LoopStrengthReduce.cpp revision f182b23f8fed014c26da48d94890080c7d916a0c
1//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This transformation analyzes and transforms the induction variables (and 11// computations derived from them) into forms suitable for efficient execution 12// on the target. 13// 14// This pass performs a strength reduction on array references inside loops that 15// have as one or more of their components the loop induction variable, it 16// rewrites expressions to take advantage of scaled-index addressing modes 17// available on the target, and it performs a variety of other optimizations 18// related to loop induction variables. 19// 20// Terminology note: this code has a lot of handling for "post-increment" or 21// "post-inc" users. This is not talking about post-increment addressing modes; 22// it is instead talking about code like this: 23// 24// %i = phi [ 0, %entry ], [ %i.next, %latch ] 25// ... 26// %i.next = add %i, 1 27// %c = icmp eq %i.next, %n 28// 29// The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however 30// it's useful to think about these as the same register, with some uses using 31// the value of the register before the add and some using // it after. In this 32// example, the icmp is a post-increment user, since it uses %i.next, which is 33// the value of the induction variable after the increment. The other common 34// case of post-increment users is users outside the loop. 35// 36// TODO: More sophistication in the way Formulae are generated and filtered. 37// 38// TODO: Handle multiple loops at a time. 39// 40// TODO: Should TargetLowering::AddrMode::BaseGV be changed to a ConstantExpr 41// instead of a GlobalValue? 42// 43// TODO: When truncation is free, truncate ICmp users' operands to make it a 44// smaller encoding (on x86 at least). 45// 46// TODO: When a negated register is used by an add (such as in a list of 47// multiple base registers, or as the increment expression in an addrec), 48// we may not actually need both reg and (-1 * reg) in registers; the 49// negation can be implemented by using a sub instead of an add. The 50// lack of support for taking this into consideration when making 51// register pressure decisions is partly worked around by the "Special" 52// use kind. 53// 54//===----------------------------------------------------------------------===// 55 56#define DEBUG_TYPE "loop-reduce" 57#include "llvm/Transforms/Scalar.h" 58#include "llvm/Constants.h" 59#include "llvm/Instructions.h" 60#include "llvm/IntrinsicInst.h" 61#include "llvm/DerivedTypes.h" 62#include "llvm/Analysis/IVUsers.h" 63#include "llvm/Analysis/Dominators.h" 64#include "llvm/Analysis/LoopPass.h" 65#include "llvm/Analysis/ScalarEvolutionExpander.h" 66#include "llvm/Transforms/Utils/BasicBlockUtils.h" 67#include "llvm/Transforms/Utils/Local.h" 68#include "llvm/ADT/SmallBitVector.h" 69#include "llvm/ADT/SetVector.h" 70#include "llvm/ADT/DenseSet.h" 71#include "llvm/Support/Debug.h" 72#include "llvm/Support/ValueHandle.h" 73#include "llvm/Support/raw_ostream.h" 74#include "llvm/Target/TargetLowering.h" 75#include <algorithm> 76using namespace llvm; 77 78namespace { 79 80/// RegSortData - This class holds data which is used to order reuse candidates. 81class RegSortData { 82public: 83 /// UsedByIndices - This represents the set of LSRUse indices which reference 84 /// a particular register. 85 SmallBitVector UsedByIndices; 86 87 RegSortData() {} 88 89 void print(raw_ostream &OS) const; 90 void dump() const; 91}; 92 93} 94 95void RegSortData::print(raw_ostream &OS) const { 96 OS << "[NumUses=" << UsedByIndices.count() << ']'; 97} 98 99void RegSortData::dump() const { 100 print(errs()); errs() << '\n'; 101} 102 103namespace { 104 105/// RegUseTracker - Map register candidates to information about how they are 106/// used. 107class RegUseTracker { 108 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy; 109 110 RegUsesTy RegUsesMap; 111 SmallVector<const SCEV *, 16> RegSequence; 112 113public: 114 void CountRegister(const SCEV *Reg, size_t LUIdx); 115 void DropRegister(const SCEV *Reg, size_t LUIdx); 116 void DropUse(size_t LUIdx); 117 118 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const; 119 120 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const; 121 122 void clear(); 123 124 typedef SmallVectorImpl<const SCEV *>::iterator iterator; 125 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator; 126 iterator begin() { return RegSequence.begin(); } 127 iterator end() { return RegSequence.end(); } 128 const_iterator begin() const { return RegSequence.begin(); } 129 const_iterator end() const { return RegSequence.end(); } 130}; 131 132} 133 134void 135RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) { 136 std::pair<RegUsesTy::iterator, bool> Pair = 137 RegUsesMap.insert(std::make_pair(Reg, RegSortData())); 138 RegSortData &RSD = Pair.first->second; 139 if (Pair.second) 140 RegSequence.push_back(Reg); 141 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1)); 142 RSD.UsedByIndices.set(LUIdx); 143} 144 145void 146RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) { 147 RegUsesTy::iterator It = RegUsesMap.find(Reg); 148 assert(It != RegUsesMap.end()); 149 RegSortData &RSD = It->second; 150 assert(RSD.UsedByIndices.size() > LUIdx); 151 RSD.UsedByIndices.reset(LUIdx); 152} 153 154void 155RegUseTracker::DropUse(size_t LUIdx) { 156 // Remove the use index from every register's use list. 157 for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end(); 158 I != E; ++I) 159 I->second.UsedByIndices.reset(LUIdx); 160} 161 162bool 163RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const { 164 if (!RegUsesMap.count(Reg)) return false; 165 const SmallBitVector &UsedByIndices = 166 RegUsesMap.find(Reg)->second.UsedByIndices; 167 int i = UsedByIndices.find_first(); 168 if (i == -1) return false; 169 if ((size_t)i != LUIdx) return true; 170 return UsedByIndices.find_next(i) != -1; 171} 172 173const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const { 174 RegUsesTy::const_iterator I = RegUsesMap.find(Reg); 175 assert(I != RegUsesMap.end() && "Unknown register!"); 176 return I->second.UsedByIndices; 177} 178 179void RegUseTracker::clear() { 180 RegUsesMap.clear(); 181 RegSequence.clear(); 182} 183 184namespace { 185 186/// Formula - This class holds information that describes a formula for 187/// computing satisfying a use. It may include broken-out immediates and scaled 188/// registers. 189struct Formula { 190 /// AM - This is used to represent complex addressing, as well as other kinds 191 /// of interesting uses. 192 TargetLowering::AddrMode AM; 193 194 /// BaseRegs - The list of "base" registers for this use. When this is 195 /// non-empty, AM.HasBaseReg should be set to true. 196 SmallVector<const SCEV *, 2> BaseRegs; 197 198 /// ScaledReg - The 'scaled' register for this use. This should be non-null 199 /// when AM.Scale is not zero. 200 const SCEV *ScaledReg; 201 202 Formula() : ScaledReg(0) {} 203 204 void InitialMatch(const SCEV *S, Loop *L, 205 ScalarEvolution &SE, DominatorTree &DT); 206 207 unsigned getNumRegs() const; 208 const Type *getType() const; 209 210 void DeleteBaseReg(const SCEV *&S); 211 212 bool referencesReg(const SCEV *S) const; 213 bool hasRegsUsedByUsesOtherThan(size_t LUIdx, 214 const RegUseTracker &RegUses) const; 215 216 void print(raw_ostream &OS) const; 217 void dump() const; 218}; 219 220} 221 222/// DoInitialMatch - Recursion helper for InitialMatch. 223static void DoInitialMatch(const SCEV *S, Loop *L, 224 SmallVectorImpl<const SCEV *> &Good, 225 SmallVectorImpl<const SCEV *> &Bad, 226 ScalarEvolution &SE, DominatorTree &DT) { 227 // Collect expressions which properly dominate the loop header. 228 if (S->properlyDominates(L->getHeader(), &DT)) { 229 Good.push_back(S); 230 return; 231 } 232 233 // Look at add operands. 234 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 235 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 236 I != E; ++I) 237 DoInitialMatch(*I, L, Good, Bad, SE, DT); 238 return; 239 } 240 241 // Look at addrec operands. 242 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) 243 if (!AR->getStart()->isZero()) { 244 DoInitialMatch(AR->getStart(), L, Good, Bad, SE, DT); 245 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0), 246 AR->getStepRecurrence(SE), 247 AR->getLoop()), 248 L, Good, Bad, SE, DT); 249 return; 250 } 251 252 // Handle a multiplication by -1 (negation) if it didn't fold. 253 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) 254 if (Mul->getOperand(0)->isAllOnesValue()) { 255 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end()); 256 const SCEV *NewMul = SE.getMulExpr(Ops); 257 258 SmallVector<const SCEV *, 4> MyGood; 259 SmallVector<const SCEV *, 4> MyBad; 260 DoInitialMatch(NewMul, L, MyGood, MyBad, SE, DT); 261 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue( 262 SE.getEffectiveSCEVType(NewMul->getType()))); 263 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(), 264 E = MyGood.end(); I != E; ++I) 265 Good.push_back(SE.getMulExpr(NegOne, *I)); 266 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(), 267 E = MyBad.end(); I != E; ++I) 268 Bad.push_back(SE.getMulExpr(NegOne, *I)); 269 return; 270 } 271 272 // Ok, we can't do anything interesting. Just stuff the whole thing into a 273 // register and hope for the best. 274 Bad.push_back(S); 275} 276 277/// InitialMatch - Incorporate loop-variant parts of S into this Formula, 278/// attempting to keep all loop-invariant and loop-computable values in a 279/// single base register. 280void Formula::InitialMatch(const SCEV *S, Loop *L, 281 ScalarEvolution &SE, DominatorTree &DT) { 282 SmallVector<const SCEV *, 4> Good; 283 SmallVector<const SCEV *, 4> Bad; 284 DoInitialMatch(S, L, Good, Bad, SE, DT); 285 if (!Good.empty()) { 286 const SCEV *Sum = SE.getAddExpr(Good); 287 if (!Sum->isZero()) 288 BaseRegs.push_back(Sum); 289 AM.HasBaseReg = true; 290 } 291 if (!Bad.empty()) { 292 const SCEV *Sum = SE.getAddExpr(Bad); 293 if (!Sum->isZero()) 294 BaseRegs.push_back(Sum); 295 AM.HasBaseReg = true; 296 } 297} 298 299/// getNumRegs - Return the total number of register operands used by this 300/// formula. This does not include register uses implied by non-constant 301/// addrec strides. 302unsigned Formula::getNumRegs() const { 303 return !!ScaledReg + BaseRegs.size(); 304} 305 306/// getType - Return the type of this formula, if it has one, or null 307/// otherwise. This type is meaningless except for the bit size. 308const Type *Formula::getType() const { 309 return !BaseRegs.empty() ? BaseRegs.front()->getType() : 310 ScaledReg ? ScaledReg->getType() : 311 AM.BaseGV ? AM.BaseGV->getType() : 312 0; 313} 314 315/// DeleteBaseReg - Delete the given base reg from the BaseRegs list. 316void Formula::DeleteBaseReg(const SCEV *&S) { 317 if (&S != &BaseRegs.back()) 318 std::swap(S, BaseRegs.back()); 319 BaseRegs.pop_back(); 320} 321 322/// referencesReg - Test if this formula references the given register. 323bool Formula::referencesReg(const SCEV *S) const { 324 return S == ScaledReg || 325 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end(); 326} 327 328/// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers 329/// which are used by uses other than the use with the given index. 330bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx, 331 const RegUseTracker &RegUses) const { 332 if (ScaledReg) 333 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx)) 334 return true; 335 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(), 336 E = BaseRegs.end(); I != E; ++I) 337 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx)) 338 return true; 339 return false; 340} 341 342void Formula::print(raw_ostream &OS) const { 343 bool First = true; 344 if (AM.BaseGV) { 345 if (!First) OS << " + "; else First = false; 346 WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false); 347 } 348 if (AM.BaseOffs != 0) { 349 if (!First) OS << " + "; else First = false; 350 OS << AM.BaseOffs; 351 } 352 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(), 353 E = BaseRegs.end(); I != E; ++I) { 354 if (!First) OS << " + "; else First = false; 355 OS << "reg(" << **I << ')'; 356 } 357 if (AM.HasBaseReg && BaseRegs.empty()) { 358 if (!First) OS << " + "; else First = false; 359 OS << "**error: HasBaseReg**"; 360 } else if (!AM.HasBaseReg && !BaseRegs.empty()) { 361 if (!First) OS << " + "; else First = false; 362 OS << "**error: !HasBaseReg**"; 363 } 364 if (AM.Scale != 0) { 365 if (!First) OS << " + "; else First = false; 366 OS << AM.Scale << "*reg("; 367 if (ScaledReg) 368 OS << *ScaledReg; 369 else 370 OS << "<unknown>"; 371 OS << ')'; 372 } 373} 374 375void Formula::dump() const { 376 print(errs()); errs() << '\n'; 377} 378 379/// isAddRecSExtable - Return true if the given addrec can be sign-extended 380/// without changing its value. 381static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) { 382 const Type *WideTy = 383 IntegerType::get(SE.getContext(), 384 SE.getTypeSizeInBits(AR->getType()) + 1); 385 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy)); 386} 387 388/// isAddSExtable - Return true if the given add can be sign-extended 389/// without changing its value. 390static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) { 391 const Type *WideTy = 392 IntegerType::get(SE.getContext(), 393 SE.getTypeSizeInBits(A->getType()) + 1); 394 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy)); 395} 396 397/// isMulSExtable - Return true if the given add can be sign-extended 398/// without changing its value. 399static bool isMulSExtable(const SCEVMulExpr *A, ScalarEvolution &SE) { 400 const Type *WideTy = 401 IntegerType::get(SE.getContext(), 402 SE.getTypeSizeInBits(A->getType()) + 1); 403 return isa<SCEVMulExpr>(SE.getSignExtendExpr(A, WideTy)); 404} 405 406/// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined 407/// and if the remainder is known to be zero, or null otherwise. If 408/// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified 409/// to Y, ignoring that the multiplication may overflow, which is useful when 410/// the result will be used in a context where the most significant bits are 411/// ignored. 412static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS, 413 ScalarEvolution &SE, 414 bool IgnoreSignificantBits = false) { 415 // Handle the trivial case, which works for any SCEV type. 416 if (LHS == RHS) 417 return SE.getConstant(LHS->getType(), 1); 418 419 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do some 420 // folding. 421 if (RHS->isAllOnesValue()) 422 return SE.getMulExpr(LHS, RHS); 423 424 // Check for a division of a constant by a constant. 425 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) { 426 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS); 427 if (!RC) 428 return 0; 429 if (C->getValue()->getValue().srem(RC->getValue()->getValue()) != 0) 430 return 0; 431 return SE.getConstant(C->getValue()->getValue() 432 .sdiv(RC->getValue()->getValue())); 433 } 434 435 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow. 436 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) { 437 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) { 438 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE, 439 IgnoreSignificantBits); 440 if (!Start) return 0; 441 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE, 442 IgnoreSignificantBits); 443 if (!Step) return 0; 444 return SE.getAddRecExpr(Start, Step, AR->getLoop()); 445 } 446 } 447 448 // Distribute the sdiv over add operands, if the add doesn't overflow. 449 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) { 450 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) { 451 SmallVector<const SCEV *, 8> Ops; 452 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 453 I != E; ++I) { 454 const SCEV *Op = getExactSDiv(*I, RHS, SE, 455 IgnoreSignificantBits); 456 if (!Op) return 0; 457 Ops.push_back(Op); 458 } 459 return SE.getAddExpr(Ops); 460 } 461 } 462 463 // Check for a multiply operand that we can pull RHS out of. 464 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) 465 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) { 466 SmallVector<const SCEV *, 4> Ops; 467 bool Found = false; 468 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end(); 469 I != E; ++I) { 470 const SCEV *S = *I; 471 if (!Found) 472 if (const SCEV *Q = getExactSDiv(S, RHS, SE, 473 IgnoreSignificantBits)) { 474 S = Q; 475 Found = true; 476 } 477 Ops.push_back(S); 478 } 479 return Found ? SE.getMulExpr(Ops) : 0; 480 } 481 482 // Otherwise we don't know. 483 return 0; 484} 485 486/// ExtractImmediate - If S involves the addition of a constant integer value, 487/// return that integer value, and mutate S to point to a new SCEV with that 488/// value excluded. 