| //===- InstCombineSelect.cpp ----------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements the visitSelect function. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "InstCombineInternal.h" |
| #include "llvm/ADT/APInt.h" |
| #include "llvm/ADT/Optional.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/Analysis/AssumptionCache.h" |
| #include "llvm/Analysis/CmpInstAnalysis.h" |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/OverflowInstAnalysis.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/IR/BasicBlock.h" |
| #include "llvm/IR/Constant.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/IRBuilder.h" |
| #include "llvm/IR/InstrTypes.h" |
| #include "llvm/IR/Instruction.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/IR/Intrinsics.h" |
| #include "llvm/IR/Operator.h" |
| #include "llvm/IR/PatternMatch.h" |
| #include "llvm/IR/Type.h" |
| #include "llvm/IR/User.h" |
| #include "llvm/IR/Value.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/KnownBits.h" |
| #include "llvm/Transforms/InstCombine/InstCombiner.h" |
| #include <cassert> |
| #include <utility> |
| |
| #define DEBUG_TYPE "instcombine" |
| #include "llvm/Transforms/Utils/InstructionWorklist.h" |
| |
| using namespace llvm; |
| using namespace PatternMatch; |
| |
| |
| static Value *createMinMax(InstCombiner::BuilderTy &Builder, |
| SelectPatternFlavor SPF, Value *A, Value *B) { |
| CmpInst::Predicate Pred = getMinMaxPred(SPF); |
| assert(CmpInst::isIntPredicate(Pred) && "Expected integer predicate"); |
| return Builder.CreateSelect(Builder.CreateICmp(Pred, A, B), A, B); |
| } |
| |
| /// Replace a select operand based on an equality comparison with the identity |
| /// constant of a binop. |
| static Instruction *foldSelectBinOpIdentity(SelectInst &Sel, |
| const TargetLibraryInfo &TLI, |
| InstCombinerImpl &IC) { |
| // The select condition must be an equality compare with a constant operand. |
| Value *X; |
| Constant *C; |
| CmpInst::Predicate Pred; |
| if (!match(Sel.getCondition(), m_Cmp(Pred, m_Value(X), m_Constant(C)))) |
| return nullptr; |
| |
| bool IsEq; |
| if (ICmpInst::isEquality(Pred)) |
| IsEq = Pred == ICmpInst::ICMP_EQ; |
| else if (Pred == FCmpInst::FCMP_OEQ) |
| IsEq = true; |
| else if (Pred == FCmpInst::FCMP_UNE) |
| IsEq = false; |
| else |
| return nullptr; |
| |
| // A select operand must be a binop. |
| BinaryOperator *BO; |
| if (!match(Sel.getOperand(IsEq ? 1 : 2), m_BinOp(BO))) |
| return nullptr; |
| |
| // The compare constant must be the identity constant for that binop. |
| // If this a floating-point compare with 0.0, any zero constant will do. |
| Type *Ty = BO->getType(); |
| Constant *IdC = ConstantExpr::getBinOpIdentity(BO->getOpcode(), Ty, true); |
| if (IdC != C) { |
| if (!IdC || !CmpInst::isFPPredicate(Pred)) |
| return nullptr; |
| if (!match(IdC, m_AnyZeroFP()) || !match(C, m_AnyZeroFP())) |
| return nullptr; |
| } |
| |
| // Last, match the compare variable operand with a binop operand. |
| Value *Y; |
| if (!BO->isCommutative() && !match(BO, m_BinOp(m_Value(Y), m_Specific(X)))) |
| return nullptr; |
| if (!match(BO, m_c_BinOp(m_Value(Y), m_Specific(X)))) |
| return nullptr; |
| |
| // +0.0 compares equal to -0.0, and so it does not behave as required for this |
| // transform. Bail out if we can not exclude that possibility. |
| if (isa<FPMathOperator>(BO)) |
| if (!BO->hasNoSignedZeros() && !CannotBeNegativeZero(Y, &TLI)) |
| return nullptr; |
| |
| // BO = binop Y, X |
| // S = { select (cmp eq X, C), BO, ? } or { select (cmp ne X, C), ?, BO } |
| // => |
| // S = { select (cmp eq X, C), Y, ? } or { select (cmp ne X, C), ?, Y } |
| return IC.replaceOperand(Sel, IsEq ? 1 : 2, Y); |
| } |
| |
| /// This folds: |
| /// select (icmp eq (and X, C1)), TC, FC |
| /// iff C1 is a power 2 and the difference between TC and FC is a power-of-2. |
| /// To something like: |
| /// (shr (and (X, C1)), (log2(C1) - log2(TC-FC))) + FC |
| /// Or: |
| /// (shl (and (X, C1)), (log2(TC-FC) - log2(C1))) + FC |
| /// With some variations depending if FC is larger than TC, or the shift |
| /// isn't needed, or the bit widths don't match. |
| static Value *foldSelectICmpAnd(SelectInst &Sel, ICmpInst *Cmp, |
| InstCombiner::BuilderTy &Builder) { |
| const APInt *SelTC, *SelFC; |
| if (!match(Sel.getTrueValue(), m_APInt(SelTC)) || |
| !match(Sel.getFalseValue(), m_APInt(SelFC))) |
| return nullptr; |
| |
| // If this is a vector select, we need a vector compare. |
| Type *SelType = Sel.getType(); |
| if (SelType->isVectorTy() != Cmp->getType()->isVectorTy()) |
| return nullptr; |
| |
| Value *V; |
| APInt AndMask; |
| bool CreateAnd = false; |
| ICmpInst::Predicate Pred = Cmp->getPredicate(); |
| if (ICmpInst::isEquality(Pred)) { |
| if (!match(Cmp->getOperand(1), m_Zero())) |
| return nullptr; |
| |
| V = Cmp->getOperand(0); |
| const APInt *AndRHS; |
| if (!match(V, m_And(m_Value(), m_Power2(AndRHS)))) |
| return nullptr; |
| |
| AndMask = *AndRHS; |
| } else if (decomposeBitTestICmp(Cmp->getOperand(0), Cmp->getOperand(1), |
| Pred, V, AndMask)) { |
| assert(ICmpInst::isEquality(Pred) && "Not equality test?"); |
| if (!AndMask.isPowerOf2()) |
| return nullptr; |
| |
| CreateAnd = true; |
| } else { |
| return nullptr; |
| } |
| |
| // In general, when both constants are non-zero, we would need an offset to |
| // replace the select. This would require more instructions than we started |
| // with. But there's one special-case that we handle here because it can |
| // simplify/reduce the instructions. |
| APInt TC = *SelTC; |
| APInt FC = *SelFC; |
| if (!TC.isZero() && !FC.isZero()) { |
| // If the select constants differ by exactly one bit and that's the same |
| // bit that is masked and checked by the select condition, the select can |
| // be replaced by bitwise logic to set/clear one bit of the constant result. |
| if (TC.getBitWidth() != AndMask.getBitWidth() || (TC ^ FC) != AndMask) |
| return nullptr; |
| if (CreateAnd) { |
| // If we have to create an 'and', then we must kill the cmp to not |
| // increase the instruction count. |
| if (!Cmp->hasOneUse()) |
| return nullptr; |
| V = Builder.CreateAnd(V, ConstantInt::get(SelType, AndMask)); |
| } |
| bool ExtraBitInTC = TC.ugt(FC); |
| if (Pred == ICmpInst::ICMP_EQ) { |
| // If the masked bit in V is clear, clear or set the bit in the result: |
| // (V & AndMaskC) == 0 ? TC : FC --> (V & AndMaskC) ^ TC |
| // (V & AndMaskC) == 0 ? TC : FC --> (V & AndMaskC) | TC |
| Constant *C = ConstantInt::get(SelType, TC); |
| return ExtraBitInTC ? Builder.CreateXor(V, C) : Builder.CreateOr(V, C); |
| } |
| if (Pred == ICmpInst::ICMP_NE) { |
| // If the masked bit in V is set, set or clear the bit in the result: |
| // (V & AndMaskC) != 0 ? TC : FC --> (V & AndMaskC) | FC |
| // (V & AndMaskC) != 0 ? TC : FC --> (V & AndMaskC) ^ FC |
| Constant *C = ConstantInt::get(SelType, FC); |
| return ExtraBitInTC ? Builder.CreateOr(V, C) : Builder.CreateXor(V, C); |
| } |
| llvm_unreachable("Only expecting equality predicates"); |
| } |
| |
| // Make sure one of the select arms is a power-of-2. |
| if (!TC.isPowerOf2() && !FC.isPowerOf2()) |
| return nullptr; |
| |
| // Determine which shift is needed to transform result of the 'and' into the |
| // desired result. |
| const APInt &ValC = !TC.isZero() ? TC : FC; |
| unsigned ValZeros = ValC.logBase2(); |
| unsigned AndZeros = AndMask.logBase2(); |
| |
| // Insert the 'and' instruction on the input to the truncate. |
| if (CreateAnd) |
| V = Builder.CreateAnd(V, ConstantInt::get(V->getType(), AndMask)); |
| |
| // If types don't match, we can still convert the select by introducing a zext |
| // or a trunc of the 'and'. |
| if (ValZeros > AndZeros) { |
| V = Builder.CreateZExtOrTrunc(V, SelType); |
| V = Builder.CreateShl(V, ValZeros - AndZeros); |
| } else if (ValZeros < AndZeros) { |
| V = Builder.CreateLShr(V, AndZeros - ValZeros); |
| V = Builder.CreateZExtOrTrunc(V, SelType); |
| } else { |
| V = Builder.CreateZExtOrTrunc(V, SelType); |
| } |
| |
| // 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 = !TC.isZero(); |
| ShouldNotVal ^= Pred == ICmpInst::ICMP_NE; |
| if (ShouldNotVal) |
| V = Builder.CreateXor(V, ValC); |
| |
| return V; |
| } |
| |
| /// 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(BinaryOperator *I) { |
| switch (I->getOpcode()) { |
| case Instruction::Add: |
| case Instruction::FAdd: |
| case Instruction::Mul: |
| case Instruction::FMul: |
| 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::FSub: |
| case Instruction::FDiv: // Can only fold on the divisor amount. |
| case Instruction::Shl: // Can only fold on the shift amount. |
| case Instruction::LShr: |
| case Instruction::AShr: |
| return 1; |
| default: |
| return 0; // Cannot fold |
| } |
| } |
| |
| /// We have (select c, TI, FI), and we know that TI and FI have the same opcode. |
| Instruction *InstCombinerImpl::foldSelectOpOp(SelectInst &SI, Instruction *TI, |
| Instruction *FI) { |
| // Don't break up min/max patterns. The hasOneUse checks below prevent that |
| // for most cases, but vector min/max with bitcasts can be transformed. If the |
| // one-use restrictions are eased for other patterns, we still don't want to |
| // obfuscate min/max. |
| if ((match(&SI, m_SMin(m_Value(), m_Value())) || |
| match(&SI, m_SMax(m_Value(), m_Value())) || |
| match(&SI, m_UMin(m_Value(), m_Value())) || |
| match(&SI, m_UMax(m_Value(), m_Value())))) |
| return nullptr; |
| |
| // If this is a cast from the same type, merge. |
| Value *Cond = SI.getCondition(); |
| Type *CondTy = Cond->getType(); |
| if (TI->getNumOperands() == 1 && TI->isCast()) { |
| Type *FIOpndTy = FI->getOperand(0)->getType(); |
| if (TI->getOperand(0)->getType() != FIOpndTy) |
| return nullptr; |
| |
| // The select condition may be a vector. We may only change the operand |
| // type if the vector width remains the same (and matches the condition). |
| if (auto *CondVTy = dyn_cast<VectorType>(CondTy)) { |
| if (!FIOpndTy->isVectorTy() || |
| CondVTy->getElementCount() != |
| cast<VectorType>(FIOpndTy)->getElementCount()) |
| return nullptr; |
| |
| // TODO: If the backend knew how to deal with casts better, we could |
| // remove this limitation. For now, there's too much potential to create |
| // worse codegen by promoting the select ahead of size-altering casts |
| // (PR28160). |
| // |
| // Note that ValueTracking's matchSelectPattern() looks through casts |
| // without checking 'hasOneUse' when it matches min/max patterns, so this |
| // transform may end up happening anyway. |
| if (TI->getOpcode() != Instruction::BitCast && |
| (!TI->hasOneUse() || !FI->hasOneUse())) |
| return nullptr; |
| } else if (!TI->hasOneUse() || !FI->hasOneUse()) { |
| // TODO: The one-use restrictions for a scalar select could be eased if |
| // the fold of a select in visitLoadInst() was enhanced to match a pattern |
| // that includes a cast. |
| return nullptr; |
| } |
| |
| // Fold this by inserting a select from the input values. |
| Value *NewSI = |
| Builder.CreateSelect(Cond, TI->getOperand(0), FI->getOperand(0), |
| SI.getName() + ".v", &SI); |
| return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI, |
| TI->getType()); |
| } |
| |
| // Cond ? -X : -Y --> -(Cond ? X : Y) |
| Value *X, *Y; |
| if (match(TI, m_FNeg(m_Value(X))) && match(FI, m_FNeg(m_Value(Y))) && |
| (TI->hasOneUse() || FI->hasOneUse())) { |
| // Intersect FMF from the fneg instructions and union those with the select. |
| FastMathFlags FMF = TI->getFastMathFlags(); |
| FMF &= FI->getFastMathFlags(); |
| FMF |= SI.getFastMathFlags(); |
| Value *NewSel = Builder.CreateSelect(Cond, X, Y, SI.getName() + ".v", &SI); |
| if (auto *NewSelI = dyn_cast<Instruction>(NewSel)) |
| NewSelI->setFastMathFlags(FMF); |
| Instruction *NewFNeg = UnaryOperator::CreateFNeg(NewSel); |
| NewFNeg->setFastMathFlags(FMF); |
| return NewFNeg; |
| } |
| |
| // Min/max intrinsic with a common operand can have the common operand pulled |
| // after the select. This is the same transform as below for binops, but |
