//===- InstCombineAddSub.cpp ----------------------------------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the visit functions for add, fadd, sub, and fsub. // //===----------------------------------------------------------------------===// #include "InstCombine.h" #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Target/TargetData.h" #include "llvm/Support/GetElementPtrTypeIterator.h" #include "llvm/Support/PatternMatch.h" using namespace llvm; using namespace PatternMatch; /// AddOne - Add one to a ConstantInt. static Constant *AddOne(Constant *C) { return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1)); } /// SubOne - Subtract one from a ConstantInt. static Constant *SubOne(ConstantInt *C) { return ConstantInt::get(C->getContext(), C->getValue()-1); } // 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, and set CST to point to the multiplier. // Otherwise, return null. // static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) { if (!V->hasOneUse() || !V->getType()->isInteger()) return 0; Instruction *I = dyn_cast(V); if (I == 0) return 0; if (I->getOpcode() == Instruction::Mul) if ((CST = dyn_cast(I->getOperand(1)))) return I->getOperand(0); if (I->getOpcode() == Instruction::Shl) if ((CST = dyn_cast(I->getOperand(1)))) { // The multiplier is really 1 << CST. uint32_t BitWidth = cast(V->getType())->getBitWidth(); uint32_t CSTVal = CST->getLimitedValue(BitWidth); CST = ConstantInt::get(V->getType()->getContext(), APInt(BitWidth, 1).shl(CSTVal)); return I->getOperand(0); } return 0; } /// WillNotOverflowSignedAdd - Return true if we can prove that: /// (sext (add LHS, RHS)) === (add (sext LHS), (sext RHS)) /// This basically requires proving that the add in the original type would not /// overflow to change the sign bit or have a carry out. bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS) { // There are different heuristics we can use for this. Here are some simple // ones. // Add has the property that adding any two 2's complement numbers can only // have one carry bit which can change a sign. As such, if LHS and RHS each // have at least two sign bits, we know that the addition of the two values // will sign extend fine. if (ComputeNumSignBits(LHS) > 1 && ComputeNumSignBits(RHS) > 1) return true; // If one of the operands only has one non-zero bit, and if the other operand // has a known-zero bit in a more significant place than it (not including the // sign bit) the ripple may go up to and fill the zero, but won't change the // sign. For example, (X & ~4) + 1. // TODO: Implement. return false; } Instruction *InstCombiner::visitAdd(BinaryOperator &I) { bool Changed = SimplifyCommutative(I); Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); if (Value *V = SimplifyAddInst(LHS, RHS, I.hasNoSignedWrap(), I.hasNoUnsignedWrap(), TD)) return ReplaceInstUsesWith(I, V); if (Constant *RHSC = dyn_cast(RHS)) { if (ConstantInt *CI = dyn_cast(RHSC)) { // X + (signbit) --> X ^ signbit const APInt& Val = CI->getValue(); uint32_t BitWidth = Val.getBitWidth(); if (Val == APInt::getSignBit(BitWidth)) return BinaryOperator::CreateXor(LHS, RHS); // See if SimplifyDemandedBits can simplify this. This handles stuff like // (X & 254)+1 -> (X&254)|1 if (SimplifyDemandedInstructionBits(I)) return &I; // zext(bool) + C -> bool ? C + 1 : C if (ZExtInst *ZI = dyn_cast(LHS)) if (ZI->getSrcTy() == Type::getInt1Ty(I.getContext())) return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI); } if (isa(LHS)) if (Instruction *NV = FoldOpIntoPhi(I)) return NV; ConstantInt *XorRHS = 0; Value *XorLHS = 0; if (isa(RHSC) && match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) { uint32_t TySizeBits = I.getType()->getScalarSizeInBits(); const APInt& RHSVal = cast(RHSC)->getValue(); uint32_t Size = TySizeBits / 2; APInt C0080Val(APInt(TySizeBits, 1ULL).shl(Size - 1)); APInt CFF80Val(-C0080Val); do { if (TySizeBits > Size) { // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext. // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext. if ((RHSVal == CFF80Val && XorRHS->getValue() == C0080Val) || (RHSVal == C0080Val && XorRHS->getValue() == CFF80Val)) { // This is a sign extend if the top bits are known zero. if (!MaskedValueIsZero(XorLHS, APInt::getHighBitsSet(TySizeBits, TySizeBits - Size))) Size = 0; // Not a sign ext, but can't be any others either. break; } } Size >>= 1; C0080Val = APIntOps::lshr(C0080Val, Size); CFF80Val = APIntOps::ashr(CFF80Val, Size); } while (Size >= 1); // FIXME: This shouldn't be necessary. When the backends can handle types // with funny bit widths then this switch statement should be removed. It // is just here to get the size of the "middle" type back up to something // that the back ends can handle. const Type *MiddleType = 0; switch (Size) { default: break; case 32: case 16: case 8: MiddleType = IntegerType::get(I.getContext(), Size); break; } if (MiddleType) { Value *NewTrunc = Builder->CreateTrunc(XorLHS, MiddleType, "sext"); return new SExtInst(NewTrunc, I.getType(), I.getName()); } } } if (I.getType()->isInteger(1)) return BinaryOperator::CreateXor(LHS, RHS); if (I.getType()->isInteger()) { // X + X --> X << 1 if (LHS == RHS) return BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1)); if (Instruction *RHSI = dyn_cast(RHS)) { if (RHSI->getOpcode() == Instruction::Sub) if (LHS == RHSI->getOperand(1)) // A + (B - A) --> B return ReplaceInstUsesWith(I, RHSI->getOperand(0)); } if (Instruction *LHSI = dyn_cast(LHS)) { if (LHSI->getOpcode() == Instruction::Sub) if (RHS == LHSI->getOperand(1)) // (B - A) + A --> B return ReplaceInstUsesWith(I, LHSI->getOperand(0)); } } // -A + B --> B - A // -A + -B --> -(A + B) if (Value *LHSV = dyn_castNegVal(LHS)) { if (LHS->getType()->isIntOrIntVector()) { if (Value *RHSV = dyn_castNegVal(RHS)) { Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum"); return BinaryOperator::CreateNeg(NewAdd); } } return BinaryOperator::CreateSub(RHS, LHSV); } // A + -B --> A - B if (!isa(RHS)) if (Value *V = dyn_castNegVal(RHS)) return BinaryOperator::CreateSub(LHS, V); ConstantInt *C2; if (Value *X = dyn_castFoldableMul(LHS, C2)) { if (X == RHS) // X*C + X --> X * (C+1) return BinaryOperator::CreateMul(RHS, AddOne(C2)); // X*C1 + X*C2 --> X * (C1+C2) ConstantInt *C1; if (X == dyn_castFoldableMul(RHS, C1)) return BinaryOperator::CreateMul(X, ConstantExpr::getAdd(C1, C2)); } // X + X*C --> X * (C+1) if (dyn_castFoldableMul(RHS, C2) == LHS) return BinaryOperator::CreateMul(LHS, AddOne(C2)); // X + ~X --> -1 since ~X = -X-1 if (match(LHS, m_Not(m_Specific(RHS))) || match(RHS, m_Not(m_Specific(LHS)))) return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType())); // A+B --> A|B iff A and B have no bits set in common. if (const IntegerType *IT = dyn_cast(I.getType())) { APInt Mask = APInt::getAllOnesValue(IT->getBitWidth()); APInt LHSKnownOne(IT->getBitWidth(), 0); APInt LHSKnownZero(IT->getBitWidth(), 0); ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne); if (LHSKnownZero != 0) { APInt RHSKnownOne(IT->getBitWidth(), 0); APInt RHSKnownZero(IT->getBitWidth(), 0); ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne); // No bits in common -> bitwise or. if ((LHSKnownZero|RHSKnownZero).isAllOnesValue()) return BinaryOperator::CreateOr(LHS, RHS); } } // W*X + Y*Z --> W * (X+Z) iff W == Y if (I.getType()->isIntOrIntVector()) { Value *W, *X, *Y, *Z; if (match(LHS, m_Mul(m_Value(W), m_Value(X))) && match(RHS, m_Mul(m_Value(Y), m_Value(Z)))) { if (W != Y) { if (W == Z) { std::swap(Y, Z); } else if (Y == X) { std::swap(W, X); } else if (X == Z) { std::swap(Y, Z); std::swap(W, X); } } if (W == Y) { Value *NewAdd = Builder->CreateAdd(X, Z, LHS->getName()); return BinaryOperator::CreateMul(W, NewAdd); } } } if (ConstantInt *CRHS = dyn_cast(RHS)) { Value *X = 0; if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X return BinaryOperator::CreateSub(SubOne(CRHS), X); // (X & FF00) + xx00 -> (X+xx00) & FF00 if (LHS->hasOneUse() && match(LHS, m_And(m_Value(X), m_ConstantInt(C2)))) { Constant *Anded = ConstantExpr::getAnd(CRHS, C2); if (Anded == CRHS) { // See if all bits from the first bit set in the Add RHS up are included // in the mask. First, get the rightmost bit. const APInt &AddRHSV = CRHS->getValue(); // Form a mask of all bits from the lowest bit added through the top. APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1)); // See if the and mask includes all of these bits. APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue()); if (AddRHSHighBits == AddRHSHighBitsAnd) { // Okay, the xform is safe. Insert the new add pronto. Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName()); return BinaryOperator::CreateAnd(NewAdd, C2); } } } // Try to fold constant add into select arguments. if (SelectInst *SI = dyn_cast(LHS)) if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; } // add (select X 0 (sub n A)) A --> select X A n { SelectInst *SI = dyn_cast(LHS); Value *A = RHS; if (!SI) { SI = dyn_cast(RHS); A = LHS; } if (SI && SI->hasOneUse()) { Value *TV = SI->getTrueValue(); Value *FV = SI->getFalseValue(); Value *N; // Can we fold the add into the argument of the select? // We check both true and false select arguments for a matching subtract. if (match(FV, m_Zero()) && match(TV, m_Sub(m_Value(N), m_Specific(A)))) // Fold the add into the true select value. return SelectInst::Create(SI->getCondition(), N, A); if (match(TV, m_Zero()) && match(FV, m_Sub(m_Value(N), m_Specific(A)))) // Fold the add into the false select value. return SelectInst::Create(SI->getCondition(), A, N); } } // Check for (add (sext x), y), see if we can merge this into an // integer add followed by a sext. if (SExtInst *LHSConv = dyn_cast(LHS)) { // (add (sext x), cst) --> (sext (add x, cst')) if (ConstantInt *RHSC = dyn_cast(RHS)) { Constant *CI = ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType()); if (LHSConv->hasOneUse() && ConstantExpr::getSExt(CI, I.getType()) == RHSC && WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) { // Insert the new, smaller add. Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), CI, "addconv"); return new SExtInst(NewAdd, I.getType()); } } // (add (sext x), (sext y)) --> (sext (add int x, y)) if (SExtInst *RHSConv = dyn_cast(RHS)) { // Only do this if x/y have the same type, if at last one of them has a // single use (so we don't increase the number of sexts), and if the // integer add will not overflow. if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&& (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && WillNotOverflowSignedAdd(LHSConv->getOperand(0), RHSConv->getOperand(0))) { // Insert the new integer add. Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), RHSConv->getOperand(0), "addconv"); return new SExtInst(NewAdd, I.getType()); } } } return Changed ? &I : 0; } Instruction *InstCombiner::visitFAdd(BinaryOperator &I) { bool Changed = SimplifyCommutative(I); Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); if (Constant *RHSC = dyn_cast(RHS)) { // X + 0 --> X if (ConstantFP *CFP = dyn_cast(RHSC)) { if (CFP->isExactlyValue(ConstantFP::getNegativeZero (I.getType())->getValueAPF())) return ReplaceInstUsesWith(I, LHS); } if (isa(LHS)) if (Instruction *NV = FoldOpIntoPhi(I)) return NV; } // -A + B --> B - A // -A + -B --> -(A + B) if (Value *LHSV = dyn_castFNegVal(LHS)) return BinaryOperator::CreateFSub(RHS, LHSV); // A + -B --> A - B if (!isa(RHS)) if (Value *V = dyn_castFNegVal(RHS)) return BinaryOperator::CreateFSub(LHS, V); // Check for X+0.0. Simplify it to X if we know X is not -0.0. if (ConstantFP *CFP = dyn_cast(RHS)) if (CFP->getValueAPF().isPosZero() && CannotBeNegativeZero(LHS)) return ReplaceInstUsesWith(I, LHS); // Check for (add double (sitofp x), y), see if we can merge this into an // integer add followed by a promotion. if (SIToFPInst *LHSConv = dyn_cast(LHS)) { // (add double (sitofp x), fpcst) --> (sitofp (add int x, intcst)) // ... if the constant fits in the integer value. This is useful for things // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer // requires a constant pool load, and generally allows the add to be better // instcombined. if (ConstantFP *CFP = dyn_cast(RHS)) { Constant *CI = ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType()); if (LHSConv->hasOneUse() && ConstantExpr::getSIToFP(CI, I.getType()) == CFP && WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) { // Insert the new integer add. Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), CI, "addconv"); return new SIToFPInst(NewAdd, I.getType()); } } // (add double (sitofp x), (sitofp y)) --> (sitofp (add int x, y)) if (SIToFPInst *RHSConv = dyn_cast(RHS)) { // Only do this if x/y have the same type, if at last one of them has a // single use (so we don't increase the number of int->fp conversions), // and if the integer add will not overflow. if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&& (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && WillNotOverflowSignedAdd(LHSConv->getOperand(0), RHSConv->getOperand(0))) { // Insert the new integer add. Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), RHSConv->getOperand(0),"addconv"); return new SIToFPInst(NewAdd, I.getType()); } } } return Changed ? &I : 0; } /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the /// code necessary to compute the offset from the base pointer (without adding /// in the base pointer). Return the result as a signed integer of intptr size. Value *InstCombiner::EmitGEPOffset(User *GEP) { TargetData &TD = *getTargetData(); gep_type_iterator GTI = gep_type_begin(GEP); const Type *IntPtrTy = TD.getIntPtrType(GEP->getContext()); Value *Result = Constant::getNullValue(IntPtrTy); // Build a mask for high order bits. unsigned IntPtrWidth = TD.getPointerSizeInBits(); uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth); for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e; ++i, ++GTI) { Value *Op = *i; uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask; if (ConstantInt *OpC = dyn_cast(Op)) { if (OpC->isZero()) continue; // Handle a struct index, which adds its field offset to the pointer. if (const StructType *STy = dyn_cast(*GTI)) { Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue()); Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size), GEP->getName()+".offs"); continue; } Constant *Scale = ConstantInt::get(IntPtrTy, Size); Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/); Scale = ConstantExpr::getMul(OC, Scale); // Emit an add instruction. Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs"); continue; } // Convert to correct type. if (Op->getType() != IntPtrTy) Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c"); if (Size != 1) { Constant *Scale = ConstantInt::get(IntPtrTy, Size); // We'll let instcombine(mul) convert this to a shl if possible. Op = Builder->CreateMul(Op, Scale, GEP->getName()+".idx"); } // Emit an add instruction. Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs"); } return Result; } /// Optimize pointer differences into the same array into a size. Consider: /// &A[10] - &A[0]: we should compile this to "10". LHS/RHS are the pointer /// operands to the ptrtoint instructions for the LHS/RHS of the subtract. /// Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS, const Type *Ty) { assert(TD && "Must have target data info for this"); // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize // this. bool Swapped = false; GetElementPtrInst *GEP = 0; ConstantExpr *CstGEP = 0; // TODO: Could also optimize &A[i] - &A[j] -> "i-j", and "&A.foo[i] - &A.foo". // For now we require one side to be the base pointer "A" or a constant // expression derived from it. if (GetElementPtrInst *LHSGEP = dyn_cast(LHS)) { // (gep X, ...) - X if (LHSGEP->getOperand(0) == RHS) { GEP = LHSGEP; Swapped = false; } else if (ConstantExpr *CE = dyn_cast(RHS)) { // (gep X, ...) - (ce_gep X, ...) if (CE->getOpcode() == Instruction::GetElementPtr && LHSGEP->getOperand(0) == CE->getOperand(0)) { CstGEP = CE; GEP = LHSGEP; Swapped = false; } } } if (GetElementPtrInst *RHSGEP = dyn_cast(RHS)) { // X - (gep X, ...) if (RHSGEP->getOperand(0) == LHS) { GEP = RHSGEP; Swapped = true; } else if (ConstantExpr *CE = dyn_cast(LHS)) { // (ce_gep X, ...) - (gep X, ...) if (CE->getOpcode() == Instruction::GetElementPtr && RHSGEP->getOperand(0) == CE->getOperand(0)) { CstGEP = CE; GEP = RHSGEP; Swapped = true; } } } if (GEP == 0) return 0; // Emit the offset of the GEP and an intptr_t. Value *Result = EmitGEPOffset(GEP); // If we had a constant expression GEP on the other side offsetting the // pointer, subtract it from the offset we have. if (CstGEP) { Value *CstOffset = EmitGEPOffset(CstGEP); Result = Builder->CreateSub(Result, CstOffset); } // If we have p - gep(p, ...) then we have to negate the result. if (Swapped) Result = Builder->CreateNeg(Result, "diff.neg"); return Builder->CreateIntCast(Result, Ty, true); } 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. This preserves NSW/NUW. if (Value *V = dyn_castNegVal(Op1)) { BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V); Res->setHasNoSignedWrap(I.hasNoSignedWrap()); Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); return Res; } if (isa(Op0)) return ReplaceInstUsesWith(I, Op0); // undef - X -> undef if (isa(Op1)) return ReplaceInstUsesWith(I, Op1); // X - undef -> undef if (I.getType()->isInteger(1)) return BinaryOperator::CreateXor(Op0, Op1); if (ConstantInt *C = dyn_cast(Op0)) { // Replace (-1 - A) with (~A). if (C->isAllOnesValue()) return BinaryOperator::CreateNot(Op1); // C - ~X == X + (1+C) Value *X = 0; if (match(Op1, m_Not(m_Value(X)))) return BinaryOperator::CreateAdd(X, AddOne(C)); // -(X >>u 31) -> (X >>s 31) // -(X >>s 31) -> (X >>u 31) if (C->isZero()) { if (BinaryOperator *SI = dyn_cast(Op1)) { if (SI->getOpcode() == Instruction::LShr) { if (ConstantInt *CU = dyn_cast(SI->getOperand(1))) { // Check to see if we are shifting out everything but the sign bit. if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) == SI->getType()->getPrimitiveSizeInBits()-1) { // Ok, the transformation is safe. Insert AShr. return BinaryOperator::Create(Instruction::AShr, SI->getOperand(0), CU, SI->getName()); } } } else if (SI->getOpcode() == Instruction::AShr) { if (ConstantInt *CU = dyn_cast(SI->getOperand(1))) { // Check to see if we are shifting out everything but the sign bit. if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) == SI->getType()->getPrimitiveSizeInBits()-1) { // Ok, the transformation is safe. Insert