[PATCH] Add a "no-split-stack" function attribute.

[Rafael Espíndola]

>> In summary, your proposal is to replace the EnableSegmentedStacks
>> codegen option with a split_stack attribute?
>
> No, extend it with a RequiredStackSize(size) attribute.

At the IR level that doesn't look all that useful. A pass over the
calls to decide if a caller should allocate stack for the callees
would have to happen really late.

I do like the idea of replacing the option with an attribute, that way
LTO rust and C (for example) would just work.

Also, the semantics that they want for a no_split_stack (or no
attribute if we drop the option) is that the function is only used in
special situations and llvm should not worry about the its callers.

Cheers,
Rafael