| // specialized for intrinsic matching and without the restrictive uses clause. |
| auto *TII = dyn_cast<IntrinsicInst>(TI); |
| auto *FII = dyn_cast<IntrinsicInst>(FI); |
| if (TII && FII && TII->getIntrinsicID() == FII->getIntrinsicID() && |
| (TII->hasOneUse() || FII->hasOneUse())) { |
| Value *T0, *T1, *F0, *F1; |
| if (match(TII, m_MaxOrMin(m_Value(T0), m_Value(T1))) && |
| match(FII, m_MaxOrMin(m_Value(F0), m_Value(F1)))) { |
| if (T0 == F0) { |
| Value *NewSel = Builder.CreateSelect(Cond, T1, F1, "minmaxop", &SI); |
| return CallInst::Create(TII->getCalledFunction(), {NewSel, T0}); |
| } |
| if (T0 == F1) { |
| Value *NewSel = Builder.CreateSelect(Cond, T1, F0, "minmaxop", &SI); |
| return CallInst::Create(TII->getCalledFunction(), {NewSel, T0}); |
| } |
| if (T1 == F0) { |
| Value *NewSel = Builder.CreateSelect(Cond, T0, F1, "minmaxop", &SI); |
| return CallInst::Create(TII->getCalledFunction(), {NewSel, T1}); |
| } |
| if (T1 == F1) { |
| Value *NewSel = Builder.CreateSelect(Cond, T0, F0, "minmaxop", &SI); |
| return CallInst::Create(TII->getCalledFunction(), {NewSel, T1}); |
| } |
| } |
| } |
| |
| // Only handle binary operators (including two-operand getelementptr) with |
| // one-use here. As with the cast case above, it may be possible to relax the |
| // one-use constraint, but that needs be examined carefully since it may not |
| // reduce the total number of instructions. |
| if (TI->getNumOperands() != 2 || FI->getNumOperands() != 2 || |
| (!isa<BinaryOperator>(TI) && !isa<GetElementPtrInst>(TI)) || |
| !TI->hasOneUse() || !FI->hasOneUse()) |
| return nullptr; |
| |
| // 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 nullptr; |
| } 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 nullptr; |
| } |
| |
| // If the select condition is a vector, the operands of the original select's |
| // operands also must be vectors. This may not be the case for getelementptr |
| // for example. |
| if (CondTy->isVectorTy() && (!OtherOpT->getType()->isVectorTy() || |
| !OtherOpF->getType()->isVectorTy())) |
| return nullptr; |
| |
| // If we reach here, they do have operations in common. |
| Value *NewSI = Builder.CreateSelect(Cond, OtherOpT, OtherOpF, |
| SI.getName() + ".v", &SI); |
| Value *Op0 = MatchIsOpZero ? MatchOp : NewSI; |
| Value *Op1 = MatchIsOpZero ? NewSI : MatchOp; |
| if (auto *BO = dyn_cast<BinaryOperator>(TI)) { |
| BinaryOperator *NewBO = BinaryOperator::Create(BO->getOpcode(), Op0, Op1); |
| NewBO->copyIRFlags(TI); |
| NewBO->andIRFlags(FI); |
| return NewBO; |
| } |
| if (auto *TGEP = dyn_cast<GetElementPtrInst>(TI)) { |
| auto *FGEP = cast<GetElementPtrInst>(FI); |
| Type *ElementType = TGEP->getResultElementType(); |
| return TGEP->isInBounds() && FGEP->isInBounds() |
| ? GetElementPtrInst::CreateInBounds(ElementType, Op0, {Op1}) |
| : GetElementPtrInst::Create(ElementType, Op0, {Op1}); |
| } |
| llvm_unreachable("Expected BinaryOperator or GEP"); |
| return nullptr; |
| } |
| |
| static bool isSelect01(const APInt &C1I, const APInt &C2I) { |
| if (!C1I.isZero() && !C2I.isZero()) // One side must be zero. |
| return false; |
| return C1I.isOne() || C1I.isAllOnes() || C2I.isOne() || C2I.isAllOnes(); |
| } |
| |
| /// Try to fold the select into one of the operands to allow further |
| /// optimization. |
| Instruction *InstCombinerImpl::foldSelectIntoOp(SelectInst &SI, Value *TrueVal, |
| Value *FalseVal) { |
| // See the comment above GetSelectFoldableOperands for a description of the |
| // transformation we are doing here. |
| if (auto *TVI = dyn_cast<BinaryOperator>(TrueVal)) { |
| if (TVI->hasOneUse() && !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 = ConstantExpr::getBinOpIdentity(TVI->getOpcode(), |
| TVI->getType(), true); |
| Value *OOp = TVI->getOperand(2-OpToFold); |
| // Avoid creating select between 2 constants unless it's selecting |
| // between 0, 1 and -1. |
| const APInt *OOpC; |
| bool OOpIsAPInt = match(OOp, m_APInt(OOpC)); |
| if (!isa<Constant>(OOp) || |
| (OOpIsAPInt && isSelect01(C->getUniqueInteger(), *OOpC))) { |
| Value *NewSel = Builder.CreateSelect(SI.getCondition(), OOp, C); |
| NewSel->takeName(TVI); |
| BinaryOperator *BO = BinaryOperator::Create(TVI->getOpcode(), |
| FalseVal, NewSel); |
| BO->copyIRFlags(TVI); |
| return BO; |
| } |
| } |
| } |
| } |
| } |
| |
| if (auto *FVI = dyn_cast<BinaryOperator>(FalseVal)) { |
| if (FVI->hasOneUse() && !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 = ConstantExpr::getBinOpIdentity(FVI->getOpcode(), |
| FVI->getType(), true); |
| Value *OOp = FVI->getOperand(2-OpToFold); |
| // Avoid creating select between 2 constants unless it's selecting |
| // between 0, 1 and -1. |
| const APInt *OOpC; |
| bool OOpIsAPInt = match(OOp, m_APInt(OOpC)); |
| if (!isa<Constant>(OOp) || |
| (OOpIsAPInt && isSelect01(C->getUniqueInteger(), *OOpC))) { |
| Value *NewSel = Builder.CreateSelect(SI.getCondition(), C, OOp); |
| NewSel->takeName(FVI); |
| BinaryOperator *BO = BinaryOperator::Create(FVI->getOpcode(), |
| TrueVal, NewSel); |
| BO->copyIRFlags(FVI); |
| return BO; |
| } |
| } |
| } |
| } |
| } |
| |
| return nullptr; |
| } |
| |
| /// We want to turn: |
| /// (select (icmp eq (and X, Y), 0), (and (lshr X, Z), 1), 1) |
| /// into: |
| /// zext (icmp ne i32 (and X, (or Y, (shl 1, Z))), 0) |
| /// Note: |
| /// Z may be 0 if lshr is missing. |
| /// Worst-case scenario is that we will replace 5 instructions with 5 different |
| /// instructions, but we got rid of select. |
| static Instruction *foldSelectICmpAndAnd(Type *SelType, const ICmpInst *Cmp, |
| Value *TVal, Value *FVal, |
| InstCombiner::BuilderTy &Builder) { |
| if (!(Cmp->hasOneUse() && Cmp->getOperand(0)->hasOneUse() && |
| Cmp->getPredicate() == ICmpInst::ICMP_EQ && |
| match(Cmp->getOperand(1), m_Zero()) && match(FVal, m_One()))) |
| return nullptr; |
| |
| // The TrueVal has general form of: and %B, 1 |
| Value *B; |
| if (!match(TVal, m_OneUse(m_And(m_Value(B), m_One())))) |
| return nullptr; |
| |
| // Where %B may be optionally shifted: lshr %X, %Z. |
| Value *X, *Z; |
| const bool HasShift = match(B, m_OneUse(m_LShr(m_Value(X), m_Value(Z)))); |
| if (!HasShift) |
| X = B; |
| |
| Value *Y; |
| if (!match(Cmp->getOperand(0), m_c_And(m_Specific(X), m_Value(Y)))) |
| return nullptr; |
| |
| // ((X & Y) == 0) ? ((X >> Z) & 1) : 1 --> (X & (Y | (1 << Z))) != 0 |
| // ((X & Y) == 0) ? (X & 1) : 1 --> (X & (Y | 1)) != 0 |
| Constant *One = ConstantInt::get(SelType, 1); |
| Value *MaskB = HasShift ? Builder.CreateShl(One, Z) : One; |
| Value *FullMask = Builder.CreateOr(Y, MaskB); |
| Value *MaskedX = Builder.CreateAnd(X, FullMask); |
| Value *ICmpNeZero = Builder.CreateIsNotNull(MaskedX); |
| return new ZExtInst(ICmpNeZero, SelType); |
| } |
| |
| /// We want to turn: |
| /// (select (icmp sgt x, C), lshr (X, Y), ashr (X, Y)); iff C s>= -1 |
| /// (select (icmp slt x, C), ashr (X, Y), lshr (X, Y)); iff C s>= 0 |
| /// into: |
| /// ashr (X, Y) |
| static Value *foldSelectICmpLshrAshr(const ICmpInst *IC, Value *TrueVal, |
| Value *FalseVal, |
| InstCombiner::BuilderTy &Builder) { |
| ICmpInst::Predicate Pred = IC->getPredicate(); |
| Value *CmpLHS = IC->getOperand(0); |
| Value *CmpRHS = IC->getOperand(1); |
| if (!CmpRHS->getType()->isIntOrIntVectorTy()) |
| return nullptr; |
| |
| Value *X, *Y; |
| unsigned Bitwidth = CmpRHS->getType()->getScalarSizeInBits(); |
| if ((Pred != ICmpInst::ICMP_SGT || |
| !match(CmpRHS, |
| m_SpecificInt_ICMP(ICmpInst::ICMP_SGE, APInt(Bitwidth, -1)))) && |
| (Pred != ICmpInst::ICMP_SLT || |
| !match(CmpRHS, |
| m_SpecificInt_ICMP(ICmpInst::ICMP_SGE, APInt(Bitwidth, 0))))) |
| return nullptr; |
| |
| // Canonicalize so that ashr is in FalseVal. |
| if (Pred == ICmpInst::ICMP_SLT) |
| std::swap(TrueVal, FalseVal); |
| |
| if (match(TrueVal, m_LShr(m_Value(X), m_Value(Y))) && |
| match(FalseVal, m_AShr(m_Specific(X), m_Specific(Y))) && |
| match(CmpLHS, m_Specific(X))) { |
| const auto *Ashr = cast<Instruction>(FalseVal); |
| // if lshr is not exact and ashr is, this new ashr must not be exact. |
| bool IsExact = Ashr->isExact() && cast<Instruction>(TrueVal)->isExact(); |
| return Builder.CreateAShr(X, Y, IC->getName(), IsExact); |
| } |
| |
| return nullptr; |
| } |
| |
| /// We want to turn: |
| /// (select (icmp eq (and X, C1), 0), Y, (or Y, C2)) |
| /// into: |
| /// (or (shl (and X, C1), C3), Y) |
| /// iff: |
| /// C1 and C2 are both powers of 2 |
| /// where: |
| /// C3 = Log(C2) - Log(C1) |
| /// |
| /// This transform handles cases where: |
| /// 1. The icmp predicate is inverted |
| /// 2. The select operands are reversed |
| /// 3. The magnitude of C2 and C1 are flipped |
| static Value *foldSelectICmpAndOr(const ICmpInst *IC, Value *TrueVal, |
| Value *FalseVal, |
| InstCombiner::BuilderTy &Builder) { |
| // Only handle integer compares. Also, if this is a vector select, we need a |
| // vector compare. |
| if (!TrueVal->getType()->isIntOrIntVectorTy() || |
| TrueVal->getType()->isVectorTy() != IC->getType()->isVectorTy()) |
| return nullptr; |
| |
| Value *CmpLHS = IC->getOperand(0); |
| Value *CmpRHS = IC->getOperand(1); |
| |
| Value *V; |
| unsigned C1Log; |
| bool IsEqualZero; |
| bool NeedAnd = false; |
| if (IC->isEquality()) { |
| if (!match(CmpRHS, m_Zero())) |
| return nullptr; |
| |
| const APInt *C1; |
| if (!match(CmpLHS, m_And(m_Value(), m_Power2(C1)))) |
| return nullptr; |
| |
| V = CmpLHS; |
| C1Log = C1->logBase2(); |
| IsEqualZero = IC->getPredicate() == ICmpInst::ICMP_EQ; |
| } else if (IC->getPredicate() == ICmpInst::ICMP_SLT || |
| IC->getPredicate() == ICmpInst::ICMP_SGT) { |
| // We also need to recognize (icmp slt (trunc (X)), 0) and |
| // (icmp sgt (trunc (X)), -1). |
| IsEqualZero = IC->getPredicate() == ICmpInst::ICMP_SGT; |
| if ((IsEqualZero && !match(CmpRHS, m_AllOnes())) || |
| (!IsEqualZero && !match(CmpRHS, m_Zero()))) |
| return nullptr; |
| |
| if (!match(CmpLHS, m_OneUse(m_Trunc(m_Value(V))))) |
| return nullptr; |
| |
| C1Log = CmpLHS->getType()->getScalarSizeInBits() - 1; |
| NeedAnd = true; |
| } else { |
| return nullptr; |
| } |
| |
| const APInt *C2; |
| bool OrOnTrueVal = false; |
| bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2))); |
| if (!OrOnFalseVal) |
| OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2))); |
| |
| if (!OrOnFalseVal && !OrOnTrueVal) |
| return nullptr; |
| |
| Value *Y = OrOnFalseVal ? TrueVal : FalseVal; |
| |
| unsigned C2Log = C2->logBase2(); |
| |
| bool NeedXor = (!IsEqualZero && OrOnFalseVal) || (IsEqualZero && OrOnTrueVal); |
| bool NeedShift = C1Log != C2Log; |
| bool NeedZExtTrunc = Y->getType()->getScalarSizeInBits() != |
| V->getType()->getScalarSizeInBits(); |
| |
| // Make sure we don't create more instructions than we save. |
| Value *Or = OrOnFalseVal ? FalseVal : TrueVal; |
| if ((NeedShift + NeedXor + NeedZExtTrunc) > |
| (IC->hasOneUse() + Or->hasOneUse())) |
| return nullptr; |
| |
| if (NeedAnd) { |
| // Insert the AND instruction on the input to the truncate. |
| APInt C1 = APInt::getOneBitSet(V->getType()->getScalarSizeInBits(), C1Log); |
| V = Builder.CreateAnd(V, ConstantInt::get(V->getType(), C1)); |
| } |
| |
| if (C2Log > C1Log) { |
| V = Builder.CreateZExtOrTrunc(V, Y->getType()); |
| V = Builder.CreateShl(V, C2Log - C1Log); |
| } else if (C1Log > C2Log) { |
| V = Builder.CreateLShr(V, C1Log - C2Log); |
| V = Builder.CreateZExtOrTrunc(V, Y->getType()); |
| } else |
| V = Builder.CreateZExtOrTrunc(V, Y->getType()); |
| |
| if (NeedXor) |
| V = Builder.CreateXor(V, *C2); |
| |
| return Builder.CreateOr(V, Y); |
| } |
| |
| /// Canonicalize a set or clear of a masked set of constant bits to |
| /// select-of-constants form. |
| static Instruction *foldSetClearBits(SelectInst &Sel, |
| InstCombiner::BuilderTy &Builder) { |
| Value *Cond = Sel.getCondition(); |
| Value *T = Sel.getTrueValue(); |
| Value *F = Sel.getFalseValue(); |
| Type *Ty = Sel.getType(); |
| Value *X; |
| const APInt *NotC, *C; |
| |
| // Cond ? (X & ~C) : (X | C) --> (X & ~C) | (Cond ? 0 : C) |
| if (match(T, m_And(m_Value(X), m_APInt(NotC))) && |
