Re: [PATCH 1/2] target/riscv/vector_helper.c: create vext_set_tail_elems_1s()

[Philippe Mathieu-Daudé]

On 26/2/23 18:05, Daniel Henrique Barboza wrote:
> Commit 752614cab8e6 ("target/riscv: rvv: Add tail agnostic for vector
> load / store instructions") added code to set the tail elements to 1 in
> the end of vext_ldst_stride(), vext_ldst_us(), vext_ldst_index() and
> vext_ldff(). Aside from a env->vl versus an evl value being used in the
> first loop, the code is being repeated 4 times.
>
> Create a helper to avoid code repetition in all those functions.
> Arguments that are used in the callers (nf, esz and max_elems) are
> passed as arguments. All other values are being derived inside the
> helper.
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Reviewed-by: Frank Chang <frank.chang@sifive.com>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>   target/riscv/vector_helper.c | 86 +++++++++++++-----------------------
>   1 file changed, 30 insertions(+), 56 deletions(-)


> +static void vext_set_tail_elems_1s(CPURISCVState *env, target_ulong vl,
> +                                   void *vd, uint32_t desc, uint32_t nf,
> +                                   uint32_t esz, uint32_t max_elems)
> +{
> +    uint32_t total_elems = vext_get_total_elems(env, desc, esz);
> +    uint32_t vlenb = env_archcpu(env)->cfg.vlen >> 3;
> +    uint32_t vta = vext_vta(desc);
> +    uint32_t registers_used;
> +    int k;
> +
> +    for (k = 0; k < nf; ++k) {
> +        vext_set_elems_1s(vd, vta, (k * max_elems + vl) * esz,
> +                          (k * max_elems + max_elems) * esz);
> +    }
> +
> +    if (nf * max_elems % total_elems != 0) {
> +        registers_used = ((nf * max_elems) * esz + (vlenb - 1)) / vlenb;
> +        vext_set_elems_1s(vd, vta, (nf * max_elems) * esz,
> +                          registers_used * vlenb);
> +    }

  for (unsigned k = 0; k < nf; ++k) {
      vext_set_elems_1s(vd, vta, (k * max_elems + vl) * esz,
                        (k * max_elems + max_elems) * esz);
  }

  if (nf * max_elems % total_elems != 0) {
      uint32_t cnt = (nf * max_elems) * esz;
      vext_set_elems_1s(vd, vta, cnt, QEMU_ALIGN_UP(cnt, vlenb));
  }

I suspect ROUND_UP() could be used if vlenb is a power of 2.