diff options
Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineShifts.cpp')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineShifts.cpp | 703 |
1 files changed, 301 insertions, 402 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineShifts.cpp b/lib/Transforms/InstCombine/InstCombineShifts.cpp index 4ff9b64ac57cf..9aa679c60e47b 100644 --- a/lib/Transforms/InstCombine/InstCombineShifts.cpp +++ b/lib/Transforms/InstCombine/InstCombineShifts.cpp @@ -22,8 +22,8 @@ using namespace PatternMatch; #define DEBUG_TYPE "instcombine" Instruction *InstCombiner::commonShiftTransforms(BinaryOperator &I) { - assert(I.getOperand(1)->getType() == I.getOperand(0)->getType()); Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + assert(Op0->getType() == Op1->getType()); // See if we can fold away this shift. if (SimplifyDemandedInstructionBits(I)) @@ -65,63 +65,60 @@ Instruction *InstCombiner::commonShiftTransforms(BinaryOperator &I) { } /// Return true if we can simplify two logical (either left or right) shifts -/// that have constant shift amounts. -static bool canEvaluateShiftedShift(unsigned FirstShiftAmt, - bool IsFirstShiftLeft, - Instruction *SecondShift, InstCombiner &IC, +/// that have constant shift amounts: OuterShift (InnerShift X, C1), C2. +static bool canEvaluateShiftedShift(unsigned OuterShAmt, bool IsOuterShl, + Instruction *InnerShift, InstCombiner &IC, Instruction *CxtI) { - assert(SecondShift->isLogicalShift() && "Unexpected instruction type"); + assert(InnerShift->isLogicalShift() && "Unexpected instruction type"); - // We need constant shifts. - auto *SecondShiftConst = dyn_cast<ConstantInt>(SecondShift->getOperand(1)); - if (!SecondShiftConst) + // We need constant scalar or constant splat shifts. + const APInt *InnerShiftConst; + if (!match(InnerShift->getOperand(1), m_APInt(InnerShiftConst))) return false; - unsigned SecondShiftAmt = SecondShiftConst->getZExtValue(); - bool IsSecondShiftLeft = SecondShift->getOpcode() == Instruction::Shl; - - // We can always fold shl(c1) + shl(c2) -> shl(c1+c2). - // We can always fold lshr(c1) + lshr(c2) -> lshr(c1+c2). - if (IsFirstShiftLeft == IsSecondShiftLeft) + // Two logical shifts in the same direction: + // shl (shl X, C1), C2 --> shl X, C1 + C2 + // lshr (lshr X, C1), C2 --> lshr X, C1 + C2 + bool IsInnerShl = InnerShift->getOpcode() == Instruction::Shl; + if (IsInnerShl == IsOuterShl) return true; - // We can always fold lshr(c) + shl(c) -> and(c2). - // We can always fold shl(c) + lshr(c) -> and(c2). - if (FirstShiftAmt == SecondShiftAmt) + // Equal shift amounts in opposite directions become bitwise 'and': + // lshr (shl X, C), C --> and X, C' + // shl (lshr X, C), C --> and X, C' + unsigned InnerShAmt = InnerShiftConst->getZExtValue(); + if (InnerShAmt == OuterShAmt) return true; - unsigned TypeWidth = SecondShift->getType()->getScalarSizeInBits(); - // If the 2nd shift is bigger than the 1st, we can fold: - // lshr(c1) + shl(c2) -> shl(c3) + and(c4) or - // shl(c1) + lshr(c2) -> lshr(c3) + and(c4), + // lshr (shl X, C1), C2 --> and (shl X, C1 - C2), C3 + // shl (lshr X, C1), C2 --> and (lshr X, C1 - C2), C3 // but it isn't profitable unless we know the and'd out bits are already zero. - // Also check that the 2nd shift is valid (less than the type width) or we'll - // crash trying to produce the bit mask for the 'and'. - if (SecondShiftAmt > FirstShiftAmt && SecondShiftAmt < TypeWidth) { - unsigned MaskShift = IsSecondShiftLeft ? TypeWidth - SecondShiftAmt - : SecondShiftAmt - FirstShiftAmt; - APInt Mask = APInt::getLowBitsSet(TypeWidth, FirstShiftAmt) << MaskShift; - if (IC.MaskedValueIsZero(SecondShift->getOperand(0), Mask, 0, CxtI)) + // Also, check that the inner shift is valid (less than the type width) or + // we'll crash trying to produce the bit mask for the 'and'. + unsigned TypeWidth = InnerShift->getType()->getScalarSizeInBits(); + if (InnerShAmt > OuterShAmt && InnerShAmt < TypeWidth) { + unsigned MaskShift = + IsInnerShl ? TypeWidth - InnerShAmt : InnerShAmt - OuterShAmt; + APInt Mask = APInt::getLowBitsSet(TypeWidth, OuterShAmt) << MaskShift; + if (IC.MaskedValueIsZero(InnerShift->getOperand(0), Mask, 0, CxtI)) return true; } return false; } -/// See if we can compute the specified value, but shifted -/// logically to the left or right by some number of bits. This should return -/// true if the expression can be computed for the same cost as the current -/// expression tree. This is used to eliminate extraneous shifting from things -/// like: +/// See if we can compute the specified value, but shifted logically