ScalarEvolutionExpander.cpp revision 202878
1//===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file contains the implementation of the scalar evolution expander, 11// which is used to generate the code corresponding to a given scalar evolution 12// expression. 13// 14//===----------------------------------------------------------------------===// 15 16#include "llvm/Analysis/ScalarEvolutionExpander.h" 17#include "llvm/Analysis/LoopInfo.h" 18#include "llvm/LLVMContext.h" 19#include "llvm/Target/TargetData.h" 20#include "llvm/ADT/STLExtras.h" 21using namespace llvm; 22 23/// InsertNoopCastOfTo - Insert a cast of V to the specified type, 24/// which must be possible with a noop cast, doing what we can to share 25/// the casts. 26Value *SCEVExpander::InsertNoopCastOfTo(Value *V, const Type *Ty) { 27 Instruction::CastOps Op = CastInst::getCastOpcode(V, false, Ty, false); 28 assert((Op == Instruction::BitCast || 29 Op == Instruction::PtrToInt || 30 Op == Instruction::IntToPtr) && 31 "InsertNoopCastOfTo cannot perform non-noop casts!"); 32 assert(SE.getTypeSizeInBits(V->getType()) == SE.getTypeSizeInBits(Ty) && 33 "InsertNoopCastOfTo cannot change sizes!"); 34 35 // Short-circuit unnecessary bitcasts. 36 if (Op == Instruction::BitCast && V->getType() == Ty) 37 return V; 38 39 // Short-circuit unnecessary inttoptr<->ptrtoint casts. 40 if ((Op == Instruction::PtrToInt || Op == Instruction::IntToPtr) && 41 SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) { 42 if (CastInst *CI = dyn_cast<CastInst>(V)) 43 if ((CI->getOpcode() == Instruction::PtrToInt || 44 CI->getOpcode() == Instruction::IntToPtr) && 45 SE.getTypeSizeInBits(CI->getType()) == 46 SE.getTypeSizeInBits(CI->getOperand(0)->getType())) 47 return CI->getOperand(0); 48 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 49 if ((CE->getOpcode() == Instruction::PtrToInt || 50 CE->getOpcode() == Instruction::IntToPtr) && 51 SE.getTypeSizeInBits(CE->getType()) == 52 SE.getTypeSizeInBits(CE->getOperand(0)->getType())) 53 return CE->getOperand(0); 54 } 55 56 if (Constant *C = dyn_cast<Constant>(V)) 57 return ConstantExpr::getCast(Op, C, Ty); 58 59 if (Argument *A = dyn_cast<Argument>(V)) { 60 // Check to see if there is already a cast! 61 for (Value::use_iterator UI = A->use_begin(), E = A->use_end(); 62 UI != E; ++UI) 63 if ((*UI)->getType() == Ty) 64 if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) 65 if (CI->getOpcode() == Op) { 66 // If the cast isn't the first instruction of the function, move it. 67 if (BasicBlock::iterator(CI) != 68 A->getParent()->getEntryBlock().begin()) { 69 // Recreate the cast at the beginning of the entry block. 70 // The old cast is left in place in case it is being used 71 // as an insert point. 72 Instruction *NewCI = 73 CastInst::Create(Op, V, Ty, "", 74 A->getParent()->getEntryBlock().begin()); 75 NewCI->takeName(CI); 76 CI->replaceAllUsesWith(NewCI); 77 return NewCI; 78 } 79 return CI; 80 } 81 82 Instruction *I = CastInst::Create(Op, V, Ty, V->getName(), 83 A->getParent()->getEntryBlock().begin()); 84 rememberInstruction(I); 85 return I; 86 } 87 88 Instruction *I = cast<Instruction>(V); 89 90 // Check to see if there is already a cast. If there is, use it. 91 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 92 UI != E; ++UI) { 93 if ((*UI)->getType() == Ty) 94 if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) 95 if (CI->getOpcode() == Op) { 96 BasicBlock::iterator It = I; ++It; 97 if (isa<InvokeInst>(I)) 98 It = cast<InvokeInst>(I)->getNormalDest()->begin(); 99 while (isa<PHINode>(It)) ++It; 100 if (It != BasicBlock::iterator(CI)) { 101 // Recreate the cast after the user. 102 // The old cast is left in place in case it is being used 103 // as an insert point. 104 Instruction *NewCI = CastInst::Create(Op, V, Ty, "", It); 105 NewCI->takeName(CI); 106 CI->replaceAllUsesWith(NewCI); 107 rememberInstruction(NewCI); 108 return NewCI; 109 } 110 rememberInstruction(CI); 111 return CI; 112 } 113 } 114 BasicBlock::iterator IP = I; ++IP; 115 if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 116 IP = II->getNormalDest()->begin(); 117 while (isa<PHINode>(IP)) ++IP; 118 Instruction *CI = CastInst::Create(Op, V, Ty, V->getName(), IP); 119 rememberInstruction(CI); 120 return CI; 121} 122 123/// InsertBinop - Insert the specified binary operator, doing a small amount 124/// of work to avoid inserting an obviously redundant operation. 125Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, 126 Value *LHS, Value *RHS) { 127 // Fold a binop with constant operands. 128 if (Constant *CLHS = dyn_cast<Constant>(LHS)) 129 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 130 return ConstantExpr::get(Opcode, CLHS, CRHS); 131 132 // Do a quick scan to see if we have this binop nearby. If so, reuse it. 133 unsigned ScanLimit = 6; 134 BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin(); 135 // Scanning starts from the last instruction before the insertion point. 