rnk added a comment.
It's the typedef alignment changes that are causing problems for us, not the
MaxVectorAlign changes. That makes more sense. The new alignment attribute
breaks our implementation of `_mm256_loadu_ps`, because the packed struct ends
up with a 32-byte alignment. Here's the implementation:
static __inline __m256 __DEFAULT_FN_ATTRS
_mm256_loadu_ps(float const *__p)
{
struct __loadu_ps {
__m256 __v;
} __attribute__((__packed__, __may_alias__));
return ((struct __loadu_ps*)__p)->__v;
}
And clang's -fdump-record-layouts says:
*** Dumping AST Record Layout
0 | struct __loadu_ps
0 | __m256 __v
| [sizeof=32, align=32]
I think the problem is that `__attribute__((aligned(N)))` beats
`__attribute__((packed))` on Windows to match MSVC's behavior with
`__declspec(align(N))`.
I think we should revert this for now. Adding the alignment attribute to all
Intel vector typedefs is a bigger change than it seems.
Repository:
rC Clang
https://reviews.llvm.org/D46042
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