//===- 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/Intrinsics.h" #include "llvm/Pass.h" #include "llvm/Constants.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 using 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 { // Worklist of all of the instructions that need to be simplified. std::vector WorkList; TargetData *TD; /// AddUsersToWorkList - When an instruction is simplified, add all users of /// the instruction to the work lists because they might get more simplified /// now. /// void AddUsersToWorkList(Instruction &I) { for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; ++UI) WorkList.push_back(cast(*UI)); } /// AddUsesToWorkList - When an instruction is simplified, add operands to /// the work lists because they might get more simplified now. /// void AddUsesToWorkList(Instruction &I) { for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) if (Instruction *Op = dyn_cast(I.getOperand(i))) WorkList.push_back(Op); } // 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(); 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 *visitFreeInst(FreeInst &FI); 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. // Value *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 return New; } 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) { AddUsersToWorkList(I); // Add all modified instrs to worklist I.replaceAllUsesWith(V); return &I; } // EraseInstFromFunction - When dealing with an instruction that has side // effects or produces a void value, we can't rely on DCE to delete the // instruction. Instead, visit methods should return the value returned by // this function. Instruction *EraseInstFromFunction(Instruction &I) { assert(I.use_empty() && "Cannot erase instruction that is used!"); AddUsesToWorkList(I); removeFromWorkList(&I); I.getParent()->getInstList().erase(&I); return 0; // Don't do anything with FI } 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 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(V)) { if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V)) return 2; return 3; } if (isa(V)) return 2; return isa(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(V); } // getSignedIntegralType - Given an unsigned integral type, return the signed // version of it that has the same size. static const Type *getSignedIntegralType(const Type *Ty) { switch (Ty->getPrimitiveID()) { default: assert(0 && "Invalid unsigned integer type!"); abort(); case Type::UByteTyID: return Type::SByteTy; case Type::UShortTyID: return Type::ShortTy; case Type::UIntTyID: return Type::IntTy; case Type::ULongTyID: return Type::LongTy; } } // 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; } } // 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(I.getOperand(0))) if (Op->getOpcode() == Opcode && isa(Op->getOperand(1))) { if (isa(I.getOperand(1))) { Constant *Folded = ConstantExpr::get(I.getOpcode(), cast(I.getOperand(1)), cast(Op->getOperand(1))); I.setOperand(0, Op->getOperand(0)); I.setOperand(1, Folded); return true; } else if (BinaryOperator *Op1=dyn_cast(I.getOperand(1))) if (Op1->getOpcode() == Opcode && isa(Op1->getOperand(1)) && isOnlyUse(Op) && isOnlyUse(Op1)) { Constant *C1 = cast(Op->getOperand(1)); Constant *C2 = cast(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(V)); // Constants can be considered to be negated values if they can be folded... if (Constant *C = dyn_cast(V)) return ConstantExpr::get(Instruction::Sub, Constant::getNullValue(V->getType()), C); return 0; } static Constant *NotConstant(Constant *C) { return ConstantExpr::get(Instruction::Xor, C, ConstantIntegral::getAllOnesValue(C->getType())); } static inline Value *dyn_castNotVal(Value *V) { if (BinaryOperator::isNot(V)) return BinaryOperator::getNotArgument(cast(V)); // Constants can be considered to be not'ed values... if (ConstantIntegral *C = dyn_cast(V)) return NotConstant(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(V)) if (I->getOpcode() == Instruction::Mul) if (isa(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 static inline Constant *dyn_castMaskingAnd(ValueType *V) { if (Instruction *I = dyn_cast(V)) if (I->getOpcode() == Instruction::And) return dyn_cast(I->getOperand(1)); // If this is a constant, it acts just like we were masking with it. return dyn_cast(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 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(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(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(Root.getOperand(0)); Instruction *LastUse = &Root; while (TmpLHSI->getParent() == BB) { LastUse = TmpLHSI; TmpLHSI = cast(TmpLHSI->getOperand(0)); } // Loop over all of the instructions in other blocks, moving them into // the current one. Value *TmpLHS = TmpLHSI; do { TmpLHSI = cast(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(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(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(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 (!I.getType()->isFloatingPoint() && // -0 + +0 = +0, so