| //===- InstCombineSelect.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 visitSelect function. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "InstCombine.h" |
| #include "llvm/Support/PatternMatch.h" |
| using namespace llvm; |
| using namespace PatternMatch; |
| |
| /// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms, |
| /// returning the kind and providing the out parameter results if we |
| /// successfully match. |
| static SelectPatternFlavor |
| MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) { |
| SelectInst *SI = dyn_cast<SelectInst>(V); |
| if (SI == 0) return SPF_UNKNOWN; |
| |
| ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition()); |
| if (ICI == 0) return SPF_UNKNOWN; |
| |
| LHS = ICI->getOperand(0); |
| RHS = ICI->getOperand(1); |
| |
| // (icmp X, Y) ? X : Y |
| if (SI->getTrueValue() == ICI->getOperand(0) && |
| SI->getFalseValue() == ICI->getOperand(1)) { |
| switch (ICI->getPredicate()) { |
| default: return SPF_UNKNOWN; // Equality. |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_UGE: return SPF_UMAX; |
| case ICmpInst::ICMP_SGT: |
| case ICmpInst::ICMP_SGE: return SPF_SMAX; |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_ULE: return SPF_UMIN; |
| case ICmpInst::ICMP_SLT: |
| case ICmpInst::ICMP_SLE: return SPF_SMIN; |
| } |
| } |
| |
| // (icmp X, Y) ? Y : X |
| if (SI->getTrueValue() == ICI->getOperand(1) && |
| SI->getFalseValue() == ICI->getOperand(0)) { |
| switch (ICI->getPredicate()) { |
| default: return SPF_UNKNOWN; // Equality. |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_UGE: return SPF_UMIN; |
| case ICmpInst::ICMP_SGT: |
| case ICmpInst::ICMP_SGE: return SPF_SMIN; |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_ULE: return SPF_UMAX; |
| case ICmpInst::ICMP_SLT: |
| case ICmpInst::ICMP_SLE: return SPF_SMAX; |
| } |
| } |
| |
| // TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5) |
| |
| return SPF_UNKNOWN; |
| } |
| |
| |
| /// GetSelectFoldableOperands - We want to turn code that looks like this: |
| /// %C = or %A, %B |
| /// %D = select %cond, %C, %A |
| /// into: |
| /// %C = select %cond, %B, 0 |
| /// %D = or %A, %C |
| /// |
| /// Assuming that the specified instruction is an operand to the select, return |
| /// a bitmask indicating which operands of this instruction are foldable if they |
| /// equal the other incoming value of the select. |
| /// |
| static unsigned GetSelectFoldableOperands(Instruction *I) { |
| switch (I->getOpcode()) { |
| case Instruction::Add: |
| case Instruction::Mul: |
| case Instruction::And: |
| case Instruction::Or: |
| case Instruction::Xor: |
| return 3; // Can fold through either operand. |
| case Instruction::Sub: // Can only fold on the amount subtracted. |
| case Instruction::Shl: // Can only fold on the shift amount. |
| case Instruction::LShr: |
| case Instruction::AShr: |
| return 1; |
| default: |
| return 0; // Cannot fold |
| } |
| } |
| |
| /// GetSelectFoldableConstant - For the same transformation as the previous |
| /// function, return the identity constant that goes into the select. |
| static Constant *GetSelectFoldableConstant(Instruction *I) { |
| switch (I->getOpcode()) { |
| default: llvm_unreachable("This cannot happen!"); |
| case Instruction::Add: |
| case Instruction::Sub: |
| case Instruction::Or: |
| case Instruction::Xor: |
| case Instruction::Shl: |
| case Instruction::LShr: |
| case Instruction::AShr: |
| return Constant::getNullValue(I->getType()); |
| case Instruction::And: |
| return Constant::getAllOnesValue(I->getType()); |
| case Instruction::Mul: |
| return ConstantInt::get(I->getType(), 1); |
| } |
| } |
| |
| /// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI |
| /// have the same opcode and only one use each. Try to simplify this. |
| Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI, |
| Instruction *FI) { |
| if (TI->getNumOperands() == 1) { |
