On Fri, Jul 12, 2024 at 02:56:53PM +0200, Richard Biener wrote:
> Padding is only an issue for very small vectors - the obvious choice is
> to disallow vector types that would require any padding. I can hardly
> see where those are faster than using a vector of up to 4 char elements.
> Problematic are 1-bit elements with 4, 2 or one element vectors, 2-bit
> elements
> with 2 or one element vectors and 4-bit elements with 1 element vectors.
I'd really like to avoid having to support something like
_BitInt(16372) __attribute__((vector_size (sizeof (_BitInt(16372)) * 16)))
_BitInt(2) to say size of long long could be acceptable.
> I have no idea what the stance of supporting _BitInt in C++ are,
> but most certainly diverging support (or even semantics) of the
> vector extension in C vs. C++ is undesirable.
I believe Clang supports it in C++ next to C, GCC doesn't and Jason didn't
look favorably to _BitInt support in C++, so at least until something like
that is standardized in C++ the answer is probably no.
Jakub