it's not a noop 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(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(cast(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(cast(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(RHS)) { if (Instruction *ILHS = dyn_cast(LHS)) { switch (ILHS->getOpcode()) { case Instruction::Xor: // ~X + C --> (C-1) - X if (ConstantInt *XorRHS = dyn_cast(ILHS->getOperand(1))) if (XorRHS->isAllOnesValue()) return BinaryOperator::create(Instruction::Sub, ConstantExpr::get(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(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(Op1)), ConstantExpr::get(Instruction::Add, C, ConstantInt::get(I.getType(), 1))); } if (BinaryOperator *Op1I = dyn_cast(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 && !Op1I->getType()->isFloatingPoint()) { // 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(cast(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(cast(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; } /// isSignBitCheck - Given an exploded setcc instruction, return true if it is /// really just returns true if the most significant (sign) bit is set. static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) { if (RHS->getType()->isSigned()) { // True if source is LHS < 0 or LHS <= -1 return Opcode == Instruction::SetLT && RHS->isNullValue() || Opcode == Instruction::SetLE && RHS->isAllOnesValue(); } else { ConstantUInt *RHSC = cast(RHS); // True if source is LHS > 127 or LHS >= 128, where the constants depend on // the size of the integer type. if (Opcode == Instruction::SetGE) return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1); if (Opcode == Instruction::SetGT) return RHSC->getValue() == (1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1; } return false; } 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(I.getOperand(1))) { if (ConstantInt *CI = dyn_cast(Op1)) { // ((X << C1)*C2) == (X * (C2 << C1)) if (ShiftInst *SI = dyn_cast(Op0)) if (SI->getOpcode() == Instruction::Shl) if (Constant *ShOp = dyn_cast(SI->getOperand(1))) return BinaryOperator::create(Instruction::Mul, SI->getOperand(0), ConstantExpr::get(Instruction::Shl, 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(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(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); // If one of the operands of the multiply is a cast from a boolean value, then // we know the bool is either zero or one, so this is a 'masking' multiply. // See if we can simplify things based on how the boolean was originally // formed. CastInst *BoolCast = 0; if (CastInst *CI = dyn_cast(I.getOperand(0))) if (CI->getOperand(0)->getType() == Type::BoolTy) BoolCast = CI; if (!BoolCast) if (CastInst *CI = dyn_cast(I.getOperand(1))) if (CI->getOperand(0)->getType() == Type::BoolTy) BoolCast = CI; if (BoolCast) { if (SetCondInst *SCI = dyn_cast(BoolCast->getOperand(0))) { Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1); const Type *SCOpTy = SCIOp0->getType(); // If the setcc is true iff the sign bit of X is set, then convert this // multiply into a shift/and combination. if (isa(SCIOp1) && isSignBitCheck(SCI->getOpcode(), SCIOp0, cast(SCIOp1))) { // Shift the X value right to turn it into "all signbits". Constant *Amt = ConstantUInt::get(Type::UByteTy, SCOpTy->getPrimitiveSize()*8-1); if (SCIOp0->getType()->isUnsigned()) { const Type *NewTy = getSignedIntegralType(SCIOp0->getType()); SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy, SCIOp0->getName()), I); } Value *V = InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt, BoolCast->getOperand(0)->getName()+ ".mask"), I); // If the multiply type is not the same as the source type, sign extend // or truncate to the multiply type. if (I.getType() != V->getType()) V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I); Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0; return BinaryOperator::create(Instruction::And, V, OtherOp); } } } return Changed ? &I : 0; } Instruction *InstCombiner::visitDiv(BinaryOperator &I) { // div X, 1 == X if (ConstantInt *RHS = dyn_cast(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(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(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(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(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(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(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(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(C)) return CU->getValue() == 1; const ConstantSInt *CS = cast(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(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(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(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(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); Constant *Together = 0; if (!isa(Op)) Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS); switch (Op->getOpcode()) { case Instruction::Xor: if (Together->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, Together); } break; case Instruction::Or: // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0 if (Together->isNullValue()) return BinaryOperator::create(Instruction::And, X, AndRHS); else { 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(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(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 = ConstantExpr::get(Instruction::And, AndRHS, ConstantExpr::get(Instruction::Shl, 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 = ConstantExpr::get(Instruction::And, AndRHS, ConstantExpr::get(Instruction::Shr, 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(Op1)) { if (RHS->isAllOnesValue()) return ReplaceInstUsesWith(I, Op0); // Optimize a variety of ((val OP C1) & C2) combinations... if (isa(Op0) || isa(Op0)) { Instruction *Op0I = cast(Op0); Value *X = Op0I->getOperand(0); if (ConstantInt *Op0CI = dyn_cast(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(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(Op1)) { if (RHS->isAllOnesValue()) return ReplaceInstUsesWith(I, Op1); if (Instruction *Op0I = dyn_cast(Op0)) { // (X & C1) | C2 --> (X | C2) & (C1|C2) if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0)) if (ConstantInt *Op0CI = dyn_cast(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, ConstantExpr::get(Instruction::Or, RHS, Op0CI)); } // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2) if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0)) if (ConstantInt *Op0CI = dyn_cast(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, ConstantExpr::get(Instruction::And, Op0CI, NotConstant(RHS))); } } } // (A & C1)|(A & C2) == A & (C1|C2) if (Instruction *LHS = dyn_cast(Op0)) if (Instruction *RHS = dyn_cast(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), ConstantExpr::get(Instruction::Or, 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(I.getOperand(1))) if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS))) return R; return Changed ? &I : 0; } // XorSelf - Implements: X ^ X --> 0 struct XorSelf { Value *RHS; XorSelf(Value *rhs) : RHS(rhs) {} bool shouldApply(Value *LHS) const { return LHS == RHS; } Instruction *apply(BinaryOperator &Xor) const { return &Xor; } }; Instruction *InstCombiner::visitXor(BinaryOperator &I) { bool Changed = SimplifyCommutative(I); Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); // xor X, X = 0, even if X is nested in a sequence of Xor's. if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) { assert(Result == &I && "AssociativeOpt didn't work?"); return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); } if (ConstantIntegral *RHS = dyn_cast(Op1)) { // xor X, 0 == X if (RHS->isNullValue()) return ReplaceInstUsesWith(I, Op0); if (BinaryOperator *Op0I = dyn_cast(Op0)) { // xor (setcc A, B), true = not (setcc A, B) = setncc A, B if (SetCondInst *SCI = dyn_cast(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()) if (Constant *Op0I0C = dyn_cast(Op0I->getOperand(0))) { Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub, Constant::getNullValue(Op0I0C->getType()), Op0I0C); Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C, ConstantInt::get(I.getType(), 1)); return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1), ConstantRHS); } if (ConstantInt *Op0CI = dyn_cast(Op0I->getOperand(1))) switch (Op0I->getOpcode()) { case Instruction::Add: // ~(X-c) --> (-c-1)-X if (RHS->isAllOnesValue()) { Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub, Constant::getNullValue(Op0CI->getType()), Op0CI); return BinaryOperator::create(Instruction::Sub, ConstantExpr::get(Instruction::Sub, NegOp0CI, ConstantInt::get(I.getType(), 1)), Op0I->getOperand(0)); } break; case Instruction::And: // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0 if (ConstantExpr::get(Instruction::And, 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 (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS) return BinaryOperator::create(Instruction::And, Op0, NotConstant(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(Op1)) if (Op1I->getOpcode() == Instruction::Or) { if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B cast(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); } } else if (Op1I->getOpcode() == Instruction::Xor) { if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B return ReplaceInstUsesWith(I, Op1I->getOperand(1)); else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B return ReplaceInstUsesWith(I, Op1I->getOperand(0)); } if (Instruction *Op0I = dyn_cast(Op0)) if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) { if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B cast(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(NotB)); return BinaryOperator::create(Instruction::And, Op0I->getOperand(0), NotB); } } else if (Op0I->getOpcode() == Instruction::Xor) { if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B return ReplaceInstUsesWith(I, Op0I->getOperand(1)); else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B return