ScalarEvolutionExpander.cpp revision fb5a3419f351056e0f599699d276bcab412d2cce
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/Target/TargetData.h" 19using namespace llvm; 20 21/// InsertCastOfTo - Insert a cast of V to the specified type, doing what 22/// we can to share the casts. 23Value *SCEVExpander::InsertCastOfTo(Instruction::CastOps opcode, Value *V, 24 const Type *Ty) { 25 // Short-circuit unnecessary bitcasts. 26 if (opcode == Instruction::BitCast && V->getType() == Ty) 27 return V; 28 29 // Short-circuit unnecessary inttoptr<->ptrtoint casts. 30 if ((opcode == Instruction::PtrToInt || opcode == Instruction::IntToPtr) && 31 SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) { 32 if (CastInst *CI = dyn_cast<CastInst>(V)) 33 if ((CI->getOpcode() == Instruction::PtrToInt || 34 CI->getOpcode() == Instruction::IntToPtr) && 35 SE.getTypeSizeInBits(CI->getType()) == 36 SE.getTypeSizeInBits(CI->getOperand(0)->getType())) 37 return CI->getOperand(0); 38 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 39 if ((CE->getOpcode() == Instruction::PtrToInt || 40 CE->getOpcode() == Instruction::IntToPtr) && 41 SE.getTypeSizeInBits(CE->getType()) == 42 SE.getTypeSizeInBits(CE->getOperand(0)->getType())) 43 return CE->getOperand(0); 44 } 45 46 // FIXME: keep track of the cast instruction. 47 if (Constant *C = dyn_cast<Constant>(V)) 48 return ConstantExpr::getCast(opcode, C, Ty); 49 50 if (Argument *A = dyn_cast<Argument>(V)) { 51 // Check to see if there is already a cast! 52 for (Value::use_iterator UI = A->use_begin(), E = A->use_end(); 53 UI != E; ++UI) { 54 if ((*UI)->getType() == Ty) 55 if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) 56 if (CI->getOpcode() == opcode) { 57 // If the cast isn't the first instruction of the function, move it. 58 if (BasicBlock::iterator(CI) != 59 A->getParent()->getEntryBlock().begin()) { 60 // If the CastInst is the insert point, change the insert point. 61 if (CI == InsertPt) ++InsertPt; 62 // Splice the cast at the beginning of the entry block. 63 CI->moveBefore(A->getParent()->getEntryBlock().begin()); 64 } 65 return CI; 66 } 67 } 68 Instruction *I = CastInst::Create(opcode, V, Ty, V->getName(), 69 A->getParent()->getEntryBlock().begin()); 70 InsertedValues.insert(I); 71 return I; 72 } 73 74 Instruction *I = cast<Instruction>(V); 75 76 // Check to see if there is already a cast. If there is, use it. 77 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 78 UI != E; ++UI) { 79 if ((*UI)->getType() == Ty) 80 if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) 81 if (CI->getOpcode() == opcode) { 82 BasicBlock::iterator It = I; ++It; 83 if (isa<InvokeInst>(I)) 84 It = cast<InvokeInst>(I)->getNormalDest()->begin(); 85 while (isa<PHINode>(It)) ++It; 86 if (It != BasicBlock::iterator(CI)) { 87 // If the CastInst is the insert point, change the insert point. 88 if (CI == InsertPt) ++InsertPt; 89 // Splice the cast immediately after the operand in question. 90 CI->moveBefore(It); 91 } 92 return CI; 93 } 94 } 95 BasicBlock::iterator IP = I; ++IP; 96 if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 97 IP = II->getNormalDest()->begin(); 98 while (isa<PHINode>(IP)) ++IP; 99 Instruction *CI = CastInst::Create(opcode, V, Ty, V->getName(), IP); 100 InsertedValues.insert(CI); 101 return CI; 102} 103 104/// InsertNoopCastOfTo - Insert a cast of V to the specified type, 105/// which must be possible with a noop cast. 106Value *SCEVExpander::InsertNoopCastOfTo(Value *V, const Type *Ty) { 107 Instruction::CastOps Op = CastInst::getCastOpcode(V, false, Ty, false); 108 assert((Op == Instruction::BitCast || 109 Op == Instruction::PtrToInt || 110 Op == Instruction::IntToPtr) && 111 "InsertNoopCastOfTo cannot perform non-noop casts!"); 112 assert(SE.getTypeSizeInBits(V->getType()) == SE.getTypeSizeInBits(Ty) && 113 "InsertNoopCastOfTo cannot change sizes!"); 114 return InsertCastOfTo(Op, V, Ty); 115} 116 117/// InsertBinop - Insert the specified binary operator, doing a small amount 118/// of work to avoid inserting an obviously redundant operation. 119Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, 120 Value *RHS, BasicBlock::iterator InsertPt) { 121 // Fold a binop with constant operands. 122 if (Constant *CLHS = dyn_cast<Constant>(LHS)) 123 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 124 return ConstantExpr::get(Opcode, CLHS, CRHS); 125 126 // Do a quick scan to see if we have this binop nearby. If so, reuse it. 127 unsigned ScanLimit = 6; 128 BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin(); 129 if (InsertPt != BlockBegin) { 130 // Scanning starts from the last instruction before InsertPt. 131 BasicBlock::iterator IP = InsertPt; 132 --IP; 133 for (; ScanLimit; --IP, --ScanLimit) { 134 if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS && 135 IP->getOperand(1) == RHS) 136 return IP; 137 if (IP == BlockBegin) break; 138 } 139 } 140 141 // If we haven't found this binop, insert it. 142 Instruction *BO = BinaryOperator::Create(Opcode, LHS, RHS, "tmp", InsertPt); 143 InsertedValues.insert(BO); 144 return BO; 145} 146 147/// FactorOutConstant - Test if S is evenly divisible by Factor, using signed 148/// division. If so, update S with Factor divided out and return true. 149/// TODO: When ScalarEvolution gets a SCEVSDivExpr, this can be made 150/// unnecessary; in its place, just signed-divide Ops[i] by the scale and 151/// check to see if the divide was folded. 152static bool FactorOutConstant(SCEVHandle &S, 153 const APInt &Factor, 154 ScalarEvolution &SE) { 155 // Everything is divisible by one. 156 if (Factor == 1) 157 return true; 158 159 // For a Constant, check for a multiple of the given factor. 160 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) 161 if (!C->getValue()->getValue().srem(Factor)) { 162 ConstantInt *CI = 163 ConstantInt::get(C->getValue()->getValue().sdiv(Factor)); 164 SCEVHandle Div = SE.getConstant(CI); 165 S = Div; 166 return true; 167 } 168 169 // In a Mul, check if there is a constant operand which is a multiple 170 // of the given factor. 171 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) 172 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0))) 173 if (!C->getValue()->getValue().srem(Factor)) { 174 std::vector<SCEVHandle> NewMulOps(M->getOperands()); 175 NewMulOps[0] = 176 SE.getConstant(C->getValue()->getValue().sdiv(Factor)); 177 S = SE.getMulExpr(NewMulOps); 178 return true; 179 } 180 181 // In an AddRec, check if both start and step are divisible. 182 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) { 183 SCEVHandle Start = A->getStart(); 184 if (!FactorOutConstant(Start, Factor, SE)) 185 return false; 186 SCEVHandle Step = A->getStepRecurrence(SE); 187 if (!FactorOutConstant(Step, Factor, SE)) 188 return false; 189 S = SE.getAddRecExpr(Start, Step, A->getLoop()); 190 return true; 191 } 192 193 return false; 194} 195 196/// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP 197/// instead of using ptrtoint+arithmetic+inttoptr. This helps 198/// BasicAliasAnalysis analyze the result. However, it suffers from the 199/// underlying bug described in PR2831. Addition in LLVM currently always 200/// has two's complement wrapping guaranteed. However, the semantics for 201/// getelementptr overflow are ambiguous. In the common case though, this 202/// expansion gets used when a GEP in the original code has been converted 203/// into integer arithmetic, in which case the resulting code will be no 204/// more undefined than it was originally. 