Re: [13/n] Allow mixed vector sizes within a single vectorised stmt

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

On Fri, Oct 25, 2019 at 2:49 PM Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> Although a previous patch allowed mixed vector sizes within a vector
> region, we generally still required equal vector sizes within a vector
> stmt.  Specifically, vect_get_vector_types_for_stmt computes two vector
> types: the vector type corresponding to STMT_VINFO_VECTYPE and the
> vector type that determines the minimum vectorisation factor for the
> stmt ("nunits_vectype").  It then required these two types to be
> the same size.
>
> There doesn't seem to be any need for that restriction though.  AFAICT,
> all vectorizable_* functions either do their own compatibility checks
> or don't need to do them (because gimple guarantees that the scalar
> types are compatible).
>
> It should always be the case that nunits_vectype has at least as many
> elements as the other vectype, but that's something we can assert for.
>
> I couldn't resist a couple of other tweaks while there:
>
> - there's no need to compute nunits_vectype if its element type is
>   the same as STMT_VINFO_VECTYPE's.
>
> - it's useful to distinguish the nunits_vectype from the main vectype
>   in dump messages
>
> - when reusing the existing STMT_VINFO_VECTYPE, it's useful to say so
>   in the dump, and say what the type is

OK.

Thanks,
Richard.

>
> 2019-10-24  Richard Sandiford  <richard.sandiford@arm.com>
>
> gcc/
>         * tree-vect-stmts.c (vect_get_vector_types_for_stmt): Don't
>         require vectype and nunits_vectype to have the same size;
>         instead assert that nunits_vectype has at least as many
>         elements as vectype.  Don't compute a separate nunits_vectype
>         if the scalar type is obviously the same as vectype's.
>         Tweak dump messages.
>
> Index: gcc/tree-vect-stmts.c
> ===================================================================
> --- gcc/tree-vect-stmts.c       2019-10-25 13:27:26.205687511 +0100
> +++ gcc/tree-vect-stmts.c       2019-10-25 13:27:32.877640367 +0100
> @@ -11973,7 +11973,12 @@ vect_get_vector_types_for_stmt (stmt_vec
>    tree vectype;
>    tree scalar_type = NULL_TREE;
>    if (STMT_VINFO_VECTYPE (stmt_info))
> -    *stmt_vectype_out = vectype = STMT_VINFO_VECTYPE (stmt_info);
> +    {
> +      *stmt_vectype_out = vectype = STMT_VINFO_VECTYPE (stmt_info);
> +      if (dump_enabled_p ())
> +       dump_printf_loc (MSG_NOTE, vect_location,
> +                        "precomputed vectype: %T\n", vectype);
> +    }
>    else
>      {
>        gcc_assert (!STMT_VINFO_DATA_REF (stmt_info));
> @@ -12005,7 +12010,7 @@ vect_get_vector_types_for_stmt (stmt_vec
>
>        if (dump_enabled_p ())
>         dump_printf_loc (MSG_NOTE, vect_location,
> -                        "get vectype for scalar type:  %T\n", scalar_type);
> +                        "get vectype for scalar type: %T\n", scalar_type);
>        vectype = get_vectype_for_scalar_type (vinfo, scalar_type);
>        if (!vectype)
>         return opt_result::failure_at (stmt,
> @@ -12022,42 +12027,38 @@ vect_get_vector_types_for_stmt (stmt_vec
>
>    /* Don't try to compute scalar types if the stmt produces a boolean
>       vector; use the existing vector type instead.  */
> -  tree nunits_vectype;
> -  if (VECTOR_BOOLEAN_TYPE_P (vectype))
> -    nunits_vectype = vectype;
> -  else
> +  tree nunits_vectype = vectype;
> +  if (!VECTOR_BOOLEAN_TYPE_P (vectype)
> +      && *stmt_vectype_out != boolean_type_node)
>      {
>        /* The number of units is set according to the smallest scalar
>          type (or the largest vector size, but we only support one
>          vector size per vectorization).  */
> -      if (*stmt_vectype_out != boolean_type_node)
> +      HOST_WIDE_INT dummy;
> +      scalar_type = vect_get_smallest_scalar_type (stmt_info, &dummy, &dummy);
> +      if (scalar_type != TREE_TYPE (vectype))
>         {
> -         HOST_WIDE_INT dummy;
> -         scalar_type = vect_get_smallest_scalar_type (stmt_info,
> -                                                      &dummy, &dummy);
> +         if (dump_enabled_p ())
> +           dump_printf_loc (MSG_NOTE, vect_location,
> +                            "get vectype for smallest scalar type: %T\n",
> +                            scalar_type);
> +         nunits_vectype = get_vectype_for_scalar_type (vinfo, scalar_type);
> +         if (!nunits_vectype)
> +           return opt_result::failure_at
> +             (stmt, "not vectorized: unsupported data-type %T\n",
> +              scalar_type);
> +         if (dump_enabled_p ())
> +           dump_printf_loc (MSG_NOTE, vect_location, "nunits vectype: %T\n",
> +                            nunits_vectype);
>         }
> -      if (dump_enabled_p ())
> -       dump_printf_loc (MSG_NOTE, vect_location,
> -                        "get vectype for scalar type:  %T\n", scalar_type);
> -      nunits_vectype = get_vectype_for_scalar_type (vinfo, scalar_type);
>      }
> -  if (!nunits_vectype)
> -    return opt_result::failure_at (stmt,
> -                                  "not vectorized: unsupported data-type %T\n",
> -                                  scalar_type);
> -
> -  if (maybe_ne (GET_MODE_SIZE (TYPE_MODE (vectype)),
> -               GET_MODE_SIZE (TYPE_MODE (nunits_vectype))))
> -    return opt_result::failure_at (stmt,
> -                                  "not vectorized: different sized vector "
> -                                  "types in statement, %T and %T\n",
> -                                  vectype, nunits_vectype);
> +
> +  gcc_assert (*stmt_vectype_out == boolean_type_node
> +             || multiple_p (TYPE_VECTOR_SUBPARTS (nunits_vectype),
> +                            TYPE_VECTOR_SUBPARTS (*stmt_vectype_out)));
>
>    if (dump_enabled_p ())
>      {
> -      dump_printf_loc (MSG_NOTE, vect_location, "vectype: %T\n",
> -                      nunits_vectype);
> -
>        dump_printf_loc (MSG_NOTE, vect_location, "nunits = ");
>        dump_dec (MSG_NOTE, TYPE_VECTOR_SUBPARTS (nunits_vectype));
>        dump_printf (MSG_NOTE, "\n");