[Bug target/77882] [Aarch64] Add 'naked' function attribute

["christophe.monat at st dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77882

--- Comment #3 from Christophe Monat <christophe.monat at st dot com> ---
Andrew,

(In reply to Andrew Pinski from comment #2)
> I really think the naked attribute as not useful at all. I think it was a
> bad idea. Why not write a .s file which does what you want?

Well, from the discussions I read (for instance in bug #25967) before posting
this, I was more or less expecting this remark. I agree that some arguments
there are not valid.

In a nutshell, I wrote quite a lot of tricky testing code (dealing manually
with functions prologues/epilogues, etc..) for the ARM target (Ramana : please
pardon the misused 'legacy' adjective) using this feature, and I would like to
have a similar installment for ARM64.

I am also generally simply bothered at the idea of putting decoration at the
beginning of an assembly file, and starting from .c enables me to have the
appropriate tags automatically emitted when I switch from target to target.
--C