| //===- InstructionSimplify.cpp - Fold instruction operands ----------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements routines for folding instructions into simpler forms |
| // that do not require creating new instructions. For example, this does |
| // constant folding, and can handle identities like (X&0)->0. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Support/ValueHandle.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Support/PatternMatch.h" |
| using namespace llvm; |
| using namespace llvm::PatternMatch; |
| |
| /// SimplifyAddInst - Given operands for an Add, see if we can |
| /// fold the result. If not, this returns null. |
| Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, |
| const TargetData *TD) { |
| if (Constant *CLHS = dyn_cast<Constant>(Op0)) { |
| if (Constant *CRHS = dyn_cast<Constant>(Op1)) { |
| Constant *Ops[] = { CLHS, CRHS }; |
| return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(), |
| Ops, 2, TD); |
| } |
| |
| // Canonicalize the constant to the RHS. |
| std::swap(Op0, Op1); |
| } |
| |
| if (Constant *Op1C = dyn_cast<Constant>(Op1)) { |
| // X + undef -> undef |
| if (isa<UndefValue>(Op1C)) |
| return Op1C; |
| |
| // X + 0 --> X |
| if (Op1C->isNullValue()) |
| return Op0; |
| } |
| |
| // FIXME: Could pull several more out of instcombine. |
| return 0; |
| } |
| |
| /// SimplifyAndInst - Given operands for an And, see if we can |
| /// fold the result. If not, this returns null. |
| Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD) { |
| if (Constant *CLHS = dyn_cast<Constant>(Op0)) { |
| if (Constant *CRHS = dyn_cast<Constant>(Op1)) { |
| Constant *Ops[] = { CLHS, CRHS }; |
| return ConstantFoldInstOperands(Instruction::And, CLHS->getType(), |
| Ops, 2, TD); |
| } |
| |
| // Canonicalize the constant to the RHS. |
| std::swap(Op0, Op1); |
| } |
| |
| // X & undef -> 0 |
| if (isa<UndefValue>(Op1)) |
| return Constant::getNullValue(Op0->getType()); |
| |
| // X & X = X |
| if (Op0 == Op1) |
| return Op0; |
| |
| // X & <0,0> = <0,0> |
| if (isa<ConstantAggregateZero>(Op1)) |
| return Op1; |
| |
| // X & <-1,-1> = X |
| if (ConstantVector *CP = dyn_cast<ConstantVector>(Op1)) |
| if (CP->isAllOnesValue()) |
| return Op0; |
| |
| if (ConstantInt *Op1CI = dyn_cast<ConstantInt>(Op1)) { |
| // X & 0 = 0 |
| if (Op1CI->isZero()) |
| return Op1CI; |
| // X & -1 = X |
| if (Op1CI->isAllOnesValue()) |
| return Op0; |
| } |
| |
| // A & ~A = ~A & A = 0 |
| Value *A, *B; |
| if ((match(Op0, m_Not(m_Value(A))) && A == Op1) || |
| (match(Op1, m_Not(m_Value(A))) && A == Op0)) |
| return Constant::getNullValue(Op0->getType()); |
| |
| // (A | ?) & A = A |
| if (match(Op0, m_Or(m_Value(A), m_Value(B))) && |
| (A == Op1 || B == Op1)) |
| return Op1; |
| |
| // A & (A | ?) = A |
| if (match(Op1, m_Or(m_Value(A), m_Value(B))) && |
| (A == Op0 || B == Op0)) |
| return Op0; |
| |
| return 0; |
| } |
| |
| /// SimplifyOrInst - Given operands for an Or, see if we can |
| /// fold the result. If not, this returns null. |
| Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD) { |
| if (Constant *CLHS = dyn_cast<Constant>(Op0)) { |
| if (Constant *CRHS = dyn_cast<Constant>(Op1)) { |
| Constant *Ops[] = { CLHS, CRHS }; |
| return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(), |
| Ops, 2, TD); |
| } |
| |
| // Canonicalize the constant to the RHS. |
| std::swap(Op0, Op1); |
| } |
| |
| // X | undef -> -1 |
| if (isa<UndefValue>(Op1)) |
| return Constant::getAllOnesValue(Op0->getType()); |
| |
| // X | X = X |
| if (Op0 == Op1) |
| return Op0; |
| |
| // X | <0,0> = X |
| if (isa<ConstantAggregateZero>(Op1)) |
| return Op0; |
| |
| // X | <-1,-1> = <-1,-1> |
| if (ConstantVector *CP = dyn_cast<ConstantVector>(Op1)) |
| if (CP->isAllOnesValue()) |
| return Op1; |
| |
| if (ConstantInt *Op1CI = dyn_cast<ConstantInt>(Op1)) { |
| // X | 0 = X |
| if (Op1CI->isZero()) |
