LoopStrengthReduce.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338
1//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This transformation analyzes and transforms the induction variables (and 11// computations derived from them) into forms suitable for efficient execution 12// on the target. 13// 14// This pass performs a strength reduction on array references inside loops that 15// have as one or more of their components the loop induction variable, it 16// rewrites expressions to take advantage of scaled-index addressing modes 17// available on the target, and it performs a variety of other optimizations 18// related to loop induction variables. 19// 20// Terminology note: this code has a lot of handling for "post-increment" or 21// "post-inc" users. This is not talking about post-increment addressing modes; 22// it is instead talking about code like this: 23// 24// %i = phi [ 0, %entry ], [ %i.next, %latch ] 25// ... 26// %i.next = add %i, 1 27// %c = icmp eq %i.next, %n 28// 29// The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however 30// it's useful to think about these as the same register, with some uses using 31// the value of the register before the add and some using // it after. In this 32// example, the icmp is a post-increment user, since it uses %i.next, which is 33// the value of the induction variable after the increment. The other common 34// case of post-increment users is users outside the loop. 35// 36// TODO: More sophistication in the way Formulae are generated and filtered. 37// 38// TODO: Handle multiple loops at a time. 39// 40// TODO: Should the addressing mode BaseGV be changed to a ConstantExpr instead 41// of a GlobalValue? 42// 43// TODO: When truncation is free, truncate ICmp users' operands to make it a 44// smaller encoding (on x86 at least). 45// 46// TODO: When a negated register is used by an add (such as in a list of 47// multiple base registers, or as the increment expression in an addrec), 48// we may not actually need both reg and (-1 * reg) in registers; the 49// negation can be implemented by using a sub instead of an add. The 50// lack of support for taking this into consideration when making 51// register pressure decisions is partly worked around by the "Special" 52// use kind. 53// 54//===----------------------------------------------------------------------===// 55 56#define DEBUG_TYPE "loop-reduce" 57#include "llvm/Transforms/Scalar.h" 58#include "llvm/ADT/DenseSet.h" 59#include "llvm/ADT/Hashing.h" 60#include "llvm/ADT/STLExtras.h" 61#include "llvm/ADT/SetVector.h" 62#include "llvm/ADT/SmallBitVector.h" 63#include "llvm/Analysis/IVUsers.h" 64#include "llvm/Analysis/LoopPass.h" 65#include "llvm/Analysis/ScalarEvolutionExpander.h" 66#include "llvm/Analysis/TargetTransformInfo.h" 67#include "llvm/IR/Constants.h" 68#include "llvm/IR/DerivedTypes.h" 69#include "llvm/IR/Dominators.h" 70#include "llvm/IR/Instructions.h" 71#include "llvm/IR/IntrinsicInst.h" 72#include "llvm/IR/ValueHandle.h" 73#include "llvm/Support/CommandLine.h" 74#include "llvm/Support/Debug.h" 75#include "llvm/Support/raw_ostream.h" 76#include "llvm/Transforms/Utils/BasicBlockUtils.h" 77#include "llvm/Transforms/Utils/Local.h" 78#include <algorithm> 79using namespace llvm; 80 81/// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for 82/// bail out. This threshold is far beyond the number of users that LSR can 83/// conceivably solve, so it should not affect generated code, but catches the 84/// worst cases before LSR burns too much compile time and stack space. 85static const unsigned MaxIVUsers = 200; 86 87// Temporary flag to cleanup congruent phis after LSR phi expansion. 88// It's currently disabled until we can determine whether it's truly useful or 89// not. The flag should be removed after the v3.0 release. 90// This is now needed for ivchains. 91static cl::opt<bool> EnablePhiElim( 92 "enable-lsr-phielim", cl::Hidden, cl::init(true), 93 cl::desc("Enable LSR phi elimination")); 94 95#ifndef NDEBUG 96// Stress test IV chain generation. 97static cl::opt<bool> StressIVChain( 98 "stress-ivchain", cl::Hidden, cl::init(false), 99 cl::desc("Stress test LSR IV chains")); 100#else 101static bool StressIVChain = false; 102#endif 103 104namespace { 105 106/// RegSortData - This class holds data which is used to order reuse candidates. 107class RegSortData { 108public: 109 /// UsedByIndices - This represents the set of LSRUse indices which reference 110 /// a particular register. 111 SmallBitVector UsedByIndices; 112 113 RegSortData() {} 114 115 void print(raw_ostream &OS) const; 116 void dump() const; 117}; 118 119} 120 121void RegSortData::print(raw_ostream &OS) const { 122 OS << "[NumUses=" << UsedByIndices.count() << ']'; 123} 124 125#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 126void RegSortData::dump() const { 127 print(errs()); errs() << '\n'; 128} 129#endif 130 131namespace { 132 133/// RegUseTracker - Map register candidates to information about how they are 134/// used. 135class RegUseTracker { 136 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy; 137 138 RegUsesTy RegUsesMap; 139 SmallVector<const SCEV *, 16> RegSequence; 140 141public: 142 void CountRegister(const SCEV *Reg, size_t LUIdx); 143 void DropRegister(const SCEV *Reg, size_t LUIdx); 144 void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx); 145 146 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const; 147 148 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const; 149 150 void clear(); 151 152 typedef SmallVectorImpl<const SCEV *>::iterator iterator; 153 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator; 154 iterator begin() { return RegSequence.begin(); } 155 iterator end() { return RegSequence.end(); } 156 const_iterator begin() const { return RegSequence.begin(); } 157 const_iterator end() const { return RegSequence.end(); } 158}; 159 160} 161 162void 163RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) { 164 std::pair<RegUsesTy::iterator, bool> Pair = 165 RegUsesMap.insert(std::make_pair(Reg, RegSortData())); 166 RegSortData &RSD = Pair.first->second; 167 if (Pair.second) 168 RegSequence.push_back(Reg); 169 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1)); 170 RSD.UsedByIndices.set(LUIdx); 171} 172 173void 174RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) { 175 RegUsesTy::iterator It = RegUsesMap.find(Reg); 176 assert(It != RegUsesMap.end()); 177 RegSortData &RSD = It->second; 178 assert(RSD.UsedByIndices.size() > LUIdx); 179 RSD.UsedByIndices.reset(LUIdx); 180} 181 182void 183RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) { 184 assert(LUIdx <= LastLUIdx); 185 186 // Update RegUses. The data structure is not optimized for this purpose; 187 // we must iterate through it and update each of the bit vectors. 188 for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end(); 189 I != E; ++I) { 190 SmallBitVector &UsedByIndices = I->second.UsedByIndices; 191 if (LUIdx < UsedByIndices.size()) 192 UsedByIndices[LUIdx] = 193 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0; 194 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx)); 195 } 196} 197 198bool 199RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const { 200 RegUsesTy::const_iterator I = RegUsesMap.find(Reg); 201 if (I == RegUsesMap.end()) 202 return false; 203 const SmallBitVector &UsedByIndices = I->second.UsedByIndices; 204 int i = UsedByIndices.find_first(); 205 if (i == -1) return false; 206 if ((size_t)i != LUIdx) return true; 207 return UsedByIndices.find_next(i) != -1; 208} 209 210const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const { 211 RegUsesTy::const_iterator I = RegUsesMap.find(Reg); 212 assert(I != RegUsesMap.end() && "Unknown register!"); 213 return I->second.UsedByIndices; 214} 215 216void RegUseTracker::clear() { 217 RegUsesMap.clear(); 218 RegSequence.clear(); 219} 220 221namespace { 222 223/// Formula - This class holds information that describes a formula for 224/// computing satisfying a use. It may include broken-out immediates and scaled 225/// registers. 226struct Formula { 227 /// Global base address used for complex addressing. 228 GlobalValue *BaseGV; 229 230 /// Base offset for complex addressing. 231 int64_t BaseOffset; 232 233 /// Whether any complex addressing has a base register. 234 bool HasBaseReg; 235 236 /// The scale of any complex addressing. 237 int64_t Scale; 238 239 /// BaseRegs - The list of "base" registers for this use. When this is 240 /// non-empty, 241 SmallVector<const SCEV *, 4> BaseRegs; 242 243 /// ScaledReg - The 'scaled' register for this use. This should be non-null 244 /// when Scale is not zero. 245 const SCEV *ScaledReg; 246 247 /// UnfoldedOffset - An additional constant offset which added near the 248 /// use. This requires a temporary register, but the offset itself can 249 /// live in an add immediate field rather than a register. 250 int64_t UnfoldedOffset; 251 252 Formula() 253 : BaseGV(0), BaseOffset(0), HasBaseReg(false), Scale(0), ScaledReg(0), 254 UnfoldedOffset(0) {} 255 256 void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE); 257 258 unsigned getNumRegs() const; 259 Type *getType() const; 260 261 void DeleteBaseReg(const SCEV *&S); 262 263 bool referencesReg(const SCEV *S) const; 264 bool hasRegsUsedByUsesOtherThan(size_t LUIdx, 265 const RegUseTracker &RegUses) const; 266 267 void print(raw_ostream &OS) const; 268 void dump() const; 269}; 270 271} 272 273/// DoInitialMatch - Recursion helper for InitialMatch. 274static void DoInitialMatch(const SCEV *S, Loop *L, 275 SmallVectorImpl<const SCEV *> &Good, 276 SmallVectorImpl<const SCEV *> &Bad, 277 ScalarEvolution &SE) { 278 // Collect expressions which properly dominate the loop header. 279 if (SE.properlyDominates(S, L->getHeader())) { 280 Good.push_back(S); 281 return; 282 } 283 284 // Look at add operands. 285 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 286 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 287 I != E; ++I) 288 DoInitialMatch(*I, L, Good, Bad, SE); 289 return; 290 } 291 292 // Look at addrec operands. 293 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) 294 if (!AR->getStart()->isZero()) { 295 DoInitialMatch(AR->getStart(), L, Good, Bad, SE); 296 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0), 297 AR->getStepRecurrence(SE), 298 // FIXME: AR->getNoWrapFlags() 299 AR->getLoop(), SCEV::FlagAnyWrap), 300 L, Good, Bad, SE); 301 return; 302 } 303 304 // Handle a multiplication by -1 (negation) if it didn't fold. 305 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) 306 if (Mul->getOperand(0)->isAllOnesValue()) { 307 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end()); 308 const SCEV *NewMul = SE.getMulExpr(Ops); 309 310 SmallVector<const SCEV *, 4> MyGood; 311 SmallVector<const SCEV *, 4> MyBad; 312 DoInitialMatch(NewMul, L, MyGood, MyBad, SE); 313 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue( 314 SE.getEffectiveSCEVType(NewMul->getType()))); 315 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(), 316 E = MyGood.end(); I != E; ++I) 317 Good.push_back(SE.getMulExpr(NegOne, *I)); 318 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(), 319 E = MyBad.end(); I != E; ++I) 320 Bad.push_back(SE.getMulExpr(NegOne, *I)); 321 return; 322 } 323 324 // Ok, we can't do anything interesting. Just stuff the whole thing into a 325 // register and hope for the best. 326 Bad.push_back(S); 327} 328 329/// InitialMatch - Incorporate loop-variant parts of S into this Formula, 330/// attempting to keep all loop-invariant and loop-computable values in a 331/// single base register. 332void Formula::InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) { 333 SmallVector<const SCEV *, 4> Good; 334 SmallVector<const SCEV *, 4> Bad; 335 DoInitialMatch(S, L, Good, Bad, SE); 336 if (!Good.empty()) { 337 const SCEV *Sum = SE.getAddExpr(Good); 338 if (!Sum->isZero()) 339 BaseRegs.push_back(Sum); 340 HasBaseReg = true; 341 } 342 if (!Bad.empty()) { 343 const SCEV *Sum = SE.getAddExpr(Bad); 344 if (!Sum->isZero()) 345 BaseRegs.push_back(Sum); 346 HasBaseReg = true; 347 } 348} 349 350/// getNumRegs - Return the total number of register operands used by this 351/// formula. This does not include register uses implied by non-constant 352/// addrec strides. 353unsigned Formula::getNumRegs() const { 354 return !!ScaledReg + BaseRegs.size(); 355} 356 357/// getType - Return the type of this formula, if it has one, or null 358/// otherwise. This type is meaningless except for the bit size. 359Type *Formula::getType() const { 360 return !BaseRegs.empty() ? BaseRegs.front()->getType() : 361 ScaledReg ? ScaledReg->getType() : 362 BaseGV ? BaseGV->getType() : 363 0; 364} 365 366/// DeleteBaseReg - Delete the given base reg from the BaseRegs list. 367void Formula::DeleteBaseReg(const SCEV *&S) { 368 if (&S != &BaseRegs.back()) 369 std::swap(S, BaseRegs.back()); 370 BaseRegs.pop_back(); 371} 372 373/// referencesReg - Test if this formula references the given register. 374bool Formula::referencesReg(const SCEV *S) const { 375 return S == ScaledReg || 376 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end(); 377} 378 379/// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers 380/// which are used by uses other than the use with the given index. 381bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx, 382 const RegUseTracker &RegUses) const { 383 if (ScaledReg) 384 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx)) 385 return true; 386 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(), 387 E = BaseRegs.end(); I != E; ++I) 388 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx)) 389 return true; 390 return false; 391} 392 393void Formula::print(raw_ostream &OS) const { 394 bool First = true; 395 if (BaseGV) { 396 if (!First) OS << " + "; else First = false; 397 BaseGV->printAsOperand(OS, /*PrintType=*/false); 398 } 399 if (BaseOffset != 0) { 400 if (!First) OS << " + "; else First = false; 401 OS << BaseOffset; 402 } 403 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(), 404 E = BaseRegs.end(); I != E; ++I) { 405 if (!First) OS << " + "; else First = false; 406 OS << "reg(" << **I << ')'; 407 } 408 if (HasBaseReg && BaseRegs.empty()) { 409 if (!First) OS << " + "; else First = false; 410 OS << "**error: HasBaseReg**"; 411 } else if (!HasBaseReg && !BaseRegs.empty()) { 412 if (!First) OS << " + "; else First = false; 413 OS << "**error: !HasBaseReg**"; 414 } 415 if (Scale != 0) { 416 if (!First) OS << " + "; else First = false; 417 OS << Scale << "*reg("; 418 if (ScaledReg) 419 OS << *ScaledReg; 420 else 421 OS << "<unknown>"; 422 OS << ')'; 423 } 424 if (UnfoldedOffset != 0) { 425 if (!First) OS << " + "; 426 OS << "imm(" << UnfoldedOffset << ')'; 427 } 428} 429 430#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 431void Formula::dump() const { 432 print(errs()); errs() << '\n'; 433} 434#endif 435 436/// isAddRecSExtable - Return true if the given addrec can be sign-extended 437/// without changing its value. 438static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) { 439 Type *WideTy = 440 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1); 441 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy)); 442} 443 444/// isAddSExtable - Return true if the given add can be sign-extended 445/// without changing its value. 446static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) { 447 Type *WideTy = 448 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1); 449 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy)); 450} 451 452/// isMulSExtable - Return true if the given mul can be sign-extended 453/// without changing its value. 454static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) { 455 Type *WideTy = 456 IntegerType::get(SE.getContext(), 457 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands()); 458 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy)); 459} 460 461/// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined 462/// and if the remainder is known to be zero, or null otherwise. If 463/// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified 464/// to Y, ignoring that the multiplication may overflow, which is useful when 465/// the result will be used in a context where the most significant bits are 466/// ignored. 467static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS, 468 ScalarEvolution &SE, 469 bool IgnoreSignificantBits = false) { 470 // Handle the trivial case, which works for any SCEV type. 471 if (LHS == RHS) 472 return SE.getConstant(LHS->getType(), 1); 473 474 // Handle a few RHS special cases. 475 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS); 476 if (RC) { 477 const APInt &RA = RC->getValue()->getValue(); 478 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do 479 // some folding. 480 if (RA.isAllOnesValue()) 481 return SE.getMulExpr(LHS, RC); 482 // Handle x /s 1 as x. 483 if (RA == 1) 484 return LHS; 485 } 486 487 // Check for a division of a constant by a constant. 488 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) { 489 if (!RC) 490 return 0; 491 const APInt &LA = C->getValue()->getValue(); 492 const APInt &RA = RC->getValue()->getValue(); 493 if (LA.srem(RA) != 0) 494 return 0; 495 return SE.getConstant(LA.sdiv(RA)); 496 } 497 498 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow. 499 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) { 500 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) { 501 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE, 502 IgnoreSignificantBits); 503 if (!Step) return 0; 504 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE, 505 IgnoreSignificantBits); 506 if (!Start) return 0; 507 // FlagNW is independent of the start value, step direction, and is 508 // preserved with smaller magnitude steps. 509 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW) 510 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap); 511 } 512 return 0; 513 } 514 515 // Distribute the sdiv over add operands, if the add doesn't overflow. 516 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) { 517 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) { 518 SmallVector<const SCEV *, 8> Ops; 519 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 520 I != E; ++I) { 521 const SCEV *Op = getExactSDiv(*I, RHS, SE, 522 IgnoreSignificantBits); 523 if (!Op) return 0; 524 Ops.push_back(Op); 525 } 526 return SE.getAddExpr(Ops); 527 } 528 return 0; 529 } 530 531 // Check for a multiply operand that we can pull RHS out of. 532 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) { 533 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) { 534 SmallVector<const SCEV *, 4> Ops; 535 bool Found = false; 536 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end(); 537 I != E; ++I) { 538 const SCEV *S = *I; 539 if (!Found) 540 if (const SCEV *Q = getExactSDiv(S, RHS, SE, 541 IgnoreSignificantBits)) { 542 S = Q; 543 Found = true; 544 } 545 Ops.push_back(S); 546 } 547 return Found ? SE.getMulExpr(Ops) : 0; 548 } 549 return 0; 550 } 551 552 // Otherwise we don't know. 553 return 0; 554} 555 556/// ExtractImmediate - If S involves the addition of a constant integer value, 557/// return that integer value, and mutate S to point to a new SCEV with that 558/// value excluded. 559static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) { 560 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) { 561 if (C->getValue()->getValue().getMinSignedBits() <= 64) { 562 S = SE.getConstant(C->getType(), 0); 563 return C->getValue()->getSExtValue(); 564 } 565 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 566 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); 567 int64_t Result = ExtractImmediate(NewOps.front(), SE); 568 if (Result != 0) 569 S = SE.getAddExpr(NewOps); 570 return Result; 571 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 572 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); 573 int64_t Result = ExtractImmediate(NewOps.front(), SE); 574 if (Result != 0) 575 S = SE.getAddRecExpr(NewOps, AR->getLoop(), 576 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW) 577 SCEV::FlagAnyWrap); 578 return Result; 579 } 580 return 0; 581} 582 583/// ExtractSymbol - If S involves the addition of a GlobalValue address, 584/// return that symbol, and mutate S to point to a new SCEV with that 585/// value excluded. 586static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) { 587 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { 588 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) { 589 S = SE.getConstant(GV->getType(), 0); 590 return GV; 591 } 592 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 593 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); 594 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE); 595 if (Result) 596 S = SE.getAddExpr(NewOps); 597 return Result; 598 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 599 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); 600 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE); 601 if (Result) 602 S = SE.getAddRecExpr(NewOps, AR->getLoop(), 603 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW) 604 SCEV::FlagAnyWrap); 605 return Result; 606 } 607 return 0; 608} 609 610/// isAddressUse - Returns true if the specified instruction is using the 611/// specified value as an address. 612static bool isAddressUse(Instruction *Inst, Value *OperandVal) { 613 bool isAddress = isa<LoadInst>(Inst); 614 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 615 if (SI->getOperand(1) == OperandVal) 616 isAddress = true; 617 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 618 // Addressing modes can also be folded into prefetches and a variety 619 // of intrinsics. 620 switch (II->getIntrinsicID()) { 621 default: break; 622 case Intrinsic::prefetch: 623 case Intrinsic::x86_sse_storeu_ps: 624 case Intrinsic::x86_sse2_storeu_pd: 625 case Intrinsic::x86_sse2_storeu_dq: 626 case Intrinsic::x86_sse2_storel_dq: 627 if (II->getArgOperand(0) == OperandVal) 628 isAddress = true; 629 break; 630 } 631 } 632 return isAddress; 633} 634 635/// getAccessType - Return the type of the memory being accessed. 636static Type *getAccessType(const Instruction *Inst) { 637 Type *AccessTy = Inst->getType(); 638 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) 639 AccessTy = SI->getOperand(0)->getType(); 640 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 641 // Addressing modes can also be folded into prefetches and a variety 642 // of intrinsics. 