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

[Nelson Chu <nelson.chu@sifive.com>]

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
>