524 return Result; 525 } 526 return 0; 527} 528 529/// ExtractSymbol - If S involves the addition of a GlobalValue address, 530/// return that symbol, and mutate S to point to a new SCEV with that 531/// value excluded. 532static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) { 533 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { 534 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) { 535 S = SE.getConstant(GV->getType(), 0); 536 return GV; 537 } 538 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 539 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); 540 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE); 541 if (Result) 542 S = SE.getAddExpr(NewOps); 543 return Result; 544 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 545 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); 546 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE); 547 if (Result) 548 S = SE.getAddRecExpr(NewOps, AR->getLoop()); 549 return Result; 550 } 551 return 0; 552} 553 554/// isAddressUse - Returns true if the specified instruction is using the 555/// specified value as an address. 556static bool isAddressUse(Instruction *Inst, Value *OperandVal) { 557 bool isAddress = isa<LoadInst>(Inst); 558 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 559 if (SI->getOperand(1) == OperandVal) 560 isAddress = true; 561 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 562 // Addressing modes can also be folded into prefetches and a variety 563 // of intrinsics. 564 switch (II->getIntrinsicID()) { 565 default: break; 566 case Intrinsic::prefetch: 567 case Intrinsic::x86_sse2_loadu_dq: 568 case Intrinsic::x86_sse2_loadu_pd: 569 case Intrinsic::x86_sse_loadu_ps: 570 case Intrinsic::x86_sse_storeu_ps: 571 case Intrinsic::x86_sse2_storeu_pd: 572 case Intrinsic::x86_sse2_storeu_dq: 573 case Intrinsic::x86_sse2_storel_dq: 574 if (II->getArgOperand(0) == OperandVal) 575 isAddress = true; 576 break; 577 } 578 } 579 return isAddress; 580} 581 582/// getAccessType - Return the type of the memory being accessed. 583static const Type *getAccessType(const Instruction *Inst) { 584 const Type *AccessTy = Inst->getType(); 585 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) 586 AccessTy = SI->getOperand(0)->getType(); 587 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 588 // Addressing modes can also be folded into prefetches and a variety 589 // of intrinsics. 590 switch (II->getIntrinsicID()) { 591 default: break; 592 case Intrinsic::x86_sse_storeu_ps: 593 case Intrinsic::x86_sse2_storeu_pd: 594 case Intrinsic::x86_sse2_storeu_dq: 595 case Intrinsic::x86_sse2_storel_dq: 596 AccessTy = II->getArgOperand(0)->getType(); 597 break; 598 } 599 } 600 601 // All pointers have the same requirements, so canonicalize them to an 602 // arbitrary pointer type to minimize variation. 603 if (const PointerType *PTy = dyn_cast<PointerType>(AccessTy)) 604 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1), 605 PTy->getAddressSpace()); 606 607 return AccessTy; 608} 609 610/// DeleteTriviallyDeadInstructions - If any of the instructions is the 611/// specified set are trivially dead, delete them and see if this makes any of 612/// their operands subsequently dead. 613static bool 614DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) { 615 bool Changed = false; 616 617 while (!DeadInsts.empty()) { 618 Instruction *I = dyn_cast_or_null<Instruction>(&*DeadInsts.pop_back_val()); 619 620 if (I == 0 || !isInstructionTriviallyDead(I)) 621 continue; 622 623 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 624 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 625 *OI = 0; 626 if (U->use_empty()) 627 DeadInsts.push_back(U); 628 } 629 630 I->eraseFromParent(); 631 Changed = true; 632 } 633 634 return Changed; 635} 636 637namespace { 638 639/// Cost - This class is used to measure and compare candidate formulae. 640class Cost { 641 /// TODO: Some of these could be merged. Also, a lexical ordering 642 /// isn't always optimal. 643 unsigned NumRegs; 644 unsigned AddRecCost; 645 unsigned NumIVMuls; 646 unsigned NumBaseAdds; 647 unsigned ImmCost; 648 unsigned SetupCost; 649 650public: 651 Cost() 652 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0), 653 SetupCost(0) {} 654 655 bool operator<(const Cost &Other) const; 656 657 void Loose(); 658 659 void RateFormula(const Formula &F, 660 SmallPtrSet<const SCEV *, 16> &Regs, 661 const DenseSet<const SCEV *> &VisitedRegs, 662 const Loop *L, 663 const SmallVectorImpl<int64_t> &Offsets, 664 ScalarEvolution &SE, DominatorTree &DT); 665 666 void print(raw_ostream &OS) const; 667 void dump() const; 668 669private: 670 void RateRegister(const SCEV *Reg, 671 SmallPtrSet<const SCEV *, 16> &Regs, 672 const Loop *L, 673 ScalarEvolution &SE, DominatorTree &DT); 674 void RatePrimaryRegister(const SCEV *Reg, 675 SmallPtrSet<const SCEV *, 16> &Regs, 676 const Loop *L, 677 ScalarEvolution &SE, DominatorTree &DT); 678}; 679 680} 681 682/// RateRegister - Tally up interesting quantities from the given register. 683void Cost::RateRegister(const SCEV *Reg, 684 SmallPtrSet<const SCEV *, 16> &Regs, 685 const Loop *L, 686 ScalarEvolution &SE, DominatorTree &DT) { 687 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) { 688 if (AR->getLoop() == L) 689 AddRecCost += 1; /// TODO: This should be a function of the stride. 690 691 // If this is an addrec for a loop that's already been visited by LSR, 692 // don't second-guess its addrec phi nodes. LSR isn't currently smart 693 // enough to reason about more than one loop at a time. Consider these 694 // registers free and leave them alone. 695 else if (L->contains(AR->getLoop()) || 696 (!AR->getLoop()->contains(L) && 697 DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) { 698 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin(); 699 PHINode *PN = dyn_cast<PHINode>(I); ++I) 700 if (SE.isSCEVable(PN->getType()) && 701 (SE.getEffectiveSCEVType(PN->getType()) == 702 SE.getEffectiveSCEVType(AR->getType())) && 703 SE.getSCEV(PN) == AR) 704 return; 705 706 // If this isn't one of the addrecs that the loop already has, it 707 // would require a costly new phi and add. TODO: This isn't 708 // precisely modeled right now. 709 ++NumBaseAdds; 710 if (!Regs.count(AR->getStart())) 711 RateRegister(AR->getStart(), Regs, L, SE, DT); 712 } 713 714 // Add the step value register, if it needs one. 715 // TODO: The non-affine case isn't precisely modeled here. 716 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) 717 if (!Regs.count(AR->getStart())) 718 RateRegister(AR->getOperand(1), Regs, L, SE, DT); 719 } 720 ++NumRegs; 721 722 // Rough heuristic; favor registers which don't require extra setup 723 // instructions in the preheader. 724 if (!isa<SCEVUnknown>(Reg) && 725 !isa<SCEVConstant>(Reg) && 726 !(isa<SCEVAddRecExpr>(Reg) && 727 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) || 728 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart())))) 729 ++SetupCost; 730 731 NumIVMuls += isa<SCEVMulExpr>(Reg) && 732 SE.hasComputableLoopEvolution(Reg, L); 733} 734 735/// RatePrimaryRegister - Record this register in the set. If we haven't seen it 736/// before, rate it. 737void Cost::RatePrimaryRegister(const SCEV *Reg, 738 SmallPtrSet<const SCEV *, 16> &Regs, 739 const Loop *L, 740 ScalarEvolution &SE, DominatorTree &DT) { 741 if (Regs.insert(Reg)) 742 RateRegister(Reg, Regs, L, SE, DT); 743} 744 745void Cost::RateFormula(const Formula &F, 746 SmallPtrSet<const SCEV *, 16> &Regs, 747 const DenseSet<const SCEV *> &VisitedRegs, 748 const Loop *L, 749 const SmallVectorImpl<int64_t> &Offsets, 750 ScalarEvolution &SE, DominatorTree &DT) { 751 // Tally up the registers. 752 if (const SCEV *ScaledReg = F.ScaledReg) { 753 if (VisitedRegs.count(ScaledReg)) { 754 Loose(); 755 return; 756 } 757 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT); 758 } 759 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), 760 E = F.BaseRegs.end(); I != E; ++I) { 761 const SCEV *BaseReg = *I; 762 if (VisitedRegs.count(BaseReg)) { 763 Loose(); 764 return; 765 } 766 RatePrimaryRegister(BaseReg, Regs, L, SE, DT); 767 } 768 769 if (F.BaseRegs.size() > 1) 770 NumBaseAdds += F.BaseRegs.size() - 1; 771 772 // Tally up the non-zero immediates. 773 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(), 774 E = Offsets.end(); I != E; ++I) { 775 int64_t Offset = (uint64_t)*I + F.AM.BaseOffs; 776 if (F.AM.BaseGV) 777 ImmCost += 64; // Handle symbolic values conservatively. 778 // TODO: This should probably be the pointer size. 779 else if (Offset != 0) 780 ImmCost += APInt(64, Offset, true).getMinSignedBits(); 781 } 782} 783 784/// Loose - Set this cost to a loosing value. 785void Cost::Loose() { 786 NumRegs = ~0u; 787 AddRecCost = ~0u; 788 NumIVMuls = ~0u; 789 NumBaseAdds = ~0u; 790 ImmCost = ~0u; 791 SetupCost = ~0u; 792} 793 794/// operator< - Choose the lower cost. 795bool Cost::operator<(const Cost &Other) const { 796 if (NumRegs != Other.NumRegs) 797 return NumRegs < Other.NumRegs; 798 if (AddRecCost != Other.AddRecCost) 799 return AddRecCost < Other.AddRecCost; 800 if (NumIVMuls != Other.NumIVMuls) 801 return NumIVMuls < Other.NumIVMuls; 802 if (NumBaseAdds != Other.NumBaseAdds) 803 return NumBaseAdds < Other.NumBaseAdds; 804 if (ImmCost != Other.ImmCost) 805 return ImmCost < Other.ImmCost; 806 if (SetupCost != Other.SetupCost) 807 return SetupCost < Other.SetupCost; 808 return false; 809} 810 811void Cost::print(raw_ostream &OS) const { 812 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s"); 813 if (AddRecCost != 0) 814 OS << ", with addrec cost " << AddRecCost; 815 if (NumIVMuls != 0) 816 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s"); 817 if (NumBaseAdds != 0) 818 OS << ", plus " << NumBaseAdds << " base add" 819 << (NumBaseAdds == 1 ? "" : "s"); 820 if (ImmCost != 0) 821 OS << ", plus " << ImmCost << " imm cost"; 822 if (SetupCost != 0) 823 OS << ", plus " << SetupCost << " setup cost"; 824} 825 826void Cost::dump() const { 827 print(errs()); errs() << '\n'; 828} 829 830namespace { 831 832/// LSRFixup - An operand value in an instruction which is to be replaced 833/// with some equivalent, possibly strength-reduced, replacement. 834struct LSRFixup { 835 /// UserInst - The instruction which will be updated. 836 Instruction *UserInst; 837 838 /// OperandValToReplace - The operand of the instruction which will 839 /// be replaced. The operand may be used more than once; every instance 840 /// will be replaced. 841 Value *OperandValToReplace; 842 843 /// PostIncLoops - If this user is to use the post-incremented value of an 844 /// induction variable, this variable is non-null and holds the loop 845 /// associated with the induction variable. 846 PostIncLoopSet PostIncLoops; 847 848 /// LUIdx - The index of the LSRUse describing the expression which 849 /// this fixup needs, minus an offset (below). 850 size_t LUIdx; 851 852 /// Offset - A constant offset to be added to the LSRUse expression. 853 /// This allows multiple fixups to share the same LSRUse with different 854 /// offsets, for example in an unrolled loop. 855 int64_t Offset; 856 857 bool isUseFullyOutsideLoop(const Loop *L) const; 858 859 LSRFixup(); 860 861 void print(raw_ostream &OS) const; 862 void dump() const; 863}; 864 865} 866 867LSRFixup::LSRFixup() 868 : UserInst(0), OperandValToReplace(0), LUIdx(~size_t(0)), Offset(0) {} 869 870/// isUseFullyOutsideLoop - Test whether this fixup always uses its 871/// value outside of the given loop. 872bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const { 873 // PHI nodes use their value in their incoming blocks. 874 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) { 875 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 876 if (PN->getIncomingValue(i) == OperandValToReplace && 877 L->contains(PN->getIncomingBlock(i))) 878 return false; 879 return true; 880 } 881 882 return !L->contains(UserInst); 883} 884 885void LSRFixup::print(raw_ostream &OS) const { 886 OS << "UserInst="; 887 // Store is common and interesting enough to be worth special-casing. 888 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) { 889 OS << "store "; 890 WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false); 891 } else if (UserInst->getType()->isVoidTy()) 892 OS << UserInst->getOpcodeName(); 893 else 894 WriteAsOperand(OS, UserInst, /*PrintType=*/false); 895 896 OS << ", OperandValToReplace="; 897 WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false); 898 899 for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(), 900 E = PostIncLoops.end(); I != E; ++I) { 901 OS << ", PostIncLoop="; 902 WriteAsOperand(OS, (*I)->getHeader(), /*PrintType=*/false); 903 } 904 905 if (LUIdx != ~size_t(0)) 906 OS << ", LUIdx=" << LUIdx; 907 908 if (Offset != 0) 909 OS << ", Offset=" << Offset; 910} 911 912void LSRFixup::dump() const { 913 print(errs()); errs() << '\n'; 914} 915 916namespace { 917 918/// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding 919/// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*. 920struct UniquifierDenseMapInfo { 921 static SmallVector<const SCEV *, 2> getEmptyKey() { 922 SmallVector<const SCEV *, 2> V; 923 V.push_back(reinterpret_cast<const SCEV *>(-1)); 924 return V; 925 } 926 927 static SmallVector<const SCEV *, 2> getTombstoneKey() { 928 SmallVector<const SCEV *, 2> V; 929 V.push_back(reinterpret_cast<const SCEV *>(-2)); 930 return V; 931 } 932 933 static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) { 934 unsigned Result = 0; 935 for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(), 936 E = V.end(); I != E; ++I) 937 Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I); 938 return Result; 939 } 940 941 static bool isEqual(const SmallVector<const SCEV *, 2> &LHS, 942 const SmallVector<const SCEV *, 2> &RHS) { 943 return LHS == RHS; 944 } 945}; 946 947/// LSRUse - This class holds the state that LSR keeps for each use in 948/// IVUsers, as well as uses invented by LSR itself. It includes information 949/// about what kinds of things can be folded into the user, information about 950/// the user itself, and information about how the use may be satisfied. 951/// TODO: Represent multiple users of the same expression in common? 952class LSRUse { 953 DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier; 954 955public: 956 /// KindType - An enum for a kind of use, indicating what types of 957 /// scaled and immediate operands it might support. 958 enum KindType { 959 Basic, ///< A normal use, with no folding. 960 Special, ///< A special case of basic, allowing -1 scales. 