| return Op0; |
| // X | -1 = -1 |
| if (Op1CI->isAllOnesValue()) |
| return Op1CI; |
| } |
| |
| // A | ~A = ~A | A = -1 |
| Value *A, *B; |
| if ((match(Op0, m_Not(m_Value(A))) && A == Op1) || |
| (match(Op1, m_Not(m_Value(A))) && A == Op0)) |
| return Constant::getAllOnesValue(Op0->getType()); |
| |
| // (A & ?) | A = A |
| if (match(Op0, m_And(m_Value(A), m_Value(B))) && |
| (A == Op1 || B == Op1)) |
| return Op1; |
| |
| // A | (A & ?) = A |
| if (match(Op1, m_And(m_Value(A), m_Value(B))) && |
| (A == Op0 || B == Op0)) |
| return Op0; |
| |
| return 0; |
| } |
| |
| |
| static const Type *GetCompareTy(Value *Op) { |
| return CmpInst::makeCmpResultType(Op->getType()); |
| } |
| |
| |
| /// SimplifyICmpInst - Given operands for an ICmpInst, see if we can |
| /// fold the result. If not, this returns null. |
| Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, |
| const TargetData *TD) { |
| CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; |
| assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!"); |
| |
| if (Constant *CLHS = dyn_cast<Constant>(LHS)) { |
| if (Constant *CRHS = dyn_cast<Constant>(RHS)) |
| return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD); |
| |
| // If we have a constant, make sure it is on the RHS. |
| std::swap(LHS, RHS); |
| Pred = CmpInst::getSwappedPredicate(Pred); |
| } |
| |
| // ITy - This is the return type of the compare we're considering. |
| const Type *ITy = GetCompareTy(LHS); |
| |
| // icmp X, X -> true/false |
| // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false |
| // because X could be 0. |
| if (LHS == RHS || isa<UndefValue>(RHS)) |
| return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred)); |
| |
| // icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value |
| // addresses never equal each other! We already know that Op0 != Op1. |
| if ((isa<GlobalValue>(LHS) || isa<AllocaInst>(LHS) || |
| isa<ConstantPointerNull>(LHS)) && |
| (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) || |
| isa<ConstantPointerNull>(RHS))) |
| return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred)); |
| |
| // See if we are doing a comparison with a constant. |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { |
| // If we have an icmp le or icmp ge instruction, turn it into the |
| // appropriate icmp lt or icmp gt instruction. This allows us to rely on |
| // them being folded in the code below. |
| switch (Pred) { |
| default: break; |
| case ICmpInst::ICMP_ULE: |
| if (CI->isMaxValue(false)) // A <=u MAX -> TRUE |
| return ConstantInt::getTrue(CI->getContext()); |
| break; |
| case ICmpInst::ICMP_SLE: |
| if (CI->isMaxValue(true)) // A <=s MAX -> TRUE |
| return ConstantInt::getTrue(CI->getContext()); |
| break; |
| case ICmpInst::ICMP_UGE: |
| if (CI->isMinValue(false)) // A >=u MIN -> TRUE |
| return ConstantInt::getTrue(CI->getContext()); |
| break; |
| case ICmpInst::ICMP_SGE: |
| if (CI->isMinValue(true)) // A >=s MIN -> TRUE |
| return ConstantInt::getTrue(CI->getContext()); |
| break; |
| } |
| } |
| |
| |
| return 0; |
| } |
| |
| /// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can |
| /// fold the result. If not, this returns null. |
| Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, |
| const TargetData *TD) { |
| CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; |
| assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!"); |
| |
| if (Constant *CLHS = dyn_cast<Constant>(LHS)) { |
| if (Constant *CRHS = dyn_cast<Constant>(RHS)) |
| return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD); |
| |
| // If we have a constant, make sure it is on the RHS. |
| std::swap(LHS, RHS); |
| Pred = CmpInst::getSwappedPredicate(Pred); |
| } |
| |
| // Fold trivial predicates. |
| if (Pred == FCmpInst::FCMP_FALSE) |
| return ConstantInt::get(GetCompareTy(LHS), 0); |
| if (Pred == FCmpInst::FCMP_TRUE) |
