| //===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file contains the implementation of the scalar evolution expander, |
| // which is used to generate the code corresponding to a given scalar evolution |
| // expression. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Analysis/ScalarEvolutionExpander.h" |
| #include "llvm/Analysis/LoopInfo.h" |
| #include "llvm/LLVMContext.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/ADT/STLExtras.h" |
| using namespace llvm; |
| |
| /// InsertNoopCastOfTo - Insert a cast of V to the specified type, |
| /// which must be possible with a noop cast, doing what we can to share |
| /// the casts. |
| Value *SCEVExpander::InsertNoopCastOfTo(Value *V, const Type *Ty) { |
| Instruction::CastOps Op = CastInst::getCastOpcode(V, false, Ty, false); |
| assert((Op == Instruction::BitCast || |
| Op == Instruction::PtrToInt || |
| Op == Instruction::IntToPtr) && |
| "InsertNoopCastOfTo cannot perform non-noop casts!"); |
| assert(SE.getTypeSizeInBits(V->getType()) == SE.getTypeSizeInBits(Ty) && |
| "InsertNoopCastOfTo cannot change sizes!"); |
| |
| // Short-circuit unnecessary bitcasts. |
| if (Op == Instruction::BitCast && V->getType() == Ty) |
| return V; |
| |
| // Short-circuit unnecessary inttoptr<->ptrtoint casts. |
| if ((Op == Instruction::PtrToInt || Op == Instruction::IntToPtr) && |
| SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) { |
| if (CastInst *CI = dyn_cast<CastInst>(V)) |
| if ((CI->getOpcode() == Instruction::PtrToInt || |
| CI->getOpcode() == Instruction::IntToPtr) && |
| SE.getTypeSizeInBits(CI->getType()) == |
| SE.getTypeSizeInBits(CI->getOperand(0)->getType())) |
| return CI->getOperand(0); |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) |
| if ((CE->getOpcode() == Instruction::PtrToInt || |
| CE->getOpcode() == Instruction::IntToPtr) && |
| SE.getTypeSizeInBits(CE->getType()) == |
| SE.getTypeSizeInBits(CE->getOperand(0)->getType())) |
| return CE->getOperand(0); |
| } |
| |
| // FIXME: keep track of the cast instruction. |
| if (Constant *C = dyn_cast<Constant>(V)) |
| return ConstantExpr::getCast(Op, C, Ty); |
| |
| if (Argument *A = dyn_cast<Argument>(V)) { |
| // Check to see if there is already a cast! |
| for (Value::use_iterator UI = A->use_begin(), E = A->use_end(); |
| UI != E; ++UI) |
| if ((*UI)->getType() == Ty) |
| if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) |
| if (CI->getOpcode() == Op) { |
| // If the cast isn't the first instruction of the function, move it. |
| if (BasicBlock::iterator(CI) != |
| A->getParent()->getEntryBlock().begin()) { |
| // Recreate the cast at the beginning of the entry block. |
| // The old cast is left in place in case it is being used |
| // as an insert point. |
| Instruction *NewCI = |
| CastInst::Create(Op, V, Ty, "", |
| A->getParent()->getEntryBlock().begin()); |
| NewCI->takeName(CI); |
| CI->replaceAllUsesWith(NewCI); |
| return NewCI; |
| } |
| return CI; |
| } |
| |
| Instruction *I = CastInst::Create(Op, V, Ty, V->getName(), |
| A->getParent()->getEntryBlock().begin()); |
| InsertedValues.insert(I); |
| return I; |
| } |
| |
| Instruction *I = cast<Instruction>(V); |
| |
| // Check to see if there is already a cast. If there is, use it. |
| for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); |
| UI != E; ++UI) { |
| if ((*UI)->getType() == Ty) |
| if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) |
| if (CI->getOpcode() == Op) { |
| BasicBlock::iterator It = I; ++It; |