| // If this is a non-volatile load or a cast from the same type, |
| // merge. |
| if (TI->isCast()) { |
| if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType()) |
| return 0; |
| } else { |
| return 0; // unknown unary op. |
| } |
| |
| // Fold this by inserting a select from the input values. |
| SelectInst *NewSI = SelectInst::Create(SI.getCondition(), TI->getOperand(0), |
| FI->getOperand(0), SI.getName()+".v"); |
| InsertNewInstBefore(NewSI, SI); |
| return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI, |
| TI->getType()); |
| } |
| |
| // Only handle binary operators here. |
| if (!isa<BinaryOperator>(TI)) |
| return 0; |
| |
| // Figure out if the operations have any operands in common. |
| Value *MatchOp, *OtherOpT, *OtherOpF; |
| bool MatchIsOpZero; |
| if (TI->getOperand(0) == FI->getOperand(0)) { |
| MatchOp = TI->getOperand(0); |
| OtherOpT = TI->getOperand(1); |
| OtherOpF = FI->getOperand(1); |
| MatchIsOpZero = true; |
| } else if (TI->getOperand(1) == FI->getOperand(1)) { |
| MatchOp = TI->getOperand(1); |
| OtherOpT = TI->getOperand(0); |
| OtherOpF = FI->getOperand(0); |
| MatchIsOpZero = false; |
| } else if (!TI->isCommutative()) { |
| return 0; |
| } else if (TI->getOperand(0) == FI->getOperand(1)) { |
| MatchOp = TI->getOperand(0); |
| OtherOpT = TI->getOperand(1); |
| OtherOpF = FI->getOperand(0); |
| MatchIsOpZero = true; |
| } else if (TI->getOperand(1) == FI->getOperand(0)) { |
| MatchOp = TI->getOperand(1); |
| OtherOpT = TI->getOperand(0); |
| OtherOpF = FI->getOperand(1); |
| MatchIsOpZero = true; |
| } else { |
| return 0; |
| } |
| |
| // If we reach here, they do have operations in common. |
| SelectInst *NewSI = SelectInst::Create(SI.getCondition(), OtherOpT, |
| OtherOpF, SI.getName()+".v"); |
| InsertNewInstBefore(NewSI, SI); |
| |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) { |
| if (MatchIsOpZero) |
| return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI); |
| else |
| return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp); |
| } |
| llvm_unreachable("Shouldn't get here"); |
| return 0; |
| } |
| |
| static bool isSelect01(Constant *C1, Constant *C2) { |
| ConstantInt *C1I = dyn_cast<ConstantInt>(C1); |
| if (!C1I) |
| return false; |
| ConstantInt *C2I = dyn_cast<ConstantInt>(C2); |
| if (!C2I) |
| return false; |
| return (C1I->isZero() || C1I->isOne()) && (C2I->isZero() || C2I->isOne()); |
| } |
| |
| /// FoldSelectIntoOp - Try fold the select into one of the operands to |
| /// facilitate further optimization. |
| Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal, |
| Value *FalseVal) { |
| // See the comment above GetSelectFoldableOperands for a description of the |
| // transformation we are doing here. |
| if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) { |
| if (TVI->hasOneUse() && TVI->getNumOperands() == 2 && |
| !isa<Constant>(FalseVal)) { |
| if (unsigned SFO = GetSelectFoldableOperands(TVI)) { |
| unsigned OpToFold = 0; |
| if ((SFO & 1) && FalseVal == TVI->getOperand(0)) { |
| OpToFold = 1; |
| } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) { |
| OpToFold = 2; |
| } |
| |
| if (OpToFold) { |
| Constant *C = GetSelectFoldableConstant(TVI); |
| Value *OOp = TVI->getOperand(2-OpToFold); |
| // Avoid creating select between 2 constants unless it's selecting |
| // between 0 and 1. |
| if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) { |
| Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C); |
| InsertNewInstBefore(NewSel, SI); |
| NewSel->takeName(TVI); |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI)) |
| return BinaryOperator::Create(BO->getOpcode(), FalseVal, NewSel); |
| llvm_unreachable("Unknown instruction!!"); |
| } |
| } |
| } |
| } |
| } |
| |
| if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) { |
| if (FVI->hasOneUse() && FVI->getNumOperands() == 2 && |
| !isa<Constant>(TrueVal)) { |
| if (unsigned SFO = GetSelectFoldableOperands(FVI)) { |
