diff options
| -rw-r--r-- | lib/Transforms/Scalar/SROA.cpp | 30 |
1 files changed, 20 insertions, 10 deletions
diff --git a/lib/Transforms/Scalar/SROA.cpp b/lib/Transforms/Scalar/SROA.cpp index a0fcf21231..8c999bccf6 100644 --- a/lib/Transforms/Scalar/SROA.cpp +++ b/lib/Transforms/Scalar/SROA.cpp @@ -2302,7 +2302,14 @@ private: /// /// This recurses through the aggregate type and tries to compute a subtype /// based on the offset and size. When the offset and size span a sub-section -/// of an array, it will even compute a new array type for that sub-section. +/// of an array, it will even compute a new array type for that sub-section, +/// and the same for structs. +/// +/// Note that this routine is very strict and tries to find a partition of the +/// type which produces the *exact* right offset and size. It is not forgiving +/// when the size or offset cause either end of type-based partition to be off. +/// Also, this is a best-effort routine. It is reasonable to give up and not +/// return a type if necessary. static Type *getTypePartition(const TargetData &TD, Type *Ty, uint64_t Offset, uint64_t Size) { if (Offset == 0 && TD.getTypeAllocSize(Ty) == Size) @@ -2348,15 +2355,13 @@ static Type *getTypePartition(const TargetData &TD, Type *Ty, return 0; const StructLayout *SL = TD.getStructLayout(STy); - if (Offset > SL->getSizeInBytes()) + if (Offset >= SL->getSizeInBytes()) return 0; uint64_t EndOffset = Offset + Size; if (EndOffset > SL->getSizeInBytes()) return 0; unsigned Index = SL->getElementContainingOffset(Offset); - if (SL->getElementOffset(Index) != Offset) - return 0; // Inside of padding. Offset -= SL->getElementOffset(Index); Type *ElementTy = STy->getElementType(Index); @@ -2381,8 +2386,15 @@ static Type *getTypePartition(const TargetData &TD, Type *Ty, unsigned EndIndex = SL->getElementContainingOffset(EndOffset); if (Index == EndIndex) return 0; // Within a single element and its padding. + + // Don't try to form "natural" types if the elements don't line up with the + // expected size. + // FIXME: We could potentially recurse down through the last element in the + // sub-struct to find a natural end point. + if (SL->getElementOffset(EndIndex) != EndOffset) + return 0; + assert(Index < EndIndex); - assert(Index + EndIndex <= STy->getNumElements()); EE = STy->element_begin() + EndIndex; } @@ -2394,12 +2406,10 @@ static Type *getTypePartition(const TargetData &TD, Type *Ty, StructType *SubTy = StructType::get(STy->getContext(), ElementTys, STy->isPacked()); const StructLayout *SubSL = TD.getStructLayout(SubTy); - if (Size == SubSL->getSizeInBytes()) - return SubTy; + if (Size != SubSL->getSizeInBytes()) + return 0; // The sub-struct doesn't have quite the size needed. - // FIXME: We could potentially recurse down through the last element in the - // sub-struct to find a natural end point. - return 0; + return SubTy; } /// \brief Rewrite an alloca partition's users. |