Re: [PATCH v5 11/19] target/riscv/cpu: add misa_ext_info_arr[]

[Philippe Mathieu-Daudé]

On 27/6/23 18:31, Daniel Henrique Barboza wrote:
> Next patch will add KVM specific user properties for both MISA and
> multi-letter extensions. For MISA extensions we want to make use of what
> is already available in misa_ext_cfgs[] to avoid code repetition.
>
> misa_ext_info_arr[] array will hold name and description for each MISA
> extension that misa_ext_cfgs[] is declaring. We'll then use this new
> array in KVM code to avoid duplicating strings.
>
> There's nothing holding us back from doing the same with multi-letter
> extensions. For now doing just with MISA extensions is enough.
>
> Suggested-by: Andrew Jones <ajones@ventanamicro.com>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> ---
>   target/riscv/cpu.c | 60 ++++++++++++++++++++++++++--------------------
>   target/riscv/cpu.h | 11 ++++++++-
>   2 files changed, 44 insertions(+), 27 deletions(-)


> +const MISAExtInfo misa_ext_info_arr[] = {
> +    [RVA] = {"a", "Atomic instructions"},
> +    [RVC] = {"c", "Compressed instructions"},
> +    [RVD] = {"d", "Double-precision float point"},
> +    [RVF] = {"f", "Single-precision float point"},
> +    [RVI] = {"i", "Base integer instruction set"},
> +    [RVE] = {"e", "Base integer instruction set (embedded)"},
> +    [RVM] = {"m", "Integer multiplication and division"},
> +    [RVS] = {"s", "Supervisor-level instructions"},
> +    [RVU] = {"u", "User-level instructions"},
> +    [RVH] = {"h", "Hypervisor"},
> +    [RVJ] = {"x-j", "Dynamic translated languages"},
> +    [RVV] = {"v", "Vector operations"},
> +    [RVG] = {"g", "General purpose (IMAFD_Zicsr_Zifencei)"},
> +};

Personally I prefer using a getter() helper because we can check in
a single place for empty entries in the array.

IIUC this 13-entries array takes 4MiB (RVV is '1<<21' = 2MiB).

Wouldn't it be clever to index by [a-z]? Except "x-j"...