| unsigned OpToFold = 0; |
| if ((SFO & 1) && TrueVal == FVI->getOperand(0)) { |
| OpToFold = 1; |
| } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) { |
| OpToFold = 2; |
| } |
| |
| if (OpToFold) { |
| Constant *C = GetSelectFoldableConstant(FVI); |
| Value *OOp = FVI->getOperand(2-OpToFold); |
| // Avoid creating select between 2 constants unless it's selecting |
| // between 0 and 1. |
| if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) { |
| Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp); |
| InsertNewInstBefore(NewSel, SI); |
| NewSel->takeName(FVI); |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI)) |
| return BinaryOperator::Create(BO->getOpcode(), TrueVal, NewSel); |
| llvm_unreachable("Unknown instruction!!"); |
| } |
| } |
| } |
| } |
| } |
| |
| return 0; |
| } |
| |
| /// visitSelectInstWithICmp - Visit a SelectInst that has an |
| /// ICmpInst as its first operand. |
| /// |
| Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI, |
| ICmpInst *ICI) { |
| bool Changed = false; |
| ICmpInst::Predicate Pred = ICI->getPredicate(); |
| Value *CmpLHS = ICI->getOperand(0); |
| Value *CmpRHS = ICI->getOperand(1); |
| Value *TrueVal = SI.getTrueValue(); |
| Value *FalseVal = SI.getFalseValue(); |
| |
| // Check cases where the comparison is with a constant that |
| // can be adjusted to fit the min/max idiom. We may edit ICI in |
| // place here, so make sure the select is the only user. |
| if (ICI->hasOneUse()) |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) { |
| switch (Pred) { |
| default: break; |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: { |
| // X < MIN ? T : F --> F |
| if (CI->isMinValue(Pred == ICmpInst::ICMP_SLT)) |
| return ReplaceInstUsesWith(SI, FalseVal); |
| // X < C ? X : C-1 --> X > C-1 ? C-1 : X |
| Constant *AdjustedRHS = |
| ConstantInt::get(CI->getContext(), CI->getValue()-1); |
| if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) || |
| (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) { |
| Pred = ICmpInst::getSwappedPredicate(Pred); |
| CmpRHS = AdjustedRHS; |
| std::swap(FalseVal, TrueVal); |
| ICI->setPredicate(Pred); |
| ICI->setOperand(1, CmpRHS); |
| SI.setOperand(1, TrueVal); |
| SI.setOperand(2, FalseVal); |
| Changed = true; |
| } |
| break; |
| } |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: { |
| // X > MAX ? T : F --> F |
| if (CI->isMaxValue(Pred == ICmpInst::ICMP_SGT)) |
| return ReplaceInstUsesWith(SI, FalseVal); |
| // X > C ? X : C+1 --> X < C+1 ? C+1 : X |
| Constant *AdjustedRHS = |
| ConstantInt::get(CI->getContext(), CI->getValue()+1); |
| if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) || |
| (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) { |
| Pred = ICmpInst::getSwappedPredicate(Pred); |
| CmpRHS = AdjustedRHS; |
| std::swap(FalseVal, TrueVal); |
| ICI->setPredicate(Pred); |
| ICI->setOperand(1, CmpRHS); |
| SI.setOperand(1, TrueVal); |
| SI.setOperand(2, FalseVal); |
| Changed = true; |
| } |
| break; |
| } |
| } |
| } |
| |
| if (CmpLHS == TrueVal && CmpRHS == FalseVal) { |
| // Transform (X == Y) ? X : Y -> Y |
| if (Pred == ICmpInst::ICMP_EQ) |
| return ReplaceInstUsesWith(SI, FalseVal); |
| // Transform (X != Y) ? X : Y -> X |
| if (Pred == ICmpInst::ICMP_NE) |
| return ReplaceInstUsesWith(SI, TrueVal); |
| /// NOTE: if we wanted to, this is where to detect integer MIN/MAX |
| |
| } else if (CmpLHS == FalseVal && CmpRHS == TrueVal) { |
| // Transform (X == Y) ? Y : X -> X |
| if (Pred == ICmpInst::ICMP_EQ) |
| return ReplaceInstUsesWith(SI, FalseVal); |
| // Transform (X != Y) ? Y : X -> Y |
| if (Pred == ICmpInst::ICMP_NE) |
| return ReplaceInstUsesWith(SI, TrueVal); |
| /// NOTE: if we wanted to, this is where to detect integer MIN/MAX |
| } |
| return Changed ? &SI : 0; |
| } |
| |
| |
| /// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a |
| /// PHI node (but the two may be in different blocks). See if the true/false |