643 switch (II->getIntrinsicID()) { 644 default: break; 645 case Intrinsic::x86_sse_storeu_ps: 646 case Intrinsic::x86_sse2_storeu_pd: 647 case Intrinsic::x86_sse2_storeu_dq: 648 case Intrinsic::x86_sse2_storel_dq: 649 AccessTy = II->getArgOperand(0)->getType(); 650 break; 651 } 652 } 653 654 // All pointers have the same requirements, so canonicalize them to an 655 // arbitrary pointer type to minimize variation. 656 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy)) 657 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1), 658 PTy->getAddressSpace()); 659 660 return AccessTy; 661} 662 663/// isExistingPhi - Return true if this AddRec is already a phi in its loop. 664static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) { 665 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin(); 666 PHINode *PN = dyn_cast<PHINode>(I); ++I) { 667 if (SE.isSCEVable(PN->getType()) && 668 (SE.getEffectiveSCEVType(PN->getType()) == 669 SE.getEffectiveSCEVType(AR->getType())) && 670 SE.getSCEV(PN) == AR) 671 return true; 672 } 673 return false; 674} 675 676/// Check if expanding this expression is likely to incur significant cost. This 677/// is tricky because SCEV doesn't track which expressions are actually computed 678/// by the current IR. 679/// 680/// We currently allow expansion of IV increments that involve adds, 681/// multiplication by constants, and AddRecs from existing phis. 682/// 683/// TODO: Allow UDivExpr if we can find an existing IV increment that is an 684/// obvious multiple of the UDivExpr. 685static bool isHighCostExpansion(const SCEV *S, 686 SmallPtrSet<const SCEV*, 8> &Processed, 687 ScalarEvolution &SE) { 688 // Zero/One operand expressions 689 switch (S->getSCEVType()) { 690 case scUnknown: 691 case scConstant: 692 return false; 693 case scTruncate: 694 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(), 695 Processed, SE); 696 case scZeroExtend: 697 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(), 698 Processed, SE); 699 case scSignExtend: 700 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(), 701 Processed, SE); 702 } 703 704 if (!Processed.insert(S)) 705 return false; 706 707 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 708 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 709 I != E; ++I) { 710 if (isHighCostExpansion(*I, Processed, SE)) 711 return true; 712 } 713 return false; 714 } 715 716 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) { 717 if (Mul->getNumOperands() == 2) { 718 // Multiplication by a constant is ok 719 if (isa<SCEVConstant>(Mul->getOperand(0))) 720 return isHighCostExpansion(Mul->getOperand(1), Processed, SE); 721 722 // If we have the value of one operand, check if an existing 723 // multiplication already generates this expression. 724 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) { 725 Value *UVal = U->getValue(); 726 for (User *UR : UVal->users()) { 727 // If U is a constant, it may be used by a ConstantExpr. 728 Instruction *UI = dyn_cast<Instruction>(UR); 729 if (UI && UI->getOpcode() == Instruction::Mul && 730 SE.isSCEVable(UI->getType())) { 731 return SE.getSCEV(UI) == Mul; 732 } 733 } 734 } 735 } 736 } 737 738 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 739 if (isExistingPhi(AR, SE)) 740 return false; 741 } 742 743 // Fow now, consider any other type of expression (div/mul/min/max) high cost. 744 return true; 745} 746 747/// DeleteTriviallyDeadInstructions - If any of the instructions is the 748/// specified set are trivially dead, delete them and see if this makes any of 749/// their operands subsequently dead. 750static bool 751DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) { 752 bool Changed = false; 753 754 while (!DeadInsts.empty()) { 755 Value *V = DeadInsts.pop_back_val(); 756 Instruction *I = dyn_cast_or_null<Instruction>(V); 757 758 if (I == 0 || !isInstructionTriviallyDead(I)) 759 continue; 760 761 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 762 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 763 *OI = 0; 764 if (U->use_empty()) 765 DeadInsts.push_back(U); 766 } 767 768 I->eraseFromParent(); 769 Changed = true; 770 } 771 772 return Changed; 773} 774 775namespace { 776class LSRUse; 777} 778// Check if it is legal to fold 2 base registers. 779static bool isLegal2RegAMUse(const TargetTransformInfo &TTI, const LSRUse &LU, 780 const Formula &F); 781// Get the cost of the scaling factor used in F for LU. 782static unsigned getScalingFactorCost(const TargetTransformInfo &TTI, 783 const LSRUse &LU, const Formula &F); 784 785namespace { 786 787/// Cost - This class is used to measure and compare candidate formulae. 788class Cost { 789 /// TODO: Some of these could be merged. Also, a lexical ordering 790 /// isn't always optimal. 791 unsigned NumRegs; 792 unsigned AddRecCost; 793 unsigned NumIVMuls; 794 unsigned NumBaseAdds; 795 unsigned ImmCost; 796 unsigned SetupCost; 797 unsigned ScaleCost; 798 799public: 800 Cost() 801 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0), 802 SetupCost(0), ScaleCost(0) {} 803 804 bool operator<(const Cost &Other) const; 805 806 void Lose(); 807 808#ifndef NDEBUG 809 // Once any of the metrics loses, they must all remain losers. 810 bool isValid() { 811 return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds 812 | ImmCost | SetupCost | ScaleCost) != ~0u) 813 || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds 814 & ImmCost & SetupCost & ScaleCost) == ~0u); 815 } 816#endif 817 818 bool isLoser() { 819 assert(isValid() && "invalid cost"); 820 return NumRegs == ~0u; 821 } 822 823 void RateFormula(const TargetTransformInfo &TTI, 824 const Formula &F, 825 SmallPtrSet<const SCEV *, 16> &Regs, 826 const DenseSet<const SCEV *> &VisitedRegs, 827 const Loop *L, 828 const SmallVectorImpl<int64_t> &Offsets, 829 ScalarEvolution &SE, DominatorTree &DT, 830 const LSRUse &LU, 831 SmallPtrSet<const SCEV *, 16> *LoserRegs = 0); 832 833 void print(raw_ostream &OS) const; 834 void dump() const; 835 836private: 837 void RateRegister(const SCEV *Reg, 838 SmallPtrSet<const SCEV *, 16> &Regs, 839 const Loop *L, 840 ScalarEvolution &SE, DominatorTree &DT); 841 void RatePrimaryRegister(const SCEV *Reg, 842 SmallPtrSet<const SCEV *, 16> &Regs, 843 const Loop *L, 844 ScalarEvolution &SE, DominatorTree &DT, 845 SmallPtrSet<const SCEV *, 16> *LoserRegs); 846}; 847 848} 849 850/// RateRegister - Tally up interesting quantities from the given register. 851void Cost::RateRegister(const SCEV *Reg, 852 SmallPtrSet<const SCEV *, 16> &Regs, 853 const Loop *L, 854 ScalarEvolution &SE, DominatorTree &DT) { 855 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) { 856 // If this is an addrec for another loop, don't second-guess its addrec phi 857 // nodes. LSR isn't currently smart enough to reason about more than one 858 // loop at a time. LSR has already run on inner loops, will not run on outer 859 // loops, and cannot be expected to change sibling loops. 860 if (AR->getLoop() != L) { 861 // If the AddRec exists, consider it's register free and leave it alone. 862 if (isExistingPhi(AR, SE)) 863 return; 864 865 // Otherwise, do not consider this formula at all. 866 Lose(); 867 return; 868 } 869 AddRecCost += 1; /// TODO: This should be a function of the stride. 870 871 // Add the step value register, if it needs one. 872 // TODO: The non-affine case isn't precisely modeled here. 873 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) { 874 if (!Regs.count(AR->getOperand(1))) { 875 RateRegister(AR->getOperand(1), Regs, L, SE, DT); 876 if (isLoser()) 877 return; 878 } 879 } 880 } 881 ++NumRegs; 882 883 // Rough heuristic; favor registers which don't require extra setup 884 // instructions in the preheader. 885 if (!isa<SCEVUnknown>(Reg) && 886 !isa<SCEVConstant>(Reg) && 887 !(isa<SCEVAddRecExpr>(Reg) && 888 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) || 889 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart())))) 890 ++SetupCost; 891 892 NumIVMuls += isa<SCEVMulExpr>(Reg) && 893 SE.hasComputableLoopEvolution(Reg, L); 894} 895 896/// RatePrimaryRegister - Record this register in the set. If we haven't seen it 897/// before, rate it. Optional LoserRegs provides a way to declare any formula 898/// that refers to one of those regs an instant loser. 899void Cost::RatePrimaryRegister(const SCEV *Reg, 900 SmallPtrSet<const SCEV *, 16> &Regs, 901 const Loop *L, 902 ScalarEvolution &SE, DominatorTree &DT, 903 SmallPtrSet<const SCEV *, 16> *LoserRegs) { 904 if (LoserRegs && LoserRegs->count(Reg)) { 905 Lose(); 906 return; 907 } 908 if (Regs.insert(Reg)) { 909 RateRegister(Reg, Regs, L, SE, DT); 910 if (LoserRegs && isLoser()) 911 LoserRegs->insert(Reg); 912 } 913} 914 915void Cost::RateFormula(const TargetTransformInfo &TTI, 916 const Formula &F, 917 SmallPtrSet<const SCEV *, 16> &Regs, 918 const DenseSet<const SCEV *> &VisitedRegs, 919 const Loop *L, 920 const SmallVectorImpl<int64_t> &Offsets, 921 ScalarEvolution &SE, DominatorTree &DT, 922 const LSRUse &LU, 923 SmallPtrSet<const SCEV *, 16> *LoserRegs) { 924 // Tally up the registers. 925 if (const SCEV *ScaledReg = F.ScaledReg) { 926 if (VisitedRegs.count(ScaledReg)) { 927 Lose(); 928 return; 929 } 930 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs); 931 if (isLoser()) 932 return; 933 } 934 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), 935 E = F.BaseRegs.end(); I != E; ++I) { 936 const SCEV *BaseReg = *I; 937 if (VisitedRegs.count(BaseReg)) { 938 Lose(); 939 return; 940 } 941 RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs); 942 if (isLoser()) 943 return; 944 } 945 946 // Determine how many (unfolded) adds we'll need inside the loop. 947 size_t NumBaseParts = F.BaseRegs.size() + (F.UnfoldedOffset != 0); 948 if (NumBaseParts > 1) 949 // Do not count the base and a possible second register if the target 950 // allows to fold 2 registers. 951 NumBaseAdds += NumBaseParts - (1 + isLegal2RegAMUse(TTI, LU, F)); 952 953 // Accumulate non-free scaling amounts. 954 ScaleCost += getScalingFactorCost(TTI, LU, F); 955 956 // Tally up the non-zero immediates. 957 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(), 958 E = Offsets.end(); I != E; ++I) { 959 int64_t Offset = (uint64_t)*I + F.BaseOffset; 960 if (F.BaseGV) 961 ImmCost += 64; // Handle symbolic values conservatively. 962 // TODO: This should probably be the pointer size. 963 else if (Offset != 0) 964 ImmCost += APInt(64, Offset, true).getMinSignedBits(); 965 } 966 assert(isValid() && "invalid cost"); 967} 968 969/// Lose - Set this cost to a losing value. 970void Cost::Lose() { 971 NumRegs = ~0u; 972 AddRecCost = ~0u; 973 NumIVMuls = ~0u; 974 NumBaseAdds = ~0u; 975 ImmCost = ~0u; 976 SetupCost = ~0u; 977 ScaleCost = ~0u; 978} 979 980/// operator< - Choose the lower cost. 981bool Cost::operator<(const Cost &Other) const { 982 return std::tie(NumRegs, AddRecCost, NumIVMuls, NumBaseAdds, ScaleCost, 983 ImmCost, SetupCost) < 984 std::tie(Other.NumRegs, Other.AddRecCost, Other.NumIVMuls, 985 Other.NumBaseAdds, Other.ScaleCost, Other.ImmCost, 986 Other.SetupCost); 987} 988 989void Cost::print(raw_ostream &OS) const { 990 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s"); 991 if (AddRecCost != 0) 992 OS << ", with addrec cost " << AddRecCost; 993 if (NumIVMuls != 0) 994 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s"); 995 if (NumBaseAdds != 0) 996 OS << ", plus " << NumBaseAdds << " base add" 997 << (NumBaseAdds == 1 ? "" : "s"); 998 if (ScaleCost != 0) 999 OS << ", plus " << ScaleCost << " scale cost"; 1000 if (ImmCost != 0) 1001 OS << ", plus " << ImmCost << " imm cost"; 1002 if (SetupCost != 0) 1003 OS << ", plus " << SetupCost << " setup cost"; 1004} 1005 1006#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 1007void Cost::dump() const { 1008 print(errs()); errs() << '\n'; 1009} 1010#endif 1011 1012namespace { 1013 1014/// LSRFixup - An operand value in an instruction which is to be replaced 1015/// with some equivalent, possibly strength-reduced, replacement. 1016struct LSRFixup { 1017 /// UserInst - The instruction which will be updated. 1018 Instruction *UserInst; 1019 1020 /// OperandValToReplace - The operand of the instruction which will 1021 /// be replaced. The operand may be used more than once; every instance 1022 /// will be replaced. 1023 Value *OperandValToReplace; 1024 1025 /// PostIncLoops - If this user is to use the post-incremented value of an 1026 /// induction variable, this variable is non-null and holds the loop 1027 /// associated with the induction variable. 1028 PostIncLoopSet PostIncLoops; 1029 1030 /// LUIdx - The index of the LSRUse describing the expression which 1031 /// this fixup needs, minus an offset (below). 1032 size_t LUIdx; 1033 1034 /// Offset - A constant offset to be added to the LSRUse expression. 1035 /// This allows multiple fixups to share the same LSRUse with different 1036 /// offsets, for example in an unrolled loop. 1037 int64_t Offset; 1038 1039 bool isUseFullyOutsideLoop(const Loop *L) const; 1040 1041 LSRFixup(); 1042 1043 void print(raw_ostream &OS) const; 1044 void dump() const; 1045}; 1046 1047} 1048 1049LSRFixup::LSRFixup() 1050 : UserInst(0), OperandValToReplace(0), LUIdx(~size_t(0)), Offset(0) {} 1051 1052/// isUseFullyOutsideLoop - Test whether this fixup always uses its 1053/// value outside of the given loop. 1054bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const { 1055 // PHI nodes use their value in their incoming blocks. 1056 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) { 1057 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 1058 if (PN->getIncomingValue(i) == OperandValToReplace && 1059 L->contains(PN->getIncomingBlock(i))) 1060 return false; 1061 return true; 1062 } 1063 1064 return !L->contains(UserInst); 1065} 1066 1067void LSRFixup::print(raw_ostream &OS) const { 1068 OS << "UserInst="; 1069 // Store is common and interesting enough to be worth special-casing. 1070 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) { 1071 OS << "store "; 1072 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false); 1073 } else if (UserInst->getType()->isVoidTy()) 1074 OS << UserInst->getOpcodeName(); 1075 else 1076 UserInst->printAsOperand(OS, /*PrintType=*/false); 1077 1078 OS << ", OperandValToReplace="; 1079 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false); 1080 1081 for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(), 1082 E = PostIncLoops.end(); I != E; ++I) { 1083 OS << ", PostIncLoop="; 1084 (*I)->getHeader()->printAsOperand(OS, /*PrintType=*/false); 1085 } 1086 1087 if (LUIdx != ~size_t(0)) 1088 OS << ", LUIdx=" << LUIdx; 1089 1090 if (Offset != 0) 1091 OS << ", Offset=" << Offset; 1092} 1093 1094#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 1095void LSRFixup::dump() const { 1096 print(errs()); errs() << '\n'; 1097} 1098#endif 1099 1100namespace { 1101 1102/// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding 1103/// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*. 1104struct UniquifierDenseMapInfo { 1105 static SmallVector<const SCEV *, 4> getEmptyKey() { 1106 SmallVector<const SCEV *, 4> V; 1107 V.push_back(reinterpret_cast<const SCEV *>(-1)); 1108 return V; 1109 } 1110 1111 static SmallVector<const SCEV *, 4> getTombstoneKey() { 1112 SmallVector<const SCEV *, 4> V; 1113 V.push_back(reinterpret_cast<const SCEV *>(-2)); 1114 return V; 1115 } 1116 1117 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) { 1118 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end())); 1119 } 1120 1121 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS, 1122 const SmallVector<const SCEV *, 4> &RHS) { 1123 return LHS == RHS; 1124 } 1125}; 1126 1127/// LSRUse - This class holds the state that LSR keeps for each use in 1128/// IVUsers, as well as uses invented by LSR itself. It includes information 1129/// about what kinds of things can be folded into the user, information about 1130/// the user itself, and information about how the use may be satisfied. 1131/// TODO: Represent multiple users of the same expression in common? 1132class LSRUse { 1133 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier; 1134 1135public: 1136 /// KindType - An enum for a kind of use, indicating what types of 1137 /// scaled and immediate operands it might support. 1138 enum KindType { 1139 Basic, ///< A normal use, with no folding. 1140 Special, ///< A special case of basic, allowing -1 scales. 1141 Address, ///< An address use; folding according to TargetLowering 1142 ICmpZero ///< An equality icmp with both operands folded into one. 1143 // TODO: Add a generic icmp too? 1144 }; 1145 1146 typedef PointerIntPair<const SCEV *, 2, KindType> SCEVUseKindPair; 1147 1148 KindType Kind; 1149 Type *AccessTy; 1150 1151 SmallVector<int64_t, 8> Offsets; 1152 int64_t MinOffset; 1153 int64_t MaxOffset; 1154 1155 /// AllFixupsOutsideLoop - This records whether all of the fixups using this 1156 /// LSRUse are outside of the loop, in which case some special-case heuristics 1157 /// may be used. 1158 bool AllFixupsOutsideLoop; 1159 1160 /// RigidFormula is set to true to guarantee that this use will be associated 1161 /// with a single formula--the one that initially matched. Some SCEV 1162 /// expressions cannot be expanded. This allows LSR to consider the registers 1163 /// used by those expressions without the need to expand them later after 1164 /// changing the formula. 1165 bool RigidFormula; 1166 1167 /// WidestFixupType - This records the widest use type for any fixup using 1168 /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different 1169 /// max fixup widths to be equivalent, because the narrower one may be relying 1170 /// on the implicit truncation to truncate away bogus bits. 1171 Type *WidestFixupType; 1172 1173 /// Formulae - A list of ways to build a value that can satisfy this user. 1174 /// After the list is populated, one of these is selected heuristically and 1175 /// used to formulate a replacement for OperandValToReplace in UserInst. 1176 SmallVector<Formula, 12> Formulae; 1177 1178 /// Regs - The set of register candidates used by all formulae in this LSRUse. 1179 SmallPtrSet<const SCEV *, 4> Regs; 1180 1181 LSRUse(KindType K, Type *T) : Kind(K), AccessTy(T), 1182 MinOffset(INT64_MAX), 1183 MaxOffset(INT64_MIN), 1184 AllFixupsOutsideLoop(true), 1185 RigidFormula(false), 1186 WidestFixupType(0) {} 1187 1188 bool HasFormulaWithSameRegs(const Formula &F) const; 1189 bool InsertFormula(const Formula &F); 1190 void DeleteFormula(Formula &F); 1191 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses); 1192 1193 void print(raw_ostream &OS) const; 1194 void dump() const; 1195}; 1196 1197} 1198 1199/// HasFormula - Test whether this use as a formula which has the same 1200/// registers as the given formula. 1201bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const { 1202 SmallVector<const SCEV *, 4> Key = F.BaseRegs; 1203 if (F.ScaledReg) Key.push_back(F.ScaledReg); 1204 // Unstable sort by host order ok, because this is only used for uniquifying. 1205 std::sort(Key.begin(), Key.end()); 1206 return Uniquifier.count(Key); 1207} 1208 1209/// InsertFormula - If the given formula has not yet been inserted, add it to 1210/// the list, and return true. Return false otherwise. 1211bool LSRUse::InsertFormula(const Formula &F) { 1212 if (!Formulae.empty() && RigidFormula) 1213 return false; 1214 1215 SmallVector<const SCEV *, 4> Key = F.BaseRegs; 1216 if (F.ScaledReg) Key.push_back(F.ScaledReg); 1217 // Unstable sort by host order ok, because this is only used for uniquifying. 1218 std::sort(Key.begin(), Key.end()); 1219 1220 if (!Uniquifier.insert(Key).second) 1221 return false; 1222 1223 // Using a register to hold the value of 0 is not profitable. 1224 assert((!F.ScaledReg || !F.ScaledReg->isZero()) && 1225 "Zero allocated in a scaled register!"); 1226#ifndef NDEBUG 1227 for (SmallVectorImpl<const SCEV *>::const_iterator I = 1228 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) 1229 assert(!(*I)->isZero() && "Zero allocated in a base register!"); 1230#endif 1231 1232 // Add the formula to the list. 1233 Formulae.push_back(F); 1234 1235 // Record registers now being used by this use. 1236 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); 1237 1238 return true; 1239} 1240 1241/// DeleteFormula - Remove the given formula from this use's list. 1242void LSRUse::DeleteFormula(Formula &F) { 1243 if (&F != &Formulae.back()) 1244 std::swap(F, Formulae.back()); 1245 Formulae.pop_back(); 1246} 1247 1248/// RecomputeRegs - Recompute the Regs field, and update RegUses. 1249void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) { 1250 // Now that we've filtered out some formulae, recompute the Regs set. 1251 SmallPtrSet<const SCEV *, 4> OldRegs = Regs; 1252 Regs.clear(); 1253 for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(), 1254 E = Formulae.end(); I != E; ++I) { 1255 const Formula &F = *I; 1256 if (F.ScaledReg) Regs.insert(F.ScaledReg); 1257 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); 1258 } 1259 1260 // Update the RegTracker. 1261 for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(), 1262 E = OldRegs.end(); I != E; ++I) 1263 if (!Regs.count(*I)) 1264 RegUses.DropRegister(*I, LUIdx); 1265} 1266 1267void LSRUse::print(raw_ostream &OS) const { 1268 OS << "LSR Use: Kind="; 1269 switch (Kind) { 1270 case Basic: OS << "Basic"; break; 1271 case Special: OS << "Special"; break; 1272 case ICmpZero: OS << "ICmpZero"; break; 1273 case Address: 1274 OS << "Address of "; 1275 if (AccessTy->isPointerTy()) 1276 OS << "pointer"; // the full pointer type could be really verbose 1277 else 1278 OS << *AccessTy; 1279 } 1280 1281 OS << ", Offsets={"; 1282 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(), 1283 E = Offsets.end(); I != E; ++I) { 1284 OS << *I; 1285 if (std::next(I) != E) 1286 OS << ','; 1287 } 1288 OS << '}'; 1289 1290 if (AllFixupsOutsideLoop) 1291 OS << ", all-fixups-outside-loop"; 1292 1293 if (WidestFixupType) 1294 OS << ", widest fixup type: " << *WidestFixupType; 1295} 1296 1297#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 1298void LSRUse::dump() const { 1299 print(errs()); errs() << '\n'; 1300} 1301#endif 1302 1303/// isLegalUse - Test whether the use described by AM is "legal", meaning it can 1304/// be completely folded into the user instruction at isel time. This includes 1305/// address-mode folding and special icmp tricks. 