to the left +/// or right by some number of bits. This should return true if the expression +/// can be computed for the same cost as the current expression tree. This is +/// used to eliminate extraneous shifting from things like: /// %C = shl i128 %A, 64 /// %D = shl i128 %B, 96 /// %E = or i128 %C, %D /// %F = lshr i128 %E, 64 -/// where the client will ask if E can be computed shifted right by 64-bits. If -/// this succeeds, the GetShiftedValue function will be called to produce the -/// value. -static bool CanEvaluateShifted(Value *V, unsigned NumBits, bool IsLeftShift, +/// where the client will ask if E can be computed shifted right by 64-bits. If +/// this succeeds, getShiftedValue() will be called to produce the value. +static bool canEvaluateShifted(Value *V, unsigned NumBits, bool IsLeftShift, InstCombiner &IC, Instruction *CxtI) { // We can always evaluate constants shifted. if (isa<Constant>(V)) @@ -165,8 +162,8 @@ static bool CanEvaluateShifted(Value *V, unsigned NumBits, bool IsLeftShift, case Instruction::Or: case Instruction::Xor: // Bitwise operators can all arbitrarily be arbitrarily evaluated shifted. - return CanEvaluateShifted(I->getOperand(0), NumBits, IsLeftShift, IC, I) && - CanEvaluateShifted(I->getOperand(1), NumBits, IsLeftShift, IC, I); + return canEvaluateShifted(I->getOperand(0), NumBits, IsLeftShift, IC, I) && + canEvaluateShifted(I->getOperand(1), NumBits, IsLeftShift, IC, I); case Instruction::Shl: case Instruction::LShr: @@ -176,8 +173,8 @@ static bool CanEvaluateShifted(Value *V, unsigned NumBits, bool IsLeftShift, SelectInst *SI = cast<SelectInst>(I); Value *TrueVal = SI->getTrueValue(); Value *FalseVal = SI->getFalseValue(); - return CanEvaluateShifted(TrueVal, NumBits, IsLeftShift, IC, SI) && - CanEvaluateShifted(FalseVal, NumBits, IsLeftShift, IC, SI); + return canEvaluateShifted(TrueVal, NumBits, IsLeftShift, IC, SI) && + canEvaluateShifted(FalseVal, NumBits, IsLeftShift, IC, SI); } case Instruction::PHI: { // We can change a phi if we can change all operands. Note that we never @@ -185,16 +182,79 @@ static bool CanEvaluateShifted(Value *V, unsigned NumBits, bool IsLeftShift, // instructions with a single use. PHINode *PN = cast<PHINode>(I); for (Value *IncValue : PN->incoming_values()) - if (!CanEvaluateShifted(IncValue, NumBits, IsLeftShift, IC, PN)) + if (!canEvaluateShifted(IncValue, NumBits, IsLeftShift, IC, PN)) return false; return true; } } } -/// When CanEvaluateShifted returned true for an expression, -/// this value inserts the new computation that produces the shifted value. -static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, +/// Fold OuterShift (InnerShift X, C1), C2. +/// See canEvaluateShiftedShift() for the constraints on these instructions. +static Value *foldShiftedShift(BinaryOperator *InnerShift, unsigned OuterShAmt, + bool IsOuterShl, + InstCombiner::BuilderTy &Builder) { + bool IsInnerShl = InnerShift->getOpcode() == Instruction::Shl; + Type *ShType = InnerShift->getType(); + unsigned TypeWidth = ShType->getScalarSizeInBits(); + + // We only accept shifts-by-a-constant in canEvaluateShifted(). + const APInt *C1; + match(InnerShift->getOperand(1), m_APInt(C1)); + unsigned InnerShAmt = C1->getZExtValue(); + + // Change the shift amount and clear the appropriate IR flags. + auto NewInnerShift = [&](unsigned ShAmt) { + InnerShift->setOperand(1, ConstantInt::get(ShType, ShAmt)); + if (IsInnerShl) { + InnerShift->setHasNoUnsignedWrap(false); + InnerShift->setHasNoSignedWrap(false); + } else { + InnerShift->setIsExact(false); + } + return InnerShift; + }; + + // Two logical shifts in the same direction: + // shl (shl X, C1), C2 --> shl X, C1 + C2 + // lshr (lshr X, C1), C2 --> lshr X, C1 + C2 + if (IsInnerShl == IsOuterShl) { + // If this is an oversized composite shift, then unsigned shifts get 0. + if (InnerShAmt + OuterShAmt >= TypeWidth) + return Constant::getNullValue(ShType); + + return NewInnerShift(InnerShAmt + OuterShAmt); + } + + // Equal shift amounts in opposite directions become bitwise 'and': + // lshr (shl X, C), C --> and X, C' + // shl (lshr X, C), C --> and X, C' + if (InnerShAmt == OuterShAmt) { + APInt Mask = IsInnerShl + ? APInt::getLowBitsSet(TypeWidth, TypeWidth - OuterShAmt) + : APInt::getHighBitsSet(TypeWidth, TypeWidth - OuterShAmt); + Value *And = Builder.CreateAnd(InnerShift->getOperand(0), + ConstantInt::get(ShType, Mask)); + if (auto *AndI = dyn_cast<Instruction>(And)) { + AndI->moveBefore(InnerShift); + AndI->takeName(InnerShift); + } + return And; + } + + assert(InnerShAmt > OuterShAmt && + "Unexpected