Re: [PATCH 2/3] RISC-V: Stricter underscore handling for ISA

[Kito Cheng <kito.cheng@gmail.com>]

Just for reference:

For RISC-V GCC, you can use any number of underscores as you can, so
-march=rv64i___m____a_____c_ is valid input for GCC.
For RISC-V LLVM, you can use only one underscore and have trailing
underscore, e.g. -march=rv64i_mac_

On Fri, Feb 25, 2022 at 5:23 PM Nelson Chu <nelson.chu@sifive.com> wrote:
>
> On Wed, Feb 23, 2022 at 9:49 AM Tsukasa OI via Binutils
> <binutils@sourceware.org> wrote:
> >
> > Double underscores and trailing underscore in an ISA string are invalid.
>
> The ISA spec does say that "Extensions with the Z prefix must be
> separated from other multi-letter extensions by an underscore".  But I
> am not sure if we need the stricter underscore checking for now.  The
> discussion [1] said that we can set the ISA string in any order, so I
> think the checks will be more and more user friendly.  I know that
> these are two different questions, and I don't have a strong opinion.
> Maybe see if anyone else has any suggestions.
>
> Thanks
> Nelson
>
> [1] https://github.com/riscv-non-isa/riscv-toolchain-conventions/pull/14
>
> > bfd/ChangeLog:
> >
> >         * elfxx-riscv.c (riscv_parse_std_ext): Make handling for
> >         underscores in ISA string more strict.
> >         (riscv_parse_prefixed_ext): Likewise.
> > ---
> >  bfd/elfxx-riscv.c | 25 ++++++++++++++++++++++++-
> >  1 file changed, 24 insertions(+), 1 deletion(-)
> >
> > diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
> > index 329dcaed304..ee4b442ba89 100644
> > --- a/bfd/elfxx-riscv.c
> > +++ b/bfd/elfxx-riscv.c
> > @@ -1650,6 +1650,8 @@ riscv_parse_std_ext (riscv_parse_subset_t *rps,
> >                      const char *arch,
> >                      const char *p)
> >  {
> > +  unsigned char underscores = 0;
> > +
> >    /* First letter must start with i, e or g.  */
> >    if (*p != 'e' && *p != 'i' && *p != 'g')
> >      {
> > @@ -1669,8 +1671,15 @@ riscv_parse_std_ext (riscv_parse_subset_t *rps,
> >        if (*p == '_')
> >         {
> >           p++;
> > +         if (++underscores == 2)
> > +           {
> > +             rps->error_handler
> > +               (_("%s: double underscores"), arch);
> > +             return NULL;
> > +           }
> >           continue;
> >         }
> > +      underscores = 0;
> >
> >        bool implicit = false;
> >        int major = RISCV_UNKNOWN_VERSION;
> > @@ -1709,7 +1718,7 @@ riscv_parse_std_ext (riscv_parse_subset_t *rps,
> >        riscv_parse_add_subset (rps, subset, major, minor, implicit);
> >      }
> >
> > -  return p;
> > +  return p - underscores;
> >  }
> >
> >  /* Parsing function for prefixed extensions.
> > @@ -1731,14 +1740,22 @@ riscv_parse_prefixed_ext (riscv_parse_subset_t *rps,
> >    int minor_version;
> >    const char *last_name;
> >    enum riscv_prefix_ext_class class;
> > +  unsigned char underscores = 0;
> >
> >    while (*p)
> >      {
> >        if (*p == '_')
> >         {
> >           p++;
> > +         if (++underscores == 2)
> > +           {
> > +             rps->error_handler
> > +               (_("%s: double underscores"), arch);
> > +             return NULL;
> > +           }
> >           continue;
> >         }
> > +      underscores = 0;
> >
> >        class = riscv_get_prefix_class (p);
> >        if (class == RV_ISA_CLASS_UNKNOWN)
> > @@ -1843,6 +1860,12 @@ riscv_parse_prefixed_ext (riscv_parse_subset_t *rps,
> >         }
> >      }
> >
> > +  if (underscores)
> > +    {
> > +      rps->error_handler
> > +       (_("%s: trailing underscore"), arch);
> > +      return NULL;
> > +    }
> >    return p;
> >  }
> >
> > --
> > 2.32.0
> >