489static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) { 490 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) { 491 if (C->getValue()->getValue().getMinSignedBits() <= 64) { 492 S = SE.getConstant(C->getType(), 0); 493 return C->getValue()->getSExtValue(); 494 } 495 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 496 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); 497 int64_t Result = ExtractImmediate(NewOps.front(), SE); 498 S = SE.getAddExpr(NewOps); 499 return Result; 500 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 501 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); 502 int64_t Result = ExtractImmediate(NewOps.front(), SE); 503 S = SE.getAddRecExpr(NewOps, AR->getLoop()); 504 return Result; 505 } 506 return 0; 507} 508 509/// ExtractSymbol - If S involves the addition of a GlobalValue address, 510/// return that symbol, and mutate S to point to a new SCEV with that 511/// value excluded. 512static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) { 513 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { 514 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) { 515 S = SE.getConstant(GV->getType(), 0); 516 return GV; 517 } 518 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 519 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); 520 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE); 521 S = SE.getAddExpr(NewOps); 522 return Result; 523 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 524 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); 525 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE); 526 S = SE.getAddRecExpr(NewOps, AR->getLoop()); 527 return Result; 528 } 529 return 0; 530} 531 532/// isAddressUse - Returns true if the specified instruction is using the 533/// specified value as an address. 534static bool isAddressUse(Instruction *Inst, Value *OperandVal) { 535 bool isAddress = isa<LoadInst>(Inst); 536 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 537 if (SI->getOperand(1) == OperandVal) 538 isAddress = true; 539 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 540 // Addressing modes can also be folded into prefetches and a variety 541 // of intrinsics. 542 switch (II->getIntrinsicID()) { 543 default: break; 544 case Intrinsic::prefetch: 545 case Intrinsic::x86_sse2_loadu_dq: 546 case Intrinsic::x86_sse2_loadu_pd: 547 case Intrinsic::x86_sse_loadu_ps: 548 case Intrinsic::x86_sse_storeu_ps: 549 case Intrinsic::x86_sse2_storeu_pd: 550 case Intrinsic::x86_sse2_storeu_dq: 551 case Intrinsic::x86_sse2_storel_dq: 552 if (II->getOperand(1) == OperandVal) 553 isAddress = true; 554 break; 555 } 556 } 557 return isAddress; 558} 559 560/// getAccessType - Return the type of the memory being accessed. 561static const Type *getAccessType(const Instruction *Inst) { 562 const Type *AccessTy = Inst->getType(); 563 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) 564 AccessTy = SI->getOperand(0)->getType(); 565 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 566 // Addressing modes can also be folded into prefetches and a variety 567 // of intrinsics. 568 switch (II->getIntrinsicID()) { 569 default: break; 570 case Intrinsic::x86_sse_storeu_ps: 571 case Intrinsic::x86_sse2_storeu_pd: 572 case Intrinsic::x86_sse2_storeu_dq: 573 case Intrinsic::x86_sse2_storel_dq: 574 AccessTy = II->getOperand(1)->getType(); 575 break; 576 } 577 } 578 579 // All pointers have the same requirements, so canonicalize them to an 580 // arbitrary pointer type to minimize variation. 581 if (const PointerType *PTy = dyn_cast<PointerType>(AccessTy)) 582 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1), 583 PTy->getAddressSpace()); 584 585 return AccessTy; 586} 587 588/// DeleteTriviallyDeadInstructions - If any of the instructions is the 589/// specified set are trivially dead, delete them and see if this makes any of 590/// their operands subsequently dead. 591static bool 592DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) { 593 bool Changed = false; 594 595 while (!DeadInsts.empty()) { 596 Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val()); 597 598 if (I == 0 || !isInstructionTriviallyDead(I)) 599 continue; 600 601 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 602 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 603 *OI = 0; 604 if (U->use_empty()) 605 DeadInsts.push_back(U); 606 } 607 608 I->eraseFromParent(); 609 Changed = true; 610 } 611 612 return Changed; 613} 614 615namespace { 616 617/// Cost - This class is used to measure and compare candidate formulae. 618class Cost { 619 /// TODO: Some of these could be merged. Also, a lexical ordering 620 /// isn't always optimal. 621 unsigned NumRegs; 622 unsigned AddRecCost; 623 unsigned NumIVMuls; 624 unsigned NumBaseAdds; 625 unsigned ImmCost; 626 unsigned SetupCost; 627 628public: 629 Cost() 630 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0), 631 SetupCost(0) {} 632 633 unsigned getNumRegs() const { return NumRegs; } 634 635 bool operator<(const Cost &Other) const; 636 637 void Loose(); 638 639 void RateFormula(const Formula &F, 640 SmallPtrSet<const SCEV *, 16> &Regs, 641 const DenseSet<const SCEV *> &VisitedRegs, 642 const Loop *L, 643 const SmallVectorImpl<int64_t> &Offsets, 644 ScalarEvolution &SE, DominatorTree &DT); 645 646 void print(raw_ostream &OS) const; 647 void dump() const; 648 649private: 650 void RateRegister(const SCEV *Reg, 651 SmallPtrSet<const SCEV *, 16> &Regs, 652 const Loop *L, 653 ScalarEvolution &SE, DominatorTree &DT); 654 void RatePrimaryRegister(const SCEV *Reg, 655 SmallPtrSet<const SCEV *, 16> &Regs, 656 const Loop *L, 657 ScalarEvolution &SE, DominatorTree &DT); 658}; 659 660} 661 662/// RateRegister - Tally up interesting quantities from the given register. 663void Cost::RateRegister(const SCEV *Reg, 664 SmallPtrSet<const SCEV *, 16> &Regs, 665 const Loop *L, 666 ScalarEvolution &SE, DominatorTree &DT) { 667 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) { 668 if (AR->getLoop() == L) 669 AddRecCost += 1; /// TODO: This should be a function of the stride. 670 671 // If this is an addrec for a loop that's already been visited by LSR, 672 // don't second-guess its addrec phi nodes. LSR isn't currently smart 673 // enough to reason about more than one loop at a time. Consider these 674 // registers free and leave them alone. 675 else if (L->contains(AR->getLoop()) || 676 (!AR->getLoop()->contains(L) && 677 DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) { 678 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin(); 679 PHINode *PN = dyn_cast<PHINode>(I); ++I) 680 if (SE.isSCEVable(PN->getType()) && 681 (SE.getEffectiveSCEVType(PN->getType()) == 682 SE.getEffectiveSCEVType(AR->getType())) && 683 SE.getSCEV(PN) == AR) 684 return; 685 686 // If this isn't one of the addrecs that the loop already has, it 687 // would require a costly new phi and add. TODO: This isn't 688 // precisely modeled right now. 689 ++NumBaseAdds; 690 if (!Regs.count(AR->getStart())) 691 RateRegister(AR->getStart(), Regs, L, SE, DT); 692 } 693 694 // Add the step value register, if it needs one. 695 // TODO: The non-affine case isn't precisely modeled here. 696 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) 697 if (!Regs.count(AR->getStart())) 698 RateRegister(AR->getOperand(1), Regs, L, SE, DT); 699 } 700 ++NumRegs; 701 702 // Rough heuristic; favor registers which don't require extra setup 703 // instructions in the preheader. 704 if (!isa<SCEVUnknown>(Reg) && 705 !isa<SCEVConstant>(Reg) && 706 !(isa<SCEVAddRecExpr>(Reg) && 707 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) || 708 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart())))) 709 ++SetupCost; 710} 711 712/// RatePrimaryRegister - Record this register in the set. If we haven't seen it 713/// before, rate it. 714void Cost::RatePrimaryRegister(const SCEV *Reg, 715 SmallPtrSet<const SCEV *, 16> &Regs, 716 const Loop *L, 717 ScalarEvolution &SE, DominatorTree &DT) { 718 if (Regs.insert(Reg)) 719 RateRegister(Reg, Regs, L, SE, DT); 720} 721 722void Cost::RateFormula(const Formula &F, 723 SmallPtrSet<const SCEV *, 16> &Regs, 724 const DenseSet<const SCEV *> &VisitedRegs, 725 const Loop *L, 726 const SmallVectorImpl<int64_t> &Offsets, 727 ScalarEvolution &SE, DominatorTree &DT) { 728 // Tally up the registers. 729 if (const SCEV *ScaledReg = F.ScaledReg) { 730 if (VisitedRegs.count(ScaledReg)) { 731 Loose(); 732 return; 733 } 734 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT); 735 } 736 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), 737 E = F.BaseRegs.end(); I != E; ++I) { 738 const SCEV *BaseReg = *I; 739 if (VisitedRegs.count(BaseReg)) { 740 Loose(); 741 return; 742 } 743 RatePrimaryRegister(BaseReg, Regs, L, SE, DT); 744 745 NumIVMuls += isa<SCEVMulExpr>(BaseReg) && 746 BaseReg->hasComputableLoopEvolution(L); 747 } 748 749 if (F.BaseRegs.size() > 1) 750 NumBaseAdds += F.BaseRegs.size() - 1; 751 752 // Tally up the non-zero immediates. 753 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(), 754 E = Offsets.end(); I != E; ++I) { 755 int64_t Offset = (uint64_t)*I + F.AM.BaseOffs; 756 if (F.AM.BaseGV) 757 ImmCost += 64; // Handle symbolic values conservatively. 758 // TODO: This should probably be the pointer size. 759 else if (Offset != 0) 760 ImmCost += APInt(64, Offset, true).getMinSignedBits(); 761 } 762} 763 764/// Loose - Set this cost to a loosing value. 765void Cost::Loose() { 766 NumRegs = ~0u; 767 AddRecCost = ~0u; 768 NumIVMuls = ~0u; 769 NumBaseAdds = ~0u; 770 ImmCost = ~0u; 771 SetupCost = ~0u; 772} 773 774/// operator< - Choose the lower cost. 775bool Cost::operator<(const Cost &Other) const { 776 if (NumRegs != Other.NumRegs) 777 return NumRegs < Other.NumRegs; 778 if (AddRecCost != Other.AddRecCost) 779 return AddRecCost < Other.AddRecCost; 780 if (NumIVMuls != Other.NumIVMuls) 781 return NumIVMuls < Other.NumIVMuls; 782 if (NumBaseAdds != Other.NumBaseAdds) 783 return NumBaseAdds < Other.NumBaseAdds; 784 if (ImmCost != Other.ImmCost) 785 return ImmCost < Other.ImmCost; 786 if (SetupCost != Other.SetupCost) 787 return SetupCost < Other.SetupCost; 788 return false; 789} 790 791void Cost::print(raw_ostream &OS) const { 792 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s"); 793 if (AddRecCost != 0) 794 OS << ", with addrec cost " << AddRecCost; 795 if (NumIVMuls != 0) 796 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s"); 797 if (NumBaseAdds != 0) 798 OS << ", plus " << NumBaseAdds << " base add" 799 << (NumBaseAdds == 1 ? "" : "s"); 800 if (ImmCost != 0) 801 OS << ", plus " << ImmCost << " imm cost"; 802 if (SetupCost != 0) 803 OS << ", plus " << SetupCost << " setup cost"; 804} 805 806void Cost::dump() const { 807 print(errs()); errs() << '\n'; 808} 809 810namespace { 811 812/// LSRFixup - An operand value in an instruction which is to be replaced 813/// with some equivalent, possibly strength-reduced, replacement. 814struct LSRFixup { 815 /// UserInst - The instruction which will be updated. 816 Instruction *UserInst; 817 818 /// OperandValToReplace - The operand of the instruction which will 819 /// be replaced. The operand may be used more than once; every instance 820 /// will be replaced. 821 Value *OperandValToReplace; 822 823 /// PostIncLoops - If this user is to use the post-incremented value of an 824 /// induction variable, this variable is non-null and holds the loop 825 /// associated with the induction variable. 826 PostIncLoopSet PostIncLoops; 827 828 /// LUIdx - The index of the LSRUse describing the expression which 829 /// this fixup needs, minus an offset (below). 830 size_t LUIdx; 831 832 /// Offset - A constant offset to be added to the LSRUse expression. 833 /// This allows multiple fixups to share the same LSRUse with different 834 /// offsets, for example in an unrolled loop. 835 int64_t Offset; 836 837 bool isUseFullyOutsideLoop(const Loop *L) const; 838 839 LSRFixup(); 840 841 void print(raw_ostream &OS) const; 842 void dump() const; 843}; 844 845} 846 847LSRFixup::LSRFixup() 848 : UserInst(0), OperandValToReplace(0), 849 LUIdx(~size_t(0)), Offset(0) {} 850 851/// isUseFullyOutsideLoop - Test whether this fixup always uses its 852/// value outside of the given loop. 853bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const { 854 // PHI nodes use their value in their incoming blocks. 855 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) { 856 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 857 if (PN->getIncomingValue(i) == OperandValToReplace && 858 L->contains(PN->getIncomingBlock(i))) 859 return false; 860 return true; 861 } 862 863 return !L->contains(UserInst); 864} 865 866void LSRFixup::print(raw_ostream &OS) const { 867 OS << "UserInst="; 868 // Store is common and interesting enough to be worth special-casing. 869 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) { 870 OS << "store "; 871 WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false); 872 } else if (UserInst->getType()->isVoidTy()) 873 OS << UserInst->getOpcodeName(); 874 else 875 WriteAsOperand(OS, UserInst, /*PrintType=*/false); 876 877 OS << ", OperandValToReplace="; 878 WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false); 879 880 for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(), 881 E = PostIncLoops.end(); I != E; ++I) { 882 OS << ", PostIncLoop="; 883 WriteAsOperand(OS, (*I)->getHeader(), /*PrintType=*/false); 884 } 885 886 if (LUIdx != ~size_t(0)) 887 OS << ", LUIdx=" << LUIdx; 888 889 if (Offset != 0) 890 OS << ", Offset=" << Offset; 891} 892 893void LSRFixup::dump() const { 894 print(errs()); errs() << '\n'; 895} 896 897namespace { 898 899/// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding 900/// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*. 901struct UniquifierDenseMapInfo { 902 static SmallVector<const SCEV *, 2> getEmptyKey() { 903 SmallVector<const SCEV *, 2> V; 904 V.push_back(reinterpret_cast<const SCEV *>(-1)); 905 return V; 906 } 907 908 static SmallVector<const SCEV *, 2> getTombstoneKey() { 909 SmallVector<const SCEV *, 2> V; 910 V.push_back(reinterpret_cast<const SCEV *>(-2)); 911 return V; 912 } 913 914 static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) { 915 unsigned Result = 0; 916 for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(), 917 E = V.end(); I != E; ++I) 918 Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I); 919 return Result; 920 } 921 922 static bool isEqual(const SmallVector<const SCEV *, 2> &LHS, 923 const SmallVector<const SCEV *, 2> &RHS) { 924 return LHS == RHS; 925 } 926}; 927 928/// LSRUse - This class holds the state that LSR keeps for each use in 929/// IVUsers, as well as uses invented by LSR itself. It includes information 930/// about what kinds of things can be folded into the user, information about 931/// the user itself, and information about how the use may be satisfied. 932/// TODO: Represent multiple users of the same expression in common? 933class LSRUse { 934 DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier; 935 936public: 937 /// KindType - An enum for a kind of use, indicating what types of 938 /// scaled and immediate operands it might support. 939 enum KindType { 940 Basic, ///< A normal use, with no folding. 941 Special, ///< A special case of basic, allowing -1 scales. 942 Address, ///< An address use; folding according to TargetLowering 943 ICmpZero ///< An equality icmp with both operands folded into one. 944 // TODO: Add a generic icmp too? 945 }; 946 947 KindType Kind; 948 const Type *AccessTy; 949 950 SmallVector<int64_t, 8> Offsets; 951 int64_t MinOffset; 952 int64_t MaxOffset; 953 954 /// AllFixupsOutsideLoop - This records whether all of the fixups using this 955 /// LSRUse are outside of the loop, in which case some special-case heuristics 956 /// may be used. 957 bool AllFixupsOutsideLoop; 958 959 /// Formulae - A list of ways to build a value that can satisfy this user. 960 /// After the list is populated, one of these is selected heuristically and 961 /// used to formulate a replacement for OperandValToReplace in UserInst. 