| //===- InstructionCombining.cpp - Combine multiple instructions -----------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // InstructionCombining - Combine instructions to form fewer, simple |
| // instructions. This pass does not modify the CFG This pass is where algebraic |
| // simplification happens. |
| // |
| // This pass combines things like: |
| // %Y = add int 1, %X |
| // %Z = add int 1, %Y |
| // into: |
| // %Z = add int 2, %X |
| // |
| // This is a simple worklist driven algorithm. |
| // |
| // This pass guarantees that the following canonicalizations are performed on |
| // the program: |
| // 1. If a binary operator has a constant operand, it is moved to the RHS |
| // 2. Bitwise operators with constant operands are always grouped so that |
| // shifts are performed first, then or's, then and's, then xor's. |
| // 3. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible |
| // 4. All SetCC instructions on boolean values are replaced with logical ops |
| // 5. add X, X is represented as (X*2) => (X << 1) |
| // 6. Multiplies with a power-of-two constant argument are transformed into |
| // shifts. |
| // N. This list is incomplete |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Constants.h" |
| #include "llvm/ConstantHandling.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/GlobalVariable.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/Support/InstIterator.h" |
| #include "llvm/Support/InstVisitor.h" |
| #include "llvm/Support/CallSite.h" |
| #include "Support/Statistic.h" |
| #include <algorithm> |
| |
| namespace llvm { |
| |
| namespace { |
| Statistic<> NumCombined ("instcombine", "Number of insts combined"); |
| Statistic<> NumConstProp("instcombine", "Number of constant folds"); |
| Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated"); |
| |
| class InstCombiner : public FunctionPass, |
| public InstVisitor<InstCombiner, Instruction*> { |
| // Worklist of all of the instructions that need to be simplified. |
| std::vector<Instruction*> WorkList; |
| TargetData *TD; |
| |
| void AddUsesToWorkList(Instruction &I) { |
| // The instruction was simplified, add all users of the instruction to |
| // the work lists because they might get more simplified now... |
| // |
| for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); |
| UI != UE; ++UI) |
| WorkList.push_back(cast<Instruction>(*UI)); |
| } |
| |
| // removeFromWorkList - remove all instances of I from the worklist. |
| void removeFromWorkList(Instruction *I); |
| public: |
| virtual bool runOnFunction(Function &F); |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<TargetData>(); |
| AU.setPreservesCFG(); |
| } |
| |
| // Visitation implementation - Implement instruction combining for different |
| // instruction types. The semantics are as follows: |
| // Return Value: |
| // null - No change was made |
| // I - Change was made, I is still valid, I may be dead though |
| // otherwise - Change was made, replace I with returned instruction |
| // |
| Instruction *visitAdd(BinaryOperator &I); |
| Instruction *visitSub(BinaryOperator &I); |
| Instruction *visitMul(BinaryOperator &I); |
| Instruction *visitDiv(BinaryOperator &I); |
| Instruction *visitRem(BinaryOperator &I); |
| Instruction *visitAnd(BinaryOperator &I); |
| Instruction *visitOr (BinaryOperator &I); |
| Instruction *visitXor(BinaryOperator &I); |
| Instruction *visitSetCondInst(BinaryOperator &I); |
| Instruction *visitShiftInst(ShiftInst &I); |
| Instruction *visitCastInst(CastInst &CI); |
| Instruction *visitCallInst(CallInst &CI); |
| Instruction *visitInvokeInst(InvokeInst &II); |
| Instruction *visitPHINode(PHINode &PN); |
| Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP); |
| Instruction *visitAllocationInst(AllocationInst &AI); |
| Instruction *visitLoadInst(LoadInst &LI); |
| Instruction *visitBranchInst(BranchInst &BI); |
| |
| // visitInstruction - Specify what to return for unhandled instructions... |
| Instruction *visitInstruction(Instruction &I) { return 0; } |
| |
| private: |
| Instruction *visitCallSite(CallSite CS); |
| bool transformConstExprCastCall(CallSite CS); |
| |
| // InsertNewInstBefore - insert an instruction New before instruction Old |
| // in the program. Add the new instruction to the worklist. |
| // |
| void InsertNewInstBefore(Instruction *New, Instruction &Old) { |
| assert(New && New->getParent() == 0 && |
| "New instruction already inserted into a basic block!"); |
| BasicBlock *BB = Old.getParent(); |
| BB->getInstList().insert(&Old, New); // Insert inst |
| WorkList.push_back(New); // Add to worklist |
| } |
| |
| public: |
| // ReplaceInstUsesWith - This method is to be used when an instruction is |
| // found to be dead, replacable with another preexisting expression. Here |
| // we add all uses of I to the worklist, replace all uses of I with the new |
| // value, then return I, so that the inst combiner will know that I was |
| // modified. |
| // |
| Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) { |
| AddUsesToWorkList(I); // Add all modified instrs to worklist |
| I.replaceAllUsesWith(V); |
| return &I; |
| } |
| private: |
| /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the |
| /// InsertBefore instruction. This is specialized a bit to avoid inserting |
| /// casts that are known to not do anything... |
| /// |
| Value *InsertOperandCastBefore(Value *V, const Type *DestTy, |
| Instruction *InsertBefore); |
| |
| // SimplifyCommutative - This performs a few simplifications for commutative |
| // operators... |
| bool SimplifyCommutative(BinaryOperator &I); |
| |
| Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS, |
| ConstantIntegral *AndRHS, BinaryOperator &TheAnd); |
| }; |
| |
| RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions"); |
| } |
| |
| // getComplexity: Assign a complexity or rank value to LLVM Values... |
| // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst |
| static unsigned getComplexity(Value *V) { |
| if (isa<Instruction>(V)) { |
| if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V)) |
| return 2; |
| return 3; |
| } |
| if (isa<Argument>(V)) return 2; |
| return isa<Constant>(V) ? 0 : 1; |
| } |
| |
| // isOnlyUse - Return true if this instruction will be deleted if we stop using |
| // it. |
| static bool isOnlyUse(Value *V) { |
| return V->hasOneUse() || isa<Constant>(V); |
| } |
| |
| // SimplifyCommutative - This performs a few simplifications for commutative |
| // operators: |
| // |
| // 1. Order operands such that they are listed from right (least complex) to |
| // left (most complex). This puts constants before unary operators before |
| // binary operators. |
| // |
| // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2)) |
| // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2)) |
| // |
| bool InstCombiner::SimplifyCommutative(BinaryOperator &I) { |
| bool Changed = false; |
| if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) |
| Changed = !I.swapOperands(); |
| |
| if (!I.isAssociative()) return Changed; |
| Instruction::BinaryOps Opcode = I.getOpcode(); |
| if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0))) |
| if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) { |
| if (isa<Constant>(I.getOperand(1))) { |
| Constant *Folded = ConstantExpr::get(I.getOpcode(), |
| cast<Constant>(I.getOperand(1)), |
| cast<Constant>(Op->getOperand(1))); |
| I.setOperand(0, Op->getOperand(0)); |
| I.setOperand(1, Folded); |
| return true; |
| } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1))) |
| if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) && |
| isOnlyUse(Op) && isOnlyUse(Op1)) { |
| Constant *C1 = cast<Constant>(Op->getOperand(1)); |
| Constant *C2 = cast<Constant>(Op1->getOperand(1)); |
| |
| // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2)) |
| Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2); |
| Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0), |
| Op1->getOperand(0), |
| Op1->getName(), &I); |
| WorkList.push_back(New); |
| I.setOperand(0, New); |
| I.setOperand(1, Folded); |
| return true; |
| } |
| } |
| return Changed; |
| } |
| |
| // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction |
| // if the LHS is a constant zero (which is the 'negate' form). |
| // |
| static inline Value *dyn_castNegVal(Value *V) { |
| if (BinaryOperator::isNeg(V)) |
| return BinaryOperator::getNegArgument(cast<BinaryOperator>(V)); |
| |
| // Constants can be considered to be negated values if they can be folded... |
| if (Constant *C = dyn_cast<Constant>(V)) |
| return ConstantExpr::get(Instruction::Sub, |
| Constant::getNullValue(V->getType()), C); |
| return 0; |
| } |
| |
| static inline Value *dyn_castNotVal(Value *V) { |
| if (BinaryOperator::isNot(V)) |
| return BinaryOperator::getNotArgument(cast<BinaryOperator>(V)); |
| |
| // Constants can be considered to be not'ed values... |
| if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V)) |
| return ConstantExpr::get(Instruction::Xor, |
| ConstantIntegral::getAllOnesValue(C->getType()),C); |
| return 0; |
| } |
| |
| // dyn_castFoldableMul - If this value is a multiply that can be folded into |
| // other computations (because it has a constant operand), return the |
| // non-constant operand of the multiply. |
| // |
| static inline Value *dyn_castFoldableMul(Value *V) { |
| if (V->hasOneUse() && V->getType()->isInteger()) |
| if (Instruction *I = dyn_cast<Instruction>(V)) |
| if (I->getOpcode() == Instruction::Mul) |
| if (isa<Constant>(I->getOperand(1))) |
| return I->getOperand(0); |
| return 0; |
| } |
| |
| // dyn_castMaskingAnd - If this value is an And instruction masking a value with |
| // a constant, return the constant being anded with. |
| // |
| template<class ValueType> |
| static inline Constant *dyn_castMaskingAnd(ValueType *V) { |
| if (Instruction *I = dyn_cast<Instruction>(V)) |
| if (I->getOpcode() == Instruction::And) |
| return dyn_cast<Constant>(I->getOperand(1)); |
| |
| // If this is a constant, it acts just like we were masking with it. |
| return dyn_cast<Constant>(V); |
| } |
| |
| // Log2 - Calculate the log base 2 for the specified value if it is exactly a |
| // power of 2. |
| static unsigned Log2(uint64_t Val) { |
| assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!"); |
| unsigned Count = 0; |
| while (Val != 1) { |
| if (Val & 1) return 0; // Multiple bits set? |
| Val >>= 1; |
| ++Count; |
| } |
| return Count; |
| } |
| |
| |
| /// AssociativeOpt - Perform an optimization on an associative operator. This |
| /// function is designed to check a chain of associative operators for a |
| /// potential to apply a certain optimization. Since the optimization may be |
| /// applicable if the expression was reassociated, this checks the chain, then |
| /// reassociates the expression as necessary to expose the optimization |
| /// opportunity. This makes use of a special Functor, which must define |
| /// 'shouldApply' and 'apply' methods. |
| /// |
| template<typename Functor> |
| Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) { |
| unsigned Opcode = Root.getOpcode(); |
| Value *LHS = Root.getOperand(0); |
| |
| // Quick check, see if the immediate LHS matches... |
| if (F.shouldApply(LHS)) |
| return F.apply(Root); |
| |
| // Otherwise, if the LHS is not of the same opcode as the root, return. |
| Instruction *LHSI = dyn_cast<Instruction>(LHS); |
| while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) { |
| // Should we apply this transform to the RHS? |
| bool ShouldApply = F.shouldApply(LHSI->getOperand(1)); |
| |
| // If not to the RHS, check to see if we should apply to the LHS... |
| if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) { |
| cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS |
| ShouldApply = true; |
| } |
| |
| // If the functor wants to apply the optimization to the RHS of LHSI, |
| // reassociate the expression from ((? op A) op B) to (? op (A op B)) |
| if (ShouldApply) { |
| BasicBlock *BB = Root.getParent(); |
| // All of the instructions have a single use and have no side-effects, |
| // because of this, we can pull them all into the current basic block. |
| if (LHSI->getParent() != BB) { |
| // Move all of the instructions from root to LHSI into the current |
| // block. |
| Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0)); |
| Instruction *LastUse = &Root; |
| while (TmpLHSI->getParent() == BB) { |
| LastUse = TmpLHSI; |
| TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0)); |
| } |
| |
| // Loop over all of the instructions in other blocks, moving them into |
| // the current one. |
| Value *TmpLHS = TmpLHSI; |
| do { |
| TmpLHSI = cast<Instruction>(TmpLHS); |
| // Remove from current block... |
| TmpLHSI->getParent()->getInstList().remove(TmpLHSI); |
| // Insert before the last instruction... |
| BB->getInstList().insert(LastUse, TmpLHSI); |
| TmpLHS = TmpLHSI->getOperand(0); |
| } while (TmpLHSI != LHSI); |
| } |
| |
| // Now all of the instructions are in the current basic block, go ahead |
| // and perform the reassociation. |
| Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0)); |
| |
| // First move the selected RHS to the LHS of the root... |
| Root.setOperand(0, LHSI->getOperand(1)); |
| |
| // Make what used to be the LHS of the root be the user of the root... |
| Value *ExtraOperand = TmpLHSI->getOperand(1); |
| Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI |
| TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root |
| BB->getInstList().remove(&Root); // Remove root from the BB |
| BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI |
| |
| // Now propagate the ExtraOperand down the chain of instructions until we |
| // get to LHSI. |
| while (TmpLHSI != LHSI) { |
| Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0)); |
| Value *NextOp = NextLHSI->getOperand(1); |
| NextLHSI->setOperand(1, ExtraOperand); |
| TmpLHSI = NextLHSI; |
| ExtraOperand = NextOp; |
| } |
| |
| // Now that the instructions are reassociated, have the functor perform |
| // the transformation... |
| return F.apply(Root); |
| } |
| |
| LHSI = dyn_cast<Instruction>(LHSI->getOperand(0)); |
| } |
| return 0; |
| } |
| |
| |
| // AddRHS - Implements: X + X --> X << 1 |
| struct AddRHS { |
| Value *RHS; |
| AddRHS(Value *rhs) : RHS(rhs) {} |
| bool shouldApply(Value *LHS) const { return LHS == RHS; } |
| Instruction *apply(BinaryOperator &Add) const { |
| return new ShiftInst(Instruction::Shl, Add.getOperand(0), |
| ConstantInt::get(Type::UByteTy, 1)); |
| } |
| }; |
| |
| // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2) |
| // iff C1&C2 == 0 |
| struct AddMaskingAnd { |
| Constant *C2; |
| AddMaskingAnd(Constant *c) : C2(c) {} |
| bool shouldApply(Value *LHS) const { |
| if (Constant *C1 = dyn_castMaskingAnd(LHS)) |
| return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue(); |
| return false; |
| } |
| Instruction *apply(BinaryOperator &Add) const { |
| return BinaryOperator::create(Instruction::Or, Add.getOperand(0), |
| Add.getOperand(1)); |
| } |
| }; |
| |
| |
| |
| Instruction *InstCombiner::visitAdd(BinaryOperator &I) { |
| bool Changed = SimplifyCommutative(I); |
| Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); |
| |
| // X + 0 --> X |
| if (RHS == Constant::getNullValue(I.getType())) |
| return ReplaceInstUsesWith(I, LHS); |
| |
| // X + X --> X << 1 |
| if (I.getType()->isInteger()) |
| if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result; |
| |
| // -A + B --> B - A |
| if (Value *V = dyn_castNegVal(LHS)) |
| return BinaryOperator::create(Instruction::Sub, RHS, V); |
| |
| // A + -B --> A - B |
| if (!isa<Constant>(RHS)) |
| if (Value *V = dyn_castNegVal(RHS)) |
| return BinaryOperator::create(Instruction::Sub, LHS, V); |
| |
| // X*C + X --> X * (C+1) |
| if (dyn_castFoldableMul(LHS) == RHS) { |
| Constant *CP1 = |
| ConstantExpr::get(Instruction::Add, |
| cast<Constant>(cast<Instruction>(LHS)->getOperand(1)), |
| ConstantInt::get(I.getType(), 1)); |
| return BinaryOperator::create(Instruction::Mul, RHS, CP1); |
| } |
| |
| // X + X*C --> X * (C+1) |
| if (dyn_castFoldableMul(RHS) == LHS) { |
| Constant *CP1 = |
| ConstantExpr::get(Instruction::Add, |
| cast<Constant>(cast<Instruction>(RHS)->getOperand(1)), |
| ConstantInt::get(I.getType(), 1)); |
| return BinaryOperator::create(Instruction::Mul, LHS, CP1); |
| } |
| |
| // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0 |
| if (Constant *C2 = dyn_castMaskingAnd(RHS)) |
| if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R; |
| |
| if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) { |
| if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) { |
| switch (ILHS->getOpcode()) { |
| case Instruction::Xor: |
| // ~X + C --> (C-1) - X |
| if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1))) |
| if (XorRHS->isAllOnesValue()) |
| return BinaryOperator::create(Instruction::Sub, |
| *CRHS - *ConstantInt::get(I.getType(), 1), |
| ILHS->getOperand(0)); |
| break; |
| default: break; |
| } |
| } |
| } |
| |
| return Changed ? &I : 0; |
| } |
| |
| // isSignBit - Return true if the value represented by the constant only has the |
| // highest order bit set. |
| static bool isSignBit(ConstantInt *CI) { |
| unsigned NumBits = CI->getType()->getPrimitiveSize()*8; |
| return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1)); |
| } |
| |
| static unsigned getTypeSizeInBits(const Type *Ty) { |
| return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8; |
| } |
| |
| Instruction *InstCombiner::visitSub(BinaryOperator &I) { |
| Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); |
| |
| if (Op0 == Op1) // sub X, X -> 0 |
| return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); |
| |
| // If this is a 'B = x-(-A)', change to B = x+A... |
| if (Value *V = dyn_castNegVal(Op1)) |
| return BinaryOperator::create(Instruction::Add, Op0, V); |
| |
| if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) { |
| // Replace (-1 - A) with (~A)... |
| if (C->isAllOnesValue()) |
| return BinaryOperator::createNot(Op1); |
| |
| // C - ~X == X + (1+C) |
| if (BinaryOperator::isNot(Op1)) |
| return BinaryOperator::create(Instruction::Add, |
| BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)), |
| *C + *ConstantInt::get(I.getType(), 1)); |
| } |
| |
| if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) |
| if (Op1I->hasOneUse()) { |
| // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression |
| // is not used by anyone else... |
| // |
| if (Op1I->getOpcode() == Instruction::Sub) { |
| // Swap the two operands of the subexpr... |
| Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1); |
| Op1I->setOperand(0, IIOp1); |
| Op1I->setOperand(1, IIOp0); |
| |
| // Create the new top level add instruction... |
| return BinaryOperator::create(Instruction::Add, Op0, Op1); |
| } |
| |
| // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)... |
| // |
| if (Op1I->getOpcode() == Instruction::And && |
| (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) { |
| Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0); |
| |
| Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I); |
| return BinaryOperator::create(Instruction::And, Op0, NewNot); |
| } |
| |
| // X - X*C --> X * (1-C) |
| if (dyn_castFoldableMul(Op1I) == Op0) { |
| Constant *CP1 = |
| ConstantExpr::get(Instruction::Sub, |
| ConstantInt::get(I.getType(), 1), |
| cast<Constant>(cast<Instruction>(Op1)->getOperand(1))); |
| assert(CP1 && "Couldn't constant fold 1-C?"); |
| return BinaryOperator::create(Instruction::Mul, Op0, CP1); |
| } |
| } |
| |
| // X*C - X --> X * (C-1) |
| if (dyn_castFoldableMul(Op0) == Op1) { |
| Constant *CP1 = |
| ConstantExpr::get(Instruction::Sub, |
| cast<Constant>(cast<Instruction>(Op0)->getOperand(1)), |
| ConstantInt::get(I.getType(), 1)); |
| assert(CP1 && "Couldn't constant fold C - 1?"); |
| return BinaryOperator::create(Instruction::Mul, Op1, CP1); |
| } |
| |
| return 0; |
| } |
| |
| Instruction *InstCombiner::visitMul(BinaryOperator &I) { |
| bool Changed = SimplifyCommutative(I); |
| Value *Op0 = I.getOperand(0); |
| |
| // Simplify mul instructions with a constant RHS... |
| if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) { |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { |
| |
| // ((X << C1)*C2) == (X * (C2 << C1)) |
| if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0)) |
| if (SI->getOpcode() == Instruction::Shl) |
| if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1))) |