1306static bool isLegalUse(const TargetTransformInfo &TTI, LSRUse::KindType Kind, 1307 Type *AccessTy, GlobalValue *BaseGV, int64_t BaseOffset, 1308 bool HasBaseReg, int64_t Scale) { 1309 switch (Kind) { 1310 case LSRUse::Address: 1311 return TTI.isLegalAddressingMode(AccessTy, BaseGV, BaseOffset, HasBaseReg, Scale); 1312 1313 // Otherwise, just guess that reg+reg addressing is legal. 1314 //return ; 1315 1316 case LSRUse::ICmpZero: 1317 // There's not even a target hook for querying whether it would be legal to 1318 // fold a GV into an ICmp. 1319 if (BaseGV) 1320 return false; 1321 1322 // ICmp only has two operands; don't allow more than two non-trivial parts. 1323 if (Scale != 0 && HasBaseReg && BaseOffset != 0) 1324 return false; 1325 1326 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by 1327 // putting the scaled register in the other operand of the icmp. 1328 if (Scale != 0 && Scale != -1) 1329 return false; 1330 1331 // If we have low-level target information, ask the target if it can fold an 1332 // integer immediate on an icmp. 1333 if (BaseOffset != 0) { 1334 // We have one of: 1335 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset 1336 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset 1337 // Offs is the ICmp immediate. 1338 if (Scale == 0) 1339 // The cast does the right thing with INT64_MIN. 1340 BaseOffset = -(uint64_t)BaseOffset; 1341 return TTI.isLegalICmpImmediate(BaseOffset); 1342 } 1343 1344 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg 1345 return true; 1346 1347 case LSRUse::Basic: 1348 // Only handle single-register values. 1349 return !BaseGV && Scale == 0 && BaseOffset == 0; 1350 1351 case LSRUse::Special: 1352 // Special case Basic to handle -1 scales. 1353 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0; 1354 } 1355 1356 llvm_unreachable("Invalid LSRUse Kind!"); 1357} 1358 1359static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset, 1360 int64_t MaxOffset, LSRUse::KindType Kind, Type *AccessTy, 1361 GlobalValue *BaseGV, int64_t BaseOffset, bool HasBaseReg, 1362 int64_t Scale) { 1363 // Check for overflow. 1364 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) != 1365 (MinOffset > 0)) 1366 return false; 1367 MinOffset = (uint64_t)BaseOffset + MinOffset; 1368 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) != 1369 (MaxOffset > 0)) 1370 return false; 1371 MaxOffset = (uint64_t)BaseOffset + MaxOffset; 1372 1373 return isLegalUse(TTI, Kind, AccessTy, BaseGV, MinOffset, HasBaseReg, 1374 Scale) && 1375 isLegalUse(TTI, Kind, AccessTy, BaseGV, MaxOffset, HasBaseReg, Scale); 1376} 1377 1378static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset, 1379 int64_t MaxOffset, LSRUse::KindType Kind, Type *AccessTy, 1380 const Formula &F) { 1381 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV, 1382 F.BaseOffset, F.HasBaseReg, F.Scale); 1383} 1384 1385static bool isLegal2RegAMUse(const TargetTransformInfo &TTI, const LSRUse &LU, 1386 const Formula &F) { 1387 // If F is used as an Addressing Mode, it may fold one Base plus one 1388 // scaled register. If the scaled register is nil, do as if another 1389 // element of the base regs is a 1-scaled register. 1390 // This is possible if BaseRegs has at least 2 registers. 1391 1392 // If this is not an address calculation, this is not an addressing mode 1393 // use. 1394 if (LU.Kind != LSRUse::Address) 1395 return false; 1396 1397 // F is already scaled. 1398 if (F.Scale != 0) 1399 return false; 1400 1401 // We need to keep one register for the base and one to scale. 1402 if (F.BaseRegs.size() < 2) 1403 return false; 1404 1405 return isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, 1406 F.BaseGV, F.BaseOffset, F.HasBaseReg, 1); 1407 } 1408 1409static unsigned getScalingFactorCost(const TargetTransformInfo &TTI, 1410 const LSRUse &LU, const Formula &F) { 1411 if (!F.Scale) 1412 return 0; 1413 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, 1414 LU.AccessTy, F) && "Illegal formula in use."); 1415 1416 switch (LU.Kind) { 1417 case LSRUse::Address: { 1418 // Check the scaling factor cost with both the min and max offsets. 1419 int ScaleCostMinOffset = 1420 TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV, 1421 F.BaseOffset + LU.MinOffset, 1422 F.HasBaseReg, F.Scale); 1423 int ScaleCostMaxOffset = 1424 TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV, 1425 F.BaseOffset + LU.MaxOffset, 1426 F.HasBaseReg, F.Scale); 1427 1428 assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && 1429 "Legal addressing mode has an illegal cost!"); 1430 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset); 1431 } 1432 case LSRUse::ICmpZero: 1433 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg. 1434 // Therefore, return 0 in case F.Scale == -1. 1435 return F.Scale != -1; 1436 1437 case LSRUse::Basic: 1438 case LSRUse::Special: 1439 return 0; 1440 } 1441 1442 llvm_unreachable("Invalid LSRUse Kind!"); 1443} 1444 1445static bool isAlwaysFoldable(const TargetTransformInfo &TTI, 1446 LSRUse::KindType Kind, Type *AccessTy, 1447 GlobalValue *BaseGV, int64_t BaseOffset, 1448 bool HasBaseReg) { 1449 // Fast-path: zero is always foldable. 1450 if (BaseOffset == 0 && !BaseGV) return true; 1451 1452 // Conservatively, create an address with an immediate and a 1453 // base and a scale. 1454 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1; 1455 1456 // Canonicalize a scale of 1 to a base register if the formula doesn't 1457 // already have a base register. 1458 if (!HasBaseReg && Scale == 1) { 1459 Scale = 0; 1460 HasBaseReg = true; 1461 } 1462 1463 return isLegalUse(TTI, Kind, AccessTy, BaseGV, BaseOffset, HasBaseReg, Scale); 1464} 1465 1466static bool isAlwaysFoldable(const TargetTransformInfo &TTI, 1467 ScalarEvolution &SE, int64_t MinOffset, 1468 int64_t MaxOffset, LSRUse::KindType Kind, 1469 Type *AccessTy, const SCEV *S, bool HasBaseReg) { 1470 // Fast-path: zero is always foldable. 1471 if (S->isZero()) return true; 1472 1473 // Conservatively, create an address with an immediate and a 1474 // base and a scale. 1475 int64_t BaseOffset = ExtractImmediate(S, SE); 1476 GlobalValue *BaseGV = ExtractSymbol(S, SE); 1477 1478 // If there's anything else involved, it's not foldable. 1479 if (!S->isZero()) return false; 1480 1481 // Fast-path: zero is always foldable. 1482 if (BaseOffset == 0 && !BaseGV) return true; 1483 1484 // Conservatively, create an address with an immediate and a 1485 // base and a scale. 1486 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1; 1487 1488 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV, 1489 BaseOffset, HasBaseReg, Scale); 1490} 1491 1492namespace { 1493 1494/// IVInc - An individual increment in a Chain of IV increments. 1495/// Relate an IV user to an expression that computes the IV it uses from the IV 1496/// used by the previous link in the Chain. 1497/// 1498/// For the head of a chain, IncExpr holds the absolute SCEV expression for the 1499/// original IVOperand. The head of the chain's IVOperand is only valid during 1500/// chain collection, before LSR replaces IV users. During chain generation, 1501/// IncExpr can be used to find the new IVOperand that computes the same 1502/// expression. 1503struct IVInc { 1504 Instruction *UserInst; 1505 Value* IVOperand; 1506 const SCEV *IncExpr; 1507 1508 IVInc(Instruction *U, Value *O, const SCEV *E): 1509 UserInst(U), IVOperand(O), IncExpr(E) {} 1510}; 1511 1512// IVChain - The list of IV increments in program order. 1513// We typically add the head of a chain without finding subsequent links. 1514struct IVChain { 1515 SmallVector<IVInc,1> Incs; 1516 const SCEV *ExprBase; 1517 1518 IVChain() : ExprBase(0) {} 1519 1520 IVChain(const IVInc &Head, const SCEV *Base) 1521 : Incs(1, Head), ExprBase(Base) {} 1522 1523 typedef SmallVectorImpl<IVInc>::const_iterator const_iterator; 1524 1525 // begin - return the first increment in the chain. 1526 const_iterator begin() const { 1527 assert(!Incs.empty()); 1528 return std::next(Incs.begin()); 1529 } 1530 const_iterator end() const { 1531 return Incs.end(); 1532 } 1533 1534 // hasIncs - Returns true if this chain contains any increments. 1535 bool hasIncs() const { return Incs.size() >= 2; } 1536 1537 // add - Add an IVInc to the end of this chain. 1538 void add(const IVInc &X) { Incs.push_back(X); } 1539 1540 // tailUserInst - Returns the last UserInst in the chain. 1541 Instruction *tailUserInst() const { return Incs.back().UserInst; } 1542 1543 // isProfitableIncrement - Returns true if IncExpr can be profitably added to 1544 // this chain. 1545 bool isProfitableIncrement(const SCEV *OperExpr, 1546 const SCEV *IncExpr, 1547 ScalarEvolution&); 1548}; 1549 1550/// ChainUsers - Helper for CollectChains to track multiple IV increment uses. 1551/// Distinguish between FarUsers that definitely cross IV increments and 1552/// NearUsers that may be used between IV increments. 1553struct ChainUsers { 1554 SmallPtrSet<Instruction*, 4> FarUsers; 1555 SmallPtrSet<Instruction*, 4> NearUsers; 1556}; 1557 1558/// LSRInstance - This class holds state for the main loop strength reduction 1559/// logic. 1560class LSRInstance { 1561 IVUsers &IU; 1562 ScalarEvolution &SE; 1563 DominatorTree &DT; 1564 LoopInfo &LI; 1565 const TargetTransformInfo &TTI; 1566 Loop *const L; 1567 bool Changed; 1568 1569 /// IVIncInsertPos - This is the insert position that the current loop's 1570 /// induction variable increment should be placed. In simple loops, this is 1571 /// the latch block's terminator. But in more complicated cases, this is a 1572 /// position which will dominate all the in-loop post-increment users. 1573 Instruction *IVIncInsertPos; 1574 1575 /// Factors - Interesting factors between use strides. 1576 SmallSetVector<int64_t, 8> Factors; 1577 1578 /// Types - Interesting use types, to facilitate truncation reuse. 1579 SmallSetVector<Type *, 4> Types; 1580 1581 /// Fixups - The list of operands which are to be replaced. 1582 SmallVector<LSRFixup, 16> Fixups; 1583 1584 /// Uses - The list of interesting uses. 1585 SmallVector<LSRUse, 16> Uses; 1586 1587 /// RegUses - Track which uses use which register candidates. 1588 RegUseTracker RegUses; 1589 1590 // Limit the number of chains to avoid quadratic behavior. We don't expect to 1591 // have more than a few IV increment chains in a loop. Missing a Chain falls 1592 // back to normal LSR behavior for those uses. 1593 static const unsigned MaxChains = 8; 1594 1595 /// IVChainVec - IV users can form a chain of IV increments. 1596 SmallVector<IVChain, MaxChains> IVChainVec; 1597 1598 /// IVIncSet - IV users that belong to profitable IVChains. 1599 SmallPtrSet<Use*, MaxChains> IVIncSet; 1600 1601 void OptimizeShadowIV(); 1602 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse); 1603 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse); 1604 void OptimizeLoopTermCond(); 1605 1606 void ChainInstruction(Instruction *UserInst, Instruction *IVOper, 1607 SmallVectorImpl<ChainUsers> &ChainUsersVec); 1608 void FinalizeChain(IVChain &Chain); 1609 void CollectChains(); 1610 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter, 1611 SmallVectorImpl<WeakVH> &DeadInsts); 1612 1613 void CollectInterestingTypesAndFactors(); 1614 void CollectFixupsAndInitialFormulae(); 1615 1616 LSRFixup &getNewFixup() { 1617 Fixups.push_back(LSRFixup()); 1618 return Fixups.back(); 1619 } 1620 1621 // Support for sharing of LSRUses between LSRFixups. 1622 typedef DenseMap<LSRUse::SCEVUseKindPair, size_t> UseMapTy; 1623 UseMapTy UseMap; 1624 1625 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg, 1626 LSRUse::KindType Kind, Type *AccessTy); 1627 1628 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, 1629 LSRUse::KindType Kind, 1630 Type *AccessTy); 1631 1632 void DeleteUse(LSRUse &LU, size_t LUIdx); 1633 1634 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU); 1635 1636 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); 1637 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); 1638 void CountRegisters(const Formula &F, size_t LUIdx); 1639 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F); 1640 1641 void CollectLoopInvariantFixupsAndFormulae(); 1642 1643 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base, 1644 unsigned Depth = 0); 1645 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base); 1646 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); 1647 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); 1648 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base); 1649 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base); 1650 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base); 1651 void GenerateCrossUseConstantOffsets(); 1652 void GenerateAllReuseFormulae(); 1653 1654 void FilterOutUndesirableDedicatedRegisters(); 1655 1656 size_t EstimateSearchSpaceComplexity() const; 1657 void NarrowSearchSpaceByDetectingSupersets(); 1658 void NarrowSearchSpaceByCollapsingUnrolledCode(); 1659 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(); 1660 void NarrowSearchSpaceByPickingWinnerRegs(); 1661 void NarrowSearchSpaceUsingHeuristics(); 1662 1663 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution, 1664 Cost &SolutionCost, 1665 SmallVectorImpl<const Formula *> &Workspace, 1666 const Cost &CurCost, 1667 const SmallPtrSet<const SCEV *, 16> &CurRegs, 1668 DenseSet<const SCEV *> &VisitedRegs) const; 1669 void Solve(SmallVectorImpl<const Formula *> &Solution) const; 1670 1671 BasicBlock::iterator 1672 HoistInsertPosition(BasicBlock::iterator IP, 1673 const SmallVectorImpl<Instruction *> &Inputs) const; 1674 BasicBlock::iterator 1675 AdjustInsertPositionForExpand(BasicBlock::iterator IP, 1676 const LSRFixup &LF, 1677 const LSRUse &LU, 1678 SCEVExpander &Rewriter) const; 1679 1680 Value *Expand(const LSRFixup &LF, 1681 const Formula &F, 1682 BasicBlock::iterator IP, 1683 SCEVExpander &Rewriter, 1684 SmallVectorImpl<WeakVH> &DeadInsts) const; 1685 void RewriteForPHI(PHINode *PN, const LSRFixup &LF, 1686 const Formula &F, 1687 SCEVExpander &Rewriter, 1688 SmallVectorImpl<WeakVH> &DeadInsts, 1689 Pass *P) const; 1690 void Rewrite(const LSRFixup &LF, 1691 const Formula &F, 1692 SCEVExpander &Rewriter, 1693 SmallVectorImpl<WeakVH> &DeadInsts, 1694 Pass *P) const; 1695 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution, 1696 Pass *P); 1697 1698public: 1699 LSRInstance(Loop *L, Pass *P); 1700 1701 bool getChanged() const { return Changed; } 1702 1703 void print_factors_and_types(raw_ostream &OS) const; 1704 void print_fixups(raw_ostream &OS) const; 1705 void print_uses(raw_ostream &OS) const; 1706 void print(raw_ostream &OS) const; 1707 void dump() const; 1708}; 1709 1710} 1711 1712/// OptimizeShadowIV - If IV is used in a int-to-float cast 1713/// inside the loop then try to eliminate the cast operation. 1714void LSRInstance::OptimizeShadowIV() { 1715 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); 1716 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) 1717 return; 1718 1719 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); 1720 UI != E; /* empty */) { 1721 IVUsers::const_iterator CandidateUI = UI; 1722 ++UI; 1723 Instruction *ShadowUse = CandidateUI->getUser(); 1724 Type *DestTy = 0; 1725 bool IsSigned = false; 1726 1727 /* If shadow use is a int->float cast then insert a second IV 1728 to eliminate this cast. 1729 1730 for (unsigned i = 0; i < n; ++i) 1731 foo((double)i); 1732 1733 is transformed into 1734 1735 double d = 0.0; 1736 for (unsigned i = 0; i < n; ++i, ++d) 1737 foo(d); 1738 */ 1739 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) { 1740 IsSigned = false; 1741 DestTy = UCast->getDestTy(); 1742 } 1743 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) { 1744 IsSigned = true; 1745 DestTy = SCast->getDestTy(); 1746 } 1747 if (!DestTy) continue; 1748 1749 // If target does not support DestTy natively then do not apply 1750 // this transformation. 1751 if (!TTI.isTypeLegal(DestTy)) continue; 1752 1753 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0)); 1754 if (!PH) continue; 1755 if (PH->getNumIncomingValues() != 2) continue; 1756 1757 Type *SrcTy = PH->getType(); 1758 int Mantissa = DestTy->getFPMantissaWidth(); 1759 if (Mantissa == -1) continue; 1760 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa) 1761 continue; 1762 1763 unsigned Entry, Latch; 1764 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) { 1765 Entry = 0; 1766 Latch = 1; 1767 } else { 1768 Entry = 1; 1769 Latch = 0; 1770 } 1771 1772 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry)); 1773 if (!Init) continue; 1774 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ? 1775 (double)Init->getSExtValue() : 1776 (double)Init->getZExtValue()); 1777 1778 BinaryOperator *Incr = 1779 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch)); 1780 if (!Incr) continue; 1781 if (Incr->getOpcode() != Instruction::Add 1782 && Incr->getOpcode() != Instruction::Sub) 1783 continue; 1784 1785 /* Initialize new IV, double d = 0.0 in above example. */ 1786 ConstantInt *C = 0; 1787 if (Incr->getOperand(0) == PH) 1788 C = dyn_cast<ConstantInt>(Incr->getOperand(1)); 1789 else if (Incr->getOperand(1) == PH) 1790 C = dyn_cast<ConstantInt>(Incr->getOperand(0)); 1791 else 1792 continue; 1793 1794 if (!C) continue; 1795 1796 // Ignore negative constants, as the code below doesn't handle them 1797 // correctly. TODO: Remove this restriction. 1798 if (!C->getValue().isStrictlyPositive()) continue; 1799 1800 /* Add new PHINode. */ 1801 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH); 1802 1803 /* create new increment. '++d' in above example. */ 1804 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue()); 1805 BinaryOperator *NewIncr = 1806 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ? 1807 Instruction::FAdd : Instruction::FSub, 1808 NewPH, CFP, "IV.S.next.", Incr); 1809 1810 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry)); 1811 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch)); 1812 1813 /* Remove cast operation */ 1814 ShadowUse->replaceAllUsesWith(NewPH); 1815 ShadowUse->eraseFromParent(); 1816 Changed = true; 1817 break; 1818 } 1819} 1820 1821/// FindIVUserForCond - If Cond has an operand that is an expression of an IV, 1822/// set the IV user and stride information and return true, otherwise return 1823/// false. 1824bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) { 1825 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) 1826 if (UI->getUser() == Cond) { 1827 // NOTE: we could handle setcc instructions with multiple uses here, but 1828 // InstCombine does it as well for simple uses, it's not clear that it 1829 // occurs enough in real life to handle. 1830 CondUse = UI; 1831 return true; 1832 } 1833 return false; 1834} 1835 1836/// OptimizeMax - Rewrite the loop's terminating condition if it uses 1837/// a max computation. 1838/// 1839/// This is a narrow solution to a specific, but acute, problem. For loops 1840/// like this: 1841/// 1842/// i = 0; 1843/// do { 1844/// p[i] = 0.0; 1845/// } while (++i < n); 1846/// 1847/// the trip count isn't just 'n', because 'n' might not be positive. And 1848/// unfortunately this can come up even for loops where the user didn't use 1849/// a C do-while loop. For example, seemingly well-behaved top-test loops 1850/// will commonly be lowered like this: 1851// 1852/// if (n > 0) { 1853/// i = 0; 1854/// do { 1855/// p[i] = 0.0; 1856/// } while (++i < n); 1857/// } 1858/// 1859/// and then it's possible for subsequent optimization to obscure the if 1860/// test in such a way that indvars can't find it. 1861/// 1862/// When indvars can't find the if test in loops like this, it creates a 1863/// max expression, which allows it to give the loop a canonical 1864/// induction variable: 1865/// 1866/// i = 0; 1867/// max = n < 1 ? 1 : n; 1868/// do { 1869/// p[i] = 0.0; 1870/// } while (++i != max); 1871/// 1872/// Canonical induction variables are necessary because the loop passes 1873/// are designed around them. The most obvious example of this is the 1874/// LoopInfo analysis, which doesn't remember trip count values. It 1875/// expects to be able to rediscover the trip count each time it is 1876/// needed, and it does this using a simple analysis that only succeeds if 1877/// the loop has a canonical induction variable. 1878/// 1879/// However, when it comes time to generate code, the maximum operation 1880/// can be quite costly, especially if it's inside of an outer loop. 1881/// 1882/// This function solves this problem by detecting this type of loop and 1883/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting 1884/// the instructions for the maximum computation. 1885/// 1886ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) { 1887 // Check that the loop matches the pattern we're looking for. 1888 if (Cond->getPredicate() != CmpInst::ICMP_EQ && 1889 Cond->getPredicate() != CmpInst::ICMP_NE) 1890 return Cond; 1891 1892 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1)); 1893 if (!Sel || !Sel->hasOneUse()) return Cond; 1894 1895 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); 1896 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) 1897 return Cond; 1898 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1); 1899 1900 // Add one to the backedge-taken count to get the trip count. 1901 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount); 1902 if (IterationCount != SE.getSCEV(Sel)) return Cond; 1903 1904 // Check for a max calculation that matches the pattern. There's no check 1905 // for ICMP_ULE here because the comparison would be with zero, which 1906 // isn't interesting. 1907 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE; 1908 const SCEVNAryExpr *Max = 0; 1909 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) { 1910 Pred = ICmpInst::ICMP_SLE; 1911 Max = S; 1912 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) { 1913 Pred = ICmpInst::ICMP_SLT; 1914 Max = S; 1915 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) { 1916 Pred = ICmpInst::ICMP_ULT; 1917 Max = U; 1918 } else { 1919 // No match; bail. 1920 return Cond; 1921 } 1922 1923 // To handle a max with more than two operands, this optimization would 1924 // require additional checking and setup. 