[PATCH] RISC-V: Support to parse the multi-letter prefix in the architecture string.

[Jim Wilson]

On Wed, Apr 7, 2021 at 2:25 AM Nelson Chu <nelson.chu@sifive.com> wrote:

> I never considered the prefixes may have multiple letters, like zxm.
> But the ISA spec has been updated for a long time that I haven't noticed.
> This patch rewrites the part of architecture parser to support parsing
> the multi-letter prefixes.  Besides, I also improve the parser to report
> errors in details.  One of the most obvious improvement is - Do not parse
> the prefixed extensions according to the orders in the parse_config.
> If we do so, then we used to get "unexpected ISA string at end" errors,
> but the message is a little bit  hard to know what is happening.  I Remove
> the confused message, and let riscv_parse_prefixed_ext to report the
> details.
>

Looks reasonable.  We will need a similar patch for gcc, but we don't need
it now.

Jim