962 SmallVector<Formula, 12> Formulae; 963 964 /// Regs - The set of register candidates used by all formulae in this LSRUse. 965 SmallPtrSet<const SCEV *, 4> Regs; 966 967 LSRUse(KindType K, const Type *T) : Kind(K), AccessTy(T), 968 MinOffset(INT64_MAX), 969 MaxOffset(INT64_MIN), 970 AllFixupsOutsideLoop(true) {} 971 972 bool HasFormulaWithSameRegs(const Formula &F) const; 973 bool InsertFormula(const Formula &F); 974 void DeleteFormula(Formula &F); 975 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses); 976 977 void check() const; 978 979 void print(raw_ostream &OS) const; 980 void dump() const; 981}; 982 983/// HasFormula - Test whether this use as a formula which has the same 984/// registers as the given formula. 985bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const { 986 SmallVector<const SCEV *, 2> Key = F.BaseRegs; 987 if (F.ScaledReg) Key.push_back(F.ScaledReg); 988 // Unstable sort by host order ok, because this is only used for uniquifying. 989 std::sort(Key.begin(), Key.end()); 990 return Uniquifier.count(Key); 991} 992 993/// InsertFormula - If the given formula has not yet been inserted, add it to 994/// the list, and return true. Return false otherwise. 995bool LSRUse::InsertFormula(const Formula &F) { 996 SmallVector<const SCEV *, 2> Key = F.BaseRegs; 997 if (F.ScaledReg) Key.push_back(F.ScaledReg); 998 // Unstable sort by host order ok, because this is only used for uniquifying. 999 std::sort(Key.begin(), Key.end()); 1000 1001 if (!Uniquifier.insert(Key).second) 1002 return false; 1003 1004 // Using a register to hold the value of 0 is not profitable. 1005 assert((!F.ScaledReg || !F.ScaledReg->isZero()) && 1006 "Zero allocated in a scaled register!"); 1007#ifndef NDEBUG 1008 for (SmallVectorImpl<const SCEV *>::const_iterator I = 1009 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) 1010 assert(!(*I)->isZero() && "Zero allocated in a base register!"); 1011#endif 1012 1013 // Add the formula to the list. 1014 Formulae.push_back(F); 1015 1016 // Record registers now being used by this use. 1017 if (F.ScaledReg) Regs.insert(F.ScaledReg); 1018 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); 1019 1020 return true; 1021} 1022 1023/// DeleteFormula - Remove the given formula from this use's list. 1024void LSRUse::DeleteFormula(Formula &F) { 1025 if (&F != &Formulae.back()) 1026 std::swap(F, Formulae.back()); 1027 Formulae.pop_back(); 1028 assert(!Formulae.empty() && "LSRUse has no formulae left!"); 1029} 1030 1031/// RecomputeRegs - Recompute the Regs field, and update RegUses. 1032void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) { 1033 // Now that we've filtered out some formulae, recompute the Regs set. 1034 SmallPtrSet<const SCEV *, 4> OldRegs = Regs; 1035 Regs.clear(); 1036 for (size_t FIdx = 0, NumForms = Formulae.size(); FIdx != NumForms; ++FIdx) { 1037 Formula &F = Formulae[FIdx]; 1038 if (F.ScaledReg) Regs.insert(F.ScaledReg); 1039 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); 1040 } 1041 1042 // Update the RegTracker. 1043 for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(), 1044 E = OldRegs.end(); I != E; ++I) 1045 if (!Regs.count(*I)) 1046 RegUses.DropRegister(*I, LUIdx); 1047} 1048 1049void LSRUse::print(raw_ostream &OS) const { 1050 OS << "LSR Use: Kind="; 1051 switch (Kind) { 1052 case Basic: OS << "Basic"; break; 1053 case Special: OS << "Special"; break; 1054 case ICmpZero: OS << "ICmpZero"; break; 1055 case Address: 1056 OS << "Address of "; 1057 if (AccessTy->isPointerTy()) 1058 OS << "pointer"; // the full pointer type could be really verbose 1059 else 1060 OS << *AccessTy; 1061 } 1062 1063 OS << ", Offsets={"; 1064 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(), 1065 E = Offsets.end(); I != E; ++I) { 1066 OS << *I; 1067 if (next(I) != E) 1068 OS << ','; 1069 } 1070 OS << '}'; 1071 1072 if (AllFixupsOutsideLoop) 1073 OS << ", all-fixups-outside-loop"; 1074} 1075 1076void LSRUse::dump() const { 1077 print(errs()); errs() << '\n'; 1078} 1079 1080/// isLegalUse - Test whether the use described by AM is "legal", meaning it can 1081/// be completely folded into the user instruction at isel time. This includes 1082/// address-mode folding and special icmp tricks. 1083static bool isLegalUse(const TargetLowering::AddrMode &AM, 1084 LSRUse::KindType Kind, const Type *AccessTy, 1085 const TargetLowering *TLI) { 1086 switch (Kind) { 1087 case LSRUse::Address: 1088 // If we have low-level target information, ask the target if it can 1089 // completely fold this address. 1090 if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy); 1091 1092 // Otherwise, just guess that reg+reg addressing is legal. 1093 return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1; 1094 1095 case LSRUse::ICmpZero: 1096 // There's not even a target hook for querying whether it would be legal to 1097 // fold a GV into an ICmp. 1098 if (AM.BaseGV) 1099 return false; 1100 1101 // ICmp only has two operands; don't allow more than two non-trivial parts. 1102 if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0) 1103 return false; 1104 1105 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by 1106 // putting the scaled register in the other operand of the icmp. 1107 if (AM.Scale != 0 && AM.Scale != -1) 1108 return false; 1109 1110 // If we have low-level target information, ask the target if it can fold an 1111 // integer immediate on an icmp. 1112 if (AM.BaseOffs != 0) { 1113 if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs); 1114 return false; 1115 } 1116 1117 return true; 1118 1119 case LSRUse::Basic: 1120 // Only handle single-register values. 1121 return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0; 1122 1123 case LSRUse::Special: 1124 // Only handle -1 scales, or no scale. 1125 return AM.Scale == 0 || AM.Scale == -1; 1126 } 1127 1128 return false; 1129} 1130 1131static bool isLegalUse(TargetLowering::AddrMode AM, 1132 int64_t MinOffset, int64_t MaxOffset, 1133 LSRUse::KindType Kind, const Type *AccessTy, 1134 const TargetLowering *TLI) { 1135 // Check for overflow. 1136 if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) != 1137 (MinOffset > 0)) 1138 return false; 1139 AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset; 1140 if (isLegalUse(AM, Kind, AccessTy, TLI)) { 1141 AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset; 1142 // Check for overflow. 1143 if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) != 1144 (MaxOffset > 0)) 1145 return false; 1146 AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset; 1147 return isLegalUse(AM, Kind, AccessTy, TLI); 1148 } 1149 return false; 1150} 1151 1152static bool isAlwaysFoldable(int64_t BaseOffs, 1153 GlobalValue *BaseGV, 1154 bool HasBaseReg, 1155 LSRUse::KindType Kind, const Type *AccessTy, 1156 const TargetLowering *TLI) { 1157 // Fast-path: zero is always foldable. 1158 if (BaseOffs == 0 && !BaseGV) return true; 1159 1160 // Conservatively, create an address with an immediate and a 1161 // base and a scale. 1162 TargetLowering::AddrMode AM; 1163 AM.BaseOffs = BaseOffs; 1164 AM.BaseGV = BaseGV; 1165 AM.HasBaseReg = HasBaseReg; 1166 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1; 1167 1168 // Canonicalize a scale of 1 to a base register if the formula doesn't 1169 // already have a base register. 1170 if (!AM.HasBaseReg && AM.Scale == 1) { 1171 AM.Scale = 0; 1172 AM.HasBaseReg = true; 1173 } 1174 1175 return isLegalUse(AM, Kind, AccessTy, TLI); 1176} 1177 1178static bool isAlwaysFoldable(const SCEV *S, 1179 int64_t MinOffset, int64_t MaxOffset, 1180 bool HasBaseReg, 1181 LSRUse::KindType Kind, const Type *AccessTy, 1182 const TargetLowering *TLI, 1183 ScalarEvolution &SE) { 1184 // Fast-path: zero is always foldable. 1185 if (S->isZero()) return true; 1186 1187 // Conservatively, create an address with an immediate and a 1188 // base and a scale. 1189 int64_t BaseOffs = ExtractImmediate(S, SE); 1190 GlobalValue *BaseGV = ExtractSymbol(S, SE); 1191 1192 // If there's anything else involved, it's not foldable. 1193 if (!S->isZero()) return false; 1194 1195 // Fast-path: zero is always foldable. 1196 if (BaseOffs == 0 && !BaseGV) return true; 1197 1198 // Conservatively, create an address with an immediate and a 1199 // base and a scale. 1200 TargetLowering::AddrMode AM; 1201 AM.BaseOffs = BaseOffs; 1202 AM.BaseGV = BaseGV; 1203 AM.HasBaseReg = HasBaseReg; 1204 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1; 1205 1206 return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI); 1207} 1208 1209/// FormulaSorter - This class implements an ordering for formulae which sorts 1210/// the by their standalone cost. 1211class FormulaSorter { 1212 /// These two sets are kept empty, so that we compute standalone costs. 1213 DenseSet<const SCEV *> VisitedRegs; 1214 SmallPtrSet<const SCEV *, 16> Regs; 1215 Loop *L; 1216 LSRUse *LU; 1217 ScalarEvolution &SE; 1218 DominatorTree &DT; 1219 1220public: 1221 FormulaSorter(Loop *l, LSRUse &lu, ScalarEvolution &se, DominatorTree &dt) 1222 : L(l), LU(&lu), SE(se), DT(dt) {} 1223 1224 bool operator()(const Formula &A, const Formula &B) { 1225 Cost CostA; 1226 CostA.RateFormula(A, Regs, VisitedRegs, L, LU->Offsets, SE, DT); 1227 Regs.clear(); 1228 Cost CostB; 1229 CostB.RateFormula(B, Regs, VisitedRegs, L, LU->Offsets, SE, DT); 1230 Regs.clear(); 1231 return CostA < CostB; 1232 } 1233}; 1234 1235/// LSRInstance - This class holds state for the main loop strength reduction 1236/// logic. 1237class LSRInstance { 1238 IVUsers &IU; 1239 ScalarEvolution &SE; 1240 DominatorTree &DT; 1241 LoopInfo &LI; 1242 const TargetLowering *const TLI; 1243 Loop *const L; 1244 bool Changed; 1245 1246 /// IVIncInsertPos - This is the insert position that the current loop's 1247 /// induction variable increment should be placed. In simple loops, this is 1248 /// the latch block's terminator. But in more complicated cases, this is a 1249 /// position which will dominate all the in-loop post-increment users. 1250 Instruction *IVIncInsertPos; 1251 1252 /// Factors - Interesting factors between use strides. 1253 SmallSetVector<int64_t, 8> Factors; 1254 1255 /// Types - Interesting use types, to facilitate truncation reuse. 1256 SmallSetVector<const Type *, 4> Types; 1257 1258 /// Fixups - The list of operands which are to be replaced. 1259 SmallVector<LSRFixup, 16> Fixups; 1260 1261 /// Uses - The list of interesting uses. 1262 SmallVector<LSRUse, 16> Uses; 1263 1264 /// RegUses - Track which uses use which register candidates. 1265 RegUseTracker RegUses; 1266 1267 void OptimizeShadowIV(); 1268 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse); 1269 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse); 1270 bool OptimizeLoopTermCond(); 1271 1272 void CollectInterestingTypesAndFactors(); 1273 void CollectFixupsAndInitialFormulae(); 1274 1275 LSRFixup &getNewFixup() { 1276 Fixups.push_back(LSRFixup()); 1277 return Fixups.back(); 1278 } 1279 1280 // Support for sharing of LSRUses between LSRFixups. 1281 typedef DenseMap<const SCEV *, size_t> UseMapTy; 1282 UseMapTy UseMap; 1283 1284 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, 1285 bool HasBaseReg, 1286 LSRUse::KindType Kind, const Type *AccessTy); 1287 1288 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, 1289 LSRUse::KindType Kind, 1290 const Type *AccessTy); 1291 1292 void DeleteUse(LSRUse &LU); 1293 1294 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU); 1295 1296public: 1297 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); 1298 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); 1299 void CountRegisters(const Formula &F, size_t LUIdx); 1300 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F); 1301 1302 void CollectLoopInvariantFixupsAndFormulae(); 1303 1304 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base, 1305 unsigned Depth = 0); 1306 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base); 1307 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); 1308 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); 1309 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base); 1310 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base); 1311 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base); 1312 void GenerateCrossUseConstantOffsets(); 1313 void GenerateAllReuseFormulae(); 1314 1315 void FilterOutUndesirableDedicatedRegisters(); 1316 1317 size_t EstimateSearchSpaceComplexity() const; 1318 void NarrowSearchSpaceUsingHeuristics(); 1319 1320 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution, 1321 Cost &SolutionCost, 1322 SmallVectorImpl<const Formula *> &Workspace, 1323 const Cost &CurCost, 1324 const SmallPtrSet<const SCEV *, 16> &CurRegs, 1325 DenseSet<const SCEV *> &VisitedRegs) const; 1326 void Solve(SmallVectorImpl<const Formula *> &Solution) const; 1327 1328 BasicBlock::iterator 1329 HoistInsertPosition(BasicBlock::iterator IP, 1330 const SmallVectorImpl<Instruction *> &Inputs) const; 1331 BasicBlock::iterator AdjustInsertPositionForExpand(BasicBlock::iterator IP, 1332 const LSRFixup &LF, 1333 const LSRUse &LU) const; 1334 1335 Value *Expand(const LSRFixup &LF, 1336 const Formula &F, 1337 BasicBlock::iterator IP, 1338 SCEVExpander &Rewriter, 1339 SmallVectorImpl<WeakVH> &DeadInsts) const; 1340 void RewriteForPHI(PHINode *PN, const LSRFixup &LF, 1341 const Formula &F, 1342 SCEVExpander &Rewriter, 1343 SmallVectorImpl<WeakVH> &DeadInsts, 1344 Pass *P) const; 1345 void Rewrite(const LSRFixup &LF, 1346 const Formula &F, 1347 SCEVExpander &Rewriter, 1348 SmallVectorImpl<WeakVH> &DeadInsts, 1349 Pass *P) const; 1350 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution, 1351 Pass *P); 1352 1353 LSRInstance(const TargetLowering *tli, Loop *l, Pass *P); 1354 1355 bool getChanged() const { return Changed; } 1356 1357 void print_factors_and_types(raw_ostream &OS) const; 1358 void print_fixups(raw_ostream &OS) const; 1359 void print_uses(raw_ostream &OS) const; 1360 void print(raw_ostream &OS) const; 1361 void dump() const; 1362}; 1363 1364} 1365 1366/// OptimizeShadowIV - If IV is used in a int-to-float cast 1367/// inside the loop then try to eliminate the cast operation. 1368void LSRInstance::OptimizeShadowIV() { 1369 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); 1370 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) 1371 return; 1372 1373 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); 1374 UI != E; /* empty */) { 1375 IVUsers::const_iterator CandidateUI = UI; 1376 ++UI; 1377 Instruction *ShadowUse = CandidateUI->getUser(); 1378 const Type *DestTy = NULL; 1379 1380 /* If shadow use is a int->float cast then insert a second IV 1381 to eliminate this cast. 1382 1383 for (unsigned i = 0; i < n; ++i) 1384 foo((double)i); 1385 1386 is transformed into 1387 1388 double d = 0.0; 1389 for (unsigned i = 0; i < n; ++i, ++d) 1390 foo(d); 1391 */ 1392 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) 1393 DestTy = UCast->getDestTy(); 1394 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) 1395 DestTy = SCast->getDestTy(); 1396 if (!DestTy) continue; 1397 1398 if (TLI) { 1399 // If target does not support DestTy natively then do not apply 1400 // this transformation. 1401 EVT DVT = TLI->getValueType(DestTy); 1402 if (!TLI->isTypeLegal(DVT)) continue; 1403 } 1404 1405 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0)); 1406 if (!PH) continue; 1407 if (PH->getNumIncomingValues() != 2) continue; 1408 1409 const Type *SrcTy = PH->getType(); 1410 int Mantissa = DestTy->getFPMantissaWidth(); 1411 if (Mantissa == -1) continue; 1412 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa) 1413 continue; 1414 1415 unsigned Entry, Latch; 1416 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) { 1417 Entry = 0; 1418 Latch = 1; 1419 } else { 1420 Entry = 1; 1421 Latch = 0; 1422 } 1423 1424 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry)); 1425 if (!Init) continue; 1426 Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue()); 1427 1428 BinaryOperator *Incr = 1429 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch)); 1430 if (!Incr) continue; 1431 if (Incr->getOpcode() != Instruction::Add 1432 && Incr->getOpcode() != Instruction::Sub) 1433 continue; 1434 1435 /* Initialize new IV, double d = 0.0 in above example. */ 1436 ConstantInt *C = NULL; 1437 if (Incr->getOperand(0) == PH) 1438 C = dyn_cast<ConstantInt>(Incr->getOperand(1)); 1439 else if (Incr->getOperand(1) == PH) 1440 C = dyn_cast<ConstantInt>(Incr->getOperand(0)); 1441 else 1442 continue; 1443 1444 if (!C) continue; 1445 1446 // Ignore negative constants, as the code below doesn't handle them 1447 // correctly. TODO: Remove this restriction. 