1925 if (Max->getNumOperands() != 2) 1926 return Cond; 1927 1928 const SCEV *MaxLHS = Max->getOperand(0); 1929 const SCEV *MaxRHS = Max->getOperand(1); 1930 1931 // ScalarEvolution canonicalizes constants to the left. For < and >, look 1932 // for a comparison with 1. For <= and >=, a comparison with zero. 1933 if (!MaxLHS || 1934 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One))) 1935 return Cond; 1936 1937 // Check the relevant induction variable for conformance to 1938 // the pattern. 1939 const SCEV *IV = SE.getSCEV(Cond->getOperand(0)); 1940 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV); 1941 if (!AR || !AR->isAffine() || 1942 AR->getStart() != One || 1943 AR->getStepRecurrence(SE) != One) 1944 return Cond; 1945 1946 assert(AR->getLoop() == L && 1947 "Loop condition operand is an addrec in a different loop!"); 1948 1949 // Check the right operand of the select, and remember it, as it will 1950 // be used in the new comparison instruction. 1951 Value *NewRHS = 0; 1952 if (ICmpInst::isTrueWhenEqual(Pred)) { 1953 // Look for n+1, and grab n. 1954 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1))) 1955 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1))) 1956 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS) 1957 NewRHS = BO->getOperand(0); 1958 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2))) 1959 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1))) 1960 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS) 1961 NewRHS = BO->getOperand(0); 1962 if (!NewRHS) 1963 return Cond; 1964 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS) 1965 NewRHS = Sel->getOperand(1); 1966 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS) 1967 NewRHS = Sel->getOperand(2); 1968 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS)) 1969 NewRHS = SU->getValue(); 1970 else 1971 // Max doesn't match expected pattern. 1972 return Cond; 1973 1974 // Determine the new comparison opcode. It may be signed or unsigned, 1975 // and the original comparison may be either equality or inequality. 1976 if (Cond->getPredicate() == CmpInst::ICMP_EQ) 1977 Pred = CmpInst::getInversePredicate(Pred); 1978 1979 // Ok, everything looks ok to change the condition into an SLT or SGE and 1980 // delete the max calculation. 1981 ICmpInst *NewCond = 1982 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp"); 1983 1984 // Delete the max calculation instructions. 1985 Cond->replaceAllUsesWith(NewCond); 1986 CondUse->setUser(NewCond); 1987 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0)); 1988 Cond->eraseFromParent(); 1989 Sel->eraseFromParent(); 1990 if (Cmp->use_empty()) 1991 Cmp->eraseFromParent(); 1992 return NewCond; 1993} 1994 1995/// OptimizeLoopTermCond - Change loop terminating condition to use the 1996/// postinc iv when possible. 1997void 1998LSRInstance::OptimizeLoopTermCond() { 1999 SmallPtrSet<Instruction *, 4> PostIncs; 2000 2001 BasicBlock *LatchBlock = L->getLoopLatch(); 2002 SmallVector<BasicBlock*, 8> ExitingBlocks; 2003 L->getExitingBlocks(ExitingBlocks); 2004 2005 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) { 2006 BasicBlock *ExitingBlock = ExitingBlocks[i]; 2007 2008 // Get the terminating condition for the loop if possible. If we 2009 // can, we want to change it to use a post-incremented version of its 2010 // induction variable, to allow coalescing the live ranges for the IV into 2011 // one register value. 2012 2013 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator()); 2014 if (!TermBr) 2015 continue; 2016 // FIXME: Overly conservative, termination condition could be an 'or' etc.. 2017 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition())) 2018 continue; 2019 2020 // Search IVUsesByStride to find Cond's IVUse if there is one. 2021 IVStrideUse *CondUse = 0; 2022 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition()); 2023 if (!FindIVUserForCond(Cond, CondUse)) 2024 continue; 2025 2026 // If the trip count is computed in terms of a max (due to ScalarEvolution 2027 // being unable to find a sufficient guard, for example), change the loop 2028 // comparison to use SLT or ULT instead of NE. 2029 // One consequence of doing this now is that it disrupts the count-down 2030 // optimization. That's not always a bad thing though, because in such 2031 // cases it may still be worthwhile to avoid a max. 2032 Cond = OptimizeMax(Cond, CondUse); 2033 2034 // If this exiting block dominates the latch block, it may also use 2035 // the post-inc value if it won't be shared with other uses. 2036 // Check for dominance. 2037 if (!DT.dominates(ExitingBlock, LatchBlock)) 2038 continue; 2039 2040 // Conservatively avoid trying to use the post-inc value in non-latch 2041 // exits if there may be pre-inc users in intervening blocks. 2042 if (LatchBlock != ExitingBlock) 2043 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) 2044 // Test if the use is reachable from the exiting block. This dominator 2045 // query is a conservative approximation of reachability. 2046 if (&*UI != CondUse && 2047 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) { 2048 // Conservatively assume there may be reuse if the quotient of their 2049 // strides could be a legal scale. 2050 const SCEV *A = IU.getStride(*CondUse, L); 2051 const SCEV *B = IU.getStride(*UI, L); 2052 if (!A || !B) continue; 2053 if (SE.getTypeSizeInBits(A->getType()) != 2054 SE.getTypeSizeInBits(B->getType())) { 2055 if (SE.getTypeSizeInBits(A->getType()) > 2056 SE.getTypeSizeInBits(B->getType())) 2057 B = SE.getSignExtendExpr(B, A->getType()); 2058 else 2059 A = SE.getSignExtendExpr(A, B->getType()); 2060 } 2061 if (const SCEVConstant *D = 2062 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) { 2063 const ConstantInt *C = D->getValue(); 2064 // Stride of one or negative one can have reuse with non-addresses. 2065 if (C->isOne() || C->isAllOnesValue()) 2066 goto decline_post_inc; 2067 // Avoid weird situations. 2068 if (C->getValue().getMinSignedBits() >= 64 || 2069 C->getValue().isMinSignedValue()) 2070 goto decline_post_inc; 2071 // Check for possible scaled-address reuse. 2072 Type *AccessTy = getAccessType(UI->getUser()); 2073 int64_t Scale = C->getSExtValue(); 2074 if (TTI.isLegalAddressingMode(AccessTy, /*BaseGV=*/ 0, 2075 /*BaseOffset=*/ 0, 2076 /*HasBaseReg=*/ false, Scale)) 2077 goto decline_post_inc; 2078 Scale = -Scale; 2079 if (TTI.isLegalAddressingMode(AccessTy, /*BaseGV=*/ 0, 2080 /*BaseOffset=*/ 0, 2081 /*HasBaseReg=*/ false, Scale)) 2082 goto decline_post_inc; 2083 } 2084 } 2085 2086 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: " 2087 << *Cond << '\n'); 2088 2089 // It's possible for the setcc instruction to be anywhere in the loop, and 2090 // possible for it to have multiple users. If it is not immediately before 2091 // the exiting block branch, move it. 2092 if (&*++BasicBlock::iterator(Cond) != TermBr) { 2093 if (Cond->hasOneUse()) { 2094 Cond->moveBefore(TermBr); 2095 } else { 2096 // Clone the terminating condition and insert into the loopend. 2097 ICmpInst *OldCond = Cond; 2098 Cond = cast<ICmpInst>(Cond->clone()); 2099 Cond->setName(L->getHeader()->getName() + ".termcond"); 2100 ExitingBlock->getInstList().insert(TermBr, Cond); 2101 2102 // Clone the IVUse, as the old use still exists! 2103 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace()); 2104 TermBr->replaceUsesOfWith(OldCond, Cond); 2105 } 2106 } 2107 2108 // If we get to here, we know that we can transform the setcc instruction to 2109 // use the post-incremented version of the IV, allowing us to coalesce the 2110 // live ranges for the IV correctly. 2111 CondUse->transformToPostInc(L); 2112 Changed = true; 2113 2114 PostIncs.insert(Cond); 2115 decline_post_inc:; 2116 } 2117 2118 // Determine an insertion point for the loop induction variable increment. It 2119 // must dominate all the post-inc comparisons we just set up, and it must 2120 // dominate the loop latch edge. 2121 IVIncInsertPos = L->getLoopLatch()->getTerminator(); 2122 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(), 2123 E = PostIncs.end(); I != E; ++I) { 2124 BasicBlock *BB = 2125 DT.findNearestCommonDominator(IVIncInsertPos->getParent(), 2126 (*I)->getParent()); 2127 if (BB == (*I)->getParent()) 2128 IVIncInsertPos = *I; 2129 else if (BB != IVIncInsertPos->getParent()) 2130 IVIncInsertPos = BB->getTerminator(); 2131 } 2132} 2133 2134/// reconcileNewOffset - Determine if the given use can accommodate a fixup 2135/// at the given offset and other details. If so, update the use and 2136/// return true. 2137bool 2138LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg, 2139 LSRUse::KindType Kind, Type *AccessTy) { 2140 int64_t NewMinOffset = LU.MinOffset; 2141 int64_t NewMaxOffset = LU.MaxOffset; 2142 Type *NewAccessTy = AccessTy; 2143 2144 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to 2145 // something conservative, however this can pessimize in the case that one of 2146 // the uses will have all its uses outside the loop, for example. 2147 if (LU.Kind != Kind) 2148 return false; 2149 // Conservatively assume HasBaseReg is true for now. 2150 if (NewOffset < LU.MinOffset) { 2151 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ 0, 2152 LU.MaxOffset - NewOffset, HasBaseReg)) 2153 return false; 2154 NewMinOffset = NewOffset; 2155 } else if (NewOffset > LU.MaxOffset) { 2156 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ 0, 2157 NewOffset - LU.MinOffset, HasBaseReg)) 2158 return false; 2159 NewMaxOffset = NewOffset; 2160 } 2161 // Check for a mismatched access type, and fall back conservatively as needed. 2162 // TODO: Be less conservative when the type is similar and can use the same 2163 // addressing modes. 2164 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy) 2165 NewAccessTy = Type::getVoidTy(AccessTy->getContext()); 2166 2167 // Update the use. 2168 LU.MinOffset = NewMinOffset; 2169 LU.MaxOffset = NewMaxOffset; 2170 LU.AccessTy = NewAccessTy; 2171 if (NewOffset != LU.Offsets.back()) 2172 LU.Offsets.push_back(NewOffset); 2173 return true; 2174} 2175 2176/// getUse - Return an LSRUse index and an offset value for a fixup which 2177/// needs the given expression, with the given kind and optional access type. 2178/// Either reuse an existing use or create a new one, as needed. 2179std::pair<size_t, int64_t> 2180LSRInstance::getUse(const SCEV *&Expr, 2181 LSRUse::KindType Kind, Type *AccessTy) { 2182 const SCEV *Copy = Expr; 2183 int64_t Offset = ExtractImmediate(Expr, SE); 2184 2185 // Basic uses can't accept any offset, for example. 2186 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ 0, 2187 Offset, /*HasBaseReg=*/ true)) { 2188 Expr = Copy; 2189 Offset = 0; 2190 } 2191 2192 std::pair<UseMapTy::iterator, bool> P = 2193 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0)); 2194 if (!P.second) { 2195 // A use already existed with this base. 2196 size_t LUIdx = P.first->second; 2197 LSRUse &LU = Uses[LUIdx]; 2198 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy)) 2199 // Reuse this use. 2200 return std::make_pair(LUIdx, Offset); 2201 } 2202 2203 // Create a new use. 2204 size_t LUIdx = Uses.size(); 2205 P.first->second = LUIdx; 2206 Uses.push_back(LSRUse(Kind, AccessTy)); 2207 LSRUse &LU = Uses[LUIdx]; 2208 2209 // We don't need to track redundant offsets, but we don't need to go out 2210 // of our way here to avoid them. 2211 if (LU.Offsets.empty() || Offset != LU.Offsets.back()) 2212 LU.Offsets.push_back(Offset); 2213 2214 LU.MinOffset = Offset; 2215 LU.MaxOffset = Offset; 2216 return std::make_pair(LUIdx, Offset); 2217} 2218 2219/// DeleteUse - Delete the given use from the Uses list. 2220void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) { 2221 if (&LU != &Uses.back()) 2222 std::swap(LU, Uses.back()); 2223 Uses.pop_back(); 2224 2225 // Update RegUses. 2226 RegUses.SwapAndDropUse(LUIdx, Uses.size()); 2227} 2228 2229/// FindUseWithFormula - Look for a use distinct from OrigLU which is has 2230/// a formula that has the same registers as the given formula. 2231LSRUse * 2232LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF, 2233 const LSRUse &OrigLU) { 2234 // Search all uses for the formula. This could be more clever. 2235 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2236 LSRUse &LU = Uses[LUIdx]; 2237 // Check whether this use is close enough to OrigLU, to see whether it's 2238 // worthwhile looking through its formulae. 2239 // Ignore ICmpZero uses because they may contain formulae generated by 2240 // GenerateICmpZeroScales, in which case adding fixup offsets may 2241 // be invalid. 2242 if (&LU != &OrigLU && 2243 LU.Kind != LSRUse::ICmpZero && 2244 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy && 2245 LU.WidestFixupType == OrigLU.WidestFixupType && 2246 LU.HasFormulaWithSameRegs(OrigF)) { 2247 // Scan through this use's formulae. 2248 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), 2249 E = LU.Formulae.end(); I != E; ++I) { 2250 const Formula &F = *I; 2251 // Check to see if this formula has the same registers and symbols 2252 // as OrigF. 2253 if (F.BaseRegs == OrigF.BaseRegs && 2254 F.ScaledReg == OrigF.ScaledReg && 2255 F.BaseGV == OrigF.BaseGV && 2256 F.Scale == OrigF.Scale && 2257 F.UnfoldedOffset == OrigF.UnfoldedOffset) { 2258 if (F.BaseOffset == 0) 2259 return &LU; 2260 // This is the formula where all the registers and symbols matched; 2261 // there aren't going to be any others. Since we declined it, we 2262 // can skip the rest of the formulae and proceed to the next LSRUse. 2263 break; 2264 } 2265 } 2266 } 2267 } 2268 2269 // Nothing looked good. 2270 return 0; 2271} 2272 2273void LSRInstance::CollectInterestingTypesAndFactors() { 2274 SmallSetVector<const SCEV *, 4> Strides; 2275 2276 // Collect interesting types and strides. 2277 SmallVector<const SCEV *, 4> Worklist; 2278 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { 2279 const SCEV *Expr = IU.getExpr(*UI); 2280 2281 // Collect interesting types. 2282 Types.insert(SE.getEffectiveSCEVType(Expr->getType())); 2283 2284 // Add strides for mentioned loops. 2285 Worklist.push_back(Expr); 2286 do { 2287 const SCEV *S = Worklist.pop_back_val(); 2288 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 2289 if (AR->getLoop() == L) 2290 Strides.insert(AR->getStepRecurrence(SE)); 2291 Worklist.push_back(AR->getStart()); 2292 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 2293 Worklist.append(Add->op_begin(), Add->op_end()); 2294 } 2295 } while (!Worklist.empty()); 2296 } 2297 2298 // Compute interesting factors from the set of interesting strides. 2299 for (SmallSetVector<const SCEV *, 4>::const_iterator 2300 I = Strides.begin(), E = Strides.end(); I != E; ++I) 2301 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter = 2302 std::next(I); NewStrideIter != E; ++NewStrideIter) { 2303 const SCEV *OldStride = *I; 2304 const SCEV *NewStride = *NewStrideIter; 2305 2306 if (SE.getTypeSizeInBits(OldStride->getType()) != 2307 SE.getTypeSizeInBits(NewStride->getType())) { 2308 if (SE.getTypeSizeInBits(OldStride->getType()) > 2309 SE.getTypeSizeInBits(NewStride->getType())) 2310 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType()); 2311 else 2312 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType()); 2313 } 2314 if (const SCEVConstant *Factor = 2315 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride, 2316 SE, true))) { 2317 if (Factor->getValue()->getValue().getMinSignedBits() <= 64) 2318 Factors.insert(Factor->getValue()->getValue().getSExtValue()); 2319 } else if (const SCEVConstant *Factor = 2320 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride, 2321 NewStride, 2322 SE, true))) { 2323 if (Factor->getValue()->getValue().getMinSignedBits() <= 64) 2324 Factors.insert(Factor->getValue()->getValue().getSExtValue()); 2325 } 2326 } 2327 2328 // If all uses use the same type, don't bother looking for truncation-based 2329 // reuse. 2330 if (Types.size() == 1) 2331 Types.clear(); 2332 2333 DEBUG(print_factors_and_types(dbgs())); 2334} 2335 2336/// findIVOperand - Helper for CollectChains that finds an IV operand (computed 2337/// by an AddRec in this loop) within [OI,OE) or returns OE. If IVUsers mapped 2338/// Instructions to IVStrideUses, we could partially skip this. 2339static User::op_iterator 2340findIVOperand(User::op_iterator OI, User::op_iterator OE, 2341 Loop *L, ScalarEvolution &SE) { 2342 for(; OI != OE; ++OI) { 2343 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) { 2344 if (!SE.isSCEVable(Oper->getType())) 2345 continue; 2346 2347 if (const SCEVAddRecExpr *AR = 2348 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) { 2349 if (AR->getLoop() == L) 2350 break; 2351 } 2352 } 2353 } 2354 return OI; 2355} 2356 2357/// getWideOperand - IVChain logic must consistenctly peek base TruncInst 2358/// operands, so wrap it in a convenient helper. 2359static Value *getWideOperand(Value *Oper) { 2360 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper)) 2361 return Trunc->getOperand(0); 2362 return Oper; 2363} 2364 2365/// isCompatibleIVType - Return true if we allow an IV chain to include both 2366/// types. 2367static bool isCompatibleIVType(Value *LVal, Value *RVal) { 2368 Type *LType = LVal->getType(); 2369 Type *RType = RVal->getType(); 2370 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy()); 2371} 2372 2373/// getExprBase - Return an approximation of this SCEV expression's "base", or 2374/// NULL for any constant. Returning the expression itself is 2375/// conservative. Returning a deeper subexpression is more precise and valid as 2376/// long as it isn't less complex than another subexpression. For expressions 2377/// involving multiple unscaled values, we need to return the pointer-type 2378/// SCEVUnknown. This avoids forming chains across objects, such as: 2379/// PrevOper==a[i], IVOper==b[i], IVInc==b-a. 2380/// 2381/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost 2382/// SCEVUnknown, we simply return the rightmost SCEV operand. 2383static const SCEV *getExprBase(const SCEV *S) { 2384 switch (S->getSCEVType()) { 2385 default: // uncluding scUnknown. 2386 return S; 2387 case scConstant: 2388 return 0; 2389 case scTruncate: 2390 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand()); 2391 case scZeroExtend: 2392 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand()); 2393 case scSignExtend: 2394 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand()); 2395 case scAddExpr: { 2396 // Skip over scaled operands (scMulExpr) to follow add operands as long as 2397 // there's nothing more complex. 2398 // FIXME: not sure if we want to recognize negation. 2399 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S); 2400 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()), 2401 E(Add->op_begin()); I != E; ++I) { 2402 const SCEV *SubExpr = *I; 2403 if (SubExpr->getSCEVType() == scAddExpr) 2404 return getExprBase(SubExpr); 2405 2406 if (SubExpr->getSCEVType() != scMulExpr) 2407 return SubExpr; 2408 } 2409 return S; // all operands are scaled, be conservative. 2410 } 2411 case scAddRecExpr: 2412 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart()); 2413 } 2414} 2415 2416/// Return true if the chain increment is profitable to expand into a loop 2417/// invariant value, which may require its own register. A profitable chain 2418/// increment will be an offset relative to the same base. We allow such offsets 2419/// to potentially be used as chain increment as long as it's not obviously 2420/// expensive to expand using real instructions. 2421bool IVChain::isProfitableIncrement(const SCEV *OperExpr, 2422 const SCEV *IncExpr, 2423 ScalarEvolution &SE) { 2424 // Aggressively form chains when -stress-ivchain. 2425 if (StressIVChain) 2426 return true; 2427 2428 // Do not replace a constant offset from IV head with a nonconstant IV 2429 // increment. 2430 if (!isa<SCEVConstant>(IncExpr)) { 2431 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand)); 2432 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr))) 2433 return 0; 2434 } 2435 2436 SmallPtrSet<const SCEV*, 8> Processed; 2437 return !isHighCostExpansion(IncExpr, Processed, SE); 2438} 2439 2440/// Return true if the number of registers needed for the chain is estimated to 2441/// be less than the number required for the individual IV users. First prohibit 2442/// any IV users that keep the IV live across increments (the Users set should 2443/// be empty). Next count the number and type of increments in the chain. 2444/// 2445/// Chaining IVs can lead to considerable code bloat if ISEL doesn't 2446/// effectively use postinc addressing modes. Only consider it profitable it the 2447/// increments can be computed in fewer registers when chained. 2448/// 2449/// TODO: Consider IVInc free if it's already used in another chains. 2450static bool 2451isProfitableChain(IVChain &Chain, SmallPtrSet<Instruction*, 4> &Users, 2452 ScalarEvolution &SE, const TargetTransformInfo &TTI) { 2453 if (StressIVChain) 2454 return true; 2455 2456 if (!Chain.hasIncs()) 2457 return false; 2458 2459 if (!Users.empty()) { 2460 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n"; 2461 for (SmallPtrSet<Instruction*, 4>::const_iterator I = Users.begin(), 2462 E = Users.end(); I != E; ++I) { 2463 dbgs() << " " << **I << "\n"; 2464 }); 2465 return false; 2466 } 2467 assert(!Chain.Incs.empty() && "empty IV chains are not allowed"); 2468 2469 // The chain itself may require a register, so intialize cost to 1. 2470 int cost = 1; 2471 2472 // A complete chain likely eliminates the need for keeping the original IV in 2473 // a register. LSR does not currently know how to form a complete chain unless 2474 // the header phi already exists. 2475 if (isa<PHINode>(Chain.tailUserInst()) 2476 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) { 2477 --cost; 2478 } 2479 const SCEV *LastIncExpr = 0; 2480 unsigned NumConstIncrements = 0; 2481 unsigned NumVarIncrements = 0; 2482 unsigned NumReusedIncrements = 0; 2483 for (IVChain::const_iterator I = Chain.begin(), E = Chain.end(); 2484 I != E; ++I) { 2485 2486 if (I->IncExpr->isZero()) 2487 continue; 2488 2489 // Incrementing by zero or some constant is neutral. We assume constants can 2490 // be folded into an addressing mode or an add's immediate operand. 