[PATCH] nvptx: implement automatic storage in custom stacks

[Alexander Monakov]

On Mon, 30 Nov 2015, Jakub Jelinek wrote:
> Does it really have to be a full multilib?  I mean, the only precondition is
> that something sets up the var, right?  Would the OpenACC folks be willing
> to set it up too?  For stuff like libc, functions that are ECF_LEAF builtins
> IMHO really don't care whether they are built as -msoft-stack or not, they
> shouldn't be passing addresses of local vars to code that could use OpenMP.
> The only question is if say qsort or other functions that call user callbacks
> could be passing addresses of local vars to those callbacks, or whether they
> only pass addresses passed from callers, or addresses of heap objects.

Well, in that full multilib there's also a second option enabled, to handle
atomics/syscalls outside of simd regions, where the cost is additional code in
the prologue, and one "shuffle" instruction after each atomic/syscall.

It doesn't have to be a multilib, but doing it as a multilib is a safe choice
w.r.t OpenACC work.

Alexander