961 Address, ///< An address use; folding according to TargetLowering 962 ICmpZero ///< An equality icmp with both operands folded into one. 963 // TODO: Add a generic icmp too? 964 }; 965 966 KindType Kind; 967 const Type *AccessTy; 968 969 SmallVector<int64_t, 8> Offsets; 970 int64_t MinOffset; 971 int64_t MaxOffset; 972 973 /// AllFixupsOutsideLoop - This records whether all of the fixups using this 974 /// LSRUse are outside of the loop, in which case some special-case heuristics 975 /// may be used. 976 bool AllFixupsOutsideLoop; 977 978 /// WidestFixupType - This records the widest use type for any fixup using 979 /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different 980 /// max fixup widths to be equivalent, because the narrower one may be relying 981 /// on the implicit truncation to truncate away bogus bits. 982 const Type *WidestFixupType; 983 984 /// Formulae - A list of ways to build a value that can satisfy this user. 985 /// After the list is populated, one of these is selected heuristically and 986 /// used to formulate a replacement for OperandValToReplace in UserInst. 987 SmallVector<Formula, 12> Formulae; 988 989 /// Regs - The set of register candidates used by all formulae in this LSRUse. 990 SmallPtrSet<const SCEV *, 4> Regs; 991 992 LSRUse(KindType K, const Type *T) : Kind(K), AccessTy(T), 993 MinOffset(INT64_MAX), 994 MaxOffset(INT64_MIN), 995 AllFixupsOutsideLoop(true), 996 WidestFixupType(0) {} 997 998 bool HasFormulaWithSameRegs(const Formula &F) const; 999 bool InsertFormula(const Formula &F); 1000 void DeleteFormula(Formula &F); 1001 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses); 1002 1003 void print(raw_ostream &OS) const; 1004 void dump() const; 1005}; 1006 1007} 1008 1009/// HasFormula - Test whether this use as a formula which has the same 1010/// registers as the given formula. 1011bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const { 1012 SmallVector<const SCEV *, 2> Key = F.BaseRegs; 1013 if (F.ScaledReg) Key.push_back(F.ScaledReg); 1014 // Unstable sort by host order ok, because this is only used for uniquifying. 1015 std::sort(Key.begin(), Key.end()); 1016 return Uniquifier.count(Key); 1017} 1018 1019/// InsertFormula - If the given formula has not yet been inserted, add it to 1020/// the list, and return true. Return false otherwise. 1021bool LSRUse::InsertFormula(const Formula &F) { 1022 SmallVector<const SCEV *, 2> Key = F.BaseRegs; 1023 if (F.ScaledReg) Key.push_back(F.ScaledReg); 1024 // Unstable sort by host order ok, because this is only used for uniquifying. 1025 std::sort(Key.begin(), Key.end()); 1026 1027 if (!Uniquifier.insert(Key).second) 1028 return false; 1029 1030 // Using a register to hold the value of 0 is not profitable. 1031 assert((!F.ScaledReg || !F.ScaledReg->isZero()) && 1032 "Zero allocated in a scaled register!"); 1033#ifndef NDEBUG 1034 for (SmallVectorImpl<const SCEV *>::const_iterator I = 1035 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) 1036 assert(!(*I)->isZero() && "Zero allocated in a base register!"); 1037#endif 1038 1039 // Add the formula to the list. 1040 Formulae.push_back(F); 1041 1042 // Record registers now being used by this use. 1043 if (F.ScaledReg) Regs.insert(F.ScaledReg); 1044 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); 1045 1046 return true; 1047} 1048 1049/// DeleteFormula - Remove the given formula from this use's list. 1050void LSRUse::DeleteFormula(Formula &F) { 1051 if (&F != &Formulae.back()) 1052 std::swap(F, Formulae.back()); 1053 Formulae.pop_back(); 1054 assert(!Formulae.empty() && "LSRUse has no formulae left!"); 1055} 1056 1057/// RecomputeRegs - Recompute the Regs field, and update RegUses. 1058void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) { 1059 // Now that we've filtered out some formulae, recompute the Regs set. 1060 SmallPtrSet<const SCEV *, 4> OldRegs = Regs; 1061 Regs.clear(); 1062 for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(), 1063 E = Formulae.end(); I != E; ++I) { 1064 const Formula &F = *I; 1065 if (F.ScaledReg) Regs.insert(F.ScaledReg); 1066 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); 1067 } 1068 1069 // Update the RegTracker. 1070 for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(), 1071 E = OldRegs.end(); I != E; ++I) 1072 if (!Regs.count(*I)) 1073 RegUses.DropRegister(*I, LUIdx); 1074} 1075 1076void LSRUse::print(raw_ostream &OS) const { 1077 OS << "LSR Use: Kind="; 1078 switch (Kind) { 1079 case Basic: OS << "Basic"; break; 1080 case Special: OS << "Special"; break; 1081 case ICmpZero: OS << "ICmpZero"; break; 1082 case Address: 1083 OS << "Address of "; 1084 if (AccessTy->isPointerTy()) 1085 OS << "pointer"; // the full pointer type could be really verbose 1086 else 1087 OS << *AccessTy; 1088 } 1089 1090 OS << ", Offsets={"; 1091 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(), 1092 E = Offsets.end(); I != E; ++I) { 1093 OS << *I; 1094 if (llvm::next(I) != E) 1095 OS << ','; 1096 } 1097 OS << '}'; 1098 1099 if (AllFixupsOutsideLoop) 1100 OS << ", all-fixups-outside-loop"; 1101 1102 if (WidestFixupType) 1103 OS << ", widest fixup type: " << *WidestFixupType; 1104} 1105 1106void LSRUse::dump() const { 1107 print(errs()); errs() << '\n'; 1108} 1109 1110/// isLegalUse - Test whether the use described by AM is "legal", meaning it can 1111/// be completely folded into the user instruction at isel time. This includes 1112/// address-mode folding and special icmp tricks. 1113static bool isLegalUse(const TargetLowering::AddrMode &AM, 1114 LSRUse::KindType Kind, const Type *AccessTy, 1115 const TargetLowering *TLI) { 1116 switch (Kind) { 1117 case LSRUse::Address: 1118 // If we have low-level target information, ask the target if it can 1119 // completely fold this address. 1120 if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy); 1121 1122 // Otherwise, just guess that reg+reg addressing is legal. 1123 return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1; 1124 1125 case LSRUse::ICmpZero: 1126 // There's not even a target hook for querying whether it would be legal to 1127 // fold a GV into an ICmp. 1128 if (AM.BaseGV) 1129 return false; 1130 1131 // ICmp only has two operands; don't allow more than two non-trivial parts. 1132 if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0) 1133 return false; 1134 1135 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by 1136 // putting the scaled register in the other operand of the icmp. 1137 if (AM.Scale != 0 && AM.Scale != -1) 1138 return false; 1139 1140 // If we have low-level target information, ask the target if it can fold an 1141 // integer immediate on an icmp. 1142 if (AM.BaseOffs != 0) { 1143 if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs); 1144 return false; 1145 } 1146 1147 return true; 1148 1149 case LSRUse::Basic: 1150 // Only handle single-register values. 1151 return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0; 1152 1153 case LSRUse::Special: 1154 // Only handle -1 scales, or no scale. 1155 return AM.Scale == 0 || AM.Scale == -1; 1156 } 1157 1158 return false; 1159} 1160 1161static bool isLegalUse(TargetLowering::AddrMode AM, 1162 int64_t MinOffset, int64_t MaxOffset, 1163 LSRUse::KindType Kind, const Type *AccessTy, 1164 const TargetLowering *TLI) { 1165 // Check for overflow. 1166 if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) != 1167 (MinOffset > 0)) 1168 return false; 1169 AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset; 1170 if (isLegalUse(AM, Kind, AccessTy, TLI)) { 1171 AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset; 1172 // Check for overflow. 1173 if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) != 1174 (MaxOffset > 0)) 1175 return false; 1176 AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset; 1177 return isLegalUse(AM, Kind, AccessTy, TLI); 1178 } 1179 return false; 1180} 1181 1182static bool isAlwaysFoldable(int64_t BaseOffs, 1183 GlobalValue *BaseGV, 1184 bool HasBaseReg, 1185 LSRUse::KindType Kind, const Type *AccessTy, 1186 const TargetLowering *TLI) { 1187 // Fast-path: zero is always foldable. 1188 if (BaseOffs == 0 && !BaseGV) return true; 1189 1190 // Conservatively, create an address with an immediate and a 1191 // base and a scale. 1192 TargetLowering::AddrMode AM; 1193 AM.BaseOffs = BaseOffs; 1194 AM.BaseGV = BaseGV; 1195 AM.HasBaseReg = HasBaseReg; 1196 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1; 1197 1198 // Canonicalize a scale of 1 to a base register if the formula doesn't 1199 // already have a base register. 1200 if (!AM.HasBaseReg && AM.Scale == 1) { 1201 AM.Scale = 0; 1202 AM.HasBaseReg = true; 1203 } 1204 1205 return isLegalUse(AM, Kind, AccessTy, TLI); 1206} 1207 1208static bool isAlwaysFoldable(const SCEV *S, 1209 int64_t MinOffset, int64_t MaxOffset, 1210 bool HasBaseReg, 1211 LSRUse::KindType Kind, const Type *AccessTy, 1212 const TargetLowering *TLI, 1213 ScalarEvolution &SE) { 1214 // Fast-path: zero is always foldable. 1215 if (S->isZero()) return true; 1216 1217 // Conservatively, create an address with an immediate and a 1218 // base and a scale. 1219 int64_t BaseOffs = ExtractImmediate(S, SE); 1220 GlobalValue *BaseGV = ExtractSymbol(S, SE); 1221 1222 // If there's anything else involved, it's not foldable. 1223 if (!S->isZero()) return false; 1224 1225 // Fast-path: zero is always foldable. 1226 if (BaseOffs == 0 && !BaseGV) return true; 1227 1228 // Conservatively, create an address with an immediate and a 1229 // base and a scale. 1230 TargetLowering::AddrMode AM; 1231 AM.BaseOffs = BaseOffs; 1232 AM.BaseGV = BaseGV; 1233 AM.HasBaseReg = HasBaseReg; 1234 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1; 1235 1236 return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI); 1237} 1238 1239namespace { 1240 1241/// UseMapDenseMapInfo - A DenseMapInfo implementation for holding 1242/// DenseMaps and DenseSets of pairs of const SCEV* and LSRUse::Kind. 1243struct UseMapDenseMapInfo { 1244 static std::pair<const SCEV *, LSRUse::KindType> getEmptyKey() { 1245 return std::make_pair(reinterpret_cast<const SCEV *>(-1), LSRUse::Basic); 1246 } 1247 1248 static std::pair<const SCEV *, LSRUse::KindType> getTombstoneKey() { 1249 return std::make_pair(reinterpret_cast<const SCEV *>(-2), LSRUse::Basic); 1250 } 1251 1252 static unsigned 1253 getHashValue(const std::pair<const SCEV *, LSRUse::KindType> &V) { 1254 unsigned Result = DenseMapInfo<const SCEV *>::getHashValue(V.first); 1255 Result ^= DenseMapInfo<unsigned>::getHashValue(unsigned(V.second)); 1256 return Result; 1257 } 1258 1259 static bool isEqual(const std::pair<const SCEV *, LSRUse::KindType> &LHS, 1260 const std::pair<const SCEV *, LSRUse::KindType> &RHS) { 1261 return LHS == RHS; 1262 } 1263}; 1264 1265/// LSRInstance - This class holds state for the main loop strength reduction 1266/// logic. 1267class LSRInstance { 1268 IVUsers &IU; 1269 ScalarEvolution &SE; 1270 DominatorTree &DT; 1271 LoopInfo &LI; 1272 const TargetLowering *const TLI; 1273 Loop *const L; 1274 bool Changed; 1275 1276 /// IVIncInsertPos - This is the insert position that the current loop's 1277 /// induction variable increment should be placed. In simple loops, this is 1278 /// the latch block's terminator. But in more complicated cases, this is a 1279 /// position which will dominate all the in-loop post-increment users. 1280 Instruction *IVIncInsertPos; 1281 1282 /// Factors - Interesting factors between use strides. 1283 SmallSetVector<int64_t, 8> Factors; 1284 1285 /// Types - Interesting use types, to facilitate truncation reuse. 1286 SmallSetVector<const Type *, 4> Types; 1287 1288 /// Fixups - The list of operands which are to be replaced. 1289 SmallVector<LSRFixup, 16> Fixups; 1290 1291 /// Uses - The list of interesting uses. 1292 SmallVector<LSRUse, 16> Uses; 1293 1294 /// RegUses - Track which uses use which register candidates. 1295 RegUseTracker RegUses; 1296 1297 void OptimizeShadowIV(); 1298 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse); 1299 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse); 1300 void OptimizeLoopTermCond(); 1301 1302 void CollectInterestingTypesAndFactors(); 1303 void CollectFixupsAndInitialFormulae(); 1304 1305 LSRFixup &getNewFixup() { 1306 Fixups.push_back(LSRFixup()); 1307 return Fixups.back(); 1308 } 1309 1310 // Support for sharing of LSRUses between LSRFixups. 1311 typedef DenseMap<std::pair<const SCEV *, LSRUse::KindType>, 1312 size_t, 1313 UseMapDenseMapInfo> UseMapTy; 1314 UseMapTy UseMap; 1315 1316 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg, 1317 LSRUse::KindType Kind, const Type *AccessTy); 1318 1319 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, 1320 LSRUse::KindType Kind, 1321 const Type *AccessTy); 1322 1323 void DeleteUse(LSRUse &LU, size_t LUIdx); 1324 1325 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU); 1326 1327public: 1328 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); 1329 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); 1330 void CountRegisters(const Formula &F, size_t LUIdx); 1331 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F); 1332 1333 void CollectLoopInvariantFixupsAndFormulae(); 1334 1335 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base, 1336 unsigned Depth = 0); 1337 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base); 1338 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); 1339 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); 1340 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base); 1341 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base); 1342 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base); 1343 void GenerateCrossUseConstantOffsets(); 1344 void GenerateAllReuseFormulae(); 1345 1346 void FilterOutUndesirableDedicatedRegisters(); 1347 1348 size_t EstimateSearchSpaceComplexity() const; 1349 void NarrowSearchSpaceByDetectingSupersets(); 1350 void NarrowSearchSpaceByCollapsingUnrolledCode(); 1351 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(); 1352 void NarrowSearchSpaceByPickingWinnerRegs(); 1353 void NarrowSearchSpaceUsingHeuristics(); 1354 1355 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution, 1356 Cost &SolutionCost, 1357 SmallVectorImpl<const Formula *> &Workspace, 1358 const Cost &CurCost, 1359 const SmallPtrSet<const SCEV *, 16> &CurRegs, 1360 DenseSet<const SCEV *> &VisitedRegs) const; 1361 void Solve(SmallVectorImpl<const Formula *> &Solution) const; 1362 1363 BasicBlock::iterator 1364 HoistInsertPosition(BasicBlock::iterator IP, 1365 const SmallVectorImpl<Instruction *> &Inputs) const; 1366 BasicBlock::iterator AdjustInsertPositionForExpand(BasicBlock::iterator IP, 1367 const LSRFixup &LF, 1368 const LSRUse &LU) const; 1369 1370 Value *Expand(const LSRFixup &LF, 1371 const Formula &F, 1372 BasicBlock::iterator IP, 1373 SCEVExpander &Rewriter, 1374 SmallVectorImpl<WeakVH> &DeadInsts) const; 1375 void RewriteForPHI(PHINode *PN, const LSRFixup &LF, 1376 const Formula &F, 1377 SCEVExpander &Rewriter, 1378 SmallVectorImpl<WeakVH> &DeadInsts, 1379 Pass *P) const; 1380 void Rewrite(const LSRFixup &LF, 1381 const Formula &F, 1382 SCEVExpander &Rewriter, 1383 SmallVectorImpl<WeakVH> &DeadInsts, 1384 Pass *P) const; 1385 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution, 1386 Pass *P); 1387 1388 LSRInstance(const TargetLowering *tli, Loop *l, Pass *P); 1389 1390 bool getChanged() const { return Changed; } 1391 1392 void print_factors_and_types(raw_ostream &OS) const; 1393 void print_fixups(raw_ostream &OS) const; 1394 void print_uses(raw_ostream &OS) const; 1395 void print(raw_ostream &OS) const; 1396 void dump() const; 1397}; 1398 1399} 1400 1401/// OptimizeShadowIV - If IV is used in a int-to-float cast 1402/// inside the loop then try to eliminate the cast operation. 