On Wed, 3 Apr 2019, Richard Biener wrote: > > 1) Is there some reason to align vectors on the same boundary > > as their size no matter how big it is? I can't find such > > a requirement in the ABIs I looked at. Or would it be more > > appropriate to align the big ones on the preferred boundary > > for the target? For instance, does it make more sense to > > align a 64KB vector on a 64KB boundary than on, say, > > a 64-byte boundary (or some other boundary less than 64K?) > > I don't think there's a good reason. Instead I think that > BIGGEST_ALIGNMENT is what we should go for as upper limit, > anything bigger doesn't make sense (unless the user explicitely > requests it).
It's plausible that you'd want the ABI for a given vector type not to depend on which architecture set extensions are enabled, but those extensions might affect BIGGEST_ALIGNMENT (or the largest alignment meaningful for any instruction, which is not necessarily the same as BIGGEST_ALIGNMENT; Arm has some vector instructions that can use alignments larger than BIGGEST_ALIGNMENT, for example). -- Joseph S. Myers jos...@codesourcery.com
