//===- 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(V); if (SI == 0) return SPF_UNKNOWN; ICmpInst *ICI = dyn_cast(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(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(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(C1); if (!C1I) return false; ConstantInt *C2I = dyn_cast(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(TrueVal)) { if (TVI->hasOneUse() && TVI->getNumOperands() == 2 && !isa(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(OOp) || isSelect01(C, cast(OOp))) { Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C); InsertNewInstBefore(NewSel, SI); NewSel->takeName(TVI); if (BinaryOperator *BO = dyn_cast(TVI)) return BinaryOperator::Create(BO->getOpcode(), FalseVal, NewSel); llvm_unreachable("Unknown instruction!!"); } } } } } if (Instruction *FVI = dyn_cast(FalseVal)) { if (FVI->hasOneUse() && FVI->getNumOperands() == 2 && !isa(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(OOp) || isSelect01(C, cast(OOp))) { Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp); InsertNewInstBefore(NewSel, SI); NewSel->takeName(FVI); if (BinaryOperator *BO = dyn_cast(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(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(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(SI.getCondition()); if (const PHINode *VP = dyn_cast(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(CondVal)) return ReplaceInstUsesWith(SI, C->getZExtValue() ? TrueVal : FalseVal); // select C, X, X -> X if (TrueVal == FalseVal) return ReplaceInstUsesWith(SI, TrueVal); if (isa(TrueVal)) // select C, undef, X -> X return ReplaceInstUsesWith(SI, FalseVal); if (isa(FalseVal)) // select C, X, undef -> X return ReplaceInstUsesWith(SI, TrueVal); if (isa(CondVal)) { // select undef, X, Y -> X or Y if (isa(TrueVal)) return ReplaceInstUsesWith(SI, TrueVal); else return ReplaceInstUsesWith(SI, FalseVal); } if (SI.getType()->isInteger(1)) { if (ConstantInt *C = dyn_cast(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(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(TrueVal)) if (ConstantInt *FalseValC = dyn_cast(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(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(IC->getOperand(1)) && cast(IC->getOperand(1))->isNullValue()) if (Instruction *ICA = dyn_cast(IC->getOperand(0))) if (ICA->getOpcode() == Instruction::And && isa(ICA->getOperand(1)) && (ICA->getOperand(1) == TrueValC || ICA->getOperand(1) == FalseValC) && cast(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(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(TrueVal)) && !CFPt->getValueAPF().isZero()) || ((CFPf = dyn_cast(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(TrueVal)) && !CFPt->getValueAPF().isZero()) || ((CFPf = dyn_cast(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(CondVal)) if (Instruction *Result = visitSelectInstWithICmp(SI, ICI)) return Result; if (Instruction *TI = dyn_cast(TrueVal)) if (Instruction *FI = dyn_cast(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(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(LHS),SPF2,LHS2,RHS2, SI, SPF, RHS)) return R; if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2)) if (Instruction *R = FoldSPFofSPF(cast(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(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; }