1403void LSRInstance::OptimizeShadowIV() { 1404 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); 1405 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) 1406 return; 1407 1408 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); 1409 UI != E; /* empty */) { 1410 IVUsers::const_iterator CandidateUI = UI; 1411 ++UI; 1412 Instruction *ShadowUse = CandidateUI->getUser(); 1413 const Type *DestTy = NULL; 1414 1415 /* If shadow use is a int->float cast then insert a second IV 1416 to eliminate this cast. 1417 1418 for (unsigned i = 0; i < n; ++i) 1419 foo((double)i); 1420 1421 is transformed into 1422 1423 double d = 0.0; 1424 for (unsigned i = 0; i < n; ++i, ++d) 1425 foo(d); 1426 */ 1427 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) 1428 DestTy = UCast->getDestTy(); 1429 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) 1430 DestTy = SCast->getDestTy(); 1431 if (!DestTy) continue; 1432 1433 if (TLI) { 1434 // If target does not support DestTy natively then do not apply 1435 // this transformation. 1436 EVT DVT = TLI->getValueType(DestTy); 1437 if (!TLI->isTypeLegal(DVT)) continue; 1438 } 1439 1440 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0)); 1441 if (!PH) continue; 1442 if (PH->getNumIncomingValues() != 2) continue; 1443 1444 const Type *SrcTy = PH->getType(); 1445 int Mantissa = DestTy->getFPMantissaWidth(); 1446 if (Mantissa == -1) continue; 1447 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa) 1448 continue; 1449 1450 unsigned Entry, Latch; 1451 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) { 1452 Entry = 0; 1453 Latch = 1; 1454 } else { 1455 Entry = 1; 1456 Latch = 0; 1457 } 1458 1459 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry)); 1460 if (!Init) continue; 1461 Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue()); 1462 1463 BinaryOperator *Incr = 1464 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch)); 1465 if (!Incr) continue; 1466 if (Incr->getOpcode() != Instruction::Add 1467 && Incr->getOpcode() != Instruction::Sub) 1468 continue; 1469 1470 /* Initialize new IV, double d = 0.0 in above example. */ 1471 ConstantInt *C = NULL; 1472 if (Incr->getOperand(0) == PH) 1473 C = dyn_cast<ConstantInt>(Incr->getOperand(1)); 1474 else if (Incr->getOperand(1) == PH) 1475 C = dyn_cast<ConstantInt>(Incr->getOperand(0)); 1476 else 1477 continue; 1478 1479 if (!C) continue; 1480 1481 // Ignore negative constants, as the code below doesn't handle them 1482 // correctly. TODO: Remove this restriction. 1483 if (!C->getValue().isStrictlyPositive()) continue; 1484 1485 /* Add new PHINode. */ 1486 PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH); 1487 1488 /* create new increment. '++d' in above example. */ 1489 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue()); 1490 BinaryOperator *NewIncr = 1491 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ? 1492 Instruction::FAdd : Instruction::FSub, 1493 NewPH, CFP, "IV.S.next.", Incr); 1494 1495 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry)); 1496 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch)); 1497 1498 /* Remove cast operation */ 1499 ShadowUse->replaceAllUsesWith(NewPH); 1500 ShadowUse->eraseFromParent(); 1501 Changed = true; 1502 break; 1503 } 1504} 1505 1506/// FindIVUserForCond - If Cond has an operand that is an expression of an IV, 1507/// set the IV user and stride information and return true, otherwise return 1508/// false. 1509bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) { 1510 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) 1511 if (UI->getUser() == Cond) { 1512 // NOTE: we could handle setcc instructions with multiple uses here, but 1513 // InstCombine does it as well for simple uses, it's not clear that it 1514 // occurs enough in real life to handle. 1515 CondUse = UI; 1516 return true; 1517 } 1518 return false; 1519} 1520 1521/// OptimizeMax - Rewrite the loop's terminating condition if it uses 1522/// a max computation. 1523/// 1524/// This is a narrow solution to a specific, but acute, problem. For loops 1525/// like this: 1526/// 1527/// i = 0; 1528/// do { 1529/// p[i] = 0.0; 1530/// } while (++i < n); 1531/// 1532/// the trip count isn't just 'n', because 'n' might not be positive. And 1533/// unfortunately this can come up even for loops where the user didn't use 1534/// a C do-while loop. For example, seemingly well-behaved top-test loops 1535/// will commonly be lowered like this: 1536// 1537/// if (n > 0) { 1538/// i = 0; 1539/// do { 1540/// p[i] = 0.0; 1541/// } while (++i < n); 1542/// } 1543/// 1544/// and then it's possible for subsequent optimization to obscure the if 1545/// test in such a way that indvars can't find it. 1546/// 1547/// When indvars can't find the if test in loops like this, it creates a 1548/// max expression, which allows it to give the loop a canonical 1549/// induction variable: 1550/// 1551/// i = 0; 1552/// max = n < 1 ? 1 : n; 1553/// do { 1554/// p[i] = 0.0; 1555/// } while (++i != max); 1556/// 1557/// Canonical induction variables are necessary because the loop passes 1558/// are designed around them. The most obvious example of this is the 1559/// LoopInfo analysis, which doesn't remember trip count values. It 1560/// expects to be able to rediscover the trip count each time it is 1561/// needed, and it does this using a simple analysis that only succeeds if 1562/// the loop has a canonical induction variable. 1563/// 1564/// However, when it comes time to generate code, the maximum operation 1565/// can be quite costly, especially if it's inside of an outer loop. 1566/// 1567/// This function solves this problem by detecting this type of loop and 1568/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting 1569/// the instructions for the maximum computation. 1570/// 1571ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) { 1572 // Check that the loop matches the pattern we're looking for. 1573 if (Cond->getPredicate() != CmpInst::ICMP_EQ && 1574 Cond->getPredicate() != CmpInst::ICMP_NE) 1575 return Cond; 1576 1577 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1)); 1578 if (!Sel || !Sel->hasOneUse()) return Cond; 1579 1580 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); 1581 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) 1582 return Cond; 1583 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1); 1584 1585 // Add one to the backedge-taken count to get the trip count. 1586 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount); 1587 if (IterationCount != SE.getSCEV(Sel)) return Cond; 1588 1589 // Check for a max calculation that matches the pattern. There's no check 1590 // for ICMP_ULE here because the comparison would be with zero, which 1591 // isn't interesting. 1592 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE; 1593 const SCEVNAryExpr *Max = 0; 1594 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) { 1595 Pred = ICmpInst::ICMP_SLE; 1596 Max = S; 1597 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) { 1598 Pred = ICmpInst::ICMP_SLT; 1599 Max = S; 1600 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) { 1601 Pred = ICmpInst::ICMP_ULT; 1602 Max = U; 1603 } else { 1604 // No match; bail. 1605 return Cond; 1606 } 1607 1608 // To handle a max with more than two operands, this optimization would 1609 // require additional checking and setup. 1610 if (Max->getNumOperands() != 2) 1611 return Cond; 1612 1613 const SCEV *MaxLHS = Max->getOperand(0); 1614 const SCEV *MaxRHS = Max->getOperand(1); 1615 1616 // ScalarEvolution canonicalizes constants to the left. For < and >, look 1617 // for a comparison with 1. For <= and >=, a comparison with zero. 1618 if (!MaxLHS || 1619 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One))) 1620 return Cond; 1621 1622 // Check the relevant induction variable for conformance to 1623 // the pattern. 1624 const SCEV *IV = SE.getSCEV(Cond->getOperand(0)); 1625 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV); 1626 if (!AR || !AR->isAffine() || 1627 AR->getStart() != One || 1628 AR->getStepRecurrence(SE) != One) 1629 return Cond; 1630 1631 assert(AR->getLoop() == L && 1632 "Loop condition operand is an addrec in a different loop!"); 1633 1634 // Check the right operand of the select, and remember it, as it will 1635 // be used in the new comparison instruction. 1636 Value *NewRHS = 0; 1637 if (ICmpInst::isTrueWhenEqual(Pred)) { 1638 // Look for n+1, and grab n. 1639 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1))) 1640 if (isa<ConstantInt>(BO->getOperand(1)) && 1641 cast<ConstantInt>(BO->getOperand(1))->isOne() && 1642 SE.getSCEV(BO->getOperand(0)) == MaxRHS) 1643 NewRHS = BO->getOperand(0); 1644 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2))) 1645 if (isa<ConstantInt>(BO->getOperand(1)) && 1646 cast<ConstantInt>(BO->getOperand(1))->isOne() && 1647 SE.getSCEV(BO->getOperand(0)) == MaxRHS) 1648 NewRHS = BO->getOperand(0); 1649 if (!NewRHS) 1650 return Cond; 1651 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS) 1652 NewRHS = Sel->getOperand(1); 1653 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS) 1654 NewRHS = Sel->getOperand(2); 1655 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS)) 1656 NewRHS = SU->getValue(); 1657 else 1658 // Max doesn't match expected pattern. 1659 return Cond; 1660 1661 // Determine the new comparison opcode. It may be signed or unsigned, 1662 // and the original comparison may be either equality or inequality. 1663 if (Cond->getPredicate() == CmpInst::ICMP_EQ) 1664 Pred = CmpInst::getInversePredicate(Pred); 1665 1666 // Ok, everything looks ok to change the condition into an SLT or SGE and 1667 // delete the max calculation. 1668 ICmpInst *NewCond = 1669 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp"); 1670 1671 // Delete the max calculation instructions. 1672 Cond->replaceAllUsesWith(NewCond); 1673 CondUse->setUser(NewCond); 1674 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0)); 1675 Cond->eraseFromParent(); 1676 Sel->eraseFromParent(); 1677 if (Cmp->use_empty()) 1678 Cmp->eraseFromParent(); 1679 return NewCond; 1680} 1681 1682/// OptimizeLoopTermCond - Change loop terminating condition to use the 1683/// postinc iv when possible. 1684void 1685LSRInstance::OptimizeLoopTermCond() { 1686 SmallPtrSet<Instruction *, 4> PostIncs; 1687 1688 BasicBlock *LatchBlock = L->getLoopLatch(); 1689 SmallVector<BasicBlock*, 8> ExitingBlocks; 1690 L->getExitingBlocks(ExitingBlocks); 1691 1692 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) { 1693 BasicBlock *ExitingBlock = ExitingBlocks[i]; 1694 1695 // Get the terminating condition for the loop if possible. If we 1696 // can, we want to change it to use a post-incremented version of its 1697 // induction variable, to allow coalescing the live ranges for the IV into 1698 // one register value. 1699 1700 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator()); 1701 if (!TermBr) 1702 continue; 1703 // FIXME: Overly conservative, termination condition could be an 'or' etc.. 1704 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition())) 1705 continue; 1706 1707 // Search IVUsesByStride to find Cond's IVUse if there is one. 1708 IVStrideUse *CondUse = 0; 1709 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition()); 1710 if (!FindIVUserForCond(Cond, CondUse)) 1711 continue; 1712 1713 // If the trip count is computed in terms of a max (due to ScalarEvolution 1714 // being unable to find a sufficient guard, for example), change the loop 1715 // comparison to use SLT or ULT instead of NE. 1716 // One consequence of doing this now is that it disrupts the count-down 1717 // optimization. That's not always a bad thing though, because in such 1718 // cases it may still be worthwhile to avoid a max. 1719 Cond = OptimizeMax(Cond, CondUse); 1720 1721 // If this exiting block dominates the latch block, it may also use 1722 // the post-inc value if it won't be shared with other uses. 1723 // Check for dominance. 1724 if (!DT.dominates(ExitingBlock, LatchBlock)) 1725 continue; 1726 1727 // Conservatively avoid trying to use the post-inc value in non-latch 1728 // exits if there may be pre-inc users in intervening blocks. 1729 if (LatchBlock != ExitingBlock) 1730 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) 1731 // Test if the use is reachable from the exiting block. This dominator 1732 // query is a conservative approximation of reachability. 1733 if (&*UI != CondUse && 1734 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) { 1735 // Conservatively assume there may be reuse if the quotient of their 1736 // strides could be a legal scale. 1737 const SCEV *A = IU.getStride(*CondUse, L); 1738 const SCEV *B = IU.getStride(*UI, L); 1739 if (!A || !B) continue; 1740 if (SE.getTypeSizeInBits(A->getType()) != 1741 SE.getTypeSizeInBits(B->getType())) { 1742 if (SE.getTypeSizeInBits(A->getType()) > 1743 SE.getTypeSizeInBits(B->getType())) 1744 B = SE.getSignExtendExpr(B, A->getType()); 1745 else 1746 A = SE.getSignExtendExpr(A, B->getType()); 1747 } 1748 if (const SCEVConstant *D = 1749 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) { 1750 const ConstantInt *C = D->getValue(); 1751 // Stride of one or negative one can have reuse with non-addresses. 1752 if (C->isOne() || C->isAllOnesValue()) 1753 goto decline_post_inc; 1754 // Avoid weird situations. 1755 if (C->getValue().getMinSignedBits() >= 64 || 1756 C->getValue().isMinSignedValue()) 1757 goto decline_post_inc; 1758 // Without TLI, assume that any stride might be valid, and so any 1759 // use might be shared. 1760 if (!TLI) 1761 goto decline_post_inc; 1762 // Check for possible scaled-address reuse. 1763 const Type *AccessTy = getAccessType(UI->getUser()); 1764 TargetLowering::AddrMode AM; 1765 AM.Scale = C->getSExtValue(); 1766 if (TLI->isLegalAddressingMode(AM, AccessTy)) 1767 goto decline_post_inc; 1768 AM.Scale = -AM.Scale; 1769 if (TLI->isLegalAddressingMode(AM, AccessTy)) 1770 goto decline_post_inc; 1771 } 1772 } 1773 1774 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: " 1775 << *Cond << '\n'); 1776 1777 // It's possible for the setcc instruction to be anywhere in the loop, and 1778 // possible for it to have multiple users. If it is not immediately before 1779 // the exiting block branch, move it. 1780 if (&*++BasicBlock::iterator(Cond) != TermBr) { 1781 if (Cond->hasOneUse()) { 1782 Cond->moveBefore(TermBr); 1783 } else { 1784 // Clone the terminating condition and insert into the loopend. 