136 BasicBlock::iterator IP = Builder.GetInsertPoint(); 137 if (IP != BlockBegin) { 138 --IP; 139 for (; ScanLimit; --IP, --ScanLimit) { 140 if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS && 141 IP->getOperand(1) == RHS) 142 return IP; 143 if (IP == BlockBegin) break; 144 } 145 } 146 147 // If we haven't found this binop, insert it. 148 Value *BO = Builder.CreateBinOp(Opcode, LHS, RHS, "tmp"); 149 rememberInstruction(BO); 150 return BO; 151} 152 153/// FactorOutConstant - Test if S is divisible by Factor, using signed 154/// division. If so, update S with Factor divided out and return true. 155/// S need not be evenly divisble if a reasonable remainder can be 156/// computed. 157/// TODO: When ScalarEvolution gets a SCEVSDivExpr, this can be made 158/// unnecessary; in its place, just signed-divide Ops[i] by the scale and 159/// check to see if the divide was folded. 160static bool FactorOutConstant(const SCEV *&S, 161 const SCEV *&Remainder, 162 const SCEV *Factor, 163 ScalarEvolution &SE, 164 const TargetData *TD) { 165 // Everything is divisible by one. 166 if (Factor->isOne()) 167 return true; 168 169 // x/x == 1. 170 if (S == Factor) { 171 S = SE.getIntegerSCEV(1, S->getType()); 172 return true; 173 } 174 175 // For a Constant, check for a multiple of the given factor. 176 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) { 177 // 0/x == 0. 178 if (C->isZero()) 179 return true; 180 // Check for divisibility. 181 if (const SCEVConstant *FC = dyn_cast<SCEVConstant>(Factor)) { 182 ConstantInt *CI = 183 ConstantInt::get(SE.getContext(), 184 C->getValue()->getValue().sdiv( 185 FC->getValue()->getValue())); 186 // If the quotient is zero and the remainder is non-zero, reject 187 // the value at this scale. It will be considered for subsequent 188 // smaller scales. 189 if (!CI->isZero()) { 190 const SCEV *Div = SE.getConstant(CI); 191 S = Div; 192 Remainder = 193 SE.getAddExpr(Remainder, 194 SE.getConstant(C->getValue()->getValue().srem( 195 FC->getValue()->getValue()))); 196 return true; 197 } 198 } 199 } 200 201 // In a Mul, check if there is a constant operand which is a multiple 202 // of the given factor. 203 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) { 204 if (TD) { 205 // With TargetData, the size is known. Check if there is a constant 206 // operand which is a multiple of the given factor. If so, we can 207 // factor it. 208 const SCEVConstant *FC = cast<SCEVConstant>(Factor); 209 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0))) 210 if (!C->getValue()->getValue().srem(FC->getValue()->getValue())) { 211 const SmallVectorImpl<const SCEV *> &MOperands = M->getOperands(); 212 SmallVector<const SCEV *, 4> NewMulOps(MOperands.begin(), 213 MOperands.end()); 214 NewMulOps[0] = 215 SE.getConstant(C->getValue()->getValue().sdiv( 216 FC->getValue()->getValue())); 217 S = SE.getMulExpr(NewMulOps); 218 return true; 219 } 220 } else { 221 // Without TargetData, check if Factor can be factored out of any of the 222 // Mul's operands. If so, we can just remove it. 223 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) { 224 const SCEV *SOp = M->getOperand(i); 225 const SCEV *Remainder = SE.getIntegerSCEV(0, SOp->getType()); 226 if (FactorOutConstant(SOp, Remainder, Factor, SE, TD) && 227 Remainder->isZero()) { 228 const SmallVectorImpl<const SCEV *> &MOperands = M->getOperands(); 229 SmallVector<const SCEV *, 4> NewMulOps(MOperands.begin(), 230 MOperands.end()); 231 NewMulOps[i] = SOp; 232 S = SE.getMulExpr(NewMulOps); 233 return true; 234 } 235 } 236 } 237 } 238 239 // In an AddRec, check if both start and step are divisible. 240 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) { 241 const SCEV *Step = A->getStepRecurrence(SE); 242 const SCEV *StepRem = SE.getIntegerSCEV(0, Step->getType()); 243 if (!FactorOutConstant(Step, StepRem, Factor, SE, TD)) 244 return false; 245 if (!StepRem->isZero()) 246 return false; 247 const SCEV *Start = A->getStart(); 248 if (!FactorOutConstant(Start, Remainder, Factor, SE, TD)) 249 return false; 250 S = SE.getAddRecExpr(Start, Step, A->getLoop()); 251 return true; 252 } 253 254 return false; 255} 256 257/// SimplifyAddOperands - Sort and simplify a list of add operands. NumAddRecs 258/// is the number of SCEVAddRecExprs present, which are kept at the end of 259/// the list. 260/// 261static void SimplifyAddOperands(SmallVectorImpl<const SCEV *> &Ops, 262 const Type *Ty, 263 ScalarEvolution &SE) { 264 unsigned NumAddRecs = 0; 265 for (unsigned i = Ops.size(); i > 0 && isa<SCEVAddRecExpr>(Ops[i-1]); --i) 266 ++NumAddRecs; 267 // Group Ops into non-addrecs and addrecs. 268 SmallVector<const SCEV *, 8> NoAddRecs(Ops.begin(), Ops.end() - NumAddRecs); 269 SmallVector<const SCEV *, 8> AddRecs(Ops.end() - NumAddRecs, Ops.end()); 270 // Let ScalarEvolution sort and simplify the non-addrecs list. 271 const SCEV *Sum = NoAddRecs.empty() ? 272 SE.getIntegerSCEV(0, Ty) : 273 SE.getAddExpr(NoAddRecs); 274 // If it returned an add, use the operands. Otherwise it simplified 275 // the sum into a single value, so just use that. 276 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Sum)) 277 Ops = Add->getOperands(); 278 else { 279 Ops.clear(); 280 if (!Sum->isZero()) 281 Ops.push_back(Sum); 282 } 283 // Then append the addrecs. 284 Ops.insert(Ops.end(), AddRecs.begin(), AddRecs.end()); 285} 286 287/// SplitAddRecs - Flatten a list of add operands, moving addrec start values 288/// out to the top level. For example, convert {a + b,+,c} to a, b, {0,+,d}. 