| return BinaryOperator::create(Instruction::Mul, SI->getOperand(0), |
| *CI << *ShOp); |
| |
| if (CI->isNullValue()) |
| return ReplaceInstUsesWith(I, Op1); // X * 0 == 0 |
| if (CI->equalsInt(1)) // X * 1 == X |
| return ReplaceInstUsesWith(I, Op0); |
| if (CI->isAllOnesValue()) // X * -1 == 0 - X |
| return BinaryOperator::createNeg(Op0, I.getName()); |
| |
| int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue(); |
| if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C |
| return new ShiftInst(Instruction::Shl, Op0, |
| ConstantUInt::get(Type::UByteTy, C)); |
| } else { |
| ConstantFP *Op1F = cast<ConstantFP>(Op1); |
| if (Op1F->isNullValue()) |
| return ReplaceInstUsesWith(I, Op1); |
| |
| // "In IEEE floating point, x*1 is not equivalent to x for nans. However, |
| // ANSI says we can drop signals, so we can do this anyway." (from GCC) |
| if (Op1F->getValue() == 1.0) |
| return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0' |
| } |
| } |
| |
| if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y |
| if (Value *Op1v = dyn_castNegVal(I.getOperand(1))) |
| return BinaryOperator::create(Instruction::Mul, Op0v, Op1v); |
| |
| return Changed ? &I : 0; |
| } |
| |
| Instruction *InstCombiner::visitDiv(BinaryOperator &I) { |
| // div X, 1 == X |
| if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) { |
| if (RHS->equalsInt(1)) |
| return ReplaceInstUsesWith(I, I.getOperand(0)); |
| |
| // Check to see if this is an unsigned division with an exact power of 2, |
| // if so, convert to a right shift. |
| if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS)) |
| if (uint64_t Val = C->getValue()) // Don't break X / 0 |
| if (uint64_t C = Log2(Val)) |
| return new ShiftInst(Instruction::Shr, I.getOperand(0), |
| ConstantUInt::get(Type::UByteTy, C)); |
| } |
| |
| // 0 / X == 0, we don't need to preserve faults! |
| if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0))) |
| if (LHS->equalsInt(0)) |
| return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); |
| |
| return 0; |
| } |
| |
| |
| Instruction *InstCombiner::visitRem(BinaryOperator &I) { |
| if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) { |
| if (RHS->equalsInt(1)) // X % 1 == 0 |
| return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); |
| |
| // Check to see if this is an unsigned remainder with an exact power of 2, |
| // if so, convert to a bitwise and. |
| if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS)) |
| if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero) |
| if (Log2(Val)) |
| return BinaryOperator::create(Instruction::And, I.getOperand(0), |
| ConstantUInt::get(I.getType(), Val-1)); |
| } |
| |
| // 0 % X == 0, we don't need to preserve faults! |
| if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0))) |
| if (LHS->equalsInt(0)) |
| return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); |
| |
| return 0; |
| } |
| |
| // isMaxValueMinusOne - return true if this is Max-1 |
| static bool isMaxValueMinusOne(const ConstantInt *C) { |
| if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) { |
| // Calculate -1 casted to the right type... |
| unsigned TypeBits = C->getType()->getPrimitiveSize()*8; |
| uint64_t Val = ~0ULL; // All ones |
| Val >>= 64-TypeBits; // Shift out unwanted 1 bits... |
| return CU->getValue() == Val-1; |
| } |
| |
| const ConstantSInt *CS = cast<ConstantSInt>(C); |
| |
| // Calculate 0111111111..11111 |
| unsigned TypeBits = C->getType()->getPrimitiveSize()*8; |
| int64_t Val = INT64_MAX; // All ones |
| Val >>= 64-TypeBits; // Shift out unwanted 1 bits... |
| return CS->getValue() == Val-1; |
| } |
| |
| // isMinValuePlusOne - return true if this is Min+1 |
| static bool isMinValuePlusOne(const ConstantInt *C) { |
| if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) |
| return CU->getValue() == 1; |
| |
| const ConstantSInt *CS = cast<ConstantSInt>(C); |
| |
| // Calculate 1111111111000000000000 |
| unsigned TypeBits = C->getType()->getPrimitiveSize()*8; |
| int64_t Val = -1; // All ones |
| Val <<= TypeBits-1; // Shift over to the right spot |
| return CS->getValue() == Val+1; |
| } |
| |
| /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits |
| /// are carefully arranged to allow folding of expressions such as: |
| /// |
| /// (A < B) | (A > B) --> (A != B) |
| /// |
| /// Bit value '4' represents that the comparison is true if A > B, bit value '2' |
| /// represents that the comparison is true if A == B, and bit value '1' is true |
| /// if A < B. |
| /// |
| static unsigned getSetCondCode(const SetCondInst *SCI) { |
| switch (SCI->getOpcode()) { |
| // False -> 0 |
| case Instruction::SetGT: return 1; |
| case Instruction::SetEQ: return 2; |
| case Instruction::SetGE: return 3; |
| case Instruction::SetLT: return 4; |
| case Instruction::SetNE: return 5; |
| case Instruction::SetLE: return 6; |
| // True -> 7 |
| default: |
| assert(0 && "Invalid SetCC opcode!"); |
| return 0; |
| } |
| } |
| |
| /// getSetCCValue - This is the complement of getSetCondCode, which turns an |
| /// opcode and two operands into either a constant true or false, or a brand new |
| /// SetCC instruction. |
| static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) { |
| switch (Opcode) { |
| case 0: return ConstantBool::False; |
| case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS); |
| case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS); |
| case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS); |
| case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS); |
| case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS); |
| case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS); |
| case 7: return ConstantBool::True; |
| default: assert(0 && "Illegal SetCCCode!"); return 0; |
| } |
| } |
| |
| // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B) |
| struct FoldSetCCLogical { |
| InstCombiner &IC; |
| Value *LHS, *RHS; |
| FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI) |
| : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {} |
| bool shouldApply(Value *V) const { |
| if (SetCondInst *SCI = dyn_cast<SetCondInst>(V)) |
| return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS || |
| SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS); |
| return false; |
| } |
| Instruction *apply(BinaryOperator &Log) const { |
| SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0)); |
| if (SCI->getOperand(0) != LHS) { |
| assert(SCI->getOperand(1) == LHS); |
| SCI->swapOperands(); // Swap the LHS and RHS of the SetCC |
| } |
| |
| unsigned LHSCode = getSetCondCode(SCI); |
| unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1))); |
| unsigned Code; |
| switch (Log.getOpcode()) { |
| case Instruction::And: Code = LHSCode & RHSCode; break; |
| case Instruction::Or: Code = LHSCode | RHSCode; break; |
| case Instruction::Xor: Code = LHSCode ^ RHSCode; break; |
| default: assert(0 && "Illegal logical opcode!"); return 0; |
| } |
| |
| Value *RV = getSetCCValue(Code, LHS, RHS); |
| if (Instruction *I = dyn_cast<Instruction>(RV)) |
| return I; |
| // Otherwise, it's a constant boolean value... |
| return IC.ReplaceInstUsesWith(Log, RV); |
| } |
| }; |
| |
| |
| // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where |
| // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is |
| // guaranteed to be either a shift instruction or a binary operator. |
| Instruction *InstCombiner::OptAndOp(Instruction *Op, |
| ConstantIntegral *OpRHS, |
| ConstantIntegral *AndRHS, |
| BinaryOperator &TheAnd) { |
| Value *X = Op->getOperand(0); |
| switch (Op->getOpcode()) { |
| case Instruction::Xor: |
| if ((*AndRHS & *OpRHS)->isNullValue()) { |
| // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0 |
| return BinaryOperator::create(Instruction::And, X, AndRHS); |
| } else if (Op->hasOneUse()) { |
| // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2) |
| std::string OpName = Op->getName(); Op->setName(""); |
| Instruction *And = BinaryOperator::create(Instruction::And, |
| X, AndRHS, OpName); |
| InsertNewInstBefore(And, TheAnd); |
| return BinaryOperator::create(Instruction::Xor, And, *AndRHS & *OpRHS); |
| } |
| break; |
| case Instruction::Or: |
| // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0 |
| if ((*AndRHS & *OpRHS)->isNullValue()) |
| return BinaryOperator::create(Instruction::And, X, AndRHS); |
| else { |
| Constant *Together = *AndRHS & *OpRHS; |
| if (Together == AndRHS) // (X | C) & C --> C |
| return ReplaceInstUsesWith(TheAnd, AndRHS); |
| |
| if (Op->hasOneUse() && Together != OpRHS) { |
| // (X | C1) & C2 --> (X | (C1&C2)) & C2 |
| std::string Op0Name = Op->getName(); Op->setName(""); |
| Instruction *Or = BinaryOperator::create(Instruction::Or, X, |
| Together, Op0Name); |
| InsertNewInstBefore(Or, TheAnd); |
| return BinaryOperator::create(Instruction::And, Or, AndRHS); |
| } |
| } |
| break; |
| case Instruction::Add: |
| if (Op->hasOneUse()) { |
| // Adding a one to a single bit bit-field should be turned into an XOR |
| // of the bit. First thing to check is to see if this AND is with a |
| // single bit constant. |
| unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue(); |
| |
| // Clear bits that are not part of the constant. |
| AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1; |
| |
| // If there is only one bit set... |
| if ((AndRHSV & (AndRHSV-1)) == 0) { |
| // Ok, at this point, we know that we are masking the result of the |
| // ADD down to exactly one bit. If the constant we are adding has |
| // no bits set below this bit, then we can eliminate the ADD. |
| unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue(); |
| |
| // Check to see if any bits below the one bit set in AndRHSV are set. |
| if ((AddRHS & (AndRHSV-1)) == 0) { |
| // If not, the only thing that can effect the output of the AND is |
| // the bit specified by AndRHSV. If that bit is set, the effect of |
| // the XOR is to toggle the bit. If it is clear, then the ADD has |
| // no effect. |
| if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop |
| TheAnd.setOperand(0, X); |
| return &TheAnd; |
| } else { |
| std::string Name = Op->getName(); Op->setName(""); |
| // Pull the XOR out of the AND. |
| Instruction *NewAnd = |
| BinaryOperator::create(Instruction::And, X, AndRHS, Name); |