1448 if (!C->getValue().isStrictlyPositive()) continue; 1449 1450 /* Add new PHINode. */ 1451 PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH); 1452 1453 /* create new increment. '++d' in above example. */ 1454 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue()); 1455 BinaryOperator *NewIncr = 1456 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ? 1457 Instruction::FAdd : Instruction::FSub, 1458 NewPH, CFP, "IV.S.next.", Incr); 1459 1460 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry)); 1461 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch)); 1462 1463 /* Remove cast operation */ 1464 ShadowUse->replaceAllUsesWith(NewPH); 1465 ShadowUse->eraseFromParent(); 1466 break; 1467 } 1468} 1469 1470/// FindIVUserForCond - If Cond has an operand that is an expression of an IV, 1471/// set the IV user and stride information and return true, otherwise return 1472/// false. 1473bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, 1474 IVStrideUse *&CondUse) { 1475 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) 1476 if (UI->getUser() == Cond) { 1477 // NOTE: we could handle setcc instructions with multiple uses here, but 1478 // InstCombine does it as well for simple uses, it's not clear that it 1479 // occurs enough in real life to handle. 1480 CondUse = UI; 1481 return true; 1482 } 1483 return false; 1484} 1485 1486/// OptimizeMax - Rewrite the loop's terminating condition if it uses 1487/// a max computation. 1488/// 1489/// This is a narrow solution to a specific, but acute, problem. For loops 1490/// like this: 1491/// 1492/// i = 0; 1493/// do { 1494/// p[i] = 0.0; 1495/// } while (++i < n); 1496/// 1497/// the trip count isn't just 'n', because 'n' might not be positive. And 1498/// unfortunately this can come up even for loops where the user didn't use 1499/// a C do-while loop. For example, seemingly well-behaved top-test loops 1500/// will commonly be lowered like this: 1501// 1502/// if (n > 0) { 1503/// i = 0; 1504/// do { 1505/// p[i] = 0.0; 1506/// } while (++i < n); 1507/// } 1508/// 1509/// and then it's possible for subsequent optimization to obscure the if 1510/// test in such a way that indvars can't find it. 1511/// 1512/// When indvars can't find the if test in loops like this, it creates a 1513/// max expression, which allows it to give the loop a canonical 1514/// induction variable: 1515/// 1516/// i = 0; 1517/// max = n < 1 ? 1 : n; 1518/// do { 1519/// p[i] = 0.0; 1520/// } while (++i != max); 1521/// 1522/// Canonical induction variables are necessary because the loop passes 1523/// are designed around them. The most obvious example of this is the 1524/// LoopInfo analysis, which doesn't remember trip count values. It 1525/// expects to be able to rediscover the trip count each time it is 1526/// needed, and it does this using a simple analysis that only succeeds if 1527/// the loop has a canonical induction variable. 1528/// 1529/// However, when it comes time to generate code, the maximum operation 1530/// can be quite costly, especially if it's inside of an outer loop. 1531/// 1532/// This function solves this problem by detecting this type of loop and 1533/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting 1534/// the instructions for the maximum computation. 1535/// 1536ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) { 1537 // Check that the loop matches the pattern we're looking for. 1538 if (Cond->getPredicate() != CmpInst::ICMP_EQ && 1539 Cond->getPredicate() != CmpInst::ICMP_NE) 1540 return Cond; 1541 1542 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1)); 1543 if (!Sel || !Sel->hasOneUse()) return Cond; 1544 1545 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); 1546 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) 1547 return Cond; 1548 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1); 1549 1550 // Add one to the backedge-taken count to get the trip count. 1551 const SCEV *IterationCount = SE.getAddExpr(BackedgeTakenCount, One); 1552 if (IterationCount != SE.getSCEV(Sel)) return Cond; 1553 1554 // Check for a max calculation that matches the pattern. There's no check 1555 // for ICMP_ULE here because the comparison would be with zero, which 1556 // isn't interesting. 1557 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE; 1558 const SCEVNAryExpr *Max = 0; 1559 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) { 1560 Pred = ICmpInst::ICMP_SLE; 1561 Max = S; 1562 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) { 1563 Pred = ICmpInst::ICMP_SLT; 1564 Max = S; 1565 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) { 1566 Pred = ICmpInst::ICMP_ULT; 1567 Max = U; 1568 } else { 1569 // No match; bail. 1570 return Cond; 1571 } 1572 1573 // To handle a max with more than two operands, this optimization would 1574 // require additional checking and setup. 1575 if (Max->getNumOperands() != 2) 1576 return Cond; 1577 1578 const SCEV *MaxLHS = Max->getOperand(0); 1579 const SCEV *MaxRHS = Max->getOperand(1); 1580 1581 // ScalarEvolution canonicalizes constants to the left. For < and >, look 1582 // for a comparison with 1. For <= and >=, a comparison with zero. 1583 if (!MaxLHS || 1584 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One))) 1585 return Cond; 1586 1587 // Check the relevant induction variable for conformance to 1588 // the pattern. 1589 const SCEV *IV = SE.getSCEV(Cond->getOperand(0)); 1590 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV); 1591 if (!AR || !AR->isAffine() || 1592 AR->getStart() != One || 1593 AR->getStepRecurrence(SE) != One) 1594 return Cond; 1595 1596 assert(AR->getLoop() == L && 1597 "Loop condition operand is an addrec in a different loop!"); 1598 1599 // Check the right operand of the select, and remember it, as it will 1600 // be used in the new comparison instruction. 1601 Value *NewRHS = 0; 1602 if (ICmpInst::isTrueWhenEqual(Pred)) { 1603 // Look for n+1, and grab n. 1604 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1))) 1605 if (isa<ConstantInt>(BO->getOperand(1)) && 1606 cast<ConstantInt>(BO->getOperand(1))->isOne() && 1607 SE.getSCEV(BO->getOperand(0)) == MaxRHS) 1608 NewRHS = BO->getOperand(0); 1609 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2))) 1610 if (isa<ConstantInt>(BO->getOperand(1)) && 1611 cast<ConstantInt>(BO->getOperand(1))->isOne() && 1612 SE.getSCEV(BO->getOperand(0)) == MaxRHS) 1613 NewRHS = BO->getOperand(0); 1614 if (!NewRHS) 1615 return Cond; 1616 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS) 1617 NewRHS = Sel->getOperand(1); 1618 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS) 1619 NewRHS = Sel->getOperand(2); 1620 else 1621 llvm_unreachable("Max doesn't match expected pattern!"); 1622 1623 // Determine the new comparison opcode. It may be signed or unsigned, 1624 // and the original comparison may be either equality or inequality. 1625 if (Cond->getPredicate() == CmpInst::ICMP_EQ) 1626 Pred = CmpInst::getInversePredicate(Pred); 1627 1628 // Ok, everything looks ok to change the condition into an SLT or SGE and 1629 // delete the max calculation. 1630 ICmpInst *NewCond = 1631 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp"); 1632 1633 // Delete the max calculation instructions. 1634 Cond->replaceAllUsesWith(NewCond); 1635 CondUse->setUser(NewCond); 1636 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0)); 1637 Cond->eraseFromParent(); 1638 Sel->eraseFromParent(); 1639 if (Cmp->use_empty()) 1640 Cmp->eraseFromParent(); 1641 return NewCond; 1642} 1643 1644/// OptimizeLoopTermCond - Change loop terminating condition to use the 1645/// postinc iv when possible. 1646bool 1647LSRInstance::OptimizeLoopTermCond() { 1648 SmallPtrSet<Instruction *, 4> PostIncs; 1649 1650 BasicBlock *LatchBlock = L->getLoopLatch(); 1651 SmallVector<BasicBlock*, 8> ExitingBlocks; 1652 L->getExitingBlocks(ExitingBlocks); 1653 1654 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) { 1655 BasicBlock *ExitingBlock = ExitingBlocks[i]; 1656 1657 // Get the terminating condition for the loop if possible. If we 1658 // can, we want to change it to use a post-incremented version of its 1659 // induction variable, to allow coalescing the live ranges for the IV into 1660 // one register value. 1661 1662 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator()); 1663 if (!TermBr) 1664 continue; 1665 // FIXME: Overly conservative, termination condition could be an 'or' etc.. 1666 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition())) 1667 continue; 1668 1669 // Search IVUsesByStride to find Cond's IVUse if there is one. 1670 IVStrideUse *CondUse = 0; 1671 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition()); 1672 if (!FindIVUserForCond(Cond, CondUse)) 1673 continue; 1674 1675 // If the trip count is computed in terms of a max (due to ScalarEvolution 1676 // being unable to find a sufficient guard, for example), change the loop 1677 // comparison to use SLT or ULT instead of NE. 1678 // One consequence of doing this now is that it disrupts the count-down 1679 // optimization. That's not always a bad thing though, because in such 1680 // cases it may still be worthwhile to avoid a max. 1681 Cond = OptimizeMax(Cond, CondUse); 1682 1683 // If this exiting block dominates the latch block, it may also use 1684 // the post-inc value if it won't be shared with other uses. 1685 // Check for dominance. 1686 if (!DT.dominates(ExitingBlock, LatchBlock)) 1687 continue; 1688 1689 // Conservatively avoid trying to use the post-inc value in non-latch 1690 // exits if there may be pre-inc users in intervening blocks. 1691 if (LatchBlock != ExitingBlock) 1692 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) 1693 // Test if the use is reachable from the exiting block. This dominator 1694 // query is a conservative approximation of reachability. 1695 if (&*UI != CondUse && 1696 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) { 1697 // Conservatively assume there may be reuse if the quotient of their 1698 // strides could be a legal scale. 1699 const SCEV *A = IU.getStride(*CondUse, L); 1700 const SCEV *B = IU.getStride(*UI, L); 1701 if (!A || !B) continue; 1702 if (SE.getTypeSizeInBits(A->getType()) != 1703 SE.getTypeSizeInBits(B->getType())) { 1704 if (SE.getTypeSizeInBits(A->getType()) > 1705 SE.getTypeSizeInBits(B->getType())) 1706 B = SE.getSignExtendExpr(B, A->getType()); 1707 else 1708 A = SE.getSignExtendExpr(A, B->getType()); 1709 } 1710 if (const SCEVConstant *D = 1711 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) { 1712 // Stride of one or negative one can have reuse with non-addresses. 1713 if (D->getValue()->isOne() || 1714 D->getValue()->isAllOnesValue()) 1715 goto decline_post_inc; 1716 // Avoid weird situations. 1717 if (D->getValue()->getValue().getMinSignedBits() >= 64 || 1718 D->getValue()->getValue().isMinSignedValue()) 1719 goto decline_post_inc; 1720 // Without TLI, assume that any stride might be valid, and so any 1721 // use might be shared. 1722 if (!TLI) 1723 goto decline_post_inc; 1724 // Check for possible scaled-address reuse. 1725 const Type *AccessTy = getAccessType(UI->getUser()); 1726 TargetLowering::AddrMode AM; 1727 AM.Scale = D->getValue()->getSExtValue(); 1728 if (TLI->isLegalAddressingMode(AM, AccessTy)) 1729 goto decline_post_inc; 1730 AM.Scale = -AM.Scale; 1731 if (TLI->isLegalAddressingMode(AM, AccessTy)) 1732 goto decline_post_inc; 1733 } 1734 } 1735 1736 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: " 1737 << *Cond << '\n'); 1738 1739 // It's possible for the setcc instruction to be anywhere in the loop, and 1740 // possible for it to have multiple users. If it is not immediately before 1741 // the exiting block branch, move it. 1742 if (&*++BasicBlock::iterator(Cond) != TermBr) { 1743 if (Cond->hasOneUse()) { 1744 Cond->moveBefore(TermBr); 1745 } else { 1746 // Clone the terminating condition and insert into the loopend. 1747 ICmpInst *OldCond = Cond; 1748 Cond = cast<ICmpInst>(Cond->clone()); 1749 Cond->setName(L->getHeader()->getName() + ".termcond"); 1750 ExitingBlock->getInstList().insert(TermBr, Cond); 1751 1752 // Clone the IVUse, as the old use still exists! 1753 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace()); 1754 TermBr->replaceUsesOfWith(OldCond, Cond); 1755 } 1756 } 1757 1758 // If we get to here, we know that we can transform the setcc instruction to 1759 // use the post-incremented version of the IV, allowing us to coalesce the 1760 // live ranges for the IV correctly. 1761 CondUse->transformToPostInc(L); 1762 Changed = true; 1763 1764 PostIncs.insert(Cond); 1765 decline_post_inc:; 1766 } 1767 1768 // Determine an insertion point for the loop induction variable increment. It 1769 // must dominate all the post-inc comparisons we just set up, and it must 1770 // dominate the loop latch edge. 1771 IVIncInsertPos = L->getLoopLatch()->getTerminator(); 1772 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(), 1773 E = PostIncs.end(); I != E; ++I) { 1774 BasicBlock *BB = 1775 DT.findNearestCommonDominator(IVIncInsertPos->getParent(), 1776 (*I)->getParent()); 1777 if (BB == (*I)->getParent()) 1778 IVIncInsertPos = *I; 1779 else if (BB != IVIncInsertPos->getParent()) 1780 IVIncInsertPos = BB->getTerminator(); 1781 } 1782 1783 return Changed; 1784} 1785 1786bool 1787LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, 1788 bool HasBaseReg, 1789 LSRUse::KindType Kind, const Type *AccessTy) { 1790 int64_t NewMinOffset = LU.MinOffset; 1791 int64_t NewMaxOffset = LU.MaxOffset; 1792 const Type *NewAccessTy = AccessTy; 1793 1794 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to 1795 // something conservative, however this can pessimize in the case that one of 1796 // the uses will have all its uses outside the loop, for example. 1797 if (LU.Kind != Kind) 1798 return false; 1799 // Conservatively assume HasBaseReg is true for now. 1800 if (NewOffset < LU.MinOffset) { 1801 if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg, 1802 Kind, AccessTy, TLI)) 1803 return false; 1804 NewMinOffset = NewOffset; 1805 } else if (NewOffset > LU.MaxOffset) { 1806 if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg, 1807 Kind, AccessTy, TLI)) 1808 return false; 1809 NewMaxOffset = NewOffset; 1810 } 1811 // Check for a mismatched access type, and fall back conservatively as needed. 1812 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy) 1813 NewAccessTy = Type::getVoidTy(AccessTy->getContext()); 1814 1815 // Update the use. 1816 LU.MinOffset = NewMinOffset; 1817 LU.MaxOffset = NewMaxOffset; 1818 LU.AccessTy = NewAccessTy; 1819 if (NewOffset != LU.Offsets.back()) 1820 LU.Offsets.push_back(NewOffset); 1821 return true; 1822} 1823 1824/// getUse - Return an LSRUse index and an offset value for a fixup which 1825/// needs the given expression, with the given kind and optional access type. 1826/// Either reuse an existing use or create a new one, as needed. 1827std::pair<size_t, int64_t> 1828LSRInstance::getUse(const SCEV *&Expr, 1829 LSRUse::KindType Kind, const Type *AccessTy) { 1830 const SCEV *Copy = Expr; 1831 int64_t Offset = ExtractImmediate(Expr, SE); 1832 1833 // Basic uses can't accept any offset, for example. 