| match(F, m_OneUse(m_Or(m_Specific(X), m_APInt(C)))) && *NotC == ~(*C)) { |
| Constant *Zero = ConstantInt::getNullValue(Ty); |
| Constant *OrC = ConstantInt::get(Ty, *C); |
| Value *NewSel = Builder.CreateSelect(Cond, Zero, OrC, "masksel", &Sel); |
| return BinaryOperator::CreateOr(T, NewSel); |
| } |
| |
| // Cond ? (X | C) : (X & ~C) --> (X & ~C) | (Cond ? C : 0) |
| if (match(F, m_And(m_Value(X), m_APInt(NotC))) && |
| match(T, m_OneUse(m_Or(m_Specific(X), m_APInt(C)))) && *NotC == ~(*C)) { |
| Constant *Zero = ConstantInt::getNullValue(Ty); |
| Constant *OrC = ConstantInt::get(Ty, *C); |
| Value *NewSel = Builder.CreateSelect(Cond, OrC, Zero, "masksel", &Sel); |
| return BinaryOperator::CreateOr(F, NewSel); |
| } |
| |
| return nullptr; |
| } |
| |
| // select (x == 0), 0, x * y --> freeze(y) * x |
| // select (y == 0), 0, x * y --> freeze(x) * y |
| // select (x == 0), undef, x * y --> freeze(y) * x |
| // select (x == undef), 0, x * y --> freeze(y) * x |
| // Usage of mul instead of 0 will make the result more poisonous, |
| // so the operand that was not checked in the condition should be frozen. |
| // The latter folding is applied only when a constant compared with x is |
| // is a vector consisting of 0 and undefs. If a constant compared with x |
| // is a scalar undefined value or undefined vector then an expression |
| // should be already folded into a constant. |
| static Instruction *foldSelectZeroOrMul(SelectInst &SI, InstCombinerImpl &IC) { |
| auto *CondVal = SI.getCondition(); |
| auto *TrueVal = SI.getTrueValue(); |
| auto *FalseVal = SI.getFalseValue(); |
| Value *X, *Y; |
| ICmpInst::Predicate Predicate; |
| |
| // Assuming that constant compared with zero is not undef (but it may be |
| // a vector with some undef elements). Otherwise (when a constant is undef) |
| // the select expression should be already simplified. |
| if (!match(CondVal, m_ICmp(Predicate, m_Value(X), m_Zero())) || |
| !ICmpInst::isEquality(Predicate)) |
| return nullptr; |
| |
| if (Predicate == ICmpInst::ICMP_NE) |
| std::swap(TrueVal, FalseVal); |
| |
| // Check that TrueVal is a constant instead of matching it with m_Zero() |
| // to handle the case when it is a scalar undef value or a vector containing |
| // non-zero elements that are masked by undef elements in the compare |
| // constant. |
| auto *TrueValC = dyn_cast<Constant>(TrueVal); |
| if (TrueValC == nullptr || |
| !match(FalseVal, m_c_Mul(m_Specific(X), m_Value(Y))) || |
| !isa<Instruction>(FalseVal)) |
| return nullptr; |
| |
| auto *ZeroC = cast<Constant>(cast<Instruction>(CondVal)->getOperand(1)); |
| auto *MergedC = Constant::mergeUndefsWith(TrueValC, ZeroC); |
| // If X is compared with 0 then TrueVal could be either zero or undef. |
| // m_Zero match vectors containing some undef elements, but for scalars |
| // m_Undef should be used explicitly. |
| if (!match(MergedC, m_Zero()) && !match(MergedC, m_Undef())) |
| return nullptr; |
| |
| auto *FalseValI = cast<Instruction>(FalseVal); |
| auto *FrY = IC.InsertNewInstBefore(new FreezeInst(Y, Y->getName() + ".fr"), |
| *FalseValI); |
| IC.replaceOperand(*FalseValI, FalseValI->getOperand(0) == Y ? 0 : 1, FrY); |
| return IC.replaceInstUsesWith(SI, FalseValI); |
| } |
| |
| /// Transform patterns such as (a > b) ? a - b : 0 into usub.sat(a, b). |
| /// There are 8 commuted/swapped variants of this pattern. |
| /// TODO: Also support a - UMIN(a,b) patterns. |
| static Value *canonicalizeSaturatedSubtract(const ICmpInst *ICI, |
| const Value *TrueVal, |
| const Value *FalseVal, |
| InstCombiner::BuilderTy &Builder) { |
| ICmpInst::Predicate Pred = ICI->getPredicate(); |
| if (!ICmpInst::isUnsigned(Pred)) |
| return nullptr; |
| |
| // (b > a) ? 0 : a - b -> (b <= a) ? a - b : 0 |
| if (match(TrueVal, m_Zero())) { |
| Pred = ICmpInst::getInversePredicate(Pred); |
| std::swap(TrueVal, FalseVal); |
| } |
| if (!match(FalseVal, m_Zero())) |
| return nullptr; |
| |
| Value *A = ICI->getOperand(0); |
| Value *B = ICI->getOperand(1); |
| if (Pred == ICmpInst::ICMP_ULE || Pred == ICmpInst::ICMP_ULT) { |
| // (b < a) ? a - b : 0 -> (a > b) ? a - b : 0 |
| std::swap(A, B); |
| Pred = ICmpInst::getSwappedPredicate(Pred); |
| } |
| |
| assert((Pred == ICmpInst::ICMP_UGE || Pred == ICmpInst::ICMP_UGT) && |
| "Unexpected isUnsigned predicate!"); |
| |
| // Ensure the sub is of the form: |
| // (a > b) ? a - b : 0 -> usub.sat(a, b) |
| // (a > b) ? b - a : 0 -> -usub.sat(a, b) |
| // Checking for both a-b and a+(-b) as a constant. |
| bool IsNegative = false; |
| const APInt *C; |
| if (match(TrueVal, m_Sub(m_Specific(B), m_Specific(A))) || |
| (match(A, m_APInt(C)) && |
| match(TrueVal, m_Add(m_Specific(B), m_SpecificInt(-*C))))) |
| IsNegative = true; |
| else if (!match(TrueVal, m_Sub(m_Specific(A), m_Specific(B))) && |
| !(match(B, m_APInt(C)) && |
| match(TrueVal, m_Add(m_Specific(A), m_SpecificInt(-*C))))) |
| return nullptr; |
| |
| // If we are adding a negate and the sub and icmp are used anywhere else, we |
| // would end up with more instructions. |
| if (IsNegative && !TrueVal->hasOneUse() && !ICI->hasOneUse()) |
| return nullptr; |
| |
| // (a > b) ? a - b : 0 -> usub.sat(a, b) |
| // (a > b) ? b - a : 0 -> -usub.sat(a, b) |
| Value *Result = Builder.CreateBinaryIntrinsic(Intrinsic::usub_sat, A, B); |
| if (IsNegative) |
| Result = Builder.CreateNeg(Result); |
| return Result; |
| } |
| |
| static Value *canonicalizeSaturatedAdd(ICmpInst *Cmp, Value *TVal, Value *FVal, |
| InstCombiner::BuilderTy &Builder) { |
| if (!Cmp->hasOneUse()) |
| return nullptr; |
| |
| // Match unsigned saturated add with constant. |
| Value *Cmp0 = Cmp->getOperand(0); |
| Value *Cmp1 = Cmp->getOperand(1); |
| ICmpInst::Predicate Pred = Cmp->getPredicate(); |
| Value *X; |
| const APInt *C, *CmpC; |
| if (Pred == ICmpInst::ICMP_ULT && |
| match(TVal, m_Add(m_Value(X), m_APInt(C))) && X == Cmp0 && |
| match(FVal, m_AllOnes()) && match(Cmp1, m_APInt(CmpC)) && *CmpC == ~*C) { |
| // (X u< ~C) ? (X + C) : -1 --> uadd.sat(X, C) |
| return Builder.CreateBinaryIntrinsic( |
| Intrinsic::uadd_sat, X, ConstantInt::get(X->getType(), *C)); |
| } |
| |
| // Match unsigned saturated add of 2 variables with an unnecessary 'not'. |
| // There are 8 commuted variants. |
| // Canonicalize -1 (saturated result) to true value of the select. |
| if (match(FVal, m_AllOnes())) { |
| std::swap(TVal, FVal); |
| Pred = CmpInst::getInversePredicate(Pred); |
| } |
| if (!match(TVal, m_AllOnes())) |
| return nullptr; |
| |
| // Canonicalize predicate to less-than or less-or-equal-than. |
| if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) { |
| std::swap(Cmp0, Cmp1); |
| Pred = CmpInst::getSwappedPredicate(Pred); |
| } |
| if (Pred != ICmpInst::ICMP_ULT && Pred != ICmpInst::ICMP_ULE) |
| return nullptr; |
| |
| // Match unsigned saturated add of 2 variables with an unnecessary 'not'. |
| // Strictness of the comparison is irrelevant. |
| Value *Y; |
| if (match(Cmp0, m_Not(m_Value(X))) && |
| match(FVal, m_c_Add(m_Specific(X), m_Value(Y))) && Y == Cmp1) { |
| // (~X u< Y) ? -1 : (X + Y) --> uadd.sat(X, Y) |
| // (~X u< Y) ? -1 : (Y + X) --> uadd.sat(X, Y) |
| return Builder.CreateBinaryIntrinsic(Intrinsic::uadd_sat, X, Y); |
| } |
| // The 'not' op may be included in the sum but not the compare. |
| // Strictness of the comparison is irrelevant. |
| X = Cmp0; |
| Y = Cmp1; |
| if (match(FVal, m_c_Add(m_Not(m_Specific(X)), m_Specific(Y)))) { |
| // (X u< Y) ? -1 : (~X + Y) --> uadd.sat(~X, Y) |
| // (X u< Y) ? -1 : (Y + ~X) --> uadd.sat(Y, ~X) |
| BinaryOperator *BO = cast<BinaryOperator>(FVal); |
| return Builder.CreateBinaryIntrinsic( |
| Intrinsic::uadd_sat, BO->getOperand(0), BO->getOperand(1)); |
| } |
| // The overflow may be detected via the add wrapping round. |
| // This is only valid for strict comparison! |
| if (Pred == ICmpInst::ICMP_ULT && |
| match(Cmp0, m_c_Add(m_Specific(Cmp1), m_Value(Y))) && |
| match(FVal, m_c_Add(m_Specific(Cmp1), m_Specific(Y)))) { |
| // ((X + Y) u< X) ? -1 : (X + Y) --> uadd.sat(X, Y) |
| // ((X + Y) u< Y) ? -1 : (X + Y) --> uadd.sat(X, Y) |
| return Builder.CreateBinaryIntrinsic(Intrinsic::uadd_sat, Cmp1, Y); |
| } |
| |
| return nullptr; |
| } |
| |
| /// Fold the following code sequence: |
| /// \code |
| /// int a = ctlz(x & -x); |
| // x ? 31 - a : a; |
| /// \code |
| /// |
| /// into: |
| /// cttz(x) |
| static Instruction *foldSelectCtlzToCttz(ICmpInst *ICI, Value *TrueVal, |
| Value *FalseVal, |
| InstCombiner::BuilderTy &Builder) { |
| unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits(); |
| if (!ICI->isEquality() || !match(ICI->getOperand(1), m_Zero())) |
| return nullptr; |
| |
| if (ICI->getPredicate() == ICmpInst::ICMP_NE) |
| std::swap(TrueVal, FalseVal); |
| |
| if (!match(FalseVal, |
| m_Xor(m_Deferred(TrueVal), m_SpecificInt(BitWidth - 1)))) |
| return nullptr; |
| |
| if (!match(TrueVal, m_Intrinsic<Intrinsic::ctlz>())) |
| return nullptr; |
| |
| Value *X = ICI->getOperand(0); |
| auto *II = cast<IntrinsicInst>(TrueVal); |
| if (!match(II->getOperand(0), m_c_And(m_Specific(X), m_Neg(m_Specific(X))))) |
| return nullptr; |
| |
| Function *F = Intrinsic::getDeclaration(II->getModule(), Intrinsic::cttz, |
| II->getType()); |
| return CallInst::Create(F, {X, II->getArgOperand(1)}); |
| } |
| |
| /// Attempt to fold a cttz/ctlz followed by a icmp plus select into a single |
| /// call to cttz/ctlz with flag 'is_zero_undef' cleared. |
| /// |
| /// For example, we can fold the following code sequence: |
| /// \code |
| /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 true) |
| /// %1 = icmp ne i32 %x, 0 |
| /// %2 = select i1 %1, i32 %0, i32 32 |
| /// \code |
| /// |
| /// into: |
| /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 false) |
| static Value *foldSelectCttzCtlz(ICmpInst *ICI, Value *TrueVal, Value *FalseVal, |
| InstCombiner::BuilderTy &Builder) { |
| ICmpInst::Predicate Pred = ICI->getPredicate(); |
| Value *CmpLHS = ICI->getOperand(0); |
| Value *CmpRHS = ICI->getOperand(1); |
| |
| // Check if the condition value compares a value for equality against zero. |
| if (!ICI->isEquality() || !match(CmpRHS, m_Zero())) |
| return nullptr; |
| |
| Value *SelectArg = FalseVal; |
| Value *ValueOnZero = TrueVal; |
| if (Pred == ICmpInst::ICMP_NE) |
| std::swap(SelectArg, ValueOnZero); |
| |
| // Skip zero extend/truncate. |
| Value *Count = nullptr; |
| if (!match(SelectArg, m_ZExt(m_Value(Count))) && |
| !match(SelectArg, m_Trunc(m_Value(Count)))) |
| Count = SelectArg; |
| |
| // Check that 'Count' is a call to intrinsic cttz/ctlz. Also check that the |
| // input to the cttz/ctlz is used as LHS for the compare instruction. |
| if (!match(Count, m_Intrinsic<Intrinsic::cttz>(m_Specific(CmpLHS))) && |
| !match(Count, m_Intrinsic<Intrinsic::ctlz>(m_Specific(CmpLHS)))) |
| return nullptr; |
| |
| IntrinsicInst *II = cast<IntrinsicInst>(Count); |
| |
| // Check if the value propagated on zero is a constant number equal to the |
| // sizeof in bits of 'Count'. |
| unsigned SizeOfInBits = Count->getType()->getScalarSizeInBits(); |
| if (match(ValueOnZero, m_SpecificInt(SizeOfInBits))) { |
| // Explicitly clear the 'undef_on_zero' flag. It's always valid to go from |
| // true to false on this flag, so we can replace it for all users. |
| II->setArgOperand(1, ConstantInt::getFalse(II->getContext())); |
| return SelectArg; |
| } |
| |
| // The ValueOnZero is not the bitwidth. But if the cttz/ctlz (and optional |
| // zext/trunc) have one use (ending at the select), the cttz/ctlz result will |
| // not be used if the input is zero. Relax to 'undef_on_zero' for that case. |
| if (II->hasOneUse() && SelectArg->hasOneUse() && |
| !match(II->getArgOperand(1), m_One())) |
| II->setArgOperand(1, ConstantInt::getTrue(II->getContext())); |
| |
| return nullptr; |
| } |
| |
| /// Return true if we find and adjust an icmp+select pattern where the compare |
| /// is with a constant that can be incremented or decremented to match the |
| /// minimum or maximum idiom. |