2491 if (isa<SCEVConstant>(I->IncExpr)) { 2492 ++NumConstIncrements; 2493 continue; 2494 } 2495 2496 if (I->IncExpr == LastIncExpr) 2497 ++NumReusedIncrements; 2498 else 2499 ++NumVarIncrements; 2500 2501 LastIncExpr = I->IncExpr; 2502 } 2503 // An IV chain with a single increment is handled by LSR's postinc 2504 // uses. However, a chain with multiple increments requires keeping the IV's 2505 // value live longer than it needs to be if chained. 2506 if (NumConstIncrements > 1) 2507 --cost; 2508 2509 // Materializing increment expressions in the preheader that didn't exist in 2510 // the original code may cost a register. For example, sign-extended array 2511 // indices can produce ridiculous increments like this: 2512 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64))) 2513 cost += NumVarIncrements; 2514 2515 // Reusing variable increments likely saves a register to hold the multiple of 2516 // the stride. 2517 cost -= NumReusedIncrements; 2518 2519 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost 2520 << "\n"); 2521 2522 return cost < 0; 2523} 2524 2525/// ChainInstruction - Add this IV user to an existing chain or make it the head 2526/// of a new chain. 2527void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper, 2528 SmallVectorImpl<ChainUsers> &ChainUsersVec) { 2529 // When IVs are used as types of varying widths, they are generally converted 2530 // to a wider type with some uses remaining narrow under a (free) trunc. 2531 Value *const NextIV = getWideOperand(IVOper); 2532 const SCEV *const OperExpr = SE.getSCEV(NextIV); 2533 const SCEV *const OperExprBase = getExprBase(OperExpr); 2534 2535 // Visit all existing chains. Check if its IVOper can be computed as a 2536 // profitable loop invariant increment from the last link in the Chain. 2537 unsigned ChainIdx = 0, NChains = IVChainVec.size(); 2538 const SCEV *LastIncExpr = 0; 2539 for (; ChainIdx < NChains; ++ChainIdx) { 2540 IVChain &Chain = IVChainVec[ChainIdx]; 2541 2542 // Prune the solution space aggressively by checking that both IV operands 2543 // are expressions that operate on the same unscaled SCEVUnknown. This 2544 // "base" will be canceled by the subsequent getMinusSCEV call. Checking 2545 // first avoids creating extra SCEV expressions. 2546 if (!StressIVChain && Chain.ExprBase != OperExprBase) 2547 continue; 2548 2549 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand); 2550 if (!isCompatibleIVType(PrevIV, NextIV)) 2551 continue; 2552 2553 // A phi node terminates a chain. 2554 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst())) 2555 continue; 2556 2557 // The increment must be loop-invariant so it can be kept in a register. 2558 const SCEV *PrevExpr = SE.getSCEV(PrevIV); 2559 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr); 2560 if (!SE.isLoopInvariant(IncExpr, L)) 2561 continue; 2562 2563 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) { 2564 LastIncExpr = IncExpr; 2565 break; 2566 } 2567 } 2568 // If we haven't found a chain, create a new one, unless we hit the max. Don't 2569 // bother for phi nodes, because they must be last in the chain. 2570 if (ChainIdx == NChains) { 2571 if (isa<PHINode>(UserInst)) 2572 return; 2573 if (NChains >= MaxChains && !StressIVChain) { 2574 DEBUG(dbgs() << "IV Chain Limit\n"); 2575 return; 2576 } 2577 LastIncExpr = OperExpr; 2578 // IVUsers may have skipped over sign/zero extensions. We don't currently 2579 // attempt to form chains involving extensions unless they can be hoisted 2580 // into this loop's AddRec. 2581 if (!isa<SCEVAddRecExpr>(LastIncExpr)) 2582 return; 2583 ++NChains; 2584 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr), 2585 OperExprBase)); 2586 ChainUsersVec.resize(NChains); 2587 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst 2588 << ") IV=" << *LastIncExpr << "\n"); 2589 } else { 2590 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst 2591 << ") IV+" << *LastIncExpr << "\n"); 2592 // Add this IV user to the end of the chain. 2593 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr)); 2594 } 2595 IVChain &Chain = IVChainVec[ChainIdx]; 2596 2597 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers; 2598 // This chain's NearUsers become FarUsers. 2599 if (!LastIncExpr->isZero()) { 2600 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(), 2601 NearUsers.end()); 2602 NearUsers.clear(); 2603 } 2604 2605 // All other uses of IVOperand become near uses of the chain. 2606 // We currently ignore intermediate values within SCEV expressions, assuming 2607 // they will eventually be used be the current chain, or can be computed 2608 // from one of the chain increments. To be more precise we could 2609 // transitively follow its user and only add leaf IV users to the set. 2610 for (User *U : IVOper->users()) { 2611 Instruction *OtherUse = dyn_cast<Instruction>(U); 2612 if (!OtherUse) 2613 continue; 2614 // Uses in the chain will no longer be uses if the chain is formed. 2615 // Include the head of the chain in this iteration (not Chain.begin()). 2616 IVChain::const_iterator IncIter = Chain.Incs.begin(); 2617 IVChain::const_iterator IncEnd = Chain.Incs.end(); 2618 for( ; IncIter != IncEnd; ++IncIter) { 2619 if (IncIter->UserInst == OtherUse) 2620 break; 2621 } 2622 if (IncIter != IncEnd) 2623 continue; 2624 2625 if (SE.isSCEVable(OtherUse->getType()) 2626 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse)) 2627 && IU.isIVUserOrOperand(OtherUse)) { 2628 continue; 2629 } 2630 NearUsers.insert(OtherUse); 2631 } 2632 2633 // Since this user is part of the chain, it's no longer considered a use 2634 // of the chain. 2635 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst); 2636} 2637 2638/// CollectChains - Populate the vector of Chains. 2639/// 2640/// This decreases ILP at the architecture level. Targets with ample registers, 2641/// multiple memory ports, and no register renaming probably don't want 2642/// this. However, such targets should probably disable LSR altogether. 2643/// 2644/// The job of LSR is to make a reasonable choice of induction variables across 2645/// the loop. Subsequent passes can easily "unchain" computation exposing more 2646/// ILP *within the loop* if the target wants it. 2647/// 2648/// Finding the best IV chain is potentially a scheduling problem. Since LSR 2649/// will not reorder memory operations, it will recognize this as a chain, but 2650/// will generate redundant IV increments. Ideally this would be corrected later 2651/// by a smart scheduler: 2652/// = A[i] 2653/// = A[i+x] 2654/// A[i] = 2655/// A[i+x] = 2656/// 2657/// TODO: Walk the entire domtree within this loop, not just the path to the 2658/// loop latch. This will discover chains on side paths, but requires 2659/// maintaining multiple copies of the Chains state. 2660void LSRInstance::CollectChains() { 2661 DEBUG(dbgs() << "Collecting IV Chains.\n"); 2662 SmallVector<ChainUsers, 8> ChainUsersVec; 2663 2664 SmallVector<BasicBlock *,8> LatchPath; 2665 BasicBlock *LoopHeader = L->getHeader(); 2666 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch()); 2667 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) { 2668 LatchPath.push_back(Rung->getBlock()); 2669 } 2670 LatchPath.push_back(LoopHeader); 2671 2672 // Walk the instruction stream from the loop header to the loop latch. 2673 for (SmallVectorImpl<BasicBlock *>::reverse_iterator 2674 BBIter = LatchPath.rbegin(), BBEnd = LatchPath.rend(); 2675 BBIter != BBEnd; ++BBIter) { 2676 for (BasicBlock::iterator I = (*BBIter)->begin(), E = (*BBIter)->end(); 2677 I != E; ++I) { 2678 // Skip instructions that weren't seen by IVUsers analysis. 2679 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(I)) 2680 continue; 2681 2682 // Ignore users that are part of a SCEV expression. This way we only 2683 // consider leaf IV Users. This effectively rediscovers a portion of 2684 // IVUsers analysis but in program order this time. 2685 if (SE.isSCEVable(I->getType()) && !isa<SCEVUnknown>(SE.getSCEV(I))) 2686 continue; 2687 2688 // Remove this instruction from any NearUsers set it may be in. 2689 for (unsigned ChainIdx = 0, NChains = IVChainVec.size(); 2690 ChainIdx < NChains; ++ChainIdx) { 2691 ChainUsersVec[ChainIdx].NearUsers.erase(I); 2692 } 2693 // Search for operands that can be chained. 2694 SmallPtrSet<Instruction*, 4> UniqueOperands; 2695 User::op_iterator IVOpEnd = I->op_end(); 2696 User::op_iterator IVOpIter = findIVOperand(I->op_begin(), IVOpEnd, L, SE); 2697 while (IVOpIter != IVOpEnd) { 2698 Instruction *IVOpInst = cast<Instruction>(*IVOpIter); 2699 if (UniqueOperands.insert(IVOpInst)) 2700 ChainInstruction(I, IVOpInst, ChainUsersVec); 2701 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE); 2702 } 2703 } // Continue walking down the instructions. 2704 } // Continue walking down the domtree. 2705 // Visit phi backedges to determine if the chain can generate the IV postinc. 2706 for (BasicBlock::iterator I = L->getHeader()->begin(); 2707 PHINode *PN = dyn_cast<PHINode>(I); ++I) { 2708 if (!SE.isSCEVable(PN->getType())) 2709 continue; 2710 2711 Instruction *IncV = 2712 dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch())); 2713 if (IncV) 2714 ChainInstruction(PN, IncV, ChainUsersVec); 2715 } 2716 // Remove any unprofitable chains. 2717 unsigned ChainIdx = 0; 2718 for (unsigned UsersIdx = 0, NChains = IVChainVec.size(); 2719 UsersIdx < NChains; ++UsersIdx) { 2720 if (!isProfitableChain(IVChainVec[UsersIdx], 2721 ChainUsersVec[UsersIdx].FarUsers, SE, TTI)) 2722 continue; 2723 // Preserve the chain at UsesIdx. 2724 if (ChainIdx != UsersIdx) 2725 IVChainVec[ChainIdx] = IVChainVec[UsersIdx]; 2726 FinalizeChain(IVChainVec[ChainIdx]); 2727 ++ChainIdx; 2728 } 2729 IVChainVec.resize(ChainIdx); 2730} 2731 2732void LSRInstance::FinalizeChain(IVChain &Chain) { 2733 assert(!Chain.Incs.empty() && "empty IV chains are not allowed"); 2734 DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n"); 2735 2736 for (IVChain::const_iterator I = Chain.begin(), E = Chain.end(); 2737 I != E; ++I) { 2738 DEBUG(dbgs() << " Inc: " << *I->UserInst << "\n"); 2739 User::op_iterator UseI = 2740 std::find(I->UserInst->op_begin(), I->UserInst->op_end(), I->IVOperand); 2741 assert(UseI != I->UserInst->op_end() && "cannot find IV operand"); 2742 IVIncSet.insert(UseI); 2743 } 2744} 2745 2746/// Return true if the IVInc can be folded into an addressing mode. 2747static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst, 2748 Value *Operand, const TargetTransformInfo &TTI) { 2749 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr); 2750 if (!IncConst || !isAddressUse(UserInst, Operand)) 2751 return false; 2752 2753 if (IncConst->getValue()->getValue().getMinSignedBits() > 64) 2754 return false; 2755 2756 int64_t IncOffset = IncConst->getValue()->getSExtValue(); 2757 if (!isAlwaysFoldable(TTI, LSRUse::Address, 2758 getAccessType(UserInst), /*BaseGV=*/ 0, 2759 IncOffset, /*HaseBaseReg=*/ false)) 2760 return false; 2761 2762 return true; 2763} 2764 2765/// GenerateIVChains - Generate an add or subtract for each IVInc in a chain to 2766/// materialize the IV user's operand from the previous IV user's operand. 2767void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter, 2768 SmallVectorImpl<WeakVH> &DeadInsts) { 2769 // Find the new IVOperand for the head of the chain. It may have been replaced 2770 // by LSR. 2771 const IVInc &Head = Chain.Incs[0]; 2772 User::op_iterator IVOpEnd = Head.UserInst->op_end(); 2773 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user. 2774 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(), 2775 IVOpEnd, L, SE); 2776 Value *IVSrc = 0; 2777 while (IVOpIter != IVOpEnd) { 2778 IVSrc = getWideOperand(*IVOpIter); 2779 2780 // If this operand computes the expression that the chain needs, we may use 2781 // it. (Check this after setting IVSrc which is used below.) 2782 // 2783 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too 2784 // narrow for the chain, so we can no longer use it. We do allow using a 2785 // wider phi, assuming the LSR checked for free truncation. In that case we 2786 // should already have a truncate on this operand such that 2787 // getSCEV(IVSrc) == IncExpr. 2788 if (SE.getSCEV(*IVOpIter) == Head.IncExpr 2789 || SE.getSCEV(IVSrc) == Head.IncExpr) { 2790 break; 2791 } 2792 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE); 2793 } 2794 if (IVOpIter == IVOpEnd) { 2795 // Gracefully give up on this chain. 2796 DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n"); 2797 return; 2798 } 2799 2800 DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n"); 2801 Type *IVTy = IVSrc->getType(); 2802 Type *IntTy = SE.getEffectiveSCEVType(IVTy); 2803 const SCEV *LeftOverExpr = 0; 2804 for (IVChain::const_iterator IncI = Chain.begin(), 2805 IncE = Chain.end(); IncI != IncE; ++IncI) { 2806 2807 Instruction *InsertPt = IncI->UserInst; 2808 if (isa<PHINode>(InsertPt)) 2809 InsertPt = L->getLoopLatch()->getTerminator(); 2810 2811 // IVOper will replace the current IV User's operand. IVSrc is the IV 2812 // value currently held in a register. 2813 Value *IVOper = IVSrc; 2814 if (!IncI->IncExpr->isZero()) { 2815 // IncExpr was the result of subtraction of two narrow values, so must 2816 // be signed. 2817 const SCEV *IncExpr = SE.getNoopOrSignExtend(IncI->IncExpr, IntTy); 2818 LeftOverExpr = LeftOverExpr ? 2819 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr; 2820 } 2821 if (LeftOverExpr && !LeftOverExpr->isZero()) { 2822 // Expand the IV increment. 2823 Rewriter.clearPostInc(); 2824 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt); 2825 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc), 2826 SE.getUnknown(IncV)); 2827 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt); 2828 2829 // If an IV increment can't be folded, use it as the next IV value. 2830 if (!canFoldIVIncExpr(LeftOverExpr, IncI->UserInst, IncI->IVOperand, 2831 TTI)) { 2832 assert(IVTy == IVOper->getType() && "inconsistent IV increment type"); 2833 IVSrc = IVOper; 2834 LeftOverExpr = 0; 2835 } 2836 } 2837 Type *OperTy = IncI->IVOperand->getType(); 2838 if (IVTy != OperTy) { 2839 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && 2840 "cannot extend a chained IV"); 2841 IRBuilder<> Builder(InsertPt); 2842 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain"); 2843 } 2844 IncI->UserInst->replaceUsesOfWith(IncI->IVOperand, IVOper); 2845 DeadInsts.push_back(IncI->IVOperand); 2846 } 2847 // If LSR created a new, wider phi, we may also replace its postinc. We only 2848 // do this if we also found a wide value for the head of the chain. 2849 if (isa<PHINode>(Chain.tailUserInst())) { 2850 for (BasicBlock::iterator I = L->getHeader()->begin(); 2851 PHINode *Phi = dyn_cast<PHINode>(I); ++I) { 2852 if (!isCompatibleIVType(Phi, IVSrc)) 2853 continue; 2854 Instruction *PostIncV = dyn_cast<Instruction>( 2855 Phi->getIncomingValueForBlock(L->getLoopLatch())); 2856 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc))) 2857 continue; 2858 Value *IVOper = IVSrc; 2859 Type *PostIncTy = PostIncV->getType(); 2860 if (IVTy != PostIncTy) { 2861 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types"); 2862 IRBuilder<> Builder(L->getLoopLatch()->getTerminator()); 2863 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc()); 2864 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain"); 2865 } 2866 Phi->replaceUsesOfWith(PostIncV, IVOper); 2867 DeadInsts.push_back(PostIncV); 2868 } 2869 } 2870} 2871 2872void LSRInstance::CollectFixupsAndInitialFormulae() { 2873 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { 2874 Instruction *UserInst = UI->getUser(); 2875 // Skip IV users that are part of profitable IV Chains. 2876 User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(), 2877 UI->getOperandValToReplace()); 2878 assert(UseI != UserInst->op_end() && "cannot find IV operand"); 2879 if (IVIncSet.count(UseI)) 2880 continue; 2881 2882 // Record the uses. 2883 LSRFixup &LF = getNewFixup(); 2884 LF.UserInst = UserInst; 2885 LF.OperandValToReplace = UI->getOperandValToReplace(); 2886 LF.PostIncLoops = UI->getPostIncLoops(); 2887 2888 LSRUse::KindType Kind = LSRUse::Basic; 2889 Type *AccessTy = 0; 2890 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) { 2891 Kind = LSRUse::Address; 2892 AccessTy = getAccessType(LF.UserInst); 2893 } 2894 2895 const SCEV *S = IU.getExpr(*UI); 2896 2897 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as 2898 // (N - i == 0), and this allows (N - i) to be the expression that we work 2899 // with rather than just N or i, so we can consider the register 2900 // requirements for both N and i at the same time. Limiting this code to 2901 // equality icmps is not a problem because all interesting loops use 2902 // equality icmps, thanks to IndVarSimplify. 2903 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst)) 2904 if (CI->isEquality()) { 2905 // Swap the operands if needed to put the OperandValToReplace on the 2906 // left, for consistency. 2907 Value *NV = CI->getOperand(1); 2908 if (NV == LF.OperandValToReplace) { 2909 CI->setOperand(1, CI->getOperand(0)); 2910 CI->setOperand(0, NV); 2911 NV = CI->getOperand(1); 2912 Changed = true; 2913 } 2914 2915 // x == y --> x - y == 0 2916 const SCEV *N = SE.getSCEV(NV); 2917 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) { 2918 // S is normalized, so normalize N before folding it into S 2919 // to keep the result normalized. 2920 N = TransformForPostIncUse(Normalize, N, CI, 0, 2921 LF.PostIncLoops, SE, DT); 2922 Kind = LSRUse::ICmpZero; 2923 S = SE.getMinusSCEV(N, S); 2924 } 2925 2926 // -1 and the negations of all interesting strides (except the negation 2927 // of -1) are now also interesting. 2928 for (size_t i = 0, e = Factors.size(); i != e; ++i) 2929 if (Factors[i] != -1) 2930 Factors.insert(-(uint64_t)Factors[i]); 2931 Factors.insert(-1); 2932 } 2933 2934 // Set up the initial formula for this use. 2935 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy); 2936 LF.LUIdx = P.first; 2937 LF.Offset = P.second; 2938 LSRUse &LU = Uses[LF.LUIdx]; 2939 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L); 2940 if (!LU.WidestFixupType || 2941 SE.getTypeSizeInBits(LU.WidestFixupType) < 2942 SE.getTypeSizeInBits(LF.OperandValToReplace->getType())) 2943 LU.WidestFixupType = LF.OperandValToReplace->getType(); 2944 2945 // If this is the first use of this LSRUse, give it a formula. 2946 if (LU.Formulae.empty()) { 2947 InsertInitialFormula(S, LU, LF.LUIdx); 2948 CountRegisters(LU.Formulae.back(), LF.LUIdx); 2949 } 2950 } 2951 2952 DEBUG(print_fixups(dbgs())); 2953} 2954 2955/// InsertInitialFormula - Insert a formula for the given expression into 2956/// the given use, separating out loop-variant portions from loop-invariant 2957/// and loop-computable portions. 2958void 2959LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) { 2960 // Mark uses whose expressions cannot be expanded. 2961 if (!isSafeToExpand(S, SE)) 2962 LU.RigidFormula = true; 2963 2964 Formula F; 2965 F.InitialMatch(S, L, SE); 2966 bool Inserted = InsertFormula(LU, LUIdx, F); 2967 assert(Inserted && "Initial formula already exists!"); (void)Inserted; 2968} 2969 2970/// InsertSupplementalFormula - Insert a simple single-register formula for 2971/// the given expression into the given use. 2972void 2973LSRInstance::InsertSupplementalFormula(const SCEV *S, 2974 LSRUse &LU, size_t LUIdx) { 2975 Formula F; 2976 F.BaseRegs.push_back(S); 2977 F.HasBaseReg = true; 2978 bool Inserted = InsertFormula(LU, LUIdx, F); 2979 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted; 2980} 2981 2982/// CountRegisters - Note which registers are used by the given formula, 2983/// updating RegUses. 2984void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) { 2985 if (F.ScaledReg) 2986 RegUses.CountRegister(F.ScaledReg, LUIdx); 2987 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), 2988 E = F.BaseRegs.end(); I != E; ++I) 2989 RegUses.CountRegister(*I, LUIdx); 2990} 2991 2992/// InsertFormula - If the given formula has not yet been inserted, add it to 2993/// the list, and return true. Return false otherwise. 2994bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) { 2995 if (!LU.InsertFormula(F)) 2996 return false; 2997 2998 CountRegisters(F, LUIdx); 2999 return true; 3000} 3001 3002/// CollectLoopInvariantFixupsAndFormulae - Check for other uses of 3003/// loop-invariant values which we're tracking. These other uses will pin these 3004/// values in registers, making them less profitable for elimination. 3005/// TODO: This currently misses non-constant addrec step registers. 3006/// TODO: Should this give more weight to users inside the loop? 3007void 3008LSRInstance::CollectLoopInvariantFixupsAndFormulae() { 3009 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end()); 3010 SmallPtrSet<const SCEV *, 8> Inserted; 3011 3012 while (!Worklist.empty()) { 3013 const SCEV *S = Worklist.pop_back_val(); 3014 3015 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) 3016 Worklist.append(N->op_begin(), N->op_end()); 3017 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S)) 3018 Worklist.push_back(C->getOperand()); 3019 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) { 3020 Worklist.push_back(D->getLHS()); 3021 Worklist.push_back(D->getRHS()); 3022 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) { 3023 if (!Inserted.insert(US)) continue; 3024 const Value *V = US->getValue(); 3025 if (const Instruction *Inst = dyn_cast<Instruction>(V)) { 3026 // Look for instructions defined outside the loop. 3027 if (L->contains(Inst)) continue; 3028 } else if (isa<UndefValue>(V)) 3029 // Undef doesn't have a live range, so it doesn't matter. 3030 continue; 3031 for (const Use &U : V->uses()) { 3032 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser()); 3033 // Ignore non-instructions. 3034 if (!UserInst) 3035 continue; 3036 // Ignore instructions in other functions (as can happen with 3037 // Constants). 3038 if (UserInst->getParent()->getParent() != L->getHeader()->getParent()) 3039 continue; 3040 // Ignore instructions not dominated by the loop. 3041 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ? 3042 UserInst->getParent() : 3043 cast<PHINode>(UserInst)->getIncomingBlock( 3044 PHINode::getIncomingValueNumForOperand(U.getOperandNo())); 3045 if (!DT.dominates(L->getHeader(), UseBB)) 3046 continue; 3047 // Ignore uses which are part of other SCEV expressions, to avoid 3048 // analyzing them multiple times. 