opposite direction logical shift pair"); + + // In general, we would need an 'and' for this transform, but + // canEvaluateShiftedShift() guarantees that the masked-off bits are not used. + // lshr (shl X, C1), C2 --> shl X, C1 - C2 + // shl (lshr X, C1), C2 --> lshr X, C1 - C2 + return NewInnerShift(InnerShAmt - OuterShAmt); +} + +/// When canEvaluateShifted() returns true for an expression, this function +/// inserts the new computation that produces the shifted value. +static Value *getShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, InstCombiner &IC, const DataLayout &DL) { // We can always evaluate constants shifted. if (Constant *C = dyn_cast<Constant>(V)) { @@ -220,100 +280,21 @@ static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, case Instruction::Xor: // Bitwise operators can all arbitrarily be arbitrarily evaluated shifted. I->setOperand( - 0, GetShiftedValue(I->getOperand(0), NumBits, isLeftShift, IC, DL)); + 0, getShiftedValue(I->getOperand(0), NumBits, isLeftShift, IC, DL)); I->setOperand( - 1, GetShiftedValue(I->getOperand(1), NumBits, isLeftShift, IC, DL)); + 1, getShiftedValue(I->getOperand(1), NumBits, isLeftShift, IC, DL)); return I; - case Instruction::Shl: { - BinaryOperator *BO = cast<BinaryOperator>(I); - unsigned TypeWidth = BO->getType()->getScalarSizeInBits(); - - // We only accept shifts-by-a-constant in CanEvaluateShifted. - ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1)); - - // We can always fold shl(c1)+shl(c2) -> shl(c1+c2). - if (isLeftShift) { - // If this is oversized composite shift, then unsigned shifts get 0. - unsigned NewShAmt = NumBits+CI->getZExtValue(); - if (NewShAmt >= TypeWidth) - return Constant::getNullValue(I->getType()); - - BO->setOperand(1, ConstantInt::get(BO->getType(), NewShAmt)); - BO->setHasNoUnsignedWrap(false); - BO->setHasNoSignedWrap(false); - return I; - } - - // We turn shl(c)+lshr(c) -> and(c2) if the input doesn't already have - // zeros. - if (CI->getValue() == NumBits) { - APInt Mask(APInt::getLowBitsSet(TypeWidth, TypeWidth - NumBits)); - V = IC.Builder->CreateAnd(BO->getOperand(0), - ConstantInt::get(BO->getContext(), Mask)); - if (Instruction *VI = dyn_cast<Instruction>(V)) { - VI->moveBefore(BO); - VI->takeName(BO); - } - return V; - } - - // We turn shl(c1)+shr(c2) -> shl(c3)+and(c4), but only when we know that - // the and won't be needed. - assert(CI->getZExtValue() > NumBits); - BO->setOperand(1, ConstantInt::get(BO->getType(), - CI->getZExtValue() - NumBits)); - BO->setHasNoUnsignedWrap(false); - BO->setHasNoSignedWrap(false); - return BO; - } - // FIXME: This is almost identical to the SHL case. Refactor both cases into - // a helper function. - case Instruction::LShr: { - BinaryOperator *BO = cast<BinaryOperator>(I); - unsigned TypeWidth = BO->getType()->getScalarSizeInBits(); - // We only accept shifts-by-a-constant in CanEvaluateShifted. - ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1)); - - // We can always fold lshr(c1)+lshr(c2) -> lshr(c1+c2). - if (!isLeftShift) { - // If this is oversized composite shift, then unsigned shifts get 0. - unsigned NewShAmt = NumBits+CI->getZExtValue(); - if (NewShAmt >= TypeWidth) - return Constant::getNullValue(BO->getType()); - - BO->setOperand(1, ConstantInt::get(BO->getType(), NewShAmt)); - BO->setIsExact(false); - return I; - } - - // We turn lshr(c)+shl(c) -> and(c2) if the input doesn't already have - // zeros. - if (CI->getValue() == NumBits) { - APInt Mask(APInt::getHighBitsSet(TypeWidth, TypeWidth - NumBits)); - V = IC.Builder->CreateAnd(I->getOperand(0), - ConstantInt::get(BO->getContext(), Mask)); - if (Instruction *VI = dyn_cast<Instruction>(V)) { - VI->moveBefore(I); - VI->takeName(I); - } - return V; - } - - // We turn lshr(c1)+shl(c2) -> lshr(c3)+and(c4), but only when we know that - // the and won't be needed. - assert(CI->getZExtValue() > NumBits); - BO->setOperand(1, ConstantInt::get(BO->getType(), - CI->getZExtValue() - NumBits)); - BO->setIsExact(false); - return BO; - } + case Instruction::Shl: + case Instruction::LShr: + return foldShiftedShift(cast<BinaryOperator>(I), NumBits, isLeftShift, + *(IC.Builder)); case Instruction::Select: I->setOperand( - 1, GetShiftedValue(I->getOperand(1), NumBits, isLeftShift, IC, DL)); + 1, getShiftedValue(I->getOperand(1), NumBits, isLeftShift, IC, DL)); I->setOperand( - 2, GetShiftedValue(I->getOperand(2), NumBits, isLeftShift, IC, DL)); + 2, getShiftedValue(I->getOperand(2), NumBits, isLeftShift, IC, DL)); return I; case Instruction::PHI: { // We can change a phi if we can change all