| if (isa<InvokeInst>(I)) |
| It = cast<InvokeInst>(I)->getNormalDest()->begin(); |
| while (isa<PHINode>(It)) ++It; |
| if (It != BasicBlock::iterator(CI)) { |
| // Recreate the cast at the beginning of the entry block. |
| // The old cast is left in place in case it is being used |
| // as an insert point. |
| Instruction *NewCI = CastInst::Create(Op, V, Ty, "", It); |
| NewCI->takeName(CI); |
| CI->replaceAllUsesWith(NewCI); |
| return NewCI; |
| } |
| return CI; |
| } |
| } |
| BasicBlock::iterator IP = I; ++IP; |
| if (InvokeInst *II = dyn_cast<InvokeInst>(I)) |
| IP = II->getNormalDest()->begin(); |
| while (isa<PHINode>(IP)) ++IP; |
| Instruction *CI = CastInst::Create(Op, V, Ty, V->getName(), IP); |
| InsertedValues.insert(CI); |
| return CI; |
| } |
| |
| /// InsertBinop - Insert the specified binary operator, doing a small amount |
| /// of work to avoid inserting an obviously redundant operation. |
| Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, |
| Value *LHS, Value *RHS) { |
| // Fold a binop with constant operands. |
| if (Constant *CLHS = dyn_cast<Constant>(LHS)) |
| if (Constant *CRHS = dyn_cast<Constant>(RHS)) |
| return ConstantExpr::get(Opcode, CLHS, CRHS); |
| |
| // Do a quick scan to see if we have this binop nearby. If so, reuse it. |
| unsigned ScanLimit = 6; |
| BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin(); |
| // Scanning starts from the last instruction before the insertion point. |
| BasicBlock::iterator IP = Builder.GetInsertPoint(); |
| if (IP != BlockBegin) { |
| --IP; |
| for (; ScanLimit; --IP, --ScanLimit) { |
| if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS && |
| IP->getOperand(1) == RHS) |
| return IP; |
| if (IP == BlockBegin) break; |
| } |
| } |
| |
| // If we haven't found this binop, insert it. |
| Value *BO = Builder.CreateBinOp(Opcode, LHS, RHS, "tmp"); |
| InsertedValues.insert(BO); |
| return BO; |
| } |
| |
| /// FactorOutConstant - Test if S is divisible by Factor, using signed |
| /// division. If so, update S with Factor divided out and return true. |
| /// S need not be evenly divisble if a reasonable remainder can be |
| /// computed. |
| /// TODO: When ScalarEvolution gets a SCEVSDivExpr, this can be made |
| /// unnecessary; in its place, just signed-divide Ops[i] by the scale and |
| /// check to see if the divide was folded. |
| static bool FactorOutConstant(const SCEV *&S, |
| const SCEV *&Remainder, |
| const APInt &Factor, |
| ScalarEvolution &SE) { |
| // Everything is divisible by one. |
| if (Factor == 1) |
| return true; |
| |
| // For a Constant, check for a multiple of the given factor. |
| if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) { |
| ConstantInt *CI = |
| ConstantInt::get(SE.getContext(), C->getValue()->getValue().sdiv(Factor)); |
| // If the quotient is zero and the remainder is non-zero, reject |
| // the value at this scale. It will be considered for subsequent |
| // smaller scales. |
| if (C->isZero() || !CI->isZero()) { |
| const SCEV *Div = SE.getConstant(CI); |
| S = Div; |
| Remainder = |
| SE.getAddExpr(Remainder, |
| SE.getConstant(C->getValue()->getValue().srem(Factor))); |
| return true; |
| } |
| } |
| |
| // In a Mul, check if there is a constant operand which is a multiple |
| // of the given factor. |
| if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) |
| if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0))) |
| if (!C->getValue()->getValue().srem(Factor)) { |
| const SmallVectorImpl<const SCEV *> &MOperands = M->getOperands(); |
