Options of fixing biggest alignment in PR target/38736

[Ian Lance Taylor]

"Richard Guenther" <richard.guenther@gmail.com> writes:

> On Fri, Jan 9, 2009 at 4:31 PM, Ian Lance Taylor <iant@google.com> wrote:
>> "Richard Guenther" <richard.guenther@gmail.com> writes:
>>
>>>> There are many ways to align data without exposing it in the
>>>> ABI--e.g., the alignment of a global array is not part of the ABI, in
>>>> that nothing breaks if the alignment is increased.  Also, there are
>>>> many programs which simply don't care about an external ABI.
>>>
>>> I'd say if programs want to use vectorization they should use
>>> alignof (vector_type) instead of a magic attribute((aligned(max))).
>>
>> It's not that programs explicitly want to use vectorization.  It's
>> that auto-vectorization happens on ordinary scalar types, and programs
>> want to permit that to happen without worrying about the details.
>
> Sure.  The vectorizer increases alignment of variables for this reason.
> But as people cannot adjust their memory allocator behavior they
> cannot use attribute((aligned(max))) for that either.  Or do you suggest
> they should stick that on every decl?  (which is what the autovectorizer
> does)

People can and do adjust their memory allocator.  Doing that in
portable code requires something like attribute((aligned)).

Ian