bug#43725: 28.0.50; Include feature/native-comp into master

[Eli Zaretskii]

> From: Andrea Corallo <akrl@sdf.org>
> Cc: bug-gnu-emacs@gnu.org, larsi@gnus.org, monnier@iro.umontreal.ca,
>         43725@debbugs.gnu.org
> Date: Fri, 19 Feb 2021 11:13:14 +0000
> 
> >   #if EMACS_INT_MAX > LONG_MAX
> >     return emit_rvalue_from_unsigned_long_long (...
> >   #else
> >     return gcc_jit_context_new_rvalue_from_long (...
> >   #endif
> >
> > Does that work well?
> 
> Unfortunately this is a compile time (for the native compiler)
> decision.  If val fits into a long we want to emit simply that.

OK, then how about my original proposal, viz.:

  if (EMACS_INT_MAX > LONG_MAX)
    {
      if (val > LONG_MAX || val < LONG_MIN)
        ...
      else
        ...
    }

You could also #ifdef this conditioned on WINDOWSNT, since MS-Windows
is the only platform where this matters.

> At this point I'm starting to think that the original formulation is
> probably the lesser of evils.

Believe me, it isn't.  For starters, it is not clear what it does.

> 'emit_rvalue_from_unsigned_long_long' was added by me as libgccjit so
> far has no long long support.  As this is shifting the numeric argument
> to emit the code that re-create the long long equivalent using an
> unsigned was the natural choice to avoid UB.
> 
> Admittedly we could just cast inside
> 'emit_rvalue_from_unsigned_long_long' and rename it into
> 'emit_rvalue_from_long_long' but I'm not sure is that important.

Either that, or some comment would be good enough.

Thanks.