1785 ICmpInst *OldCond = Cond; 1786 Cond = cast<ICmpInst>(Cond->clone()); 1787 Cond->setName(L->getHeader()->getName() + ".termcond"); 1788 ExitingBlock->getInstList().insert(TermBr, Cond); 1789 1790 // Clone the IVUse, as the old use still exists! 1791 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace()); 1792 TermBr->replaceUsesOfWith(OldCond, Cond); 1793 } 1794 } 1795 1796 // If we get to here, we know that we can transform the setcc instruction to 1797 // use the post-incremented version of the IV, allowing us to coalesce the 1798 // live ranges for the IV correctly. 1799 CondUse->transformToPostInc(L); 1800 Changed = true; 1801 1802 PostIncs.insert(Cond); 1803 decline_post_inc:; 1804 } 1805 1806 // Determine an insertion point for the loop induction variable increment. It 1807 // must dominate all the post-inc comparisons we just set up, and it must 1808 // dominate the loop latch edge. 1809 IVIncInsertPos = L->getLoopLatch()->getTerminator(); 1810 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(), 1811 E = PostIncs.end(); I != E; ++I) { 1812 BasicBlock *BB = 1813 DT.findNearestCommonDominator(IVIncInsertPos->getParent(), 1814 (*I)->getParent()); 1815 if (BB == (*I)->getParent()) 1816 IVIncInsertPos = *I; 1817 else if (BB != IVIncInsertPos->getParent()) 1818 IVIncInsertPos = BB->getTerminator(); 1819 } 1820} 1821 1822/// reconcileNewOffset - Determine if the given use can accomodate a fixup 1823/// at the given offset and other details. If so, update the use and 1824/// return true. 1825bool 1826LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg, 1827 LSRUse::KindType Kind, const Type *AccessTy) { 1828 int64_t NewMinOffset = LU.MinOffset; 1829 int64_t NewMaxOffset = LU.MaxOffset; 1830 const Type *NewAccessTy = AccessTy; 1831 1832 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to 1833 // something conservative, however this can pessimize in the case that one of 1834 // the uses will have all its uses outside the loop, for example. 1835 if (LU.Kind != Kind) 1836 return false; 1837 // Conservatively assume HasBaseReg is true for now. 1838 if (NewOffset < LU.MinOffset) { 1839 if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg, 1840 Kind, AccessTy, TLI)) 1841 return false; 1842 NewMinOffset = NewOffset; 1843 } else if (NewOffset > LU.MaxOffset) { 1844 if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg, 1845 Kind, AccessTy, TLI)) 1846 return false; 1847 NewMaxOffset = NewOffset; 1848 } 1849 // Check for a mismatched access type, and fall back conservatively as needed. 1850 // TODO: Be less conservative when the type is similar and can use the same 1851 // addressing modes. 1852 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy) 1853 NewAccessTy = Type::getVoidTy(AccessTy->getContext()); 1854 1855 // Update the use. 1856 LU.MinOffset = NewMinOffset; 1857 LU.MaxOffset = NewMaxOffset; 1858 LU.AccessTy = NewAccessTy; 1859 if (NewOffset != LU.Offsets.back()) 1860 LU.Offsets.push_back(NewOffset); 1861 return true; 1862} 1863 1864/// getUse - Return an LSRUse index and an offset value for a fixup which 1865/// needs the given expression, with the given kind and optional access type. 1866/// Either reuse an existing use or create a new one, as needed. 1867std::pair<size_t, int64_t> 1868LSRInstance::getUse(const SCEV *&Expr, 1869 LSRUse::KindType Kind, const Type *AccessTy) { 1870 const SCEV *Copy = Expr; 1871 int64_t Offset = ExtractImmediate(Expr, SE); 1872 1873 // Basic uses can't accept any offset, for example. 1874 if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) { 1875 Expr = Copy; 1876 Offset = 0; 1877 } 1878 1879 std::pair<UseMapTy::iterator, bool> P = 1880 UseMap.insert(std::make_pair(std::make_pair(Expr, Kind), 0)); 1881 if (!P.second) { 1882 // A use already existed with this base. 1883 size_t LUIdx = P.first->second; 1884 LSRUse &LU = Uses[LUIdx]; 1885 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy)) 1886 // Reuse this use. 1887 return std::make_pair(LUIdx, Offset); 1888 } 1889 1890 // Create a new use. 1891 size_t LUIdx = Uses.size(); 1892 P.first->second = LUIdx; 1893 Uses.push_back(LSRUse(Kind, AccessTy)); 1894 LSRUse &LU = Uses[LUIdx]; 1895 1896 // We don't need to track redundant offsets, but we don't need to go out 1897 // of our way here to avoid them. 1898 if (LU.Offsets.empty() || Offset != LU.Offsets.back()) 1899 LU.Offsets.push_back(Offset); 1900 1901 LU.MinOffset = Offset; 1902 LU.MaxOffset = Offset; 1903 return std::make_pair(LUIdx, Offset); 1904} 1905 1906/// DeleteUse - Delete the given use from the Uses list. 1907void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) { 1908 if (&LU != &Uses.back()) 1909 std::swap(LU, Uses.back()); 1910 Uses.pop_back(); 1911 1912 // Update RegUses. 1913 RegUses.SwapAndDropUse(LUIdx, Uses.size()); 1914} 1915 1916/// FindUseWithFormula - Look for a use distinct from OrigLU which is has 1917/// a formula that has the same registers as the given formula. 1918LSRUse * 1919LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF, 1920 const LSRUse &OrigLU) { 1921 // Search all uses for the formula. This could be more clever. 1922 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 1923 LSRUse &LU = Uses[LUIdx]; 1924 // Check whether this use is close enough to OrigLU, to see whether it's 1925 // worthwhile looking through its formulae. 1926 // Ignore ICmpZero uses because they may contain formulae generated by 1927 // GenerateICmpZeroScales, in which case adding fixup offsets may 1928 // be invalid. 1929 if (&LU != &OrigLU && 1930 LU.Kind != LSRUse::ICmpZero && 1931 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy && 1932 LU.WidestFixupType == OrigLU.WidestFixupType && 1933 LU.HasFormulaWithSameRegs(OrigF)) { 1934 // Scan through this use's formulae. 1935 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), 1936 E = LU.Formulae.end(); I != E; ++I) { 1937 const Formula &F = *I; 1938 // Check to see if this formula has the same registers and symbols 1939 // as OrigF. 1940 if (F.BaseRegs == OrigF.BaseRegs && 1941 F.ScaledReg == OrigF.ScaledReg && 1942 F.AM.BaseGV == OrigF.AM.BaseGV && 1943 F.AM.Scale == OrigF.AM.Scale) { 1944 if (F.AM.BaseOffs == 0) 1945 return &LU; 1946 // This is the formula where all the registers and symbols matched; 1947 // there aren't going to be any others. Since we declined it, we 1948 // can skip the rest of the formulae and procede to the next LSRUse. 1949 break; 1950 } 1951 } 1952 } 1953 } 1954 1955 // Nothing looked good. 1956 return 0; 1957} 1958 1959void LSRInstance::CollectInterestingTypesAndFactors() { 1960 SmallSetVector<const SCEV *, 4> Strides; 1961 1962 // Collect interesting types and strides. 1963 SmallVector<const SCEV *, 4> Worklist; 1964 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { 1965 const SCEV *Expr = IU.getExpr(*UI); 1966 1967 // Collect interesting types. 1968 Types.insert(SE.getEffectiveSCEVType(Expr->getType())); 1969 1970 // Add strides for mentioned loops. 1971 Worklist.push_back(Expr); 1972 do { 1973 const SCEV *S = Worklist.pop_back_val(); 1974 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 1975 Strides.insert(AR->getStepRecurrence(SE)); 1976 Worklist.push_back(AR->getStart()); 1977 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 1978 Worklist.append(Add->op_begin(), Add->op_end()); 1979 } 1980 } while (!Worklist.empty()); 1981 } 1982 1983 // Compute interesting factors from the set of interesting strides. 1984 for (SmallSetVector<const SCEV *, 4>::const_iterator 1985 I = Strides.begin(), E = Strides.end(); I != E; ++I) 1986 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter = 1987 llvm::next(I); NewStrideIter != E; ++NewStrideIter) { 1988 const SCEV *OldStride = *I; 1989 const SCEV *NewStride = *NewStrideIter; 1990 1991 if (SE.getTypeSizeInBits(OldStride->getType()) != 1992 SE.getTypeSizeInBits(NewStride->getType())) { 1993 if (SE.getTypeSizeInBits(OldStride->getType()) > 1994 SE.getTypeSizeInBits(NewStride->getType())) 1995 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType()); 1996 else 1997 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType()); 1998 } 1999 if (const SCEVConstant *Factor = 2000 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride, 2001 SE, true))) { 2002 if (Factor->getValue()->getValue().getMinSignedBits() <= 64) 2003 Factors.insert(Factor->getValue()->getValue().getSExtValue()); 2004 } else if (const SCEVConstant *Factor = 2005 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride, 2006 NewStride, 2007 SE, true))) { 2008 if (Factor->getValue()->getValue().getMinSignedBits() <= 64) 2009 Factors.insert(Factor->getValue()->getValue().getSExtValue()); 2010 } 2011 } 2012 2013 // If all uses use the same type, don't bother looking for truncation-based 2014 // reuse. 2015 if (Types.size() == 1) 2016 Types.clear(); 2017 2018 DEBUG(print_factors_and_types(dbgs())); 2019} 2020 2021void LSRInstance::CollectFixupsAndInitialFormulae() { 2022 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { 2023 // Record the uses. 2024 LSRFixup &LF = getNewFixup(); 2025 LF.UserInst = UI->getUser(); 2026 LF.OperandValToReplace = UI->getOperandValToReplace(); 2027 LF.PostIncLoops = UI->getPostIncLoops(); 2028 2029 LSRUse::KindType Kind = LSRUse::Basic; 2030 const Type *AccessTy = 0; 2031 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) { 2032 Kind = LSRUse::Address; 2033 AccessTy = getAccessType(LF.UserInst); 2034 } 2035 2036 const SCEV *S = IU.getExpr(*UI); 2037 2038 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as 2039 // (N - i == 0), and this allows (N - i) to be the expression that we work 2040 // with rather than just N or i, so we can consider the register 2041 // requirements for both N and i at the same time. Limiting this code to 2042 // equality icmps is not a problem because all interesting loops use 2043 // equality icmps, thanks to IndVarSimplify. 2044 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst)) 2045 if (CI->isEquality()) { 2046 // Swap the operands if needed to put the OperandValToReplace on the 2047 // left, for consistency. 2048 Value *NV = CI->getOperand(1); 2049 if (NV == LF.OperandValToReplace) { 2050 CI->setOperand(1, CI->getOperand(0)); 2051 CI->setOperand(0, NV); 2052 NV = CI->getOperand(1); 2053 Changed = true; 2054 } 2055 2056 // x == y --> x - y == 0 2057 const SCEV *N = SE.getSCEV(NV); 2058 if (SE.isLoopInvariant(N, L)) { 2059 Kind = LSRUse::ICmpZero; 2060 S = SE.getMinusSCEV(N, S); 2061 } 2062 2063 // -1 and the negations of all interesting strides (except the negation 2064 // of -1) are now also interesting. 2065 for (size_t i = 0, e = Factors.size(); i != e; ++i) 2066 if (Factors[i] != -1) 2067 Factors.insert(-(uint64_t)Factors[i]); 2068 Factors.insert(-1); 2069 } 2070 2071 // Set up the initial formula for this use. 2072 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy); 2073 LF.LUIdx = P.first; 2074 LF.Offset = P.second; 2075 LSRUse &LU = Uses[LF.LUIdx]; 2076 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L); 2077 if (!LU.WidestFixupType || 2078 SE.getTypeSizeInBits(LU.WidestFixupType) < 2079 SE.getTypeSizeInBits(LF.OperandValToReplace->getType())) 2080 LU.WidestFixupType = LF.OperandValToReplace->getType(); 2081 2082 // If this is the first use of this LSRUse, give it a formula. 2083 if (LU.Formulae.empty()) { 2084 InsertInitialFormula(S, LU, LF.LUIdx); 2085 CountRegisters(LU.Formulae.back(), LF.LUIdx); 2086 } 2087 } 2088 2089 DEBUG(print_fixups(dbgs())); 2090} 2091 2092/// InsertInitialFormula - Insert a formula for the given expression into 2093/// the given use, separating out loop-variant portions from loop-invariant 2094/// and loop-computable portions. 2095void 2096LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) { 2097 Formula F; 2098 F.InitialMatch(S, L, SE); 2099 bool Inserted = InsertFormula(LU, LUIdx, F); 2100 assert(Inserted && "Initial formula already exists!"); (void)Inserted; 2101} 2102 2103/// InsertSupplementalFormula - Insert a simple single-register formula for 2104/// the given expression into the given use. 2105void 2106LSRInstance::InsertSupplementalFormula(const SCEV *S, 2107 LSRUse &LU, size_t LUIdx) { 2108 Formula F; 2109 F.BaseRegs.push_back(S); 2110 F.AM.HasBaseReg = true; 2111 bool Inserted = InsertFormula(LU, LUIdx, F); 2112 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted; 2113} 2114 2115/// CountRegisters - Note which registers are used by the given formula, 2116/// updating RegUses. 2117void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) { 2118 if (F.ScaledReg) 2119 RegUses.CountRegister(F.ScaledReg, LUIdx); 2120 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), 2121 E = F.BaseRegs.end(); I != E; ++I) 2122 RegUses.CountRegister(*I, LUIdx); 2123} 2124 2125/// InsertFormula - If the given formula has not yet been inserted, add it to 2126/// the list, and return true. Return false otherwise. 2127bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) { 2128 if (!LU.InsertFormula(F)) 2129 return false; 2130 2131 CountRegisters(F, LUIdx); 2132 return true; 2133} 2134 2135/// CollectLoopInvariantFixupsAndFormulae - Check for other uses of 2136/// loop-invariant values which we're tracking. These other uses will pin these 2137/// values in registers, making them less profitable for elimination. 2138/// TODO: This currently misses non-constant addrec step registers. 2139/// TODO: Should this give more weight to users inside the loop? 2140void 2141LSRInstance::CollectLoopInvariantFixupsAndFormulae() { 2142 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end()); 2143 SmallPtrSet<const SCEV *, 8> Inserted; 2144 2145 while (!Worklist.empty()) { 2146 const SCEV *S = Worklist.pop_back_val(); 2147 2148 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) 2149 Worklist.append(N->op_begin(), N->op_end()); 2150 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S)) 2151 Worklist.push_back(C->getOperand()); 2152 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) { 2153 Worklist.push_back(D->getLHS()); 2154 Worklist.push_back(D->getRHS()); 2155 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { 2156 if (!Inserted.insert(U)) continue; 2157 const Value *V = U->getValue(); 2158 if (const Instruction *Inst = dyn_cast<Instruction>(V)) { 2159 // Look for instructions defined outside the loop. 2160 if (L->contains(Inst)) continue; 2161 } else if (isa<UndefValue>(V)) 2162 // Undef doesn't have a live range, so it doesn't matter. 2163 continue; 2164 for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end(); 2165 UI != UE; ++UI) { 2166 const Instruction *UserInst = dyn_cast<Instruction>(*UI); 2167 // Ignore non-instructions. 2168 if (!UserInst) 2169 continue; 2170 // Ignore instructions in other functions (as can happen with 2171 // Constants). 