1834 if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) { 1835 Expr = Copy; 1836 Offset = 0; 1837 } 1838 1839 std::pair<UseMapTy::iterator, bool> P = 1840 UseMap.insert(std::make_pair(Expr, 0)); 1841 if (!P.second) { 1842 // A use already existed with this base. 1843 size_t LUIdx = P.first->second; 1844 LSRUse &LU = Uses[LUIdx]; 1845 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy)) 1846 // Reuse this use. 1847 return std::make_pair(LUIdx, Offset); 1848 } 1849 1850 // Create a new use. 1851 size_t LUIdx = Uses.size(); 1852 P.first->second = LUIdx; 1853 Uses.push_back(LSRUse(Kind, AccessTy)); 1854 LSRUse &LU = Uses[LUIdx]; 1855 1856 // We don't need to track redundant offsets, but we don't need to go out 1857 // of our way here to avoid them. 1858 if (LU.Offsets.empty() || Offset != LU.Offsets.back()) 1859 LU.Offsets.push_back(Offset); 1860 1861 LU.MinOffset = Offset; 1862 LU.MaxOffset = Offset; 1863 return std::make_pair(LUIdx, Offset); 1864} 1865 1866/// DeleteUse - Delete the given use from the Uses list. 1867void LSRInstance::DeleteUse(LSRUse &LU) { 1868 if (&LU != &Uses.back()) 1869 std::swap(LU, Uses.back()); 1870 Uses.pop_back(); 1871} 1872 1873/// FindUseWithFormula - Look for a use distinct from OrigLU which is has 1874/// a formula that has the same registers as the given formula. 1875LSRUse * 1876LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF, 1877 const LSRUse &OrigLU) { 1878 // Search all uses for the formula. This could be more clever. Ignore 1879 // ICmpZero uses because they may contain formulae generated by 1880 // GenerateICmpZeroScales, in which case adding fixup offsets may 1881 // be invalid. 1882 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 1883 LSRUse &LU = Uses[LUIdx]; 1884 if (&LU != &OrigLU && 1885 LU.Kind != LSRUse::ICmpZero && 1886 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy && 1887 LU.HasFormulaWithSameRegs(OrigF)) { 1888 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); 1889 FIdx != NumForms; ++FIdx) { 1890 Formula &F = LU.Formulae[FIdx]; 1891 if (F.BaseRegs == OrigF.BaseRegs && 1892 F.ScaledReg == OrigF.ScaledReg && 1893 F.AM.BaseGV == OrigF.AM.BaseGV && 1894 F.AM.Scale == OrigF.AM.Scale && 1895 LU.Kind) { 1896 if (F.AM.BaseOffs == 0) 1897 return &LU; 1898 break; 1899 } 1900 } 1901 } 1902 } 1903 1904 return 0; 1905} 1906 1907void LSRInstance::CollectInterestingTypesAndFactors() { 1908 SmallSetVector<const SCEV *, 4> Strides; 1909 1910 // Collect interesting types and strides. 1911 SmallVector<const SCEV *, 4> Worklist; 1912 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { 1913 const SCEV *Expr = IU.getExpr(*UI); 1914 1915 // Collect interesting types. 1916 Types.insert(SE.getEffectiveSCEVType(Expr->getType())); 1917 1918 // Add strides for mentioned loops. 1919 Worklist.push_back(Expr); 1920 do { 1921 const SCEV *S = Worklist.pop_back_val(); 1922 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 1923 Strides.insert(AR->getStepRecurrence(SE)); 1924 Worklist.push_back(AR->getStart()); 1925 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 1926 Worklist.insert(Worklist.end(), Add->op_begin(), Add->op_end()); 1927 } 1928 } while (!Worklist.empty()); 1929 } 1930 1931 // Compute interesting factors from the set of interesting strides. 1932 for (SmallSetVector<const SCEV *, 4>::const_iterator 1933 I = Strides.begin(), E = Strides.end(); I != E; ++I) 1934 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter = 1935 next(I); NewStrideIter != E; ++NewStrideIter) { 1936 const SCEV *OldStride = *I; 1937 const SCEV *NewStride = *NewStrideIter; 1938 1939 if (SE.getTypeSizeInBits(OldStride->getType()) != 1940 SE.getTypeSizeInBits(NewStride->getType())) { 1941 if (SE.getTypeSizeInBits(OldStride->getType()) > 1942 SE.getTypeSizeInBits(NewStride->getType())) 1943 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType()); 1944 else 1945 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType()); 1946 } 1947 if (const SCEVConstant *Factor = 1948 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride, 1949 SE, true))) { 1950 if (Factor->getValue()->getValue().getMinSignedBits() <= 64) 1951 Factors.insert(Factor->getValue()->getValue().getSExtValue()); 1952 } else if (const SCEVConstant *Factor = 1953 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride, 1954 NewStride, 1955 SE, true))) { 1956 if (Factor->getValue()->getValue().getMinSignedBits() <= 64) 1957 Factors.insert(Factor->getValue()->getValue().getSExtValue()); 1958 } 1959 } 1960 1961 // If all uses use the same type, don't bother looking for truncation-based 1962 // reuse. 1963 if (Types.size() == 1) 1964 Types.clear(); 1965 1966 DEBUG(print_factors_and_types(dbgs())); 1967} 1968 1969void LSRInstance::CollectFixupsAndInitialFormulae() { 1970 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { 1971 // Record the uses. 1972 LSRFixup &LF = getNewFixup(); 1973 LF.UserInst = UI->getUser(); 1974 LF.OperandValToReplace = UI->getOperandValToReplace(); 1975 LF.PostIncLoops = UI->getPostIncLoops(); 1976 1977 LSRUse::KindType Kind = LSRUse::Basic; 1978 const Type *AccessTy = 0; 1979 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) { 1980 Kind = LSRUse::Address; 1981 AccessTy = getAccessType(LF.UserInst); 1982 } 1983 1984 const SCEV *S = IU.getExpr(*UI); 1985 1986 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as 1987 // (N - i == 0), and this allows (N - i) to be the expression that we work 1988 // with rather than just N or i, so we can consider the register 1989 // requirements for both N and i at the same time. Limiting this code to 1990 // equality icmps is not a problem because all interesting loops use 1991 // equality icmps, thanks to IndVarSimplify. 1992 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst)) 1993 if (CI->isEquality()) { 1994 // Swap the operands if needed to put the OperandValToReplace on the 1995 // left, for consistency. 1996 Value *NV = CI->getOperand(1); 1997 if (NV == LF.OperandValToReplace) { 1998 CI->setOperand(1, CI->getOperand(0)); 1999 CI->setOperand(0, NV); 2000 NV = CI->getOperand(1); 2001 Changed = true; 2002 } 2003 2004 // x == y --> x - y == 0 2005 const SCEV *N = SE.getSCEV(NV); 2006 if (N->isLoopInvariant(L)) { 2007 Kind = LSRUse::ICmpZero; 2008 S = SE.getMinusSCEV(N, S); 2009 } 2010 2011 // -1 and the negations of all interesting strides (except the negation 2012 // of -1) are now also interesting. 2013 for (size_t i = 0, e = Factors.size(); i != e; ++i) 2014 if (Factors[i] != -1) 2015 Factors.insert(-(uint64_t)Factors[i]); 2016 Factors.insert(-1); 2017 } 2018 2019 // Set up the initial formula for this use. 2020 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy); 2021 LF.LUIdx = P.first; 2022 LF.Offset = P.second; 2023 LSRUse &LU = Uses[LF.LUIdx]; 2024 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L); 2025 2026 // If this is the first use of this LSRUse, give it a formula. 2027 if (LU.Formulae.empty()) { 2028 InsertInitialFormula(S, LU, LF.LUIdx); 2029 CountRegisters(LU.Formulae.back(), LF.LUIdx); 2030 } 2031 } 2032 2033 DEBUG(print_fixups(dbgs())); 2034} 2035 2036void 2037LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) { 2038 Formula F; 2039 F.InitialMatch(S, L, SE, DT); 2040 bool Inserted = InsertFormula(LU, LUIdx, F); 2041 assert(Inserted && "Initial formula already exists!"); (void)Inserted; 2042} 2043 2044void 2045LSRInstance::InsertSupplementalFormula(const SCEV *S, 2046 LSRUse &LU, size_t LUIdx) { 2047 Formula F; 2048 F.BaseRegs.push_back(S); 2049 F.AM.HasBaseReg = true; 2050 bool Inserted = InsertFormula(LU, LUIdx, F); 2051 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted; 2052} 2053 2054/// CountRegisters - Note which registers are used by the given formula, 2055/// updating RegUses. 2056void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) { 2057 if (F.ScaledReg) 2058 RegUses.CountRegister(F.ScaledReg, LUIdx); 2059 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), 2060 E = F.BaseRegs.end(); I != E; ++I) 2061 RegUses.CountRegister(*I, LUIdx); 2062} 2063 2064/// InsertFormula - If the given formula has not yet been inserted, add it to 2065/// the list, and return true. Return false otherwise. 2066bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) { 2067 if (!LU.InsertFormula(F)) 2068 return false; 2069 2070 CountRegisters(F, LUIdx); 2071 return true; 2072} 2073 2074/// CollectLoopInvariantFixupsAndFormulae - Check for other uses of 2075/// loop-invariant values which we're tracking. These other uses will pin these 2076/// values in registers, making them less profitable for elimination. 2077/// TODO: This currently misses non-constant addrec step registers. 2078/// TODO: Should this give more weight to users inside the loop? 2079void 2080LSRInstance::CollectLoopInvariantFixupsAndFormulae() { 2081 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end()); 2082 SmallPtrSet<const SCEV *, 8> Inserted; 2083 2084 while (!Worklist.empty()) { 2085 const SCEV *S = Worklist.pop_back_val(); 2086 2087 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) 2088 Worklist.insert(Worklist.end(), N->op_begin(), N->op_end()); 2089 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S)) 2090 Worklist.push_back(C->getOperand()); 2091 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) { 2092 Worklist.push_back(D->getLHS()); 2093 Worklist.push_back(D->getRHS()); 2094 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { 2095 if (!Inserted.insert(U)) continue; 2096 const Value *V = U->getValue(); 2097 if (const Instruction *Inst = dyn_cast<Instruction>(V)) 2098 if (L->contains(Inst)) continue; 2099 for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end(); 2100 UI != UE; ++UI) { 2101 const Instruction *UserInst = dyn_cast<Instruction>(*UI); 2102 // Ignore non-instructions. 2103 if (!UserInst) 2104 continue; 2105 // Ignore instructions in other functions (as can happen with 2106 // Constants). 2107 if (UserInst->getParent()->getParent() != L->getHeader()->getParent()) 2108 continue; 2109 // Ignore instructions not dominated by the loop. 2110 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ? 2111 UserInst->getParent() : 2112 cast<PHINode>(UserInst)->getIncomingBlock( 2113 PHINode::getIncomingValueNumForOperand(UI.getOperandNo())); 2114 if (!DT.dominates(L->getHeader(), UseBB)) 2115 continue; 2116 // Ignore uses which are part of other SCEV expressions, to avoid 2117 // analyzing them multiple times. 2118 if (SE.isSCEVable(UserInst->getType())) { 2119 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst)); 2120 // If the user is a no-op, look through to its uses. 2121 if (!isa<SCEVUnknown>(UserS)) 2122 continue; 2123 if (UserS == U) { 2124 Worklist.push_back( 2125 SE.getUnknown(const_cast<Instruction *>(UserInst))); 2126 continue; 2127 } 2128 } 2129 // Ignore icmp instructions which are already being analyzed. 2130 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) { 2131 unsigned OtherIdx = !UI.getOperandNo(); 2132 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx)); 2133 if (SE.getSCEV(OtherOp)->hasComputableLoopEvolution(L)) 2134 continue; 2135 } 2136 2137 LSRFixup &LF = getNewFixup(); 2138 LF.UserInst = const_cast<Instruction *>(UserInst); 2139 LF.OperandValToReplace = UI.getUse(); 2140 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0); 2141 LF.LUIdx = P.first; 2142 LF.Offset = P.second; 2143 LSRUse &LU = Uses[LF.LUIdx]; 2144 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L); 2145 InsertSupplementalFormula(U, LU, LF.LUIdx); 2146 CountRegisters(LU.Formulae.back(), Uses.size() - 1); 2147 break; 2148 } 2149 } 2150 } 2151} 2152 2153/// CollectSubexprs - Split S into subexpressions which can be pulled out into 2154/// separate registers. If C is non-null, multiply each subexpression by C. 2155static void CollectSubexprs(const SCEV *S, const SCEVConstant *C, 2156 SmallVectorImpl<const SCEV *> &Ops, 2157 ScalarEvolution &SE) { 2158 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { 2159 // Break out add operands. 2160 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); 2161 I != E; ++I) 2162 CollectSubexprs(*I, C, Ops, SE); 2163 return; 2164 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { 2165 // Split a non-zero base out of an addrec. 2166 if (!AR->getStart()->isZero()) { 2167 CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0), 2168 AR->getStepRecurrence(SE), 2169 AR->getLoop()), C, Ops, SE); 2170 CollectSubexprs(AR->getStart(), C, Ops, SE); 2171 return; 2172 } 2173 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) { 2174 // Break (C * (a + b + c)) into C*a + C*b + C*c. 2175 if (Mul->getNumOperands() == 2) 2176 if (const SCEVConstant *Op0 = 2177 dyn_cast<SCEVConstant>(Mul->getOperand(0))) { 2178 CollectSubexprs(Mul->getOperand(1), 2179 C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0, 2180 Ops, SE); 2181 return; 2182 } 2183 } 2184 2185 // Otherwise use the value itself. 2186 Ops.push_back(C ? SE.getMulExpr(C, S) : S); 2187} 2188 2189/// GenerateReassociations - Split out subexpressions from adds and the bases of 2190/// addrecs. 2191void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx, 2192 Formula Base, 2193 unsigned Depth) { 2194 // Arbitrarily cap recursion to protect compile time. 2195 if (Depth >= 3) return; 2196 2197 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { 2198 const SCEV *BaseReg = Base.BaseRegs[i]; 2199 2200 SmallVector<const SCEV *, 8> AddOps; 2201 CollectSubexprs(BaseReg, 0, AddOps, SE); 2202 if (AddOps.size() == 1) continue; 2203 2204 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(), 2205 JE = AddOps.end(); J != JE; ++J) { 2206 // Don't pull a constant into a register if the constant could be folded 2207 // into an immediate field. 2208 if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset, 2209 Base.getNumRegs() > 1, 2210 LU.Kind, LU.AccessTy, TLI, SE)) 2211 continue; 2212 2213 // Collect all operands except *J. 2214 SmallVector<const SCEV *, 8> InnerAddOps; 2215 for (SmallVectorImpl<const SCEV *>::const_iterator K = AddOps.begin(), 2216 KE = AddOps.end(); K != KE; ++K) 2217 if (K != J) 2218 InnerAddOps.push_back(*K); 2219 2220 // Don't leave just a constant behind in a register if the constant could 2221 // be folded into an immediate field. 2222 if (InnerAddOps.size() == 1 && 2223 isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset, 2224 Base.getNumRegs() > 1, 2225 LU.Kind, LU.AccessTy, TLI, SE)) 2226 continue; 2227 2228 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps); 2229 if (InnerSum->isZero()) 2230 continue; 2231 Formula F = Base; 2232 F.BaseRegs[i] = InnerSum; 2233 F.BaseRegs.push_back(*J); 2234 if (InsertFormula(LU, LUIdx, F)) 2235 // If that formula hadn't been seen before, recurse to find more like 2236 // it. 2237 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1); 2238 } 2239 } 2240} 2241 2242/// GenerateCombinations - Generate a formula consisting of all of the 2243/// loop-dominating registers added into a single register. 2244void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx, 2245 Formula Base) { 2246 // This method is only interesting on a plurality of registers. 2247 if (Base.BaseRegs.size() <= 1) return; 2248 2249 Formula F = Base; 2250 F.BaseRegs.clear(); 2251 SmallVector<const SCEV *, 4> Ops; 2252 for (SmallVectorImpl<const SCEV *>::const_iterator 2253 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) { 2254 const SCEV *BaseReg = *I; 2255 if (BaseReg->properlyDominates(L->getHeader(), &DT) && 2256 !BaseReg->hasComputableLoopEvolution(L)) 2257 Ops.push_back(BaseReg); 2258 else 2259 F.BaseRegs.push_back(BaseReg); 2260 } 2261 if (Ops.size() > 1) { 2262 const SCEV *Sum = SE.getAddExpr(Ops); 2263 // TODO: If Sum is zero, it probably means ScalarEvolution missed an 2264 // opportunity to fold something. For now, just ignore such cases 2265 // rather than proceed with zero in a register. 2266 if (!Sum->isZero()) { 2267 F.BaseRegs.push_back(Sum); 2268 (void)InsertFormula(LU, LUIdx, F); 2269 } 2270 } 2271} 2272 2273/// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets. 2274void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, 2275 Formula Base) { 2276 // We can't add a symbolic offset if the address already contains one. 2277 if (Base.AM.BaseGV) return; 2278 2279 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { 2280 const SCEV *G = Base.BaseRegs[i]; 2281 GlobalValue *GV = ExtractSymbol(G, SE); 2282 if (G->isZero() || !GV) 2283 continue; 2284 Formula F = Base; 2285 F.AM.BaseGV = GV; 2286 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset, 2287 LU.Kind, LU.AccessTy, TLI)) 2288 continue; 2289 F.BaseRegs[i] = G; 2290 (void)InsertFormula(LU, LUIdx, F); 2291 } 2292} 2293 2294/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets. 2295void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, 2296 Formula Base) { 2297 // TODO: For now, just add the min and max offset, because it usually isn't 2298 // worthwhile looking at everything inbetween. 