205/// 206/// Design note: It might seem desirable for this function to be more 207/// loop-aware. If some of the indices are loop-invariant while others 208/// aren't, it might seem desirable to emit multiple GEPs, keeping the 209/// loop-invariant portions of the overall computation outside the loop. 210/// However, there are a few reasons this is not done here. Hoisting simple 211/// arithmetic is a low-level optimization that often isn't very 212/// important until late in the optimization process. In fact, passes 213/// like InstructionCombining will combine GEPs, even if it means 214/// pushing loop-invariant computation down into loops, so even if the 215/// GEPs were split here, the work would quickly be undone. The 216/// LoopStrengthReduction pass, which is usually run quite late (and 217/// after the last InstructionCombining pass), takes care of hoisting 218/// loop-invariant portions of expressions, after considering what 219/// can be folded using target addressing modes. 220/// 221Value *SCEVExpander::expandAddToGEP(const SCEVHandle *op_begin, 222 const SCEVHandle *op_end, 223 const PointerType *PTy, 224 const Type *Ty, 225 Value *V) { 226 const Type *ElTy = PTy->getElementType(); 227 SmallVector<Value *, 4> GepIndices; 228 std::vector<SCEVHandle> Ops(op_begin, op_end); 229 bool AnyNonZeroIndices = false; 230 231 // Decend down the pointer's type and attempt to convert the other 232 // operands into GEP indices, at each level. The first index in a GEP 233 // indexes into the array implied by the pointer operand; the rest of 234 // the indices index into the element or field type selected by the 235 // preceding index. 236 for (;;) { 237 APInt ElSize = APInt(SE.getTypeSizeInBits(Ty), 238 ElTy->isSized() ? SE.TD->getTypeAllocSize(ElTy) : 0); 239 std::vector<SCEVHandle> NewOps; 240 std::vector<SCEVHandle> ScaledOps; 241 for (unsigned i = 0, e = Ops.size(); i != e; ++i) { 242 // Split AddRecs up into parts as either of the parts may be usable 243 // without the other. 244 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i])) 245 if (!A->getStart()->isZero()) { 246 SCEVHandle Start = A->getStart(); 247 Ops.push_back(SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()), 248 A->getStepRecurrence(SE), 249 A->getLoop())); 250 Ops[i] = Start; 251 ++e; 252 } 253 // If the scale size is not 0, attempt to factor out a scale. 254 if (ElSize != 0) { 255 SCEVHandle Op = Ops[i]; 256 if (FactorOutConstant(Op, ElSize, SE)) { 257 ScaledOps.push_back(Op); // Op now has ElSize factored out. 258 continue; 259 } 260 } 261 // If the operand was not divisible, add it to the list of operands 262 // we'll scan next iteration. 263 NewOps.push_back(Ops[i]); 264 } 265 Ops = NewOps; 266 AnyNonZeroIndices |= !ScaledOps.empty(); 267 Value *Scaled = ScaledOps.empty() ? 268 Constant::getNullValue(Ty) : 269 expandCodeFor(SE.getAddExpr(ScaledOps), Ty); 270 GepIndices.push_back(Scaled); 271 272 // Collect struct field index operands. 273 if (!Ops.empty()) 274 while (const StructType *STy = dyn_cast<StructType>(ElTy)) { 275 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0])) 276 if (SE.getTypeSizeInBits(C->getType()) <= 64) { 277 const StructLayout &SL = *SE.TD->getStructLayout(STy); 278 uint64_t FullOffset = C->getValue()->getZExtValue(); 279 if (FullOffset < SL.getSizeInBytes()) { 280 unsigned ElIdx = SL.getElementContainingOffset(FullOffset); 281 GepIndices.push_back(ConstantInt::get(Type::Int32Ty, ElIdx)); 282 ElTy = STy->getTypeAtIndex(ElIdx); 283 Ops[0] = 284 SE.getConstant(ConstantInt::get(Ty, 285 FullOffset - 286 SL.getElementOffset(ElIdx))); 287 AnyNonZeroIndices = true; 288 continue; 289 } 290 } 291 break; 292 } 293 294 if (const ArrayType *ATy = dyn_cast<ArrayType>(ElTy)) { 295 ElTy = ATy->getElementType(); 296 continue; 297 } 298 break; 299 } 300 301 // If none of the operands were convertable to proper GEP indices, cast 302 // the base to i8* and do an ugly getelementptr with that. It's still 303 // better than ptrtoint+arithmetic+inttoptr at least. 