289/// This helps expose more opportunities for folding parts of the expressions 290/// into GEP indices. 291/// 292static void SplitAddRecs(SmallVectorImpl<const SCEV *> &Ops, 293 const Type *Ty, 294 ScalarEvolution &SE) { 295 // Find the addrecs. 296 SmallVector<const SCEV *, 8> AddRecs; 297 for (unsigned i = 0, e = Ops.size(); i != e; ++i) 298 while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i])) { 299 const SCEV *Start = A->getStart(); 300 if (Start->isZero()) break; 301 const SCEV *Zero = SE.getIntegerSCEV(0, Ty); 302 AddRecs.push_back(SE.getAddRecExpr(Zero, 303 A->getStepRecurrence(SE), 304 A->getLoop())); 305 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Start)) { 306 Ops[i] = Zero; 307 Ops.insert(Ops.end(), Add->op_begin(), Add->op_end()); 308 e += Add->getNumOperands(); 309 } else { 310 Ops[i] = Start; 311 } 312 } 313 if (!AddRecs.empty()) { 314 // Add the addrecs onto the end of the list. 315 Ops.insert(Ops.end(), AddRecs.begin(), AddRecs.end()); 316 // Resort the operand list, moving any constants to the front. 317 SimplifyAddOperands(Ops, Ty, SE); 318 } 319} 320 321/// expandAddToGEP - Expand an addition expression with a pointer type into 322/// a GEP instead of using ptrtoint+arithmetic+inttoptr. This helps 323/// BasicAliasAnalysis and other passes analyze the result. See the rules 324/// for getelementptr vs. inttoptr in 325/// http://llvm.org/docs/LangRef.html#pointeraliasing 326/// for details. 327/// 328/// Design note: The correctness of using getelementptr here depends on 329/// ScalarEvolution not recognizing inttoptr and ptrtoint operators, as 330/// they may introduce pointer arithmetic which may not be safely converted 331/// into getelementptr. 332/// 333/// Design note: It might seem desirable for this function to be more 334/// loop-aware. If some of the indices are loop-invariant while others 335/// aren't, it might seem desirable to emit multiple GEPs, keeping the 336/// loop-invariant portions of the overall computation outside the loop. 337/// However, there are a few reasons this is not done here. Hoisting simple 338/// arithmetic is a low-level optimization that often isn't very 339/// important until late in the optimization process. In fact, passes 340/// like InstructionCombining will combine GEPs, even if it means 341/// pushing loop-invariant computation down into loops, so even if the 342/// GEPs were split here, the work would quickly be undone. The 343/// LoopStrengthReduction pass, which is usually run quite late (and 344/// after the last InstructionCombining pass), takes care of hoisting 345/// loop-invariant portions of expressions, after considering what 346/// can be folded using target addressing modes. 347/// 348Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin, 349 const SCEV *const *op_end, 350 const PointerType *PTy, 351 const Type *Ty, 352 Value *V) { 353 const Type *ElTy = PTy->getElementType(); 354 SmallVector<Value *, 4> GepIndices; 355 SmallVector<const SCEV *, 8> Ops(op_begin, op_end); 356 bool AnyNonZeroIndices = false; 357 358 // Split AddRecs up into parts as either of the parts may be usable 359 // without the other. 360 SplitAddRecs(Ops, Ty, SE); 361 362 // Descend down the pointer's type and attempt to convert the other 363 // operands into GEP indices, at each level. The first index in a GEP 364 // indexes into the array implied by the pointer operand; the rest of 365 // the indices index into the element or field type selected by the 366 // preceding index. 367 for (;;) { 368 const SCEV *ElSize = SE.getAllocSizeExpr(ElTy); 369 // If the scale size is not 0, attempt to factor out a scale for 370 // array indexing. 371 SmallVector<const SCEV *, 8> ScaledOps; 372 if (ElTy->isSized() && !ElSize->isZero()) { 373 SmallVector<const SCEV *, 8> NewOps; 374 for (unsigned i = 0, e = Ops.size(); i != e; ++i) { 375 const SCEV *Op = Ops[i]; 376 const SCEV *Remainder = SE.getIntegerSCEV(0, Ty); 377 if (FactorOutConstant(Op, Remainder, ElSize, SE, SE.TD)) { 378 // Op now has ElSize factored out. 379 ScaledOps.push_back(Op); 380 if (!Remainder->isZero()) 381 NewOps.push_back(Remainder); 382 AnyNonZeroIndices = true; 383 } else { 384 // The operand was not divisible, so add it to the list of operands 385 // we'll scan next iteration. 386 NewOps.push_back(Ops[i]); 387 } 388 } 389 // If we made any changes, update Ops. 390 if (!ScaledOps.empty()) { 391 Ops = NewOps; 392 SimplifyAddOperands(Ops, Ty, SE); 393 } 394 } 395 396 // Record the scaled array index for this level of the type. If 397 // we didn't find any operands that could be factored, tentatively 398 // assume that element zero was selected (since the zero offset 399 // would obviously be folded away). 400 Value *Scaled = ScaledOps.empty() ? 401 Constant::getNullValue(Ty) : 402 expandCodeFor(SE.getAddExpr(ScaledOps), Ty); 403 GepIndices.push_back(Scaled); 404 405 // Collect struct field index operands. 406 while (const StructType *STy = dyn_cast<StructType>(ElTy)) { 407 bool FoundFieldNo = false; 408 // An empty struct has no fields. 