Re: [01/13] Add a qimode_for_vec_perm helper function

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

On Sun, Dec 10, 2017 at 12:08 AM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> The vec_perm code falls back to doing byte-level permutes if
> element-level permutes aren't supported.  There were two copies
> of the code to calculate the mode, and later patches add another,
> so this patch splits it out into a helper function.
>

Ok.

> 2017-12-09  Richard Sandiford  <richard.sandiford@linaro.org>
>
> gcc/
>         * optabs-query.h (qimode_for_vec_perm): Declare.
>         * optabs-query.c (can_vec_perm_p): Split out qimode search to...
>         (qimode_for_vec_perm): ...this new function.
>         * optabs.c (expand_vec_perm): Use qimode_for_vec_perm.
>
> Index: gcc/optabs-query.h
> ===================================================================
> --- gcc/optabs-query.h  2017-12-09 22:47:12.476364764 +0000
> +++ gcc/optabs-query.h  2017-12-09 22:47:14.730310076 +0000
> @@ -174,6 +174,7 @@ enum insn_code can_extend_p (machine_mod
>  enum insn_code can_float_p (machine_mode, machine_mode, int);
>  enum insn_code can_fix_p (machine_mode, machine_mode, int, bool *);
>  bool can_conditionally_move_p (machine_mode mode);
> +opt_machine_mode qimode_for_vec_perm (machine_mode);
>  bool can_vec_perm_p (machine_mode, bool, vec_perm_indices *);
>  /* Find a widening optab even if it doesn't widen as much as we want.  */
>  #define find_widening_optab_handler(A, B, C) \
> Index: gcc/optabs-query.c
> ===================================================================
> --- gcc/optabs-query.c  2017-12-09 22:47:12.476364764 +0000
> +++ gcc/optabs-query.c  2017-12-09 22:47:14.729310075 +0000
> @@ -345,6 +345,22 @@ can_conditionally_move_p (machine_mode m
>    return direct_optab_handler (movcc_optab, mode) != CODE_FOR_nothing;
>  }
>
> +/* If a target doesn't implement a permute on a vector with multibyte
> +   elements, we can try to do the same permute on byte elements.
> +   If this makes sense for vector mode MODE then return the appropriate
> +   byte vector mode.  */
> +
> +opt_machine_mode
> +qimode_for_vec_perm (machine_mode mode)
> +{
> +  machine_mode qimode;
> +  if (GET_MODE_INNER (mode) != QImode
> +      && mode_for_vector (QImode, GET_MODE_SIZE (mode)).exists (&qimode)
> +      && VECTOR_MODE_P (qimode))
> +    return qimode;
> +  return opt_machine_mode ();
> +}
> +
>  /* Return true if VEC_PERM_EXPR of arbitrary input vectors can be
>     expanded using SIMD extensions of the CPU.  SEL may be NULL, which
>     stands for an unknown constant.  Note that additional permutations
> @@ -375,9 +391,7 @@ can_vec_perm_p (machine_mode mode, bool
>      return true;
>
>    /* We allow fallback to a QI vector mode, and adjust the mask.  */
> -  if (GET_MODE_INNER (mode) == QImode
> -      || !mode_for_vector (QImode, GET_MODE_SIZE (mode)).exists (&qimode)
> -      || !VECTOR_MODE_P (qimode))
> +  if (!qimode_for_vec_perm (mode).exists (&qimode))
>      return false;
>
>    /* ??? For completeness, we ought to check the QImode version of
> Index: gcc/optabs.c
> ===================================================================
> --- gcc/optabs.c        2017-12-09 22:47:12.476364764 +0000
> +++ gcc/optabs.c        2017-12-09 22:47:14.731310077 +0000
> @@ -5452,9 +5452,7 @@ expand_vec_perm (machine_mode mode, rtx
>
>    /* Set QIMODE to a different vector mode with byte elements.
>       If no such mode, or if MODE already has byte elements, use VOIDmode.  */
> -  if (GET_MODE_INNER (mode) == QImode
> -      || !mode_for_vector (QImode, w).exists (&qimode)
> -      || !VECTOR_MODE_P (qimode))
> +  if (!qimode_for_vec_perm (mode).exists (&qimode))
>      qimode = VOIDmode;
>
>    /* If the input is a constant, expand it specially.  */