Re: [PATCH v3 10/13] target/riscv/cpu.h: use 'vlenb' in vext_get_vlmax()

[Alistair Francis]

On Wed, Jan 17, 2024 at 7:02 AM Daniel Henrique Barboza
<dbarb...@ventanamicro.com> wrote:
>
> Rename the existing 'sew' variable to 'vsew' for extra clarity.
>
> Signed-off-by: Daniel Henrique Barboza <dbarb...@ventanamicro.com>

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

Alistair

> ---
>  target/riscv/cpu.h | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 11df226a00..3af61e0f94 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -690,9 +690,16 @@ static inline RISCVMXL riscv_cpu_sxl(CPURISCVState *env)
>   */
>  static inline uint32_t vext_get_vlmax(RISCVCPU *cpu, target_ulong vtype)
>  {
> -    uint8_t sew = FIELD_EX64(vtype, VTYPE, VSEW);
> +    uint8_t vsew = FIELD_EX64(vtype, VTYPE, VSEW);
>      int8_t lmul = sextract32(FIELD_EX64(vtype, VTYPE, VLMUL), 0, 3);
> -    return cpu->cfg.vlen >> (sew + 3 - lmul);
> +    uint32_t vlen = cpu->cfg.vlenb << 3;
> +
> +    /*
> +     * We need to use 'vlen' instead of 'vlenb' to
> +     * preserve the '+ 3' in the formula. Otherwise
> +     * we risk a negative shift if vsew < lmul.
> +     */
> +    return vlen >> (vsew + 3 - lmul);
>  }
>
>  void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
> --
> 2.43.0
>
>