| static bool adjustMinMax(SelectInst &Sel, ICmpInst &Cmp) { |
| ICmpInst::Predicate Pred = Cmp.getPredicate(); |
| Value *CmpLHS = Cmp.getOperand(0); |
| Value *CmpRHS = Cmp.getOperand(1); |
| Value *TrueVal = Sel.getTrueValue(); |
| Value *FalseVal = Sel.getFalseValue(); |
| |
| // We may move or edit the compare, so make sure the select is the only user. |
| const APInt *CmpC; |
| if (!Cmp.hasOneUse() || !match(CmpRHS, m_APInt(CmpC))) |
| return false; |
| |
| // These transforms only work for selects of integers or vector selects of |
| // integer vectors. |
| Type *SelTy = Sel.getType(); |
| auto *SelEltTy = dyn_cast<IntegerType>(SelTy->getScalarType()); |
| if (!SelEltTy || SelTy->isVectorTy() != Cmp.getType()->isVectorTy()) |
| return false; |
| |
| Constant *AdjustedRHS; |
| if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT) |
| AdjustedRHS = ConstantInt::get(CmpRHS->getType(), *CmpC + 1); |
| else if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT) |
| AdjustedRHS = ConstantInt::get(CmpRHS->getType(), *CmpC - 1); |
| else |
| return false; |
| |
| // X > C ? X : C+1 --> X < C+1 ? C+1 : X |
| // X < C ? X : C-1 --> X > C-1 ? C-1 : X |
| if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) || |
| (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) { |
| ; // Nothing to do here. Values match without any sign/zero extension. |
| } |
| // Types do not match. Instead of calculating this with mixed types, promote |
| // all to the larger type. This enables scalar evolution to analyze this |
| // expression. |
| else if (CmpRHS->getType()->getScalarSizeInBits() < SelEltTy->getBitWidth()) { |
| Constant *SextRHS = ConstantExpr::getSExt(AdjustedRHS, SelTy); |
| |
| // X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X |
| // X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X |
| // X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X |
| // X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X |
| if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) && SextRHS == FalseVal) { |
| CmpLHS = TrueVal; |
| AdjustedRHS = SextRHS; |
| } else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) && |
| SextRHS == TrueVal) { |
| CmpLHS = FalseVal; |
| AdjustedRHS = SextRHS; |
| } else if (Cmp.isUnsigned()) { |
| Constant *ZextRHS = ConstantExpr::getZExt(AdjustedRHS, SelTy); |
| // X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X |
| // X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X |
| // zext + signed compare cannot be changed: |
| // 0xff <s 0x00, but 0x00ff >s 0x0000 |
| if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) && ZextRHS == FalseVal) { |
| CmpLHS = TrueVal; |
| AdjustedRHS = ZextRHS; |
| } else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) && |
| ZextRHS == TrueVal) { |
| CmpLHS = FalseVal; |
| AdjustedRHS = ZextRHS; |
| } else { |
| return false; |
| } |
| } else { |
| return false; |
| } |
| } else { |
| return false; |
| } |
| |
| Pred = ICmpInst::getSwappedPredicate(Pred); |
| CmpRHS = AdjustedRHS; |
| std::swap(FalseVal, TrueVal); |
| Cmp.setPredicate(Pred); |
| Cmp.setOperand(0, CmpLHS); |
| Cmp.setOperand(1, CmpRHS); |
| Sel.setOperand(1, TrueVal); |
| Sel.setOperand(2, FalseVal); |
| Sel.swapProfMetadata(); |
| |
| // Move the compare instruction right before the select instruction. Otherwise |
| // the sext/zext value may be defined after the compare instruction uses it. |
| Cmp.moveBefore(&Sel); |
| |
| return true; |
| } |
| |
| /// If this is an integer min/max (icmp + select) with a constant operand, |
| /// create the canonical icmp for the min/max operation and canonicalize the |
| /// constant to the 'false' operand of the select: |
| /// select (icmp Pred X, C1), C2, X --> select (icmp Pred' X, C2), X, C2 |
| /// Note: if C1 != C2, this will change the icmp constant to the existing |
| /// constant operand of the select. |
| static Instruction *canonicalizeMinMaxWithConstant(SelectInst &Sel, |
| ICmpInst &Cmp, |
| InstCombinerImpl &IC) { |
| if (!Cmp.hasOneUse() || !isa<Constant>(Cmp.getOperand(1))) |
| return nullptr; |
| |
| // Canonicalize the compare predicate based on whether we have min or max. |
| Value *LHS, *RHS; |
| SelectPatternResult SPR = matchSelectPattern(&Sel, LHS, RHS); |
| if (!SelectPatternResult::isMinOrMax(SPR.Flavor)) |
| return nullptr; |
| |
| // Is this already canonical? |
| ICmpInst::Predicate CanonicalPred = getMinMaxPred(SPR.Flavor); |
| if (Cmp.getOperand(0) == LHS && Cmp.getOperand(1) == RHS && |
| Cmp.getPredicate() == CanonicalPred) |
| return nullptr; |
| |
| // Bail out on unsimplified X-0 operand (due to some worklist management bug), |
| // as this may cause an infinite combine loop. Let the sub be folded first. |
| if (match(LHS, m_Sub(m_Value(), m_Zero())) || |
| match(RHS, m_Sub(m_Value(), m_Zero()))) |
| return nullptr; |
| |
| // Create the canonical compare and plug it into the select. |
| IC.replaceOperand(Sel, 0, IC.Builder.CreateICmp(CanonicalPred, LHS, RHS)); |
| |
| // If the select operands did not change, we're done. |
| if (Sel.getTrueValue() == LHS && Sel.getFalseValue() == RHS) |
| return &Sel; |
| |
| // If we are swapping the select operands, swap the metadata too. |
| assert(Sel.getTrueValue() == RHS && Sel.getFalseValue() == LHS && |
| "Unexpected results from matchSelectPattern"); |
| Sel.swapValues(); |
| Sel.swapProfMetadata(); |
| return &Sel; |
| } |
| |
| static Instruction *canonicalizeAbsNabs(SelectInst &Sel, ICmpInst &Cmp, |
| InstCombinerImpl &IC) { |
| if (!Cmp.hasOneUse() || !isa<Constant>(Cmp.getOperand(1))) |
| return nullptr; |
| |
| Value *LHS, *RHS; |
| SelectPatternFlavor SPF = matchSelectPattern(&Sel, LHS, RHS).Flavor; |
| if (SPF != SelectPatternFlavor::SPF_ABS && |
| SPF != SelectPatternFlavor::SPF_NABS) |
| return nullptr; |
| |
| // Note that NSW flag can only be propagated for normal, non-negated abs! |
| bool IntMinIsPoison = SPF == SelectPatternFlavor::SPF_ABS && |
| match(RHS, m_NSWNeg(m_Specific(LHS))); |
| Constant *IntMinIsPoisonC = |
| ConstantInt::get(Type::getInt1Ty(Sel.getContext()), IntMinIsPoison); |
| Instruction *Abs = |
| IC.Builder.CreateBinaryIntrinsic(Intrinsic::abs, LHS, IntMinIsPoisonC); |
| |
| if (SPF == SelectPatternFlavor::SPF_NABS) |
| return BinaryOperator::CreateNeg(Abs); // Always without NSW flag! |
| |
| return IC.replaceInstUsesWith(Sel, Abs); |
| } |
| |
| /// If we have a select with an equality comparison, then we know the value in |
| /// one of the arms of the select. See if substituting this value into an arm |
| /// and simplifying the result yields the same value as the other arm. |
| /// |
| /// To make this transform safe, we must drop poison-generating flags |
| /// (nsw, etc) if we simplified to a binop because the select may be guarding |
| /// that poison from propagating. If the existing binop already had no |
| /// poison-generating flags, then this transform can be done by instsimplify. |
| /// |
| /// Consider: |
| /// %cmp = icmp eq i32 %x, 2147483647 |
| /// %add = add nsw i32 %x, 1 |
| /// %sel = select i1 %cmp, i32 -2147483648, i32 %add |
| /// |
| /// We can't replace %sel with %add unless we strip away the flags. |
| /// TODO: Wrapping flags could be preserved in some cases with better analysis. |
| Instruction *InstCombinerImpl::foldSelectValueEquivalence(SelectInst &Sel, |
| ICmpInst &Cmp) { |
| // Value equivalence substitution requires an all-or-nothing replacement. |
| // It does not make sense for a vector compare where each lane is chosen |
| // independently. |
| if (!Cmp.isEquality() || Cmp.getType()->isVectorTy()) |
| return nullptr; |
| |
| // Canonicalize the pattern to ICMP_EQ by swapping the select operands. |
| Value *TrueVal = Sel.getTrueValue(), *FalseVal = Sel.getFalseValue(); |
| bool Swapped = false; |
| if (Cmp.getPredicate() == ICmpInst::ICMP_NE) { |
| std::swap(TrueVal, FalseVal); |
| Swapped = true; |
| } |
| |
| // In X == Y ? f(X) : Z, try to evaluate f(Y) and replace the operand. |
| // Make sure Y cannot be undef though, as we might pick different values for |
| // undef in the icmp and in f(Y). Additionally, take care to avoid replacing |
| // X == Y ? X : Z with X == Y ? Y : Z, as that would lead to an infinite |
| // replacement cycle. |
| Value *CmpLHS = Cmp.getOperand(0), *CmpRHS = Cmp.getOperand(1); |
| if (TrueVal != CmpLHS && |
| isGuaranteedNotToBeUndefOrPoison(CmpRHS, SQ.AC, &Sel, &DT)) { |
| if (Value *V = simplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, SQ, |
| /* AllowRefinement */ true)) |
| return replaceOperand(Sel, Swapped ? 2 : 1, V); |
| |
| // Even if TrueVal does not simplify, we can directly replace a use of |
| // CmpLHS with CmpRHS, as long as the instruction is not used anywhere |
| // else and is safe to speculatively execute (we may end up executing it |
| // with different operands, which should not cause side-effects or trigger |
| // undefined behavior). Only do this if CmpRHS is a constant, as |
| // profitability is not clear for other cases. |
| // FIXME: The replacement could be performed recursively. |
| if (match(CmpRHS, m_ImmConstant()) && !match(CmpLHS, m_ImmConstant())) |
| if (auto *I = dyn_cast<Instruction>(TrueVal)) |
| if (I->hasOneUse() && isSafeToSpeculativelyExecute(I)) |
| for (Use &U : I->operands()) |
| if (U == CmpLHS) { |
| replaceUse(U, CmpRHS); |
| return &Sel; |
| } |
| } |
| if (TrueVal != CmpRHS && |
| isGuaranteedNotToBeUndefOrPoison(CmpLHS, SQ.AC, &Sel, &DT)) |
| if (Value *V = simplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, SQ, |
| /* AllowRefinement */ true)) |
| return replaceOperand(Sel, Swapped ? 2 : 1, V); |
| |
| auto *FalseInst = dyn_cast<Instruction>(FalseVal); |
| if (!FalseInst) |
| return nullptr; |
| |
| // InstSimplify already performed this fold if it was possible subject to |
| // current poison-generating flags. Try the transform again with |
| // poison-generating flags temporarily dropped. |
| bool WasNUW = false, WasNSW = false, WasExact = false, WasInBounds = false; |
| if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(FalseVal)) { |
| WasNUW = OBO->hasNoUnsignedWrap(); |
| WasNSW = OBO->hasNoSignedWrap(); |
| FalseInst->setHasNoUnsignedWrap(false); |
| FalseInst->setHasNoSignedWrap(false); |
| } |
| if (auto *PEO = dyn_cast<PossiblyExactOperator>(FalseVal)) { |
| WasExact = PEO->isExact(); |
| FalseInst->setIsExact(false); |
| } |
| if (auto *GEP = dyn_cast<GetElementPtrInst>(FalseVal)) { |
| WasInBounds = GEP->isInBounds(); |
| GEP->setIsInBounds(false); |
| } |
| |
| // Try each equivalence substitution possibility. |
| // We have an 'EQ' comparison, so the select's false value will propagate. |
| // Example: |
| // (X == 42) ? 43 : (X + 1) --> (X == 42) ? (X + 1) : (X + 1) --> X + 1 |
| if (simplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, SQ, |
| /* AllowRefinement */ false) == TrueVal || |
| simplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, SQ, |
| /* AllowRefinement */ false) == TrueVal) { |
| return replaceInstUsesWith(Sel, FalseVal); |
| } |
| |
| // Restore poison-generating flags if the transform did not apply. |
| if (WasNUW) |
| FalseInst->setHasNoUnsignedWrap(); |
| if (WasNSW) |
| FalseInst->setHasNoSignedWrap(); |
| if (WasExact) |
| FalseInst->setIsExact(); |
| if (WasInBounds) |
| cast<GetElementPtrInst>(FalseInst)->setIsInBounds(); |
| |
| return nullptr; |
| } |
| |
| // See if this is a pattern like: |
| // %old_cmp1 = icmp slt i32 %x, C2 |
| // %old_replacement = select i1 %old_cmp1, i32 %target_low, i32 %target_high |
| // %old_x_offseted = add i32 %x, C1 |
| // %old_cmp0 = icmp ult i32 %old_x_offseted, C0 |
| // %r = select i1 %old_cmp0, i32 %x, i32 %old_replacement |
| // This can be rewritten as more canonical pattern: |
| // %new_cmp1 = icmp slt i32 %x, -C1 |
| // %new_cmp2 = icmp sge i32 %x, C0-C1 |
| // %new_clamped_low = select i1 %new_cmp1, i32 %target_low, i32 %x |
| // %r = select i1 %new_cmp2, i32 %target_high, i32 %new_clamped_low |
| // Iff -C1 s<= C2 s<= C0-C1 |
| // Also ULT predicate can also be UGT iff C0 != -1 (+invert result) |