operands. Note that we never @@ -321,215 +302,39 @@ static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, // instructions with a single use. PHINode *PN = cast<PHINode>(I); for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) - PN->setIncomingValue(i, GetShiftedValue(PN->getIncomingValue(i), NumBits, + PN->setIncomingValue(i, getShiftedValue(PN->getIncomingValue(i), NumBits, isLeftShift, IC, DL)); return PN; } } } -/// Try to fold (X << C1) << C2, where the shifts are some combination of -/// shl/ashr/lshr. -static Instruction * -foldShiftByConstOfShiftByConst(BinaryOperator &I, ConstantInt *COp1, - InstCombiner::BuilderTy *Builder) { - Value *Op0 = I.getOperand(0); - uint32_t TypeBits = Op0->getType()->getScalarSizeInBits(); - - // Find out if this is a shift of a shift by a constant. - BinaryOperator *ShiftOp = dyn_cast<BinaryOperator>(Op0); - if (ShiftOp && !ShiftOp->isShift()) - ShiftOp = nullptr; - - if (ShiftOp && isa<ConstantInt>(ShiftOp->getOperand(1))) { - - // This is a constant shift of a constant shift. Be careful about hiding - // shl instructions behind bit masks. They are used to represent multiplies - // by a constant, and it is important that simple arithmetic expressions - // are still recognizable by scalar evolution. - // - // The transforms applied to shl are very similar to the transforms applied - // to mul by constant. We can be more aggressive about optimizing right - // shifts. - // - // Combinations of right and left shifts will still be optimized in - // DAGCombine where scalar evolution no longer applies. - - ConstantInt *ShiftAmt1C = cast<ConstantInt>(ShiftOp->getOperand(1)); - uint32_t ShiftAmt1 = ShiftAmt1C->getLimitedValue(TypeBits); - uint32_t ShiftAmt2 = COp1->getLimitedValue(TypeBits); - assert(ShiftAmt2 != 0 && "Should have been simplified earlier"); - if (ShiftAmt1 == 0) - return nullptr; // Will be simplified in the future. - Value *X = ShiftOp->getOperand(0); - - IntegerType *Ty = cast<IntegerType>(I.getType()); - - // Check for (X << c1) << c2 and (X >> c1) >> c2 - if (I.getOpcode() == ShiftOp->getOpcode()) { - uint32_t AmtSum = ShiftAmt1 + ShiftAmt2; // Fold into one big shift. - // If this is an oversized composite shift, then unsigned shifts become - // zero (handled in InstSimplify) and ashr saturates. - if (AmtSum >= TypeBits) { - if (I.getOpcode() != Instruction::AShr) - return nullptr; - AmtSum = TypeBits - 1; // Saturate to 31 for i32 ashr. - } - - return BinaryOperator::Create(I.getOpcode(), X, - ConstantInt::get(Ty, AmtSum)); - } - - if (ShiftAmt1 == ShiftAmt2) { - // If we have ((X << C) >>u C), turn this into X & (-1 >>u C). - if (I.getOpcode() == Instruction::LShr && - ShiftOp->getOpcode() == Instruction::Shl) { - APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt1)); - return BinaryOperator::CreateAnd( - X, ConstantInt::get(I.getContext(), Mask)); - } - } else if (ShiftAmt1 < ShiftAmt2) { - uint32_t ShiftDiff = ShiftAmt2 - ShiftAmt1; - - // (X >>?,exact C1) << C2 --> X << (C2-C1) - // The inexact version is deferred to DAGCombine so we don't hide shl - // behind a bit mask. - if (I.getOpcode() == Instruction::Shl && - ShiftOp->getOpcode() != Instruction::Shl && ShiftOp->isExact()) { - assert(ShiftOp->getOpcode() == Instruction::LShr || - ShiftOp->getOpcode() == Instruction::AShr); - ConstantInt *ShiftDiffCst = ConstantInt::get(Ty, ShiftDiff); - BinaryOperator *NewShl = - BinaryOperator::Create(Instruction::Shl, X, ShiftDiffCst); - NewShl->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); - NewShl->setHasNoSignedWrap(I.hasNoSignedWrap()); - return NewShl; - } - - // (X << C1) >>u C2 --> X >>u (C2-C1) & (-1 >> C2) - if (I.getOpcode() == Instruction::LShr && - ShiftOp->getOpcode() == Instruction::Shl) { - ConstantInt *ShiftDiffCst = ConstantInt::get(Ty, ShiftDiff); - // (X <<nuw C1) >>u C2 --> X >>u (C2-C1) - if (ShiftOp->hasNoUnsignedWrap()) { - BinaryOperator *NewLShr = - BinaryOperator::Create(Instruction::LShr, X, ShiftDiffCst); - NewLShr->setIsExact(I.isExact()); - return NewLShr; - } - Value *Shift = Builder->CreateLShr(X, ShiftDiffCst); - - APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2)); - return BinaryOperator::CreateAnd( - Shift, ConstantInt::get(I.getContext(), Mask)); - } - - // We can't handle (X << C1) >>s C2, it shifts arbitrary bits in. However, - // we can handle (X <<nsw C1) >>s C2 since it only shifts in sign bits. - if (I.getOpcode() == Instruction::AShr && - ShiftOp->getOpcode() == Instruction::Shl) { - if (ShiftOp->hasNoSignedWrap()) { - // (X <<nsw C1) >>s C2 --> X >>s (C2-C1) - ConstantInt *ShiftDiffCst = ConstantInt::get(Ty, ShiftDiff); - BinaryOperator *NewAShr = - BinaryOperator::Create(Instruction::AShr, X, ShiftDiffCst); - NewAShr->setIsExact(I.isExact()); - return NewAShr; - } - } - } else { - assert(ShiftAmt2 < ShiftAmt1); - uint32_t ShiftDiff = ShiftAmt1 - ShiftAmt2; - - // (X >>?exact C1) << C2 --> X >>?exact (C1-C2) - // The inexact version is deferred to DAGCombine so we don't hide shl - // behind a bit mask. - if (I.getOpcode() == Instruction::Shl && - ShiftOp->getOpcode() != Instruction::Shl && ShiftOp->isExact()) { - ConstantInt *ShiftDiffCst = ConstantInt::get(Ty, ShiftDiff); - BinaryOperator *NewShr = - BinaryOperator::Create(ShiftOp->getOpcode(), X, ShiftDiffCst); - NewShr->setIsExact(true); - return NewShr; - } - - // (X << C1) >>u C2 --> X << (C1-C2) & (-1 >> C2) - if (I.getOpcode() == Instruction::LShr && - ShiftOp->getOpcode() == Instruction::Shl) { - ConstantInt *ShiftDiffCst = ConstantInt::get(Ty, ShiftDiff); - if (ShiftOp->hasNoUnsignedWrap()) { - // (X <<nuw C1) >>u C2 --> X <<nuw (C1-C2) - BinaryOperator *NewShl = - BinaryOperator::Create(Instruction::Shl, X, ShiftDiffCst); - NewShl->setHasNoUnsignedWrap(true); - return NewShl; - } - Value *Shift = Builder->CreateShl(X, ShiftDiffCst); - - APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2)); - return BinaryOperator::CreateAnd( - Shift, ConstantInt::get(I.getContext(), Mask)); - } - - // We can't handle (X << C1) >>s C2, it shifts arbitrary bits in. However, - // we can handle (X <<nsw C1) >>s C2 since it only shifts in sign bits. - if (I.getOpcode() == Instruction::AShr && - ShiftOp->getOpcode() == Instruction::Shl) { - if (ShiftOp->hasNoSignedWrap()) { - // (X <<nsw C1) >>s C2 --> X <<nsw (C1-C2) - ConstantInt *ShiftDiffCst = ConstantInt::get(Ty, ShiftDiff); - BinaryOperator *NewShl = - BinaryOperator::Create(Instruction::Shl, X, ShiftDiffCst); - NewShl->setHasNoSignedWrap(true); - return NewShl; - } - } - } - } - - return nullptr; -} - Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, Constant *Op1, BinaryOperator &I) { bool isLeftShift = I.getOpcode() == Instruction::Shl; - ConstantInt *COp1 = nullptr; - if (ConstantDataVector *CV = dyn_cast<ConstantDataVector>(Op1)) - COp1 = dyn_cast_or_null<ConstantInt>(CV->getSplatValue()); - else if (ConstantVector *CV = dyn_cast<ConstantVector>(Op1)) - COp1 = dyn_cast_or_null<ConstantInt>(CV->getSplatValue()); - else - COp1 = dyn_cast<ConstantInt>(Op1); - - if (!COp1) + const APInt *Op1C; + if (!match(Op1, m_APInt(Op1C))) return nullptr; // See if we can propagate this shift into the input, this covers the trivial // cast of lshr(shl(x,c1),c2) as well as other more complex cases. if (I.getOpcode() != Instruction::AShr && - CanEvaluateShifted(Op0, COp1->getZExtValue(), isLeftShift, *this, &I)) { + canEvaluateShifted(Op0, Op1C->getZExtValue(), isLeftShift, *this, &I)) { DEBUG(dbgs() << "ICE: GetShiftedValue propagating shift through expression" " to eliminate shift:\n IN: " << *Op0 << "\n SH: " << I <<"\n"); return replaceInstUsesWith( - I, GetShiftedValue(Op0, COp1->getZExtValue(), isLeftShift, *this, DL)); + I, getShiftedValue(Op0, Op1C->getZExtValue(), isLeftShift, *this, DL)); } // See if we can simplify any instructions used by the instruction whose sole // purpose is to compute bits we don't care about. - uint32_t TypeBits = Op0->getType()->getScalarSizeInBits(); + unsigned TypeBits = Op0->getType()->getScalarSizeInBits(); - assert(!COp1->uge(TypeBits) && + assert(!Op1C->uge(TypeBits) && "Shift over the type width should have been removed already"); - // ((X*C1) << C2) == (X * (C1 << C2)) - if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) - if (BO->getOpcode() == Instruction::Mul && isLeftShift) - if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1))) - return BinaryOperator::CreateMul(BO->getOperand(0), - ConstantExpr::getShl(BOOp, Op1)); - if (Instruction *FoldedShift = foldOpWithConstantIntoOperand(I)) return FoldedShift; @@ -544,7 +349,8 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, Constant *Op1, if (TrOp && I.isLogicalShift() && TrOp->isShift() && isa<ConstantInt>(TrOp->getOperand(1))) { // Okay, we'll do this xform. Make the shift of shift. - Constant *ShAmt = ConstantExpr::getZExt(COp1, TrOp->getType()); + Constant *ShAmt = + ConstantExpr::getZExt(cast<Constant>(Op1), TrOp->getType()); // (shift2 (shift1 & 0x00FF), c2) Value *NSh = Builder->CreateBinOp(I.getOpcode(), TrOp, ShAmt,I.getName()); @@ -561,10 +367,10 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, Constant *Op1, // shift. We know that it is a logical shift