//===- 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(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(V)) if ((CE->getOpcode() == Instruction::PtrToInt || CE->getOpcode() == Instruction::IntToPtr) && SE.getTypeSizeInBits(CE->getType()) == SE.getTypeSizeInBits(CE->getOperand(0)->getType())) return CE->getOperand(0); } if (Constant *C = dyn_cast(V)) return ConstantExpr::getCast(Op, C, Ty); if (Argument *A = dyn_cast(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(cast(*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(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(cast(*UI))) if (CI->getOpcode() == Op) { BasicBlock::iterator It = I; ++It; if (isa(I)) It = cast(I)->getNormalDest()->begin(); while (isa(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(I)) IP = II->getNormalDest()->begin(); while (isa(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(LHS)) if (Constant *CRHS = dyn_cast(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 SCEV *Factor, ScalarEvolution &SE, const TargetData *TD) { // Everything is divisible by one. if (Factor->isOne()) return true; // x/x == 1. if (S == Factor) { S = SE.getIntegerSCEV(1, S->getType()); return true; } // For a Constant, check for a multiple of the given factor. if (const SCEVConstant *C = dyn_cast(S)) { // 0/x == 0. if (C->isZero()) return true; // Check for divisibility. if (const SCEVConstant *FC = dyn_cast(Factor)) { ConstantInt *CI = ConstantInt::get(SE.getContext(), C->getValue()->getValue().sdiv( FC->getValue()->getValue())); // 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 (!CI->isZero()) { const SCEV *Div = SE.getConstant(CI); S = Div; Remainder = SE.getAddExpr(Remainder, SE.getConstant(C->getValue()->getValue().srem( FC->getValue()->getValue()))); 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(S)) { if (TD) { // With TargetData, the size is known. Check if there is a constant // operand which is a multiple of the given factor. If so, we can // factor it. const SCEVConstant *FC = cast(Factor); if (const SCEVConstant *C = dyn_cast(M->getOperand(0))) if (!C->getValue()->getValue().srem(FC->getValue()->getValue())) { const SmallVectorImpl &MOperands = M->getOperands(); SmallVector NewMulOps(MOperands.begin(), MOperands.end()); NewMulOps[0] = SE.getConstant(C->getValue()->getValue().sdiv( FC->getValue()->getValue())); S = SE.getMulExpr(NewMulOps); return true; } } else { // Without TargetData, check if Factor can be factored out of any of the // Mul's operands. If so, we can just remove it. for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) { const SCEV *SOp = M->getOperand(i); const SCEV *Remainder = SE.getIntegerSCEV(0, SOp->getType()); if (FactorOutConstant(SOp, Remainder, Factor, SE, TD) && Remainder->isZero()) { const SmallVectorImpl &MOperands = M->getOperands(); SmallVector NewMulOps(MOperands.begin(), MOperands.end()); NewMulOps[i] = SOp; S = SE.getMulExpr(NewMulOps); return true; } } } } // In an AddRec, check if both start and step are divisible. if (const SCEVAddRecExpr *A = dyn_cast(S)) { const SCEV *Step = A->getStepRecurrence(SE); const SCEV *StepRem = SE.getIntegerSCEV(0, Step->getType()); if (!FactorOutConstant(Step, StepRem, Factor, SE, TD)) return false; if (!StepRem->isZero()) return false; const SCEV *Start = A->getStart(); if (!FactorOutConstant(Start, Remainder, Factor, SE, TD)) return false; S = SE.getAddRecExpr(Start, Step, A->getLoop()); return true; } return false; } /// SimplifyAddOperands - Sort and simplify a list of add operands. NumAddRecs /// is the number of SCEVAddRecExprs present, which are kept at the end of /// the list. /// static void SimplifyAddOperands(SmallVectorImpl &Ops, const Type *Ty, ScalarEvolution &SE) { unsigned NumAddRecs = 0; for (unsigned i = Ops.size(); i > 0 && isa(Ops[i-1]); --i) ++NumAddRecs; // Group Ops into non-addrecs and addrecs. SmallVector NoAddRecs(Ops.begin(), Ops.end() - NumAddRecs); SmallVector AddRecs(Ops.end() - NumAddRecs, Ops.end()); // Let ScalarEvolution sort and simplify the non-addrecs list. const SCEV *Sum = NoAddRecs.empty() ? SE.getIntegerSCEV(0, Ty) : SE.getAddExpr(NoAddRecs); // If it returned an add, use