frasercrmck wrote:
> > > I'm not sure why we would ever want the current default if this is an
> > > option. I'm trying to see it, but I can't work out a case where a 64bit
> > > pointer would make sense, since the even tens-of-thousands of money
> > > supercomputer cards have less than 256KiB of addressable shared memory.
> > > It might be a bit of an intrusive change (albeit a relatively mechanical
> > > one), but until we see a GPU come to market that has >4GiB addressable
> > > shared memory, I think we should use the "short pointer" datalayout as
> > > default
> >
> >
> > It also applies to constant and private / local address spaces. I don't
> > think those hit 4 GiB yet but it's more feasible than shared. Making
> > address space 3 32-bit by default would make sense to me.
>
> I was also considering separating out address space 3 into its own option,
> yep. At that point I suppose you might as well split out the remaining two,
> and have `-fcuda-short-ptr` alias the three of them.
@jhuber6 do you have any thoughts on how we'd best split up `-fcuda-short-ptr`?
I was initially thinking of `-f[no-]cuda-short-ptr={shared,local,const}` and
have the old `-f[no-]cuda-short-ptr` alias "all". However, it seems like this
sort of (bitfield toggling on//off) option isn't supported by clang's automated
marshalling, and the documented advice is to reconsider the option, rather than
do custom marshalling.
It seems as though a comma-joined operation is best marshalled as a list of
strings, but having the corresponding "no-" case is pretty rare, and would
undoubtedly add extra code and complicate things when trying to tie it in with
the old option format.
Maybe we don't need `-fno-cuda-short-ptr=...`, which I think would simplify
things here. Of course, I might be thinking about this all wrong, and the
frontend and cc1 options could be split up somehow.
https://github.com/llvm/llvm-project/pull/111682
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