| InsertNewInstBefore(NewAnd, TheAnd); |
| return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS); |
| } |
| } |
| } |
| } |
| break; |
| |
| case Instruction::Shl: { |
| // We know that the AND will not produce any of the bits shifted in, so if |
| // the anded constant includes them, clear them now! |
| // |
| Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType()); |
| Constant *CI = *AndRHS & *(*AllOne << *OpRHS); |
| if (CI != AndRHS) { |
| TheAnd.setOperand(1, CI); |
| return &TheAnd; |
| } |
| break; |
| } |
| case Instruction::Shr: |
| // We know that the AND will not produce any of the bits shifted in, so if |
| // the anded constant includes them, clear them now! This only applies to |
| // unsigned shifts, because a signed shr may bring in set bits! |
| // |
| if (AndRHS->getType()->isUnsigned()) { |
| Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType()); |
| Constant *CI = *AndRHS & *(*AllOne >> *OpRHS); |
| if (CI != AndRHS) { |
| TheAnd.setOperand(1, CI); |
| return &TheAnd; |
| } |
| } |
| break; |
| } |
| return 0; |
| } |
| |
| |
| Instruction *InstCombiner::visitAnd(BinaryOperator &I) { |
| bool Changed = SimplifyCommutative(I); |
| Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); |
| |
| // and X, X = X and X, 0 == 0 |
| if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType())) |
| return ReplaceInstUsesWith(I, Op1); |
| |
| // and X, -1 == X |
| if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) { |
| if (RHS->isAllOnesValue()) |
| return ReplaceInstUsesWith(I, Op0); |
| |
| // Optimize a variety of ((val OP C1) & C2) combinations... |
| if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) { |
| Instruction *Op0I = cast<Instruction>(Op0); |
| Value *X = Op0I->getOperand(0); |
| if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) |
| if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I)) |
| return Res; |
| } |
| } |
| |
| Value *Op0NotVal = dyn_castNotVal(Op0); |
| Value *Op1NotVal = dyn_castNotVal(Op1); |
| |
| // (~A & ~B) == (~(A | B)) - Demorgan's Law |
| if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) { |
| Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal, |
| Op1NotVal,I.getName()+".demorgan"); |
| InsertNewInstBefore(Or, I); |
| return BinaryOperator::createNot(Or); |
| } |
| |
| if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0 |
| return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); |
| |
| // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B) |
| if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1))) |
| if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS))) |
| return R; |
| |
| return Changed ? &I : 0; |
| } |
| |
| |
| |
| Instruction *InstCombiner::visitOr(BinaryOperator &I) { |
| bool Changed = SimplifyCommutative(I); |
| Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); |
| |
| // or X, X = X or X, 0 == X |
| if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType())) |
| return ReplaceInstUsesWith(I, Op0); |
| |
| // or X, -1 == -1 |
| if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) { |
| if (RHS->isAllOnesValue()) |
| return ReplaceInstUsesWith(I, Op1); |
| |
| if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) { |
| // (X & C1) | C2 --> (X | C2) & (C1|C2) |
| if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0)) |
| if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) { |
| std::string Op0Name = Op0I->getName(); Op0I->setName(""); |
| Instruction *Or = BinaryOperator::create(Instruction::Or, |
| Op0I->getOperand(0), RHS, |
| Op0Name); |
| InsertNewInstBefore(Or, I); |
| return BinaryOperator::create(Instruction::And, Or, *RHS | *Op0CI); |
| } |
| |
| // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2) |
| if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0)) |
| if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) { |
| std::string Op0Name = Op0I->getName(); Op0I->setName(""); |
| Instruction *Or = BinaryOperator::create(Instruction::Or, |
| Op0I->getOperand(0), RHS, |
| Op0Name); |
| InsertNewInstBefore(Or, I); |
| return BinaryOperator::create(Instruction::Xor, Or, *Op0CI & *~*RHS); |
| } |
| } |
| } |
| |
| // (A & C1)|(A & C2) == A & (C1|C2) |
| if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0)) |
| if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1)) |
| if (LHS->getOperand(0) == RHS->getOperand(0)) |
| if (Constant *C0 = dyn_castMaskingAnd(LHS)) |
| if (Constant *C1 = dyn_castMaskingAnd(RHS)) |
| return BinaryOperator::create(Instruction::And, LHS->getOperand(0), |
| *C0 | *C1); |
| |
| Value *Op0NotVal = dyn_castNotVal(Op0); |
| Value *Op1NotVal = dyn_castNotVal(Op1); |
| |
| if (Op1 == Op0NotVal) // ~A | A == -1 |
| return ReplaceInstUsesWith(I, |
| ConstantIntegral::getAllOnesValue(I.getType())); |
| |
| if (Op0 == Op1NotVal) // A | ~A == -1 |
| return ReplaceInstUsesWith(I, |
| ConstantIntegral::getAllOnesValue(I.getType())); |
| |
| // (~A | ~B) == (~(A & B)) - Demorgan's Law |
| if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) { |
| Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal, |
| Op1NotVal,I.getName()+".demorgan", |
| &I); |
| WorkList.push_back(And); |
| return BinaryOperator::createNot(And); |
| } |
| |
| // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B) |
| if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1))) |
| if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS))) |
| return R; |
| |
| return Changed ? &I : 0; |
| } |
| |
| |
| |
| Instruction *InstCombiner::visitXor(BinaryOperator &I) { |
| bool Changed = SimplifyCommutative(I); |
| Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); |
| |
| // xor X, X = 0 |
| if (Op0 == Op1) |
| return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); |
| |
| if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) { |
| // xor X, 0 == X |
| if (RHS->isNullValue()) |
| return ReplaceInstUsesWith(I, Op0); |
| |
| if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) { |
| // xor (setcc A, B), true = not (setcc A, B) = setncc A, B |
| if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I)) |
| if (RHS == ConstantBool::True && SCI->hasOneUse()) |
| return new SetCondInst(SCI->getInverseCondition(), |
| SCI->getOperand(0), SCI->getOperand(1)); |
| |
| // ~(c-X) == X-c-1 == X+(-c-1) |
| if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue() && |
| isa<Constant>(Op0I->getOperand(0))) { |
| Constant *ConstantRHS = *-*cast<Constant>(Op0I->getOperand(0)) - |
| *ConstantInt::get(I.getType(), 1); |
| return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1), |
| ConstantRHS); |
| } |
| |
| if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) |
| switch (Op0I->getOpcode()) { |
| case Instruction::Add: |
| // ~(X-c) --> (-c-1)-X |
| if (RHS->isAllOnesValue()) |
| return BinaryOperator::create(Instruction::Sub, |
| *-*Op0CI - |
| *ConstantInt::get(I.getType(), 1), |
| Op0I->getOperand(0)); |
| break; |
| case Instruction::And: |
| // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0 |
| if ((*RHS & *Op0CI)->isNullValue()) |
| return BinaryOperator::create(Instruction::Or, Op0, RHS); |
| break; |
| case Instruction::Or: |
| // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2 |
| if ((*RHS & *Op0CI) == RHS) |
| return BinaryOperator::create(Instruction::And, Op0, ~*RHS); |
| break; |
| default: break; |
| } |
| } |
| } |
| |
| if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1 |
| if (X == Op1) |
| return ReplaceInstUsesWith(I, |
| ConstantIntegral::getAllOnesValue(I.getType())); |
| |
| if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1 |
| if (X == Op0) |
| return ReplaceInstUsesWith(I, |
| ConstantIntegral::getAllOnesValue(I.getType())); |
| |
| if (Instruction *Op1I = dyn_cast<Instruction>(Op1)) |
| if (Op1I->getOpcode() == Instruction::Or) |
| if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B |
| cast<BinaryOperator>(Op1I)->swapOperands(); |
| I.swapOperands(); |
| std::swap(Op0, Op1); |
| } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B |
| I.swapOperands(); |
| std::swap(Op0, Op1); |
| } |
| |
| if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) |
| if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) { |
| if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B |
| cast<BinaryOperator>(Op0I)->swapOperands(); |
| if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B |
| Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I); |
| WorkList.push_back(cast<Instruction>(NotB)); |
| return BinaryOperator::create(Instruction::And, Op0I->getOperand(0), |
| NotB); |
| } |
| } |
| |
| // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0 |
| if (Constant *C1 = dyn_castMaskingAnd(Op0)) |
| if (Constant *C2 = dyn_castMaskingAnd(Op1)) |
| if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue()) |
| return BinaryOperator::create(Instruction::Or, Op0, Op1); |
| |
| // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B) |
| if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1))) |
| if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS))) |
| return R; |
| |
| return Changed ? &I : 0; |
| } |
| |
| // AddOne, SubOne - Add or subtract a constant one from an integer constant... |
| static Constant *AddOne(ConstantInt *C) { |
| Constant *Result = ConstantExpr::get(Instruction::Add, C, |
| ConstantInt::get(C->getType(), 1)); |
| assert(Result && "Constant folding integer addition failed!"); |
| return Result; |
| } |
| static Constant *SubOne(ConstantInt *C) { |
| Constant *Result = ConstantExpr::get(Instruction::Sub, C, |
| ConstantInt::get(C->getType(), 1)); |
| assert(Result && "Constant folding integer addition failed!"); |
| return Result; |
| } |
| |
| // isTrueWhenEqual - Return true if the specified setcondinst instruction is |
| // true when both operands are equal... |
| // |
| static bool isTrueWhenEqual(Instruction &I) { |
| return I.getOpcode() == Instruction::SetEQ || |
| I.getOpcode() == Instruction::SetGE || |
| I.getOpcode() == Instruction::SetLE; |
| } |
| |
| Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) { |
| bool Changed = SimplifyCommutative(I); |
| Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); |
| const Type *Ty = Op0->getType(); |
| |
| // setcc X, X |
