Re: [PATCH v3 01/13] target/riscv: add 'vlenb' field in cpu->cfg

[Alistair Francis]

On Wed, Jan 17, 2024 at 7:00 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> Our usage of 'vlenb' is overwhelming superior than the use of 'vlen'.
> We're using 'vlenb' most of the time, having to do 'vlen >> 3' or
> 'vlen / 8' in every instance.
>
> In hindsight we would be better if the 'vlenb' property  was introduced
> instead of 'vlen'. That's not what happened, and now we can't easily get
> rid of it due to user scripts all around. What we can do, however, is to
> change our internal representation to use 'vlenb'.
>
> Add a 'vlenb' field in cpu->cfg. It'll be set via the existing 'vlen'
> property, i.e. setting 'vlen' will also set 'vlenb'.
>
> We'll replace all 'vlen >> 3' code to use 'vlenb' directly. Start with
> the single instance we have in target/riscv/cpu.c.
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

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

Alistair

> ---
>  target/riscv/cpu.c     | 4 +++-
>  target/riscv/cpu_cfg.h | 1 +
>  2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 8d3ec74a1c..f4261d2ffc 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -847,7 +847,7 @@ static void riscv_cpu_dump_state(CPUState *cs, FILE *f, 
> int flags)
>                               csr_ops[csrno].name, val);
>              }
>          }
> -        uint16_t vlenb = cpu->cfg.vlen >> 3;
> +        uint16_t vlenb = cpu->cfg.vlenb;
>
>          for (i = 0; i < 32; i++) {
>              qemu_fprintf(f, " %-8s ", riscv_rvv_regnames[i]);
> @@ -1314,6 +1314,7 @@ static void riscv_cpu_init(Object *obj)
>      /* Default values for non-bool cpu properties */
>      cpu->cfg.pmu_mask = MAKE_64BIT_MASK(3, 16);
>      cpu->cfg.vlen = 128;
> +    cpu->cfg.vlenb = 128 >> 3;
>      cpu->cfg.elen = 64;
>      cpu->env.vext_ver = VEXT_VERSION_1_00_0;
>  }
> @@ -1810,6 +1811,7 @@ static void prop_vlen_set(Object *obj, Visitor *v, 
> const char *name,
>
>      cpu_option_add_user_setting(name, value);
>      cpu->cfg.vlen = value;
> +    cpu->cfg.vlenb = value >> 3;
>  }
>
>  static void prop_vlen_get(Object *obj, Visitor *v, const char *name,
> diff --git a/target/riscv/cpu_cfg.h b/target/riscv/cpu_cfg.h
> index fea14c275f..50479dd72f 100644
> --- a/target/riscv/cpu_cfg.h
> +++ b/target/riscv/cpu_cfg.h
> @@ -140,6 +140,7 @@ struct RISCVCPUConfig {
>
>      uint32_t pmu_mask;
>      uint16_t vlen;
> +    uint16_t vlenb;
>      uint16_t elen;
>      uint16_t cbom_blocksize;
>      uint16_t cbop_blocksize;
> --
> 2.43.0
>
>