| return ConstantInt::get(GetCompareTy(LHS), 1); |
| |
| if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef |
| return UndefValue::get(GetCompareTy(LHS)); |
| |
| // fcmp x,x -> true/false. Not all compares are foldable. |
| if (LHS == RHS) { |
| if (CmpInst::isTrueWhenEqual(Pred)) |
| return ConstantInt::get(GetCompareTy(LHS), 1); |
| if (CmpInst::isFalseWhenEqual(Pred)) |
| return ConstantInt::get(GetCompareTy(LHS), 0); |
| } |
| |
| // Handle fcmp with constant RHS |
| if (Constant *RHSC = dyn_cast<Constant>(RHS)) { |
| // If the constant is a nan, see if we can fold the comparison based on it. |
| if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) { |
| if (CFP->getValueAPF().isNaN()) { |
| if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo" |
| return ConstantInt::getFalse(CFP->getContext()); |
| assert(FCmpInst::isUnordered(Pred) && |
| "Comparison must be either ordered or unordered!"); |
| // True if unordered. |
| return ConstantInt::getTrue(CFP->getContext()); |
| } |
| // Check whether the constant is an infinity. |
| if (CFP->getValueAPF().isInfinity()) { |
| if (CFP->getValueAPF().isNegative()) { |
| switch (Pred) { |
| case FCmpInst::FCMP_OLT: |
| // No value is ordered and less than negative infinity. |
| return ConstantInt::getFalse(CFP->getContext()); |
| case FCmpInst::FCMP_UGE: |
| // All values are unordered with or at least negative infinity. |
| return ConstantInt::getTrue(CFP->getContext()); |
| default: |
| break; |
| } |
| } else { |
| switch (Pred) { |
| case FCmpInst::FCMP_OGT: |
| // No value is ordered and greater than infinity. |
| return ConstantInt::getFalse(CFP->getContext()); |
| case FCmpInst::FCMP_ULE: |
| // All values are unordered with and at most infinity. |
| return ConstantInt::getTrue(CFP->getContext()); |
| default: |
| break; |
| } |
| } |
| } |
| } |
| } |
| |
| return 0; |
| } |
| |
| /// SimplifySelectInst - Given operands for a SelectInst, see if we can fold |
| /// the result. If not, this returns null. |
| Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal, |
| const TargetData *TD) { |
| // select true, X, Y -> X |
| // select false, X, Y -> Y |
| if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal)) |
| return CB->getZExtValue() ? TrueVal : FalseVal; |
| |
| // select C, X, X -> X |
| if (TrueVal == FalseVal) |
| return TrueVal; |
| |
| if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X |
| return FalseVal; |
| if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X |
| return TrueVal; |
| if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y |
| if (isa<Constant>(TrueVal)) |
| return TrueVal; |
| return FalseVal; |
| } |
| |
| |
| |
| return 0; |
| } |
| |
| |
| /// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can |
| /// fold the result. If not, this returns null. |
| Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps, |
| const TargetData *TD) { |
| // getelementptr P -> P. |
| if (NumOps == 1) |
| return Ops[0]; |
| |
| // TODO. |
| //if (isa<UndefValue>(Ops[0])) |
| // return UndefValue::get(GEP.getType()); |
| |
| // getelementptr P, 0 -> P. |
| if (NumOps == 2) |
| if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1])) |
| if (C->isZero()) |
| return Ops[0]; |
| |
| // Check to see if this is constant foldable. |
| for (unsigned i = 0; i != NumOps; ++i) |
| if (!isa<Constant>(Ops[i])) |
| return 0; |
| |
| return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]), |
| (Constant *const*)Ops+1, NumOps-1); |
| } |
| |
| |
| //=== Helper functions for higher up the class hierarchy. |
| |
| /// SimplifyBinOp - Given operands for a BinaryOperator, see if we can |
| /// fold the result. If not, this returns null. |
| Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, |
| const TargetData *TD) { |
| switch (Opcode) { |
| case Instruction::And: return SimplifyAndInst(LHS, RHS, TD); |
| case Instruction::Or: return SimplifyOrInst(LHS, RHS, TD); |
