Re: [PATCH v1 2/6] target/loongarch: Add set_vec_extctx to set LSX/LASX instructions extctx_flags

[Richard Henderson]

On 10/9/23 20:36, Song Gao wrote:
> Signed-off-by: Song Gao <gaosong@loongson.cn>
> ---
>   target/loongarch/insn_trans/trans_vec.c.inc | 12 ++++++++++++
>   target/loongarch/internals.h                |  2 ++
>   2 files changed, 14 insertions(+)
>
> diff --git a/target/loongarch/insn_trans/trans_vec.c.inc 
> b/target/loongarch/insn_trans/trans_vec.c.inc
> index 98f856bb29..aef16ef44a 100644
> --- a/target/loongarch/insn_trans/trans_vec.c.inc
> +++ b/target/loongarch/insn_trans/trans_vec.c.inc
> @@ -23,8 +23,20 @@ static bool check_vec(DisasContext *ctx, uint32_t oprsz)
>   
>   #else
>   
> +static void set_vec_extctx(DisasContext *ctx, uint32_t oprsz)
> +{
> +    if (oprsz == 16) {
> +        ctx->extctx_flags |= EXTCTX_FLAGS_LSX;
> +    }
> +
> +    if (oprsz == 32) {
> +        ctx->extctx_flags |= EXTCTX_FLAGS_LASX;
> +    }
> +}
> +
>   static bool check_vec(DisasContext *ctx, uint32_t oprsz)
>   {
> +    set_vec_extctx(ctx, oprsz);
>       return true;
>   }

This doesn't do anything.  Nothing copies the changed value back to env.
Anyway, I think this is the wrong way to go about it.

If you want to track what the program is using, you should do it exactly like the real 
kernel: disable the execution unit, have the program trap, and the enable the execution 
unit when the trap occurs.  At this point, CSR_EUEN enable bits contain exactly which 
units have been used by the program.


r~