2172 if (UserInst->getParent()->getParent() != L->getHeader()->getParent()) 2173 continue; 2174 // Ignore instructions not dominated by the loop. 2175 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ? 2176 UserInst->getParent() : 2177 cast<PHINode>(UserInst)->getIncomingBlock( 2178 PHINode::getIncomingValueNumForOperand(UI.getOperandNo())); 2179 if (!DT.dominates(L->getHeader(), UseBB)) 2180 continue; 2181 // Ignore uses which are part of other SCEV expressions, to avoid 2182 // analyzing them multiple times. 2183 if (SE.isSCEVable(UserInst->getType())) { 2184 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst)); 2185 // If the user is a no-op, look through to its uses. 2186 if (!isa<SCEVUnknown>(UserS)) 2187 continue; 2188 if (UserS == U) { 2189 Worklist.push_back( 2190 SE.getUnknown(const_cast<Instruction *>(UserInst))); 2191 continue; 2192 } 2193 } 2194 // Ignore icmp instructions which are already being analyzed. 2195 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) { 2196 unsigned OtherIdx = !UI.getOperandNo(); 2197 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx)); 2198 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L)) 2199 continue; 2200 } 2201 2202 LSRFixup &LF = getNewFixup(); 2203 LF.UserInst = const_cast<Instruction *>(UserInst); 2204 LF.OperandValToReplace = UI.getUse(); 2205 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0); 2206 LF.LUIdx = P.first; 2207 LF.Offset = P.second; 2208 LSRUse &LU = Uses[LF.LUIdx]; 2209 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L); 2210 if (!LU.WidestFixupType || 2211 SE.getTypeSizeInBits(LU.WidestFixupType) < 2212 SE.getTypeSizeInBits(LF.OperandValToReplace->getType())) 2213 LU.WidestFixupType = LF.OperandValToReplace->getType(); 2214 InsertSupplementalFormula(U, LU, LF.LUIdx); 2215 CountRegisters(LU.Formulae.back(), Uses.size() - 1); 2216 break; 2217 } 2218 } 2219 } 2220} 2221 2222/// CollectSubexprs - Split S into subexpressions which can be pulled out into 2223/// separate registers. If C is non-null, multiply each subexpression by C. 2224static void CollectSubexprs(const SCEV *S, const SCEVConstant *C, 2225 SmallVectorImpl<const SCEV *> &Ops, 2226 const Loop *L, 2227 ScalarEvolution &SE) { 2228 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 2229 // Break out add operands. 2230 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 2231 I != E; ++I) 2232 CollectSubexprs(*I, C, Ops, L, SE); 2233 return; 2234 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 2235 // Split a non-zero base out of an addrec. 2236 if (!AR->getStart()->isZero()) { 2237 CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0), 2238 AR->getStepRecurrence(SE), 2239 AR->getLoop()), 2240 C, Ops, L, SE); 2241 CollectSubexprs(AR->getStart(), C, Ops, L, SE); 2242 return; 2243 } 2244 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) { 2245 // Break (C * (a + b + c)) into C*a + C*b + C*c. 2246 if (Mul->getNumOperands() == 2) 2247 if (const SCEVConstant *Op0 = 2248 dyn_cast<SCEVConstant>(Mul->getOperand(0))) { 2249 CollectSubexprs(Mul->getOperand(1), 2250 C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0, 2251 Ops, L, SE); 2252 return; 2253 } 2254 } 2255 2256 // Otherwise use the value itself, optionally with a scale applied. 2257 Ops.push_back(C ? SE.getMulExpr(C, S) : S); 2258} 2259 2260/// GenerateReassociations - Split out subexpressions from adds and the bases of 2261/// addrecs. 2262void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx, 2263 Formula Base, 2264 unsigned Depth) { 2265 // Arbitrarily cap recursion to protect compile time. 2266 if (Depth >= 3) return; 2267 2268 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { 2269 const SCEV *BaseReg = Base.BaseRegs[i]; 2270 2271 SmallVector<const SCEV *, 8> AddOps; 2272 CollectSubexprs(BaseReg, 0, AddOps, L, SE); 2273 2274 if (AddOps.size() == 1) continue; 2275 2276 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(), 2277 JE = AddOps.end(); J != JE; ++J) { 2278 2279 // Loop-variant "unknown" values are uninteresting; we won't be able to 2280 // do anything meaningful with them. 2281 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L)) 2282 continue; 2283 2284 // Don't pull a constant into a register if the constant could be folded 2285 // into an immediate field. 2286 if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset, 2287 Base.getNumRegs() > 1, 2288 LU.Kind, LU.AccessTy, TLI, SE)) 2289 continue; 2290 2291 // Collect all operands except *J. 2292 SmallVector<const SCEV *, 8> InnerAddOps 2293 (((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J); 2294 InnerAddOps.append 2295 (llvm::next(J), ((const SmallVector<const SCEV *, 8> &)AddOps).end()); 2296 2297 // Don't leave just a constant behind in a register if the constant could 2298 // be folded into an immediate field. 2299 if (InnerAddOps.size() == 1 && 2300 isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset, 2301 Base.getNumRegs() > 1, 2302 LU.Kind, LU.AccessTy, TLI, SE)) 2303 continue; 2304 2305 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps); 2306 if (InnerSum->isZero()) 2307 continue; 2308 Formula F = Base; 2309 F.BaseRegs[i] = InnerSum; 2310 F.BaseRegs.push_back(*J); 2311 if (InsertFormula(LU, LUIdx, F)) 2312 // If that formula hadn't been seen before, recurse to find more like 2313 // it. 2314 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1); 2315 } 2316 } 2317} 2318 2319/// GenerateCombinations - Generate a formula consisting of all of the 2320/// loop-dominating registers added into a single register. 2321void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx, 2322 Formula Base) { 2323 // This method is only interesting on a plurality of registers. 2324 if (Base.BaseRegs.size() <= 1) return; 2325 2326 Formula F = Base; 2327 F.BaseRegs.clear(); 2328 SmallVector<const SCEV *, 4> Ops; 2329 for (SmallVectorImpl<const SCEV *>::const_iterator 2330 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) { 2331 const SCEV *BaseReg = *I; 2332 if (SE.properlyDominates(BaseReg, L->getHeader()) && 2333 !SE.hasComputableLoopEvolution(BaseReg, L)) 2334 Ops.push_back(BaseReg); 2335 else 2336 F.BaseRegs.push_back(BaseReg); 2337 } 2338 if (Ops.size() > 1) { 2339 const SCEV *Sum = SE.getAddExpr(Ops); 2340 // TODO: If Sum is zero, it probably means ScalarEvolution missed an 2341 // opportunity to fold something. For now, just ignore such cases 2342 // rather than proceed with zero in a register. 2343 if (!Sum->isZero()) { 2344 F.BaseRegs.push_back(Sum); 2345 (void)InsertFormula(LU, LUIdx, F); 2346 } 2347 } 2348} 2349 2350/// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets. 2351void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, 2352 Formula Base) { 2353 // We can't add a symbolic offset if the address already contains one. 2354 if (Base.AM.BaseGV) return; 2355 2356 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { 2357 const SCEV *G = Base.BaseRegs[i]; 2358 GlobalValue *GV = ExtractSymbol(G, SE); 2359 if (G->isZero() || !GV) 2360 continue; 2361 Formula F = Base; 2362 F.AM.BaseGV = GV; 2363 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset, 2364 LU.Kind, LU.AccessTy, TLI)) 2365 continue; 2366 F.BaseRegs[i] = G; 2367 (void)InsertFormula(LU, LUIdx, F); 2368 } 2369} 2370 2371/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets. 2372void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, 2373 Formula Base) { 2374 // TODO: For now, just add the min and max offset, because it usually isn't 2375 // worthwhile looking at everything inbetween. 2376 SmallVector<int64_t, 2> Worklist; 2377 Worklist.push_back(LU.MinOffset); 2378 if (LU.MaxOffset != LU.MinOffset) 2379 Worklist.push_back(LU.MaxOffset); 2380 2381 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { 2382 const SCEV *G = Base.BaseRegs[i]; 2383 2384 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(), 2385 E = Worklist.end(); I != E; ++I) { 2386 Formula F = Base; 2387 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I; 2388 if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I, 2389 LU.Kind, LU.AccessTy, TLI)) { 2390 // Add the offset to the base register. 2391 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G); 2392 // If it cancelled out, drop the base register, otherwise update it. 2393 if (NewG->isZero()) { 2394 std::swap(F.BaseRegs[i], F.BaseRegs.back()); 2395 F.BaseRegs.pop_back(); 2396 } else 2397 F.BaseRegs[i] = NewG; 2398 2399 (void)InsertFormula(LU, LUIdx, F); 2400 } 2401 } 2402 2403 int64_t Imm = ExtractImmediate(G, SE); 2404 if (G->isZero() || Imm == 0) 2405 continue; 2406 Formula F = Base; 2407 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm; 2408 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset, 2409 LU.Kind, LU.AccessTy, TLI)) 2410 continue; 2411 F.BaseRegs[i] = G; 2412 (void)InsertFormula(LU, LUIdx, F); 2413 } 2414} 2415 2416/// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up 2417/// the comparison. For example, x == y -> x*c == y*c. 2418void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, 2419 Formula Base) { 2420 if (LU.Kind != LSRUse::ICmpZero) return; 2421 2422 // Determine the integer type for the base formula. 2423 const Type *IntTy = Base.getType(); 2424 if (!IntTy) return; 2425 if (SE.getTypeSizeInBits(IntTy) > 64) return; 2426 2427 // Don't do this if there is more than one offset. 2428 if (LU.MinOffset != LU.MaxOffset) return; 2429 2430 assert(!Base.AM.BaseGV && "ICmpZero use is not legal!"); 2431 2432 // Check each interesting stride. 2433 for (SmallSetVector<int64_t, 8>::const_iterator 2434 I = Factors.begin(), E = Factors.end(); I != E; ++I) { 2435 int64_t Factor = *I; 2436 2437 // Check that the multiplication doesn't overflow. 2438 if (Base.AM.BaseOffs == INT64_MIN && Factor == -1) 2439 continue; 2440 int64_t NewBaseOffs = (uint64_t)Base.AM.BaseOffs * Factor; 2441 if (NewBaseOffs / Factor != Base.AM.BaseOffs) 2442 continue; 2443 2444 // Check that multiplying with the use offset doesn't overflow. 2445 int64_t Offset = LU.MinOffset; 2446 if (Offset == INT64_MIN && Factor == -1) 2447 continue; 2448 Offset = (uint64_t)Offset * Factor; 2449 if (Offset / Factor != LU.MinOffset) 2450 continue; 2451 2452 Formula F = Base; 2453 F.AM.BaseOffs = NewBaseOffs; 2454 2455 // Check that this scale is legal. 2456 if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI)) 2457 continue; 2458 2459 // Compensate for the use having MinOffset built into it. 2460 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset; 2461 2462 const SCEV *FactorS = SE.getConstant(IntTy, Factor); 2463 2464 // Check that multiplying with each base register doesn't overflow. 2465 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) { 2466 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS); 2467 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i]) 2468 goto next; 2469 } 2470 2471 // Check that multiplying with the scaled register doesn't overflow. 2472 if (F.ScaledReg) { 2473 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS); 2474 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg) 2475 continue; 2476 } 2477 2478 // If we make it here and it's legal, add it. 2479 (void)InsertFormula(LU, LUIdx, F); 2480 next:; 2481 } 2482} 2483 2484/// GenerateScales - Generate stride factor reuse formulae by making use of 2485/// scaled-offset address modes, for example. 2486void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) { 2487 // Determine the integer type for the base formula. 2488 const Type *IntTy = Base.getType(); 2489 if (!IntTy) return; 2490 2491 // If this Formula already has a scaled register, we can't add another one. 2492 if (Base.AM.Scale != 0) return; 2493 2494 // Check each interesting stride. 2495 for (SmallSetVector<int64_t, 8>::const_iterator 2496 I = Factors.begin(), E = Factors.end(); I != E; ++I) { 2497 int64_t Factor = *I; 2498 2499 Base.AM.Scale = Factor; 2500 Base.AM.HasBaseReg = Base.BaseRegs.size() > 1; 2501 // Check whether this scale is going to be legal. 2502 if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset, 2503 LU.Kind, LU.AccessTy, TLI)) { 2504 // As a special-case, handle special out-of-loop Basic users specially. 2505 // TODO: Reconsider this special case. 2506 if (LU.Kind == LSRUse::Basic && 2507 isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset, 2508 LSRUse::Special, LU.AccessTy, TLI) && 2509 LU.AllFixupsOutsideLoop) 2510 LU.Kind = LSRUse::Special; 2511 else 2512 continue; 2513 } 2514 // For an ICmpZero, negating a solitary base register won't lead to 2515 // new solutions. 2516 if (LU.Kind == LSRUse::ICmpZero && 2517 !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV) 2518 continue; 2519 // For each addrec base reg, apply the scale, if possible. 2520 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) 2521 if (const SCEVAddRecExpr *AR = 2522 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) { 2523 const SCEV *FactorS = SE.getConstant(IntTy, Factor); 2524 if (FactorS->isZero()) 2525 continue; 2526 // Divide out the factor, ignoring high bits, since we'll be 2527 // scaling the value back up in the end. 2528 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) { 2529 // TODO: This could be optimized to avoid all the copying. 2530 Formula F = Base; 2531 F.ScaledReg = Quotient; 2532 F.DeleteBaseReg(F.BaseRegs[i]); 2533 (void)InsertFormula(LU, LUIdx, F); 2534 } 2535 } 2536 } 2537} 2538 2539/// GenerateTruncates - Generate reuse formulae from different IV types. 2540void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) { 2541 // This requires TargetLowering to tell us which truncates are free. 2542 if (!TLI) return; 2543 2544 // Don't bother truncating symbolic values. 2545 if (Base.AM.BaseGV) return; 2546 2547 // Determine the integer type for the base formula. 2548 const Type *DstTy = Base.getType(); 2549 if (!DstTy) return; 2550 DstTy = SE.getEffectiveSCEVType(DstTy); 2551 2552 for (SmallSetVector<const Type *, 4>::const_iterator 2553 I = Types.begin(), E = Types.end(); I != E; ++I) { 2554 const Type *SrcTy = *I; 2555 if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) { 2556 Formula F = Base; 2557 2558 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I); 2559 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(), 2560 JE = F.BaseRegs.end(); J != JE; ++J) 2561 *J = SE.getAnyExtendExpr(*J, SrcTy); 2562 2563 // TODO: This assumes we've done basic processing on all uses and 2564 // have an idea what the register usage is. 2565 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses)) 2566 continue; 2567 2568 (void)InsertFormula(LU, LUIdx, F); 2569 } 2570 } 2571} 2572 2573namespace { 2574 2575/// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to 2576/// defer modifications so that the search phase doesn't have to worry about 2577/// the data structures moving underneath it. 2578struct WorkItem { 2579 size_t LUIdx; 2580 int64_t Imm; 2581 const SCEV *OrigReg; 2582 2583 WorkItem(size_t LI, int64_t I, const SCEV *R) 2584 : LUIdx(LI), Imm(I), OrigReg(R) {} 2585 2586 void print(raw_ostream &OS) const; 2587 void dump() const; 2588}; 2589 2590} 2591 2592void WorkItem::print(raw_ostream &OS) const { 2593 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx 2594 << " , add offset " << Imm; 2595} 2596 2597void WorkItem::dump() const { 2598 print(errs()); errs() << '\n'; 2599} 2600 2601/// GenerateCrossUseConstantOffsets - Look for registers which are a constant 2602/// distance apart and try to form reuse opportunities between them. 2603void LSRInstance::GenerateCrossUseConstantOffsets() { 2604 // Group the registers by their value without any added constant offset. 