[Bug target/115713] rs6000: Miss warning for incompatible no-altivec and vsx in target attribute

[linkw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115713

--- Comment #3 from Kewen Lin <linkw at gcc dot gnu.org> ---
(In reply to Peter Bergner from comment #2)
> (In reply to Kewen Lin from comment #0)
> > As Peter found in the PR115688, there isn't a warning for:
> > 
> > long __attribute__ ((target ("no-altivec,vsx")))
> > foo (void)
> > {
> >   return 0;
> > }
> > 
> > It's expected to see warning like:
> > 
> > warning: ‘-mvsx’ and ‘-mno-altivec’ are incompatible
> 
> I think Segher and I mentioned in the other bug, that conflicting options
> like this should be an error, rather than a warning.

ah, thanks for noting this, sorry that I missed that part.  I agree that error
sounds better as both are explicitly specified. I thought the reason why it's a
warning is that the whole processing hunk is for warning:

  /* Add some warnings for VSX.  */
  if (TARGET_VSX)
    {
      const char *msg = NULL;
      if (!TARGET_HARD_FLOAT)
        {
          if (rs6000_isa_flags_explicit & OPTION_MASK_VSX)
            msg = N_("%<-mvsx%> requires hardware floating point");
          else
            {
              rs6000_isa_flags &= ~ OPTION_MASK_VSX;
              rs6000_isa_flags_explicit |= OPTION_MASK_VSX;
            }
        }
      else if (TARGET_AVOID_XFORM > 0)
        msg = N_("%<-mvsx%> needs indexed addressing");
      else if (!TARGET_ALTIVEC && (rs6000_isa_flags_explicit
                                   & OPTION_MASK_ALTIVEC))
        {
          if (rs6000_isa_flags_explicit & OPTION_MASK_VSX)
            msg = N_("%<-mvsx%> and %<-mno-altivec%> are incompatible");
          else
            msg = N_("%<-mno-altivec%> disables vsx");
        }

      if (msg)
        {
          warning (0, msg);
          rs6000_isa_flags &= ~ OPTION_MASK_VSX;
          rs6000_isa_flags_explicit |= OPTION_MASK_VSX;
        }
    }

I think we still would like to leave the others as warning, then I'll add one
flag specific in explicit vsx and altivec arm for error.