Re: [PATCH v3 08/13] target/riscv/vector_helper.c: use vlenb in HELPER(vsetvl)

[Alistair Francis]

On Wed, Jan 17, 2024 at 7:02 AM Daniel Henrique Barboza
<dbarb...@ventanamicro.com> wrote:
>
> Use the new 'vlenb' CPU config to validate fractional LMUL. The original
> comparison is done with 'vlen' and 'sew', both in bits. Adjust the shift
> to use vlenb.
>
> Signed-off-by: Daniel Henrique Barboza <dbarb...@ventanamicro.com>
> Reviewed-by: Richard Henderson <richard.hender...@linaro.org>

Reviewed-by: Alistair Francis <alistair.fran...@wdc.com>

Alistair

> ---
>  target/riscv/vector_helper.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/vector_helper.c b/target/riscv/vector_helper.c
> index cb944229b0..b13be1541a 100644
> --- a/target/riscv/vector_helper.c
> +++ b/target/riscv/vector_helper.c
> @@ -45,9 +45,16 @@ target_ulong HELPER(vsetvl)(CPURISCVState *env, 
> target_ulong s1,
>                                              xlen - 1 - 
> R_VTYPE_RESERVED_SHIFT);
>
>      if (lmul & 4) {
> -        /* Fractional LMUL - check LMUL * VLEN >= SEW */
> +        /*
> +         * Fractional LMUL, check:
> +         *
> +         * VLEN * LMUL >= SEW
> +         * VLEN >> (8 - lmul) >= sew
> +         * (vlenb << 3) >> (8 - lmul) >= sew
> +         * vlenb >> (8 - 3 - lmul) >= sew
> +         */
>          if (lmul == 4 ||
> -            cpu->cfg.vlen >> (8 - lmul) < sew) {
> +            cpu->cfg.vlenb >> (8 - 3 - lmul) < sew) {
>              vill = true;
>          }
>      }
> --
> 2.43.0
>
>