target/6882: [SPARC] Useless stack adjustment code

[Eric Botcazou]

> No, it seems a valid optimization request to not emit the
> stack-adjustment code.  Could you find a *specific* reason for
> the stack-adjustment code?  (Please state that in the PR.)

No, I don't see a "specific" reason. But:
- functions from the same translation unit that call it (and that appear 
after it in normal mode, but the restriction is lifted with 
-funit-at-a-time) don't actually emit the call,
- would the benefit be worth it in real life, given that the costly operation 
is to call the function itself (for nothing)? I think the real optimization 
is not to emit the call at all.

-- 
Eric Botcazou