by a constant, so adjust the // mask as appropriate. if (I.getOpcode() == Instruction::Shl) - MaskV <<= COp1->getZExtValue(); + MaskV <<= Op1C->getZExtValue(); else { assert(I.getOpcode() == Instruction::LShr && "Unknown logical shift"); - MaskV = MaskV.lshr(COp1->getZExtValue()); + MaskV = MaskV.lshr(Op1C->getZExtValue()); } // shift1 & 0x00FF @@ -598,7 +404,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, Constant *Op1, // (X + (Y << C)) Value *X = Builder->CreateBinOp(Op0BO->getOpcode(), YS, V1, Op0BO->getOperand(1)->getName()); - uint32_t Op1Val = COp1->getLimitedValue(TypeBits); + unsigned Op1Val = Op1C->getLimitedValue(TypeBits); APInt Bits = APInt::getHighBitsSet(TypeBits, TypeBits - Op1Val); Constant *Mask = ConstantInt::get(I.getContext(), Bits); @@ -634,7 +440,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, Constant *Op1, // (X + (Y << C)) Value *X = Builder->CreateBinOp(Op0BO->getOpcode(), V1, YS, Op0BO->getOperand(0)->getName()); - uint32_t Op1Val = COp1->getLimitedValue(TypeBits); + unsigned Op1Val = Op1C->getLimitedValue(TypeBits); APInt Bits = APInt::getHighBitsSet(TypeBits, TypeBits - Op1Val); Constant *Mask = ConstantInt::get(I.getContext(), Bits); @@ -705,9 +511,6 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, Constant *Op1, } } - if (Instruction *Folded = foldShiftByConstOfShiftByConst(I, COp1, Builder)) - return Folded; - return nullptr; } @@ -715,59 +518,97 @@ Instruction *InstCombiner::visitShl(BinaryOperator &I) { if (Value *V = SimplifyVectorOp(I)) return replaceInstUsesWith(I, V); - if (Value *V = - SimplifyShlInst(I.getOperand(0), I.getOperand(1), I.hasNoSignedWrap(), - I.hasNoUnsignedWrap(), DL, &TLI, &DT, &AC)) + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + if (Value *V = SimplifyShlInst(Op0, Op1, I.hasNoSignedWrap(), + I.hasNoUnsignedWrap(), DL, &TLI, &DT, &AC)) return replaceInstUsesWith(I, V); if (Instruction *V = commonShiftTransforms(I)) return V; - if (ConstantInt *Op1C = dyn_cast<ConstantInt>(I.getOperand(1))) { - unsigned ShAmt = Op1C->getZExtValue(); - - // Turn: - // %zext = zext i32 %V to i64 - // %res = shl i64 %V, 8 - // - // Into: - // %shl = shl i32 %V, 8 - // %res = zext i32 %shl to i64 - // - // This is only valid if %V would have zeros shifted out. - if (auto *ZI = dyn_cast<ZExtInst>(I.getOperand(0))) { - unsigned SrcBitWidth = ZI->getSrcTy()->getScalarSizeInBits(); - if (ShAmt < SrcBitWidth && - MaskedValueIsZero(ZI->getOperand(0), - APInt::getHighBitsSet(SrcBitWidth, ShAmt), 0, &I)) { - auto *Shl = Builder->CreateShl(ZI->getOperand(0), ShAmt); - return new ZExtInst(Shl, I.getType()); + const APInt *ShAmtAPInt; + if (match(Op1, m_APInt(ShAmtAPInt))) { + unsigned ShAmt = ShAmtAPInt->getZExtValue(); + unsigned BitWidth = I.getType()->getScalarSizeInBits(); + Type *Ty = I.getType(); + + // shl (zext X), ShAmt --> zext (shl X, ShAmt) + // This is only valid if X would have zeros shifted out. + Value *X; + if (match(Op0, m_ZExt(m_Value(X)))) { + unsigned SrcWidth = X->getType()->getScalarSizeInBits(); + if (ShAmt < SrcWidth && + MaskedValueIsZero(X, APInt::getHighBitsSet(SrcWidth, ShAmt), 0, &I)) + return new ZExtInst(Builder->CreateShl(X, ShAmt), Ty); + } + + // (X >>u C) << C --> X & (-1 << C) + if (match(Op0, m_LShr(m_Value(X), m_Specific(Op1)))) { + APInt Mask(APInt::getHighBitsSet(BitWidth, BitWidth - ShAmt)); + return BinaryOperator::CreateAnd(X, ConstantInt::get(Ty, Mask)); + } + + // Be careful about hiding shl instructions behind bit masks. They are used + // to represent multiplies by a constant, and it is important that simple + // arithmetic expressions are still recognizable by scalar evolution. + // The inexact versions are deferred to DAGCombine, so we don't hide shl + // behind a bit mask. + const APInt *ShOp1; + if (match(Op0, m_CombineOr(m_Exact(m_LShr(m_Value(X), m_APInt(ShOp1))), + m_Exact(m_AShr(m_Value(X), m_APInt(ShOp1)))))) { + unsigned ShrAmt = ShOp1->getZExtValue(); + if (ShrAmt < ShAmt) { + // If C1 < C2: (X >>?,exact C1) << C2 --> X << (C2 - C1) + Constant *ShiftDiff = ConstantInt::get(Ty, ShAmt - ShrAmt); + auto *NewShl = BinaryOperator::CreateShl(X, ShiftDiff); + NewShl->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); + NewShl->setHasNoSignedWrap(I.hasNoSignedWrap()); + return NewShl; } + if (ShrAmt > ShAmt) { + // If C1 > C2: (X >>?exact C1) << C2 --> X >>?exact (C1 - C2) + Constant *ShiftDiff = ConstantInt::get(Ty, ShrAmt - ShAmt); + auto *NewShr = BinaryOperator::Create( + cast<BinaryOperator>(Op0)->getOpcode(), X, ShiftDiff); + NewShr->setIsExact(true); + return NewShr; + } + } + + if (match(Op0, m_Shl(m_Value(X), m_APInt(ShOp1)))) { + unsigned AmtSum = ShAmt + ShOp1->getZExtValue(); + // Oversized shifts are simplified to zero in InstSimplify. + if (AmtSum < BitWidth) + // (X << C1) << C2 --> X << (C1 + C2) + return BinaryOperator::CreateShl(X, ConstantInt::get(Ty, AmtSum)); } // If the shifted-out value is known-zero, then this is a NUW shift. if (!I.hasNoUnsignedWrap() && - MaskedValueIsZero(I.getOperand(0), - APInt::getHighBitsSet(Op1C->getBitWidth(), ShAmt), 0, - &I)) { + MaskedValueIsZero(Op0, APInt::getHighBitsSet(BitWidth, ShAmt), 0, &I)) { I.setHasNoUnsignedWrap(); return &I; } - // If the shifted out value is all signbits, this is a NSW shift. - if (!I.hasNoSignedWrap() && - ComputeNumSignBits(I.getOperand(0), 0, &I) > ShAmt) { + // If the shifted-out value is all signbits, then this is a NSW shift. + if (!I.hasNoSignedWrap() && ComputeNumSignBits(Op0, 0, &I) > ShAmt) { I.setHasNoSignedWrap(); return &I; } } - // (C1 << A) << C2 -> (C1 << C2) << A - Constant *C1, *C2; - Value *A; - if (match(I.getOperand(0), m_OneUse(m_Shl(m_Constant(C1), m_Value(A)))) && - match(I.getOperand(1), m_Constant(C2))) - return BinaryOperator::CreateShl(ConstantExpr::getShl(C1, C2), A); + Constant *C1; + if (match(Op1, m_Constant(C1))) { + Constant *C2; + Value *X; + // (C2 << X) << C1 --> (C2 << C1) << X + if (match(Op0, m_OneUse(m_Shl(m_Constant(C2), m_Value(X))))) + return BinaryOperator::CreateShl(ConstantExpr::getShl(C2, C1), X); + + // (X * C2) << C1 --> X * (C2 << C1) + if (match(Op0, m_Mul(m_Value(X), m_Constant(C2)))) + return BinaryOperator::CreateMul(X, ConstantExpr::getShl(C2, C1)); + } return nullptr; } @@ -776,43 +617,83 @@ Instruction *InstCombiner::visitLShr(BinaryOperator &I) { if (Value *V = SimplifyVectorOp(I)) return replaceInstUsesWith(I, V); - if (Value *V = SimplifyLShrInst(I.getOperand(0), I.getOperand(1), I.isExact(), - DL, &TLI, &DT, &AC)) + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + if (Value *V = SimplifyLShrInst(Op0, Op1, I.isExact(), DL, &TLI, &DT, &AC)) return replaceInstUsesWith(I, V); if (Instruction *R = commonShiftTransforms(I)) return R; - Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); - - if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) { - unsigned ShAmt = Op1C->getZExtValue(); - - if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0)) { - unsigned BitWidth = Op0->getType()->getScalarSizeInBits(); + Type *Ty = I.getType(); + const APInt *ShAmtAPInt; + if (match(Op1, m_APInt(ShAmtAPInt))) { + unsigned ShAmt = ShAmtAPInt->getZExtValue(); + unsigned BitWidth = Ty->getScalarSizeInBits(); + auto *II = dyn_cast<IntrinsicInst>(Op0); + if (II && isPowerOf2_32(BitWidth) && Log2_32(BitWidth) == ShAmt && + (II->getIntrinsicID() == Intrinsic::ctlz || + II->getIntrinsicID() == Intrinsic::cttz || + II->getIntrinsicID() == Intrinsic::ctpop)) { // ctlz.i32(x)>>5 --> zext(x == 0) // cttz.i32(x)>>5 --> zext(x == 0) // ctpop.i32(x)>>5 --> zext(x == -1) - if ((II->getIntrinsicID() == Intrinsic::ctlz || - II->getIntrinsicID() == Intrinsic::cttz || - II->getIntrinsicID() == Intrinsic::ctpop) && - isPowerOf2_32(BitWidth) && Log2_32(BitWidth) == ShAmt) { - bool isCtPop = II->getIntrinsicID() == Intrinsic::ctpop; - Constant *RHS = ConstantInt::getSigned(Op0->getType(), isCtPop ? -1:0); - Value *Cmp = Builder->CreateICmpEQ(II->getArgOperand(0), RHS); - return new ZExtInst(Cmp, II->getType()); + bool IsPop = II->getIntrinsicID() == Intrinsic::ctpop; + Constant *RHS = ConstantInt::getSigned(Ty, IsPop ? -1 : 0); + Value *Cmp = Builder->CreateICmpEQ(II->getArgOperand(0), RHS); + return new ZExtInst(Cmp, Ty); + } + + Value *X; + const APInt *ShOp1; + if (match(Op0, m_Shl(m_Value(X), m_APInt(ShOp1)))) { + unsigned ShlAmt = ShOp1->getZExtValue(); + if (ShlAmt < ShAmt) { + Constant *ShiftDiff = ConstantInt::get(Ty, ShAmt - ShlAmt); + if (cast<BinaryOperator>(Op0)->hasNoUnsignedWrap()) { + // (X <<nuw C1) >>u C2 --> X >>u (C2 - C1) + auto *NewLShr = BinaryOperator::CreateLShr(X, ShiftDiff); + NewLShr->setIsExact(I.isExact()); + return NewLShr; + } + // (X << C1) >>u C2 --> (X >>u (C2 - C1)) & (-1 >> C2) + Value *NewLShr = Builder->CreateLShr(X, ShiftDiff, "", I.isExact()); + APInt Mask(APInt::getLowBitsSet(BitWidth, BitWidth - ShAmt)); + return BinaryOperator::CreateAnd(NewLShr, ConstantInt::get(Ty, Mask)); } + if (ShlAmt > ShAmt) { + Constant *ShiftDiff = ConstantInt::get(Ty, ShlAmt - ShAmt); + if (cast<BinaryOperator>(Op0)->hasNoUnsignedWrap()) { + // (X <<nuw C1) >>u C2 --> X <<nuw (C1 - C2) + auto *NewShl = BinaryOperator::CreateShl(X, ShiftDiff); + NewShl->setHasNoUnsignedWrap(true); + return NewShl; + } + // (X << C1) >>u C2 --> X << (C1 - C2) & (-1 >> C2) + Value *NewShl = Builder->CreateShl(X, ShiftDiff); + APInt Mask(APInt::getLowBitsSet(BitWidth, BitWidth - ShAmt)); + return BinaryOperator::CreateAnd(NewShl, ConstantInt::get(Ty, Mask)); + } + assert(ShlAmt == ShAmt); + // (X << C) >>u C --> X & (-1 >>u C) + APInt Mask(APInt::getLowBitsSet(BitWidth, BitWidth - ShAmt)); + return BinaryOperator::CreateAnd(X, ConstantInt::get(Ty, Mask)); + } + + if (match(Op0, m_LShr(m_Value(X), m_APInt(ShOp1)))) { + unsigned AmtSum = ShAmt + ShOp1->getZExtValue(); + // Oversized shifts are simplified to zero in InstSimplify. + if (AmtSum < BitWidth) + // (X >>u C1) >>u C2 --> X >>u (C1 + C2) + return BinaryOperator::CreateLShr(X, ConstantInt::get(Ty, AmtSum)); } // If the shifted-out value is known-zero, then this is an exact shift. if (!I.isExact() && - MaskedValueIsZero(Op0, APInt::getLowBitsSet(Op1C->getBitWidth(), ShAmt), - 0, &I)){ + MaskedValueIsZero(Op0, APInt::getLowBitsSet(BitWidth, ShAmt), 0, &I)) { I.setIsExact(); return &I; } } - return nullptr; } @@ -820,48 +701,66 @@ Instruction *InstCombiner::visitAShr(BinaryOperator &I) { if (Value *V = SimplifyVectorOp(I)) return replaceInstUsesWith(I, V); - if (Value *V = SimplifyAShrInst(I.getOperand(0), I.getOperand(1), I.isExact(), - DL, &TLI, &DT, &AC)) + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + if (Value *V = SimplifyAShrInst(Op0, Op1, I.isExact(), DL, &TLI, &DT, &AC)) return replaceInstUsesWith(I, V); if (Instruction *R = commonShiftTransforms(I)) return R; - Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); - - if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) { - unsigned ShAmt = Op1C->getZExtValue(); + Type *Ty = I.getType(); + unsigned BitWidth = Ty->getScalarSizeInBits(); + const APInt *ShAmtAPInt; + if (match(Op1, m_APInt(ShAmtAPInt))) { + unsigned ShAmt = ShAmtAPInt->getZExtValue(); - // If the input is a SHL by the same constant (ashr (shl X, C), C), then we - // have a sign-extend idiom. + // If the shift amount equals the difference in width of the destination + // and source scalar types: + // ashr (shl (zext X), C), C --> sext X Value *X; - if (match(Op0, m_Shl(m_Value(X), m_Specific(Op1)))) { - // If the input is an extension from the shifted amount value, e.g. - // %x = zext i8 %A to i32 - // %y = shl i32 %x, 24 - // %z = ashr %y, 24 - // then turn this into "z = sext i8 A to i32". - if (ZExtInst *ZI = dyn_cast<ZExtInst>(X)) { - uint32_t SrcBits = ZI->getOperand(0)->getType()->getScalarSizeInBits(); - uint32_t DestBits = ZI->getType()->getScalarSizeInBits(); - if (Op1C->getZExtValue() == DestBits-SrcBits) - return new SExtInst(ZI->getOperand(0), ZI->getType()); + if (match(Op0, m_Shl(m_ZExt(m_Value(X)), m_Specific(Op1))) && + ShAmt == BitWidth - X->getType()->getScalarSizeInBits()) + return new SExtInst(X, Ty); + + // We can't handle (X << C1) >>s C2. It shifts arbitrary bits in. However, + // we can handle (X <<nsw C1) >>s C2 since it only shifts in sign bits. + const APInt *ShOp1; + if (match(Op0, m_NSWShl(m_Value(X), m_APInt(ShOp1)))) { + unsigned ShlAmt = ShOp1->getZExtValue(); + if (ShlAmt < ShAmt) { + // (X <<nsw C1) >>s C2 --> X >>s (C2 - C1) + Constant *ShiftDiff = ConstantInt::get(Ty, ShAmt - ShlAmt); + auto *NewAShr = BinaryOperator::CreateAShr(X, ShiftDiff); + NewAShr->setIsExact(I.isExact()); + return NewAShr; } + if (ShlAmt > ShAmt) { + // (X <<nsw C1) >>s C2 --> X <<nsw (C1 - C2) + Constant *ShiftDiff = ConstantInt::get(Ty, ShlAmt - ShAmt); + auto *NewShl = BinaryOperator::Create(Instruction::Shl, X, ShiftDiff); + NewShl->setHasNoSignedWrap(true); + return NewShl; + } + } + + if (match(Op0, m_AShr(m_Value(X), m_APInt(ShOp1)))) { + unsigned AmtSum = ShAmt + ShOp1->getZExtValue(); + // Oversized arithmetic shifts replicate the sign bit. + AmtSum = std::min(AmtSum, BitWidth - 1); + // (X >>s C1) >>s C2 --> X >>s (C1 + C2) + return BinaryOperator::CreateAShr(X, ConstantInt::get(Ty, AmtSum)); } // If the shifted-out value is known-zero, then this is an exact shift. if (!I.isExact() && - MaskedValueIsZero(Op0, APInt::getLowBitsSet(Op1C->getBitWidth(), ShAmt), - 0, &I)) { + MaskedValueIsZero(Op0, APInt::getLowBitsSet(BitWidth, ShAmt), 0, &I)) { I.setIsExact(); return &I; } } // See if we can turn a signed shr into an unsigned shr. - if (MaskedValueIsZero(Op0, - APInt::getSignBit(I.getType()->getScalarSizeInBits()), - 0, &I)) + if (MaskedValueIsZero(Op0, APInt::getSignBit(BitWidth), 0, &I)) return BinaryOperator::CreateLShr(Op0, Op1); return nullptr; |