Re: [PATCH v2] target/riscv: Fix the element agnostic function problem

[Richard Henderson <richard.henderson@linaro.org>]

On 3/20/24 17:58, Huang Tao wrote:
> In RVV and vcrypto instructions, the masked and tail elements are set to 1s
> using vext_set_elems_1s function if the vma/vta bit is set. It is the element
> agnostic policy.
> 
> However, this function can't deal the big endian situation. This patch fixes
> the problem by adding handling of such case.
> 
> Signed-off-by: Huang Tao <eric.huang@linux.alibaba.com>
> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> Changes in v2:
> - Keep the api of vext_set_elems_1s
> - Reduce the number of patches.
> ---
>   target/riscv/vector_internals.c | 22 ++++++++++++++++++++++
>   1 file changed, 22 insertions(+)
> 
> diff --git a/target/riscv/vector_internals.c b/target/riscv/vector_internals.c
> index 12f5964fbb..3e45b9b4a7 100644
> --- a/target/riscv/vector_internals.c
> +++ b/target/riscv/vector_internals.c
> @@ -30,6 +30,28 @@ void vext_set_elems_1s(void *base, uint32_t is_agnostic, uint32_t cnt,
>       if (tot - cnt == 0) {
>           return ;
>       }
> +
> +#if HOST_BIG_ENDIAN
> +    /*
> +     * Deal the situation when the elements are insdie
> +     * only one uint64 block including setting the
> +     * masked-off element.
> +     */
> +    if ((tot - 1) ^ cnt < 8) {
> +        memset(base + H1(tot - 1), -1, tot - cnt);
> +        return;
> +    }

(1) tot will always be a multiple of 8, afaik, so there's no need for this first block.
(2) Using if not #if means that the code is always compile-tested, even if it is eliminated.


r~