| SmallVector<const SCEV *, 4> NewMulOps(MOperands.begin(), |
| MOperands.end()); |
| NewMulOps[0] = |
| SE.getConstant(C->getValue()->getValue().sdiv(Factor)); |
| S = SE.getMulExpr(NewMulOps); |
| return true; |
| } |
| |
| // In an AddRec, check if both start and step are divisible. |
| if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) { |
| const SCEV *Step = A->getStepRecurrence(SE); |
| const SCEV *StepRem = SE.getIntegerSCEV(0, Step->getType()); |
| if (!FactorOutConstant(Step, StepRem, Factor, SE)) |
| return false; |
| if (!StepRem->isZero()) |
| return false; |
| const SCEV *Start = A->getStart(); |
| if (!FactorOutConstant(Start, Remainder, Factor, SE)) |
| return false; |
| S = SE.getAddRecExpr(Start, Step, A->getLoop()); |
| return true; |
| } |
| |
| return false; |
| } |
| |
| /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP |
| /// instead of using ptrtoint+arithmetic+inttoptr. This helps |
| /// BasicAliasAnalysis analyze the result. |
| /// |
| /// Design note: This depends on ScalarEvolution not recognizing inttoptr |
| /// and ptrtoint operators, as they may introduce pointer arithmetic |
| /// which may not be safely converted into getelementptr. |
| /// |
| /// Design note: It might seem desirable for this function to be more |
| /// loop-aware. If some of the indices are loop-invariant while others |
| /// aren't, it might seem desirable to emit multiple GEPs, keeping the |
| /// loop-invariant portions of the overall computation outside the loop. |
| /// However, there are a few reasons this is not done here. Hoisting simple |
| /// arithmetic is a low-level optimization that often isn't very |
| /// important until late in the optimization process. In fact, passes |
| /// like InstructionCombining will combine GEPs, even if it means |
| /// pushing loop-invariant computation down into loops, so even if the |
| /// GEPs were split here, the work would quickly be undone. The |
| /// LoopStrengthReduction pass, which is usually run quite late (and |
| /// after the last InstructionCombining pass), takes care of hoisting |
| /// loop-invariant portions of expressions, after considering what |
| /// can be folded using target addressing modes. |
| /// |
| Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin, |
| const SCEV *const *op_end, |
| const PointerType *PTy, |
| const Type *Ty, |
| Value *V) { |
| const Type *ElTy = PTy->getElementType(); |
| SmallVector<Value *, 4> GepIndices; |
| SmallVector<const SCEV *, 8> Ops(op_begin, op_end); |
| bool AnyNonZeroIndices = false; |
| |
| // Decend down the pointer's type and attempt to convert the other |
| // operands into GEP indices, at each level. The first index in a GEP |
| // indexes into the array implied by the pointer operand; the rest of |
| // the indices index into the element or field type selected by the |
| // preceding index. |
| for (;;) { |
| APInt ElSize = APInt(SE.getTypeSizeInBits(Ty), |
| ElTy->isSized() ? SE.TD->getTypeAllocSize(ElTy) : 0); |
| SmallVector<const SCEV *, 8> NewOps; |
| SmallVector<const SCEV *, 8> ScaledOps; |
| for (unsigned i = 0, e = Ops.size(); i != e; ++i) { |
| // Split AddRecs up into parts as either of the parts may be usable |
| // without the other. |
| if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i])) |
| if (!A->getStart()->isZero()) { |
| const SCEV *Start = A->getStart(); |
| Ops.push_back(SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()), |
