[cherry-pick][stable/20230725] [lldb][DataFormatter] VectorType: fix format for arrays with size not a power-of-2 #7622
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… a power-of-2 (llvm#68907) To get the number of children for a VectorType (i.e., a type declared with a `vector_size`/`ext_vector_type` attribute) LLDB previously did following calculation: 1. Get byte-size of the vector container from Clang (`getTypeInfo`). 2. Get byte-size of the element type we want to interpret the array as. (e.g., sometimes we want to interpret an `unsigned char vec[16]` as a `float32[]`). 3. `numChildren = containerSize / reinterpretedElementSize` However, for step 1, clang will return us the *aligned* container byte-size. So for a type such as `float __attribute__((ext_vector_type(3)))` (which is an array of 3 4-byte floats), clang will round up the byte-width of the array to `16`. (see [here](https://github.com/llvm/llvm-project/blob/ab6a66dbec61654d0962f6abf6d6c5b776937584/clang/lib/AST/ASTContext.cpp#L1987-L1992)) This means that for vectors where the size isn't a power-of-2, LLDB will miscalculate the number of elements. **Solution** This patch changes step 1 such that we calculate the container size as `numElementsInSource * byteSizeOfElement`. (cherry picked from commit 0dfcfb5)
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To get the number of children for a VectorType (i.e., a type declared with a
vector_size/ext_vector_typeattribute) LLDB previously did following calculation:getTypeInfo).unsigned char vec[16]as afloat32[]).numChildren = containerSize / reinterpretedElementSizeHowever, for step 1, clang will return us the aligned container byte-size.
So for a type such as
float __attribute__((ext_vector_type(3)))(which is an array of 3 4-byte floats), clang will round up the byte-width of the array to16.(see
here)
This means that for vectors where the size isn't a power-of-2, LLDB will miscalculate the number of elements.
Solution
This patch changes step 1 such that we calculate the container size as
numElementsInSource * byteSizeOfElement.(cherry picked from commit 0dfcfb5)