409 if (STy->getNumElements() == 0) break; 410 if (SE.TD) { 411 // With TargetData, field offsets are known. See if a constant offset 412 // falls within any of the struct fields. 413 if (Ops.empty()) break; 414 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0])) 415 if (SE.getTypeSizeInBits(C->getType()) <= 64) { 416 const StructLayout &SL = *SE.TD->getStructLayout(STy); 417 uint64_t FullOffset = C->getValue()->getZExtValue(); 418 if (FullOffset < SL.getSizeInBytes()) { 419 unsigned ElIdx = SL.getElementContainingOffset(FullOffset); 420 GepIndices.push_back( 421 ConstantInt::get(Type::getInt32Ty(Ty->getContext()), ElIdx)); 422 ElTy = STy->getTypeAtIndex(ElIdx); 423 Ops[0] = 424 SE.getConstant(Ty, FullOffset - SL.getElementOffset(ElIdx)); 425 AnyNonZeroIndices = true; 426 FoundFieldNo = true; 427 } 428 } 429 } else { 430 // Without TargetData, just check for a SCEVFieldOffsetExpr of the 431 // appropriate struct type. 432 for (unsigned i = 0, e = Ops.size(); i != e; ++i) 433 if (const SCEVFieldOffsetExpr *FO = 434 dyn_cast<SCEVFieldOffsetExpr>(Ops[i])) 435 if (FO->getStructType() == STy) { 436 unsigned FieldNo = FO->getFieldNo(); 437 GepIndices.push_back( 438 ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 439 FieldNo)); 440 ElTy = STy->getTypeAtIndex(FieldNo); 441 Ops[i] = SE.getConstant(Ty, 0); 442 AnyNonZeroIndices = true; 443 FoundFieldNo = true; 444 break; 445 } 446 } 447 // If no struct field offsets were found, tentatively assume that 448 // field zero was selected (since the zero offset would obviously 449 // be folded away). 450 if (!FoundFieldNo) { 451 ElTy = STy->getTypeAtIndex(0u); 452 GepIndices.push_back( 453 Constant::getNullValue(Type::getInt32Ty(Ty->getContext()))); 454 } 455 } 456 457 if (const ArrayType *ATy = dyn_cast<ArrayType>(ElTy)) 458 ElTy = ATy->getElementType(); 459 else 460 break; 461 } 462 463 // If none of the operands were convertable to proper GEP indices, cast 464 // the base to i8* and do an ugly getelementptr with that. It's still 465 // better than ptrtoint+arithmetic+inttoptr at least. 466 if (!AnyNonZeroIndices) { 467 // Cast the base to i8*. 468 V = InsertNoopCastOfTo(V, 469 Type::getInt8PtrTy(Ty->getContext(), PTy->getAddressSpace())); 470 471 // Expand the operands for a plain byte offset. 472 Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty); 473 474 // Fold a GEP with constant operands. 475 if (Constant *CLHS = dyn_cast<Constant>(V)) 476 if (Constant *CRHS = dyn_cast<Constant>(Idx)) 477 return ConstantExpr::getGetElementPtr(CLHS, &CRHS, 1); 478 479 // Do a quick scan to see if we have this GEP nearby. If so, reuse it. 480 unsigned ScanLimit = 6; 481 BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin(); 482 // Scanning starts from the last instruction before the insertion point. 483 BasicBlock::iterator IP = Builder.GetInsertPoint(); 484 if (IP != BlockBegin) { 485 --IP; 486 for (; ScanLimit; --IP, --ScanLimit) { 487 if (IP->getOpcode() == Instruction::GetElementPtr && 488 IP->getOperand(0) == V && IP->getOperand(1) == Idx) 489 return IP; 490 if (IP == BlockBegin) break; 491 } 492 } 493 494 // Emit a GEP. 495 Value *GEP = Builder.CreateGEP(V, Idx, "uglygep"); 496 rememberInstruction(GEP); 497 return GEP; 498 } 499 500 // Insert a pretty getelementptr. Note that this GEP is not marked inbounds, 501 // because ScalarEvolution may have changed the address arithmetic to 502 // compute a value which is beyond the end of the allocated object. 503 Value *Casted = V; 504 if (V->getType() != PTy) 505 Casted = InsertNoopCastOfTo(Casted, PTy); 506 Value *GEP = Builder.CreateGEP(Casted, 507 GepIndices.begin(), 508 GepIndices.end(), 509 "scevgep"); 510 Ops.push_back(SE.getUnknown(GEP)); 511 rememberInstruction(GEP); 512 return expand(SE.getAddExpr(Ops)); 513} 514 515/// isNonConstantNegative - Return true if the specified scev is negated, but 516/// not a constant. 517static bool isNonConstantNegative(const SCEV *F) { 518 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(F); 519 if (!Mul) return false; 520 521 // If there is a constant factor, it will be first. 522 const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0)); 523 if (!SC) return false; 524 525 // Return true if the value is negative, this matches things like (-42 * V). 526 return SC->getValue()->getValue().isNegative(); 527} 528 529Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) { 530 int NumOperands = S->getNumOperands(); 531 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 532 533 // Find the index of an operand to start with. Choose the operand with 534 // pointer type, if there is one, or the last operand otherwise. 535 int PIdx = 0; 536 for (; PIdx != NumOperands - 1; ++PIdx) 537 if (isa<PointerType>(S->getOperand(PIdx)->getType())) break; 538 539 // Expand code for the operand that we chose. 540 Value *V = expand(S->getOperand(PIdx)); 541 542 // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the 543 // comments on expandAddToGEP for details. 