2605 typedef std::map<int64_t, const SCEV *> ImmMapTy; 2606 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy; 2607 RegMapTy Map; 2608 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap; 2609 SmallVector<const SCEV *, 8> Sequence; 2610 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end(); 2611 I != E; ++I) { 2612 const SCEV *Reg = *I; 2613 int64_t Imm = ExtractImmediate(Reg, SE); 2614 std::pair<RegMapTy::iterator, bool> Pair = 2615 Map.insert(std::make_pair(Reg, ImmMapTy())); 2616 if (Pair.second) 2617 Sequence.push_back(Reg); 2618 Pair.first->second.insert(std::make_pair(Imm, *I)); 2619 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I); 2620 } 2621 2622 // Now examine each set of registers with the same base value. Build up 2623 // a list of work to do and do the work in a separate step so that we're 2624 // not adding formulae and register counts while we're searching. 2625 SmallVector<WorkItem, 32> WorkItems; 2626 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems; 2627 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(), 2628 E = Sequence.end(); I != E; ++I) { 2629 const SCEV *Reg = *I; 2630 const ImmMapTy &Imms = Map.find(Reg)->second; 2631 2632 // It's not worthwhile looking for reuse if there's only one offset. 2633 if (Imms.size() == 1) 2634 continue; 2635 2636 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':'; 2637 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end(); 2638 J != JE; ++J) 2639 dbgs() << ' ' << J->first; 2640 dbgs() << '\n'); 2641 2642 // Examine each offset. 2643 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end(); 2644 J != JE; ++J) { 2645 const SCEV *OrigReg = J->second; 2646 2647 int64_t JImm = J->first; 2648 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg); 2649 2650 if (!isa<SCEVConstant>(OrigReg) && 2651 UsedByIndicesMap[Reg].count() == 1) { 2652 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n'); 2653 continue; 2654 } 2655 2656 // Conservatively examine offsets between this orig reg a few selected 2657 // other orig regs. 2658 ImmMapTy::const_iterator OtherImms[] = { 2659 Imms.begin(), prior(Imms.end()), 2660 Imms.upper_bound((Imms.begin()->first + prior(Imms.end())->first) / 2) 2661 }; 2662 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) { 2663 ImmMapTy::const_iterator M = OtherImms[i]; 2664 if (M == J || M == JE) continue; 2665 2666 // Compute the difference between the two. 2667 int64_t Imm = (uint64_t)JImm - M->first; 2668 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1; 2669 LUIdx = UsedByIndices.find_next(LUIdx)) 2670 // Make a memo of this use, offset, and register tuple. 2671 if (UniqueItems.insert(std::make_pair(LUIdx, Imm))) 2672 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg)); 2673 } 2674 } 2675 } 2676 2677 Map.clear(); 2678 Sequence.clear(); 2679 UsedByIndicesMap.clear(); 2680 UniqueItems.clear(); 2681 2682 // Now iterate through the worklist and add new formulae. 2683 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(), 2684 E = WorkItems.end(); I != E; ++I) { 2685 const WorkItem &WI = *I; 2686 size_t LUIdx = WI.LUIdx; 2687 LSRUse &LU = Uses[LUIdx]; 2688 int64_t Imm = WI.Imm; 2689 const SCEV *OrigReg = WI.OrigReg; 2690 2691 const Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType()); 2692 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm)); 2693 unsigned BitWidth = SE.getTypeSizeInBits(IntTy); 2694 2695 // TODO: Use a more targeted data structure. 2696 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) { 2697 const Formula &F = LU.Formulae[L]; 2698 // Use the immediate in the scaled register. 2699 if (F.ScaledReg == OrigReg) { 2700 int64_t Offs = (uint64_t)F.AM.BaseOffs + 2701 Imm * (uint64_t)F.AM.Scale; 2702 // Don't create 50 + reg(-50). 2703 if (F.referencesReg(SE.getSCEV( 2704 ConstantInt::get(IntTy, -(uint64_t)Offs)))) 2705 continue; 2706 Formula NewF = F; 2707 NewF.AM.BaseOffs = Offs; 2708 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset, 2709 LU.Kind, LU.AccessTy, TLI)) 2710 continue; 2711 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg); 2712 2713 // If the new scale is a constant in a register, and adding the constant 2714 // value to the immediate would produce a value closer to zero than the 2715 // immediate itself, then the formula isn't worthwhile. 2716 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg)) 2717 if (C->getValue()->getValue().isNegative() != 2718 (NewF.AM.BaseOffs < 0) && 2719 (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale)) 2720 .ule(abs64(NewF.AM.BaseOffs))) 2721 continue; 2722 2723 // OK, looks good. 2724 (void)InsertFormula(LU, LUIdx, NewF); 2725 } else { 2726 // Use the immediate in a base register. 2727 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) { 2728 const SCEV *BaseReg = F.BaseRegs[N]; 2729 if (BaseReg != OrigReg) 2730 continue; 2731 Formula NewF = F; 2732 NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm; 2733 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset, 2734 LU.Kind, LU.AccessTy, TLI)) 2735 continue; 2736 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg); 2737 2738 // If the new formula has a constant in a register, and adding the 2739 // constant value to the immediate would produce a value closer to 2740 // zero than the immediate itself, then the formula isn't worthwhile. 2741 for (SmallVectorImpl<const SCEV *>::const_iterator 2742 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end(); 2743 J != JE; ++J) 2744 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J)) 2745 if ((C->getValue()->getValue() + NewF.AM.BaseOffs).abs().slt( 2746 abs64(NewF.AM.BaseOffs)) && 2747 (C->getValue()->getValue() + 2748 NewF.AM.BaseOffs).countTrailingZeros() >= 2749 CountTrailingZeros_64(NewF.AM.BaseOffs)) 2750 goto skip_formula; 2751 2752 // Ok, looks good. 2753 (void)InsertFormula(LU, LUIdx, NewF); 2754 break; 2755 skip_formula:; 2756 } 2757 } 2758 } 2759 } 2760} 2761 2762/// GenerateAllReuseFormulae - Generate formulae for each use. 2763void 2764LSRInstance::GenerateAllReuseFormulae() { 2765 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan 2766 // queries are more precise. 2767 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2768 LSRUse &LU = Uses[LUIdx]; 2769 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2770 GenerateReassociations(LU, LUIdx, LU.Formulae[i]); 2771 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2772 GenerateCombinations(LU, LUIdx, LU.Formulae[i]); 2773 } 2774 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2775 LSRUse &LU = Uses[LUIdx]; 2776 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2777 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]); 2778 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2779 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]); 2780 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2781 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]); 2782 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2783 GenerateScales(LU, LUIdx, LU.Formulae[i]); 2784 } 2785 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2786 LSRUse &LU = Uses[LUIdx]; 2787 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2788 GenerateTruncates(LU, LUIdx, LU.Formulae[i]); 2789 } 2790 2791 GenerateCrossUseConstantOffsets(); 2792 2793 DEBUG(dbgs() << "\n" 2794 "After generating reuse formulae:\n"; 2795 print_uses(dbgs())); 2796} 2797 2798/// If there are multiple formulae with the same set of registers used 2799/// by other uses, pick the best one and delete the others. 2800void LSRInstance::FilterOutUndesirableDedicatedRegisters() { 2801 DenseSet<const SCEV *> VisitedRegs; 2802 SmallPtrSet<const SCEV *, 16> Regs; 2803#ifndef NDEBUG 2804 bool ChangedFormulae = false; 2805#endif 2806 2807 // Collect the best formula for each unique set of shared registers. This 2808 // is reset for each use. 2809 typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo> 2810 BestFormulaeTy; 2811 BestFormulaeTy BestFormulae; 2812 2813 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2814 LSRUse &LU = Uses[LUIdx]; 2815 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n'); 2816 2817 bool Any = false; 2818 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); 2819 FIdx != NumForms; ++FIdx) { 2820 Formula &F = LU.Formulae[FIdx]; 2821 2822 SmallVector<const SCEV *, 2> Key; 2823 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(), 2824 JE = F.BaseRegs.end(); J != JE; ++J) { 2825 const SCEV *Reg = *J; 2826 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx)) 2827 Key.push_back(Reg); 2828 } 2829 if (F.ScaledReg && 2830 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx)) 2831 Key.push_back(F.ScaledReg); 2832 // Unstable sort by host order ok, because this is only used for 2833 // uniquifying. 2834 std::sort(Key.begin(), Key.end()); 2835 2836 std::pair<BestFormulaeTy::const_iterator, bool> P = 2837 BestFormulae.insert(std::make_pair(Key, FIdx)); 2838 if (!P.second) { 2839 Formula &Best = LU.Formulae[P.first->second]; 2840 2841 Cost CostF; 2842 CostF.RateFormula(F, Regs, VisitedRegs, L, LU.Offsets, SE, DT); 2843 Regs.clear(); 2844 Cost CostBest; 2845 CostBest.RateFormula(Best, Regs, VisitedRegs, L, LU.Offsets, SE, DT); 2846 Regs.clear(); 2847 if (CostF < CostBest) 2848 std::swap(F, Best); 2849 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs()); 2850 dbgs() << "\n" 2851 " in favor of formula "; Best.print(dbgs()); 2852 dbgs() << '\n'); 2853#ifndef NDEBUG 2854 ChangedFormulae = true; 2855#endif 2856 LU.DeleteFormula(F); 2857 --FIdx; 2858 --NumForms; 2859 Any = true; 2860 continue; 2861 } 2862 } 2863 2864 // Now that we've filtered out some formulae, recompute the Regs set. 2865 if (Any) 2866 LU.RecomputeRegs(LUIdx, RegUses); 2867 2868 // Reset this to prepare for the next use. 2869 BestFormulae.clear(); 2870 } 2871 2872 DEBUG(if (ChangedFormulae) { 2873 dbgs() << "\n" 2874 "After filtering out undesirable candidates:\n"; 2875 print_uses(dbgs()); 2876 }); 2877} 2878 2879// This is a rough guess that seems to work fairly well. 2880static const size_t ComplexityLimit = UINT16_MAX; 2881 2882/// EstimateSearchSpaceComplexity - Estimate the worst-case number of 2883/// solutions the solver might have to consider. It almost never considers 2884/// this many solutions because it prune the search space, but the pruning 2885/// isn't always sufficient. 2886size_t LSRInstance::EstimateSearchSpaceComplexity() const { 2887 size_t Power = 1; 2888 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), 2889 E = Uses.end(); I != E; ++I) { 2890 size_t FSize = I->Formulae.size(); 2891 if (FSize >= ComplexityLimit) { 2892 Power = ComplexityLimit; 2893 break; 2894 } 2895 Power *= FSize; 2896 if (Power >= ComplexityLimit) 2897 break; 2898 } 2899 return Power; 2900} 2901 2902/// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset 2903/// of the registers of another formula, it won't help reduce register 2904/// pressure (though it may not necessarily hurt register pressure); remove 2905/// it to simplify the system. 2906void LSRInstance::NarrowSearchSpaceByDetectingSupersets() { 2907 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 2908 DEBUG(dbgs() << "The search space is too complex.\n"); 2909 2910 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae " 2911 "which use a superset of registers used by other " 2912 "formulae.\n"); 2913 2914 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2915 LSRUse &LU = Uses[LUIdx]; 2916 bool Any = false; 2917 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { 2918 Formula &F = LU.Formulae[i]; 2919 // Look for a formula with a constant or GV in a register. If the use 2920 // also has a formula with that same value in an immediate field, 2921 // delete the one that uses a register. 2922 for (SmallVectorImpl<const SCEV *>::const_iterator 2923 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) { 2924 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) { 2925 Formula NewF = F; 2926 NewF.AM.BaseOffs += C->getValue()->getSExtValue(); 2927 NewF.BaseRegs.erase(NewF.BaseRegs.begin() + 2928 (I - F.BaseRegs.begin())); 2929 if (LU.HasFormulaWithSameRegs(NewF)) { 2930 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); 2931 LU.DeleteFormula(F); 2932 --i; 2933 --e; 2934 Any = true; 2935 break; 2936 } 2937 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) { 2938 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) 2939 if (!F.AM.BaseGV) { 2940 Formula NewF = F; 2941 NewF.AM.BaseGV = GV; 2942 NewF.BaseRegs.erase(NewF.BaseRegs.begin() + 2943 (I - F.BaseRegs.begin())); 2944 if (LU.HasFormulaWithSameRegs(NewF)) { 2945 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); 2946 dbgs() << '\n'); 2947 LU.DeleteFormula(F); 2948 --i; 2949 --e; 2950 Any = true; 2951 break; 2952 } 2953 } 2954 } 2955 } 2956 } 2957 if (Any) 2958 LU.RecomputeRegs(LUIdx, RegUses); 2959 } 2960 2961 DEBUG(dbgs() << "After pre-selection:\n"; 2962 print_uses(dbgs())); 2963 } 2964} 2965 2966/// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers 2967/// for expressions like A, A+1, A+2, etc., allocate a single register for 2968/// them. 2969void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() { 2970 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 2971 DEBUG(dbgs() << "The search space is too complex.\n"); 2972 2973 DEBUG(dbgs() << "Narrowing the search space by assuming that uses " 2974 "separated by a constant offset will use the same " 2975 "registers.\n"); 2976 2977 // This is especially useful for unrolled loops. 