| A->getStepRecurrence(SE), |
| A->getLoop())); |
| Ops[i] = Start; |
| ++e; |
| } |
| // If the scale size is not 0, attempt to factor out a scale. |
| if (ElSize != 0) { |
| const SCEV *Op = Ops[i]; |
| const SCEV *Remainder = SE.getIntegerSCEV(0, Op->getType()); |
| if (FactorOutConstant(Op, Remainder, ElSize, SE)) { |
| ScaledOps.push_back(Op); // Op now has ElSize factored out. |
| NewOps.push_back(Remainder); |
| continue; |
| } |
| } |
| // If the operand was not divisible, add it to the list of operands |
| // we'll scan next iteration. |
| NewOps.push_back(Ops[i]); |
| } |
| Ops = NewOps; |
| AnyNonZeroIndices |= !ScaledOps.empty(); |
| Value *Scaled = ScaledOps.empty() ? |
| getContext().getNullValue(Ty) : |
| expandCodeFor(SE.getAddExpr(ScaledOps), Ty); |
| GepIndices.push_back(Scaled); |
| |
| // Collect struct field index operands. |
| if (!Ops.empty()) |
| while (const StructType *STy = dyn_cast<StructType>(ElTy)) { |
| if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0])) |
| if (SE.getTypeSizeInBits(C->getType()) <= 64) { |
| const StructLayout &SL = *SE.TD->getStructLayout(STy); |
| uint64_t FullOffset = C->getValue()->getZExtValue(); |
| if (FullOffset < SL.getSizeInBytes()) { |
| unsigned ElIdx = SL.getElementContainingOffset(FullOffset); |
| GepIndices.push_back(ConstantInt::get(Type::Int32Ty, ElIdx)); |
| ElTy = STy->getTypeAtIndex(ElIdx); |
| Ops[0] = |
| SE.getConstant(Ty, FullOffset - SL.getElementOffset(ElIdx)); |
| AnyNonZeroIndices = true; |
| continue; |
| } |
| } |
| break; |
| } |
| |
| if (const ArrayType *ATy = dyn_cast<ArrayType>(ElTy)) { |
| ElTy = ATy->getElementType(); |
| continue; |
| } |
| break; |
| } |
| |
| // If none of the operands were convertable to proper GEP indices, cast |
| // the base to i8* and do an ugly getelementptr with that. It's still |
| // better than ptrtoint+arithmetic+inttoptr at least. |
| if (!AnyNonZeroIndices) { |
| V = InsertNoopCastOfTo(V, |
| Type::Int8Ty->getPointerTo(PTy->getAddressSpace())); |
| Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty); |
| |
| // Fold a GEP with constant operands. |
| if (Constant *CLHS = dyn_cast<Constant>(V)) |
| if (Constant *CRHS = dyn_cast<Constant>(Idx)) |
| return ConstantExpr::getGetElementPtr(CLHS, &CRHS, 1); |
| |
| // Do a quick scan to see if we have this GEP nearby. If so, reuse it. |
| unsigned ScanLimit = 6; |
| BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin(); |
| // Scanning starts from the last instruction before the insertion point. |
| BasicBlock::iterator IP = Builder.GetInsertPoint(); |
| if (IP != BlockBegin) { |
| --IP; |
| for (; ScanLimit; --IP, --ScanLimit) { |
| if (IP->getOpcode() == Instruction::GetElementPtr && |
| IP->getOperand(0) == V && IP->getOperand(1) == Idx) |
| return IP; |
| if (IP == BlockBegin) break; |
| } |
| } |
| |
| Value *GEP = Builder.CreateGEP(V, Idx, "scevgep"); |
| InsertedValues.insert(GEP); |
| return GEP; |
| } |
| |
| // Insert a pretty getelementptr. Note that this GEP is not marked inbounds, |
| // because ScalarEvolution may have changed the address arithmetic to |
| // compute a value which is beyond the end of the allocated object. |
| Value *GEP = Builder.CreateGEP(V, |
| GepIndices.begin(), |
| GepIndices.end(), |
| "scevgep"); |
| Ops.push_back(SE.getUnknown(GEP)); |
| InsertedValues.insert(GEP); |
| return expand(SE.getAddExpr(Ops)); |
| } |
| |
| Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) { |
| const Type *Ty = SE.getEffectiveSCEVType(S->getType()); |