| // SLT predicate can also be SGT iff C2 != INT_MAX (+invert res.) |
| static Value *canonicalizeClampLike(SelectInst &Sel0, ICmpInst &Cmp0, |
| InstCombiner::BuilderTy &Builder) { |
| Value *X = Sel0.getTrueValue(); |
| Value *Sel1 = Sel0.getFalseValue(); |
| |
| // First match the condition of the outermost select. |
| // Said condition must be one-use. |
| if (!Cmp0.hasOneUse()) |
| return nullptr; |
| ICmpInst::Predicate Pred0 = Cmp0.getPredicate(); |
| Value *Cmp00 = Cmp0.getOperand(0); |
| Constant *C0; |
| if (!match(Cmp0.getOperand(1), |
| m_CombineAnd(m_AnyIntegralConstant(), m_Constant(C0)))) |
| return nullptr; |
| |
| if (!isa<SelectInst>(Sel1)) { |
| Pred0 = ICmpInst::getInversePredicate(Pred0); |
| std::swap(X, Sel1); |
| } |
| |
| // Canonicalize Cmp0 into ult or uge. |
| // FIXME: we shouldn't care about lanes that are 'undef' in the end? |
| switch (Pred0) { |
| case ICmpInst::Predicate::ICMP_ULT: |
| case ICmpInst::Predicate::ICMP_UGE: |
| // Although icmp ult %x, 0 is an unusual thing to try and should generally |
| // have been simplified, it does not verify with undef inputs so ensure we |
| // are not in a strange state. |
| if (!match(C0, m_SpecificInt_ICMP( |
| ICmpInst::Predicate::ICMP_NE, |
| APInt::getZero(C0->getType()->getScalarSizeInBits())))) |
| return nullptr; |
| break; // Great! |
| case ICmpInst::Predicate::ICMP_ULE: |
| case ICmpInst::Predicate::ICMP_UGT: |
| // We want to canonicalize it to 'ult' or 'uge', so we'll need to increment |
| // C0, which again means it must not have any all-ones elements. |
| if (!match(C0, |
| m_SpecificInt_ICMP( |
| ICmpInst::Predicate::ICMP_NE, |
| APInt::getAllOnes(C0->getType()->getScalarSizeInBits())))) |
| return nullptr; // Can't do, have all-ones element[s]. |
| C0 = InstCombiner::AddOne(C0); |
| break; |
| default: |
| return nullptr; // Unknown predicate. |
| } |
| |
| // Now that we've canonicalized the ICmp, we know the X we expect; |
| // the select in other hand should be one-use. |
| if (!Sel1->hasOneUse()) |
| return nullptr; |
| |
| // If the types do not match, look through any truncs to the underlying |
| // instruction. |
| if (Cmp00->getType() != X->getType() && X->hasOneUse()) |
| match(X, m_TruncOrSelf(m_Value(X))); |
| |
| // We now can finish matching the condition of the outermost select: |
| // it should either be the X itself, or an addition of some constant to X. |
| Constant *C1; |
| if (Cmp00 == X) |
| C1 = ConstantInt::getNullValue(X->getType()); |
| else if (!match(Cmp00, |
| m_Add(m_Specific(X), |
| m_CombineAnd(m_AnyIntegralConstant(), m_Constant(C1))))) |
| return nullptr; |
| |
| Value *Cmp1; |
| ICmpInst::Predicate Pred1; |
| Constant *C2; |
| Value *ReplacementLow, *ReplacementHigh; |
| if (!match(Sel1, m_Select(m_Value(Cmp1), m_Value(ReplacementLow), |
| m_Value(ReplacementHigh))) || |
| !match(Cmp1, |
| m_ICmp(Pred1, m_Specific(X), |
| m_CombineAnd(m_AnyIntegralConstant(), m_Constant(C2))))) |
| return nullptr; |
| |
| if (!Cmp1->hasOneUse() && (Cmp00 == X || !Cmp00->hasOneUse())) |
| return nullptr; // Not enough one-use instructions for the fold. |
| // FIXME: this restriction could be relaxed if Cmp1 can be reused as one of |
| // two comparisons we'll need to build. |
| |
| // Canonicalize Cmp1 into the form we expect. |
| // FIXME: we shouldn't care about lanes that are 'undef' in the end? |
| switch (Pred1) { |
| case ICmpInst::Predicate::ICMP_SLT: |
| break; |
| case ICmpInst::Predicate::ICMP_SLE: |
| // We'd have to increment C2 by one, and for that it must not have signed |
| // max element, but then it would have been canonicalized to 'slt' before |
| // we get here. So we can't do anything useful with 'sle'. |
| return nullptr; |
| case ICmpInst::Predicate::ICMP_SGT: |
| // We want to canonicalize it to 'slt', so we'll need to increment C2, |
| // which again means it must not have any signed max elements. |
| if (!match(C2, |
| m_SpecificInt_ICMP(ICmpInst::Predicate::ICMP_NE, |
| APInt::getSignedMaxValue( |
| C2->getType()->getScalarSizeInBits())))) |
| return nullptr; // Can't do, have signed max element[s]. |
| C2 = InstCombiner::AddOne(C2); |
| LLVM_FALLTHROUGH; |
| case ICmpInst::Predicate::ICMP_SGE: |
| // Also non-canonical, but here we don't need to change C2, |
| // so we don't have any restrictions on C2, so we can just handle it. |
| std::swap(ReplacementLow, ReplacementHigh); |
| break; |
| default: |
| return nullptr; // Unknown predicate. |
| } |
| |
| // The thresholds of this clamp-like pattern. |
| auto *ThresholdLowIncl = ConstantExpr::getNeg(C1); |
| auto *ThresholdHighExcl = ConstantExpr::getSub(C0, C1); |
| if (Pred0 == ICmpInst::Predicate::ICMP_UGE) |
| std::swap(ThresholdLowIncl, ThresholdHighExcl); |
| |
| // The fold has a precondition 1: C2 s>= ThresholdLow |
| auto *Precond1 = ConstantExpr::getICmp(ICmpInst::Predicate::ICMP_SGE, C2, |
| ThresholdLowIncl); |
| if (!match(Precond1, m_One())) |
| return nullptr; |
| // The fold has a precondition 2: C2 s<= ThresholdHigh |
| auto *Precond2 = ConstantExpr::getICmp(ICmpInst::Predicate::ICMP_SLE, C2, |
| ThresholdHighExcl); |
| if (!match(Precond2, m_One())) |
| return nullptr; |
| |
| // If we are matching from a truncated input, we need to sext the |
| // ReplacementLow and ReplacementHigh values. Only do the transform if they |
| // are free to extend due to being constants. |
| if (X->getType() != Sel0.getType()) { |
| Constant *LowC, *HighC; |
| if (!match(ReplacementLow, m_ImmConstant(LowC)) || |
| !match(ReplacementHigh, m_ImmConstant(HighC))) |
| return nullptr; |
| ReplacementLow = ConstantExpr::getSExt(LowC, X->getType()); |
| ReplacementHigh = ConstantExpr::getSExt(HighC, X->getType()); |
| } |
| |
| // All good, finally emit the new pattern. |
| Value *ShouldReplaceLow = Builder.CreateICmpSLT(X, ThresholdLowIncl); |
| Value *ShouldReplaceHigh = Builder.CreateICmpSGE(X, ThresholdHighExcl); |
| Value *MaybeReplacedLow = |
| Builder.CreateSelect(ShouldReplaceLow, ReplacementLow, X); |
| |
| // Create the final select. If we looked through a truncate above, we will |
| // need to retruncate the result. |
| Value *MaybeReplacedHigh = Builder.CreateSelect( |
| ShouldReplaceHigh, ReplacementHigh, MaybeReplacedLow); |
| return Builder.CreateTrunc(MaybeReplacedHigh, Sel0.getType()); |
| } |
| |
| // If we have |
| // %cmp = icmp [canonical predicate] i32 %x, C0 |
| // %r = select i1 %cmp, i32 %y, i32 C1 |
| // Where C0 != C1 and %x may be different from %y, see if the constant that we |
| // will have if we flip the strictness of the predicate (i.e. without changing |
| // the result) is identical to the C1 in select. If it matches we can change |
| // original comparison to one with swapped predicate, reuse the constant, |
| // and swap the hands of select. |
| static Instruction * |
| tryToReuseConstantFromSelectInComparison(SelectInst &Sel, ICmpInst &Cmp, |
| InstCombinerImpl &IC) { |
| ICmpInst::Predicate Pred; |
| Value *X; |
| Constant *C0; |
| if (!match(&Cmp, m_OneUse(m_ICmp( |
| Pred, m_Value(X), |
| m_CombineAnd(m_AnyIntegralConstant(), m_Constant(C0)))))) |
| return nullptr; |
| |
| // If comparison predicate is non-relational, we won't be able to do anything. |
| if (ICmpInst::isEquality(Pred)) |
| return nullptr; |
| |
| // If comparison predicate is non-canonical, then we certainly won't be able |
| // to make it canonical; canonicalizeCmpWithConstant() already tried. |
| if (!InstCombiner::isCanonicalPredicate(Pred)) |
| return nullptr; |
| |
| // If the [input] type of comparison and select type are different, lets abort |
| // for now. We could try to compare constants with trunc/[zs]ext though. |
| if (C0->getType() != Sel.getType()) |
| return nullptr; |
| |
| // FIXME: are there any magic icmp predicate+constant pairs we must not touch? |
| |
| Value *SelVal0, *SelVal1; // We do not care which one is from where. |
| match(&Sel, m_Select(m_Value(), m_Value(SelVal0), m_Value(SelVal1))); |
| // At least one of these values we are selecting between must be a constant |
| // else we'll never succeed. |
| if (!match(SelVal0, m_AnyIntegralConstant()) && |
| !match(SelVal1, m_AnyIntegralConstant())) |
| return nullptr; |
| |
| // Does this constant C match any of the `select` values? |
| auto MatchesSelectValue = [SelVal0, SelVal1](Constant *C) { |
| return C->isElementWiseEqual(SelVal0) || C->isElementWiseEqual(SelVal1); |
| }; |
| |
| // If C0 *already* matches true/false value of select, we are done. |
| if (MatchesSelectValue(C0)) |
| return nullptr; |
| |
| // Check the constant we'd have with flipped-strictness predicate. |
| auto FlippedStrictness = |
| InstCombiner::getFlippedStrictnessPredicateAndConstant(Pred, C0); |
| if (!FlippedStrictness) |
| return nullptr; |
| |
| // If said constant doesn't match either, then there is no hope, |
| if (!MatchesSelectValue(FlippedStrictness->second)) |
| return nullptr; |
| |
| // It matched! Lets insert the new comparison just before select. |
| InstCombiner::BuilderTy::InsertPointGuard Guard(IC.Builder); |
| IC.Builder.SetInsertPoint(&Sel); |
| |
| Pred = ICmpInst::getSwappedPredicate(Pred); // Yes, swapped. |
| Value *NewCmp = IC.Builder.CreateICmp(Pred, X, FlippedStrictness->second, |
| Cmp.getName() + ".inv"); |
| IC.replaceOperand(Sel, 0, NewCmp); |
| Sel.swapValues(); |
| Sel.swapProfMetadata(); |
| |
| return &Sel; |
| } |
| |
| /// Visit a SelectInst that has an ICmpInst as its first operand. |
| Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI, |
| ICmpInst *ICI) { |
| if (Instruction *NewSel = foldSelectValueEquivalence(SI, *ICI)) |
| return NewSel; |
| |
| if (Instruction *NewSel = canonicalizeMinMaxWithConstant(SI, *ICI, *this)) |
| return NewSel; |
| |
| if (Instruction *NewAbs = canonicalizeAbsNabs(SI, *ICI, *this)) |
| return NewAbs; |
| |
| if (Value *V = canonicalizeClampLike(SI, *ICI, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| if (Instruction *NewSel = |
| tryToReuseConstantFromSelectInComparison(SI, *ICI, *this)) |
| return NewSel; |
| |
| bool Changed = adjustMinMax(SI, *ICI); |
| |
| if (Value *V = foldSelectICmpAnd(SI, ICI, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| // NOTE: if we wanted to, this is where to detect integer MIN/MAX |
| Value *TrueVal = SI.getTrueValue(); |
| Value *FalseVal = SI.getFalseValue(); |
| ICmpInst::Predicate Pred = ICI->getPredicate(); |
| Value *CmpLHS = ICI->getOperand(0); |
| Value *CmpRHS = ICI->getOperand(1); |
| if (CmpRHS != CmpLHS && isa<Constant>(CmpRHS)) { |
| if (CmpLHS == TrueVal && Pred == ICmpInst::ICMP_EQ) { |
| // Transform (X == C) ? X : Y -> (X == C) ? C : Y |
| SI.setOperand(1, CmpRHS); |
| Changed = true; |
| } else if (CmpLHS == FalseVal && Pred == ICmpInst::ICMP_NE) { |
| // Transform (X != C) ? Y : X -> (X != C) ? Y : C |
| SI.setOperand(2, CmpRHS); |
| Changed = true; |
| } |
| } |
| |
| // FIXME: This code is nearly duplicated in InstSimplify. Using/refactoring |
| // decomposeBitTestICmp() might help. |
| { |
| unsigned BitWidth = |
| DL.getTypeSizeInBits(TrueVal->getType()->getScalarType()); |
| APInt MinSignedValue = APInt::getSignedMinValue(BitWidth); |
| Value *X; |
| const APInt *Y, *C; |
| bool TrueWhenUnset; |
| bool IsBitTest = false; |
| if (ICmpInst::isEquality(Pred) && |
| match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) && |
| match(CmpRHS, m_Zero())) { |
| IsBitTest = true; |
| TrueWhenUnset = Pred == ICmpInst::ICMP_EQ; |
| } else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) { |
| X = CmpLHS; |
| Y = &MinSignedValue; |
| IsBitTest = true; |
| TrueWhenUnset = false; |
| } else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) { |
| X = CmpLHS; |
| Y = &MinSignedValue; |
| IsBitTest = true; |
| TrueWhenUnset = true; |
| } |
| if (IsBitTest) { |
| Value *V = nullptr; |
| // (X & Y) == 0 ? X : X ^ Y --> X & ~Y |
| if (TrueWhenUnset && TrueVal == X && |
| match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) |
| V = Builder.CreateAnd(X, ~(*Y)); |
| // (X & Y) != 0 ? X ^ Y : X --> X & ~Y |