| /// values (V) are live in all of the predecessor blocks of the PHI. For |
| /// example, cases like this cannot be mapped: |
| /// |
| /// X = phi [ C1, BB1], [C2, BB2] |
| /// Y = add |
| /// Z = select X, Y, 0 |
| /// |
| /// because Y is not live in BB1/BB2. |
| /// |
| static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V, |
| const SelectInst &SI) { |
| // If the value is a non-instruction value like a constant or argument, it |
| // can always be mapped. |
| const Instruction *I = dyn_cast<Instruction>(V); |
| if (I == 0) return true; |
| |
| // If V is a PHI node defined in the same block as the condition PHI, we can |
| // map the arguments. |
| const PHINode *CondPHI = cast<PHINode>(SI.getCondition()); |
| |
| if (const PHINode *VP = dyn_cast<PHINode>(I)) |
| if (VP->getParent() == CondPHI->getParent()) |
| return true; |
| |
| // Otherwise, if the PHI and select are defined in the same block and if V is |
| // defined in a different block, then we can transform it. |
| if (SI.getParent() == CondPHI->getParent() && |
| I->getParent() != CondPHI->getParent()) |
| return true; |
| |
| // Otherwise we have a 'hard' case and we can't tell without doing more |
| // detailed dominator based analysis, punt. |
| return false; |
| } |
| |
| /// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form: |
| /// SPF2(SPF1(A, B), C) |
| Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner, |
| SelectPatternFlavor SPF1, |
| Value *A, Value *B, |
| Instruction &Outer, |
| SelectPatternFlavor SPF2, Value *C) { |
| if (C == A || C == B) { |
| // MAX(MAX(A, B), B) -> MAX(A, B) |
| // MIN(MIN(a, b), a) -> MIN(a, b) |
| if (SPF1 == SPF2) |
| return ReplaceInstUsesWith(Outer, Inner); |
| |
| // MAX(MIN(a, b), a) -> a |
| // MIN(MAX(a, b), a) -> a |
| if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) || |
| (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) || |
| (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) || |
| (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN)) |
| return ReplaceInstUsesWith(Outer, C); |
| } |
| |
| // TODO: MIN(MIN(A, 23), 97) |
| return 0; |
| } |
| |
| |
| |
| |
| Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { |
| Value *CondVal = SI.getCondition(); |
| Value *TrueVal = SI.getTrueValue(); |
| Value *FalseVal = SI.getFalseValue(); |
| |
| // select true, X, Y -> X |
| // select false, X, Y -> Y |
| if (ConstantInt *C = dyn_cast<ConstantInt>(CondVal)) |
| return ReplaceInstUsesWith(SI, C->getZExtValue() ? TrueVal : FalseVal); |
| |
| // select C, X, X -> X |
| if (TrueVal == FalseVal) |
| return ReplaceInstUsesWith(SI, TrueVal); |
| |
| if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X |
| return ReplaceInstUsesWith(SI, FalseVal); |
| if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X |
| return ReplaceInstUsesWith(SI, TrueVal); |
| if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y |
| if (isa<Constant>(TrueVal)) |
| return ReplaceInstUsesWith(SI, TrueVal); |
| else |
| return ReplaceInstUsesWith(SI, FalseVal); |
| } |
| |
| if (SI.getType()->isInteger(1)) { |
| if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) { |
| if (C->getZExtValue()) { |
| // Change: A = select B, true, C --> A = or B, C |
| return BinaryOperator::CreateOr(CondVal, FalseVal); |
| } else { |
| // Change: A = select B, false, C --> A = and !B, C |
| Value *NotCond = |
| InsertNewInstBefore(BinaryOperator::CreateNot(CondVal, |
| "not."+CondVal->getName()), SI); |
| return BinaryOperator::CreateAnd(NotCond, FalseVal); |
| } |
| } else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) { |
| if (C->getZExtValue() == false) { |
| // Change: A = select B, C, false --> A = and B, C |
| return BinaryOperator::CreateAnd(CondVal, TrueVal); |
| } else { |
| // Change: A = select B, C, true --> A = or !B, C |
| Value *NotCond = |
| InsertNewInstBefore(BinaryOperator::CreateNot(CondVal, |
| "not."+CondVal->getName()), SI); |