| if (Op0 == Op1) |
| return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I))); |
| |
| // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null! |
| if (isa<ConstantPointerNull>(Op1) && |
| (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0))) |
| return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I))); |
| |
| |
| // setcc's with boolean values can always be turned into bitwise operations |
| if (Ty == Type::BoolTy) { |
| // If this is <, >, or !=, we can change this into a simple xor instruction |
| if (!isTrueWhenEqual(I)) |
| return BinaryOperator::create(Instruction::Xor, Op0, Op1); |
| |
| // Otherwise we need to make a temporary intermediate instruction and insert |
| // it into the instruction stream. This is what we are after: |
| // |
| // seteq bool %A, %B -> ~(A^B) |
| // setle bool %A, %B -> ~A | B |
| // setge bool %A, %B -> A | ~B |
| // |
| if (I.getOpcode() == Instruction::SetEQ) { // seteq case |
| Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1, |
| I.getName()+"tmp"); |
| InsertNewInstBefore(Xor, I); |
| return BinaryOperator::createNot(Xor); |
| } |
| |
| // Handle the setXe cases... |
| assert(I.getOpcode() == Instruction::SetGE || |
| I.getOpcode() == Instruction::SetLE); |
| |
| if (I.getOpcode() == Instruction::SetGE) |
| std::swap(Op0, Op1); // Change setge -> setle |
| |
| // Now we just have the SetLE case. |
| Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp"); |
| InsertNewInstBefore(Not, I); |
| return BinaryOperator::create(Instruction::Or, Not, Op1); |
| } |
| |
| // Check to see if we are doing one of many comparisons against constant |
| // integers at the end of their ranges... |
| // |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { |
| // Simplify seteq and setne instructions... |
| if (I.getOpcode() == Instruction::SetEQ || |
| I.getOpcode() == Instruction::SetNE) { |
| bool isSetNE = I.getOpcode() == Instruction::SetNE; |
| |
| // If the first operand is (and|or|xor) with a constant, and the second |
| // operand is a constant, simplify a bit. |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) { |
| switch (BO->getOpcode()) { |
| case Instruction::Add: |
| if (CI->isNullValue()) { |
| // Replace ((add A, B) != 0) with (A != -B) if A or B is |
| // efficiently invertible, or if the add has just this one use. |
| Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1); |
| if (Value *NegVal = dyn_castNegVal(BOp1)) |
| return new SetCondInst(I.getOpcode(), BOp0, NegVal); |
| else if (Value *NegVal = dyn_castNegVal(BOp0)) |
| return new SetCondInst(I.getOpcode(), NegVal, BOp1); |
| else if (BO->hasOneUse()) { |
| Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName()); |
| BO->setName(""); |
| InsertNewInstBefore(Neg, I); |
| return new SetCondInst(I.getOpcode(), BOp0, Neg); |
| } |
| } |
| break; |
| case Instruction::Xor: |
| // For the xor case, we can xor two constants together, eliminating |
| // the explicit xor. |
| if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) |
| return BinaryOperator::create(I.getOpcode(), BO->getOperand(0), |
| *CI ^ *BOC); |
| |
| // FALLTHROUGH |
| case Instruction::Sub: |
| // Replace (([sub|xor] A, B) != 0) with (A != B) |
| if (CI->isNullValue()) |
| return new SetCondInst(I.getOpcode(), BO->getOperand(0), |
| BO->getOperand(1)); |
| break; |
| |
| case Instruction::Or: |
| // If bits are being or'd in that are not present in the constant we |
| // are comparing against, then the comparison could never succeed! |
| if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) |
| if (!(*BOC & *~*CI)->isNullValue()) |
| return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE)); |
| break; |
| |
| case Instruction::And: |
| if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) { |
| // If bits are being compared against that are and'd out, then the |
| // comparison can never succeed! |
| if (!(*CI & *~*BOC)->isNullValue()) |
| return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE)); |
| |
| // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X |
| // to be a signed value as appropriate. |
| if (isSignBit(BOC)) { |
| Value *X = BO->getOperand(0); |
| // If 'X' is not signed, insert a cast now... |
| if (!BOC->getType()->isSigned()) { |
| const Type *DestTy; |
| switch (BOC->getType()->getPrimitiveID()) { |
| case Type::UByteTyID: DestTy = Type::SByteTy; break; |
| case Type::UShortTyID: DestTy = Type::ShortTy; break; |
| case Type::UIntTyID: DestTy = Type::IntTy; break; |
| case Type::ULongTyID: DestTy = Type::LongTy; break; |
| default: assert(0 && "Invalid unsigned integer type!"); abort(); |
| } |
| CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed"); |
| InsertNewInstBefore(NewCI, I); |
| X = NewCI; |
| } |
| return new SetCondInst(isSetNE ? Instruction::SetLT : |
| Instruction::SetGE, X, |
| Constant::getNullValue(X->getType())); |
| } |
| } |
| default: break; |
| } |
| } |
| } |
| |
| // Check to see if we are comparing against the minimum or maximum value... |
| if (CI->isMinValue()) { |
| if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE |
| return ReplaceInstUsesWith(I, ConstantBool::False); |
| if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE |
| return ReplaceInstUsesWith(I, ConstantBool::True); |
| if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN |
| return BinaryOperator::create(Instruction::SetEQ, Op0, Op1); |
| if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN |
| return BinaryOperator::create(Instruction::SetNE, Op0, Op1); |
| |
| } else if (CI->isMaxValue()) { |
| if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE |
| return ReplaceInstUsesWith(I, ConstantBool::False); |
| if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE |
| return ReplaceInstUsesWith(I, ConstantBool::True); |
| if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX |
| return BinaryOperator::create(Instruction::SetEQ, Op0, Op1); |
| if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX |
| return BinaryOperator::create(Instruction::SetNE, Op0, Op1); |
| |
| // Comparing against a value really close to min or max? |
| } else if (isMinValuePlusOne(CI)) { |
| if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN |
| return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI)); |
| if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN |
| return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI)); |
| |
| } else if (isMaxValueMinusOne(CI)) { |
| if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX |
| return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI)); |
| if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX |
| return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI)); |
| } |
| } |
| |
| // Test to see if the operands of the setcc are casted versions of other |
| // values. If the cast can be stripped off both arguments, we do so now. |
| if (CastInst *CI = dyn_cast<CastInst>(Op0)) { |
| Value *CastOp0 = CI->getOperand(0); |
| if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) && |
| !isa<Argument>(Op1) && |
| (I.getOpcode() == Instruction::SetEQ || |
| I.getOpcode() == Instruction::SetNE)) { |
| // We keep moving the cast from the left operand over to the right |
| // operand, where it can often be eliminated completely. |
| Op0 = CastOp0; |
| |
| // If operand #1 is a cast instruction, see if we can eliminate it as |
| // well. |
| if (CastInst *CI2 = dyn_cast<CastInst>(Op1)) |
| if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo( |
| Op0->getType())) |
| Op1 = CI2->getOperand(0); |
| |
| // If Op1 is a constant, we can fold the cast into the constant. |
| if (Op1->getType() != Op0->getType()) |
| if (Constant *Op1C = dyn_cast<Constant>(Op1)) { |
| Op1 = ConstantExpr::getCast(Op1C, Op0->getType()); |
| } else { |
| // Otherwise, cast the RHS right before the setcc |
| Op1 = new CastInst(Op1, Op0->getType(), Op1->getName()); |
| InsertNewInstBefore(cast<Instruction>(Op1), I); |
| } |
| return BinaryOperator::create(I.getOpcode(), Op0, Op1); |
| } |
| |
| // Handle the special case of: setcc (cast bool to X), <cst> |
| // This comes up when you have code like |
| // int X = A < B; |
| // if (X) ... |
| // For generality, we handle any zero-extension of any operand comparison |
| // with a constant. |
| if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) { |
| const Type *SrcTy = CastOp0->getType(); |
| const Type *DestTy = Op0->getType(); |
| if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() && |
| (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) { |
| // Ok, we have an expansion of operand 0 into a new type. Get the |
| // constant value, masink off bits which are not set in the RHS. These |
| // could be set if the destination value is signed. |
| uint64_t ConstVal = ConstantRHS->getRawValue(); |
| ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1; |
| |
| // If the constant we are comparing it with has high bits set, which |
| // don't exist in the original value, the values could never be equal, |
| // because the source would be zero extended. |
| unsigned SrcBits = |
| SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8; |
| bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1)); |
| if (ConstVal & ~((1ULL << SrcBits)-1)) { |
| switch (I.getOpcode()) { |
| default: assert(0 && "Unknown comparison type!"); |
| case Instruction::SetEQ: |
| return ReplaceInstUsesWith(I, ConstantBool::False); |
| case Instruction::SetNE: |
| return ReplaceInstUsesWith(I, ConstantBool::True); |
| case Instruction::SetLT: |
| case Instruction::SetLE: |
| if (DestTy->isSigned() && HasSignBit) |
| return ReplaceInstUsesWith(I, ConstantBool::False); |
| return ReplaceInstUsesWith(I, ConstantBool::True); |
| case Instruction::SetGT: |
| case Instruction::SetGE: |
| if (DestTy->isSigned() && HasSignBit) |
| return ReplaceInstUsesWith(I, ConstantBool::True); |
| return ReplaceInstUsesWith(I, ConstantBool::False); |
| } |
| } |
| |
| // Otherwise, we can replace the setcc with a setcc of the smaller |
| // operand value. |
| Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy); |
| return BinaryOperator::create(I.getOpcode(), CastOp0, Op1); |
| } |
| } |
| } |
| return Changed ? &I : 0; |
| } |
| |
| |
| |
| Instruction *InstCombiner::visitShiftInst(ShiftInst &I) { |
