Re: [RFC PATCH 0/1] RISC-V: Imply 'Zicsr' from privileged extensions with CSRs

[Nelson Chu <nelson@rivosinc.com>]

On Sat, Oct 8, 2022 at 12:32 PM Tsukasa OI <research_trasio@irq.a4lg.com> wrote:
>
> Hello,
>
> 'H', 'Smstateen', 'Sscofpmf' and 'Sstc' are four privileged extensions with
> their CSR definitions and 'Smepmp' is a privileged extension with additional
> CSR bits.
>
> Volume II: Privileged Architecture of the RISC-V ISA Manual states that the
> privileged architecture requires the 'Zicsr' extension.

Looking at the privileged spec, makes sense.
https://github.com/riscv/riscv-isa-manual/blob/draft-20221004-28b46de/src/priv-csrs.tex#L9

> However, current
> GNU Binutils has no direct way whether the program has dependency to the
> privileged architecture itself.

Yeah, and we won't have one in the future.  I had heard last time that
the privileged spec should be covered by lots of extensions, F, H, Ss,
Sm, ....

> As a workaround, we could add implications from privileged extensions that
> either add new CSRs, extend existing CSRs or depends on using CSRs.

After seeing the spec, I believe this should be the right way to do
rather than a workaround :-)  Besides, your previous patch, adding
implicit zicsr for v and zkr, should also be the right way to do it
because i no longer implies zicsr since 2.1.  Of course, it is best to
have the rvv and k spec written that they need zicsr, but now I think
keeping the same rule as others (extensions of privileged spec) is
better.

Thanks, so please commit.
Nelson

> This patchset adds such implications for existing privileged extensions that
> satisfy this condition.
>
> I would like to hear your thoughts.
>
>
> Thanks,
> Tsukasa
>
>
>
>
> Tsukasa OI (1):
>   RISC-V: Imply 'Zicsr' from privileged extensions with CSRs
>
>  bfd/elfxx-riscv.c                       | 5 +++++
>  gas/testsuite/gas/riscv/march-imply-h.d | 6 ++++++
>  2 files changed, 11 insertions(+)
>  create mode 100644 gas/testsuite/gas/riscv/march-imply-h.d
>
>
> base-commit: 4cbfd0daabd68516651ee37a19d0e24ca4789ea3
> --
> 2.34.1
>