| else if (!TrueWhenUnset && FalseVal == X && |
| match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) |
| V = Builder.CreateAnd(X, ~(*Y)); |
| // (X & Y) == 0 ? X ^ Y : X --> X | Y |
| else if (TrueWhenUnset && FalseVal == X && |
| match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) |
| V = Builder.CreateOr(X, *Y); |
| // (X & Y) != 0 ? X : X ^ Y --> X | Y |
| else if (!TrueWhenUnset && TrueVal == X && |
| match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) |
| V = Builder.CreateOr(X, *Y); |
| |
| if (V) |
| return replaceInstUsesWith(SI, V); |
| } |
| } |
| |
| if (Instruction *V = |
| foldSelectICmpAndAnd(SI.getType(), ICI, TrueVal, FalseVal, Builder)) |
| return V; |
| |
| if (Instruction *V = foldSelectCtlzToCttz(ICI, TrueVal, FalseVal, Builder)) |
| return V; |
| |
| if (Value *V = foldSelectICmpAndOr(ICI, TrueVal, FalseVal, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| if (Value *V = foldSelectICmpLshrAshr(ICI, TrueVal, FalseVal, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| if (Value *V = foldSelectCttzCtlz(ICI, TrueVal, FalseVal, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| if (Value *V = canonicalizeSaturatedSubtract(ICI, TrueVal, FalseVal, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| if (Value *V = canonicalizeSaturatedAdd(ICI, TrueVal, FalseVal, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| return Changed ? &SI : nullptr; |
| } |
| |
| /// 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 can't 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) 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; |
| } |
| |
| /// We have an SPF (e.g. a min or max) of an SPF of the form: |
| /// SPF2(SPF1(A, B), C) |
| Instruction *InstCombinerImpl::foldSPFofSPF(Instruction *Inner, |
| SelectPatternFlavor SPF1, Value *A, |
| Value *B, Instruction &Outer, |
| SelectPatternFlavor SPF2, |
| Value *C) { |
| if (Outer.getType() != Inner->getType()) |
| return nullptr; |
| |
| if (C == A || C == B) { |
| // MAX(MAX(A, B), B) -> MAX(A, B) |
| // MIN(MIN(a, b), a) -> MIN(a, b) |
| // TODO: This could be done in instsimplify. |
| if (SPF1 == SPF2 && SelectPatternResult::isMinOrMax(SPF1)) |
| return replaceInstUsesWith(Outer, Inner); |
| |
| // MAX(MIN(a, b), a) -> a |
| // MIN(MAX(a, b), a) -> a |
| // TODO: This could be done in instsimplify. |
| 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); |
| } |
| |
| if (SPF1 == SPF2) { |
| const APInt *CB, *CC; |
| if (match(B, m_APInt(CB)) && match(C, m_APInt(CC))) { |
| // MIN(MIN(A, 23), 97) -> MIN(A, 23) |
| // MAX(MAX(A, 97), 23) -> MAX(A, 97) |
| // TODO: This could be done in instsimplify. |
| if ((SPF1 == SPF_UMIN && CB->ule(*CC)) || |
| (SPF1 == SPF_SMIN && CB->sle(*CC)) || |
| (SPF1 == SPF_UMAX && CB->uge(*CC)) || |
| (SPF1 == SPF_SMAX && CB->sge(*CC))) |
| return replaceInstUsesWith(Outer, Inner); |
| |
| // MIN(MIN(A, 97), 23) -> MIN(A, 23) |
| // MAX(MAX(A, 23), 97) -> MAX(A, 97) |
| if ((SPF1 == SPF_UMIN && CB->ugt(*CC)) || |
| (SPF1 == SPF_SMIN && CB->sgt(*CC)) || |
| (SPF1 == SPF_UMAX && CB->ult(*CC)) || |
| (SPF1 == SPF_SMAX && CB->slt(*CC))) { |
| Outer.replaceUsesOfWith(Inner, A); |
| return &Outer; |
| } |
| } |
| } |
| |
| // max(max(A, B), min(A, B)) --> max(A, B) |
| // min(min(A, B), max(A, B)) --> min(A, B) |
| // TODO: This could be done in instsimplify. |
| if (SPF1 == SPF2 && |
| ((SPF1 == SPF_UMIN && match(C, m_c_UMax(m_Specific(A), m_Specific(B)))) || |
| (SPF1 == SPF_SMIN && match(C, m_c_SMax(m_Specific(A), m_Specific(B)))) || |
| (SPF1 == SPF_UMAX && match(C, m_c_UMin(m_Specific(A), m_Specific(B)))) || |
| (SPF1 == SPF_SMAX && match(C, m_c_SMin(m_Specific(A), m_Specific(B)))))) |
| return replaceInstUsesWith(Outer, Inner); |
| |
| // ABS(ABS(X)) -> ABS(X) |
| // NABS(NABS(X)) -> NABS(X) |
| // TODO: This could be done in instsimplify. |
| if (SPF1 == SPF2 && (SPF1 == SPF_ABS || SPF1 == SPF_NABS)) { |
| return replaceInstUsesWith(Outer, Inner); |
| } |
| |
| // ABS(NABS(X)) -> ABS(X) |
| // NABS(ABS(X)) -> NABS(X) |
| if ((SPF1 == SPF_ABS && SPF2 == SPF_NABS) || |
| (SPF1 == SPF_NABS && SPF2 == SPF_ABS)) { |
| SelectInst *SI = cast<SelectInst>(Inner); |
| Value *NewSI = |
| Builder.CreateSelect(SI->getCondition(), SI->getFalseValue(), |
| SI->getTrueValue(), SI->getName(), SI); |
| return replaceInstUsesWith(Outer, NewSI); |
| } |
| |
| auto IsFreeOrProfitableToInvert = |
| [&](Value *V, Value *&NotV, bool &ElidesXor) { |
| if (match(V, m_Not(m_Value(NotV)))) { |
| // If V has at most 2 uses then we can get rid of the xor operation |
| // entirely. |
| ElidesXor |= !V->hasNUsesOrMore(3); |
| return true; |
| } |
| |
| if (isFreeToInvert(V, !V->hasNUsesOrMore(3))) { |
| NotV = nullptr; |
| return true; |
| } |
| |
| return false; |
| }; |
| |
| Value *NotA, *NotB, *NotC; |
| bool ElidesXor = false; |
| |
| // MIN(MIN(~A, ~B), ~C) == ~MAX(MAX(A, B), C) |
| // MIN(MAX(~A, ~B), ~C) == ~MAX(MIN(A, B), C) |
| // MAX(MIN(~A, ~B), ~C) == ~MIN(MAX(A, B), C) |
| // MAX(MAX(~A, ~B), ~C) == ~MIN(MIN(A, B), C) |
| // |
| // This transform is performance neutral if we can elide at least one xor from |
| // the set of three operands, since we'll be tacking on an xor at the very |
| // end. |
| if (SelectPatternResult::isMinOrMax(SPF1) && |
| SelectPatternResult::isMinOrMax(SPF2) && |
| IsFreeOrProfitableToInvert(A, NotA, ElidesXor) && |
| IsFreeOrProfitableToInvert(B, NotB, ElidesXor) && |
| IsFreeOrProfitableToInvert(C, NotC, ElidesXor) && ElidesXor) { |
| if (!NotA) |
| NotA = Builder.CreateNot(A); |
| if (!NotB) |
| NotB = Builder.CreateNot(B); |
| if (!NotC) |
| NotC = Builder.CreateNot(C); |
| |
| Value *NewInner = createMinMax(Builder, getInverseMinMaxFlavor(SPF1), NotA, |
| NotB); |
| Value *NewOuter = Builder.CreateNot( |
| createMinMax(Builder, getInverseMinMaxFlavor(SPF2), NewInner, NotC)); |
| return replaceInstUsesWith(Outer, NewOuter); |
| } |
| |
| return nullptr; |
| } |
| |
| /// Turn select C, (X + Y), (X - Y) --> (X + (select C, Y, (-Y))). |
| /// This is even legal for FP. |
| static Instruction *foldAddSubSelect(SelectInst &SI, |
| InstCombiner::BuilderTy &Builder) { |
| Value *CondVal = SI.getCondition(); |
| Value *TrueVal = SI.getTrueValue(); |
| Value *FalseVal = SI.getFalseValue(); |
| auto *TI = dyn_cast<Instruction>(TrueVal); |
| auto *FI = dyn_cast<Instruction>(FalseVal); |
| if (!TI || !FI || !TI->hasOneUse() || !FI->hasOneUse()) |
| return nullptr; |
| |
| Instruction *AddOp = nullptr, *SubOp = nullptr; |
| 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 = nullptr; |
| 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 (SI.getType()->isFPOrFPVectorTy()) { |
| NegVal = Builder.CreateFNeg(SubOp->getOperand(1)); |
| if (Instruction *NegInst = dyn_cast<Instruction>(NegVal)) { |
| FastMathFlags Flags = AddOp->getFastMathFlags(); |
| Flags &= SubOp->getFastMathFlags(); |
| NegInst->setFastMathFlags(Flags); |
| } |
| } else { |
| NegVal = Builder.CreateNeg(SubOp->getOperand(1)); |
| } |
| |
| Value *NewTrueOp = OtherAddOp; |
| Value *NewFalseOp = NegVal; |
| if (AddOp != TI) |
| std::swap(NewTrueOp, NewFalseOp); |
| Value *NewSel = Builder.CreateSelect(CondVal, NewTrueOp, NewFalseOp, |
| SI.getName() + ".p", &SI); |
| |
| if (SI.getType()->isFPOrFPVectorTy()) { |
| Instruction *RI = |
| BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel); |
| |
| FastMathFlags Flags = AddOp->getFastMathFlags(); |
| Flags &= SubOp->getFastMathFlags(); |
| RI->setFastMathFlags(Flags); |
| return RI; |
| } else |
| return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel); |
| } |
| } |
| return nullptr; |
| } |
| |
| /// Turn X + Y overflows ? -1 : X + Y -> uadd_sat X, Y |
| /// And X - Y overflows ? 0 : X - Y -> usub_sat X, Y |
| /// Along with a number of patterns similar to: |
| /// X + Y overflows ? (X < 0 ? INTMIN : INTMAX) : X + Y --> sadd_sat X, Y |
| /// X - Y overflows ? (X > 0 ? INTMAX : INTMIN) : X - Y --> ssub_sat X, Y |
| static Instruction * |
| foldOverflowingAddSubSelect(SelectInst &SI, InstCombiner::BuilderTy &Builder) { |
| Value *CondVal = SI.getCondition(); |
| Value *TrueVal = SI.getTrueValue(); |
| Value *FalseVal = SI.getFalseValue(); |
| |
| WithOverflowInst *II; |
| if (!match(CondVal, m_ExtractValue<1>(m_WithOverflowInst(II))) || |
| !match(FalseVal, m_ExtractValue<0>(m_Specific(II)))) |
| return nullptr; |
| |
| Value *X = II->getLHS(); |
| Value *Y = II->getRHS(); |
| |
| auto IsSignedSaturateLimit = [&](Value *Limit, bool IsAdd) { |
| Type *Ty = Limit->getType(); |
| |
| ICmpInst::Predicate Pred; |
| Value *TrueVal, *FalseVal, *Op; |
| const APInt *C; |
| if (!match(Limit, m_Select(m_ICmp(Pred, m_Value(Op), m_APInt(C)), |
| m_Value(TrueVal), m_Value(FalseVal)))) |
| return false; |
| |
| auto IsZeroOrOne = [](const APInt &C) { return C.isZero() || C.isOne(); }; |
| auto IsMinMax = [&](Value *Min, Value *Max) { |
| APInt MinVal = APInt::getSignedMinValue(Ty->getScalarSizeInBits()); |
| APInt MaxVal = APInt::getSignedMaxValue(Ty->getScalarSizeInBits()); |
| return match(Min, m_SpecificInt(MinVal)) && |
| match(Max, m_SpecificInt(MaxVal)); |
| }; |
| |
| if (Op != X && Op != Y) |
| return false; |
| |
| if (IsAdd) { |
| // X + Y overflows ? (X <s 0 ? INTMIN : INTMAX) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (X <s 1 ? INTMIN : INTMAX) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (Y <s 0 ? INTMIN : INTMAX) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (Y <s 1 ? INTMIN : INTMAX) : X + Y --> sadd_sat X, Y |
| if (Pred == ICmpInst::ICMP_SLT && IsZeroOrOne(*C) && |
| IsMinMax(TrueVal, FalseVal)) |
| return true; |
| // X + Y overflows ? (X >s 0 ? INTMAX : INTMIN) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (X >s -1 ? INTMAX : INTMIN) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (Y >s 0 ? INTMAX : INTMIN) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (Y >s -1 ? INTMAX : INTMIN) : X + Y --> sadd_sat X, Y |
| if (Pred == ICmpInst::ICMP_SGT && IsZeroOrOne(*C + 1) && |
| IsMinMax(FalseVal, TrueVal)) |
| return true; |
| } else { |
| // X - Y overflows ? (X <s 0 ? INTMIN : INTMAX) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (X <s -1 ? INTMIN : INTMAX) : X - Y --> ssub_sat X, Y |
| if (Op == X && Pred == ICmpInst::ICMP_SLT && IsZeroOrOne(*C + 1) && |
| IsMinMax(TrueVal, FalseVal)) |
| return true; |
| // X - Y overflows ? (X >s -1 ? INTMAX : INTMIN) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (X >s -2 ? INTMAX : INTMIN) : X - Y --> ssub_sat X, Y |
| if (Op == X && Pred == ICmpInst::ICMP_SGT && IsZeroOrOne(*C + 2) && |
| IsMinMax(FalseVal, TrueVal)) |
| return true; |
| // X - Y overflows ? (Y <s 0 ? INTMAX : INTMIN) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (Y <s 1 ? INTMAX : INTMIN) : X - Y --> ssub_sat X, Y |
| if (Op == Y && Pred == ICmpInst::ICMP_SLT && IsZeroOrOne(*C) && |
| IsMinMax(FalseVal, TrueVal)) |
| return true; |
| // X - Y overflows ? (Y >s 0 ? INTMIN : INTMAX) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (Y >s -1 ? INTMIN : INTMAX) : X - Y --> ssub_sat X, Y |
| if (Op == Y && Pred == ICmpInst::ICMP_SGT && IsZeroOrOne(*C + 1) && |
| IsMinMax(TrueVal, FalseVal)) |
| return true; |
| } |
| |
| return false; |
| }; |
| |
| Intrinsic::ID NewIntrinsicID; |
| if (II->getIntrinsicID() == Intrinsic::uadd_with_overflow && |
| match(TrueVal, m_AllOnes())) |
| // X + Y overflows ? -1 : X + Y -> uadd_sat X, Y |
| NewIntrinsicID = Intrinsic::uadd_sat; |
| else if (II->getIntrinsicID() == Intrinsic::usub_with_overflow && |
| match(TrueVal, m_Zero())) |
| // X - Y overflows ? 0 : X - Y -> usub_sat X, Y |
| NewIntrinsicID = Intrinsic::usub_sat; |
| else if (II->getIntrinsicID() == Intrinsic::sadd_with_overflow && |
| IsSignedSaturateLimit(TrueVal, /*IsAdd=*/true)) |
| // X + Y overflows ? (X <s 0 ? INTMIN : INTMAX) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (X <s 1 ? INTMIN : INTMAX) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (X >s 0 ? INTMAX : INTMIN) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (X >s -1 ? INTMAX : INTMIN) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (Y <s 0 ? INTMIN : INTMAX) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (Y <s 1 ? INTMIN : INTMAX) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (Y >s 0 ? INTMAX : INTMIN) : X + Y --> sadd_sat X, Y |