| assert(I.getOperand(1)->getType() == Type::UByteTy); |
| Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); |
| bool isLeftShift = I.getOpcode() == Instruction::Shl; |
| |
| // shl X, 0 == X and shr X, 0 == X |
| // shl 0, X == 0 and shr 0, X == 0 |
| if (Op1 == Constant::getNullValue(Type::UByteTy) || |
| Op0 == Constant::getNullValue(Op0->getType())) |
| return ReplaceInstUsesWith(I, Op0); |
| |
| // shr int -1, X = -1 (for any arithmetic shift rights of ~0) |
| if (!isLeftShift) |
| if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0)) |
| if (CSI->isAllOnesValue()) |
| return ReplaceInstUsesWith(I, CSI); |
| |
| if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) { |
| // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr |
| // of a signed value. |
| // |
| unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8; |
| if (CUI->getValue() >= TypeBits && |
| (!Op0->getType()->isSigned() || isLeftShift)) |
| return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType())); |
| |
| // ((X*C1) << C2) == (X * (C1 << C2)) |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) |
| if (BO->getOpcode() == Instruction::Mul && isLeftShift) |
| if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1))) |
| return BinaryOperator::create(Instruction::Mul, BO->getOperand(0), |
| *BOOp << *CUI); |
| |
| |
| // If the operand is an bitwise operator with a constant RHS, and the |
| // shift is the only use, we can pull it out of the shift. |
| if (Op0->hasOneUse()) |
| if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0)) |
| if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) { |
| bool isValid = true; // Valid only for And, Or, Xor |
| bool highBitSet = false; // Transform if high bit of constant set? |
| |
| switch (Op0BO->getOpcode()) { |
| default: isValid = false; break; // Do not perform transform! |
| case Instruction::Or: |
| case Instruction::Xor: |
| highBitSet = false; |
| break; |
| case Instruction::And: |
| highBitSet = true; |
| break; |
| } |
| |
| // If this is a signed shift right, and the high bit is modified |
| // by the logical operation, do not perform the transformation. |
| // The highBitSet boolean indicates the value of the high bit of |
| // the constant which would cause it to be modified for this |
| // operation. |
| // |
| if (isValid && !isLeftShift && !I.getType()->isUnsigned()) { |
| uint64_t Val = Op0C->getRawValue(); |
| isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet; |
| } |
| |
| if (isValid) { |
| Constant *NewRHS = |
| ConstantFoldShiftInstruction(I.getOpcode(), Op0C, CUI); |
| |
| Instruction *NewShift = |
| new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI, |
| Op0BO->getName()); |
| Op0BO->setName(""); |
| InsertNewInstBefore(NewShift, I); |
| |
| return BinaryOperator::create(Op0BO->getOpcode(), NewShift, |
| NewRHS); |
| } |
| } |
| |
| // If this is a shift of a shift, see if we can fold the two together... |
| if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0)) |
| if (ConstantUInt *ShiftAmt1C = |
| dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) { |
| unsigned ShiftAmt1 = ShiftAmt1C->getValue(); |
| unsigned ShiftAmt2 = CUI->getValue(); |
| |
| // Check for (A << c1) << c2 and (A >> c1) >> c2 |
| if (I.getOpcode() == Op0SI->getOpcode()) { |
| unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift... |
| return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0), |
| ConstantUInt::get(Type::UByteTy, Amt)); |
| } |
| |
| // Check for (A << c1) >> c2 or visaversa. If we are dealing with |
| // signed types, we can only support the (A >> c1) << c2 configuration, |
| // because it can not turn an arbitrary bit of A into a sign bit. |
| if (I.getType()->isUnsigned() || isLeftShift) { |
| // Calculate bitmask for what gets shifted off the edge... |
| Constant *C = ConstantIntegral::getAllOnesValue(I.getType()); |
| if (isLeftShift) |
| C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C); |
| else |
| C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C); |
| |
| Instruction *Mask = |
| BinaryOperator::create(Instruction::And, Op0SI->getOperand(0), |
| C, Op0SI->getOperand(0)->getName()+".mask"); |
| InsertNewInstBefore(Mask, I); |
| |
| // Figure out what flavor of shift we should use... |
| if (ShiftAmt1 == ShiftAmt2) |
| return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2 |
| else if (ShiftAmt1 < ShiftAmt2) { |
| return new ShiftInst(I.getOpcode(), Mask, |
| ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1)); |
| } else { |
| return new ShiftInst(Op0SI->getOpcode(), Mask, |
| ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2)); |
| } |
| } |
| } |
| } |
| |
| return 0; |
| } |
| |
| |
| // isEliminableCastOfCast - Return true if it is valid to eliminate the CI |
| // instruction. |
| // |
| static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy, |
| const Type *DstTy) { |
| |
| // It is legal to eliminate the instruction if casting A->B->A if the sizes |
| // are identical and the bits don't get reinterpreted (for example |
| // int->float->int would not be allowed) |
| if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy)) |
| return true; |
| |
| // Allow free casting and conversion of sizes as long as the sign doesn't |
| // change... |
| if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) { |
| unsigned SrcSize = SrcTy->getPrimitiveSize(); |
| unsigned MidSize = MidTy->getPrimitiveSize(); |
| unsigned DstSize = DstTy->getPrimitiveSize(); |
| |
| // Cases where we are monotonically decreasing the size of the type are |
| // always ok, regardless of what sign changes are going on. |
| // |
| if (SrcSize >= MidSize && MidSize >= DstSize) |
| return true; |
| |
| // Cases where the source and destination type are the same, but the middle |
| // type is bigger are noops. |
| // |
| if (SrcSize == DstSize && MidSize > SrcSize) |
| return true; |
| |
| // If we are monotonically growing, things are more complex. |
| // |
| if (SrcSize <= MidSize && MidSize <= DstSize) { |
| // We have eight combinations of signedness to worry about. Here's the |
| // table: |
| static const int SignTable[8] = { |
| // CODE, SrcSigned, MidSigned, DstSigned, Comment |
| 1, // U U U Always ok |
| 1, // U U S Always ok |
| 3, // U S U Ok iff SrcSize != MidSize |
| 3, // U S S Ok iff SrcSize != MidSize |
| 0, // S U U Never ok |
| 2, // S U S Ok iff MidSize == DstSize |
| 1, // S S U Always ok |
| 1, // S S S Always ok |
| }; |
| |
| // Choose an action based on the current entry of the signtable that this |
| // cast of cast refers to... |
| unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned(); |
| switch (SignTable[Row]) { |
| case 0: return false; // Never ok |
| case 1: return true; // Always ok |
| case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize |
| case 3: // Ok iff SrcSize != MidSize |
| return SrcSize != MidSize || SrcTy == Type::BoolTy; |
| default: assert(0 && "Bad entry in sign table!"); |
| } |
| } |
| } |
| |
| // Otherwise, we cannot succeed. Specifically we do not want to allow things |
| // like: short -> ushort -> uint, because this can create wrong results if |
| // the input short is negative! |
| // |
| return false; |
| } |
| |
| static bool ValueRequiresCast(const Value *V, const Type *Ty) { |
| if (V->getType() == Ty || isa<Constant>(V)) return false; |
| if (const CastInst *CI = dyn_cast<CastInst>(V)) |
| if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty)) |
| return false; |
| return true; |
| } |
| |
| /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the |
| /// InsertBefore instruction. This is specialized a bit to avoid inserting |
| /// casts that are known to not do anything... |
| /// |
| Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy, |
| Instruction *InsertBefore) { |
| if (V->getType() == DestTy) return V; |
| if (Constant *C = dyn_cast<Constant>(V)) |
| return ConstantExpr::getCast(C, DestTy); |
| |
| CastInst *CI = new CastInst(V, DestTy, V->getName()); |
| InsertNewInstBefore(CI, *InsertBefore); |
| return CI; |
| } |
| |
| // CastInst simplification |
| // |
| Instruction *InstCombiner::visitCastInst(CastInst &CI) { |
| Value *Src = CI.getOperand(0); |
| |
| // If the user is casting a value to the same type, eliminate this cast |
| // instruction... |
| if (CI.getType() == Src->getType()) |
| return ReplaceInstUsesWith(CI, Src); |
| |
| // If casting the result of another cast instruction, try to eliminate this |
| // one! |
| // |
| if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { |
| if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(), |
| CSrc->getType(), CI.getType())) { |
| // This instruction now refers directly to the cast's src operand. This |
| // has a good chance of making CSrc dead. |
| CI.setOperand(0, CSrc->getOperand(0)); |
| return &CI; |
| } |
| |
| // If this is an A->B->A cast, and we are dealing with integral types, try |
| // to convert this into a logical 'and' instruction. |
| // |
| if (CSrc->getOperand(0)->getType() == CI.getType() && |
| CI.getType()->isInteger() && CSrc->getType()->isInteger() && |
| CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() && |
| CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){ |
| assert(CSrc->getType() != Type::ULongTy && |
| "Cannot have type bigger than ulong!"); |
| uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1; |
| Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue); |
| return BinaryOperator::create(Instruction::And, CSrc->getOperand(0), |
| AndOp); |
| } |
| } |
| |
| // If casting the result of a getelementptr instruction with no offset, turn |
| // this into a cast of the original pointer! |
| // |
| if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) { |
| bool AllZeroOperands = true; |
| for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i) |
| if (!isa<Constant>(GEP->getOperand(i)) || |
| !cast<Constant>(GEP->getOperand(i))->isNullValue()) { |
| AllZeroOperands = false; |
| break; |
| } |
| if (AllZeroOperands) { |
| CI.setOperand(0, GEP->getOperand(0)); |
| return &CI; |
| } |
| } |
| |
| // If we are casting a malloc or alloca to a pointer to a type of the same |
| // size, rewrite the allocation instruction to allocate the "right" type. |