| default: |
| if (Constant *CLHS = dyn_cast<Constant>(LHS)) |
| if (Constant *CRHS = dyn_cast<Constant>(RHS)) { |
| Constant *COps[] = {CLHS, CRHS}; |
| return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, 2, TD); |
| } |
| return 0; |
| } |
| } |
| |
| /// SimplifyCmpInst - Given operands for a CmpInst, see if we can |
| /// fold the result. |
| Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, |
| const TargetData *TD) { |
| if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate)) |
| return SimplifyICmpInst(Predicate, LHS, RHS, TD); |
| return SimplifyFCmpInst(Predicate, LHS, RHS, TD); |
| } |
| |
| |
| /// SimplifyInstruction - See if we can compute a simplified version of this |
| /// instruction. If not, this returns null. |
| Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) { |
| switch (I->getOpcode()) { |
| default: |
| return ConstantFoldInstruction(I, TD); |
| case Instruction::Add: |
| return SimplifyAddInst(I->getOperand(0), I->getOperand(1), |
| cast<BinaryOperator>(I)->hasNoSignedWrap(), |
| cast<BinaryOperator>(I)->hasNoUnsignedWrap(), TD); |
| case Instruction::And: |
| return SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD); |
| case Instruction::Or: |
| return SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD); |
| case Instruction::ICmp: |
| return SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(), |
| I->getOperand(0), I->getOperand(1), TD); |
| case Instruction::FCmp: |
| return SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(), |
| I->getOperand(0), I->getOperand(1), TD); |
| case Instruction::Select: |
| return SimplifySelectInst(I->getOperand(0), I->getOperand(1), |
| I->getOperand(2), TD); |
| case Instruction::GetElementPtr: { |
| SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end()); |
| return SimplifyGEPInst(&Ops[0], Ops.size(), TD); |
| } |
| } |
| } |
| |
| /// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then |
| /// delete the From instruction. In addition to a basic RAUW, this does a |
| /// recursive simplification of the newly formed instructions. This catches |
| /// things where one simplification exposes other opportunities. This only |
| /// simplifies and deletes scalar operations, it does not change the CFG. |
| /// |
| void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To, |
| const TargetData *TD) { |
| assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!"); |
| |
| // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that |
| // we can know if it gets deleted out from under us or replaced in a |
| // recursive simplification. |
| WeakVH FromHandle(From); |
| WeakVH ToHandle(To); |
| |
| while (!From->use_empty()) { |
| // Update the instruction to use the new value. |
| Use &TheUse = From->use_begin().getUse(); |
| Instruction *User = cast<Instruction>(TheUse.getUser()); |
| TheUse = To; |
| |
| // Check to see if the instruction can be folded due to the operand |
| // replacement. For example changing (or X, Y) into (or X, -1) can replace |
| // the 'or' with -1. |
| Value *SimplifiedVal; |
| { |
| // Sanity check to make sure 'User' doesn't dangle across |
| // SimplifyInstruction. |
| AssertingVH<> UserHandle(User); |
| |
| SimplifiedVal = SimplifyInstruction(User, TD); |
| if (SimplifiedVal == 0) continue; |
| } |
| |
| // Recursively simplify this user to the new value. |
| ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD); |
| From = dyn_cast_or_null<Instruction>((Value*)FromHandle); |
| To = ToHandle; |
| |
| assert(ToHandle && "To value deleted by recursive simplification?"); |
| |
| // If the recursive simplification ended up revisiting and deleting |
| // 'From' then we're done. |
| if (From == 0) |
| return; |
| } |
| |
| // If 'From' has value handles referring to it, do a real RAUW to update them. |
| From->replaceAllUsesWith(To); |
| |
| From->eraseFromParent(); |
| } |
| |