| Value *V = expand(S->getOperand(S->getNumOperands()-1)); |
| |
| // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the |
| // comments on expandAddToGEP for details. |
| if (SE.TD) |
| if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) { |
| const SmallVectorImpl<const SCEV *> &Ops = S->getOperands(); |
| return expandAddToGEP(&Ops[0], &Ops[Ops.size() - 1], PTy, Ty, V); |
| } |
| |
| V = InsertNoopCastOfTo(V, Ty); |
| |
| // Emit a bunch of add instructions |
| for (int i = S->getNumOperands()-2; i >= 0; --i) { |
| Value *W = expandCodeFor(S->getOperand(i), Ty); |
| V = InsertBinop(Instruction::Add, V, W); |
| } |
| return V; |
| } |
| |
| Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) { |
| const Type *Ty = SE.getEffectiveSCEVType(S->getType()); |
| int FirstOp = 0; // Set if we should emit a subtract. |
| if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0))) |
| if (SC->getValue()->isAllOnesValue()) |
| FirstOp = 1; |
| |
| int i = S->getNumOperands()-2; |
| Value *V = expandCodeFor(S->getOperand(i+1), Ty); |
| |
| // Emit a bunch of multiply instructions |
| for (; i >= FirstOp; --i) { |
| Value *W = expandCodeFor(S->getOperand(i), Ty); |
| V = InsertBinop(Instruction::Mul, V, W); |
| } |
| |
| // -1 * ... ---> 0 - ... |
| if (FirstOp == 1) |
| V = InsertBinop(Instruction::Sub, getContext().getNullValue(Ty), V); |
| return V; |
| } |
| |
| Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) { |
| const Type *Ty = SE.getEffectiveSCEVType(S->getType()); |
| |
| Value *LHS = expandCodeFor(S->getLHS(), Ty); |
| if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getRHS())) { |
| const APInt &RHS = SC->getValue()->getValue(); |
| if (RHS.isPowerOf2()) |
| return InsertBinop(Instruction::LShr, LHS, |
| ConstantInt::get(Ty, RHS.logBase2())); |
| } |
| |
| Value *RHS = expandCodeFor(S->getRHS(), Ty); |
| return InsertBinop(Instruction::UDiv, LHS, RHS); |
| } |
| |
| /// Move parts of Base into Rest to leave Base with the minimal |
| /// expression that provides a pointer operand suitable for a |
| /// GEP expansion. |
| static void ExposePointerBase(const SCEV *&Base, const SCEV *&Rest, |
| ScalarEvolution &SE) { |
| while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) { |
| Base = A->getStart(); |
| Rest = SE.getAddExpr(Rest, |
| SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()), |
| A->getStepRecurrence(SE), |
| A->getLoop())); |
| } |
| if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) { |
| Base = A->getOperand(A->getNumOperands()-1); |
| SmallVector<const SCEV *, 8> NewAddOps(A->op_begin(), A->op_end()); |
| NewAddOps.back() = Rest; |
| Rest = SE.getAddExpr(NewAddOps); |
| ExposePointerBase(Base, Rest, SE); |
| } |
| } |
| |
| Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) { |
| const Type *Ty = SE.getEffectiveSCEVType(S->getType()); |
| const Loop *L = S->getLoop(); |
| |
| // First check for an existing canonical IV in a suitable type. |
| PHINode *CanonicalIV = 0; |
| if (PHINode *PN = L->getCanonicalInductionVariable()) |
| if (SE.isSCEVable(PN->getType()) && |
| isa<IntegerType>(SE.getEffectiveSCEVType(PN->getType())) && |
| SE.getTypeSizeInBits(PN->getType()) >= SE.getTypeSizeInBits(Ty)) |
| CanonicalIV = PN; |
| |
| // Rewrite an AddRec in terms of the canonical induction variable, if |
| // its type is more narrow. |
| if (CanonicalIV && |
| SE.getTypeSizeInBits(CanonicalIV->getType()) > |
| SE.getTypeSizeInBits(Ty)) { |
| const SCEV *Start = SE.getAnyExtendExpr(S->getStart(), |
