Re: [11/13] Use vec_perm_builder::series_p in shift_amt_for_vec_perm_mask

[Richard Biener <richard dot guenther at gmail dot com>]

On Sun, Dec 10, 2017 at 12:24 AM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> This patch makes shift_amt_for_vec_perm_mask use series_p to check
> for the simple case of a natural linear series before falling back
> to testing each element individually.  The series_p test works with
> variable-length vectors but testing every individual element doesn't.

Ok.

Richard.

>
> 2017-12-09  Richard Sandiford  <richard.sandiford@linaro.org>
>
> gcc/
>         * optabs.c (shift_amt_for_vec_perm_mask): Try using series_p
>         before testing each element individually.
>
> Index: gcc/optabs.c
> ===================================================================
> --- gcc/optabs.c        2017-12-09 22:48:52.266015836 +0000
> +++ gcc/optabs.c        2017-12-09 22:48:56.257154317 +0000
> @@ -5375,20 +5375,20 @@ vector_compare_rtx (machine_mode cmp_mod
>  static rtx
>  shift_amt_for_vec_perm_mask (machine_mode mode, const vec_perm_indices &sel)
>  {
> -  unsigned int i, first, nelt = GET_MODE_NUNITS (mode);
> +  unsigned int nelt = GET_MODE_NUNITS (mode);
>    unsigned int bitsize = GET_MODE_UNIT_BITSIZE (mode);
> -
> -  first = sel[0];
> +  unsigned int first = sel[0];
>    if (first >= nelt)
>      return NULL_RTX;
> -  for (i = 1; i < nelt; i++)
> -    {
> -      int idx = sel[i];
> -      unsigned int expected = i + first;
> -      /* Indices into the second vector are all equivalent.  */
> -      if (idx < 0 || (MIN (nelt, (unsigned) idx) != MIN (nelt, expected)))
> -       return NULL_RTX;
> -    }
> +
> +  if (!sel.series_p (0, 1, first, 1))
> +    for (unsigned int i = 1; i < nelt; i++)
> +      {
> +       unsigned int expected = i + first;
> +       /* Indices into the second vector are all equivalent.  */
> +       if (MIN (nelt, sel[i]) != MIN (nelt, expected))
> +         return NULL_RTX;
> +      }
>
>    return GEN_INT (first * bitsize);
>  }