2299 SmallVector<int64_t, 4> Worklist; 2300 Worklist.push_back(LU.MinOffset); 2301 if (LU.MaxOffset != LU.MinOffset) 2302 Worklist.push_back(LU.MaxOffset); 2303 2304 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { 2305 const SCEV *G = Base.BaseRegs[i]; 2306 2307 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(), 2308 E = Worklist.end(); I != E; ++I) { 2309 Formula F = Base; 2310 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I; 2311 if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I, 2312 LU.Kind, LU.AccessTy, TLI)) { 2313 F.BaseRegs[i] = SE.getAddExpr(G, SE.getConstant(G->getType(), *I)); 2314 2315 (void)InsertFormula(LU, LUIdx, F); 2316 } 2317 } 2318 2319 int64_t Imm = ExtractImmediate(G, SE); 2320 if (G->isZero() || Imm == 0) 2321 continue; 2322 Formula F = Base; 2323 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm; 2324 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset, 2325 LU.Kind, LU.AccessTy, TLI)) 2326 continue; 2327 F.BaseRegs[i] = G; 2328 (void)InsertFormula(LU, LUIdx, F); 2329 } 2330} 2331 2332/// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up 2333/// the comparison. For example, x == y -> x*c == y*c. 2334void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, 2335 Formula Base) { 2336 if (LU.Kind != LSRUse::ICmpZero) return; 2337 2338 // Determine the integer type for the base formula. 2339 const Type *IntTy = Base.getType(); 2340 if (!IntTy) return; 2341 if (SE.getTypeSizeInBits(IntTy) > 64) return; 2342 2343 // Don't do this if there is more than one offset. 2344 if (LU.MinOffset != LU.MaxOffset) return; 2345 2346 assert(!Base.AM.BaseGV && "ICmpZero use is not legal!"); 2347 2348 // Check each interesting stride. 2349 for (SmallSetVector<int64_t, 8>::const_iterator 2350 I = Factors.begin(), E = Factors.end(); I != E; ++I) { 2351 int64_t Factor = *I; 2352 Formula F = Base; 2353 2354 // Check that the multiplication doesn't overflow. 2355 if (F.AM.BaseOffs == INT64_MIN && Factor == -1) 2356 continue; 2357 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs * Factor; 2358 if (F.AM.BaseOffs / Factor != Base.AM.BaseOffs) 2359 continue; 2360 2361 // Check that multiplying with the use offset doesn't overflow. 2362 int64_t Offset = LU.MinOffset; 2363 if (Offset == INT64_MIN && Factor == -1) 2364 continue; 2365 Offset = (uint64_t)Offset * Factor; 2366 if (Offset / Factor != LU.MinOffset) 2367 continue; 2368 2369 // Check that this scale is legal. 2370 if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI)) 2371 continue; 2372 2373 // Compensate for the use having MinOffset built into it. 2374 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset; 2375 2376 const SCEV *FactorS = SE.getConstant(IntTy, Factor); 2377 2378 // Check that multiplying with each base register doesn't overflow. 2379 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) { 2380 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS); 2381 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i]) 2382 goto next; 2383 } 2384 2385 // Check that multiplying with the scaled register doesn't overflow. 2386 if (F.ScaledReg) { 2387 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS); 2388 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg) 2389 continue; 2390 } 2391 2392 // If we make it here and it's legal, add it. 2393 (void)InsertFormula(LU, LUIdx, F); 2394 next:; 2395 } 2396} 2397 2398/// GenerateScales - Generate stride factor reuse formulae by making use of 2399/// scaled-offset address modes, for example. 2400void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, 2401 Formula Base) { 2402 // Determine the integer type for the base formula. 2403 const Type *IntTy = Base.getType(); 2404 if (!IntTy) return; 2405 2406 // If this Formula already has a scaled register, we can't add another one. 2407 if (Base.AM.Scale != 0) return; 2408 2409 // Check each interesting stride. 2410 for (SmallSetVector<int64_t, 8>::const_iterator 2411 I = Factors.begin(), E = Factors.end(); I != E; ++I) { 2412 int64_t Factor = *I; 2413 2414 Base.AM.Scale = Factor; 2415 Base.AM.HasBaseReg = Base.BaseRegs.size() > 1; 2416 // Check whether this scale is going to be legal. 2417 if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset, 2418 LU.Kind, LU.AccessTy, TLI)) { 2419 // As a special-case, handle special out-of-loop Basic users specially. 2420 // TODO: Reconsider this special case. 2421 if (LU.Kind == LSRUse::Basic && 2422 isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset, 2423 LSRUse::Special, LU.AccessTy, TLI) && 2424 LU.AllFixupsOutsideLoop) 2425 LU.Kind = LSRUse::Special; 2426 else 2427 continue; 2428 } 2429 // For an ICmpZero, negating a solitary base register won't lead to 2430 // new solutions. 2431 if (LU.Kind == LSRUse::ICmpZero && 2432 !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV) 2433 continue; 2434 // For each addrec base reg, apply the scale, if possible. 2435 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) 2436 if (const SCEVAddRecExpr *AR = 2437 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) { 2438 const SCEV *FactorS = SE.getConstant(IntTy, Factor); 2439 if (FactorS->isZero()) 2440 continue; 2441 // Divide out the factor, ignoring high bits, since we'll be 2442 // scaling the value back up in the end. 2443 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) { 2444 // TODO: This could be optimized to avoid all the copying. 2445 Formula F = Base; 2446 F.ScaledReg = Quotient; 2447 F.DeleteBaseReg(F.BaseRegs[i]); 2448 (void)InsertFormula(LU, LUIdx, F); 2449 } 2450 } 2451 } 2452} 2453 2454/// GenerateTruncates - Generate reuse formulae from different IV types. 2455void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, 2456 Formula Base) { 2457 // This requires TargetLowering to tell us which truncates are free. 2458 if (!TLI) return; 2459 2460 // Don't bother truncating symbolic values. 2461 if (Base.AM.BaseGV) return; 2462 2463 // Determine the integer type for the base formula. 2464 const Type *DstTy = Base.getType(); 2465 if (!DstTy) return; 2466 DstTy = SE.getEffectiveSCEVType(DstTy); 2467 2468 for (SmallSetVector<const Type *, 4>::const_iterator 2469 I = Types.begin(), E = Types.end(); I != E; ++I) { 2470 const Type *SrcTy = *I; 2471 if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) { 2472 Formula F = Base; 2473 2474 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I); 2475 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(), 2476 JE = F.BaseRegs.end(); J != JE; ++J) 2477 *J = SE.getAnyExtendExpr(*J, SrcTy); 2478 2479 // TODO: This assumes we've done basic processing on all uses and 2480 // have an idea what the register usage is. 2481 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses)) 2482 continue; 2483 2484 (void)InsertFormula(LU, LUIdx, F); 2485 } 2486 } 2487} 2488 2489namespace { 2490 2491/// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to 2492/// defer modifications so that the search phase doesn't have to worry about 2493/// the data structures moving underneath it. 2494struct WorkItem { 2495 size_t LUIdx; 2496 int64_t Imm; 2497 const SCEV *OrigReg; 2498 2499 WorkItem(size_t LI, int64_t I, const SCEV *R) 2500 : LUIdx(LI), Imm(I), OrigReg(R) {} 2501 2502 void print(raw_ostream &OS) const; 2503 void dump() const; 2504}; 2505 2506} 2507 2508void WorkItem::print(raw_ostream &OS) const { 2509 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx 2510 << " , add offset " << Imm; 2511} 2512 2513void WorkItem::dump() const { 2514 print(errs()); errs() << '\n'; 2515} 2516 2517/// GenerateCrossUseConstantOffsets - Look for registers which are a constant 2518/// distance apart and try to form reuse opportunities between them. 2519void LSRInstance::GenerateCrossUseConstantOffsets() { 2520 // Group the registers by their value without any added constant offset. 2521 typedef std::map<int64_t, const SCEV *> ImmMapTy; 2522 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy; 2523 RegMapTy Map; 2524 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap; 2525 SmallVector<const SCEV *, 8> Sequence; 2526 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end(); 2527 I != E; ++I) { 2528 const SCEV *Reg = *I; 2529 int64_t Imm = ExtractImmediate(Reg, SE); 2530 std::pair<RegMapTy::iterator, bool> Pair = 2531 Map.insert(std::make_pair(Reg, ImmMapTy())); 2532 if (Pair.second) 2533 Sequence.push_back(Reg); 2534 Pair.first->second.insert(std::make_pair(Imm, *I)); 2535 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I); 2536 } 2537 2538 // Now examine each set of registers with the same base value. Build up 2539 // a list of work to do and do the work in a separate step so that we're 2540 // not adding formulae and register counts while we're searching. 2541 SmallVector<WorkItem, 32> WorkItems; 2542 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems; 2543 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(), 2544 E = Sequence.end(); I != E; ++I) { 2545 const SCEV *Reg = *I; 2546 const ImmMapTy &Imms = Map.find(Reg)->second; 2547 2548 // It's not worthwhile looking for reuse if there's only one offset. 2549 if (Imms.size() == 1) 2550 continue; 2551 2552 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':'; 2553 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end(); 2554 J != JE; ++J) 2555 dbgs() << ' ' << J->first; 2556 dbgs() << '\n'); 2557 2558 // Examine each offset. 2559 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end(); 2560 J != JE; ++J) { 2561 const SCEV *OrigReg = J->second; 2562 2563 int64_t JImm = J->first; 2564 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg); 2565 2566 if (!isa<SCEVConstant>(OrigReg) && 2567 UsedByIndicesMap[Reg].count() == 1) { 2568 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n'); 2569 continue; 2570 } 2571 2572 // Conservatively examine offsets between this orig reg a few selected 2573 // other orig regs. 2574 ImmMapTy::const_iterator OtherImms[] = { 2575 Imms.begin(), prior(Imms.end()), 2576 Imms.upper_bound((Imms.begin()->first + prior(Imms.end())->first) / 2) 2577 }; 2578 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) { 2579 ImmMapTy::const_iterator M = OtherImms[i]; 2580 if (M == J || M == JE) continue; 2581 2582 // Compute the difference between the two. 2583 int64_t Imm = (uint64_t)JImm - M->first; 2584 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1; 2585 LUIdx = UsedByIndices.find_next(LUIdx)) 2586 // Make a memo of this use, offset, and register tuple. 2587 if (UniqueItems.insert(std::make_pair(LUIdx, Imm))) 2588 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg)); 2589 } 2590 } 2591 } 2592 2593 Map.clear(); 2594 Sequence.clear(); 2595 UsedByIndicesMap.clear(); 2596 UniqueItems.clear(); 2597 2598 // Now iterate through the worklist and add new formulae. 2599 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(), 2600 E = WorkItems.end(); I != E; ++I) { 2601 const WorkItem &WI = *I; 2602 size_t LUIdx = WI.LUIdx; 2603 LSRUse &LU = Uses[LUIdx]; 2604 int64_t Imm = WI.Imm; 2605 const SCEV *OrigReg = WI.OrigReg; 2606 2607 const Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType()); 2608 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm)); 2609 unsigned BitWidth = SE.getTypeSizeInBits(IntTy); 2610 2611 // TODO: Use a more targeted data structure. 2612 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) { 2613 Formula F = LU.Formulae[L]; 2614 // Use the immediate in the scaled register. 2615 if (F.ScaledReg == OrigReg) { 2616 int64_t Offs = (uint64_t)F.AM.BaseOffs + 2617 Imm * (uint64_t)F.AM.Scale; 2618 // Don't create 50 + reg(-50). 2619 if (F.referencesReg(SE.getSCEV( 2620 ConstantInt::get(IntTy, -(uint64_t)Offs)))) 2621 continue; 2622 Formula NewF = F; 2623 NewF.AM.BaseOffs = Offs; 2624 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset, 2625 LU.Kind, LU.AccessTy, TLI)) 2626 continue; 2627 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg); 2628 2629 // If the new scale is a constant in a register, and adding the constant 2630 // value to the immediate would produce a value closer to zero than the 2631 // immediate itself, then the formula isn't worthwhile. 2632 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg)) 2633 if (C->getValue()->getValue().isNegative() != 2634 (NewF.AM.BaseOffs < 0) && 2635 (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale)) 2636 .ule(abs64(NewF.AM.BaseOffs))) 2637 continue; 2638 2639 // OK, looks good. 2640 (void)InsertFormula(LU, LUIdx, NewF); 2641 } else { 2642 // Use the immediate in a base register. 2643 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) { 2644 const SCEV *BaseReg = F.BaseRegs[N]; 2645 if (BaseReg != OrigReg) 2646 continue; 2647 Formula NewF = F; 2648 NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm; 2649 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset, 2650 LU.Kind, LU.AccessTy, TLI)) 2651 continue; 2652 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg); 2653 2654 // If the new formula has a constant in a register, and adding the 2655 // constant value to the immediate would produce a value closer to 2656 // zero than the immediate itself, then the formula isn't worthwhile. 2657 for (SmallVectorImpl<const SCEV *>::const_iterator 2658 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end(); 2659 J != JE; ++J) 2660 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J)) 2661 if ((C->getValue()->getValue() + NewF.AM.BaseOffs).abs().slt( 2662 abs64(NewF.AM.BaseOffs)) && 2663 (C->getValue()->getValue() + 2664 NewF.AM.BaseOffs).countTrailingZeros() >= 2665 CountTrailingZeros_64(NewF.AM.BaseOffs)) 2666 goto skip_formula; 2667 2668 // Ok, looks good. 2669 (void)InsertFormula(LU, LUIdx, NewF); 2670 break; 2671 skip_formula:; 2672 } 2673 } 2674 } 2675 } 2676} 2677 2678/// GenerateAllReuseFormulae - Generate formulae for each use. 2679void 2680LSRInstance::GenerateAllReuseFormulae() { 2681 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan 2682 // queries are more precise. 2683 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2684 LSRUse &LU = Uses[LUIdx]; 2685 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2686 GenerateReassociations(LU, LUIdx, LU.Formulae[i]); 2687 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2688 GenerateCombinations(LU, LUIdx, LU.Formulae[i]); 2689 } 2690 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2691 LSRUse &LU = Uses[LUIdx]; 2692 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2693 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]); 2694 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2695 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]); 2696 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2697 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]); 2698 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2699 GenerateScales(LU, LUIdx, LU.Formulae[i]); 2700 } 2701 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2702 LSRUse &LU = Uses[LUIdx]; 2703 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) 2704 GenerateTruncates(LU, LUIdx, LU.Formulae[i]); 2705 } 2706 2707 GenerateCrossUseConstantOffsets(); 2708} 2709 2710/// If their are multiple formulae with the same set of registers used 2711/// by other uses, pick the best one and delete the others. 2712void LSRInstance::FilterOutUndesirableDedicatedRegisters() { 2713#ifndef NDEBUG 2714 bool Changed = false; 2715#endif 2716 2717 // Collect the best formula for each unique set of shared registers. This 2718 // is reset for each use. 2719 typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo> 2720 BestFormulaeTy; 2721 BestFormulaeTy BestFormulae; 2722 2723 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2724 LSRUse &LU = Uses[LUIdx]; 2725 FormulaSorter Sorter(L, LU, SE, DT); 2726 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << "\n"); 2727 2728 bool Any = false; 2729 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); 2730 FIdx != NumForms; ++FIdx) { 2731 Formula &F = LU.Formulae[FIdx]; 2732 2733 SmallVector<const SCEV *, 2> Key; 2734 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(), 2735 JE = F.BaseRegs.end(); J != JE; ++J) { 2736 const SCEV *Reg = *J; 2737 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx)) 2738 Key.push_back(Reg); 2739 } 2740 if (F.ScaledReg && 2741 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx)) 2742 Key.push_back(F.ScaledReg); 2743 // Unstable sort by host order ok, because this is only used for 2744 // uniquifying. 