ReplaceInstUsesWith(I, Op0I->getOperand(0)); } // (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(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 , 0 - Global/Stack value addresses are never null! if (isa(Op1) && (isa(Op0) || isa(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(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(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(BO->getOperand(1))) return BinaryOperator::create(I.getOpcode(), BO->getOperand(0), ConstantExpr::get(Instruction::Xor, 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(BO->getOperand(1))) { Constant *NotCI = NotConstant(CI); if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue()) return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE)); } break; case Instruction::And: if (ConstantInt *BOC = dyn_cast(BO->getOperand(1))) { // If bits are being compared against that are and'd out, then the // comparison can never succeed! if (!ConstantExpr::get(Instruction::And, CI, NotConstant(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 = getSignedIntegralType(BOC->getType()); 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; } } } else { // Not a SetEQ/SetNE // If the LHS is a cast from an integral value of the same size, if (CastInst *Cast = dyn_cast(Op0)) { Value *CastOp = Cast->getOperand(0); const Type *SrcTy = CastOp->getType(); unsigned SrcTySize = SrcTy->getPrimitiveSize(); if (SrcTy != Cast->getType() && SrcTy->isInteger() && SrcTySize == Cast->getType()->getPrimitiveSize()) { assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) && "Source and destination signednesses should differ!"); if (Cast->getType()->isSigned()) { // If this is a signed comparison, check for comparisons in the // vicinity of zero. if (I.getOpcode() == Instruction::SetLT && CI->isNullValue()) // X < 0 => x > 127 return BinaryOperator::create(Instruction::SetGT, CastOp, ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1)); else if (I.getOpcode() == Instruction::SetGT && cast(CI)->getValue() == -1) // X > -1 => x < 128 return BinaryOperator::create(Instruction::SetLT, CastOp, ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1))); } else { ConstantUInt *CUI = cast(CI); if (I.getOpcode() == Instruction::SetLT && CUI->getValue() == 1ULL << (SrcTySize*8-1)) // X < 128 => X > -1 return BinaryOperator::create(Instruction::SetGT, CastOp, ConstantSInt::get(SrcTy, -1)); else if (I.getOpcode() == Instruction::SetGT && CUI->getValue() == (1ULL << (SrcTySize*8-1))-1) // X > 127 => X < 0 return BinaryOperator::create(Instruction::SetLT, CastOp, Constant::getNullValue(SrcTy)); } } } } // 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)); } // If we still have a setle or setge instruction, turn it into the // appropriate setlt or setgt instruction. Since the border cases have // already been handled above, this requires little checking. // if (I.getOpcode() == Instruction::SetLE) return BinaryOperator::create(Instruction::SetLT, Op0, AddOne(CI)); if (I.getOpcode() == Instruction::SetGE) return BinaryOperator::create(Instruction::SetGT, Op0, SubOne(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(Op0)) { Value *CastOp0 = CI->getOperand(0); if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) && !isa(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(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(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(Op1), I); } return BinaryOperator::create(I.getOpcode(), Op0, Op1); } // Handle the special case of: setcc (cast bool to X), // 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(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(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(Op0)) if (CSI->isAllOnesValue()) return ReplaceInstUsesWith(I, CSI); if (ConstantUInt *CUI = dyn_cast(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) { if (!Op0->getType()->isSigned() || isLeftShift) return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType())); else { I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1)); return &I; } } // ((X*C1) << C2) == (X * (C1 << C2)) if (BinaryOperator *BO = dyn_cast(Op0)) if (BO->getOpcode() == Instruction::Mul && isLeftShift) if (Constant *BOOp = dyn_cast(BO->getOperand(1))) return BinaryOperator::create(Instruction::Mul, BO->getOperand(0), ConstantExpr::get(Instruction::Shl, 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(Op0)) if (ConstantInt *Op0C = dyn_cast(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 = ConstantExpr::get(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(Op0)) if (ConstantUInt *ShiftAmt1C = dyn_cast(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... if (Op0->getType()->getPrimitiveSize()*8 < Amt) Amt = Op0->getType()->getPrimitiveSize()*8; 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::get(Instruction::Shl, C, ShiftAmt1C); else C = ConstantExpr::get(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(V)) return false; if (const CastInst *CI = dyn_cast(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(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(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(Src)) { bool