| CanonicalIV->getType()); |
| const SCEV *Step = SE.getAnyExtendExpr(S->getStepRecurrence(SE), |
| CanonicalIV->getType()); |
| Value *V = expand(SE.getAddRecExpr(Start, Step, S->getLoop())); |
| BasicBlock *SaveInsertBB = Builder.GetInsertBlock(); |
| BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint(); |
| BasicBlock::iterator NewInsertPt = |
| next(BasicBlock::iterator(cast<Instruction>(V))); |
| while (isa<PHINode>(NewInsertPt)) ++NewInsertPt; |
| V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), 0, |
| NewInsertPt); |
| Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt); |
| return V; |
| } |
| |
| // {X,+,F} --> X + {0,+,F} |
| if (!S->getStart()->isZero()) { |
| const SmallVectorImpl<const SCEV *> &SOperands = S->getOperands(); |
| SmallVector<const SCEV *, 4> NewOps(SOperands.begin(), SOperands.end()); |
| NewOps[0] = SE.getIntegerSCEV(0, Ty); |
| const SCEV *Rest = SE.getAddRecExpr(NewOps, L); |
| |
| // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the |
| // comments on expandAddToGEP for details. |
| if (SE.TD) { |
| const SCEV *Base = S->getStart(); |
| const SCEV *RestArray[1] = { Rest }; |
| // Dig into the expression to find the pointer base for a GEP. |
| ExposePointerBase(Base, RestArray[0], SE); |
| // If we found a pointer, expand the AddRec with a GEP. |
| if (const PointerType *PTy = dyn_cast<PointerType>(Base->getType())) { |
| // Make sure the Base isn't something exotic, such as a multiplied |
| // or divided pointer value. In those cases, the result type isn't |
| // actually a pointer type. |
| if (!isa<SCEVMulExpr>(Base) && !isa<SCEVUDivExpr>(Base)) { |
| Value *StartV = expand(Base); |
| assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!"); |
| return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV); |
| } |
| } |
| } |
| |
| // Just do a normal add. Pre-expand the operands to suppress folding. |
| return expand(SE.getAddExpr(SE.getUnknown(expand(S->getStart())), |
| SE.getUnknown(expand(Rest)))); |
| } |
| |
| // {0,+,1} --> Insert a canonical induction variable into the loop! |
| if (S->isAffine() && |
| S->getOperand(1) == SE.getIntegerSCEV(1, Ty)) { |
| // If there's a canonical IV, just use it. |
| if (CanonicalIV) { |
| assert(Ty == SE.getEffectiveSCEVType(CanonicalIV->getType()) && |
| "IVs with types different from the canonical IV should " |
| "already have been handled!"); |
| return CanonicalIV; |
| } |
| |
| // Create and insert the PHI node for the induction variable in the |
| // specified loop. |
| BasicBlock *Header = L->getHeader(); |
| BasicBlock *Preheader = L->getLoopPreheader(); |
| PHINode *PN = PHINode::Create(Ty, "indvar", Header->begin()); |
| InsertedValues.insert(PN); |
| PN->addIncoming(getContext().getNullValue(Ty), Preheader); |
| |
| pred_iterator HPI = pred_begin(Header); |
| assert(HPI != pred_end(Header) && "Loop with zero preds???"); |
| if (!L->contains(*HPI)) ++HPI; |
| assert(HPI != pred_end(Header) && L->contains(*HPI) && |
| "No backedge in loop?"); |
| |
| // Insert a unit add instruction right before the terminator corresponding |
| // to the back-edge. |
| Constant *One = ConstantInt::get(Ty, 1); |
| Instruction *Add = BinaryOperator::CreateAdd(PN, One, "indvar.next", |
| (*HPI)->getTerminator()); |
| InsertedValues.insert(Add); |
| |
| pred_iterator PI = pred_begin(Header); |
| if (*PI == Preheader) |
| ++PI; |
| PN->addIncoming(Add, *PI); |
| return PN; |
| } |
| |
| // {0,+,F} --> {0,+,1} * F |