| return BinaryOperator::CreateOr(NotCond, TrueVal); |
| } |
| } |
| |
| // select a, b, a -> a&b |
| // select a, a, b -> a|b |
| if (CondVal == TrueVal) |
| return BinaryOperator::CreateOr(CondVal, FalseVal); |
| else if (CondVal == FalseVal) |
| return BinaryOperator::CreateAnd(CondVal, TrueVal); |
| } |
| |
| // Selecting between two integer constants? |
| if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal)) |
| if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) { |
| // select C, 1, 0 -> zext C to int |
| if (FalseValC->isZero() && TrueValC->getValue() == 1) |
| return new ZExtInst(CondVal, SI.getType()); |
| |
| // select C, -1, 0 -> sext C to int |
| if (FalseValC->isZero() && TrueValC->isAllOnesValue()) |
| return new SExtInst(CondVal, SI.getType()); |
| |
| // select C, 0, 1 -> zext !C to int |
| if (TrueValC->isZero() && FalseValC->getValue() == 1) { |
| Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName()); |
| return new ZExtInst(NotCond, SI.getType()); |
| } |
| |
| // select C, 0, -1 -> sext !C to int |
| if (TrueValC->isZero() && FalseValC->isAllOnesValue()) { |
| Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName()); |
| return new SExtInst(NotCond, SI.getType()); |
| } |
| |
| if (ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition())) { |
| // If one of the constants is zero (we know they can't both be) and we |
| // have an icmp instruction with zero, and we have an 'and' with the |
| // non-constant value, eliminate this whole mess. This corresponds to |
| // cases like this: ((X & 27) ? 27 : 0) |
| if (TrueValC->isZero() || FalseValC->isZero()) |
| if (IC->isEquality() && isa<ConstantInt>(IC->getOperand(1)) && |
| cast<Constant>(IC->getOperand(1))->isNullValue()) |
| if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0))) |
| if (ICA->getOpcode() == Instruction::And && |
| isa<ConstantInt>(ICA->getOperand(1)) && |
| (ICA->getOperand(1) == TrueValC || |
| ICA->getOperand(1) == FalseValC) && |
| cast<ConstantInt>(ICA->getOperand(1))->getValue().isPowerOf2()) { |
| // Okay, now we know that everything is set up, we just don't |
| // know whether we have a icmp_ne or icmp_eq and whether the |
| // true or false val is the zero. |
| bool ShouldNotVal = !TrueValC->isZero(); |
| ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE; |
| Value *V = ICA; |
| if (ShouldNotVal) |
| V = Builder->CreateXor(V, ICA->getOperand(1)); |
| return ReplaceInstUsesWith(SI, V); |
| } |
| } |
| } |
| |
| // See if we are selecting two values based on a comparison of the two values. |
| if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) { |
| if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) { |
| // Transform (X == Y) ? X : Y -> Y |
| if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { |
| // This is not safe in general for floating point: |
| // consider X== -0, Y== +0. |
| // It becomes safe if either operand is a nonzero constant. |
| ConstantFP *CFPt, *CFPf; |
| if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && |
| !CFPt->getValueAPF().isZero()) || |
| ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && |
| !CFPf->getValueAPF().isZero())) |
| return ReplaceInstUsesWith(SI, FalseVal); |
| } |
| // Transform (X != Y) ? X : Y -> X |
| if (FCI->getPredicate() == FCmpInst::FCMP_ONE) |
| return ReplaceInstUsesWith(SI, TrueVal); |
| // NOTE: if we wanted to, this is where to detect MIN/MAX |
| |
| } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){ |
| // Transform (X == Y) ? Y : X -> X |
| if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { |
| // This is not safe in general for floating point: |
| // consider X== -0, Y== +0. |
| // It becomes safe if either operand is a nonzero constant. |
| ConstantFP *CFPt, *CFPf; |
| if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && |
| !CFPt->getValueAPF().isZero()) || |
| ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && |
| !CFPf->getValueAPF().isZero())) |
| return ReplaceInstUsesWith(SI, FalseVal); |
| } |
| // Transform (X != Y) ? Y : X -> Y |
| if (FCI->getPredicate() == FCmpInst::FCMP_ONE) |
| return ReplaceInstUsesWith(SI, TrueVal); |
| // NOTE: if we wanted to, this is where to detect MIN/MAX |
| } |
| // NOTE: if we wanted to, this is where to detect ABS |
| } |
| |
| // See if we are selecting two values based on a comparison of the two values. |
| if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal)) |
| if (Instruction *Result = visitSelectInstWithICmp(SI, ICI)) |
| return Result; |
| |
| if (Instruction *TI = dyn_cast<Instruction>(TrueVal)) |
| if (Instruction *FI = dyn_cast<Instruction>(FalseVal)) |
| if (TI->hasOneUse() && FI->hasOneUse()) { |
| Instruction *AddOp = 0, *SubOp = 0; |
| |
| // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z)) |
| if (TI->getOpcode() == FI->getOpcode()) |
| if (Instruction *IV = FoldSelectOpOp(SI, TI, FI)) |
| return IV; |
| |
| // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is |
| // even legal for FP. |
| if ((TI->getOpcode() == Instruction::Sub && |
| FI->getOpcode() == Instruction::Add) || |
| (TI->getOpcode() == Instruction::FSub && |
| FI->getOpcode() == Instruction::FAdd)) { |
| AddOp = FI; SubOp = TI; |
| } else if ((FI->getOpcode() == Instruction::Sub && |
| TI->getOpcode() == Instruction::Add) || |
| (FI->getOpcode() == Instruction::FSub && |
| TI->getOpcode() == Instruction::FAdd)) { |
| AddOp = TI; SubOp = FI; |
| } |
| |
| if (AddOp) { |
| Value *OtherAddOp = 0; |
| if (SubOp->getOperand(0) == AddOp->getOperand(0)) { |
| OtherAddOp = AddOp->getOperand(1); |
| } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) { |
| OtherAddOp = AddOp->getOperand(0); |
| } |
| |
| if (OtherAddOp) { |
| // So at this point we know we have (Y -> OtherAddOp): |
| // select C, (add X, Y), (sub X, Z) |
| Value *NegVal; // Compute -Z |
| if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) { |
| NegVal = ConstantExpr::getNeg(C); |
| } else { |
| NegVal = InsertNewInstBefore( |
| BinaryOperator::CreateNeg(SubOp->getOperand(1), |
| "tmp"), SI); |
| } |
| |
| Value *NewTrueOp = OtherAddOp; |
| Value *NewFalseOp = NegVal; |
| if (AddOp != TI) |
| std::swap(NewTrueOp, NewFalseOp); |
| Instruction *NewSel = |
| SelectInst::Create(CondVal, NewTrueOp, |
| NewFalseOp, SI.getName() + ".p"); |
| |
| NewSel = InsertNewInstBefore(NewSel, SI); |
| return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel); |
| } |
| } |
| } |
| |
| // See if we can fold the select into one of our operands. |
| if (SI.getType()->isInteger()) { |
| if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal)) |
| return FoldI; |
| |
| // MAX(MAX(a, b), a) -> MAX(a, b) |
| // MIN(MIN(a, b), a) -> MIN(a, b) |
| // MAX(MIN(a, b), a) -> a |
| // MIN(MAX(a, b), a) -> a |
| Value *LHS, *RHS, *LHS2, *RHS2; |
| if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) { |
| if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2)) |
| if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2, |
| SI, SPF, RHS)) |
| return R; |
| if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2)) |
| if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2, |
| SI, SPF, LHS)) |
| return R; |
| } |
| |
| // TODO. |
| // ABS(-X) -> ABS(X) |
| // ABS(ABS(X)) -> ABS(X) |
| } |
| |
| // See if we can fold the select into a phi node if the condition is a select. |
| if (isa<PHINode>(SI.getCondition())) |
| // The true/false values have to be live in the PHI predecessor's blocks. |
| if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) && |
| CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI)) |
| if (Instruction *NV = FoldOpIntoPhi(SI)) |
| return NV; |
| |
| if (BinaryOperator::isNot(CondVal)) { |
| SI.setOperand(0, BinaryOperator::getNotArgument(CondVal)); |
| SI.setOperand(1, FalseVal); |
| SI.setOperand(2, TrueVal); |
| return &SI; |
| } |
| |
| return 0; |
| } |