2978 2979 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2980 LSRUse &LU = Uses[LUIdx]; 2981 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), 2982 E = LU.Formulae.end(); I != E; ++I) { 2983 const Formula &F = *I; 2984 if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) { 2985 if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) { 2986 if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs, 2987 /*HasBaseReg=*/false, 2988 LU.Kind, LU.AccessTy)) { 2989 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); 2990 dbgs() << '\n'); 2991 2992 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop; 2993 2994 // Update the relocs to reference the new use. 2995 for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(), 2996 E = Fixups.end(); I != E; ++I) { 2997 LSRFixup &Fixup = *I; 2998 if (Fixup.LUIdx == LUIdx) { 2999 Fixup.LUIdx = LUThatHas - &Uses.front(); 3000 Fixup.Offset += F.AM.BaseOffs; 3001 // Add the new offset to LUThatHas' offset list. 3002 if (LUThatHas->Offsets.back() != Fixup.Offset) { 3003 LUThatHas->Offsets.push_back(Fixup.Offset); 3004 if (Fixup.Offset > LUThatHas->MaxOffset) 3005 LUThatHas->MaxOffset = Fixup.Offset; 3006 if (Fixup.Offset < LUThatHas->MinOffset) 3007 LUThatHas->MinOffset = Fixup.Offset; 3008 } 3009 DEBUG(dbgs() << "New fixup has offset " 3010 << Fixup.Offset << '\n'); 3011 } 3012 if (Fixup.LUIdx == NumUses-1) 3013 Fixup.LUIdx = LUIdx; 3014 } 3015 3016 // Delete formulae from the new use which are no longer legal. 3017 bool Any = false; 3018 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) { 3019 Formula &F = LUThatHas->Formulae[i]; 3020 if (!isLegalUse(F.AM, 3021 LUThatHas->MinOffset, LUThatHas->MaxOffset, 3022 LUThatHas->Kind, LUThatHas->AccessTy, TLI)) { 3023 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); 3024 dbgs() << '\n'); 3025 LUThatHas->DeleteFormula(F); 3026 --i; 3027 --e; 3028 Any = true; 3029 } 3030 } 3031 if (Any) 3032 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses); 3033 3034 // Delete the old use. 3035 DeleteUse(LU, LUIdx); 3036 --LUIdx; 3037 --NumUses; 3038 break; 3039 } 3040 } 3041 } 3042 } 3043 } 3044 3045 DEBUG(dbgs() << "After pre-selection:\n"; 3046 print_uses(dbgs())); 3047 } 3048} 3049 3050/// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call 3051/// FilterOutUndesirableDedicatedRegisters again, if necessary, now that 3052/// we've done more filtering, as it may be able to find more formulae to 3053/// eliminate. 3054void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){ 3055 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 3056 DEBUG(dbgs() << "The search space is too complex.\n"); 3057 3058 DEBUG(dbgs() << "Narrowing the search space by re-filtering out " 3059 "undesirable dedicated registers.\n"); 3060 3061 FilterOutUndesirableDedicatedRegisters(); 3062 3063 DEBUG(dbgs() << "After pre-selection:\n"; 3064 print_uses(dbgs())); 3065 } 3066} 3067 3068/// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely 3069/// to be profitable, and then in any use which has any reference to that 3070/// register, delete all formulae which do not reference that register. 3071void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() { 3072 // With all other options exhausted, loop until the system is simple 3073 // enough to handle. 3074 SmallPtrSet<const SCEV *, 4> Taken; 3075 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 3076 // Ok, we have too many of formulae on our hands to conveniently handle. 3077 // Use a rough heuristic to thin out the list. 3078 DEBUG(dbgs() << "The search space is too complex.\n"); 3079 3080 // Pick the register which is used by the most LSRUses, which is likely 3081 // to be a good reuse register candidate. 3082 const SCEV *Best = 0; 3083 unsigned BestNum = 0; 3084 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end(); 3085 I != E; ++I) { 3086 const SCEV *Reg = *I; 3087 if (Taken.count(Reg)) 3088 continue; 3089 if (!Best) 3090 Best = Reg; 3091 else { 3092 unsigned Count = RegUses.getUsedByIndices(Reg).count(); 3093 if (Count > BestNum) { 3094 Best = Reg; 3095 BestNum = Count; 3096 } 3097 } 3098 } 3099 3100 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best 3101 << " will yield profitable reuse.\n"); 3102 Taken.insert(Best); 3103 3104 // In any use with formulae which references this register, delete formulae 3105 // which don't reference it. 3106 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3107 LSRUse &LU = Uses[LUIdx]; 3108 if (!LU.Regs.count(Best)) continue; 3109 3110 bool Any = false; 3111 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { 3112 Formula &F = LU.Formulae[i]; 3113 if (!F.referencesReg(Best)) { 3114 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); 3115 LU.DeleteFormula(F); 3116 --e; 3117 --i; 3118 Any = true; 3119 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?"); 3120 continue; 3121 } 3122 } 3123 3124 if (Any) 3125 LU.RecomputeRegs(LUIdx, RegUses); 3126 } 3127 3128 DEBUG(dbgs() << "After pre-selection:\n"; 3129 print_uses(dbgs())); 3130 } 3131} 3132 3133/// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of 3134/// formulae to choose from, use some rough heuristics to prune down the number 3135/// of formulae. This keeps the main solver from taking an extraordinary amount 3136/// of time in some worst-case scenarios. 3137void LSRInstance::NarrowSearchSpaceUsingHeuristics() { 3138 NarrowSearchSpaceByDetectingSupersets(); 3139 NarrowSearchSpaceByCollapsingUnrolledCode(); 3140 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(); 3141 NarrowSearchSpaceByPickingWinnerRegs(); 3142} 3143 3144/// SolveRecurse - This is the recursive solver. 3145void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution, 3146 Cost &SolutionCost, 3147 SmallVectorImpl<const Formula *> &Workspace, 3148 const Cost &CurCost, 3149 const SmallPtrSet<const SCEV *, 16> &CurRegs, 3150 DenseSet<const SCEV *> &VisitedRegs) const { 3151 // Some ideas: 3152 // - prune more: 3153 // - use more aggressive filtering 3154 // - sort the formula so that the most profitable solutions are found first 3155 // - sort the uses too 3156 // - search faster: 3157 // - don't compute a cost, and then compare. compare while computing a cost 3158 // and bail early. 3159 // - track register sets with SmallBitVector 3160 3161 const LSRUse &LU = Uses[Workspace.size()]; 3162 3163 // If this use references any register that's already a part of the 3164 // in-progress solution, consider it a requirement that a formula must 3165 // reference that register in order to be considered. This prunes out 3166 // unprofitable searching. 3167 SmallSetVector<const SCEV *, 4> ReqRegs; 3168 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(), 3169 E = CurRegs.end(); I != E; ++I) 3170 if (LU.Regs.count(*I)) 3171 ReqRegs.insert(*I); 3172 3173 bool AnySatisfiedReqRegs = false; 3174 SmallPtrSet<const SCEV *, 16> NewRegs; 3175 Cost NewCost; 3176retry: 3177 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), 3178 E = LU.Formulae.end(); I != E; ++I) { 3179 const Formula &F = *I; 3180 3181 // Ignore formulae which do not use any of the required registers. 3182 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(), 3183 JE = ReqRegs.end(); J != JE; ++J) { 3184 const SCEV *Reg = *J; 3185 if ((!F.ScaledReg || F.ScaledReg != Reg) && 3186 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) == 3187 F.BaseRegs.end()) 3188 goto skip; 3189 } 3190 AnySatisfiedReqRegs = true; 3191 3192 // Evaluate the cost of the current formula. If it's already worse than 3193 // the current best, prune the search at that point. 3194 NewCost = CurCost; 3195 NewRegs = CurRegs; 3196 NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT); 3197 if (NewCost < SolutionCost) { 3198 Workspace.push_back(&F); 3199 if (Workspace.size() != Uses.size()) { 3200 SolveRecurse(Solution, SolutionCost, Workspace, NewCost, 3201 NewRegs, VisitedRegs); 3202 if (F.getNumRegs() == 1 && Workspace.size() == 1) 3203 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]); 3204 } else { 3205 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs()); 3206 dbgs() << ". Regs:"; 3207 for (SmallPtrSet<const SCEV *, 16>::const_iterator 3208 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I) 3209 dbgs() << ' ' << **I; 3210 dbgs() << '\n'); 3211 3212 SolutionCost = NewCost; 3213 Solution = Workspace; 3214 } 3215 Workspace.pop_back(); 3216 } 3217 skip:; 3218 } 3219 3220 // If none of the formulae had all of the required registers, relax the 3221 // constraint so that we don't exclude all formulae. 3222 if (!AnySatisfiedReqRegs) { 3223 assert(!ReqRegs.empty() && "Solver failed even without required registers"); 3224 ReqRegs.clear(); 3225 goto retry; 3226 } 3227} 3228 3229/// Solve - Choose one formula from each use. Return the results in the given 3230/// Solution vector. 3231void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const { 3232 SmallVector<const Formula *, 8> Workspace; 3233 Cost SolutionCost; 3234 SolutionCost.Loose(); 3235 Cost CurCost; 3236 SmallPtrSet<const SCEV *, 16> CurRegs; 3237 DenseSet<const SCEV *> VisitedRegs; 3238 Workspace.reserve(Uses.size()); 3239 3240 // SolveRecurse does all the work. 3241 SolveRecurse(Solution, SolutionCost, Workspace, CurCost, 3242 CurRegs, VisitedRegs); 3243 3244 // Ok, we've now made all our decisions. 3245 DEBUG(dbgs() << "\n" 3246 "The chosen solution requires "; SolutionCost.print(dbgs()); 3247 dbgs() << ":\n"; 3248 for (size_t i = 0, e = Uses.size(); i != e; ++i) { 3249 dbgs() << " "; 3250 Uses[i].print(dbgs()); 3251 dbgs() << "\n" 3252 " "; 3253 Solution[i]->print(dbgs()); 3254 dbgs() << '\n'; 3255 }); 3256 3257 assert(Solution.size() == Uses.size() && "Malformed solution!"); 3258} 3259 3260/// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up 3261/// the dominator tree far as we can go while still being dominated by the 3262/// input positions. This helps canonicalize the insert position, which 3263/// encourages sharing. 3264BasicBlock::iterator 3265LSRInstance::HoistInsertPosition(BasicBlock::iterator IP, 3266 const SmallVectorImpl<Instruction *> &Inputs) 3267 const { 3268 for (;;) { 3269 const Loop *IPLoop = LI.getLoopFor(IP->getParent()); 3270 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0; 3271 3272 BasicBlock *IDom; 3273 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) { 3274 if (!Rung) return IP; 3275 Rung = Rung->getIDom(); 3276 if (!Rung) return IP; 3277 IDom = Rung->getBlock(); 3278 3279 // Don't climb into a loop though. 3280 const Loop *IDomLoop = LI.getLoopFor(IDom); 3281 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0; 3282 if (IDomDepth <= IPLoopDepth && 3283 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop)) 3284 break; 3285 } 3286 3287 bool AllDominate = true; 3288 Instruction *BetterPos = 0; 3289 Instruction *Tentative = IDom->getTerminator(); 3290 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(), 3291 E = Inputs.end(); I != E; ++I) { 3292 Instruction *Inst = *I; 3293 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) { 3294 AllDominate = false; 3295 break; 3296 } 3297 // Attempt to find an insert position in the middle of the block, 3298 // instead of at the end, so that it can be used for other expansions. 3299 if (IDom == Inst->getParent() && 3300 (!BetterPos || DT.dominates(BetterPos, Inst))) 3301 BetterPos = llvm::next(BasicBlock::iterator(Inst)); 3302 } 3303 if (!AllDominate) 3304 break; 3305 if (BetterPos) 3306 IP = BetterPos; 3307 else 3308 IP = Tentative; 3309 } 3310 3311 return IP; 3312} 3313 3314/// AdjustInsertPositionForExpand - Determine an input position which will be 3315/// dominated by the operands and which will dominate the result. 3316BasicBlock::iterator 3317LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator IP, 3318 const LSRFixup &LF, 3319 const LSRUse &LU) const { 3320 // Collect some instructions which must be dominated by the 3321 // expanding replacement. These must be dominated by any operands that 3322 // will be required in the expansion. 3323 SmallVector<Instruction *, 4> Inputs; 3324 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace)) 3325 Inputs.push_back(I); 3326 if (LU.Kind == LSRUse::ICmpZero) 3327 if (Instruction *I = 3328 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1))) 3329 Inputs.push_back(I); 3330 if (LF.PostIncLoops.count(L)) { 3331 if (LF.isUseFullyOutsideLoop(L)) 3332 Inputs.push_back(L->getLoopLatch()->getTerminator()); 3333 else 3334 Inputs.push_back(IVIncInsertPos); 3335 } 3336 // The expansion must also be dominated by the increment positions of any 3337 // loops it for which it is using post-inc mode. 3338 for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(), 3339 E = LF.PostIncLoops.end(); I != E; ++I) { 3340 const Loop *PIL = *I; 3341 if (PIL == L) continue; 3342 3343 // Be dominated by the loop exit. 3344 SmallVector<BasicBlock *, 4> ExitingBlocks; 3345 PIL->getExitingBlocks(ExitingBlocks); 3346 if (!ExitingBlocks.empty()) { 3347 BasicBlock *BB = ExitingBlocks[0]; 3348 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i) 3349 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]); 3350 Inputs.push_back(BB->getTerminator()); 3351 } 3352 } 3353 3354 // Then, climb up the immediate dominator tree as far as we can go while 3355 // still being dominated by the input positions. 3356 IP = HoistInsertPosition(IP, Inputs); 3357 3358 // Don't insert instructions before PHI nodes. 3359 while (isa<PHINode>(IP)) ++IP; 3360 3361 // Ignore debug intrinsics. 3362 while (isa<DbgInfoIntrinsic>(IP)) ++IP; 3363 3364 return IP; 3365} 3366 3367/// Expand - Emit instructions for the leading candidate expression for this 3368/// LSRUse (this is called "expanding"). 3369Value *LSRInstance::Expand(const LSRFixup &LF, 3370 const Formula &F, 3371 BasicBlock::iterator IP, 3372 SCEVExpander &Rewriter, 3373 SmallVectorImpl<WeakVH> &DeadInsts) const { 3374 const LSRUse &LU = Uses[LF.LUIdx]; 3375 3376 // Determine an input position which will be dominated by the operands and 3377 // which will dominate the result. 3378 IP = AdjustInsertPositionForExpand(IP, LF, LU); 3379 3380 // Inform the Rewriter if we have a post-increment use, so that it can 3381 // perform an advantageous expansion. 3382 Rewriter.setPostInc(LF.PostIncLoops); 3383 3384 // This is the type that the user actually needs. 3385 const Type *OpTy = LF.OperandValToReplace->getType(); 3386 // This will be the type that we'll initially expand to. 3387 const Type *Ty = F.getType(); 3388 if (!Ty) 3389 // No type known; just expand directly to the ultimate type. 3390 Ty = OpTy; 3391 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy)) 3392 // Expand directly to the ultimate type if it's the right size. 3393 Ty = OpTy; 3394 // This is the type to do integer arithmetic in. 3395 const Type *IntTy = SE.getEffectiveSCEVType(Ty); 3396 3397 // Build up a list of operands to add together to form the full base. 3398 SmallVector<const SCEV *, 8> Ops; 3399 3400 // Expand the BaseRegs portion. 3401 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), 3402 E = F.BaseRegs.end(); I != E; ++I) { 3403 const SCEV *Reg = *I; 3404 assert(!Reg->isZero() && "Zero allocated in a base register!"); 3405 3406 // If we're expanding for a post-inc user, make the post-inc adjustment. 3407 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); 3408 Reg = TransformForPostIncUse(Denormalize, Reg, 3409 LF.UserInst, LF.OperandValToReplace, 3410 Loops, SE, DT); 3411 3412 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP))); 3413 } 3414 3415 // Flush the operand list to suppress SCEVExpander hoisting. 