| // Get the canonical induction variable I for this loop. |
| Value *I = CanonicalIV ? |
| CanonicalIV : |
| getOrInsertCanonicalInductionVariable(L, Ty); |
| |
| // If this is a simple linear addrec, emit it now as a special case. |
| if (S->isAffine()) // {0,+,F} --> i*F |
| return |
| expand(SE.getTruncateOrNoop( |
| SE.getMulExpr(SE.getUnknown(I), |
| SE.getNoopOrAnyExtend(S->getOperand(1), |
| I->getType())), |
| Ty)); |
| |
| // If this is a chain of recurrences, turn it into a closed form, using the |
| // folders, then expandCodeFor the closed form. This allows the folders to |
| // simplify the expression without having to build a bunch of special code |
| // into this folder. |
| const SCEV *IH = SE.getUnknown(I); // Get I as a "symbolic" SCEV. |
| |
| // Promote S up to the canonical IV type, if the cast is foldable. |
| const SCEV *NewS = S; |
| const SCEV *Ext = SE.getNoopOrAnyExtend(S, I->getType()); |
| if (isa<SCEVAddRecExpr>(Ext)) |
| NewS = Ext; |
| |
| const SCEV *V = cast<SCEVAddRecExpr>(NewS)->evaluateAtIteration(IH, SE); |
| //cerr << "Evaluated: " << *this << "\n to: " << *V << "\n"; |
| |
| // Truncate the result down to the original type, if needed. |
| const SCEV *T = SE.getTruncateOrNoop(V, Ty); |
| return expand(T); |
| } |
| |
| Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) { |
| const Type *Ty = SE.getEffectiveSCEVType(S->getType()); |
| Value *V = expandCodeFor(S->getOperand(), |
| SE.getEffectiveSCEVType(S->getOperand()->getType())); |
| Value *I = Builder.CreateTrunc(V, Ty, "tmp"); |
| InsertedValues.insert(I); |
| return I; |
| } |
| |
| Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) { |
| const Type *Ty = SE.getEffectiveSCEVType(S->getType()); |
| Value *V = expandCodeFor(S->getOperand(), |
| SE.getEffectiveSCEVType(S->getOperand()->getType())); |
| Value *I = Builder.CreateZExt(V, Ty, "tmp"); |
| InsertedValues.insert(I); |
| return I; |
| } |
| |
| Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) { |
| const Type *Ty = SE.getEffectiveSCEVType(S->getType()); |
| Value *V = expandCodeFor(S->getOperand(), |
| SE.getEffectiveSCEVType(S->getOperand()->getType())); |
| Value *I = Builder.CreateSExt(V, Ty, "tmp"); |
| InsertedValues.insert(I); |
| return I; |
| } |
| |
| Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) { |
| Value *LHS = expand(S->getOperand(S->getNumOperands()-1)); |
| const Type *Ty = LHS->getType(); |
| for (int i = S->getNumOperands()-2; i >= 0; --i) { |
| // In the case of mixed integer and pointer types, do the |
| // rest of the comparisons as integer. |
| if (S->getOperand(i)->getType() != Ty) { |
| Ty = SE.getEffectiveSCEVType(Ty); |
| LHS = InsertNoopCastOfTo(LHS, Ty); |
| } |
| Value *RHS = expandCodeFor(S->getOperand(i), Ty); |
| Value *ICmp = Builder.CreateICmpSGT(LHS, RHS, "tmp"); |
| InsertedValues.insert(ICmp); |
| Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "smax"); |
| InsertedValues.insert(Sel); |
| LHS = Sel; |
| } |
| // In the case of mixed integer and pointer types, cast the |
| // final result back to the pointer type. |
| if (LHS->getType() != S->getType()) |
| LHS = InsertNoopCastOfTo(LHS, S->getType()); |
| return LHS; |
| } |
| |
| Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) { |
| Value *LHS = expand(S->getOperand(S->getNumOperands()-1)); |
| const Type *Ty = LHS->getType(); |
| for (int i = S->getNumOperands()-2; i >= 0; --i) { |
| // In the case of mixed integer and pointer types, do the |
| // rest of the comparisons as integer. |
