[PATCH 1/9] RISC-V: Add 'H' to canonical extension ordering

[Palmer Dabbelt]

On Thu, 02 Jun 2022 07:05:58 PDT (-0700), binutils@sourceware.org wrote:
> This commit adds 'H' to canonical extension ordering based on current
> consensus (not officially ratified as a new ISA specification manual
> but discussion for software compatibility is made).
>
> bfd/ChangeLog
>
> 	* elfxx-riscv.c (riscv_ext_canonical_order): Add 'H' for
> 	canonical extension ordering based on current consensus.
> ---
>  bfd/elfxx-riscv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
> index 92ad03feea0..5c2c616a760 100644
> --- a/bfd/elfxx-riscv.c
> +++ b/bfd/elfxx-riscv.c
> @@ -1345,7 +1345,7 @@ riscv_recognized_prefixed_ext (const char *ext)
>  }
>
>  /* Canonical order for single letter extensions.  */
> -static const char riscv_ext_canonical_order[] = "eigmafdqlcbkjtpvn";
> +static const char riscv_ext_canonical_order[] = "eigmafdqlcbkjtpvnh";
>
>  /* Array is used to compare the orders of standard extensions quickly.  */
>  static int riscv_ext_order[26] = {0};

I forget if this came up elsewhere, but it just did in Linux land.  
Essenitally we added the hypervisor CSRs/instructions to the base ISA 
under the assumption that the lack of a letter meant they were in 
there, but now that there's a letter it's unclear what we should do.  
Probably we should do the same thing for H that we do for the other ones 
in flight right now, though.