304 if (!AnyNonZeroIndices) { 305 V = InsertNoopCastOfTo(V, 306 Type::Int8Ty->getPointerTo(PTy->getAddressSpace())); 307 Value *Idx = expand(SE.getAddExpr(Ops)); 308 Idx = InsertNoopCastOfTo(Idx, Ty); 309 310 // Fold a GEP with constant operands. 311 if (Constant *CLHS = dyn_cast<Constant>(V)) 312 if (Constant *CRHS = dyn_cast<Constant>(Idx)) 313 return ConstantExpr::getGetElementPtr(CLHS, &CRHS, 1); 314 315 // Do a quick scan to see if we have this GEP nearby. If so, reuse it. 316 unsigned ScanLimit = 6; 317 BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin(); 318 if (InsertPt != BlockBegin) { 319 // Scanning starts from the last instruction before InsertPt. 320 BasicBlock::iterator IP = InsertPt; 321 --IP; 322 for (; ScanLimit; --IP, --ScanLimit) { 323 if (IP->getOpcode() == Instruction::GetElementPtr && 324 IP->getOperand(0) == V && IP->getOperand(1) == Idx) 325 return IP; 326 if (IP == BlockBegin) break; 327 } 328 } 329 330 Value *GEP = GetElementPtrInst::Create(V, Idx, "scevgep", InsertPt); 331 InsertedValues.insert(GEP); 332 return GEP; 333 } 334 335 // Insert a pretty getelementptr. 336 Value *GEP = GetElementPtrInst::Create(V, 337 GepIndices.begin(), 338 GepIndices.end(), 339 "scevgep", InsertPt); 340 Ops.push_back(SE.getUnknown(GEP)); 341 InsertedValues.insert(GEP); 342 return expand(SE.getAddExpr(Ops)); 343} 344 345Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) { 346 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 347 Value *V = expand(S->getOperand(S->getNumOperands()-1)); 348 349 // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the 350 // comments on expandAddToGEP for details. 351 if (SE.TD) 352 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) { 353 const std::vector<SCEVHandle> &Ops = S->getOperands(); 354 return expandAddToGEP(&Ops[0], &Ops[Ops.size() - 1], 355 PTy, Ty, V); 356 } 357 358 V = InsertNoopCastOfTo(V, Ty); 359 360 // Emit a bunch of add instructions 361 for (int i = S->getNumOperands()-2; i >= 0; --i) { 362 Value *W = expand(S->getOperand(i)); 363 W = InsertNoopCastOfTo(W, Ty); 364 V = InsertBinop(Instruction::Add, V, W, InsertPt); 365 } 366 return V; 367} 368 369Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) { 370 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 371 int FirstOp = 0; // Set if we should emit a subtract. 372 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0))) 373 if (SC->getValue()->isAllOnesValue()) 374 FirstOp = 1; 375 376 int i = S->getNumOperands()-2; 377 Value *V = expand(S->getOperand(i+1)); 378 V = InsertNoopCastOfTo(V, Ty); 379 380 // Emit a bunch of multiply instructions 381 for (; i >= FirstOp; --i) { 382 Value *W = expand(S->getOperand(i)); 383 W = InsertNoopCastOfTo(W, Ty); 384 V = InsertBinop(Instruction::Mul, V, W, InsertPt); 385 } 386 387 // -1 * ... ---> 0 - ... 388 if (FirstOp == 1) 389 V = InsertBinop(Instruction::Sub, Constant::getNullValue(Ty), V, InsertPt); 390 return V; 391} 392 393Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) { 394 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 395 396 Value *LHS = expand(S->getLHS()); 397 LHS = InsertNoopCastOfTo(LHS, Ty); 398 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getRHS())) { 399 const APInt &RHS = SC->getValue()->getValue(); 400 if (RHS.isPowerOf2()) 401 return InsertBinop(Instruction::LShr, LHS, 402 ConstantInt::get(Ty, RHS.logBase2()), 403 InsertPt); 404 } 405 406 Value *RHS = expand(S->getRHS()); 407 RHS = InsertNoopCastOfTo(RHS, Ty); 408 return InsertBinop(Instruction::UDiv, LHS, RHS, InsertPt); 409} 410 411/// Move parts of Base into Rest to leave Base with the minimal 412/// expression that provides a pointer operand suitable for a 413/// GEP expansion. 