| if (S->getOperand(i)->getType() != Ty) { |
| Ty = SE.getEffectiveSCEVType(Ty); |
| LHS = InsertNoopCastOfTo(LHS, Ty); |
| } |
| Value *RHS = expandCodeFor(S->getOperand(i), Ty); |
| Value *ICmp = Builder.CreateICmpUGT(LHS, RHS, "tmp"); |
| InsertedValues.insert(ICmp); |
| Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "umax"); |
| InsertedValues.insert(Sel); |
| LHS = Sel; |
| } |
| // In the case of mixed integer and pointer types, cast the |
| // final result back to the pointer type. |
| if (LHS->getType() != S->getType()) |
| LHS = InsertNoopCastOfTo(LHS, S->getType()); |
| return LHS; |
| } |
| |
| Value *SCEVExpander::expandCodeFor(const SCEV *SH, const Type *Ty) { |
| // Expand the code for this SCEV. |
| Value *V = expand(SH); |
| if (Ty) { |
| assert(SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(SH->getType()) && |
| "non-trivial casts should be done with the SCEVs directly!"); |
| V = InsertNoopCastOfTo(V, Ty); |
| } |
| return V; |
| } |
| |
| Value *SCEVExpander::expand(const SCEV *S) { |
| // Compute an insertion point for this SCEV object. Hoist the instructions |
| // as far out in the loop nest as possible. |
| Instruction *InsertPt = Builder.GetInsertPoint(); |
| for (Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock()); ; |
| L = L->getParentLoop()) |
| if (S->isLoopInvariant(L)) { |
| if (!L) break; |
| if (BasicBlock *Preheader = L->getLoopPreheader()) |
| InsertPt = Preheader->getTerminator(); |
| } else { |
| // If the SCEV is computable at this level, insert it into the header |
| // after the PHIs (and after any other instructions that we've inserted |
| // there) so that it is guaranteed to dominate any user inside the loop. |
| if (L && S->hasComputableLoopEvolution(L)) |
| InsertPt = L->getHeader()->getFirstNonPHI(); |
| while (isInsertedInstruction(InsertPt)) |
| InsertPt = next(BasicBlock::iterator(InsertPt)); |
| break; |
| } |
| |
| // Check to see if we already expanded this here. |
| std::map<std::pair<const SCEV *, Instruction *>, |
| AssertingVH<Value> >::iterator I = |
| InsertedExpressions.find(std::make_pair(S, InsertPt)); |
| if (I != InsertedExpressions.end()) |
| return I->second; |
| |
| BasicBlock *SaveInsertBB = Builder.GetInsertBlock(); |
| BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint(); |
| Builder.SetInsertPoint(InsertPt->getParent(), InsertPt); |
| |
| // Expand the expression into instructions. |
| Value *V = visit(S); |
| |
| // Remember the expanded value for this SCEV at this location. |
| InsertedExpressions[std::make_pair(S, InsertPt)] = V; |
| |
| Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt); |
| return V; |
| } |
| |
| /// getOrInsertCanonicalInductionVariable - This method returns the |
| /// canonical induction variable of the specified type for the specified |
| /// loop (inserting one if there is none). A canonical induction variable |
| /// starts at zero and steps by one on each iteration. |
| Value * |
| SCEVExpander::getOrInsertCanonicalInductionVariable(const Loop *L, |
| const Type *Ty) { |
| assert(Ty->isInteger() && "Can only insert integer induction variables!"); |
| const SCEV *H = SE.getAddRecExpr(SE.getIntegerSCEV(0, Ty), |
| SE.getIntegerSCEV(1, Ty), L); |
| BasicBlock *SaveInsertBB = Builder.GetInsertBlock(); |
| BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint(); |
| Value *V = expandCodeFor(H, 0, L->getHeader()->begin()); |
| if (SaveInsertBB) |
| Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt); |
| return V; |
| } |