544 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) { 545 // Take the operand at PIdx out of the list. 546 const SmallVectorImpl<const SCEV *> &Ops = S->getOperands(); 547 SmallVector<const SCEV *, 8> NewOps; 548 NewOps.insert(NewOps.end(), Ops.begin(), Ops.begin() + PIdx); 549 NewOps.insert(NewOps.end(), Ops.begin() + PIdx + 1, Ops.end()); 550 // Make a GEP. 551 return expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, V); 552 } 553 554 // Otherwise, we'll expand the rest of the SCEVAddExpr as plain integer 555 // arithmetic. 556 V = InsertNoopCastOfTo(V, Ty); 557 558 // Emit a bunch of add instructions 559 for (int i = NumOperands-1; i >= 0; --i) { 560 if (i == PIdx) continue; 561 const SCEV *Op = S->getOperand(i); 562 if (isNonConstantNegative(Op)) { 563 Value *W = expandCodeFor(SE.getNegativeSCEV(Op), Ty); 564 V = InsertBinop(Instruction::Sub, V, W); 565 } else { 566 Value *W = expandCodeFor(Op, Ty); 567 V = InsertBinop(Instruction::Add, V, W); 568 } 569 } 570 return V; 571} 572 573Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) { 574 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 575 int FirstOp = 0; // Set if we should emit a subtract. 576 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0))) 577 if (SC->getValue()->isAllOnesValue()) 578 FirstOp = 1; 579 580 int i = S->getNumOperands()-2; 581 Value *V = expandCodeFor(S->getOperand(i+1), Ty); 582 583 // Emit a bunch of multiply instructions 584 for (; i >= FirstOp; --i) { 585 Value *W = expandCodeFor(S->getOperand(i), Ty); 586 V = InsertBinop(Instruction::Mul, V, W); 587 } 588 589 // -1 * ... ---> 0 - ... 590 if (FirstOp == 1) 591 V = InsertBinop(Instruction::Sub, Constant::getNullValue(Ty), V); 592 return V; 593} 594 595Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) { 596 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 597 598 Value *LHS = expandCodeFor(S->getLHS(), Ty); 599 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getRHS())) { 600 const APInt &RHS = SC->getValue()->getValue(); 601 if (RHS.isPowerOf2()) 602 return InsertBinop(Instruction::LShr, LHS, 603 ConstantInt::get(Ty, RHS.logBase2())); 604 } 605 606 Value *RHS = expandCodeFor(S->getRHS(), Ty); 607 return InsertBinop(Instruction::UDiv, LHS, RHS); 608} 609 610/// Move parts of Base into Rest to leave Base with the minimal 611/// expression that provides a pointer operand suitable for a 612/// GEP expansion. 613static void ExposePointerBase(const SCEV *&Base, const SCEV *&Rest, 614 ScalarEvolution &SE) { 615 while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) { 616 Base = A->getStart(); 617 Rest = SE.getAddExpr(Rest, 618 SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()), 619 A->getStepRecurrence(SE), 620 A->getLoop())); 621 } 622 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) { 623 Base = A->getOperand(A->getNumOperands()-1); 624 SmallVector<const SCEV *, 8> NewAddOps(A->op_begin(), A->op_end()); 625 NewAddOps.back() = Rest; 626 Rest = SE.getAddExpr(NewAddOps); 627 ExposePointerBase(Base, Rest, SE); 628 } 629} 630 631/// getAddRecExprPHILiterally - Helper for expandAddRecExprLiterally. Expand 632/// the base addrec, which is the addrec without any non-loop-dominating 633/// values, and return the PHI. 634PHINode * 635SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized, 636 const Loop *L, 637 const Type *ExpandTy, 638 const Type *IntTy) { 639 // Reuse a previously-inserted PHI, if present. 640 for (BasicBlock::iterator I = L->getHeader()->begin(); 641 PHINode *PN = dyn_cast<PHINode>(I); ++I) 642 if (isInsertedInstruction(PN) && SE.getSCEV(PN) == Normalized) 643 return PN; 644 645 // Save the original insertion point so we can restore it when we're done. 646 BasicBlock *SaveInsertBB = Builder.GetInsertBlock(); 647 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint(); 648 649 // Expand code for the start value. 650 Value *StartV = expandCodeFor(Normalized->getStart(), ExpandTy, 651 L->getHeader()->begin()); 652 653 // Expand code for the step value. Insert instructions right before the 654 // terminator corresponding to the back-edge. Do this before creating the PHI 655 // so that PHI reuse code doesn't see an incomplete PHI. If the stride is 656 // negative, insert a sub instead of an add for the increment (unless it's a 657 // constant, because subtracts of constants are canonicalized to adds). 658 const SCEV *Step = Normalized->getStepRecurrence(SE); 659 bool isPointer = isa<PointerType>(ExpandTy); 660 bool isNegative = !isPointer && isNonConstantNegative(Step); 661 if (isNegative) 662 Step = SE.getNegativeSCEV(Step); 663 Value *StepV = expandCodeFor(Step, IntTy, L->getHeader()->begin()); 664 665 // Create the PHI. 666 Builder.SetInsertPoint(L->getHeader(), L->getHeader()->begin()); 667 PHINode *PN = Builder.CreatePHI(ExpandTy, "lsr.iv"); 668 rememberInstruction(PN); 669 670 // Create the step instructions and populate the PHI. 671 BasicBlock *Header = L->getHeader(); 672 for (pred_iterator HPI = pred_begin(Header), HPE = pred_end(Header); 673 HPI != HPE; ++HPI) { 674 BasicBlock *Pred = *HPI; 675 676 // Add a start value. 677 if (!L->contains(Pred)) { 678 PN->addIncoming(StartV, Pred); 679 continue; 680 } 681 682 // Create a step value and add it to the PHI. If IVIncInsertLoop is 683 // non-null and equal to the addrec's loop, insert the instructions 684 // at IVIncInsertPos. 