| // X + Y overflows ? (Y >s -1 ? INTMAX : INTMIN) : X + Y --> sadd_sat X, Y |
| NewIntrinsicID = Intrinsic::sadd_sat; |
| else if (II->getIntrinsicID() == Intrinsic::ssub_with_overflow && |
| IsSignedSaturateLimit(TrueVal, /*IsAdd=*/false)) |
| // X - Y overflows ? (X <s 0 ? INTMIN : INTMAX) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (X <s -1 ? INTMIN : INTMAX) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (X >s -1 ? INTMAX : INTMIN) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (X >s -2 ? INTMAX : INTMIN) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (Y <s 0 ? INTMAX : INTMIN) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (Y <s 1 ? INTMAX : INTMIN) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (Y >s 0 ? INTMIN : INTMAX) : X - Y --> ssub_sat X, Y |
| // X - Y overflows ? (Y >s -1 ? INTMIN : INTMAX) : X - Y --> ssub_sat X, Y |
| NewIntrinsicID = Intrinsic::ssub_sat; |
| else |
| return nullptr; |
| |
| Function *F = |
| Intrinsic::getDeclaration(SI.getModule(), NewIntrinsicID, SI.getType()); |
| return CallInst::Create(F, {X, Y}); |
| } |
| |
| Instruction *InstCombinerImpl::foldSelectExtConst(SelectInst &Sel) { |
| Constant *C; |
| if (!match(Sel.getTrueValue(), m_Constant(C)) && |
| !match(Sel.getFalseValue(), m_Constant(C))) |
| return nullptr; |
| |
| Instruction *ExtInst; |
| if (!match(Sel.getTrueValue(), m_Instruction(ExtInst)) && |
| !match(Sel.getFalseValue(), m_Instruction(ExtInst))) |
| return nullptr; |
| |
| auto ExtOpcode = ExtInst->getOpcode(); |
| if (ExtOpcode != Instruction::ZExt && ExtOpcode != Instruction::SExt) |
| return nullptr; |
| |
| // If we are extending from a boolean type or if we can create a select that |
| // has the same size operands as its condition, try to narrow the select. |
| Value *X = ExtInst->getOperand(0); |
| Type *SmallType = X->getType(); |
| Value *Cond = Sel.getCondition(); |
| auto *Cmp = dyn_cast<CmpInst>(Cond); |
| if (!SmallType->isIntOrIntVectorTy(1) && |
| (!Cmp || Cmp->getOperand(0)->getType() != SmallType)) |
| return nullptr; |
| |
| // If the constant is the same after truncation to the smaller type and |
| // extension to the original type, we can narrow the select. |
| Type *SelType = Sel.getType(); |
| Constant *TruncC = ConstantExpr::getTrunc(C, SmallType); |
| Constant *ExtC = ConstantExpr::getCast(ExtOpcode, TruncC, SelType); |
| if (ExtC == C && ExtInst->hasOneUse()) { |
| Value *TruncCVal = cast<Value>(TruncC); |
| if (ExtInst == Sel.getFalseValue()) |
| std::swap(X, TruncCVal); |
| |
| // select Cond, (ext X), C --> ext(select Cond, X, C') |
| // select Cond, C, (ext X) --> ext(select Cond, C', X) |
| Value *NewSel = Builder.CreateSelect(Cond, X, TruncCVal, "narrow", &Sel); |
| return CastInst::Create(Instruction::CastOps(ExtOpcode), NewSel, SelType); |
| } |
| |
| // If one arm of the select is the extend of the condition, replace that arm |
| // with the extension of the appropriate known bool value. |
| if (Cond == X) { |
| if (ExtInst == Sel.getTrueValue()) { |
| // select X, (sext X), C --> select X, -1, C |
| // select X, (zext X), C --> select X, 1, C |
| Constant *One = ConstantInt::getTrue(SmallType); |
| Constant *AllOnesOrOne = ConstantExpr::getCast(ExtOpcode, One, SelType); |
| return SelectInst::Create(Cond, AllOnesOrOne, C, "", nullptr, &Sel); |
| } else { |
| // select X, C, (sext X) --> select X, C, 0 |
| // select X, C, (zext X) --> select X, C, 0 |
| Constant *Zero = ConstantInt::getNullValue(SelType); |
| return SelectInst::Create(Cond, C, Zero, "", nullptr, &Sel); |
| } |
| } |
| |
| return nullptr; |
| } |
| |
| /// Try to transform a vector select with a constant condition vector into a |
| /// shuffle for easier combining with other shuffles and insert/extract. |
| static Instruction *canonicalizeSelectToShuffle(SelectInst &SI) { |
| Value *CondVal = SI.getCondition(); |
| Constant *CondC; |
| auto *CondValTy = dyn_cast<FixedVectorType>(CondVal->getType()); |
| if (!CondValTy || !match(CondVal, m_Constant(CondC))) |
| return nullptr; |
| |
| unsigned NumElts = CondValTy->getNumElements(); |
| SmallVector<int, 16> Mask; |
| Mask.reserve(NumElts); |
| for (unsigned i = 0; i != NumElts; ++i) { |
| Constant *Elt = CondC->getAggregateElement(i); |
| if (!Elt) |
| return nullptr; |
| |
| if (Elt->isOneValue()) { |
| // If the select condition element is true, choose from the 1st vector. |
| Mask.push_back(i); |
| } else if (Elt->isNullValue()) { |
| // If the select condition element is false, choose from the 2nd vector. |
| Mask.push_back(i + NumElts); |
| } else if (isa<UndefValue>(Elt)) { |
| // Undef in a select condition (choose one of the operands) does not mean |
| // the same thing as undef in a shuffle mask (any value is acceptable), so |
| // give up. |
| return nullptr; |
| } else { |
| // Bail out on a constant expression. |
| return nullptr; |
| } |
| } |
| |
| return new ShuffleVectorInst(SI.getTrueValue(), SI.getFalseValue(), Mask); |
| } |
| |
| /// If we have a select of vectors with a scalar condition, try to convert that |
| /// to a vector select by splatting the condition. A splat may get folded with |
| /// other operations in IR and having all operands of a select be vector types |
| /// is likely better for vector codegen. |
| static Instruction *canonicalizeScalarSelectOfVecs(SelectInst &Sel, |
| InstCombinerImpl &IC) { |
| auto *Ty = dyn_cast<VectorType>(Sel.getType()); |
| if (!Ty) |
| return nullptr; |
| |
| // We can replace a single-use extract with constant index. |
| Value *Cond = Sel.getCondition(); |
| if (!match(Cond, m_OneUse(m_ExtractElt(m_Value(), m_ConstantInt())))) |
| return nullptr; |
| |
| // select (extelt V, Index), T, F --> select (splat V, Index), T, F |
| // Splatting the extracted condition reduces code (we could directly create a |
| // splat shuffle of the source vector to eliminate the intermediate step). |
| return IC.replaceOperand( |
| Sel, 0, IC.Builder.CreateVectorSplat(Ty->getElementCount(), Cond)); |
| } |
| |
| /// Reuse bitcasted operands between a compare and select: |
| /// select (cmp (bitcast C), (bitcast D)), (bitcast' C), (bitcast' D) --> |
| /// bitcast (select (cmp (bitcast C), (bitcast D)), (bitcast C), (bitcast D)) |
| static Instruction *foldSelectCmpBitcasts(SelectInst &Sel, |
| InstCombiner::BuilderTy &Builder) { |
| Value *Cond = Sel.getCondition(); |
| Value *TVal = Sel.getTrueValue(); |
| Value *FVal = Sel.getFalseValue(); |
| |
| CmpInst::Predicate Pred; |
| Value *A, *B; |
| if (!match(Cond, m_Cmp(Pred, m_Value(A), m_Value(B)))) |
| return nullptr; |
| |
| // The select condition is a compare instruction. If the select's true/false |
| // values are already the same as the compare operands, there's nothing to do. |
| if (TVal == A || TVal == B || FVal == A || FVal == B) |
| return nullptr; |
| |
| Value *C, *D; |
| if (!match(A, m_BitCast(m_Value(C))) || !match(B, m_BitCast(m_Value(D)))) |
| return nullptr; |
| |
| // select (cmp (bitcast C), (bitcast D)), (bitcast TSrc), (bitcast FSrc) |
| Value *TSrc, *FSrc; |
| if (!match(TVal, m_BitCast(m_Value(TSrc))) || |
| !match(FVal, m_BitCast(m_Value(FSrc)))) |
| return nullptr; |
| |
| // If the select true/false values are *different bitcasts* of the same source |
| // operands, make the select operands the same as the compare operands and |
| // cast the result. This is the canonical select form for min/max. |
| Value *NewSel; |
| if (TSrc == C && FSrc == D) { |
| // select (cmp (bitcast C), (bitcast D)), (bitcast' C), (bitcast' D) --> |
| // bitcast (select (cmp A, B), A, B) |
| NewSel = Builder.CreateSelect(Cond, A, B, "", &Sel); |
| } else if (TSrc == D && FSrc == C) { |
| // select (cmp (bitcast C), (bitcast D)), (bitcast' D), (bitcast' C) --> |
| // bitcast (select (cmp A, B), B, A) |
| NewSel = Builder.CreateSelect(Cond, B, A, "", &Sel); |
| } else { |
| return nullptr; |
| } |
| return CastInst::CreateBitOrPointerCast(NewSel, Sel.getType()); |
| } |
| |
| /// Try to eliminate select instructions that test the returned flag of cmpxchg |
| /// instructions. |
| /// |
| /// If a select instruction tests the returned flag of a cmpxchg instruction and |
| /// selects between the returned value of the cmpxchg instruction its compare |
| /// operand, the result of the select will always be equal to its false value. |
| /// For example: |
| /// |
| /// %0 = cmpxchg i64* %ptr, i64 %compare, i64 %new_value seq_cst seq_cst |
| /// %1 = extractvalue { i64, i1 } %0, 1 |
| /// %2 = extractvalue { i64, i1 } %0, 0 |
| /// %3 = select i1 %1, i64 %compare, i64 %2 |
| /// ret i64 %3 |
| /// |
| /// The returned value of the cmpxchg instruction (%2) is the original value |
| /// located at %ptr prior to any update. If the cmpxchg operation succeeds, %2 |
| /// must have been equal to %compare. Thus, the result of the select is always |
| /// equal to %2, and the code can be simplified to: |
| /// |
| /// %0 = cmpxchg i64* %ptr, i64 %compare, i64 %new_value seq_cst seq_cst |
| /// %1 = extractvalue { i64, i1 } %0, 0 |
| /// ret i64 %1 |
| /// |
| static Value *foldSelectCmpXchg(SelectInst &SI) { |
| // A helper that determines if V is an extractvalue instruction whose |
| // aggregate operand is a cmpxchg instruction and whose single index is equal |
| // to I. If such conditions are true, the helper returns the cmpxchg |
| // instruction; otherwise, a nullptr is returned. |
| auto isExtractFromCmpXchg = [](Value *V, unsigned I) -> AtomicCmpXchgInst * { |
| auto *Extract = dyn_cast<ExtractValueInst>(V); |
| if (!Extract) |
| return nullptr; |
| if (Extract->getIndices()[0] != I) |
| return nullptr; |
| return dyn_cast<AtomicCmpXchgInst>(Extract->getAggregateOperand()); |
| }; |
| |
| // If the select has a single user, and this user is a select instruction that |
| // we can simplify, skip the cmpxchg simplification for now. |
| if (SI.hasOneUse()) |
| if (auto *Select = dyn_cast<SelectInst>(SI.user_back())) |
| if (Select->getCondition() == SI.getCondition()) |
| if (Select->getFalseValue() == SI.getTrueValue() || |
| Select->getTrueValue() == SI.getFalseValue()) |
| return nullptr; |
| |
| // Ensure the select condition is the returned flag of a cmpxchg instruction. |
| auto *CmpXchg = isExtractFromCmpXchg(SI.getCondition(), 1); |
| if (!CmpXchg) |
| return nullptr; |
| |
| // Check the true value case: The true value of the select is the returned |
| // value of the same cmpxchg used by the condition, and the false value is the |
| // cmpxchg instruction's compare operand. |
| if (auto *X = isExtractFromCmpXchg(SI.getTrueValue(), 0)) |
| if (X == CmpXchg && X->getCompareOperand() == SI.getFalseValue()) |
| return SI.getFalseValue(); |
| |
| // Check the false value case: The false value of the select is the returned |
| // value of the same cmpxchg used by the condition, and the true value is the |
| // cmpxchg instruction's compare operand. |
| if (auto *X = isExtractFromCmpXchg(SI.getFalseValue(), 0)) |
| if (X == CmpXchg && X->getCompareOperand() == SI.getTrueValue()) |
| return SI.getFalseValue(); |
| |
| return nullptr; |
| } |
| |
| static Instruction *moveAddAfterMinMax(SelectPatternFlavor SPF, Value *X, |
| Value *Y, |
| InstCombiner::BuilderTy &Builder) { |
| assert(SelectPatternResult::isMinOrMax(SPF) && "Expected min/max pattern"); |
| bool IsUnsigned = SPF == SelectPatternFlavor::SPF_UMIN || |
| SPF == SelectPatternFlavor::SPF_UMAX; |
| // TODO: If InstSimplify could fold all cases where C2 <= C1, we could change |
| // the constant value check to an assert. |
| Value *A; |
| const APInt *C1, *C2; |
| if (IsUnsigned && match(X, m_NUWAdd(m_Value(A), m_APInt(C1))) && |
| match(Y, m_APInt(C2)) && C2->uge(*C1) && X->hasNUses(2)) { |
| // umin (add nuw A, C1), C2 --> add nuw (umin A, C2 - C1), C1 |
| // umax (add nuw A, C1), C2 --> add nuw (umax A, C2 - C1), C1 |