414static void ExposePointerBase(SCEVHandle &Base, SCEVHandle &Rest, 415 ScalarEvolution &SE) { 416 while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) { 417 Base = A->getStart(); 418 Rest = SE.getAddExpr(Rest, 419 SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()), 420 A->getStepRecurrence(SE), 421 A->getLoop())); 422 } 423 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) { 424 Base = A->getOperand(A->getNumOperands()-1); 425 std::vector<SCEVHandle> NewAddOps(A->op_begin(), A->op_end()); 426 NewAddOps.back() = Rest; 427 Rest = SE.getAddExpr(NewAddOps); 428 ExposePointerBase(Base, Rest, SE); 429 } 430} 431 432Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) { 433 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 434 const Loop *L = S->getLoop(); 435 436 // {X,+,F} --> X + {0,+,F} 437 if (!S->getStart()->isZero()) { 438 std::vector<SCEVHandle> NewOps(S->getOperands()); 439 NewOps[0] = SE.getIntegerSCEV(0, Ty); 440 SCEVHandle Rest = SE.getAddRecExpr(NewOps, L); 441 442 // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the 443 // comments on expandAddToGEP for details. 444 if (SE.TD) { 445 SCEVHandle Base = S->getStart(); 446 SCEVHandle RestArray[1] = Rest; 447 // Dig into the expression to find the pointer base for a GEP. 448 ExposePointerBase(Base, RestArray[0], SE); 449 // If we found a pointer, expand the AddRec with a GEP. 450 if (const PointerType *PTy = dyn_cast<PointerType>(Base->getType())) { 451 Value *StartV = expand(Base); 452 assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!"); 453 return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV); 454 } 455 } 456 457 Value *RestV = expand(Rest); 458 return expand(SE.getAddExpr(S->getStart(), SE.getUnknown(RestV))); 459 } 460 461 // {0,+,1} --> Insert a canonical induction variable into the loop! 462 if (S->isAffine() && 463 S->getOperand(1) == SE.getIntegerSCEV(1, Ty)) { 464 // Create and insert the PHI node for the induction variable in the 465 // specified loop. 466 BasicBlock *Header = L->getHeader(); 467 PHINode *PN = PHINode::Create(Ty, "indvar", Header->begin()); 468 InsertedValues.insert(PN); 469 PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader()); 470 471 pred_iterator HPI = pred_begin(Header); 472 assert(HPI != pred_end(Header) && "Loop with zero preds???"); 473 if (!L->contains(*HPI)) ++HPI; 474 assert(HPI != pred_end(Header) && L->contains(*HPI) && 475 "No backedge in loop?"); 476 477 // Insert a unit add instruction right before the terminator corresponding 478 // to the back-edge. 479 Constant *One = ConstantInt::get(Ty, 1); 480 Instruction *Add = BinaryOperator::CreateAdd(PN, One, "indvar.next", 481 (*HPI)->getTerminator()); 482 InsertedValues.insert(Add); 483 484 pred_iterator PI = pred_begin(Header); 485 if (*PI == L->getLoopPreheader()) 486 ++PI; 487 PN->addIncoming(Add, *PI); 488 return PN; 489 } 490 491 // Get the canonical induction variable I for this loop. 492 Value *I = getOrInsertCanonicalInductionVariable(L, Ty); 493 494 // If this is a simple linear addrec, emit it now as a special case. 495 if (S->isAffine()) { // {0,+,F} --> i*F 496 Value *F = expand(S->getOperand(1)); 497 F = InsertNoopCastOfTo(F, Ty); 498 499 // IF the step is by one, just return the inserted IV. 500 if (ConstantInt *CI = dyn_cast<ConstantInt>(F)) 501 if (CI->getValue() == 1) 502 return I; 503 504 // If the insert point is directly inside of the loop, emit the multiply at 505 // the insert point. Otherwise, L is a loop that is a parent of the insert 506 // point loop. If we can, move the multiply to the outer most loop that it 507 // is safe to be in. 508 BasicBlock::iterator MulInsertPt = getInsertionPoint(); 509 Loop *InsertPtLoop = SE.LI->getLoopFor(MulInsertPt->getParent()); 510 if (InsertPtLoop != L && InsertPtLoop && 511 L->contains(InsertPtLoop->getHeader())) { 512 do { 513 // If we cannot hoist the multiply out of this loop, don't. 514 if (!InsertPtLoop->isLoopInvariant(F)) break; 515 516 BasicBlock *InsertPtLoopPH = InsertPtLoop->getLoopPreheader(); 517 518 // If this loop hasn't got a preheader, we aren't able to hoist the 519 // multiply. 