AllZeroOperands = true; for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i) if (!isa(GEP->getOperand(i)) || !cast(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(Src)) if (AI->hasOneUse() && !AI->isArrayAllocation()) if (const PointerType *PTy = dyn_cast(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(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(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(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(Op1))) { Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI); return new ShiftInst(Instruction::Shl, Op0c, Op1); } break; } } return 0; } // CallInst simplification // Instruction *InstCombiner::visitCallInst(CallInst &CI) { // Intrinsics cannot occur in an invoke, so handle them here instead of in // visitCallSite. if (Function *F = CI.getCalledFunction()) switch (F->getIntrinsicID()) { case Intrinsic::memmove: case Intrinsic::memcpy: case Intrinsic::memset: // memmove/cpy/set of zero bytes is a noop. if (Constant *NumBytes = dyn_cast(CI.getOperand(3))) { if (NumBytes->isNullValue()) return EraseInstFromFunction(CI); } break; default: break; } return visitCallSite(&CI); } // InvokeInst simplification // Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) { return visitCallSite(&II); } // 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(Callee->getType()); const FunctionType *FTy = cast(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(*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(CS.getCalledValue())) return false; ConstantExpr *CE = cast(CS.getCalledValue()); if (CE->getOpcode() != Instruction::Cast || !isa(CE->getOperand(0))) return false; ConstantPointerRef *CPR = cast(CE->getOperand(0)); if (!isa(CPR->getValue())) return false; Function *Callee = cast(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(); // Check to see if we are changing the return type... if (OldRetTy != FT->getReturnType()) { if (Callee->isExternal() && !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) && !Caller->use_empty()) return false; // Cannot transform this return value... // If the callsite is an invoke instruction, and the return value is used by // a PHI node in a successor, we cannot change the return type of the call // because there is no place to put the cast instruction (without breaking // the critical edge). Bail out in this case. if (!Caller->use_empty()) if (InvokeInst *II = dyn_cast(Caller)) for (Value::use_iterator UI = II->use_begin(), E = II->use_end(); UI != E; ++UI) if (PHINode *PN = dyn_cast(*UI)) if (PN->getParent() == II->getNormalDest() || PN->getParent() == II->getUnwindDest()) return false; } 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 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(Caller)) { NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(), 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(Caller)) { BasicBlock::iterator I = II->getNormalDest()->begin(); while (isa(I)) ++I; InsertNewInstBefore(NC, *I); } else { // Otherwise, it's a call, just insert cast right after the call instr InsertNewInstBefore(NC, *Caller); } AddUsersToWorkList(*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 (Value *V = hasConstantValue(&PN)) return ReplaceInstUsesWith(PN, V); // If the only user of this instruction is a cast instruction, and all of the // incoming values are constants, change this PHI to merge together the casted // constants. if (PN.hasOneUse()) if (CastInst *CI = dyn_cast(PN.use_back())) if (CI->getType() != PN.getType()) { // noop casts will be folded bool AllConstant = true; for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) if (!isa(PN.getIncomingValue(i))) { AllConstant = false; break; } if (AllConstant) { // Make a new PHI with all casted values. PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN); for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) { Constant *OldArg = cast(PN.getIncomingValue(i)); New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()), PN.getIncomingBlock(i)); } // Update the cast instruction. CI->setOperand(0, New); WorkList.push_back(CI); // revisit the cast instruction to fold. WorkList.push_back(New); // Make sure to revisit the new Phi return &PN; // PN is now dead! } } return 0; } Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { // Is it 'getelementptr %P, long 0' or 'getelementptr %P' // If so, eliminate the noop. if (GEP.getNumOperands() == 1) return ReplaceInstUsesWith(GEP, GEP.getOperand(0)); bool HasZeroPointerIndex = false; if (Constant *C = dyn_cast(GEP.getOperand(1))) HasZeroPointerIndex = C->isNullValue(); if (GEP.getNumOperands() == 2 && HasZeroPointerIndex) 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(GEP.getOperand(0))) { std::vector Indices; // Can we combine the two pointer arithmetics offsets? if (Src->getNumOperands() == 2 && isa(Src->getOperand(1)) && isa(GEP.getOperand(1))) { // Replace: gep (gep %P, long C1), long C2, ... // With: gep %P, long (C1+C2), ... Value *Sum = ConstantExpr::get(Instruction::Add, cast(Src->getOperand(1)), cast(GEP.getOperand(1))); assert(Sum && "Constant folding of longs failed!?"); GEP.setOperand(0, Src->getOperand(0)); GEP.setOperand(1, Sum); AddUsersToWorkList(*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, ... // // Note that if our source is a gep chain itself that we wait for that // chain to be resolved before we perform this transformation. This // avoids us creating a TON of code in some cases. // if (isa(Src->getOperand(0)) && cast(Src->getOperand(0))->getNumOperands() == 2) return 0; // Wait until our source is folded to completion. 