2745 std::sort(Key.begin(), Key.end()); 2746 2747 std::pair<BestFormulaeTy::const_iterator, bool> P = 2748 BestFormulae.insert(std::make_pair(Key, FIdx)); 2749 if (!P.second) { 2750 Formula &Best = LU.Formulae[P.first->second]; 2751 if (Sorter.operator()(F, Best)) 2752 std::swap(F, Best); 2753 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs()); 2754 dbgs() << "\n" 2755 " in favor of formula "; Best.print(dbgs()); 2756 dbgs() << '\n'); 2757#ifndef NDEBUG 2758 Changed = true; 2759#endif 2760 LU.DeleteFormula(F); 2761 --FIdx; 2762 --NumForms; 2763 Any = true; 2764 continue; 2765 } 2766 } 2767 2768 // Now that we've filtered out some formulae, recompute the Regs set. 2769 if (Any) 2770 LU.RecomputeRegs(LUIdx, RegUses); 2771 2772 // Reset this to prepare for the next use. 2773 BestFormulae.clear(); 2774 } 2775 2776 DEBUG(if (Changed) { 2777 dbgs() << "\n" 2778 "After filtering out undesirable candidates:\n"; 2779 print_uses(dbgs()); 2780 }); 2781} 2782 2783// This is a rough guess that seems to work fairly well. 2784static const size_t ComplexityLimit = UINT16_MAX; 2785 2786/// EstimateSearchSpaceComplexity - Estimate the worst-case number of 2787/// solutions the solver might have to consider. It almost never considers 2788/// this many solutions because it prune the search space, but the pruning 2789/// isn't always sufficient. 2790size_t LSRInstance::EstimateSearchSpaceComplexity() const { 2791 uint32_t Power = 1; 2792 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), 2793 E = Uses.end(); I != E; ++I) { 2794 size_t FSize = I->Formulae.size(); 2795 if (FSize >= ComplexityLimit) { 2796 Power = ComplexityLimit; 2797 break; 2798 } 2799 Power *= FSize; 2800 if (Power >= ComplexityLimit) 2801 break; 2802 } 2803 return Power; 2804} 2805 2806/// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of 2807/// formulae to choose from, use some rough heuristics to prune down the number 2808/// of formulae. This keeps the main solver from taking an extraordinary amount 2809/// of time in some worst-case scenarios. 2810void LSRInstance::NarrowSearchSpaceUsingHeuristics() { 2811 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 2812 DEBUG(dbgs() << "The search space is too complex.\n"); 2813 2814 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae " 2815 "which use a superset of registers used by other " 2816 "formulae.\n"); 2817 2818 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2819 LSRUse &LU = Uses[LUIdx]; 2820 bool Any = false; 2821 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { 2822 Formula &F = LU.Formulae[i]; 2823 for (SmallVectorImpl<const SCEV *>::const_iterator 2824 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) { 2825 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) { 2826 Formula NewF = F; 2827 NewF.AM.BaseOffs += C->getValue()->getSExtValue(); 2828 NewF.BaseRegs.erase(NewF.BaseRegs.begin() + 2829 (I - F.BaseRegs.begin())); 2830 if (LU.HasFormulaWithSameRegs(NewF)) { 2831 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); 2832 LU.DeleteFormula(F); 2833 --i; 2834 --e; 2835 Any = true; 2836 break; 2837 } 2838 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) { 2839 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) 2840 if (!F.AM.BaseGV) { 2841 Formula NewF = F; 2842 NewF.AM.BaseGV = GV; 2843 NewF.BaseRegs.erase(NewF.BaseRegs.begin() + 2844 (I - F.BaseRegs.begin())); 2845 if (LU.HasFormulaWithSameRegs(NewF)) { 2846 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); 2847 dbgs() << '\n'); 2848 LU.DeleteFormula(F); 2849 --i; 2850 --e; 2851 Any = true; 2852 break; 2853 } 2854 } 2855 } 2856 } 2857 } 2858 if (Any) 2859 LU.RecomputeRegs(LUIdx, RegUses); 2860 } 2861 2862 DEBUG(dbgs() << "After pre-selection:\n"; 2863 print_uses(dbgs())); 2864 } 2865 2866 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 2867 DEBUG(dbgs() << "The search space is too complex.\n"); 2868 2869 DEBUG(dbgs() << "Narrowing the search space by assuming that uses " 2870 "separated by a constant offset will use the same " 2871 "registers.\n"); 2872 2873 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2874 LSRUse &LU = Uses[LUIdx]; 2875 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); 2876 FIdx != NumForms; ++FIdx) { 2877 Formula &F = LU.Formulae[FIdx]; 2878 if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) { 2879 if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) { 2880 if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs, 2881 /*HasBaseReg=*/false, 2882 LU.Kind, LU.AccessTy)) { 2883 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); 2884 dbgs() << '\n'); 2885 2886 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop; 2887 2888 // Delete formulae from the new use which are no longer legal. 2889 bool Any = false; 2890 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) { 2891 Formula &F = LUThatHas->Formulae[i]; 2892 if (!isLegalUse(F.AM, 2893 LUThatHas->MinOffset, LUThatHas->MaxOffset, 2894 LUThatHas->Kind, LUThatHas->AccessTy, TLI)) { 2895 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); 2896 dbgs() << '\n'); 2897 LUThatHas->DeleteFormula(F); 2898 --i; 2899 --e; 2900 Any = true; 2901 } 2902 } 2903 if (Any) 2904 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses); 2905 2906 // Update the relocs to reference the new use. 2907 for (size_t i = 0, e = Fixups.size(); i != e; ++i) { 2908 if (Fixups[i].LUIdx == LUIdx) { 2909 Fixups[i].LUIdx = LUThatHas - &Uses.front(); 2910 Fixups[i].Offset += F.AM.BaseOffs; 2911 DEBUG(errs() << "New fixup has offset " 2912 << Fixups[i].Offset << "\n"); 2913 } 2914 if (Fixups[i].LUIdx == NumUses-1) 2915 Fixups[i].LUIdx = LUIdx; 2916 } 2917 2918 // Delete the old use. 2919 DeleteUse(LU); 2920 --LUIdx; 2921 --NumUses; 2922 break; 2923 } 2924 } 2925 } 2926 } 2927 } 2928 2929 DEBUG(dbgs() << "After pre-selection:\n"; 2930 print_uses(dbgs())); 2931 } 2932 2933 SmallPtrSet<const SCEV *, 4> Taken; 2934 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) { 2935 // Ok, we have too many of formulae on our hands to conveniently handle. 2936 // Use a rough heuristic to thin out the list. 2937 DEBUG(dbgs() << "The search space is too complex.\n"); 2938 2939 // Pick the register which is used by the most LSRUses, which is likely 2940 // to be a good reuse register candidate. 2941 const SCEV *Best = 0; 2942 unsigned BestNum = 0; 2943 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end(); 2944 I != E; ++I) { 2945 const SCEV *Reg = *I; 2946 if (Taken.count(Reg)) 2947 continue; 2948 if (!Best) 2949 Best = Reg; 2950 else { 2951 unsigned Count = RegUses.getUsedByIndices(Reg).count(); 2952 if (Count > BestNum) { 2953 Best = Reg; 2954 BestNum = Count; 2955 } 2956 } 2957 } 2958 2959 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best 2960 << " will yield profitable reuse.\n"); 2961 Taken.insert(Best); 2962 2963 // In any use with formulae which references this register, delete formulae 2964 // which don't reference it. 2965 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { 2966 LSRUse &LU = Uses[LUIdx]; 2967 if (!LU.Regs.count(Best)) continue; 2968 2969 bool Any = false; 2970 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { 2971 Formula &F = LU.Formulae[i]; 2972 if (!F.referencesReg(Best)) { 2973 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); 2974 LU.DeleteFormula(F); 2975 --e; 2976 --i; 2977 Any = true; 2978 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?"); 2979 continue; 2980 } 2981 } 2982 2983 if (Any) 2984 LU.RecomputeRegs(LUIdx, RegUses); 2985 } 2986 2987 DEBUG(dbgs() << "After pre-selection:\n"; 2988 print_uses(dbgs())); 2989 } 2990} 2991 2992/// SolveRecurse - This is the recursive solver. 2993void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution, 2994 Cost &SolutionCost, 2995 SmallVectorImpl<const Formula *> &Workspace, 2996 const Cost &CurCost, 2997 const SmallPtrSet<const SCEV *, 16> &CurRegs, 2998 DenseSet<const SCEV *> &VisitedRegs) const { 2999 // Some ideas: 3000 // - prune more: 3001 // - use more aggressive filtering 3002 // - sort the formula so that the most profitable solutions are found first 3003 // - sort the uses too 3004 // - search faster: 3005 // - don't compute a cost, and then compare. compare while computing a cost 3006 // and bail early. 3007 // - track register sets with SmallBitVector 3008 3009 const LSRUse &LU = Uses[Workspace.size()]; 3010 3011 // If this use references any register that's already a part of the 3012 // in-progress solution, consider it a requirement that a formula must 3013 // reference that register in order to be considered. This prunes out 3014 // unprofitable searching. 3015 SmallSetVector<const SCEV *, 4> ReqRegs; 3016 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(), 3017 E = CurRegs.end(); I != E; ++I) 3018 if (LU.Regs.count(*I)) 3019 ReqRegs.insert(*I); 3020 3021 bool AnySatisfiedReqRegs = false; 3022 SmallPtrSet<const SCEV *, 16> NewRegs; 3023 Cost NewCost; 3024retry: 3025 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), 3026 E = LU.Formulae.end(); I != E; ++I) { 3027 const Formula &F = *I; 3028 3029 // Ignore formulae which do not use any of the required registers. 3030 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(), 3031 JE = ReqRegs.end(); J != JE; ++J) { 3032 const SCEV *Reg = *J; 3033 if ((!F.ScaledReg || F.ScaledReg != Reg) && 3034 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) == 3035 F.BaseRegs.end()) 3036 goto skip; 3037 } 3038 AnySatisfiedReqRegs = true; 3039 3040 // Evaluate the cost of the current formula. If it's already worse than 3041 // the current best, prune the search at that point. 3042 NewCost = CurCost; 3043 NewRegs = CurRegs; 3044 NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT); 3045 if (NewCost < SolutionCost) { 3046 Workspace.push_back(&F); 3047 if (Workspace.size() != Uses.size()) { 3048 SolveRecurse(Solution, SolutionCost, Workspace, NewCost, 3049 NewRegs, VisitedRegs); 3050 if (F.getNumRegs() == 1 && Workspace.size() == 1) 3051 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]); 3052 } else { 3053 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs()); 3054 dbgs() << ". Regs:"; 3055 for (SmallPtrSet<const SCEV *, 16>::const_iterator 3056 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I) 3057 dbgs() << ' ' << **I; 3058 dbgs() << '\n'); 3059 3060 SolutionCost = NewCost; 3061 Solution = Workspace; 3062 } 3063 Workspace.pop_back(); 3064 } 3065 skip:; 3066 } 3067 3068 // If none of the formulae had all of the required registers, relax the 3069 // constraint so that we don't exclude all formulae. 3070 if (!AnySatisfiedReqRegs) { 3071 assert(!ReqRegs.empty() && "Solver failed even without required registers"); 3072 ReqRegs.clear(); 3073 goto retry; 3074 } 3075} 3076 3077void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const { 3078 SmallVector<const Formula *, 8> Workspace; 3079 Cost SolutionCost; 3080 SolutionCost.Loose(); 3081 Cost CurCost; 3082 SmallPtrSet<const SCEV *, 16> CurRegs; 3083 DenseSet<const SCEV *> VisitedRegs; 3084 Workspace.reserve(Uses.size()); 3085 3086 SolveRecurse(Solution, SolutionCost, Workspace, CurCost, 3087 CurRegs, VisitedRegs); 3088 3089 // Ok, we've now made all our decisions. 3090 DEBUG(dbgs() << "\n" 3091 "The chosen solution requires "; SolutionCost.print(dbgs()); 3092 dbgs() << ":\n"; 3093 for (size_t i = 0, e = Uses.size(); i != e; ++i) { 3094 dbgs() << " "; 3095 Uses[i].print(dbgs()); 3096 dbgs() << "\n" 3097 " "; 3098 Solution[i]->print(dbgs()); 3099 dbgs() << '\n'; 3100 }); 3101} 3102 3103/// getImmediateDominator - A handy utility for the specific DominatorTree 3104/// query that we need here. 3105/// 3106static BasicBlock *getImmediateDominator(BasicBlock *BB, DominatorTree &DT) { 3107 DomTreeNode *Node = DT.getNode(BB); 3108 if (!Node) return 0; 3109 Node = Node->getIDom(); 3110 if (!Node) return 0; 3111 return Node->getBlock(); 3112} 3113 3114/// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up 3115/// the dominator tree far as we can go while still being dominated by the 3116/// input positions. This helps canonicalize the insert position, which 3117/// encourages sharing. 3118BasicBlock::iterator 3119LSRInstance::HoistInsertPosition(BasicBlock::iterator IP, 3120 const SmallVectorImpl<Instruction *> &Inputs) 3121 const { 3122 for (;;) { 3123 const Loop *IPLoop = LI.getLoopFor(IP->getParent()); 3124 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0; 3125 3126 BasicBlock *IDom; 3127 for (BasicBlock *Rung = IP->getParent(); ; Rung = IDom) { 3128 IDom = getImmediateDominator(Rung, DT); 3129 if (!IDom) return IP; 3130 3131 // Don't climb into a loop though. 3132 const Loop *IDomLoop = LI.getLoopFor(IDom); 3133 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0; 3134 if (IDomDepth <= IPLoopDepth && 3135 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop)) 3136 break; 3137 } 3138 3139 bool AllDominate = true; 3140 Instruction *BetterPos = 0; 3141 Instruction *Tentative = IDom->getTerminator(); 3142 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(), 3143 E = Inputs.end(); I != E; ++I) { 3144 Instruction *Inst = *I; 3145 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) { 3146 AllDominate = false; 3147 break; 3148 } 3149 // Attempt to find an insert position in the middle of the block, 3150 // instead of at the end, so that it can be used for other expansions. 3151 if (IDom == Inst->getParent() && 3152 (!BetterPos || DT.dominates(BetterPos, Inst))) 3153 BetterPos = llvm::next(BasicBlock::iterator(Inst)); 3154 } 3155 if (!AllDominate) 3156 break; 3157 if (BetterPos) 3158 IP = BetterPos; 3159 else 3160 IP = Tentative; 3161 } 3162 3163 return IP; 3164} 3165 3166/// AdjustInsertPositionForExpand - Determine an input position which will be 3167/// dominated by the operands and which will dominate the result. 3168BasicBlock::iterator 3169LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator IP, 3170 const LSRFixup &LF, 3171 const LSRUse &LU) const { 3172 // Collect some instructions which must be dominated by the 3173 // expanding replacement. These must be dominated by any operands that 3174 // will be required in the expansion. 3175 SmallVector<Instruction *, 4> Inputs; 3176 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace)) 3177 Inputs.push_back(I); 3178 if (LU.Kind == LSRUse::ICmpZero) 3179 if (Instruction *I = 3180 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1))) 3181 Inputs.push_back(I); 3182 if (LF.PostIncLoops.count(L)) { 3183 if (LF.isUseFullyOutsideLoop(L)) 3184 Inputs.push_back(L->getLoopLatch()->getTerminator()); 3185 else 3186 Inputs.push_back(IVIncInsertPos); 3187 } 3188 // The expansion must also be dominated by the increment positions of any 3189 // loops it for which it is using post-inc mode. 3190 for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(), 3191 E = LF.PostIncLoops.end(); I != E; ++I) { 3192 const Loop *PIL = *I; 3193 if (PIL == L) continue; 3194 3195 // Be dominated by the loop exit. 3196 SmallVector<BasicBlock *, 4> ExitingBlocks; 3197 PIL->getExitingBlocks(ExitingBlocks); 3198 if (!ExitingBlocks.empty()) { 3199 BasicBlock *BB = ExitingBlocks[0]; 3200 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i) 3201 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]); 3202 Inputs.push_back(BB->getTerminator()); 3203 } 3204 } 3205 3206 // Then, climb up the immediate dominator tree as far as we can go while 3207 // still being dominated by the input positions. 3208 IP = HoistInsertPosition(IP, Inputs); 3209 3210 // Don't insert instructions before PHI nodes. 3211 while (isa<PHINode>(IP)) ++IP; 3212 3213 // Ignore debug intrinsics. 3214 while (isa<DbgInfoIntrinsic>(IP)) ++IP; 3215 3216 return IP; 3217} 3218 3219Value *LSRInstance::Expand(const LSRFixup &LF, 3220 const Formula &F, 3221 BasicBlock::iterator IP, 3222 SCEVExpander &Rewriter, 3223 SmallVectorImpl<WeakVH> &DeadInsts) const { 3224 const LSRUse &LU = Uses[LF.LUIdx]; 3225 3226 // Determine an input position which will be dominated by the operands and 3227 // which will dominate the result. 