| // |
| if (AllocationInst *AI = dyn_cast<AllocationInst>(Src)) |
| if (AI->hasOneUse() && !AI->isArrayAllocation()) |
| if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) { |
| // Get the type really allocated and the type casted to... |
| const Type *AllocElTy = AI->getAllocatedType(); |
| unsigned AllocElTySize = TD->getTypeSize(AllocElTy); |
| const Type *CastElTy = PTy->getElementType(); |
| unsigned CastElTySize = TD->getTypeSize(CastElTy); |
| |
| // If the allocation is for an even multiple of the cast type size |
| if (CastElTySize && (AllocElTySize % CastElTySize == 0)) { |
| Value *Amt = ConstantUInt::get(Type::UIntTy, |
| AllocElTySize/CastElTySize); |
| std::string Name = AI->getName(); AI->setName(""); |
| AllocationInst *New; |
| if (isa<MallocInst>(AI)) |
| New = new MallocInst(CastElTy, Amt, Name); |
| else |
| New = new AllocaInst(CastElTy, Amt, Name); |
| InsertNewInstBefore(New, CI); |
| return ReplaceInstUsesWith(CI, New); |
| } |
| } |
| |
| // If the source value is an instruction with only this use, we can attempt to |
| // propagate the cast into the instruction. Also, only handle integral types |
| // for now. |
| if (Instruction *SrcI = dyn_cast<Instruction>(Src)) |
| if (SrcI->hasOneUse() && Src->getType()->isIntegral() && |
| CI.getType()->isInteger()) { // Don't mess with casts to bool here |
| const Type *DestTy = CI.getType(); |
| unsigned SrcBitSize = getTypeSizeInBits(Src->getType()); |
| unsigned DestBitSize = getTypeSizeInBits(DestTy); |
| |
| Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0; |
| Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0; |
| |
| switch (SrcI->getOpcode()) { |
| case Instruction::Add: |
| case Instruction::Mul: |
| case Instruction::And: |
| case Instruction::Or: |
| case Instruction::Xor: |
| // If we are discarding information, or just changing the sign, rewrite. |
| if (DestBitSize <= SrcBitSize && DestBitSize != 1) { |
| // Don't insert two casts if they cannot be eliminated. We allow two |
| // casts to be inserted if the sizes are the same. This could only be |
| // converting signedness, which is a noop. |
| if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) || |
| !ValueRequiresCast(Op0, DestTy)) { |
| Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI); |
| Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI); |
| return BinaryOperator::create(cast<BinaryOperator>(SrcI) |
| ->getOpcode(), Op0c, Op1c); |
| } |
| } |
| break; |
| case Instruction::Shl: |
| // Allow changing the sign of the source operand. Do not allow changing |
| // the size of the shift, UNLESS the shift amount is a constant. We |
| // mush not change variable sized shifts to a smaller size, because it |
| // is undefined to shift more bits out than exist in the value. |
| if (DestBitSize == SrcBitSize || |
| (DestBitSize < SrcBitSize && isa<Constant>(Op1))) { |
| Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI); |
| return new ShiftInst(Instruction::Shl, Op0c, Op1); |
| } |
| break; |
| } |
| } |
| |
| return 0; |
| } |
| |
| // CallInst simplification |
| // |
| Instruction *InstCombiner::visitCallInst(CallInst &CI) { |
| return visitCallSite(&CI); |
| } |
| |
| // InvokeInst simplification |
| // |
| Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) { |
| return visitCallSite(&II); |
| } |
| |
| // getPromotedType - Return the specified type promoted as it would be to pass |
| // though a va_arg area... |
| static const Type *getPromotedType(const Type *Ty) { |
| switch (Ty->getPrimitiveID()) { |
| case Type::SByteTyID: |
| case Type::ShortTyID: return Type::IntTy; |
| case Type::UByteTyID: |
| case Type::UShortTyID: return Type::UIntTy; |
| case Type::FloatTyID: return Type::DoubleTy; |
| default: return Ty; |
| } |
| } |
| |
| // visitCallSite - Improvements for call and invoke instructions. |
| // |
| Instruction *InstCombiner::visitCallSite(CallSite CS) { |
| bool Changed = false; |
| |
| // If the callee is a constexpr cast of a function, attempt to move the cast |
| // to the arguments of the call/invoke. |
| if (transformConstExprCastCall(CS)) return 0; |
| |
| Value *Callee = CS.getCalledValue(); |
| const PointerType *PTy = cast<PointerType>(Callee->getType()); |
| const FunctionType *FTy = cast<FunctionType>(PTy->getElementType()); |
| if (FTy->isVarArg()) { |
| // See if we can optimize any arguments passed through the varargs area of |
| // the call. |
| for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(), |
| E = CS.arg_end(); I != E; ++I) |
| if (CastInst *CI = dyn_cast<CastInst>(*I)) { |
| // If this cast does not effect the value passed through the varargs |
| // area, we can eliminate the use of the cast. |
| Value *Op = CI->getOperand(0); |
| if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) { |
| *I = Op; |
| Changed = true; |
| } |
| } |
| } |
| |
| return Changed ? CS.getInstruction() : 0; |
| } |
| |
| // transformConstExprCastCall - If the callee is a constexpr cast of a function, |
| // attempt to move the cast to the arguments of the call/invoke. |
| // |
| bool InstCombiner::transformConstExprCastCall(CallSite CS) { |
| if (!isa<ConstantExpr>(CS.getCalledValue())) return false; |
| ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue()); |
| if (CE->getOpcode() != Instruction::Cast || |
| !isa<ConstantPointerRef>(CE->getOperand(0))) |
| return false; |
| ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0)); |
| if (!isa<Function>(CPR->getValue())) return false; |
| Function *Callee = cast<Function>(CPR->getValue()); |
| Instruction *Caller = CS.getInstruction(); |
| |
| // Okay, this is a cast from a function to a different type. Unless doing so |
| // would cause a type conversion of one of our arguments, change this call to |
| // be a direct call with arguments casted to the appropriate types. |
| // |
| const FunctionType *FT = Callee->getFunctionType(); |
| const Type *OldRetTy = Caller->getType(); |
| |
| if (Callee->isExternal() && |
| !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType())) |
| return false; // Cannot transform this return value... |
| |
| unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin()); |
| unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs); |
| |
| CallSite::arg_iterator AI = CS.arg_begin(); |
| for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) { |
| const Type *ParamTy = FT->getParamType(i); |
| bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy); |
| if (Callee->isExternal() && !isConvertible) return false; |
| } |
| |
| if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() && |
| Callee->isExternal()) |
| return false; // Do not delete arguments unless we have a function body... |
| |
| // Okay, we decided that this is a safe thing to do: go ahead and start |
| // inserting cast instructions as necessary... |
| std::vector<Value*> Args; |
| Args.reserve(NumActualArgs); |
| |
| AI = CS.arg_begin(); |
| for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) { |
| const Type *ParamTy = FT->getParamType(i); |
| if ((*AI)->getType() == ParamTy) { |
| Args.push_back(*AI); |
| } else { |
| Instruction *Cast = new CastInst(*AI, ParamTy, "tmp"); |
| InsertNewInstBefore(Cast, *Caller); |
| Args.push_back(Cast); |
| } |
| } |
| |
| // If the function takes more arguments than the call was taking, add them |
| // now... |
| for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i) |
| Args.push_back(Constant::getNullValue(FT->getParamType(i))); |
| |
| // If we are removing arguments to the function, emit an obnoxious warning... |
| if (FT->getNumParams() < NumActualArgs) |
| if (!FT->isVarArg()) { |
| std::cerr << "WARNING: While resolving call to function '" |
| << Callee->getName() << "' arguments were dropped!\n"; |
| } else { |
| // Add all of the arguments in their promoted form to the arg list... |
| for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) { |
| const Type *PTy = getPromotedType((*AI)->getType()); |
| if (PTy != (*AI)->getType()) { |
| // Must promote to pass through va_arg area! |
| Instruction *Cast = new CastInst(*AI, PTy, "tmp"); |
| InsertNewInstBefore(Cast, *Caller); |
| Args.push_back(Cast); |
| } else { |
| Args.push_back(*AI); |
| } |
| } |
| } |
| |
| if (FT->getReturnType() == Type::VoidTy) |
| Caller->setName(""); // Void type should not have a name... |
| |
| Instruction *NC; |
| if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) { |
| NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(), |
| Args, Caller->getName(), Caller); |
| } else { |
| NC = new CallInst(Callee, Args, Caller->getName(), Caller); |
| } |
| |
| // Insert a cast of the return type as necessary... |
| Value *NV = NC; |
| if (Caller->getType() != NV->getType() && !Caller->use_empty()) { |
| if (NV->getType() != Type::VoidTy) { |
| NV = NC = new CastInst(NC, Caller->getType(), "tmp"); |
| |
| // If this is an invoke instruction, we should insert it after the first |
| // non-phi, instruction in the normal successor block. |
| if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) { |
| BasicBlock::iterator I = II->getNormalDest()->begin(); |
| while (isa<PHINode>(I)) ++I; |
| InsertNewInstBefore(NC, *I); |
| } else { |
| // Otherwise, it's a call, just insert cast right after the call instr |
| InsertNewInstBefore(NC, *Caller); |
| } |
| AddUsesToWorkList(*Caller); |
| } else { |
| NV = Constant::getNullValue(Caller->getType()); |
| } |
| } |
| |
| if (Caller->getType() != Type::VoidTy && !Caller->use_empty()) |
| Caller->replaceAllUsesWith(NV); |
| Caller->getParent()->getInstList().erase(Caller); |
| removeFromWorkList(Caller); |
| return true; |
| } |
| |
| |
| |
| // PHINode simplification |
| // |
| Instruction *InstCombiner::visitPHINode(PHINode &PN) { |
| // If the PHI node only has one incoming value, eliminate the PHI node... |
| if (PN.getNumIncomingValues() == 1) |
| return ReplaceInstUsesWith(PN, PN.getIncomingValue(0)); |
| |
| // Otherwise if all of the incoming values are the same for the PHI, replace |
| // the PHI node with the incoming value. |
| // |
| Value *InVal = 0; |
| for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) |
| if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself... |
| if (InVal && PN.getIncomingValue(i) != InVal) |
