[PATCH 06/10] vect: Pass reduc_info to get_initial_defs_for_reduction

[Richard Biener]

On Thu, Jul 8, 2021 at 2:46 PM Richard Sandiford via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This patch passes the reduc_info to get_initial_defs_for_reduction,
> so that the function can get general information from there rather
> than from the first SLP statement.  This isn't a win on its own,
> but it becomes important with later patches.

So the original code should have used SLP_TREE_REPRESENTATIVE
instead of SLP_TREE_SCALAR_STMTS ()[0] (there might have been
issues with doing that - my recollection is weak here).

I'm not sure if reduc_info is actually better - only the representative
will have STMT_VINFO_VECTYPE set, for the reduc_info
there's STMT_VINFO_REDUC_VECTYPE (and STMT_VINFO_REDUC_VECTYPE_IN).

So I think if you want to use reduc_info then you want to use
STMT_VINFO_REDUC_VECTYPE?

> gcc/
>         * tree-vect-loop.c (get_initial_defs_for_reduction): Take the
>         reduc_info as an additional parameter.
>         (vect_transform_cycle_phi): Update accordingly.
> ---
>  gcc/tree-vect-loop.c | 23 ++++++++++-------------
>  1 file changed, 10 insertions(+), 13 deletions(-)
>
> diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
> index a31d7621c3b..565c2859477 100644
> --- a/gcc/tree-vect-loop.c
> +++ b/gcc/tree-vect-loop.c
> @@ -4764,32 +4764,28 @@ get_initial_def_for_reduction (loop_vec_info loop_vinfo,
>    return init_def;
>  }
>
> -/* Get at the initial defs for the reduction PHIs in SLP_NODE.
> -   NUMBER_OF_VECTORS is the number of vector defs to create.
> -   If NEUTRAL_OP is nonnull, introducing extra elements of that
> -   value will not change the result.  */
> +/* Get at the initial defs for the reduction PHIs for REDUC_INFO, whose
> +   associated SLP node is SLP_NODE.  NUMBER_OF_VECTORS is the number of vector
> +   defs to create.  If NEUTRAL_OP is nonnull, introducing extra elements of
> +   that value will not change the result.  */
>
>  static void
>  get_initial_defs_for_reduction (vec_info *vinfo,
> +                               stmt_vec_info reduc_info,
>                                 slp_tree slp_node,
>                                 vec<tree> *vec_oprnds,
>                                 unsigned int number_of_vectors,
>                                 bool reduc_chain, tree neutral_op)
>  {
>    vec<stmt_vec_info> stmts = SLP_TREE_SCALAR_STMTS (slp_node);
> -  stmt_vec_info stmt_vinfo = stmts[0];
>    unsigned HOST_WIDE_INT nunits;
>    unsigned j, number_of_places_left_in_vector;
> -  tree vector_type;
> +  tree vector_type = STMT_VINFO_VECTYPE (reduc_info);
>    unsigned int group_size = stmts.length ();
>    unsigned int i;
>    class loop *loop;
>
> -  vector_type = STMT_VINFO_VECTYPE (stmt_vinfo);
> -
> -  gcc_assert (STMT_VINFO_DEF_TYPE (stmt_vinfo) == vect_reduction_def);
> -
> -  loop = (gimple_bb (stmt_vinfo->stmt))->loop_father;
> +  loop = (gimple_bb (reduc_info->stmt))->loop_father;
>    gcc_assert (loop);
>    edge pe = loop_preheader_edge (loop);
>
> @@ -4823,7 +4819,7 @@ get_initial_defs_for_reduction (vec_info *vinfo,
>      {
>        tree op;
>        i = j % group_size;
> -      stmt_vinfo = stmts[i];
> +      stmt_vec_info stmt_vinfo = stmts[i];
>
>        /* Get the def before the loop.  In reduction chain we have only
>          one initial value.  Else we have as many as PHIs in the group.  */
> @@ -7510,7 +7506,8 @@ vect_transform_cycle_phi (loop_vec_info loop_vinfo,
>               = neutral_op_for_slp_reduction (slp_node, vectype_out,
>                                               STMT_VINFO_REDUC_CODE (reduc_info),
>                                               first != NULL);
> -         get_initial_defs_for_reduction (loop_vinfo, slp_node_instance->reduc_phis,
> +         get_initial_defs_for_reduction (loop_vinfo, reduc_info,
> +                                         slp_node_instance->reduc_phis,
>                                           &vec_initial_defs, vec_num,
>                                           first != NULL, neutral_op);
>         }