3228 IP = AdjustInsertPositionForExpand(IP, LF, LU); 3229 3230 // Inform the Rewriter if we have a post-increment use, so that it can 3231 // perform an advantageous expansion. 3232 Rewriter.setPostInc(LF.PostIncLoops); 3233 3234 // This is the type that the user actually needs. 3235 const Type *OpTy = LF.OperandValToReplace->getType(); 3236 // This will be the type that we'll initially expand to. 3237 const Type *Ty = F.getType(); 3238 if (!Ty) 3239 // No type known; just expand directly to the ultimate type. 3240 Ty = OpTy; 3241 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy)) 3242 // Expand directly to the ultimate type if it's the right size. 3243 Ty = OpTy; 3244 // This is the type to do integer arithmetic in. 3245 const Type *IntTy = SE.getEffectiveSCEVType(Ty); 3246 3247 // Build up a list of operands to add together to form the full base. 3248 SmallVector<const SCEV *, 8> Ops; 3249 3250 // Expand the BaseRegs portion. 3251 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), 3252 E = F.BaseRegs.end(); I != E; ++I) { 3253 const SCEV *Reg = *I; 3254 assert(!Reg->isZero() && "Zero allocated in a base register!"); 3255 3256 // If we're expanding for a post-inc user, make the post-inc adjustment. 3257 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); 3258 Reg = TransformForPostIncUse(Denormalize, Reg, 3259 LF.UserInst, LF.OperandValToReplace, 3260 Loops, SE, DT); 3261 3262 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP))); 3263 } 3264 3265 // Flush the operand list to suppress SCEVExpander hoisting. 3266 if (!Ops.empty()) { 3267 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); 3268 Ops.clear(); 3269 Ops.push_back(SE.getUnknown(FullV)); 3270 } 3271 3272 // Expand the ScaledReg portion. 3273 Value *ICmpScaledV = 0; 3274 if (F.AM.Scale != 0) { 3275 const SCEV *ScaledS = F.ScaledReg; 3276 3277 // If we're expanding for a post-inc user, make the post-inc adjustment. 3278 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); 3279 ScaledS = TransformForPostIncUse(Denormalize, ScaledS, 3280 LF.UserInst, LF.OperandValToReplace, 3281 Loops, SE, DT); 3282 3283 if (LU.Kind == LSRUse::ICmpZero) { 3284 // An interesting way of "folding" with an icmp is to use a negated 3285 // scale, which we'll implement by inserting it into the other operand 3286 // of the icmp. 3287 assert(F.AM.Scale == -1 && 3288 "The only scale supported by ICmpZero uses is -1!"); 3289 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP); 3290 } else { 3291 // Otherwise just expand the scaled register and an explicit scale, 3292 // which is expected to be matched as part of the address. 3293 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP)); 3294 ScaledS = SE.getMulExpr(ScaledS, 3295 SE.getConstant(ScaledS->getType(), F.AM.Scale)); 3296 Ops.push_back(ScaledS); 3297 3298 // Flush the operand list to suppress SCEVExpander hoisting. 3299 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); 3300 Ops.clear(); 3301 Ops.push_back(SE.getUnknown(FullV)); 3302 } 3303 } 3304 3305 // Expand the GV portion. 3306 if (F.AM.BaseGV) { 3307 Ops.push_back(SE.getUnknown(F.AM.BaseGV)); 3308 3309 // Flush the operand list to suppress SCEVExpander hoisting. 3310 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); 3311 Ops.clear(); 3312 Ops.push_back(SE.getUnknown(FullV)); 3313 } 3314 3315 // Expand the immediate portion. 3316 int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset; 3317 if (Offset != 0) { 3318 if (LU.Kind == LSRUse::ICmpZero) { 3319 // The other interesting way of "folding" with an ICmpZero is to use a 3320 // negated immediate. 3321 if (!ICmpScaledV) 3322 ICmpScaledV = ConstantInt::get(IntTy, -Offset); 3323 else { 3324 Ops.push_back(SE.getUnknown(ICmpScaledV)); 3325 ICmpScaledV = ConstantInt::get(IntTy, Offset); 3326 } 3327 } else { 3328 // Just add the immediate values. These again are expected to be matched 3329 // as part of the address. 3330 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset))); 3331 } 3332 } 3333 3334 // Emit instructions summing all the operands. 3335 const SCEV *FullS = Ops.empty() ? 3336 SE.getConstant(IntTy, 0) : 3337 SE.getAddExpr(Ops); 3338 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP); 3339 3340 // We're done expanding now, so reset the rewriter. 3341 Rewriter.clearPostInc(); 3342 3343 // An ICmpZero Formula represents an ICmp which we're handling as a 3344 // comparison against zero. Now that we've expanded an expression for that 3345 // form, update the ICmp's other operand. 3346 if (LU.Kind == LSRUse::ICmpZero) { 3347 ICmpInst *CI = cast<ICmpInst>(LF.UserInst); 3348 DeadInsts.push_back(CI->getOperand(1)); 3349 assert(!F.AM.BaseGV && "ICmp does not support folding a global value and " 3350 "a scale at the same time!"); 3351 if (F.AM.Scale == -1) { 3352 if (ICmpScaledV->getType() != OpTy) { 3353 Instruction *Cast = 3354 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false, 3355 OpTy, false), 3356 ICmpScaledV, OpTy, "tmp", CI); 3357 ICmpScaledV = Cast; 3358 } 3359 CI->setOperand(1, ICmpScaledV); 3360 } else { 3361 assert(F.AM.Scale == 0 && 3362 "ICmp does not support folding a global value and " 3363 "a scale at the same time!"); 3364 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy), 3365 -(uint64_t)Offset); 3366 if (C->getType() != OpTy) 3367 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 3368 OpTy, false), 3369 C, OpTy); 3370 3371 CI->setOperand(1, C); 3372 } 3373 } 3374 3375 return FullV; 3376} 3377 3378/// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use 3379/// of their operands effectively happens in their predecessor blocks, so the 3380/// expression may need to be expanded in multiple places. 3381void LSRInstance::RewriteForPHI(PHINode *PN, 3382 const LSRFixup &LF, 3383 const Formula &F, 3384 SCEVExpander &Rewriter, 3385 SmallVectorImpl<WeakVH> &DeadInsts, 3386 Pass *P) const { 3387 DenseMap<BasicBlock *, Value *> Inserted; 3388 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 3389 if (PN->getIncomingValue(i) == LF.OperandValToReplace) { 3390 BasicBlock *BB = PN->getIncomingBlock(i); 3391 3392 // If this is a critical edge, split the edge so that we do not insert 3393 // the code on all predecessor/successor paths. We do this unless this 3394 // is the canonical backedge for this loop, which complicates post-inc 3395 // users. 3396 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 && 3397 !isa<IndirectBrInst>(BB->getTerminator()) && 3398 (PN->getParent() != L->getHeader() || !L->contains(BB))) { 3399 // Split the critical edge. 3400 BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P); 3401 3402 // If PN is outside of the loop and BB is in the loop, we want to 3403 // move the block to be immediately before the PHI block, not 3404 // immediately after BB. 3405 if (L->contains(BB) && !L->contains(PN)) 3406 NewBB->moveBefore(PN->getParent()); 3407 3408 // Splitting the edge can reduce the number of PHI entries we have. 3409 e = PN->getNumIncomingValues(); 3410 BB = NewBB; 3411 i = PN->getBasicBlockIndex(BB); 3412 } 3413 3414 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair = 3415 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0))); 3416 if (!Pair.second) 3417 PN->setIncomingValue(i, Pair.first->second); 3418 else { 3419 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts); 3420 3421 // If this is reuse-by-noop-cast, insert the noop cast. 3422 const Type *OpTy = LF.OperandValToReplace->getType(); 3423 if (FullV->getType() != OpTy) 3424 FullV = 3425 CastInst::Create(CastInst::getCastOpcode(FullV, false, 3426 OpTy, false), 3427 FullV, LF.OperandValToReplace->getType(), 3428 "tmp", BB->getTerminator()); 3429 3430 PN->setIncomingValue(i, FullV); 3431 Pair.first->second = FullV; 3432 } 3433 } 3434} 3435 3436/// Rewrite - Emit instructions for the leading candidate expression for this 3437/// LSRUse (this is called "expanding"), and update the UserInst to reference 3438/// the newly expanded value. 3439void LSRInstance::Rewrite(const LSRFixup &LF, 3440 const Formula &F, 3441 SCEVExpander &Rewriter, 3442 SmallVectorImpl<WeakVH> &DeadInsts, 3443 Pass *P) const { 3444 // First, find an insertion point that dominates UserInst. For PHI nodes, 3445 // find the nearest block which dominates all the relevant uses. 3446 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) { 3447 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P); 3448 } else { 3449 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts); 3450 3451 // If this is reuse-by-noop-cast, insert the noop cast. 3452 const Type *OpTy = LF.OperandValToReplace->getType(); 3453 if (FullV->getType() != OpTy) { 3454 Instruction *Cast = 3455 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false), 3456 FullV, OpTy, "tmp", LF.UserInst); 3457 FullV = Cast; 3458 } 3459 3460 // Update the user. ICmpZero is handled specially here (for now) because 3461 // Expand may have updated one of the operands of the icmp already, and 3462 // its new value may happen to be equal to LF.OperandValToReplace, in 3463 // which case doing replaceUsesOfWith leads to replacing both operands 3464 // with the same value. TODO: Reorganize this. 3465 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero) 3466 LF.UserInst->setOperand(0, FullV); 3467 else 3468 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV); 3469 } 3470 3471 DeadInsts.push_back(LF.OperandValToReplace); 3472} 3473 3474void 3475LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution, 3476 Pass *P) { 3477 // Keep track of instructions we may have made dead, so that 3478 // we can remove them after we are done working. 3479 SmallVector<WeakVH, 16> DeadInsts; 3480 3481 SCEVExpander Rewriter(SE); 3482 Rewriter.disableCanonicalMode(); 3483 Rewriter.setIVIncInsertPos(L, IVIncInsertPos); 3484 3485 // Expand the new value definitions and update the users. 3486 for (size_t i = 0, e = Fixups.size(); i != e; ++i) { 3487 size_t LUIdx = Fixups[i].LUIdx; 3488 3489 Rewrite(Fixups[i], *Solution[LUIdx], Rewriter, DeadInsts, P); 3490 3491 Changed = true; 3492 } 3493 3494 // Clean up after ourselves. This must be done before deleting any 3495 // instructions. 3496 Rewriter.clear(); 3497 3498 Changed |= DeleteTriviallyDeadInstructions(DeadInsts); 3499} 3500 3501LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P) 3502 : IU(P->getAnalysis<IVUsers>()), 3503 SE(P->getAnalysis<ScalarEvolution>()), 3504 DT(P->getAnalysis<DominatorTree>()), 3505 LI(P->getAnalysis<LoopInfo>()), 3506 TLI(tli), L(l), Changed(false), IVIncInsertPos(0) { 3507 3508 // If LoopSimplify form is not available, stay out of trouble. 3509 if (!L->isLoopSimplifyForm()) return; 3510 3511 // If there's no interesting work to be done, bail early. 3512 if (IU.empty()) return; 3513 3514 DEBUG(dbgs() << "\nLSR on loop "; 3515 WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false); 3516 dbgs() << ":\n"); 3517 3518 /// OptimizeShadowIV - If IV is used in a int-to-float cast 3519 /// inside the loop then try to eliminate the cast operation. 3520 OptimizeShadowIV(); 3521 3522 // Change loop terminating condition to use the postinc iv when possible. 3523 Changed |= OptimizeLoopTermCond(); 3524 3525 CollectInterestingTypesAndFactors(); 3526 CollectFixupsAndInitialFormulae(); 3527 CollectLoopInvariantFixupsAndFormulae(); 3528 3529 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n"; 3530 print_uses(dbgs())); 3531 3532 // Now use the reuse data to generate a bunch of interesting ways 3533 // to formulate the values needed for the uses. 3534 GenerateAllReuseFormulae(); 3535 3536 DEBUG(dbgs() << "\n" 3537 "After generating reuse formulae:\n"; 3538 print_uses(dbgs())); 3539 3540 FilterOutUndesirableDedicatedRegisters(); 3541 NarrowSearchSpaceUsingHeuristics(); 3542 3543 SmallVector<const Formula *, 8> Solution; 3544 Solve(Solution); 3545 assert(Solution.size() == Uses.size() && "Malformed solution!"); 3546 3547 // Release memory that is no longer needed. 3548 Factors.clear(); 3549 Types.clear(); 3550 RegUses.clear(); 3551 3552#ifndef NDEBUG 3553 // Formulae should be legal. 3554 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), 3555 E = Uses.end(); I != E; ++I) { 3556 const LSRUse &LU = *I; 3557 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(), 3558 JE = LU.Formulae.end(); J != JE; ++J) 3559 assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset, 3560 LU.Kind, LU.AccessTy, TLI) && 3561 "Illegal formula generated!"); 3562 }; 3563#endif 3564 3565 // Now that we've decided what we want, make it so. 3566 ImplementSolution(Solution, P); 3567} 3568 3569void LSRInstance::print_factors_and_types(raw_ostream &OS) const { 3570 if (Factors.empty() && Types.empty()) return; 3571 3572 OS << "LSR has identified the following interesting factors and types: "; 3573 bool First = true; 3574 3575 for (SmallSetVector<int64_t, 8>::const_iterator 3576 I = Factors.begin(), E = Factors.end(); I != E; ++I) { 3577 if (!First) OS << ", "; 3578 First = false; 3579 OS << '*' << *I; 3580 } 3581 3582 for (SmallSetVector<const Type *, 4>::const_iterator 3583 I = Types.begin(), E = Types.end(); I != E; ++I) { 3584 if (!First) OS << ", "; 3585 First = false; 3586 OS << '(' << **I << ')'; 3587 } 3588 OS << '\n'; 3589} 3590 3591void LSRInstance::print_fixups(raw_ostream &OS) const { 3592 OS << "LSR is examining the following fixup sites:\n"; 3593 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(), 3594 E = Fixups.end(); I != E; ++I) { 3595 const LSRFixup &LF = *I; 3596 dbgs() << " "; 3597 LF.print(OS); 3598 OS << '\n'; 3599 } 3600} 3601 3602void LSRInstance::print_uses(raw_ostream &OS) const { 3603 OS << "LSR is examining the following uses:\n"; 3604 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), 3605 E = Uses.end(); I != E; ++I) { 3606 const LSRUse &LU = *I; 3607 dbgs() << " "; 3608 LU.print(OS); 3609 OS << '\n'; 3610 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(), 3611 JE = LU.Formulae.end(); J != JE; ++J) { 3612 OS << " "; 3613 J->print(OS); 3614 OS << '\n'; 3615 } 3616 } 3617} 3618 3619void LSRInstance::print(raw_ostream &OS) const { 3620 print_factors_and_types(OS); 3621 print_fixups(OS); 3622 print_uses(OS); 3623} 3624 3625void LSRInstance::dump() const { 3626 print(errs()); errs() << '\n'; 3627} 3628 3629namespace { 3630 3631class LoopStrengthReduce : public LoopPass { 3632 /// TLI - Keep a pointer of a TargetLowering to consult for determining 3633 /// transformation profitability. 3634 const TargetLowering *const TLI; 3635 3636public: 3637 static char ID; // Pass ID, replacement for typeid 3638 explicit LoopStrengthReduce(const TargetLowering *tli = 0); 3639 3640private: 3641 bool runOnLoop(Loop *L, LPPassManager &LPM); 3642 void getAnalysisUsage(AnalysisUsage &AU) const; 3643}; 3644 3645} 3646 3647char LoopStrengthReduce::ID = 0; 3648static RegisterPass<LoopStrengthReduce> 3649X("loop-reduce", "Loop Strength Reduction"); 3650 3651Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) { 3652 return new LoopStrengthReduce(TLI); 3653} 3654 3655LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli) 3656 : LoopPass(&ID), TLI(tli) {} 3657 3658void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const { 3659 // We split critical edges, so we change the CFG. However, we do update 3660 // many analyses if they are around. 3661 AU.addPreservedID(LoopSimplifyID); 3662 AU.addPreserved("domfrontier"); 3663 3664 AU.addRequired<LoopInfo>(); 3665 AU.addPreserved<LoopInfo>(); 3666 AU.addRequiredID(LoopSimplifyID); 3667 AU.addRequired<DominatorTree>(); 3668 AU.addPreserved<DominatorTree>(); 3669 AU.addRequired<ScalarEvolution>(); 3670 AU.addPreserved<ScalarEvolution>(); 3671 AU.addRequired<IVUsers>(); 3672 AU.addPreserved<IVUsers>(); 3673} 3674 3675bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) { 3676 bool Changed = false; 3677 3678 // Run the main LSR transformation. 3679 Changed |= LSRInstance(TLI, L, this).getChanged(); 3680 3681 // At this point, it is worth checking to see if any recurrence PHIs are also 3682 // dead, so that we can remove them as well. 3683 Changed |= DeleteDeadPHIs(L->getHeader()); 3684 3685 return Changed; 3686} 3687