685 Instruction *InsertPos = L == IVIncInsertLoop ? 686 IVIncInsertPos : Pred->getTerminator(); 687 Builder.SetInsertPoint(InsertPos->getParent(), InsertPos); 688 Value *IncV; 689 // If the PHI is a pointer, use a GEP, otherwise use an add or sub. 690 if (isPointer) { 691 const PointerType *GEPPtrTy = cast<PointerType>(ExpandTy); 692 // If the step isn't constant, don't use an implicitly scaled GEP, because 693 // that would require a multiply inside the loop. 694 if (!isa<ConstantInt>(StepV)) 695 GEPPtrTy = PointerType::get(Type::getInt1Ty(SE.getContext()), 696 GEPPtrTy->getAddressSpace()); 697 const SCEV *const StepArray[1] = { SE.getSCEV(StepV) }; 698 IncV = expandAddToGEP(StepArray, StepArray+1, GEPPtrTy, IntTy, PN); 699 if (IncV->getType() != PN->getType()) { 700 IncV = Builder.CreateBitCast(IncV, PN->getType(), "tmp"); 701 rememberInstruction(IncV); 702 } 703 } else { 704 IncV = isNegative ? 705 Builder.CreateSub(PN, StepV, "lsr.iv.next") : 706 Builder.CreateAdd(PN, StepV, "lsr.iv.next"); 707 rememberInstruction(IncV); 708 } 709 PN->addIncoming(IncV, Pred); 710 } 711 712 // Restore the original insert point. 713 if (SaveInsertBB) 714 Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt); 715 716 // Remember this PHI, even in post-inc mode. 717 InsertedValues.insert(PN); 718 719 return PN; 720} 721 722Value *SCEVExpander::expandAddRecExprLiterally(const SCEVAddRecExpr *S) { 723 const Type *STy = S->getType(); 724 const Type *IntTy = SE.getEffectiveSCEVType(STy); 725 const Loop *L = S->getLoop(); 726 727 // Determine a normalized form of this expression, which is the expression 728 // before any post-inc adjustment is made. 729 const SCEVAddRecExpr *Normalized = S; 730 if (L == PostIncLoop) { 731 const SCEV *Step = S->getStepRecurrence(SE); 732 Normalized = cast<SCEVAddRecExpr>(SE.getMinusSCEV(S, Step)); 733 } 734 735 // Strip off any non-loop-dominating component from the addrec start. 736 const SCEV *Start = Normalized->getStart(); 737 const SCEV *PostLoopOffset = 0; 738 if (!Start->properlyDominates(L->getHeader(), SE.DT)) { 739 PostLoopOffset = Start; 740 Start = SE.getIntegerSCEV(0, Normalized->getType()); 741 Normalized = 742 cast<SCEVAddRecExpr>(SE.getAddRecExpr(Start, 743 Normalized->getStepRecurrence(SE), 744 Normalized->getLoop())); 745 } 746 747 // Strip off any non-loop-dominating component from the addrec step. 748 const SCEV *Step = Normalized->getStepRecurrence(SE); 749 const SCEV *PostLoopScale = 0; 750 if (!Step->hasComputableLoopEvolution(L) && 751 !Step->dominates(L->getHeader(), SE.DT)) { 752 PostLoopScale = Step; 753 Step = SE.getIntegerSCEV(1, Normalized->getType()); 754 Normalized = 755 cast<SCEVAddRecExpr>(SE.getAddRecExpr(Start, Step, 756 Normalized->getLoop())); 757 } 758 759 // Expand the core addrec. If we need post-loop scaling, force it to 760 // expand to an integer type to avoid the need for additional casting. 761 const Type *ExpandTy = PostLoopScale ? IntTy : STy; 762 PHINode *PN = getAddRecExprPHILiterally(Normalized, L, ExpandTy, IntTy); 763 764 // Accomodate post-inc mode, if necessary. 765 Value *Result; 766 if (L != PostIncLoop) 767 Result = PN; 768 else { 769 // In PostInc mode, use the post-incremented value. 770 BasicBlock *LatchBlock = L->getLoopLatch(); 771 assert(LatchBlock && "PostInc mode requires a unique loop latch!"); 772 Result = PN->getIncomingValueForBlock(LatchBlock); 773 } 774 775 // Re-apply any non-loop-dominating scale. 776 if (PostLoopScale) { 777 Result = Builder.CreateMul(Result, 778 expandCodeFor(PostLoopScale, IntTy)); 779 rememberInstruction(Result); 780 } 781 782 // Re-apply any non-loop-dominating offset. 783 if (PostLoopOffset) { 784 if (const PointerType *PTy = dyn_cast<PointerType>(ExpandTy)) { 785 const SCEV *const OffsetArray[1] = { PostLoopOffset }; 786 Result = expandAddToGEP(OffsetArray, OffsetArray+1, PTy, IntTy, Result); 787 } else { 788 Result = Builder.CreateAdd(Result, 789 expandCodeFor(PostLoopOffset, IntTy)); 790 rememberInstruction(Result); 791 } 792 } 793 794 return Result; 795} 796 797Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) { 798 if (!CanonicalMode) return expandAddRecExprLiterally(S); 799 800 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 801 const Loop *L = S->getLoop(); 802 803 // First check for an existing canonical IV in a suitable type. 804 PHINode *CanonicalIV = 0; 805 if (PHINode *PN = L->getCanonicalInductionVariable()) 806 if (SE.isSCEVable(PN->getType()) && 807 isa<IntegerType>(SE.getEffectiveSCEVType(PN->getType())) && 808 SE.getTypeSizeInBits(PN->getType()) >= SE.getTypeSizeInBits(Ty)) 809 CanonicalIV = PN; 810 811 // Rewrite an AddRec in terms of the canonical induction variable, if 812 // its type is more narrow. 