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

[Rafael Espíndola]

>> Luqman, would you be ok with adding a split_stack attribute instead?
>
> To clarify, that is remove the EnableSegmentedStacks option and
> instead have a per-fn split_stack attribute?

Correct. The advantage is that then LTO of a file using split stacks
(say rust) and one without (C++) will just work.

Cheers,
Rafael