[PATCH] RISC-V: Checking 'm' extension when using RVV.

[Christoph Müllner]

On Tue, Jan 21, 2025 at 4:23 PM Jiawei <jiawei@iscas.ac.cn> wrote:
>
> This patch add a new extension check when using `v` extension, it
> currently should also enable `m` extension to make sure vector length
> caculate correct.

How to trigger this incorrect calculation?
Is there an example?

>
> bfd/ChangeLog:
>
>         * elfxx-riscv.c (riscv_parse_check_conflicts): New check.
>
> gas/ChangeLog:
>
>         * testsuite/gas/riscv/march-fail-rv64i_v.d: New test.
>         * testsuite/gas/riscv/march-fail-rv64i_v.l: New test.
>
> ---
>  bfd/elfxx-riscv.c                            | 10 +++++++++-
>  gas/testsuite/gas/riscv/march-fail-rv64i_v.d |  4 ++++
>  gas/testsuite/gas/riscv/march-fail-rv64i_v.l |  3 +++
>  3 files changed, 16 insertions(+), 1 deletion(-)
>  create mode 100644 gas/testsuite/gas/riscv/march-fail-rv64i_v.d
>  create mode 100644 gas/testsuite/gas/riscv/march-fail-rv64i_v.l
>
> diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
> index c9e4b03b17d..150838d3d24 100644
> --- a/bfd/elfxx-riscv.c
> +++ b/bfd/elfxx-riscv.c
> @@ -2123,7 +2123,15 @@ riscv_parse_check_conflicts (riscv_parse_subset_t *rps)
>         (_("`xtheadvector' is conflict with the `v' extension"));
>        no_conflict = false;
>      }
> -
> +  /* We might use a multiplication to calculate the scalable vector length at
> +     runtime.  Therefore, require the M extension.  */
> +  if (riscv_lookup_subset (rps->subset_list, "v", &subset)
> +      && !riscv_lookup_subset (rps->subset_list, "m", &subset))
> +    {
> +      rps->error_handler
> +       (_("Currently the 'v' implementation requires the 'm' extension"));
> +      no_conflict = false;
> +    }
>    bool support_zve = false;
>    bool support_zvl = false;
>    riscv_subset_t *s = rps->subset_list->head;
> diff --git a/gas/testsuite/gas/riscv/march-fail-rv64i_v.d b/gas/testsuite/gas/riscv/march-fail-rv64i_v.d
> new file mode 100644
> index 00000000000..4d14bb4f9a9
> --- /dev/null
> +++ b/gas/testsuite/gas/riscv/march-fail-rv64i_v.d
> @@ -0,0 +1,4 @@
> +#as: -march=rv64i_v
> +#source: empty.s
> +#error_output: march-fail-rv64i_v.l
> +
> diff --git a/gas/testsuite/gas/riscv/march-fail-rv64i_v.l b/gas/testsuite/gas/riscv/march-fail-rv64i_v.l
> new file mode 100644
> index 00000000000..5386a942ec5
> --- /dev/null
> +++ b/gas/testsuite/gas/riscv/march-fail-rv64i_v.l
> @@ -0,0 +1,3 @@
> +Assembler messages:
> +Error: Currently the 'v' implementation requires the 'm' extension
> +
> --
> 2.43.0
>