Re: [PATCH v8 02/10] target/riscv: handle vstart >= vl in vext_set_tail_elems_1s()

[Richard Henderson]

On 3/8/24 11:53, Daniel Henrique Barboza wrote:
> +static void vext_set_tail_elems_1s(CPURISCVState *env, void *vd,
> +                                   uint32_t desc, uint32_t esz,
> +                                   uint32_t max_elems)
>   {
>       uint32_t vta = vext_vta(desc);
> +    uint32_t nf = vext_nf(desc);
>       int k;
>   
> -    if (vta == 0) {
> +    /*
> +     * Section 5.4 of the RVV spec mentions:
> +     * "When vstart ≥ vl, there are no body elements, and no
> +     *  elements are updated in any destination vector register
> +     *  group, including that no tail elements are updated
> +     *  with agnostic values."
> +     */
> +    if (vta == 0 || env->vstart >= env->vl) {
>           return;
>       }

This isn't going to work for ...

> @@ -222,9 +230,8 @@ vext_ldst_stride(void *vd, void *v0, target_ulong base,
>               k++;
>           }
>       }
> +    vext_set_tail_elems_1s(env, vd, desc, esz, max_elems);
>       env->vstart = 0;

... ldst, because we also need to increment vstart in the load loop, for consumption by 
the exception path.

You'll need to structure the helper as

    if (vstart >= vl) {
       vstart = 0;
       return;
    }
    for (i = vstart; i < vl; vstart = ++i) {
        ...
    }
    set_tail_elems(...);
    vstart = 0;


r~