LShr. return BinaryOperator::CreateLShr( SI->getOperand(0), CU, SI->getName()); } } } } } // Try to fold constant sub into select arguments. if (SelectInst *SI = dyn_cast(Op1)) if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; // C - zext(bool) -> bool ? C - 1 : C if (ZExtInst *ZI = dyn_cast(Op1)) if (ZI->getSrcTy() == Type::getInt1Ty(I.getContext())) return SelectInst::Create(ZI->getOperand(0), SubOne(C), C); } if (BinaryOperator *Op1I = dyn_cast(Op1)) { if (Op1I->getOpcode() == Instruction::Add) { if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y return BinaryOperator::CreateNeg(Op1I->getOperand(1), I.getName()); else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y return BinaryOperator::CreateNeg(Op1I->getOperand(0), I.getName()); else if (ConstantInt *CI1 = dyn_cast(I.getOperand(0))) { if (ConstantInt *CI2 = dyn_cast(Op1I->getOperand(1))) // C1-(X+C2) --> (C1-C2)-X return BinaryOperator::CreateSub( ConstantExpr::getSub(CI1, CI2), Op1I->getOperand(0)); } } if (Op1I->hasOneUse()) { // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression // is not used by anyone else... // if (Op1I->getOpcode() == Instruction::Sub) { // Swap the two operands of the subexpr... Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1); Op1I->setOperand(0, IIOp1); Op1I->setOperand(1, IIOp0); // Create the new top level add instruction... return BinaryOperator::CreateAdd(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); Value *NewNot = Builder->CreateNot(OtherOp, "B.not"); return BinaryOperator::CreateAnd(Op0, NewNot); } // 0 - (X sdiv C) -> (X sdiv -C) if (Op1I->getOpcode() == Instruction::SDiv) if (ConstantInt *CSI = dyn_cast(Op0)) if (CSI->isZero()) if (Constant *DivRHS = dyn_cast(Op1I->getOperand(1))) return BinaryOperator::CreateSDiv(Op1I->getOperand(0), ConstantExpr::getNeg(DivRHS)); // X - X*C --> X * (1-C) ConstantInt *C2 = 0; if (dyn_castFoldableMul(Op1I, C2) == Op0) { Constant *CP1 = ConstantExpr::getSub(ConstantInt::get(I.getType(), 1), C2); return BinaryOperator::CreateMul(Op0, CP1); } } } if (BinaryOperator *Op0I = dyn_cast(Op0)) { if (Op0I->getOpcode() == Instruction::Add) { if (Op0I->getOperand(0) == Op1) // (Y+X)-Y == X return ReplaceInstUsesWith(I, Op0I->getOperand(1)); else if (Op0I->getOperand(1) == Op1) // (X+Y)-Y == X return ReplaceInstUsesWith(I, Op0I->getOperand(0)); } else if (Op0I->getOpcode() == Instruction::Sub) { if (Op0I->getOperand(0) == Op1) // (X-Y)-X == -Y return BinaryOperator::CreateNeg(Op0I->getOperand(1), I.getName()); } } ConstantInt *C1; if (Value *X = dyn_castFoldableMul(Op0, C1)) { if (X == Op1) // X*C - X --> X * (C-1) return BinaryOperator::CreateMul(Op1, SubOne(C1)); ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2) if (X == dyn_castFoldableMul(Op1, C2)) return BinaryOperator::CreateMul(X, ConstantExpr::getSub(C1, C2)); } // Optimize pointer differences into the same array into a size. Consider: // &A[10] - &A[0]: we should compile this to "10". if (TD) { Value *LHSOp, *RHSOp; if (match(Op0, m_PtrToInt(m_Value(LHSOp))) && match(Op1, m_PtrToInt(m_Value(RHSOp)))) if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType())) return ReplaceInstUsesWith(I, Res); // trunc(p)-trunc(q) -> trunc(p-q) if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) && match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp))))) if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType())) return ReplaceInstUsesWith(I, Res); } return 0; } Instruction *InstCombiner::visitFSub(BinaryOperator &I) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); // If this is a 'B = x-(-A)', change to B = x+A... if (Value *V = dyn_castFNegVal(Op1)) return BinaryOperator::CreateFAdd(Op0, V); return 0; }