the operands. Otherwise it simplified // the sum into a single value, so just use that. if (const SCEVAddExpr *Add = dyn_cast(Sum)) Ops = Add->getOperands(); else { Ops.clear(); if (!Sum->isZero()) Ops.push_back(Sum); } // Then append the addrecs. Ops.insert(Ops.end(), AddRecs.begin(), AddRecs.end()); } /// SplitAddRecs - Flatten a list of add operands, moving addrec start values /// out to the top level. For example, convert {a + b,+,c} to a, b, {0,+,d}. /// This helps expose more opportunities for folding parts of the expressions /// into GEP indices. /// static void SplitAddRecs(SmallVectorImpl &Ops, const Type *Ty, ScalarEvolution &SE) { // Find the addrecs. SmallVector AddRecs; for (unsigned i = 0, e = Ops.size(); i != e; ++i) while (const SCEVAddRecExpr *A = dyn_cast(Ops[i])) { const SCEV *Start = A->getStart(); if (Start->isZero()) break; const SCEV *Zero = SE.getIntegerSCEV(0, Ty); AddRecs.push_back(SE.getAddRecExpr(Zero, A->getStepRecurrence(SE), A->getLoop())); if (const SCEVAddExpr *Add = dyn_cast(Start)) { Ops[i] = Zero; Ops.insert(Ops.end(), Add->op_begin(), Add->op_end()); e += Add->getNumOperands(); } else { Ops[i] = Start; } } if (!AddRecs.empty()) { // Add the addrecs onto the end of the list. Ops.insert(Ops.end(), AddRecs.begin(), AddRecs.end()); // Resort the operand list, moving any constants to the front. SimplifyAddOperands(Ops, Ty, SE); } } /// expandAddToGEP - Expand an addition expression with a pointer type into /// a GEP instead of using ptrtoint+arithmetic+inttoptr. This helps /// BasicAliasAnalysis and other passes analyze the result. See the rules /// for getelementptr vs. inttoptr in /// http://llvm.org/docs/LangRef.html#pointeraliasing /// for details. /// /// Design note: The correctness of using getelmeentptr here 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 GepIndices; SmallVector Ops(op_begin, op_end); bool AnyNonZeroIndices = false; // Split AddRecs up into parts as either of the parts may be usable // without the other. SplitAddRecs(Ops, Ty, SE); // 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 (;;) { const SCEV *ElSize = SE.getAllocSizeExpr(ElTy); // If the scale size is not 0, attempt to factor out a scale for // array indexing. SmallVector ScaledOps; if (ElTy->isSized() && !ElSize->isZero()) { SmallVector NewOps; for (unsigned i = 0, e = Ops.size(); i != e; ++i) { const SCEV *Op = Ops[i]; const SCEV *Remainder = SE.getIntegerSCEV(0, Ty); if (FactorOutConstant(Op, Remainder, ElSize, SE, SE.TD)) { // Op now has ElSize factored out. ScaledOps.push_back(Op); if (!Remainder->isZero()) NewOps.push_back(Remainder); AnyNonZeroIndices = true; } else { // The operand was not divisible, so add it to the list of operands // we'll scan next iteration. NewOps.push_back(Ops[i]); } } // If we made any changes, update Ops. if (!ScaledOps.empty()) { Ops = NewOps; SimplifyAddOperands(Ops, Ty, SE); } } // Record the scaled array index for this level of the type. If // we didn't find any operands that could be factored, tentatively // assume that element zero was selected (since the zero offset // would obviously be folded away). Value *Scaled = ScaledOps.empty() ? Constant::getNullValue(Ty) : expandCodeFor(SE.getAddExpr(ScaledOps), Ty); GepIndices.push_back(Scaled); // Collect struct field index operands. while (const StructType *STy = dyn_cast(ElTy)) { bool FoundFieldNo = false; // An empty struct has no fields. if (STy->getNumElements() == 0) break; if (SE.TD) { // With TargetData, field offsets are known. See if a constant offset // falls within any of the struct fields. if (Ops.empty()) break; if (const SCEVConstant *C = dyn_cast(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::getInt32Ty(Ty->getContext()), ElIdx)); ElTy = STy->getTypeAtIndex(ElIdx); Ops[0] = SE.getConstant(Ty, FullOffset - SL.getElementOffset(ElIdx)); AnyNonZeroIndices = true; FoundFieldNo = true; } } } else { // Without TargetData, just check for a SCEVFieldOffsetExpr of the // appropriate struct type. for (unsigned i = 0, e = Ops.size(); i != e; ++i) if (const SCEVFieldOffsetExpr *FO = dyn_cast(Ops[i])) if (FO->getStructType() == STy) { unsigned FieldNo = FO->getFieldNo(); GepIndices.push_back( ConstantInt::get(Type::getInt32Ty(Ty->getContext()), FieldNo)); ElTy = STy->getTypeAtIndex(FieldNo); Ops[i] = SE.getConstant(Ty, 0); AnyNonZeroIndices = true; FoundFieldNo = true; break; } } // If no struct field offsets were found, tentatively assume that // field zero was selected (since the zero offset would obviously // be folded away). if (!FoundFieldNo) { ElTy = STy->getTypeAtIndex(0u); GepIndices.push_back( Constant::getNullValue(Type::getInt32Ty(Ty->getContext()))); } } if (const ArrayType *ATy = dyn_cast(ElTy)) ElTy = ATy->getElementType(); else 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) { // Cast the base to i8*. V = InsertNoopCastOfTo(V, Type::getInt8Ty(Ty->getContext())->getPointerTo(PTy->getAddressSpace())); // Expand the operands for a plain byte offset. Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty); // Fold a GEP with constant operands. if (Constant *CLHS = dyn_cast(V)) if (Constant *CRHS = dyn_cast(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; } } // Emit a GEP. Value *GEP = Builder.CreateGEP(V, Idx, "uglygep"); 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) { int NumOperands = S->getNumOperands(); const Type *Ty = SE.getEffectiveSCEVType(S->getType()); // Find the index of an operand to start with. Choose the operand with // pointer type, if there is one, or the last operand otherwise. int PIdx = 0; for (; PIdx != NumOperands - 1; ++PIdx) if (isa(S->getOperand(PIdx)->getType())) break; // Expand code for the operand that we chose. Value *V = expand(S->getOperand(PIdx)); // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the // comments on expandAddToGEP for details. if (const PointerType *PTy = dyn_cast(V->getType())) { // Take the operand at PIdx out of the list. const SmallVectorImpl &Ops = S->getOperands(); SmallVector NewOps; NewOps.insert(NewOps.end(), Ops.begin(), Ops.begin() + PIdx); NewOps.insert(NewOps.end(), Ops.begin() + PIdx + 1, Ops.end()); // Make a GEP. return expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, V); } // Otherwise, we'll expand the rest of the SCEVAddExpr as plain integer // arithmetic. V = InsertNoopCastOfTo(V, Ty); // Emit a bunch of add instructions for (int i = NumOperands-1; i >= 0; --i) { if (i == PIdx) continue; 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(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, Constant::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(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(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(Base)) { Base = A->getOperand(A->getNumOperands()-1); SmallVector 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(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(V))); while (isa(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 &SOperands = S->getOperands(); SmallVector 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. 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(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(Base) && !isa(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(); PHINode *PN = PHINode::Create(Ty, "indvar", Header->begin()); InsertedValues.insert(PN); Constant *One = ConstantInt::get(Ty, 1); for (pred_iterator HPI = pred_begin(Header), HPE = pred_end(Header); HPI != HPE; ++HPI) if (L->contains(*HPI)) { // Insert a unit add instruction right before the terminator corresponding // to the back-edge. Instruction *Add = BinaryOperator::CreateAdd(PN, One, "indvar.next", (*HPI)->getTerminator()); InsertedValues.insert(Add); PN->addIncoming(Add, *HPI); } else { PN->addIncoming(Constant::getNullValue(Ty), *HPI); } } // {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(Ext)) NewS = Ext; const SCEV *V = cast(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::visitFieldOffsetExpr(const SCEVFieldOffsetExpr *S) { return ConstantExpr::getOffsetOf(S->getStructType(), S->getFieldNo()); } Value *SCEVExpander::visitAllocSizeExpr(const SCEVAllocSizeExpr *S) { return ConstantExpr::getSizeOf(S->getAllocType()); } 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, AssertingVH >::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; }