diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index b032b07f29ac..f0b04b7133d0 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -1409,6 +1409,37 @@ static void computeKnownBitsFromOperator(Operator *I, APInt &KnownZero, } } +static unsigned getAlignment(Value *V, const DataLayout &DL) { + unsigned Align = 0; + if (auto *GO = dyn_cast(V)) { + Align = GO->getAlignment(); + if (Align == 0) { + if (auto *GVar = dyn_cast(GO)) { + Type *ObjectType = GVar->getType()->getElementType(); + if (ObjectType->isSized()) { + // If the object is defined in the current Module, we'll be giving + // it the preferred alignment. Otherwise, we have to assume that it + // may only have the minimum ABI alignment. + if (GVar->isStrongDefinitionForLinker()) + Align = DL.getPreferredAlignment(GVar); + else + Align = DL.getABITypeAlignment(ObjectType); + } + } + } + } else if (Argument *A = dyn_cast(V)) { + Align = A->getType()->isPointerTy() ? A->getParamAlignment() : 0; + + if (!Align && A->hasStructRetAttr()) { + // An sret parameter has at least the ABI alignment of the return type. + Type *EltTy = cast(A->getType())->getElementType(); + if (EltTy->isSized()) + Align = DL.getABITypeAlignment(EltTy); + } + } + return Align; +} + /// Determine which bits of V are known to be either zero or one and return /// them in the KnownZero/KnownOne bit sets. /// @@ -1469,59 +1500,6 @@ void computeKnownBits(Value *V, APInt &KnownZero, APInt &KnownOne, return; } - // The address of an aligned GlobalValue has trailing zeros. - if (auto *GO = dyn_cast(V)) { - unsigned Align = GO->getAlignment(); - if (Align == 0) { - if (auto *GVar = dyn_cast(GO)) { - Type *ObjectType = GVar->getType()->getElementType(); - if (ObjectType->isSized()) { - // If the object is defined in the current Module, we'll be giving - // it the preferred alignment. Otherwise, we have to assume that it - // may only have the minimum ABI alignment. - if (GVar->isStrongDefinitionForLinker()) - Align = DL.getPreferredAlignment(GVar); - else - Align = DL.getABITypeAlignment(ObjectType); - } - } - } - if (Align > 0) - KnownZero = APInt::getLowBitsSet(BitWidth, - countTrailingZeros(Align)); - else - KnownZero.clearAllBits(); - KnownOne.clearAllBits(); - return; - } - - if (Argument *A = dyn_cast(V)) { - unsigned Align = A->getType()->isPointerTy() ? A->getParamAlignment() : 0; - - if (!Align && A->hasStructRetAttr()) { - // An sret parameter has at least the ABI alignment of the return type. - Type *EltTy = cast(A->getType())->getElementType(); - if (EltTy->isSized()) - Align = DL.getABITypeAlignment(EltTy); - } - - if (Align) - KnownZero = APInt::getLowBitsSet(BitWidth, countTrailingZeros(Align)); - else - KnownZero.clearAllBits(); - KnownOne.clearAllBits(); - - // Don't give up yet... there might be an assumption that provides more - // information... - computeKnownBitsFromAssume(V, KnownZero, KnownOne, DL, Depth, Q); - - // Or a dominating condition for that matter - if (EnableDomConditions && Depth <= DomConditionsMaxDepth) - computeKnownBitsFromDominatingCondition(V, KnownZero, KnownOne, DL, - Depth, Q); - return; - } - // Start out not knowing anything. KnownZero.clearAllBits(); KnownOne.clearAllBits(); @@ -1541,6 +1519,13 @@ void computeKnownBits(Value *V, APInt &KnownZero, APInt &KnownOne, if (Operator *I = dyn_cast(V)) computeKnownBitsFromOperator(I, KnownZero, KnownOne, DL, Depth, Q); + // Aligned pointers have trailing zeros - refine KnownZero set + if (V->getType()->isPointerTy()) { + unsigned Align = getAlignment(V, DL); + if (Align) + KnownZero |= APInt::getLowBitsSet(BitWidth, countTrailingZeros(Align)); + } + // computeKnownBitsFromAssume and computeKnownBitsFromDominatingCondition // strictly refines KnownZero and KnownOne. Therefore, we run them after // computeKnownBitsFromOperator.