3049 if (SE.isSCEVable(UserInst->getType())) { 3050 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst)); 3051 // If the user is a no-op, look through to its uses. 3052 if (!isa<SCEVUnknown>(UserS)) 3053 continue; 3054 if (UserS == US) { 3055 Worklist.push_back( 3056 SE.getUnknown(const_cast<Instruction *>(UserInst))); 3057 continue; 3058 } 3059 } 3060 // Ignore icmp instructions which are already being analyzed. 3061 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) { 3062 unsigned OtherIdx = !U.getOperandNo(); 3063 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx)); 3064 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L)) 3065 continue; 3066 } 3067 3068 LSRFixup &LF = getNewFixup(); 3069 LF.UserInst = const_cast<Instruction *>(UserInst); 3070 LF.OperandValToReplace = U; 3071 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0); 3072 LF.LUIdx = P.first; 3073 LF.Offset = P.second; 3074 LSRUse &LU = Uses[LF.LUIdx]; 3075 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L); 3076 if (!LU.WidestFixupType || 3077 SE.getTypeSizeInBits(LU.WidestFixupType) < 3078 SE.getTypeSizeInBits(LF.OperandValToReplace->getType())) 3079 LU.WidestFixupType = LF.OperandValToReplace->getType(); 3080 InsertSupplementalFormula(US, LU, LF.LUIdx); 3081 CountRegisters(LU.Formulae.back(), Uses.size() - 1); 3082 break; 3083 } 3084 } 3085 } 3086} 3087 3088/// CollectSubexprs - Split S into subexpressions which can be pulled out into 3089/// separate registers. If C is non-null, multiply each subexpression by C. 3090/// 3091/// Return remainder expression after factoring the subexpressions captured by 3092/// Ops. If Ops is complete, return NULL. 3093static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C, 3094 SmallVectorImpl<const SCEV *> &Ops, 3095 const Loop *L, 3096 ScalarEvolution &SE, 3097 unsigned Depth = 0) { 3098 // Arbitrarily cap recursion to protect compile time. 3099 if (Depth >= 3) 3100 return S; 3101 3102 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 3103 // Break out add operands. 3104 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 3105 I != E; ++I) { 3106 const SCEV *Remainder = CollectSubexprs(*I, C, Ops, L, SE, Depth+1); 3107 if (Remainder) 3108 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder); 3109 } 3110 return 0; 3111 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 3112 // Split a non-zero base out of an addrec. 3113 if (AR->getStart()->isZero()) 3114 return S; 3115 3116 const SCEV *Remainder = CollectSubexprs(AR->getStart(), 3117 C, Ops, L, SE, Depth+1); 3118 // Split the non-zero AddRec unless it is part of a nested recurrence that 3119 // does not pertain to this loop. 3120 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) { 3121 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder); 3122 Remainder = 0; 3123 } 3124 if (Remainder != AR->getStart()) { 3125 if (!Remainder) 3126 Remainder = SE.getConstant(AR->getType(), 0); 3127 return SE.getAddRecExpr(Remainder, 3128 AR->getStepRecurrence(SE), 3129 AR->getLoop(), 3130 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW) 3131 SCEV::FlagAnyWrap); 3132 } 3133 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) { 3134 // Break (C * (a + b + c)) into C*a + C*b + C*c. 3135 if (Mul->getNumOperands() != 2) 3136 return S; 3137 if (const SCEVConstant *Op0 = 3138 dyn_cast<SCEVConstant>(Mul->getOperand(0))) { 3139 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0; 3140 const SCEV *Remainder = 3141 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1); 3142 if (Remainder) 3143 Ops.push_back(SE.getMulExpr(C, Remainder)); 3144 return 0; 3145 } 3146 } 3147 return S; 3148} 3149 3150/// GenerateReassociations - Split out subexpressions from adds and the bases of 3151/// addrecs. 3152void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx, 3153 Formula Base, 3154 unsigned Depth) { 3155 // Arbitrarily cap recursion to protect compile time. 3156 if (Depth >= 3) return; 3157 3158 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { 3159 const SCEV *BaseReg = Base.BaseRegs[i]; 3160 3161 SmallVector<const SCEV *, 8> AddOps; 3162 const SCEV *Remainder = CollectSubexprs(BaseReg, 0, AddOps, L, SE); 3163 if (Remainder) 3164 AddOps.push_back(Remainder); 3165 3166 if (AddOps.size() == 1) continue; 3167 3168 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(), 3169 JE = AddOps.end(); J != JE; ++J) { 3170 3171 // Loop-variant "unknown" values are uninteresting; we won't be able to 3172 // do anything meaningful with them. 3173 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L)) 3174 continue; 3175 3176 // Don't pull a constant into a register if the constant could be folded 3177 // into an immediate field. 3178 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind, 3179 LU.AccessTy, *J, Base.getNumRegs() > 1)) 3180 continue; 3181 3182 // Collect all operands except *J. 3183 SmallVector<const SCEV *, 8> InnerAddOps( 3184 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J); 3185 InnerAddOps.append(std::next(J), 3186 ((const SmallVector<const SCEV *, 8> &)AddOps).end()); 3187 3188 // Don't leave just a constant behind in a register if the constant could 3189 // be folded into an immediate field. 3190 if (InnerAddOps.size() == 1 && 3191 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind, 3192 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1)) 3193 continue; 3194 3195 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps); 3196 if (InnerSum->isZero()) 3197 continue; 3198 Formula F = Base; 3199 3200 // Add the remaining pieces of the add back into the new formula. 3201 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum); 3202 if (InnerSumSC && 3203 SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 && 3204 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset + 3205 InnerSumSC->getValue()->getZExtValue())) { 3206 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset + 3207 InnerSumSC->getValue()->getZExtValue(); 3208 F.BaseRegs.erase(F.BaseRegs.begin() + i); 3209 } else 3210 F.BaseRegs[i] = InnerSum; 3211 3212 // Add J as its own register, or an unfolded immediate. 3213 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J); 3214 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 && 3215 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset + 3216 SC->getValue()->getZExtValue())) 3217 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset + 3218 SC->getValue()->getZExtValue(); 3219 else 3220 F.BaseRegs.push_back(*J); 3221 3222 if (InsertFormula(LU, LUIdx, F)) 3223 // If that formula hadn't been seen before, recurse to find more like 3224 // it. 3225 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1); 3226 } 3227 } 3228} 3229 3230/// GenerateCombinations - Generate a formula consisting of all of the 3231/// loop-dominating registers added into a single register. 3232void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx, 3233 Formula Base) { 3234 // This method is only interesting on a plurality of registers. 3235 if (Base.BaseRegs.size() <= 1) return; 3236 3237 Formula F = Base; 3238 F.BaseRegs.clear(); 3239 SmallVector<const SCEV *, 4> Ops; 3240 for (SmallVectorImpl<const SCEV *>::const_iterator 3241 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) { 3242 const SCEV *BaseReg = *I; 3243 if (SE.properlyDominates(BaseReg, L->getHeader()) && 3244 !SE.hasComputableLoopEvolution(BaseReg, L)) 3245 Ops.push_back(BaseReg); 3246 else 3247 F.BaseRegs.push_back(BaseReg); 3248 } 3249 if (Ops.size() > 1) { 3250 const SCEV *Sum = SE.getAddExpr(Ops); 3251 // TODO: If Sum is zero, it probably means ScalarEvolution missed an 3252 // opportunity to fold something. For now, just ignore such cases 3253 // rather than proceed with zero in a register. 3254 if (!Sum->isZero()) { 3255 F.BaseRegs.push_back(Sum); 3256 (void)InsertFormula(LU, LUIdx, F); 3257 } 3258 } 3259} 3260 3261/// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets. 3262void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, 3263 Formula Base) { 3264 // We can't add a symbolic offset if the address already contains one. 3265 if (Base.BaseGV) return; 3266 3267 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { 3268 const SCEV *G = Base.BaseRegs[i]; 3269 GlobalValue *GV = ExtractSymbol(G, SE); 3270 if (G->isZero() || !GV) 3271 continue; 3272 Formula F = Base; 3273 F.BaseGV = GV; 3274 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F)) 3275 continue; 3276 F.BaseRegs[i] = G; 3277 (void)InsertFormula(LU, LUIdx, F); 3278 } 3279} 3280 3281/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets. 3282void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, 3283 Formula Base) { 3284 // TODO: For now, just add the min and max offset, because it usually isn't 3285 // worthwhile looking at everything inbetween. 3286 SmallVector<int64_t, 2> Worklist; 3287 Worklist.push_back(LU.MinOffset); 3288 if (LU.MaxOffset != LU.MinOffset) 3289 Worklist.push_back(LU.MaxOffset); 3290 3291 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { 3292 const SCEV *G = Base.BaseRegs[i]; 3293 3294 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(), 3295 E = Worklist.end(); I != E; ++I) { 3296 Formula F = Base; 3297 F.BaseOffset = (uint64_t)Base.BaseOffset - *I; 3298 if (isLegalUse(TTI, LU.MinOffset - *I, LU.MaxOffset - *I, LU.Kind, 3299 LU.AccessTy, F)) { 3300 // Add the offset to the base register. 3301 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G); 3302 // If it cancelled out, drop the base register, otherwise update it. 3303 if (NewG->isZero()) { 3304 std::swap(F.BaseRegs[i], F.BaseRegs.back()); 3305 F.BaseRegs.pop_back(); 3306 } else 3307 F.BaseRegs[i] = NewG; 3308 3309 (void)InsertFormula(LU, LUIdx, F); 3310 } 3311 } 3312 3313 int64_t Imm = ExtractImmediate(G, SE); 3314 if (G->isZero() || Imm == 0) 3315 continue; 3316 Formula F = Base; 3317 F.BaseOffset = (uint64_t)F.BaseOffset + Imm; 3318 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F)) 3319 continue; 3320 F.BaseRegs[i] = G; 3321 (void)InsertFormula(LU, LUIdx, F); 3322 } 3323} 3324 3325/// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up 3326/// the comparison. For example, x == y -> x*c == y*c. 3327void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, 3328 Formula Base) { 3329 if (LU.Kind != LSRUse::ICmpZero) return; 3330 3331 // Determine the integer type for the base formula. 3332 Type *IntTy = Base.getType(); 3333 if (!IntTy) return; 3334 if (SE.getTypeSizeInBits(IntTy) > 64) return; 3335 3336 // Don't do this if there is more than one offset. 3337 if (LU.MinOffset != LU.MaxOffset) return; 3338 3339 assert(!Base.BaseGV && "ICmpZero use is not legal!"); 3340 3341 // Check each interesting stride. 3342 for (SmallSetVector<int64_t, 8>::const_iterator 3343 I = Factors.begin(), E = Factors.end(); I != E; ++I) { 3344 int64_t Factor = *I; 3345 3346 // Check that the multiplication doesn't overflow. 3347 if (Base.BaseOffset == INT64_MIN && Factor == -1) 3348 continue; 3349 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor; 3350 if (NewBaseOffset / Factor != Base.BaseOffset) 3351 continue; 3352 // If the offset will be truncated at this use, check that it is in bounds. 3353 if (!IntTy->isPointerTy() && 3354 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset)) 3355 continue; 3356 3357 // Check that multiplying with the use offset doesn't overflow. 3358 int64_t Offset = LU.MinOffset; 3359 if (Offset == INT64_MIN && Factor == -1) 3360 continue; 3361 Offset = (uint64_t)Offset * Factor; 3362 if (Offset / Factor != LU.MinOffset) 3363 continue; 3364 // If the offset will be truncated at this use, check that it is in bounds. 3365 if (!IntTy->isPointerTy() && 3366 !ConstantInt::isValueValidForType(IntTy, Offset)) 3367 continue; 3368 3369 Formula F = Base; 3370 F.BaseOffset = NewBaseOffset; 3371 3372 // Check that this scale is legal. 3373 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F)) 3374 continue; 3375 3376 // Compensate for the use having MinOffset built into it. 3377 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset; 3378 3379 const SCEV *FactorS = SE.getConstant(IntTy, Factor); 3380 3381 // Check that multiplying with each base register doesn't overflow. 3382 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) { 3383 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS); 3384 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i]) 3385 goto next; 3386 } 3387 3388 // Check that multiplying with the scaled register doesn't overflow. 3389 if (F.ScaledReg) { 3390 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS); 3391 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg) 3392 continue; 3393 } 3394 3395 // Check that multiplying with the unfolded offset doesn't overflow. 3396 if (F.UnfoldedOffset != 0) { 3397 if (F.UnfoldedOffset == INT64_MIN && Factor == -1) 3398 continue; 3399 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor; 3400 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset) 3401 continue; 3402 // If the offset will be truncated, check that it is in bounds. 3403 if (!IntTy->isPointerTy() && 3404 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset)) 3405 continue; 3406 } 3407 3408 // If we make it here and it's legal, add it. 3409 (void)InsertFormula(LU, LUIdx, F); 3410 next:; 3411 } 3412} 3413 3414/// GenerateScales - Generate stride factor reuse formulae by making use of 3415/// scaled-offset address modes, for example. 3416void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) { 3417 // Determine the integer type for the base formula. 3418 Type *IntTy = Base.getType(); 3419 if (!IntTy) return; 3420 3421 // If this Formula already has a scaled register, we can't add another one. 3422 if (Base.Scale != 0) return; 3423 3424 // Check each interesting stride. 3425 for (SmallSetVector<int64_t, 8>::const_iterator 3426 I = Factors.begin(), E = Factors.end(); I != E; ++I) { 3427 int64_t Factor = *I; 3428 3429 Base.Scale = Factor; 3430 Base.HasBaseReg = Base.BaseRegs.size() > 1; 3431 // Check whether this scale is going to be legal. 3432 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, 3433 Base)) { 3434 // As a special-case, handle special out-of-loop Basic users specially. 3435 // TODO: Reconsider this special case. 3436 if (LU.Kind == LSRUse::Basic && 3437 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special, 3438 LU.AccessTy, Base) && 3439 LU.AllFixupsOutsideLoop) 3440 LU.Kind = LSRUse::Special; 3441 else 3442 continue; 3443 } 3444 // For an ICmpZero, negating a solitary base register won't lead to 3445 // new solutions. 3446 if (LU.Kind == LSRUse::ICmpZero && 3447 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV) 3448 continue; 3449 // For each addrec base reg, apply the scale, if possible. 3450 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) 3451 if (const SCEVAddRecExpr *AR = 3452 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) { 3453 const SCEV *FactorS = SE.getConstant(IntTy, Factor); 3454 if (FactorS->isZero()) 3455 continue; 3456 // Divide out the factor, ignoring high bits, since we'll be 3457 // scaling the value back up in the end. 3458 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) { 3459 // TODO: This could be optimized to avoid all the copying. 3460 Formula F = Base; 3461 F.ScaledReg = Quotient; 3462 F.DeleteBaseReg(F.BaseRegs[i]); 3463 (void)InsertFormula(LU, LUIdx, F); 3464 } 3465 } 3466 } 3467} 3468 3469/// GenerateTruncates - Generate reuse formulae from different IV types. 3470void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) { 3471 // Don't bother truncating symbolic values. 3472 if (Base.BaseGV) return; 3473 3474 // Determine the integer type for the base formula. 3475 Type *DstTy = Base.getType(); 3476 if (!DstTy) return; 3477 DstTy = SE.getEffectiveSCEVType(DstTy); 3478 3479 for (SmallSetVector<Type *, 4>::const_iterator 3480 I = Types.begin(), E = Types.end(); I != E; ++I) { 3481 Type *SrcTy = *I; 3482 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) { 3483 Formula F = Base; 3484 3485 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I); 3486 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(), 3487 JE = F.BaseRegs.end(); J != JE; ++J) 3488 *J = SE.getAnyExtendExpr(*J, SrcTy); 3489 3490 // TODO: This assumes we've done basic processing on all uses and 3491 // have an idea what the register usage is. 3492 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses)) 3493 continue; 3494 3495 (void)InsertFormula(LU, LUIdx, F); 3496 } 3497 } 3498} 3499 3500namespace { 3501 3502/// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to 3503/// defer modifications so that the search phase doesn't have to worry about 3504/// the data structures moving underneath it. 3505struct WorkItem { 3506 size_t LUIdx; 3507 int64_t Imm; 3508 const SCEV *OrigReg; 3509 3510 WorkItem(size_t LI, int64_t I, const SCEV *R) 3511 : LUIdx(LI), Imm(I), OrigReg(R) {} 3512 3513 void print(raw_ostream &OS) const; 3514 void dump() const; 3515}; 3516 3517} 3518 3519void WorkItem::print(raw_ostream &OS) const { 3520 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx 3521 << " , add offset " << Imm; 3522} 3523 3524#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 3525void WorkItem::dump() const { 3526 print(errs()); errs() << '\n'; 3527} 3528#endif 3529 3530/// GenerateCrossUseConstantOffsets - Look for registers which are a constant 3531/// distance apart and try to form reuse opportunities between them. 3532void LSRInstance::GenerateCrossUseConstantOffsets() { 3533 // Group the registers by their value without any added constant offset. 3534 typedef std::map<int64_t, const SCEV *> ImmMapTy; 3535 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy; 3536 RegMapTy Map; 3537 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap; 3538 SmallVector<const SCEV *, 8> Sequence; 3539 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end(); 3540 I != E; ++I) { 3541 const SCEV *Reg = *I; 3542 int64_t Imm = ExtractImmediate(Reg, SE); 3543 std::pair<RegMapTy::iterator, bool> Pair = 3544 Map.insert(std::make_pair(Reg, ImmMapTy())); 3545 if (Pair.second) 3546 Sequence.push_back(Reg); 3547 Pair.first->second.insert(std::make_pair(Imm, *I)); 3548 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I); 3549 } 3550 3551 // Now examine each set of registers with the same base value. Build up 3552 // a list of work to do and do the work in a separate step so that we're 3553 // not adding formulae and register counts while we're searching. 3554 SmallVector<WorkItem, 32> WorkItems; 3555 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems; 3556 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(), 3557 E = Sequence.end(); I != E; ++I) { 3558 const SCEV *Reg = *I; 3559 const ImmMapTy &Imms = Map.find(Reg)->second; 3560 3561 // It's not worthwhile looking for reuse if there's only one offset. 3562 if (Imms.size() == 1) 3563 continue; 3564 3565 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':'; 3566 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end(); 3567 J != JE; ++J) 3568 dbgs() << ' ' << J->first; 3569 dbgs() << '\n'); 3570 3571 // Examine each offset. 3572 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end(); 3573 J != JE; ++J) { 3574 const SCEV *OrigReg = J->second; 3575 3576 int64_t JImm = J->first; 3577 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg); 3578 3579 if (!isa<SCEVConstant>(OrigReg) && 3580 UsedByIndicesMap[Reg].count() == 1) { 3581 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n'); 3582 continue; 3583 } 3584 3585 // Conservatively examine offsets between this orig reg a few selected 3586 // other orig regs. 3587 ImmMapTy::const_iterator OtherImms[] = { 3588 Imms.begin(), std::prev(Imms.end()), 3589 Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) / 3590 2) 3591 }; 3592 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) { 3593 ImmMapTy::const_iterator M = OtherImms[i]; 3594 if (M == J || M == JE) continue; 3595 3596 // Compute the difference between the two. 3597 int64_t Imm = (uint64_t)JImm - M->first; 3598 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1; 3599 LUIdx = UsedByIndices.find_next(LUIdx)) 3600 // Make a memo of this use, offset, and register tuple. 3601 if (UniqueItems.insert(std::make_pair(LUIdx, Imm))) 3602 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg)); 3603 } 3604 } 3605 } 3606 3607 Map.clear(); 3608 Sequence.clear(); 3609 UsedByIndicesMap.clear(); 3610 UniqueItems.clear(); 3611 3612 // Now iterate through the worklist and add new formulae. 3613 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(), 3614 E = WorkItems.end(); I != E; ++I) { 3615 const WorkItem &WI = *I; 3616 size_t LUIdx = WI.LUIdx; 3617 LSRUse &LU = Uses[LUIdx]; 3618 int64_t Imm = WI.Imm; 3619 const SCEV *OrigReg = WI.OrigReg; 3620 3621 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType()); 3622 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm)); 3623 unsigned BitWidth = SE.getTypeSizeInBits(IntTy); 3624 3625 // TODO: Use a more targeted data structure. 3626 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) { 3627 const Formula &F = LU.Formulae[L]; 3628 // Use the immediate in the scaled register. 3629 if (F.ScaledReg == OrigReg) { 3630 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale; 3631 // Don't create 50 + reg(-50). 3632 if (F.referencesReg(SE.getSCEV( 3633 ConstantInt::get(IntTy, -(uint64_t)Offset)))) 3634 continue; 3635 Formula NewF = F; 3636 NewF.BaseOffset = Offset; 3637 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, 3638 NewF)) 3639 continue; 3640 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg); 3641 3642 // If the new scale is a constant in a register, and adding the constant 3643 // value to the immediate would produce a value closer to zero than the 3644 // immediate itself, then the formula isn't worthwhile. 3645 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg)) 3646 if (C->getValue()->isNegative() != 3647 (NewF.BaseOffset < 0) && 3648 (C->getValue()->getValue().abs() * APInt(BitWidth, F.Scale)) 3649 .ule(abs64(NewF.BaseOffset))) 3650 continue; 3651 3652 // OK, looks good. 3653 (void)InsertFormula(LU, LUIdx, NewF); 3654 } else { 3655 // Use the immediate in a base register. 