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(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(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 Indices; User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end(); for (; I != E && isa(*I); ++I) Indices.push_back(cast(*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); } } else if (ConstantExpr *CE = dyn_cast(GEP.getOperand(0))) { if (CE->getOpcode() == Instruction::Cast) { if (HasZeroPointerIndex) { // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ... // into : GEP [10 x ubyte]* X, long 0, ... // // This occurs when the program declares an array extern like "int X[];" // Constant *X = CE->getOperand(0); const PointerType *CPTy = cast(CE->getType()); if (const PointerType *XTy = dyn_cast(X->getType())) if (const ArrayType *XATy = dyn_cast(XTy->getElementType())) if (const ArrayType *CATy = dyn_cast(CPTy->getElementType())) if (CATy->getElementType() == XATy->getElementType()) { // At this point, we know that the cast source type is a pointer // to an array of the same type as the destination pointer // array. Because the array type is never stepped over (there // is a leading zero) we can fold the cast into this GEP. GEP.setOperand(0, X); return &GEP; } } } } 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(AI.getArraySize())) { const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue()); AllocationInst *New = 0; // Create and insert the replacement instruction... if (isa(AI)) New = new MallocInst(NewTy, 0, AI.getName(), &AI); else { assert(isa(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(*It)) ++It; // Now that I is pointing to the first non-allocation-inst in the block, // insert our getelementptr instruction... // std::vector 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; } Instruction *InstCombiner::visitFreeInst(FreeInst &FI) { Value *Op = FI.getOperand(0); // Change free * (cast * X to *) into free * X if (CastInst *CI = dyn_cast(Op)) if (isa(CI->getOperand(0)->getType())) { FI.setOperand(0, CI->getOperand(0)); return &FI; } // If we have 'free null' delete the instruction. This can happen in stl code // when lots of inlining happens. if (isa(Op)) return EraseInstFromFunction(FI); 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(CE->getOperand(i))) { ConstantStruct *CS = dyn_cast(C); if (CS == 0) return 0; if (CU->getValue() >= CS->getValues().size()) return 0; C = cast(CS->getValues()[CU->getValue()]); } else if (ConstantSInt *CS = dyn_cast(CE->getOperand(i))) { ConstantArray *CA = dyn_cast(C); if (CA == 0) return 0; if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0; C = cast(CA->getValues()[CS->getValue()]); } else return 0; return C; } Instruction *InstCombiner::visitLoadInst(LoadInst &LI) { Value *Op = LI.getOperand(0); if (LI.isVolatile()) return 0; if (ConstantPointerRef *CPR = dyn_cast(Op)) Op = CPR->getValue(); // Instcombine load (constant global) into the value loaded... if (GlobalVariable *GV = dyn_cast(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(Op)) if (CE->getOpcode() == Instruction::GetElementPtr) if (ConstantPointerRef *G=dyn_cast(CE->getOperand(0))) if (GlobalVariable *GV = dyn_cast(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(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; } else if (SetCondInst *I = dyn_cast(BI.getCondition())) { // Cannonicalize setne -> seteq if ((I->getOpcode() == Instruction::SetNE || I->getOpcode() == Instruction::SetLE || I->getOpcode() == Instruction::SetGE) && I->hasOneUse()) { std::string Name = I->getName(); I->setName(""); Instruction::BinaryOps NewOpcode = SetCondInst::getInverseCondition(I->getOpcode()); Value *NewSCC = BinaryOperator::create(NewOpcode, I->getOperand(0), I->getOperand(1), Name, I); BasicBlock *TrueDest = BI.getSuccessor(0); BasicBlock *FalseDest = BI.getSuccessor(1); // Swap Destinations and condition... BI.setCondition(NewSCC); BI.setSuccessor(0, FalseDest); BI.setSuccessor(1, TrueDest); removeFromWorkList(I); I->getParent()->getInstList().erase(I); WorkList.push_back(cast(NewSCC)); 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(); 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) AddUsesToWorkList(*I); ++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... AddUsesToWorkList(*I); 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); AddUsersToWorkList(*Result); } Changed = true; } } return Changed; } Pass *llvm::createInstructionCombiningPass() { return new InstCombiner(); }