813 if (CanonicalIV && 814 SE.getTypeSizeInBits(CanonicalIV->getType()) > 815 SE.getTypeSizeInBits(Ty)) { 816 const SmallVectorImpl<const SCEV *> &Ops = S->getOperands(); 817 SmallVector<const SCEV *, 4> NewOps(Ops.size()); 818 for (unsigned i = 0, e = Ops.size(); i != e; ++i) 819 NewOps[i] = SE.getAnyExtendExpr(Ops[i], CanonicalIV->getType()); 820 Value *V = expand(SE.getAddRecExpr(NewOps, S->getLoop())); 821 BasicBlock *SaveInsertBB = Builder.GetInsertBlock(); 822 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint(); 823 BasicBlock::iterator NewInsertPt = 824 llvm::next(BasicBlock::iterator(cast<Instruction>(V))); 825 while (isa<PHINode>(NewInsertPt)) ++NewInsertPt; 826 V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), 0, 827 NewInsertPt); 828 Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt); 829 return V; 830 } 831 832 // {X,+,F} --> X + {0,+,F} 833 if (!S->getStart()->isZero()) { 834 const SmallVectorImpl<const SCEV *> &SOperands = S->getOperands(); 835 SmallVector<const SCEV *, 4> NewOps(SOperands.begin(), SOperands.end()); 836 NewOps[0] = SE.getIntegerSCEV(0, Ty); 837 const SCEV *Rest = SE.getAddRecExpr(NewOps, L); 838 839 // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the 840 // comments on expandAddToGEP for details. 841 const SCEV *Base = S->getStart(); 842 const SCEV *RestArray[1] = { Rest }; 843 // Dig into the expression to find the pointer base for a GEP. 844 ExposePointerBase(Base, RestArray[0], SE); 845 // If we found a pointer, expand the AddRec with a GEP. 846 if (const PointerType *PTy = dyn_cast<PointerType>(Base->getType())) { 847 // Make sure the Base isn't something exotic, such as a multiplied 848 // or divided pointer value. In those cases, the result type isn't 849 // actually a pointer type. 850 if (!isa<SCEVMulExpr>(Base) && !isa<SCEVUDivExpr>(Base)) { 851 Value *StartV = expand(Base); 852 assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!"); 853 return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV); 854 } 855 } 856 857 // Just do a normal add. Pre-expand the operands to suppress folding. 858 return expand(SE.getAddExpr(SE.getUnknown(expand(S->getStart())), 859 SE.getUnknown(expand(Rest)))); 860 } 861 862 // {0,+,1} --> Insert a canonical induction variable into the loop! 863 if (S->isAffine() && 864 S->getOperand(1) == SE.getIntegerSCEV(1, Ty)) { 865 // If there's a canonical IV, just use it. 866 if (CanonicalIV) { 867 assert(Ty == SE.getEffectiveSCEVType(CanonicalIV->getType()) && 868 "IVs with types different from the canonical IV should " 869 "already have been handled!"); 870 return CanonicalIV; 871 } 872 873 // Create and insert the PHI node for the induction variable in the 874 // specified loop. 875 BasicBlock *Header = L->getHeader(); 876 PHINode *PN = PHINode::Create(Ty, "indvar", Header->begin()); 877 rememberInstruction(PN); 878 879 Constant *One = ConstantInt::get(Ty, 1); 880 for (pred_iterator HPI = pred_begin(Header), HPE = pred_end(Header); 881 HPI != HPE; ++HPI) 882 if (L->contains(*HPI)) { 883 // Insert a unit add instruction right before the terminator 884 // corresponding to the back-edge. 885 Instruction *Add = BinaryOperator::CreateAdd(PN, One, "indvar.next", 886 (*HPI)->getTerminator()); 887 rememberInstruction(Add); 888 PN->addIncoming(Add, *HPI); 889 } else { 890 PN->addIncoming(Constant::getNullValue(Ty), *HPI); 891 } 892 } 893 894 // {0,+,F} --> {0,+,1} * F 895 // Get the canonical induction variable I for this loop. 896 Value *I = CanonicalIV ? 897 CanonicalIV : 898 getOrInsertCanonicalInductionVariable(L, Ty); 899 900 // If this is a simple linear addrec, emit it now as a special case. 901 if (S->isAffine()) // {0,+,F} --> i*F 902 return 903 expand(SE.getTruncateOrNoop( 904 SE.getMulExpr(SE.getUnknown(I), 905 SE.getNoopOrAnyExtend(S->getOperand(1), 906 I->getType())), 907 Ty)); 908 909 // If this is a chain of recurrences, turn it into a closed form, using the 910 // folders, then expandCodeFor the closed form. This allows the folders to 911 // simplify the expression without having to build a bunch of special code 912 // into this folder. 913 const SCEV *IH = SE.getUnknown(I); // Get I as a "symbolic" SCEV. 914 915 // Promote S up to the canonical IV type, if the cast is foldable. 916 const SCEV *NewS = S; 917 const SCEV *Ext = SE.getNoopOrAnyExtend(S, I->getType()); 918 if (isa<SCEVAddRecExpr>(Ext)) 919 NewS = Ext; 920 921 const SCEV *V = cast<SCEVAddRecExpr>(NewS)->evaluateAtIteration(IH, SE); 922 //cerr << "Evaluated: " << *this << "\n to: " << *V << "\n"; 923 924 // Truncate the result down to the original type, if needed. 925 const SCEV *T = SE.getTruncateOrNoop(V, Ty); 926 return expand(T); 927} 928 929Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) { 930 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 931 Value *V = expandCodeFor(S->getOperand(), 932 SE.getEffectiveSCEVType(S->getOperand()->getType())); 933 Value *I = Builder.CreateTrunc(V, Ty, "tmp"); 934 rememberInstruction(I); 935 return I; 936} 937 938Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) { 939 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 940 Value *V = expandCodeFor(S->getOperand(), 941 SE.getEffectiveSCEVType(S->getOperand()->getType())); 942 Value *I = Builder.CreateZExt(V, Ty, "tmp"); 943 rememberInstruction(I); 944 return I; 945} 946 947Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) { 948 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 949 Value *V = expandCodeFor(S->getOperand(), 950 SE.getEffectiveSCEVType(S->getOperand()->getType())); 951 Value *I = Builder.CreateSExt(V, Ty, "tmp"); 952 rememberInstruction(I); 953 return I; 954} 955 956Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) { 957 Value *LHS = expand(S->getOperand(S->getNumOperands()-1)); 958 const Type *Ty = LHS->getType(); 959 for (int i = S->getNumOperands()-2; i >= 0; --i) { 960 // In the case of mixed integer and pointer types, do the 961 // rest of the comparisons as integer. 