3656 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) { 3657 const SCEV *BaseReg = F.BaseRegs[N]; 3658 if (BaseReg != OrigReg) 3659 continue; 3660 Formula NewF = F; 3661 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm; 3662 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, 3663 LU.Kind, LU.AccessTy, NewF)) { 3664 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm)) 3665 continue; 3666 NewF = F; 3667 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm; 3668 } 3669 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg); 3670 3671 // If the new formula has a constant in a register, and adding the 3672 // constant value to the immediate would produce a value closer to 3673 // zero than the immediate itself, then the formula isn't worthwhile. 3674 for (SmallVectorImpl<const SCEV *>::const_iterator 3675 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end(); 3676 J != JE; ++J) 3677 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J)) 3678 if ((C->getValue()->getValue() + NewF.BaseOffset).abs().slt( 3679 abs64(NewF.BaseOffset)) && 3680 (C->getValue()->getValue() + 3681 NewF.BaseOffset).countTrailingZeros() >= 3682 countTrailingZeros<uint64_t>(NewF.BaseOffset)) 3683 goto skip_formula; 3684 3685 // Ok, looks good. 3686 (void)InsertFormula(LU, LUIdx, NewF); 3687 break; 3688 skip_formula:; 3689 } 3690 } 3691 } 3692 } 3693} 3694 3695/// GenerateAllReuseFormulae - Generate formulae for each use. 3696void 3697LSRInstance::GenerateAllReuseFormulae() { 3698 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan 3699 // queries are more precise. 3700 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3701 LSRUse &LU = Uses[LUIdx]; 3702 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3703 GenerateReassociations(LU, LUIdx, LU.Formulae[i]); 3704 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3705 GenerateCombinations(LU, LUIdx, LU.Formulae[i]); 3706 } 3707 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3708 LSRUse &LU = Uses[LUIdx]; 3709 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3710 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]); 3711 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3712 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]); 3713 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3714 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]); 3715 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3716 GenerateScales(LU, LUIdx, LU.Formulae[i]); 3717 } 3718 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3719 LSRUse &LU = Uses[LUIdx]; 3720 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 3721 GenerateTruncates(LU, LUIdx, LU.Formulae[i]); 3722 } 3723 3724 GenerateCrossUseConstantOffsets(); 3725 3726 DEBUG(dbgs() << "\n" 3727 "After generating reuse formulae:\n"; 3728 print_uses(dbgs())); 3729} 3730 3731/// If there are multiple formulae with the same set of registers used 3732/// by other uses, pick the best one and delete the others. 3733void LSRInstance::FilterOutUndesirableDedicatedRegisters() { 3734 DenseSet<const SCEV *> VisitedRegs; 3735 SmallPtrSet<const SCEV *, 16> Regs; 3736 SmallPtrSet<const SCEV *, 16> LoserRegs; 3737#ifndef NDEBUG 3738 bool ChangedFormulae = false; 3739#endif 3740 3741 // Collect the best formula for each unique set of shared registers. This 3742 // is reset for each use. 3743 typedef DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo> 3744 BestFormulaeTy; 3745 BestFormulaeTy BestFormulae; 3746 3747 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3748 LSRUse &LU = Uses[LUIdx]; 3749 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n'); 3750 3751 bool Any = false; 3752 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); 3753 FIdx != NumForms; ++FIdx) { 3754 Formula &F = LU.Formulae[FIdx]; 3755 3756 // Some formulas are instant losers. For example, they may depend on 3757 // nonexistent AddRecs from other loops. These need to be filtered 3758 // immediately, otherwise heuristics could choose them over others leading 3759 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here 3760 // avoids the need to recompute this information across formulae using the 3761 // same bad AddRec. Passing LoserRegs is also essential unless we remove 3762 // the corresponding bad register from the Regs set. 3763 Cost CostF; 3764 Regs.clear(); 3765 CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, LU.Offsets, SE, DT, LU, 3766 &LoserRegs); 3767 if (CostF.isLoser()) { 3768 // During initial formula generation, undesirable formulae are generated 3769 // by uses within other loops that have some non-trivial address mode or 3770 // use the postinc form of the IV. LSR needs to provide these formulae 3771 // as the basis of rediscovering the desired formula that uses an AddRec 3772 // corresponding to the existing phi. Once all formulae have been 3773 // generated, these initial losers may be pruned. 3774 DEBUG(dbgs() << " Filtering loser "; F.print(dbgs()); 3775 dbgs() << "\n"); 3776 } 3777 else { 3778 SmallVector<const SCEV *, 4> Key; 3779 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(), 3780 JE = F.BaseRegs.end(); J != JE; ++J) { 3781 const SCEV *Reg = *J; 3782 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx)) 3783 Key.push_back(Reg); 3784 } 3785 if (F.ScaledReg && 3786 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx)) 3787 Key.push_back(F.ScaledReg); 3788 // Unstable sort by host order ok, because this is only used for 3789 // uniquifying. 3790 std::sort(Key.begin(), Key.end()); 3791 3792 std::pair<BestFormulaeTy::const_iterator, bool> P = 3793 BestFormulae.insert(std::make_pair(Key, FIdx)); 3794 if (P.second) 3795 continue; 3796 3797 Formula &Best = LU.Formulae[P.first->second]; 3798 3799 Cost CostBest; 3800 Regs.clear(); 3801 CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, LU.Offsets, SE, 3802 DT, LU); 3803 if (CostF < CostBest) 3804 std::swap(F, Best); 3805 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs()); 3806 dbgs() << "\n" 3807 " in favor of formula "; Best.print(dbgs()); 3808 dbgs() << '\n'); 3809 } 3810#ifndef NDEBUG 3811 ChangedFormulae = true; 3812#endif 3813 LU.DeleteFormula(F); 3814 --FIdx; 3815 --NumForms; 3816 Any = true; 3817 } 3818 3819 // Now that we've filtered out some formulae, recompute the Regs set. 3820 if (Any) 3821 LU.RecomputeRegs(LUIdx, RegUses); 3822 3823 // Reset this to prepare for the next use. 3824 BestFormulae.clear(); 3825 } 3826 3827 DEBUG(if (ChangedFormulae) { 3828 dbgs() << "\n" 3829 "After filtering out undesirable candidates:\n"; 3830 print_uses(dbgs()); 3831 }); 3832} 3833 3834// This is a rough guess that seems to work fairly well. 3835static const size_t ComplexityLimit = UINT16_MAX; 3836 3837/// EstimateSearchSpaceComplexity - Estimate the worst-case number of 3838/// solutions the solver might have to consider. It almost never considers 3839/// this many solutions because it prune the search space, but the pruning 3840/// isn't always sufficient. 3841size_t LSRInstance::EstimateSearchSpaceComplexity() const { 3842 size_t Power = 1; 3843 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), 3844 E = Uses.end(); I != E; ++I) { 3845 size_t FSize = I->Formulae.size(); 3846 if (FSize >= ComplexityLimit) { 3847 Power = ComplexityLimit; 3848 break; 3849 } 3850 Power *= FSize; 3851 if (Power >= ComplexityLimit) 3852 break; 3853 } 3854 return Power; 3855} 3856 3857/// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset 3858/// of the registers of another formula, it won't help reduce register 3859/// pressure (though it may not necessarily hurt register pressure); remove 3860/// it to simplify the system. 3861void LSRInstance::NarrowSearchSpaceByDetectingSupersets() { 3862 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 3863 DEBUG(dbgs() << "The search space is too complex.\n"); 3864 3865 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae " 3866 "which use a superset of registers used by other " 3867 "formulae.\n"); 3868 3869 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3870 LSRUse &LU = Uses[LUIdx]; 3871 bool Any = false; 3872 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { 3873 Formula &F = LU.Formulae[i]; 3874 // Look for a formula with a constant or GV in a register. If the use 3875 // also has a formula with that same value in an immediate field, 3876 // delete the one that uses a register. 3877 for (SmallVectorImpl<const SCEV *>::const_iterator 3878 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) { 3879 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) { 3880 Formula NewF = F; 3881 NewF.BaseOffset += C->getValue()->getSExtValue(); 3882 NewF.BaseRegs.erase(NewF.BaseRegs.begin() + 3883 (I - F.BaseRegs.begin())); 3884 if (LU.HasFormulaWithSameRegs(NewF)) { 3885 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); 3886 LU.DeleteFormula(F); 3887 --i; 3888 --e; 3889 Any = true; 3890 break; 3891 } 3892 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) { 3893 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) 3894 if (!F.BaseGV) { 3895 Formula NewF = F; 3896 NewF.BaseGV = GV; 3897 NewF.BaseRegs.erase(NewF.BaseRegs.begin() + 3898 (I - F.BaseRegs.begin())); 3899 if (LU.HasFormulaWithSameRegs(NewF)) { 3900 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); 3901 dbgs() << '\n'); 3902 LU.DeleteFormula(F); 3903 --i; 3904 --e; 3905 Any = true; 3906 break; 3907 } 3908 } 3909 } 3910 } 3911 } 3912 if (Any) 3913 LU.RecomputeRegs(LUIdx, RegUses); 3914 } 3915 3916 DEBUG(dbgs() << "After pre-selection:\n"; 3917 print_uses(dbgs())); 3918 } 3919} 3920 3921/// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers 3922/// for expressions like A, A+1, A+2, etc., allocate a single register for 3923/// them. 3924void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() { 3925 if (EstimateSearchSpaceComplexity() < ComplexityLimit) 3926 return; 3927 3928 DEBUG(dbgs() << "The search space is too complex.\n" 3929 "Narrowing the search space by assuming that uses separated " 3930 "by a constant offset will use the same registers.\n"); 3931 3932 // This is especially useful for unrolled loops. 3933 3934 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 3935 LSRUse &LU = Uses[LUIdx]; 3936 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), 3937 E = LU.Formulae.end(); I != E; ++I) { 3938 const Formula &F = *I; 3939 if (F.BaseOffset == 0 || F.Scale != 0) 3940 continue; 3941 3942 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU); 3943 if (!LUThatHas) 3944 continue; 3945 3946 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false, 3947 LU.Kind, LU.AccessTy)) 3948 continue; 3949 3950 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n'); 3951 3952 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop; 3953 3954 // Update the relocs to reference the new use. 3955 for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(), 3956 E = Fixups.end(); I != E; ++I) { 3957 LSRFixup &Fixup = *I; 3958 if (Fixup.LUIdx == LUIdx) { 3959 Fixup.LUIdx = LUThatHas - &Uses.front(); 3960 Fixup.Offset += F.BaseOffset; 3961 // Add the new offset to LUThatHas' offset list. 3962 if (LUThatHas->Offsets.back() != Fixup.Offset) { 3963 LUThatHas->Offsets.push_back(Fixup.Offset); 3964 if (Fixup.Offset > LUThatHas->MaxOffset) 3965 LUThatHas->MaxOffset = Fixup.Offset; 3966 if (Fixup.Offset < LUThatHas->MinOffset) 3967 LUThatHas->MinOffset = Fixup.Offset; 3968 } 3969 DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n'); 3970 } 3971 if (Fixup.LUIdx == NumUses-1) 3972 Fixup.LUIdx = LUIdx; 3973 } 3974 3975 // Delete formulae from the new use which are no longer legal. 3976 bool Any = false; 3977 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) { 3978 Formula &F = LUThatHas->Formulae[i]; 3979 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset, 3980 LUThatHas->Kind, LUThatHas->AccessTy, F)) { 3981 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); 3982 dbgs() << '\n'); 3983 LUThatHas->DeleteFormula(F); 3984 --i; 3985 --e; 3986 Any = true; 3987 } 3988 } 3989 3990 if (Any) 3991 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses); 3992 3993 // Delete the old use. 3994 DeleteUse(LU, LUIdx); 3995 --LUIdx; 3996 --NumUses; 3997 break; 3998 } 3999 } 4000 4001 DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs())); 4002} 4003 4004/// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call 4005/// FilterOutUndesirableDedicatedRegisters again, if necessary, now that 4006/// we've done more filtering, as it may be able to find more formulae to 4007/// eliminate. 4008void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){ 4009 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 4010 DEBUG(dbgs() << "The search space is too complex.\n"); 4011 4012 DEBUG(dbgs() << "Narrowing the search space by re-filtering out " 4013 "undesirable dedicated registers.\n"); 4014 4015 FilterOutUndesirableDedicatedRegisters(); 4016 4017 DEBUG(dbgs() << "After pre-selection:\n"; 4018 print_uses(dbgs())); 4019 } 4020} 4021 4022/// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely 4023/// to be profitable, and then in any use which has any reference to that 4024/// register, delete all formulae which do not reference that register. 4025void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() { 4026 // With all other options exhausted, loop until the system is simple 4027 // enough to handle. 4028 SmallPtrSet<const SCEV *, 4> Taken; 4029 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 4030 // Ok, we have too many of formulae on our hands to conveniently handle. 4031 // Use a rough heuristic to thin out the list. 4032 DEBUG(dbgs() << "The search space is too complex.\n"); 4033 4034 // Pick the register which is used by the most LSRUses, which is likely 4035 // to be a good reuse register candidate. 4036 const SCEV *Best = 0; 4037 unsigned BestNum = 0; 4038 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end(); 4039 I != E; ++I) { 4040 const SCEV *Reg = *I; 4041 if (Taken.count(Reg)) 4042 continue; 4043 if (!Best) 4044 Best = Reg; 4045 else { 4046 unsigned Count = RegUses.getUsedByIndices(Reg).count(); 4047 if (Count > BestNum) { 4048 Best = Reg; 4049 BestNum = Count; 4050 } 4051 } 4052 } 4053 4054 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best 4055 << " will yield profitable reuse.\n"); 4056 Taken.insert(Best); 4057 4058 // In any use with formulae which references this register, delete formulae 4059 // which don't reference it. 4060 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 4061 LSRUse &LU = Uses[LUIdx]; 4062 if (!LU.Regs.count(Best)) continue; 4063 4064 bool Any = false; 4065 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { 4066 Formula &F = LU.Formulae[i]; 4067 if (!F.referencesReg(Best)) { 4068 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); 4069 LU.DeleteFormula(F); 4070 --e; 4071 --i; 4072 Any = true; 4073 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?"); 4074 continue; 4075 } 4076 } 4077 4078 if (Any) 4079 LU.RecomputeRegs(LUIdx, RegUses); 4080 } 4081 4082 DEBUG(dbgs() << "After pre-selection:\n"; 4083 print_uses(dbgs())); 4084 } 4085} 4086 4087/// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of 4088/// formulae to choose from, use some rough heuristics to prune down the number 4089/// of formulae. This keeps the main solver from taking an extraordinary amount 4090/// of time in some worst-case scenarios. 4091void LSRInstance::NarrowSearchSpaceUsingHeuristics() { 4092 NarrowSearchSpaceByDetectingSupersets(); 4093 NarrowSearchSpaceByCollapsingUnrolledCode(); 4094 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(); 4095 NarrowSearchSpaceByPickingWinnerRegs(); 4096} 4097 4098/// SolveRecurse - This is the recursive solver. 4099void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution, 4100 Cost &SolutionCost, 4101 SmallVectorImpl<const Formula *> &Workspace, 4102 const Cost &CurCost, 4103 const SmallPtrSet<const SCEV *, 16> &CurRegs, 4104 DenseSet<const SCEV *> &VisitedRegs) const { 4105 // Some ideas: 4106 // - prune more: 4107 // - use more aggressive filtering 4108 // - sort the formula so that the most profitable solutions are found first 4109 // - sort the uses too 4110 // - search faster: 4111 // - don't compute a cost, and then compare. compare while computing a cost 4112 // and bail early. 4113 // - track register sets with SmallBitVector 4114 4115 const LSRUse &LU = Uses[Workspace.size()]; 4116 4117 // If this use references any register that's already a part of the 4118 // in-progress solution, consider it a requirement that a formula must 4119 // reference that register in order to be considered. This prunes out 4120 // unprofitable searching. 4121 SmallSetVector<const SCEV *, 4> ReqRegs; 4122 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(), 4123 E = CurRegs.end(); I != E; ++I) 4124 if (LU.Regs.count(*I)) 4125 ReqRegs.insert(*I); 4126 4127 SmallPtrSet<const SCEV *, 16> NewRegs; 4128 Cost NewCost; 4129 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), 4130 E = LU.Formulae.end(); I != E; ++I) { 4131 const Formula &F = *I; 4132 4133 // Ignore formulae which do not use any of the required registers. 4134 bool SatisfiedReqReg = true; 4135 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(), 4136 JE = ReqRegs.end(); J != JE; ++J) { 4137 const SCEV *Reg = *J; 4138 if ((!F.ScaledReg || F.ScaledReg != Reg) && 4139 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) == 4140 F.BaseRegs.end()) { 4141 SatisfiedReqReg = false; 4142 break; 4143 } 4144 } 4145 if (!SatisfiedReqReg) { 4146 // If none of the formulae satisfied the required registers, then we could 4147 // clear ReqRegs and try again. Currently, we simply give up in this case. 4148 continue; 4149 } 4150 4151 // Evaluate the cost of the current formula. If it's already worse than 4152 // the current best, prune the search at that point. 4153 NewCost = CurCost; 4154 NewRegs = CurRegs; 4155 NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT, 4156 LU); 4157 if (NewCost < SolutionCost) { 4158 Workspace.push_back(&F); 4159 if (Workspace.size() != Uses.size()) { 4160 SolveRecurse(Solution, SolutionCost, Workspace, NewCost, 4161 NewRegs, VisitedRegs); 4162 if (F.getNumRegs() == 1 && Workspace.size() == 1) 4163 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]); 4164 } else { 4165 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs()); 4166 dbgs() << ".\n Regs:"; 4167 for (SmallPtrSet<const SCEV *, 16>::const_iterator 4168 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I) 4169 dbgs() << ' ' << **I; 4170 dbgs() << '\n'); 4171 4172 SolutionCost = NewCost; 4173 Solution = Workspace; 4174 } 4175 Workspace.pop_back(); 4176 } 4177 } 4178} 4179 4180/// Solve - Choose one formula from each use. Return the results in the given 4181/// Solution vector. 4182void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const { 4183 SmallVector<const Formula *, 8> Workspace; 4184 Cost SolutionCost; 4185 SolutionCost.Lose(); 4186 Cost CurCost; 4187 SmallPtrSet<const SCEV *, 16> CurRegs; 4188 DenseSet<const SCEV *> VisitedRegs; 4189 Workspace.reserve(Uses.size()); 4190 4191 // SolveRecurse does all the work. 4192 SolveRecurse(Solution, SolutionCost, Workspace, CurCost, 4193 CurRegs, VisitedRegs); 4194 if (Solution.empty()) { 4195 DEBUG(dbgs() << "\nNo Satisfactory Solution\n"); 4196 return; 4197 } 4198 4199 // Ok, we've now made all our decisions. 4200 DEBUG(dbgs() << "\n" 4201 "The chosen solution requires "; SolutionCost.print(dbgs()); 4202 dbgs() << ":\n"; 4203 for (size_t i = 0, e = Uses.size(); i != e; ++i) { 4204 dbgs() << " "; 4205 Uses[i].print(dbgs()); 4206 dbgs() << "\n" 4207 " "; 4208 Solution[i]->print(dbgs()); 4209 dbgs() << '\n'; 4210 }); 4211 4212 assert(Solution.size() == Uses.size() && "Malformed solution!"); 4213} 4214 4215/// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up 4216/// the dominator tree far as we can go while still being dominated by the 4217/// input positions. This helps canonicalize the insert position, which 4218/// encourages sharing. 4219BasicBlock::iterator 4220LSRInstance::HoistInsertPosition(BasicBlock::iterator IP, 4221 const SmallVectorImpl<Instruction *> &Inputs) 4222 const { 4223 for (;;) { 4224 const Loop *IPLoop = LI.getLoopFor(IP->getParent()); 4225 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0; 4226 4227 BasicBlock *IDom; 4228 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) { 4229 if (!Rung) return IP; 4230 Rung = Rung->getIDom(); 4231 if (!Rung) return IP; 4232 IDom = Rung->getBlock(); 4233 4234 // Don't climb into a loop though. 4235 const Loop *IDomLoop = LI.getLoopFor(IDom); 4236 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0; 4237 if (IDomDepth <= IPLoopDepth && 4238 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop)) 4239 break; 4240 } 4241 4242 bool AllDominate = true; 4243 Instruction *BetterPos = 0; 4244 Instruction *Tentative = IDom->getTerminator(); 4245 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(), 4246 E = Inputs.end(); I != E; ++I) { 4247 Instruction *Inst = *I; 4248 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) { 4249 AllDominate = false; 4250 break; 4251 } 4252 // Attempt to find an insert position in the middle of the block, 4253 // instead of at the end, so that it can be used for other expansions. 4254 if (IDom == Inst->getParent() && 4255 (!BetterPos || !DT.dominates(Inst, BetterPos))) 4256 BetterPos = std::next(BasicBlock::iterator(Inst)); 4257 } 4258 if (!AllDominate) 4259 break; 4260 if (BetterPos) 4261 IP = BetterPos; 4262 else 4263 IP = Tentative; 4264 } 4265 4266 return IP; 4267} 4268 4269/// AdjustInsertPositionForExpand - Determine an input position which will be 4270/// dominated by the operands and which will dominate the result. 4271BasicBlock::iterator 4272LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP, 4273 const LSRFixup &LF, 4274 const LSRUse &LU, 4275 SCEVExpander &Rewriter) const { 4276 // Collect some instructions which must be dominated by the 4277 // expanding replacement. These must be dominated by any operands that 4278 // will be required in the expansion. 