| return 0; // Not the same, bail out. |
| else |
| InVal = PN.getIncomingValue(i); |
| |
| // The only case that could cause InVal to be null is if we have a PHI node |
| // that only has entries for itself. In this case, there is no entry into the |
| // loop, so kill the PHI. |
| // |
| if (InVal == 0) InVal = Constant::getNullValue(PN.getType()); |
| |
| // All of the incoming values are the same, replace the PHI node now. |
| return ReplaceInstUsesWith(PN, InVal); |
| } |
| |
| |
| Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { |
| // Is it 'getelementptr %P, long 0' or 'getelementptr %P' |
| // If so, eliminate the noop. |
| if ((GEP.getNumOperands() == 2 && |
| GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) || |
| GEP.getNumOperands() == 1) |
| return ReplaceInstUsesWith(GEP, GEP.getOperand(0)); |
| |
| // Combine Indices - If the source pointer to this getelementptr instruction |
| // is a getelementptr instruction, combine the indices of the two |
| // getelementptr instructions into a single instruction. |
| // |
| if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) { |
| std::vector<Value *> Indices; |
| |
| // Can we combine the two pointer arithmetics offsets? |
| if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) && |
| isa<Constant>(GEP.getOperand(1))) { |
| // Replace: gep (gep %P, long C1), long C2, ... |
| // With: gep %P, long (C1+C2), ... |
| Value *Sum = ConstantExpr::get(Instruction::Add, |
| cast<Constant>(Src->getOperand(1)), |
| cast<Constant>(GEP.getOperand(1))); |
| assert(Sum && "Constant folding of longs failed!?"); |
| GEP.setOperand(0, Src->getOperand(0)); |
| GEP.setOperand(1, Sum); |
| AddUsesToWorkList(*Src); // Reduce use count of Src |
| return &GEP; |
| } else if (Src->getNumOperands() == 2) { |
| // Replace: gep (gep %P, long B), long A, ... |
| // With: T = long A+B; gep %P, T, ... |
| // |
| Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1), |
| GEP.getOperand(1), |
| Src->getName()+".sum", &GEP); |
| GEP.setOperand(0, Src->getOperand(0)); |
| GEP.setOperand(1, Sum); |
| WorkList.push_back(cast<Instruction>(Sum)); |
| return &GEP; |
| } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) && |
| Src->getNumOperands() != 1) { |
| // Otherwise we can do the fold if the first index of the GEP is a zero |
| Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()); |
| Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end()); |
| } else if (Src->getOperand(Src->getNumOperands()-1) == |
| Constant::getNullValue(Type::LongTy)) { |
| // If the src gep ends with a constant array index, merge this get into |
| // it, even if we have a non-zero array index. |
| Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1); |
| Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end()); |
| } |
| |
| if (!Indices.empty()) |
| return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName()); |
| |
| } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) { |
| // GEP of global variable. If all of the indices for this GEP are |
| // constants, we can promote this to a constexpr instead of an instruction. |
| |
| // Scan for nonconstants... |
| std::vector<Constant*> Indices; |
| User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end(); |
| for (; I != E && isa<Constant>(*I); ++I) |
| Indices.push_back(cast<Constant>(*I)); |
| |
| if (I == E) { // If they are all constants... |
| Constant *CE = |
| ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices); |
| |
| // Replace all uses of the GEP with the new constexpr... |
| return ReplaceInstUsesWith(GEP, CE); |
| } |
| } |
| |
| return 0; |
| } |
| |
| Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) { |
| // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1 |
| if (AI.isArrayAllocation()) // Check C != 1 |
| if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) { |
| const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue()); |
| AllocationInst *New = 0; |
| |
| // Create and insert the replacement instruction... |
| if (isa<MallocInst>(AI)) |
| New = new MallocInst(NewTy, 0, AI.getName(), &AI); |
| else { |
| assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!"); |
| New = new AllocaInst(NewTy, 0, AI.getName(), &AI); |
| } |
| |
| // Scan to the end of the allocation instructions, to skip over a block of |
| // allocas if possible... |
| // |
| BasicBlock::iterator It = New; |
| while (isa<AllocationInst>(*It)) ++It; |
| |
| // Now that I is pointing to the first non-allocation-inst in the block, |
| // insert our getelementptr instruction... |
| // |
| std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy)); |
| Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It); |
| |
| // Now make everything use the getelementptr instead of the original |
| // allocation. |
| ReplaceInstUsesWith(AI, V); |
| return &AI; |
| } |
| return 0; |
| } |
| |
| /// GetGEPGlobalInitializer - Given a constant, and a getelementptr |
| /// constantexpr, return the constant value being addressed by the constant |
| /// expression, or null if something is funny. |
| /// |
| static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) { |
| if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy)) |
| return 0; // Do not allow stepping over the value! |
| |
| // Loop over all of the operands, tracking down which value we are |
| // addressing... |
| for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i) |
| if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) { |
| ConstantStruct *CS = cast<ConstantStruct>(C); |
| if (CU->getValue() >= CS->getValues().size()) return 0; |
| C = cast<Constant>(CS->getValues()[CU->getValue()]); |
| } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) { |
| ConstantArray *CA = cast<ConstantArray>(C); |
| if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0; |
| C = cast<Constant>(CA->getValues()[CS->getValue()]); |
| } else |
| return 0; |
| return C; |
| } |
| |
| Instruction *InstCombiner::visitLoadInst(LoadInst &LI) { |
| Value *Op = LI.getOperand(0); |
| if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op)) |
| Op = CPR->getValue(); |
| |
| // Instcombine load (constant global) into the value loaded... |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op)) |
| if (GV->isConstant() && !GV->isExternal()) |
| return ReplaceInstUsesWith(LI, GV->getInitializer()); |
| |
| // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded... |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op)) |
| if (CE->getOpcode() == Instruction::GetElementPtr) |
| if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0))) |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue())) |
| if (GV->isConstant() && !GV->isExternal()) |
| if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE)) |
| return ReplaceInstUsesWith(LI, V); |
| return 0; |
| } |
| |
| |
| Instruction *InstCombiner::visitBranchInst(BranchInst &BI) { |
| // Change br (not X), label True, label False to: br X, label False, True |
| if (BI.isConditional() && !isa<Constant>(BI.getCondition())) |
| if (Value *V = dyn_castNotVal(BI.getCondition())) { |
| BasicBlock *TrueDest = BI.getSuccessor(0); |
| BasicBlock *FalseDest = BI.getSuccessor(1); |
| // Swap Destinations and condition... |
| BI.setCondition(V); |
| BI.setSuccessor(0, FalseDest); |
| BI.setSuccessor(1, TrueDest); |
| return &BI; |
| } |
| return 0; |
| } |
| |
| |
| void InstCombiner::removeFromWorkList(Instruction *I) { |
| WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I), |
| WorkList.end()); |
| } |
| |
| bool InstCombiner::runOnFunction(Function &F) { |
| bool Changed = false; |
| TD = &getAnalysis<TargetData>(); |
| |
| WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F)); |
| |
| while (!WorkList.empty()) { |
| Instruction *I = WorkList.back(); // Get an instruction from the worklist |
| WorkList.pop_back(); |
| |
| // Check to see if we can DCE or ConstantPropagate the instruction... |
| // Check to see if we can DIE the instruction... |
| if (isInstructionTriviallyDead(I)) { |
| // Add operands to the worklist... |
| if (I->getNumOperands() < 4) |
| for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) |
| if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i))) |
| WorkList.push_back(Op); |
| ++NumDeadInst; |
| |
| I->getParent()->getInstList().erase(I); |
| removeFromWorkList(I); |
| continue; |
| } |
| |
| // Instruction isn't dead, see if we can constant propagate it... |
| if (Constant *C = ConstantFoldInstruction(I)) { |
| // Add operands to the worklist... |
| for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) |
| if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i))) |
| WorkList.push_back(Op); |
| ReplaceInstUsesWith(*I, C); |
| |
| ++NumConstProp; |
| I->getParent()->getInstList().erase(I); |
| removeFromWorkList(I); |
| continue; |
| } |
| |
| // Now that we have an instruction, try combining it to simplify it... |
| if (Instruction *Result = visit(*I)) { |
| ++NumCombined; |
| // Should we replace the old instruction with a new one? |
| if (Result != I) { |
| // Instructions can end up on the worklist more than once. Make sure |
| // we do not process an instruction that has been deleted. |
| removeFromWorkList(I); |
| |
| // Move the name to the new instruction first... |
| std::string OldName = I->getName(); I->setName(""); |
| Result->setName(OldName); |
| |
| // Insert the new instruction into the basic block... |
| BasicBlock *InstParent = I->getParent(); |
| InstParent->getInstList().insert(I, Result); |
| |
| // Everything uses the new instruction now... |
| I->replaceAllUsesWith(Result); |
| |
| // Erase the old instruction. |
| InstParent->getInstList().erase(I); |
| } else { |
| BasicBlock::iterator II = I; |
| |
| // If the instruction was modified, it's possible that it is now dead. |
| // if so, remove it. |
| if (dceInstruction(II)) { |
| // Instructions may end up in the worklist more than once. Erase them |
| // all. |
| removeFromWorkList(I); |
| Result = 0; |
| } |
| } |
| |
| if (Result) { |
| WorkList.push_back(Result); |
| AddUsesToWorkList(*Result); |
| } |
| Changed = true; |
| } |
| } |
| |
| return Changed; |
| } |
| |
| Pass *createInstructionCombiningPass() { |
| return new InstCombiner(); |
| } |
| |
| } // End llvm namespace |