"Richard Guenther" <richard.guent...@gmail.com> writes: > As there is no hardware implementation of AVX available I think > we definitely should stay with 16 for 4.4.
That makes sense. > And IMNSHO also for > all future - __attribute__((aligned)) is part of the ABI, and if it is > not the only user of BIGGEST_ALIGNMENT then BIGGEST_ALIGNMENT > should be properly split between an ABI part and an optimization > related part. I certainly agree that they should be split. However, I don't agree that the value should be fixed for the future, if that is indeed what you are saying. __attribute__ ((aligned)) is very useful for use with portable code. It should correctly reflect the requirements of the processor. That is, there are two conflicting requirements: maintaining a stable ABI on a single platform, and supporting a cross-platform API. I would argue that code which runs on a single platform and needs a stable ABI should avoid __attribute__ ((aligned)). That leaves us with the case of a cross-platform API which wants to present a stable ABI on each platform. (gcc's unwind code could fall into this category, although it's not clear to me that the alignment is actually exposed in a way that it matters.) Is there a way that we can handle that case that is better than simply documenting changes? Ian