4279 SmallVector<Instruction *, 4> Inputs; 4280 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace)) 4281 Inputs.push_back(I); 4282 if (LU.Kind == LSRUse::ICmpZero) 4283 if (Instruction *I = 4284 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1))) 4285 Inputs.push_back(I); 4286 if (LF.PostIncLoops.count(L)) { 4287 if (LF.isUseFullyOutsideLoop(L)) 4288 Inputs.push_back(L->getLoopLatch()->getTerminator()); 4289 else 4290 Inputs.push_back(IVIncInsertPos); 4291 } 4292 // The expansion must also be dominated by the increment positions of any 4293 // loops it for which it is using post-inc mode. 4294 for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(), 4295 E = LF.PostIncLoops.end(); I != E; ++I) { 4296 const Loop *PIL = *I; 4297 if (PIL == L) continue; 4298 4299 // Be dominated by the loop exit. 4300 SmallVector<BasicBlock *, 4> ExitingBlocks; 4301 PIL->getExitingBlocks(ExitingBlocks); 4302 if (!ExitingBlocks.empty()) { 4303 BasicBlock *BB = ExitingBlocks[0]; 4304 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i) 4305 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]); 4306 Inputs.push_back(BB->getTerminator()); 4307 } 4308 } 4309 4310 assert(!isa<PHINode>(LowestIP) && !isa<LandingPadInst>(LowestIP) 4311 && !isa<DbgInfoIntrinsic>(LowestIP) && 4312 "Insertion point must be a normal instruction"); 4313 4314 // Then, climb up the immediate dominator tree as far as we can go while 4315 // still being dominated by the input positions. 4316 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs); 4317 4318 // Don't insert instructions before PHI nodes. 4319 while (isa<PHINode>(IP)) ++IP; 4320 4321 // Ignore landingpad instructions. 4322 while (isa<LandingPadInst>(IP)) ++IP; 4323 4324 // Ignore debug intrinsics. 4325 while (isa<DbgInfoIntrinsic>(IP)) ++IP; 4326 4327 // Set IP below instructions recently inserted by SCEVExpander. This keeps the 4328 // IP consistent across expansions and allows the previously inserted 4329 // instructions to be reused by subsequent expansion. 4330 while (Rewriter.isInsertedInstruction(IP) && IP != LowestIP) ++IP; 4331 4332 return IP; 4333} 4334 4335/// Expand - Emit instructions for the leading candidate expression for this 4336/// LSRUse (this is called "expanding"). 4337Value *LSRInstance::Expand(const LSRFixup &LF, 4338 const Formula &F, 4339 BasicBlock::iterator IP, 4340 SCEVExpander &Rewriter, 4341 SmallVectorImpl<WeakVH> &DeadInsts) const { 4342 const LSRUse &LU = Uses[LF.LUIdx]; 4343 if (LU.RigidFormula) 4344 return LF.OperandValToReplace; 4345 4346 // Determine an input position which will be dominated by the operands and 4347 // which will dominate the result. 4348 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter); 4349 4350 // Inform the Rewriter if we have a post-increment use, so that it can 4351 // perform an advantageous expansion. 4352 Rewriter.setPostInc(LF.PostIncLoops); 4353 4354 // This is the type that the user actually needs. 4355 Type *OpTy = LF.OperandValToReplace->getType(); 4356 // This will be the type that we'll initially expand to. 4357 Type *Ty = F.getType(); 4358 if (!Ty) 4359 // No type known; just expand directly to the ultimate type. 4360 Ty = OpTy; 4361 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy)) 4362 // Expand directly to the ultimate type if it's the right size. 4363 Ty = OpTy; 4364 // This is the type to do integer arithmetic in. 4365 Type *IntTy = SE.getEffectiveSCEVType(Ty); 4366 4367 // Build up a list of operands to add together to form the full base. 4368 SmallVector<const SCEV *, 8> Ops; 4369 4370 // Expand the BaseRegs portion. 4371 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), 4372 E = F.BaseRegs.end(); I != E; ++I) { 4373 const SCEV *Reg = *I; 4374 assert(!Reg->isZero() && "Zero allocated in a base register!"); 4375 4376 // If we're expanding for a post-inc user, make the post-inc adjustment. 4377 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); 4378 Reg = TransformForPostIncUse(Denormalize, Reg, 4379 LF.UserInst, LF.OperandValToReplace, 4380 Loops, SE, DT); 4381 4382 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP))); 4383 } 4384 4385 // Expand the ScaledReg portion. 4386 Value *ICmpScaledV = 0; 4387 if (F.Scale != 0) { 4388 const SCEV *ScaledS = F.ScaledReg; 4389 4390 // If we're expanding for a post-inc user, make the post-inc adjustment. 4391 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); 4392 ScaledS = TransformForPostIncUse(Denormalize, ScaledS, 4393 LF.UserInst, LF.OperandValToReplace, 4394 Loops, SE, DT); 4395 4396 if (LU.Kind == LSRUse::ICmpZero) { 4397 // An interesting way of "folding" with an icmp is to use a negated 4398 // scale, which we'll implement by inserting it into the other operand 4399 // of the icmp. 4400 assert(F.Scale == -1 && 4401 "The only scale supported by ICmpZero uses is -1!"); 4402 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP); 4403 } else { 4404 // Otherwise just expand the scaled register and an explicit scale, 4405 // which is expected to be matched as part of the address. 4406 4407 // Flush the operand list to suppress SCEVExpander hoisting address modes. 4408 if (!Ops.empty() && LU.Kind == LSRUse::Address) { 4409 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); 4410 Ops.clear(); 4411 Ops.push_back(SE.getUnknown(FullV)); 4412 } 4413 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP)); 4414 ScaledS = SE.getMulExpr(ScaledS, 4415 SE.getConstant(ScaledS->getType(), F.Scale)); 4416 Ops.push_back(ScaledS); 4417 } 4418 } 4419 4420 // Expand the GV portion. 4421 if (F.BaseGV) { 4422 // Flush the operand list to suppress SCEVExpander hoisting. 4423 if (!Ops.empty()) { 4424 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); 4425 Ops.clear(); 4426 Ops.push_back(SE.getUnknown(FullV)); 4427 } 4428 Ops.push_back(SE.getUnknown(F.BaseGV)); 4429 } 4430 4431 // Flush the operand list to suppress SCEVExpander hoisting of both folded and 4432 // unfolded offsets. LSR assumes they both live next to their uses. 4433 if (!Ops.empty()) { 4434 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); 4435 Ops.clear(); 4436 Ops.push_back(SE.getUnknown(FullV)); 4437 } 4438 4439 // Expand the immediate portion. 4440 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset; 4441 if (Offset != 0) { 4442 if (LU.Kind == LSRUse::ICmpZero) { 4443 // The other interesting way of "folding" with an ICmpZero is to use a 4444 // negated immediate. 4445 if (!ICmpScaledV) 4446 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset); 4447 else { 4448 Ops.push_back(SE.getUnknown(ICmpScaledV)); 4449 ICmpScaledV = ConstantInt::get(IntTy, Offset); 4450 } 4451 } else { 4452 // Just add the immediate values. These again are expected to be matched 4453 // as part of the address. 4454 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset))); 4455 } 4456 } 4457 4458 // Expand the unfolded offset portion. 4459 int64_t UnfoldedOffset = F.UnfoldedOffset; 4460 if (UnfoldedOffset != 0) { 4461 // Just add the immediate values. 4462 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, 4463 UnfoldedOffset))); 4464 } 4465 4466 // Emit instructions summing all the operands. 4467 const SCEV *FullS = Ops.empty() ? 4468 SE.getConstant(IntTy, 0) : 4469 SE.getAddExpr(Ops); 4470 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP); 4471 4472 // We're done expanding now, so reset the rewriter. 4473 Rewriter.clearPostInc(); 4474 4475 // An ICmpZero Formula represents an ICmp which we're handling as a 4476 // comparison against zero. Now that we've expanded an expression for that 4477 // form, update the ICmp's other operand. 4478 if (LU.Kind == LSRUse::ICmpZero) { 4479 ICmpInst *CI = cast<ICmpInst>(LF.UserInst); 4480 DeadInsts.push_back(CI->getOperand(1)); 4481 assert(!F.BaseGV && "ICmp does not support folding a global value and " 4482 "a scale at the same time!"); 4483 if (F.Scale == -1) { 4484 if (ICmpScaledV->getType() != OpTy) { 4485 Instruction *Cast = 4486 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false, 4487 OpTy, false), 4488 ICmpScaledV, OpTy, "tmp", CI); 4489 ICmpScaledV = Cast; 4490 } 4491 CI->setOperand(1, ICmpScaledV); 4492 } else { 4493 assert(F.Scale == 0 && 4494 "ICmp does not support folding a global value and " 4495 "a scale at the same time!"); 4496 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy), 4497 -(uint64_t)Offset); 4498 if (C->getType() != OpTy) 4499 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 4500 OpTy, false), 4501 C, OpTy); 4502 4503 CI->setOperand(1, C); 4504 } 4505 } 4506 4507 return FullV; 4508} 4509 4510/// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use 4511/// of their operands effectively happens in their predecessor blocks, so the 4512/// expression may need to be expanded in multiple places. 4513void LSRInstance::RewriteForPHI(PHINode *PN, 4514 const LSRFixup &LF, 4515 const Formula &F, 4516 SCEVExpander &Rewriter, 4517 SmallVectorImpl<WeakVH> &DeadInsts, 4518 Pass *P) const { 4519 DenseMap<BasicBlock *, Value *> Inserted; 4520 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 4521 if (PN->getIncomingValue(i) == LF.OperandValToReplace) { 4522 BasicBlock *BB = PN->getIncomingBlock(i); 4523 4524 // If this is a critical edge, split the edge so that we do not insert 4525 // the code on all predecessor/successor paths. We do this unless this 4526 // is the canonical backedge for this loop, which complicates post-inc 4527 // users. 4528 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 && 4529 !isa<IndirectBrInst>(BB->getTerminator())) { 4530 BasicBlock *Parent = PN->getParent(); 4531 Loop *PNLoop = LI.getLoopFor(Parent); 4532 if (!PNLoop || Parent != PNLoop->getHeader()) { 4533 // Split the critical edge. 4534 BasicBlock *NewBB = 0; 4535 if (!Parent->isLandingPad()) { 4536 NewBB = SplitCriticalEdge(BB, Parent, P, 4537 /*MergeIdenticalEdges=*/true, 4538 /*DontDeleteUselessPhis=*/true); 4539 } else { 4540 SmallVector<BasicBlock*, 2> NewBBs; 4541 SplitLandingPadPredecessors(Parent, BB, "", "", P, NewBBs); 4542 NewBB = NewBBs[0]; 4543 } 4544 // If NewBB==NULL, then SplitCriticalEdge refused to split because all 4545 // phi predecessors are identical. The simple thing to do is skip 4546 // splitting in this case rather than complicate the API. 4547 if (NewBB) { 4548 // If PN is outside of the loop and BB is in the loop, we want to 4549 // move the block to be immediately before the PHI block, not 4550 // immediately after BB. 4551 if (L->contains(BB) && !L->contains(PN)) 4552 NewBB->moveBefore(PN->getParent()); 4553 4554 // Splitting the edge can reduce the number of PHI entries we have. 4555 e = PN->getNumIncomingValues(); 4556 BB = NewBB; 4557 i = PN->getBasicBlockIndex(BB); 4558 } 4559 } 4560 } 4561 4562 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair = 4563 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0))); 4564 if (!Pair.second) 4565 PN->setIncomingValue(i, Pair.first->second); 4566 else { 4567 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts); 4568 4569 // If this is reuse-by-noop-cast, insert the noop cast. 4570 Type *OpTy = LF.OperandValToReplace->getType(); 4571 if (FullV->getType() != OpTy) 4572 FullV = 4573 CastInst::Create(CastInst::getCastOpcode(FullV, false, 4574 OpTy, false), 4575 FullV, LF.OperandValToReplace->getType(), 4576 "tmp", BB->getTerminator()); 4577 4578 PN->setIncomingValue(i, FullV); 4579 Pair.first->second = FullV; 4580 } 4581 } 4582} 4583 4584/// Rewrite - Emit instructions for the leading candidate expression for this 4585/// LSRUse (this is called "expanding"), and update the UserInst to reference 4586/// the newly expanded value. 4587void LSRInstance::Rewrite(const LSRFixup &LF, 4588 const Formula &F, 4589 SCEVExpander &Rewriter, 4590 SmallVectorImpl<WeakVH> &DeadInsts, 4591 Pass *P) const { 4592 // First, find an insertion point that dominates UserInst. For PHI nodes, 4593 // find the nearest block which dominates all the relevant uses. 4594 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) { 4595 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P); 4596 } else { 4597 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts); 4598 4599 // If this is reuse-by-noop-cast, insert the noop cast. 4600 Type *OpTy = LF.OperandValToReplace->getType(); 4601 if (FullV->getType() != OpTy) { 4602 Instruction *Cast = 4603 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false), 4604 FullV, OpTy, "tmp", LF.UserInst); 4605 FullV = Cast; 4606 } 4607 4608 // Update the user. ICmpZero is handled specially here (for now) because 4609 // Expand may have updated one of the operands of the icmp already, and 4610 // its new value may happen to be equal to LF.OperandValToReplace, in 4611 // which case doing replaceUsesOfWith leads to replacing both operands 4612 // with the same value. TODO: Reorganize this. 4613 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero) 4614 LF.UserInst->setOperand(0, FullV); 4615 else 4616 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV); 4617 } 4618 4619 DeadInsts.push_back(LF.OperandValToReplace); 4620} 4621 4622/// ImplementSolution - Rewrite all the fixup locations with new values, 4623/// following the chosen solution. 4624void 4625LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution, 4626 Pass *P) { 4627 // Keep track of instructions we may have made dead, so that 4628 // we can remove them after we are done working. 4629 SmallVector<WeakVH, 16> DeadInsts; 4630 4631 SCEVExpander Rewriter(SE, "lsr"); 4632#ifndef NDEBUG 4633 Rewriter.setDebugType(DEBUG_TYPE); 4634#endif 4635 Rewriter.disableCanonicalMode(); 4636 Rewriter.enableLSRMode(); 4637 Rewriter.setIVIncInsertPos(L, IVIncInsertPos); 4638 4639 // Mark phi nodes that terminate chains so the expander tries to reuse them. 4640 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(), 4641 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) { 4642 if (PHINode *PN = dyn_cast<PHINode>(ChainI->tailUserInst())) 4643 Rewriter.setChainedPhi(PN); 4644 } 4645 4646 // Expand the new value definitions and update the users. 4647 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(), 4648 E = Fixups.end(); I != E; ++I) { 4649 const LSRFixup &Fixup = *I; 4650 4651 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P); 4652 4653 Changed = true; 4654 } 4655 4656 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(), 4657 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) { 4658 GenerateIVChain(*ChainI, Rewriter, DeadInsts); 4659 Changed = true; 4660 } 4661 // Clean up after ourselves. This must be done before deleting any 4662 // instructions. 4663 Rewriter.clear(); 4664 4665 Changed |= DeleteTriviallyDeadInstructions(DeadInsts); 4666} 4667 4668LSRInstance::LSRInstance(Loop *L, Pass *P) 4669 : IU(P->getAnalysis<IVUsers>()), SE(P->getAnalysis<ScalarEvolution>()), 4670 DT(P->getAnalysis<DominatorTreeWrapperPass>().getDomTree()), 4671 LI(P->getAnalysis<LoopInfo>()), 4672 TTI(P->getAnalysis<TargetTransformInfo>()), L(L), Changed(false), 4673 IVIncInsertPos(0) { 4674 // If LoopSimplify form is not available, stay out of trouble. 4675 if (!L->isLoopSimplifyForm()) 4676 return; 4677 4678 // If there's no interesting work to be done, bail early. 4679 if (IU.empty()) return; 4680 4681 // If there's too much analysis to be done, bail early. We won't be able to 4682 // model the problem anyway. 4683 unsigned NumUsers = 0; 4684 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { 4685 if (++NumUsers > MaxIVUsers) { 4686 DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << *L 4687 << "\n"); 4688 return; 4689 } 4690 } 4691 4692#ifndef NDEBUG 4693 // All dominating loops must have preheaders, or SCEVExpander may not be able 4694 // to materialize an AddRecExpr whose Start is an outer AddRecExpr. 4695 // 4696 // IVUsers analysis should only create users that are dominated by simple loop 4697 // headers. Since this loop should dominate all of its users, its user list 4698 // should be empty if this loop itself is not within a simple loop nest. 4699 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader()); 4700 Rung; Rung = Rung->getIDom()) { 4701 BasicBlock *BB = Rung->getBlock(); 4702 const Loop *DomLoop = LI.getLoopFor(BB); 4703 if (DomLoop && DomLoop->getHeader() == BB) { 4704 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest"); 4705 } 4706 } 4707#endif // DEBUG 4708 4709 DEBUG(dbgs() << "\nLSR on loop "; 4710 L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false); 4711 dbgs() << ":\n"); 4712 4713 // First, perform some low-level loop optimizations. 4714 OptimizeShadowIV(); 4715 OptimizeLoopTermCond(); 4716 4717 // If loop preparation eliminates all interesting IV users, bail. 4718 if (IU.empty()) return; 4719 4720 // Skip nested loops until we can model them better with formulae. 4721 if (!L->empty()) { 4722 DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n"); 4723 return; 4724 } 4725 4726 // Start collecting data and preparing for the solver. 4727 CollectChains(); 4728 CollectInterestingTypesAndFactors(); 4729 CollectFixupsAndInitialFormulae(); 4730 CollectLoopInvariantFixupsAndFormulae(); 4731 4732 assert(!Uses.empty() && "IVUsers reported at least one use"); 4733 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n"; 4734 print_uses(dbgs())); 4735 4736 // Now use the reuse data to generate a bunch of interesting ways 4737 // to formulate the values needed for the uses. 4738 GenerateAllReuseFormulae(); 4739 4740 FilterOutUndesirableDedicatedRegisters(); 4741 NarrowSearchSpaceUsingHeuristics(); 4742 4743 SmallVector<const Formula *, 8> Solution; 4744 Solve(Solution); 4745 4746 // Release memory that is no longer needed. 4747 Factors.clear(); 4748 Types.clear(); 4749 RegUses.clear(); 4750 4751 if (Solution.empty()) 4752 return; 4753 4754#ifndef NDEBUG 4755 // Formulae should be legal. 4756 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), E = Uses.end(); 4757 I != E; ++I) { 4758 const LSRUse &LU = *I; 4759 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(), 4760 JE = LU.Formulae.end(); 4761 J != JE; ++J) 4762 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, 4763 *J) && "Illegal formula generated!"); 4764 }; 4765#endif 4766 4767 // Now that we've decided what we want, make it so. 4768 ImplementSolution(Solution, P); 4769} 4770 4771void LSRInstance::print_factors_and_types(raw_ostream &OS) const { 4772 if (Factors.empty() && Types.empty()) return; 4773 4774 OS << "LSR has identified the following interesting factors and types: "; 4775 bool First = true; 4776 4777 for (SmallSetVector<int64_t, 8>::const_iterator 4778 I = Factors.begin(), E = Factors.end(); I != E; ++I) { 4779 if (!First) OS << ", "; 4780 First = false; 4781 OS << '*' << *I; 4782 } 4783 4784 for (SmallSetVector<Type *, 4>::const_iterator 4785 I = Types.begin(), E = Types.end(); I != E; ++I) { 4786 if (!First) OS << ", "; 4787 First = false; 4788 OS << '(' << **I << ')'; 4789 } 4790 OS << '\n'; 4791} 4792 4793void LSRInstance::print_fixups(raw_ostream &OS) const { 4794 OS << "LSR is examining the following fixup sites:\n"; 4795 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(), 4796 E = Fixups.end(); I != E; ++I) { 4797 dbgs() << " "; 4798 I->print(OS); 4799 OS << '\n'; 4800 } 4801} 4802 4803void LSRInstance::print_uses(raw_ostream &OS) const { 4804 OS << "LSR is examining the following uses:\n"; 4805 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), 4806 E = Uses.end(); I != E; ++I) { 4807 const LSRUse &LU = *I; 4808 dbgs() << " "; 4809 LU.print(OS); 4810 OS << '\n'; 4811 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(), 4812 JE = LU.Formulae.end(); J != JE; ++J) { 4813 OS << " "; 4814 J->print(OS); 4815 OS << '\n'; 4816 } 4817 } 4818} 4819 4820void LSRInstance::print(raw_ostream &OS) const { 4821 print_factors_and_types(OS); 4822 print_fixups(OS); 4823 print_uses(OS); 4824} 4825 4826#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 4827void LSRInstance::dump() const { 4828 print(errs()); errs() << '\n'; 4829} 4830#endif 4831 4832namespace { 4833 4834class LoopStrengthReduce : public LoopPass { 4835public: 4836 static char ID; // Pass ID, replacement for typeid 4837 LoopStrengthReduce(); 4838 4839private: 4840 bool runOnLoop(Loop *L, LPPassManager &LPM) override; 4841 void getAnalysisUsage(AnalysisUsage &AU) const override; 4842}; 4843 4844} 4845 4846char LoopStrengthReduce::ID = 0; 4847INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce", 4848 "Loop Strength Reduction", false, false) 4849INITIALIZE_AG_DEPENDENCY(TargetTransformInfo) 4850INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 4851INITIALIZE_PASS_DEPENDENCY(ScalarEvolution) 4852INITIALIZE_PASS_DEPENDENCY(IVUsers) 4853INITIALIZE_PASS_DEPENDENCY(LoopInfo) 4854INITIALIZE_PASS_DEPENDENCY(LoopSimplify) 4855INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce", 4856 "Loop Strength Reduction", false, false) 4857 4858 4859Pass *llvm::createLoopStrengthReducePass() { 4860 return new LoopStrengthReduce(); 4861} 4862 4863LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) { 4864 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry()); 4865} 4866 4867void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const { 4868 // We split critical edges, so we change the CFG. However, we do update 4869 // many analyses if they are around. 4870 AU.addPreservedID(LoopSimplifyID); 4871 4872 AU.addRequired<LoopInfo>(); 4873 AU.addPreserved<LoopInfo>(); 4874 AU.addRequiredID(LoopSimplifyID); 4875 AU.addRequired<DominatorTreeWrapperPass>(); 4876 AU.addPreserved<DominatorTreeWrapperPass>(); 4877 AU.addRequired<ScalarEvolution>(); 4878 AU.addPreserved<ScalarEvolution>(); 4879 // Requiring LoopSimplify a second time here prevents IVUsers from running 4880 // twice, since LoopSimplify was invalidated by running ScalarEvolution. 4881 AU.addRequiredID(LoopSimplifyID); 4882 AU.addRequired<IVUsers>(); 4883 AU.addPreserved<IVUsers>(); 4884 AU.addRequired<TargetTransformInfo>(); 4885} 4886 4887bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) { 4888 if (skipOptnoneFunction(L)) 4889 return false; 4890 4891 bool Changed = false; 4892 4893 // Run the main LSR transformation. 4894 Changed |= LSRInstance(L, this).getChanged(); 4895 4896 // Remove any extra phis created by processing inner loops. 4897 Changed |= DeleteDeadPHIs(L->getHeader()); 4898 if (EnablePhiElim && L->isLoopSimplifyForm()) { 4899 SmallVector<WeakVH, 16> DeadInsts; 4900 SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), "lsr"); 4901#ifndef NDEBUG 4902 Rewriter.setDebugType(DEBUG_TYPE); 4903#endif 4904 unsigned numFolded = Rewriter.replaceCongruentIVs( 4905 L, &getAnalysis<DominatorTreeWrapperPass>().getDomTree(), DeadInsts, 4906 &getAnalysis<TargetTransformInfo>()); 4907 if (numFolded) { 4908 Changed = true; 4909 DeleteTriviallyDeadInstructions(DeadInsts); 4910 DeleteDeadPHIs(L->getHeader()); 4911 } 4912 } 4913 return Changed; 4914} 4915