| Value *NewMinMax = createMinMax(Builder, SPF, A, |
| ConstantInt::get(X->getType(), *C2 - *C1)); |
| return BinaryOperator::CreateNUW(BinaryOperator::Add, NewMinMax, |
| ConstantInt::get(X->getType(), *C1)); |
| } |
| |
| if (!IsUnsigned && match(X, m_NSWAdd(m_Value(A), m_APInt(C1))) && |
| match(Y, m_APInt(C2)) && X->hasNUses(2)) { |
| bool Overflow; |
| APInt Diff = C2->ssub_ov(*C1, Overflow); |
| if (!Overflow) { |
| // smin (add nsw A, C1), C2 --> add nsw (smin A, C2 - C1), C1 |
| // smax (add nsw A, C1), C2 --> add nsw (smax A, C2 - C1), C1 |
| Value *NewMinMax = createMinMax(Builder, SPF, A, |
| ConstantInt::get(X->getType(), Diff)); |
| return BinaryOperator::CreateNSW(BinaryOperator::Add, NewMinMax, |
| ConstantInt::get(X->getType(), *C1)); |
| } |
| } |
| |
| return nullptr; |
| } |
| |
| /// Match a sadd_sat or ssub_sat which is using min/max to clamp the value. |
| Instruction *InstCombinerImpl::matchSAddSubSat(Instruction &MinMax1) { |
| Type *Ty = MinMax1.getType(); |
| |
| // We are looking for a tree of: |
| // max(INT_MIN, min(INT_MAX, add(sext(A), sext(B)))) |
| // Where the min and max could be reversed |
| Instruction *MinMax2; |
| BinaryOperator *AddSub; |
| const APInt *MinValue, *MaxValue; |
| if (match(&MinMax1, m_SMin(m_Instruction(MinMax2), m_APInt(MaxValue)))) { |
| if (!match(MinMax2, m_SMax(m_BinOp(AddSub), m_APInt(MinValue)))) |
| return nullptr; |
| } else if (match(&MinMax1, |
| m_SMax(m_Instruction(MinMax2), m_APInt(MinValue)))) { |
| if (!match(MinMax2, m_SMin(m_BinOp(AddSub), m_APInt(MaxValue)))) |
| return nullptr; |
| } else |
| return nullptr; |
| |
| // Check that the constants clamp a saturate, and that the new type would be |
| // sensible to convert to. |
| if (!(*MaxValue + 1).isPowerOf2() || -*MinValue != *MaxValue + 1) |
| return nullptr; |
| // In what bitwidth can this be treated as saturating arithmetics? |
| unsigned NewBitWidth = (*MaxValue + 1).logBase2() + 1; |
| // FIXME: This isn't quite right for vectors, but using the scalar type is a |
| // good first approximation for what should be done there. |
| if (!shouldChangeType(Ty->getScalarType()->getIntegerBitWidth(), NewBitWidth)) |
| return nullptr; |
| |
| // Also make sure that the number of uses is as expected. The 3 is for the |
| // the two items of the compare and the select, or 2 from a min/max. |
| unsigned ExpUses = isa<IntrinsicInst>(MinMax1) ? 2 : 3; |
| if (MinMax2->hasNUsesOrMore(ExpUses) || AddSub->hasNUsesOrMore(ExpUses)) |
| return nullptr; |
| |
| // Create the new type (which can be a vector type) |
| Type *NewTy = Ty->getWithNewBitWidth(NewBitWidth); |
| |
| Intrinsic::ID IntrinsicID; |
| if (AddSub->getOpcode() == Instruction::Add) |
| IntrinsicID = Intrinsic::sadd_sat; |
| else if (AddSub->getOpcode() == Instruction::Sub) |
| IntrinsicID = Intrinsic::ssub_sat; |
| else |
| return nullptr; |
| |
| // The two operands of the add/sub must be nsw-truncatable to the NewTy. This |
| // is usually achieved via a sext from a smaller type. |
| if (ComputeMinSignedBits(AddSub->getOperand(0), 0, AddSub) > NewBitWidth || |
| ComputeMinSignedBits(AddSub->getOperand(1), 0, AddSub) > NewBitWidth) |
| return nullptr; |
| |
| // Finally create and return the sat intrinsic, truncated to the new type |
| Function *F = Intrinsic::getDeclaration(MinMax1.getModule(), IntrinsicID, NewTy); |
| Value *AT = Builder.CreateTrunc(AddSub->getOperand(0), NewTy); |
| Value *BT = Builder.CreateTrunc(AddSub->getOperand(1), NewTy); |
| Value *Sat = Builder.CreateCall(F, {AT, BT}); |
| return CastInst::Create(Instruction::SExt, Sat, Ty); |
| } |
| |
| /// Reduce a sequence of min/max with a common operand. |
| static Instruction *factorizeMinMaxTree(SelectPatternFlavor SPF, Value *LHS, |
| Value *RHS, |
| InstCombiner::BuilderTy &Builder) { |
| assert(SelectPatternResult::isMinOrMax(SPF) && "Expected a min/max"); |
| // TODO: Allow FP min/max with nnan/nsz. |
| if (!LHS->getType()->isIntOrIntVectorTy()) |
| return nullptr; |
| |
| // Match 3 of the same min/max ops. Example: umin(umin(), umin()). |
| Value *A, *B, *C, *D; |
| SelectPatternResult L = matchSelectPattern(LHS, A, B); |
| SelectPatternResult R = matchSelectPattern(RHS, C, D); |
| if (SPF != L.Flavor || L.Flavor != R.Flavor) |
| return nullptr; |
| |
| // Look for a common operand. The use checks are different than usual because |
| // a min/max pattern typically has 2 uses of each op: 1 by the cmp and 1 by |
| // the select. |
| Value *MinMaxOp = nullptr; |
| Value *ThirdOp = nullptr; |
| if (!LHS->hasNUsesOrMore(3) && RHS->hasNUsesOrMore(3)) { |
| // If the LHS is only used in this chain and the RHS is used outside of it, |
| // reuse the RHS min/max because that will eliminate the LHS. |
| if (D == A || C == A) { |
| // min(min(a, b), min(c, a)) --> min(min(c, a), b) |
| // min(min(a, b), min(a, d)) --> min(min(a, d), b) |
| MinMaxOp = RHS; |
| ThirdOp = B; |
| } else if (D == B || C == B) { |
| // min(min(a, b), min(c, b)) --> min(min(c, b), a) |
| // min(min(a, b), min(b, d)) --> min(min(b, d), a) |
| MinMaxOp = RHS; |
| ThirdOp = A; |
| } |
| } else if (!RHS->hasNUsesOrMore(3)) { |
| // Reuse the LHS. This will eliminate the RHS. |
| if (D == A || D == B) { |
| // min(min(a, b), min(c, a)) --> min(min(a, b), c) |
| // min(min(a, b), min(c, b)) --> min(min(a, b), c) |
| MinMaxOp = LHS; |
| ThirdOp = C; |
| } else if (C == A || C == B) { |
| // min(min(a, b), min(b, d)) --> min(min(a, b), d) |
| // min(min(a, b), min(c, b)) --> min(min(a, b), d) |
| MinMaxOp = LHS; |
| ThirdOp = D; |
| } |
| } |
| if (!MinMaxOp || !ThirdOp) |
| return nullptr; |
| |
| CmpInst::Predicate P = getMinMaxPred(SPF); |
| Value *CmpABC = Builder.CreateICmp(P, MinMaxOp, ThirdOp); |
| return SelectInst::Create(CmpABC, MinMaxOp, ThirdOp); |
| } |
| |
| /// Try to reduce a funnel/rotate pattern that includes a compare and select |
| /// into a funnel shift intrinsic. Example: |
| /// rotl32(a, b) --> (b == 0 ? a : ((a >> (32 - b)) | (a << b))) |
| /// --> call llvm.fshl.i32(a, a, b) |
| /// fshl32(a, b, c) --> (c == 0 ? a : ((b >> (32 - c)) | (a << c))) |
| /// --> call llvm.fshl.i32(a, b, c) |
| /// fshr32(a, b, c) --> (c == 0 ? b : ((a >> (32 - c)) | (b << c))) |
| /// --> call llvm.fshr.i32(a, b, c) |
| static Instruction *foldSelectFunnelShift(SelectInst &Sel, |
| InstCombiner::BuilderTy &Builder) { |
| // This must be a power-of-2 type for a bitmasking transform to be valid. |
| unsigned Width = Sel.getType()->getScalarSizeInBits(); |
| if (!isPowerOf2_32(Width)) |
| return nullptr; |
| |
| BinaryOperator *Or0, *Or1; |
| if (!match(Sel.getFalseValue(), m_OneUse(m_Or(m_BinOp(Or0), m_BinOp(Or1))))) |
| return nullptr; |
| |
| Value *SV0, *SV1, *SA0, *SA1; |
| if (!match(Or0, m_OneUse(m_LogicalShift(m_Value(SV0), |
| m_ZExtOrSelf(m_Value(SA0))))) || |
| !match(Or1, m_OneUse(m_LogicalShift(m_Value(SV1), |
| m_ZExtOrSelf(m_Value(SA1))))) || |
| Or0->getOpcode() == Or1->getOpcode()) |
| return nullptr; |
| |
| // Canonicalize to or(shl(SV0, SA0), lshr(SV1, SA1)). |
| if (Or0->getOpcode() == BinaryOperator::LShr) { |
| std::swap(Or0, Or1); |
| std::swap(SV0, SV1); |
| std::swap(SA0, SA1); |
| } |
| assert(Or0->getOpcode() == BinaryOperator::Shl && |
| Or1->getOpcode() == BinaryOperator::LShr && |
| "Illegal or(shift,shift) pair"); |
| |
| // Check the shift amounts to see if they are an opposite pair. |
| Value *ShAmt; |
| if (match(SA1, m_OneUse(m_Sub(m_SpecificInt(Width), m_Specific(SA0))))) |
| ShAmt = SA0; |
| else if (match(SA0, m_OneUse(m_Sub(m_SpecificInt(Width), m_Specific(SA1))))) |
| ShAmt = SA1; |
| else |
| return nullptr; |
| |
| // We should now have this pattern: |
| // select ?, TVal, (or (shl SV0, SA0), (lshr SV1, SA1)) |
| // The false value of the select must be a funnel-shift of the true value: |
| // IsFShl -> TVal must be SV0 else TVal must be SV1. |
| bool IsFshl = (ShAmt == SA0); |
| Value *TVal = Sel.getTrueValue(); |
| if ((IsFshl && TVal != SV0) || (!IsFshl && TVal != SV1)) |
| return nullptr; |
| |
| // Finally, see if the select is filtering out a shift-by-zero. |
| Value *Cond = Sel.getCondition(); |
| ICmpInst::Predicate Pred; |
| if (!match(Cond, m_OneUse(m_ICmp(Pred, m_Specific(ShAmt), m_ZeroInt()))) || |
| Pred != ICmpInst::ICMP_EQ) |
| return nullptr; |
| |
| // If this is not a rotate then the select was blocking poison from the |
| // 'shift-by-zero' non-TVal, but a funnel shift won't - so freeze it. |
| if (SV0 != SV1) { |
| if (IsFshl && !llvm::isGuaranteedNotToBePoison(SV1)) |
| SV1 = Builder.CreateFreeze(SV1); |
| else if (!IsFshl && !llvm::isGuaranteedNotToBePoison(SV0)) |
| SV0 = Builder.CreateFreeze(SV0); |
| } |
| |
| // This is a funnel/rotate that avoids shift-by-bitwidth UB in a suboptimal way. |
| // Convert to funnel shift intrinsic. |
| Intrinsic::ID IID = IsFshl ? Intrinsic::fshl : Intrinsic::fshr; |
| Function *F = Intrinsic::getDeclaration(Sel.getModule(), IID, Sel.getType()); |
| ShAmt = Builder.CreateZExt(ShAmt, Sel.getType()); |
| return CallInst::Create(F, { SV0, SV1, ShAmt }); |
| } |
| |
| static Instruction *foldSelectToCopysign(SelectInst &Sel, |
| InstCombiner::BuilderTy &Builder) { |
| Value *Cond = Sel.getCondition(); |
| Value *TVal = Sel.getTrueValue(); |
| Value *FVal = Sel.getFalseValue(); |
| Type *SelType = Sel.getType(); |
| |
| // Match select ?, TC, FC where the constants are equal but negated. |
| // TODO: Generalize to handle a negated variable operand? |
| const APFloat *TC, *FC; |
| if (!match(TVal, m_APFloat(TC)) || !match(FVal, m_APFloat(FC)) || |
| !abs(*TC).bitwiseIsEqual(abs(*FC))) |
| return nullptr; |
| |
| assert(TC != FC && "Expected equal select arms to simplify"); |
| |
| Value *X; |
| const APInt *C; |
| bool IsTrueIfSignSet; |
| ICmpInst::Predicate Pred; |
| if (!match(Cond, m_OneUse(m_ICmp(Pred, m_BitCast(m_Value(X)), m_APInt(C)))) || |
| !InstCombiner::isSignBitCheck(Pred, *C, IsTrueIfSignSet) || |
| X->getType() != SelType) |
| return nullptr; |
| |
| // If needed, negate the value that will be the sign argument of the copysign: |
| // (bitcast X) < 0 ? -TC : TC --> copysign(TC, X) |
| // (bitcast X) < 0 ? TC : -TC --> copysign(TC, -X) |
| // (bitcast X) >= 0 ? -TC : TC --> copysign(TC, -X) |
| // (bitcast X) >= 0 ? TC : -TC --> copysign(TC, X) |
| if (IsTrueIfSignSet ^ TC->isNegative()) |
| X = Builder.CreateFNegFMF(X, &Sel); |
| |
| // Canonicalize the magnitude argument as the positive constant since we do |
| // not care about its sign. |
| Value *MagArg = TC->isNegative() ? FVal : TVal; |
| Function *F = Intrinsic::getDeclaration(Sel.getModule(), Intrinsic::copysign, |
| Sel.getType()); |
| Instruction *CopySign = CallInst::Create(F, { MagArg, X }); |
| CopySign->setFastMathFlags(Sel.getFastMathFlags()); |
| return CopySign; |
| } |
| |
| Instruction *InstCombinerImpl::foldVectorSelect(SelectInst &Sel) { |
| auto *VecTy = dyn_cast<FixedVectorType>(Sel.getType()); |
| if (!VecTy) |
| return nullptr; |
| |
| unsigned NumElts = VecTy->getNumElements(); |
| APInt UndefElts(NumElts, 0); |
| APInt AllOnesEltMask(APInt::getAllOnes(NumElts)); |
| if (Value *V = SimplifyDemandedVectorElts(&Sel, AllOnesEltMask, UndefElts)) { |
| if (V != &Sel) |
| return replaceInstUsesWith(Sel, V); |
| return &Sel; |
| } |
| |
| // A select of a "select shuffle" with a common operand can be rearranged |
| // to select followed by "select shuffle". Because of poison, this only works |
| // in the case of a shuffle with no undefined mask elements. |
| Value *Cond = Sel.getCondition(); |
| Value *TVal = Sel.getTrueValue(); |
| Value *FVal = Sel.getFalseValue(); |
| Value *X, *Y; |
| ArrayRef<int> Mask; |
| if (match(TVal, m_OneUse(m_Shuffle(m_Value(X), m_Value(Y), m_Mask(Mask)))) && |
| !is_contained(Mask, UndefMaskElem) && |
| cast<ShuffleVectorInst>(TVal)->isSelect()) { |
| if (X == FVal) { |
| // select Cond, (shuf_sel X, Y), X --> shuf_sel X, (select Cond, Y, X) |
| Value *NewSel = Builder.CreateSelect(Cond, Y, X, "sel", &Sel); |
| return new ShuffleVectorInst(X, NewSel, Mask); |
| } |
| if (Y == FVal) { |
| |