3416 if (!Ops.empty()) { 3417 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); 3418 Ops.clear(); 3419 Ops.push_back(SE.getUnknown(FullV)); 3420 } 3421 3422 // Expand the ScaledReg portion. 3423 Value *ICmpScaledV = 0; 3424 if (F.AM.Scale != 0) { 3425 const SCEV *ScaledS = F.ScaledReg; 3426 3427 // If we're expanding for a post-inc user, make the post-inc adjustment. 3428 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); 3429 ScaledS = TransformForPostIncUse(Denormalize, ScaledS, 3430 LF.UserInst, LF.OperandValToReplace, 3431 Loops, SE, DT); 3432 3433 if (LU.Kind == LSRUse::ICmpZero) { 3434 // An interesting way of "folding" with an icmp is to use a negated 3435 // scale, which we'll implement by inserting it into the other operand 3436 // of the icmp. 3437 assert(F.AM.Scale == -1 && 3438 "The only scale supported by ICmpZero uses is -1!"); 3439 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP); 3440 } else { 3441 // Otherwise just expand the scaled register and an explicit scale, 3442 // which is expected to be matched as part of the address. 3443 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP)); 3444 ScaledS = SE.getMulExpr(ScaledS, 3445 SE.getConstant(ScaledS->getType(), F.AM.Scale)); 3446 Ops.push_back(ScaledS); 3447 3448 // Flush the operand list to suppress SCEVExpander hoisting. 3449 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); 3450 Ops.clear(); 3451 Ops.push_back(SE.getUnknown(FullV)); 3452 } 3453 } 3454 3455 // Expand the GV portion. 3456 if (F.AM.BaseGV) { 3457 Ops.push_back(SE.getUnknown(F.AM.BaseGV)); 3458 3459 // Flush the operand list to suppress SCEVExpander hoisting. 3460 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); 3461 Ops.clear(); 3462 Ops.push_back(SE.getUnknown(FullV)); 3463 } 3464 3465 // Expand the immediate portion. 3466 int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset; 3467 if (Offset != 0) { 3468 if (LU.Kind == LSRUse::ICmpZero) { 3469 // The other interesting way of "folding" with an ICmpZero is to use a 3470 // negated immediate. 3471 if (!ICmpScaledV) 3472 ICmpScaledV = ConstantInt::get(IntTy, -Offset); 3473 else { 3474 Ops.push_back(SE.getUnknown(ICmpScaledV)); 3475 ICmpScaledV = ConstantInt::get(IntTy, Offset); 3476 } 3477 } else { 3478 // Just add the immediate values. These again are expected to be matched 3479 // as part of the address. 3480 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset))); 3481 } 3482 } 3483 3484 // Emit instructions summing all the operands. 3485 const SCEV *FullS = Ops.empty() ? 3486 SE.getConstant(IntTy, 0) : 3487 SE.getAddExpr(Ops); 3488 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP); 3489 3490 // We're done expanding now, so reset the rewriter. 3491 Rewriter.clearPostInc(); 3492 3493 // An ICmpZero Formula represents an ICmp which we're handling as a 3494 // comparison against zero. Now that we've expanded an expression for that 3495 // form, update the ICmp's other operand. 3496 if (LU.Kind == LSRUse::ICmpZero) { 3497 ICmpInst *CI = cast<ICmpInst>(LF.UserInst); 3498 DeadInsts.push_back(CI->getOperand(1)); 3499 assert(!F.AM.BaseGV && "ICmp does not support folding a global value and " 3500 "a scale at the same time!"); 3501 if (F.AM.Scale == -1) { 3502 if (ICmpScaledV->getType() != OpTy) { 3503 Instruction *Cast = 3504 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false, 3505 OpTy, false), 3506 ICmpScaledV, OpTy, "tmp", CI); 3507 ICmpScaledV = Cast; 3508 } 3509 CI->setOperand(1, ICmpScaledV); 3510 } else { 3511 assert(F.AM.Scale == 0 && 3512 "ICmp does not support folding a global value and " 3513 "a scale at the same time!"); 3514 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy), 3515 -(uint64_t)Offset); 3516 if (C->getType() != OpTy) 3517 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 3518 OpTy, false), 3519 C, OpTy); 3520 3521 CI->setOperand(1, C); 3522 } 3523 } 3524 3525 return FullV; 3526} 3527 3528/// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use 3529/// of their operands effectively happens in their predecessor blocks, so the 3530/// expression may need to be expanded in multiple places. 3531void LSRInstance::RewriteForPHI(PHINode *PN, 3532 const LSRFixup &LF, 3533 const Formula &F, 3534 SCEVExpander &Rewriter, 3535 SmallVectorImpl<WeakVH> &DeadInsts, 3536 Pass *P) const { 3537 DenseMap<BasicBlock *, Value *> Inserted; 3538 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 3539 if (PN->getIncomingValue(i) == LF.OperandValToReplace) { 3540 BasicBlock *BB = PN->getIncomingBlock(i); 3541 3542 // If this is a critical edge, split the edge so that we do not insert 3543 // the code on all predecessor/successor paths. We do this unless this 3544 // is the canonical backedge for this loop, which complicates post-inc 3545 // users. 3546 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 && 3547 !isa<IndirectBrInst>(BB->getTerminator()) && 3548 (PN->getParent() != L->getHeader() || !L->contains(BB))) { 3549 // Split the critical edge. 3550 BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P); 3551 3552 // If PN is outside of the loop and BB is in the loop, we want to 3553 // move the block to be immediately before the PHI block, not 3554 // immediately after BB. 3555 if (L->contains(BB) && !L->contains(PN)) 3556 NewBB->moveBefore(PN->getParent()); 3557 3558 // Splitting the edge can reduce the number of PHI entries we have. 3559 e = PN->getNumIncomingValues(); 3560 BB = NewBB; 3561 i = PN->getBasicBlockIndex(BB); 3562 } 3563 3564 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair = 3565 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0))); 3566 if (!Pair.second) 3567 PN->setIncomingValue(i, Pair.first->second); 3568 else { 3569 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts); 3570 3571 // If this is reuse-by-noop-cast, insert the noop cast. 3572 const Type *OpTy = LF.OperandValToReplace->getType(); 3573 if (FullV->getType() != OpTy) 3574 FullV = 3575 CastInst::Create(CastInst::getCastOpcode(FullV, false, 3576 OpTy, false), 3577 FullV, LF.OperandValToReplace->getType(), 3578 "tmp", BB->getTerminator()); 3579 3580 PN->setIncomingValue(i, FullV); 3581 Pair.first->second = FullV; 3582 } 3583 } 3584} 3585 3586/// Rewrite - Emit instructions for the leading candidate expression for this 3587/// LSRUse (this is called "expanding"), and update the UserInst to reference 3588/// the newly expanded value. 3589void LSRInstance::Rewrite(const LSRFixup &LF, 3590 const Formula &F, 3591 SCEVExpander &Rewriter, 3592 SmallVectorImpl<WeakVH> &DeadInsts, 3593 Pass *P) const { 3594 // First, find an insertion point that dominates UserInst. For PHI nodes, 3595 // find the nearest block which dominates all the relevant uses. 3596 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) { 3597 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P); 3598 } else { 3599 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts); 3600 3601 // If this is reuse-by-noop-cast, insert the noop cast. 3602 const Type *OpTy = LF.OperandValToReplace->getType(); 3603 if (FullV->getType() != OpTy) { 3604 Instruction *Cast = 3605 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false), 3606 FullV, OpTy, "tmp", LF.UserInst); 3607 FullV = Cast; 3608 } 3609 3610 // Update the user. ICmpZero is handled specially here (for now) because 3611 // Expand may have updated one of the operands of the icmp already, and 3612 // its new value may happen to be equal to LF.OperandValToReplace, in 3613 // which case doing replaceUsesOfWith leads to replacing both operands 3614 // with the same value. TODO: Reorganize this. 3615 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero) 3616 LF.UserInst->setOperand(0, FullV); 3617 else 3618 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV); 3619 } 3620 3621 DeadInsts.push_back(LF.OperandValToReplace); 3622} 3623 3624/// ImplementSolution - Rewrite all the fixup locations with new values, 3625/// following the chosen solution. 3626void 3627LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution, 3628 Pass *P) { 3629 // Keep track of instructions we may have made dead, so that 3630 // we can remove them after we are done working. 3631 SmallVector<WeakVH, 16> DeadInsts; 3632 3633 SCEVExpander Rewriter(SE); 3634 Rewriter.disableCanonicalMode(); 3635 Rewriter.setIVIncInsertPos(L, IVIncInsertPos); 3636 3637 // Expand the new value definitions and update the users. 3638 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(), 3639 E = Fixups.end(); I != E; ++I) { 3640 const LSRFixup &Fixup = *I; 3641 3642 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P); 3643 3644 Changed = true; 3645 } 3646 3647 // Clean up after ourselves. This must be done before deleting any 3648 // instructions. 3649 Rewriter.clear(); 3650 3651 Changed |= DeleteTriviallyDeadInstructions(DeadInsts); 3652} 3653 3654LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P) 3655 : IU(P->getAnalysis<IVUsers>()), 3656 SE(P->getAnalysis<ScalarEvolution>()), 3657 DT(P->getAnalysis<DominatorTree>()), 3658 LI(P->getAnalysis<LoopInfo>()), 3659 TLI(tli), L(l), Changed(false), IVIncInsertPos(0) { 3660 3661 // If LoopSimplify form is not available, stay out of trouble. 3662 if (!L->isLoopSimplifyForm()) return; 3663 3664 // If there's no interesting work to be done, bail early. 3665 if (IU.empty()) return; 3666 3667 DEBUG(dbgs() << "\nLSR on loop "; 3668 WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false); 3669 dbgs() << ":\n"); 3670 3671 // First, perform some low-level loop optimizations. 3672 OptimizeShadowIV(); 3673 OptimizeLoopTermCond(); 3674 3675 // Start collecting data and preparing for the solver. 3676 CollectInterestingTypesAndFactors(); 3677 CollectFixupsAndInitialFormulae(); 3678 CollectLoopInvariantFixupsAndFormulae(); 3679 3680 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n"; 3681 print_uses(dbgs())); 3682 3683 // Now use the reuse data to generate a bunch of interesting ways 3684 // to formulate the values needed for the uses. 3685 GenerateAllReuseFormulae(); 3686 3687 FilterOutUndesirableDedicatedRegisters(); 3688 NarrowSearchSpaceUsingHeuristics(); 3689 3690 SmallVector<const Formula *, 8> Solution; 3691 Solve(Solution); 3692 3693 // Release memory that is no longer needed. 3694 Factors.clear(); 3695 Types.clear(); 3696 RegUses.clear(); 3697 3698#ifndef NDEBUG 3699 // Formulae should be legal. 3700 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), 3701 E = Uses.end(); I != E; ++I) { 3702 const LSRUse &LU = *I; 3703 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(), 3704 JE = LU.Formulae.end(); J != JE; ++J) 3705 assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset, 3706 LU.Kind, LU.AccessTy, TLI) && 3707 "Illegal formula generated!"); 3708 }; 3709#endif 3710 3711 // Now that we've decided what we want, make it so. 3712 ImplementSolution(Solution, P); 3713} 3714 3715void LSRInstance::print_factors_and_types(raw_ostream &OS) const { 3716 if (Factors.empty() && Types.empty()) return; 3717 3718 OS << "LSR has identified the following interesting factors and types: "; 3719 bool First = true; 3720 3721 for (SmallSetVector<int64_t, 8>::const_iterator 3722 I = Factors.begin(), E = Factors.end(); I != E; ++I) { 3723 if (!First) OS << ", "; 3724 First = false; 3725 OS << '*' << *I; 3726 } 3727 3728 for (SmallSetVector<const Type *, 4>::const_iterator 3729 I = Types.begin(), E = Types.end(); I != E; ++I) { 3730 if (!First) OS << ", "; 3731 First = false; 3732 OS << '(' << **I << ')'; 3733 } 3734 OS << '\n'; 3735} 3736 3737void LSRInstance::print_fixups(raw_ostream &OS) const { 3738 OS << "LSR is examining the following fixup sites:\n"; 3739 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(), 3740 E = Fixups.end(); I != E; ++I) { 3741 dbgs() << " "; 3742 I->print(OS); 3743 OS << '\n'; 3744 } 3745} 3746 3747void LSRInstance::print_uses(raw_ostream &OS) const { 3748 OS << "LSR is examining the following uses:\n"; 3749 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), 3750 E = Uses.end(); I != E; ++I) { 3751 const LSRUse &LU = *I; 3752 dbgs() << " "; 3753 LU.print(OS); 3754 OS << '\n'; 3755 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(), 3756 JE = LU.Formulae.end(); J != JE; ++J) { 3757 OS << " "; 3758 J->print(OS); 3759 OS << '\n'; 3760 } 3761 } 3762} 3763 3764void LSRInstance::print(raw_ostream &OS) const { 3765 print_factors_and_types(OS); 3766 print_fixups(OS); 3767 print_uses(OS); 3768} 3769 3770void LSRInstance::dump() const { 3771 print(errs()); errs() << '\n'; 3772} 3773 3774namespace { 3775 3776class LoopStrengthReduce : public LoopPass { 3777 /// TLI - Keep a pointer of a TargetLowering to consult for determining 3778 /// transformation profitability. 3779 const TargetLowering *const TLI; 3780 3781public: 3782 static char ID; // Pass ID, replacement for typeid 3783 explicit LoopStrengthReduce(const TargetLowering *tli = 0); 3784 3785private: 3786 bool runOnLoop(Loop *L, LPPassManager &LPM); 3787 void getAnalysisUsage(AnalysisUsage &AU) const; 3788}; 3789 3790} 3791 3792char LoopStrengthReduce::ID = 0; 3793INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce", 3794 "Loop Strength Reduction", false, false) 3795INITIALIZE_PASS_DEPENDENCY(DominatorTree) 3796INITIALIZE_PASS_DEPENDENCY(ScalarEvolution) 3797INITIALIZE_PASS_DEPENDENCY(IVUsers) 3798INITIALIZE_PASS_DEPENDENCY(LoopInfo) 3799INITIALIZE_PASS_DEPENDENCY(LoopSimplify) 3800INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce", 3801 "Loop Strength Reduction", false, false) 3802 3803 3804Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) { 3805 return new LoopStrengthReduce(TLI); 3806} 3807 3808LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli) 3809 : LoopPass(ID), TLI(tli) { 3810 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry()); 3811 } 3812 3813void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const { 3814 // We split critical edges, so we change the CFG. However, we do update 3815 // many analyses if they are around. 3816 AU.addPreservedID(LoopSimplifyID); 3817 AU.addPreserved("domfrontier"); 3818 3819 AU.addRequired<LoopInfo>(); 3820 AU.addPreserved<LoopInfo>(); 3821 AU.addRequiredID(LoopSimplifyID); 3822 AU.addRequired<DominatorTree>(); 3823 AU.addPreserved<DominatorTree>(); 3824 AU.addRequired<ScalarEvolution>(); 3825 AU.addPreserved<ScalarEvolution>(); 3826 AU.addRequired<IVUsers>(); 3827 AU.addPreserved<IVUsers>(); 3828} 3829 3830bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) { 3831 bool Changed = false; 3832 3833 // Run the main LSR transformation. 3834 Changed |= LSRInstance(TLI, L, this).getChanged(); 3835 3836 // At this point, it is worth checking to see if any recurrence PHIs are also 3837 // dead, so that we can remove them as well. 3838 Changed |= DeleteDeadPHIs(L->getHeader()); 3839 3840 return Changed; 3841} 3842