[PATCH] RISC-V: Control fence.i and csr instructions by zifencei and zicsr.

[Jim Wilson]

On Wed, Dec 2, 2020 at 6:27 PM Nelson Chu <nelson.chu@sifive.com> wrote:

> +    case INSN_CLASS_I_AND_ZICSR:
> +      return (riscv_subset_supports ("i")
> +             && riscv_subset_supports ("zicsr"));
> +    case INSN_CLASS_I_AND_ZIFENCEI:
> +      return (riscv_subset_supports ("i")
> +             && riscv_subset_supports ("zifencei"));
>

Do we really need the 'i' check here?  I don't think that either zicsr or
zifencei requires the 'i' extension.  I don't see anything in the unpriv
spec about that.  'i' is just the category that the extension has been
placed into.  zba doesn't require the B extension for instance.  If we do
need the 'i' extension, maybe we should check that during parsing, once,
instead of everytime we see an instruction in that group.  But I think the
check is unnecessary.  If we drop the 'i' check, then we can delete 6
characters from the insn class name, which will make the riscv-opc.c file
look nicer.

Otherwise this all looks OK to me.

Jim