[Bug lto/48200] Implement function attribute for symbol versioning (.symver)

[xry111 at mengyan1223 dot wang]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48200

--- Comment #39 from Xi Ruoyao <xry111 at mengyan1223 dot wang> ---
(In reply to Jan Hubicka from comment #38)

> Internally in GCC the symver is handled just as normal alias only output
> differntly.  I think GCC, just like static linker, does not really need
> to understand the versions because there are no direct ways to bind to
> those symbols.
> 
> I wonder if someone sees limitations to this design (in particular
> attaching the symver directly to the definition). 

I think this design is correct.  "symver" attribute is introduced to "bind" a
symver to a definition.  If they can be seperated LTO will do stupid things.

I prefer "symver" than "version_def".