962 if (S->getOperand(i)->getType() != Ty) { 963 Ty = SE.getEffectiveSCEVType(Ty); 964 LHS = InsertNoopCastOfTo(LHS, Ty); 965 } 966 Value *RHS = expandCodeFor(S->getOperand(i), Ty); 967 Value *ICmp = Builder.CreateICmpSGT(LHS, RHS, "tmp"); 968 rememberInstruction(ICmp); 969 Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "smax"); 970 rememberInstruction(Sel); 971 LHS = Sel; 972 } 973 // In the case of mixed integer and pointer types, cast the 974 // final result back to the pointer type. 975 if (LHS->getType() != S->getType()) 976 LHS = InsertNoopCastOfTo(LHS, S->getType()); 977 return LHS; 978} 979 980Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) { 981 Value *LHS = expand(S->getOperand(S->getNumOperands()-1)); 982 const Type *Ty = LHS->getType(); 983 for (int i = S->getNumOperands()-2; i >= 0; --i) { 984 // In the case of mixed integer and pointer types, do the 985 // rest of the comparisons as integer. 986 if (S->getOperand(i)->getType() != Ty) { 987 Ty = SE.getEffectiveSCEVType(Ty); 988 LHS = InsertNoopCastOfTo(LHS, Ty); 989 } 990 Value *RHS = expandCodeFor(S->getOperand(i), Ty); 991 Value *ICmp = Builder.CreateICmpUGT(LHS, RHS, "tmp"); 992 rememberInstruction(ICmp); 993 Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "umax"); 994 rememberInstruction(Sel); 995 LHS = Sel; 996 } 997 // In the case of mixed integer and pointer types, cast the 998 // final result back to the pointer type. 999 if (LHS->getType() != S->getType()) 1000 LHS = InsertNoopCastOfTo(LHS, S->getType()); 1001 return LHS; 1002} 1003 1004Value *SCEVExpander::visitFieldOffsetExpr(const SCEVFieldOffsetExpr *S) { 1005 return ConstantExpr::getOffsetOf(S->getStructType(), S->getFieldNo()); 1006} 1007 1008Value *SCEVExpander::visitAllocSizeExpr(const SCEVAllocSizeExpr *S) { 1009 return ConstantExpr::getSizeOf(S->getAllocType()); 1010} 1011 1012Value *SCEVExpander::expandCodeFor(const SCEV *SH, const Type *Ty) { 1013 // Expand the code for this SCEV. 1014 Value *V = expand(SH); 1015 if (Ty) { 1016 assert(SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(SH->getType()) && 1017 "non-trivial casts should be done with the SCEVs directly!"); 1018 V = InsertNoopCastOfTo(V, Ty); 1019 } 1020 return V; 1021} 1022 1023Value *SCEVExpander::expand(const SCEV *S) { 1024 // Compute an insertion point for this SCEV object. Hoist the instructions 1025 // as far out in the loop nest as possible. 1026 Instruction *InsertPt = Builder.GetInsertPoint(); 1027 for (Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock()); ; 1028 L = L->getParentLoop()) 1029 if (S->isLoopInvariant(L)) { 1030 if (!L) break; 1031 if (BasicBlock *Preheader = L->getLoopPreheader()) 1032 InsertPt = Preheader->getTerminator(); 1033 } else { 1034 // If the SCEV is computable at this level, insert it into the header 1035 // after the PHIs (and after any other instructions that we've inserted 1036 // there) so that it is guaranteed to dominate any user inside the loop. 1037 if (L && S->hasComputableLoopEvolution(L)) 1038 InsertPt = L->getHeader()->getFirstNonPHI(); 1039 while (isInsertedInstruction(InsertPt)) 1040 InsertPt = llvm::next(BasicBlock::iterator(InsertPt)); 1041 break; 1042 } 1043 1044 // Check to see if we already expanded this here. 1045 std::map<std::pair<const SCEV *, Instruction *>, 1046 AssertingVH<Value> >::iterator I = 1047 InsertedExpressions.find(std::make_pair(S, InsertPt)); 1048 if (I != InsertedExpressions.end()) 1049 return I->second; 1050 1051 BasicBlock *SaveInsertBB = Builder.GetInsertBlock(); 1052 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint(); 1053 Builder.SetInsertPoint(InsertPt->getParent(), InsertPt); 1054 1055 // Expand the expression into instructions. 1056 Value *V = visit(S); 1057 1058 // Remember the expanded value for this SCEV at this location. 1059 if (!PostIncLoop) 1060 InsertedExpressions[std::make_pair(S, InsertPt)] = V; 1061 1062 Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt); 1063 return V; 1064} 1065 1066/// getOrInsertCanonicalInductionVariable - This method returns the 1067/// canonical induction variable of the specified type for the specified 1068/// loop (inserting one if there is none). A canonical induction variable 1069/// starts at zero and steps by one on each iteration. 1070Value * 1071SCEVExpander::getOrInsertCanonicalInductionVariable(const Loop *L, 1072 const Type *Ty) { 1073 assert(Ty->isInteger() && "Can only insert integer induction variables!"); 1074 const SCEV *H = SE.getAddRecExpr(SE.getIntegerSCEV(0, Ty), 1075 SE.getIntegerSCEV(1, Ty), L); 1076 BasicBlock *SaveInsertBB = Builder.GetInsertBlock(); 1077 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint(); 1078 Value *V = expandCodeFor(H, 0, L->getHeader()->begin()); 1079 if (SaveInsertBB) 1080 Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt); 1081 return V; 1082} 1083