520 if (!InsertPtLoopPH) 521 break; 522 523 // Otherwise, move the insert point to the preheader. 524 MulInsertPt = InsertPtLoopPH->getTerminator(); 525 InsertPtLoop = InsertPtLoop->getParentLoop(); 526 } while (InsertPtLoop != L); 527 } 528 529 return InsertBinop(Instruction::Mul, I, F, MulInsertPt); 530 } 531 532 // If this is a chain of recurrences, turn it into a closed form, using the 533 // folders, then expandCodeFor the closed form. This allows the folders to 534 // simplify the expression without having to build a bunch of special code 535 // into this folder. 536 SCEVHandle IH = SE.getUnknown(I); // Get I as a "symbolic" SCEV. 537 538 SCEVHandle V = S->evaluateAtIteration(IH, SE); 539 //cerr << "Evaluated: " << *this << "\n to: " << *V << "\n"; 540 541 return expand(V); 542} 543 544Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) { 545 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 546 Value *V = expand(S->getOperand()); 547 V = InsertNoopCastOfTo(V, SE.getEffectiveSCEVType(V->getType())); 548 Instruction *I = new TruncInst(V, Ty, "tmp.", InsertPt); 549 InsertedValues.insert(I); 550 return I; 551} 552 553Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) { 554 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 555 Value *V = expand(S->getOperand()); 556 V = InsertNoopCastOfTo(V, SE.getEffectiveSCEVType(V->getType())); 557 Instruction *I = new ZExtInst(V, Ty, "tmp.", InsertPt); 558 InsertedValues.insert(I); 559 return I; 560} 561 562Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) { 563 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 564 Value *V = expand(S->getOperand()); 565 V = InsertNoopCastOfTo(V, SE.getEffectiveSCEVType(V->getType())); 566 Instruction *I = new SExtInst(V, Ty, "tmp.", InsertPt); 567 InsertedValues.insert(I); 568 return I; 569} 570 571Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) { 572 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 573 Value *LHS = expand(S->getOperand(0)); 574 LHS = InsertNoopCastOfTo(LHS, Ty); 575 for (unsigned i = 1; i < S->getNumOperands(); ++i) { 576 Value *RHS = expand(S->getOperand(i)); 577 RHS = InsertNoopCastOfTo(RHS, Ty); 578 Instruction *ICmp = 579 new ICmpInst(ICmpInst::ICMP_SGT, LHS, RHS, "tmp", InsertPt); 580 InsertedValues.insert(ICmp); 581 Instruction *Sel = SelectInst::Create(ICmp, LHS, RHS, "smax", InsertPt); 582 InsertedValues.insert(Sel); 583 LHS = Sel; 584 } 585 return LHS; 586} 587 588Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) { 589 const Type *Ty = SE.getEffectiveSCEVType(S->getType()); 590 Value *LHS = expand(S->getOperand(0)); 591 LHS = InsertNoopCastOfTo(LHS, Ty); 592 for (unsigned i = 1; i < S->getNumOperands(); ++i) { 593 Value *RHS = expand(S->getOperand(i)); 594 RHS = InsertNoopCastOfTo(RHS, Ty); 595 Instruction *ICmp = 596 new ICmpInst(ICmpInst::ICMP_UGT, LHS, RHS, "tmp", InsertPt); 597 InsertedValues.insert(ICmp); 598 Instruction *Sel = SelectInst::Create(ICmp, LHS, RHS, "umax", InsertPt); 599 InsertedValues.insert(Sel); 600 LHS = Sel; 601 } 602 return LHS; 603} 604 605Value *SCEVExpander::expandCodeFor(SCEVHandle SH, const Type *Ty) { 606 // Expand the code for this SCEV. 607 Value *V = expand(SH); 608 if (Ty) { 609 assert(SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(SH->getType()) && 610 "non-trivial casts should be done with the SCEVs directly!"); 611 V = InsertNoopCastOfTo(V, Ty); 612 } 613 return V; 614} 615 616Value *SCEVExpander::expand(const SCEV *S) { 617 // Check to see if we already expanded this. 618 std::map<SCEVHandle, AssertingVH<Value> >::iterator I = InsertedExpressions.find(S); 619 if (I != InsertedExpressions.end()) 620 return I->second; 621 622 Value *V = visit(S); 623 InsertedExpressions[S] = V; 624 return V; 625} 626