Richard Biener <rguent...@suse.de> writes:
> We currently fail to re-CSE SLP nodes after optimizing permutes
> which results in off cost estimates. For gcc.dg/vect/bb-slp-32.c
> this shows in not re-using the SLP node with the load and arithmetic
> for both the store and the reduction. The following implements
> CSE by re-bst-mapping nodes as finalization part of vect_optimize_slp.
>
> I've tried to make the CSE part of permute materialization but it
> isn't a very good fit there. I've not bothered to implement something
> more complete, also handling external defs or defs without
> SLP_TREE_SCALAR_STMTS.
>
> I realize this might result in more BB SLP which in turn might slow
> down code given costing for BB SLP is difficult (even that we now
> vectorize gcc.dg/vect/bb-slp-32.c on x86_64 might be not a good idea).
> This is nevertheless feeding more accurate info to costing which is
> good.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> Does this look OK?
>
> Thanks,
> Richard.
>
> PR tree-optimization/114413
> * tree-vect-slp.cc (release_scalar_stmts_to_slp_tree_map):
> New function, split out from ...
> (vect_analyze_slp): ... here. Call it.
> (vect_cse_slp_nodes): New function.
> (vect_optimize_slp): Call it.
>
> * gcc.dg/vect/bb-slp-32.c: Expect CSE and vectorization on x86.
> ---
> gcc/testsuite/gcc.dg/vect/bb-slp-32.c | 6 +++
> gcc/tree-vect-slp.cc | 77 ++++++++++++++++++++++-----
> 2 files changed, 71 insertions(+), 12 deletions(-)
>
> diff --git a/gcc/testsuite/gcc.dg/vect/bb-slp-32.c
> b/gcc/testsuite/gcc.dg/vect/bb-slp-32.c
> index 4f72727b694..475b241c36e 100644
> --- a/gcc/testsuite/gcc.dg/vect/bb-slp-32.c
> +++ b/gcc/testsuite/gcc.dg/vect/bb-slp-32.c
> @@ -38,3 +38,9 @@ int main()
> abort ();
> return 0;
> }
> +
> +/* This is a weak test but we want to re-use the arithmetic for both the
> + store and the reduction. */
> +/* { dg-final { scan-tree-dump "re-using SLP tree" "slp2" { target {
> x86_64-*-* i?86-*-* } } } } */
> +/* On i386 we vectorize both the store and the reduction. */
> +/* { dg-final { scan-tree-dump-times "basic block part vectorized" 2 "slp2"
> { target { x86_64-*-* i?86-*-* } } } } */
> diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
> index 2552dacbd69..980d1e7267d 100644
> --- a/gcc/tree-vect-slp.cc
> +++ b/gcc/tree-vect-slp.cc
> @@ -1586,6 +1586,23 @@ bst_traits::equal (value_type existing, value_type
> candidate)
> return true;
> }
>
> +typedef hash_map <vec <stmt_vec_info>, slp_tree,
> + simple_hashmap_traits <bst_traits, slp_tree> >
> + scalar_stmts_to_slp_tree_map_t;
> +
> +/* Release BST_MAP. */
> +
> +static void
> +release_scalar_stmts_to_slp_tree_map (scalar_stmts_to_slp_tree_map_t
> *bst_map)
> +{
> + /* The map keeps a reference on SLP nodes built, release that. */
> + for (scalar_stmts_to_slp_tree_map_t::iterator it = bst_map->begin ();
> + it != bst_map->end (); ++it)
> + if ((*it).second)
> + vect_free_slp_tree ((*it).second);
> + delete bst_map;
> +}
> +
> /* ??? This was std::pair<std::pair<tree_code, vect_def_type>, tree>
> but then vec::insert does memmove and that's not compatible with
> std::pair. */
> @@ -1684,10 +1701,6 @@ vect_slp_linearize_chain (vec_info *vinfo,
> }
> }
>
> -typedef hash_map <vec <stmt_vec_info>, slp_tree,
> - simple_hashmap_traits <bst_traits, slp_tree> >
> - scalar_stmts_to_slp_tree_map_t;
> -
> static slp_tree
> vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
> vec<stmt_vec_info> stmts, unsigned int group_size,
> @@ -4308,14 +4321,7 @@ vect_analyze_slp (vec_info *vinfo, unsigned
> max_tree_size)
> }
> }
>
> -
> -
> - /* The map keeps a reference on SLP nodes built, release that. */
> - for (scalar_stmts_to_slp_tree_map_t::iterator it = bst_map->begin ();
> - it != bst_map->end (); ++it)
> - if ((*it).second)
> - vect_free_slp_tree ((*it).second);
> - delete bst_map;
> + release_scalar_stmts_to_slp_tree_map (bst_map);
>
> if (pattern_found && dump_enabled_p ())
> {
> @@ -6373,6 +6379,43 @@ vect_optimize_slp_pass::run ()
> free_graph (m_slpg);
> }
>
> +/* Apply CSE to NODE and its children using BST_MAP. */
> +
> +static void
> +vect_cse_slp_nodes (scalar_stmts_to_slp_tree_map_t *bst_map, slp_tree& node)
> +{
> + if (SLP_TREE_DEF_TYPE (node) == vect_internal_def
> + && SLP_TREE_CODE (node) != VEC_PERM_EXPR
> + /* Besides some VEC_PERM_EXPR, two-operator nodes also
> + lack scalar stmts and thus CSE doesn't work via bst_map. Ideally
> + we'd have sth that works for all internal and external nodes. */
> + && !SLP_TREE_SCALAR_STMTS (node).is_empty ())
> + {
> + if (slp_tree *leader = bst_map->get (SLP_TREE_SCALAR_STMTS (node)))
> + {
> + if (*leader != node)
> + {
> + if (dump_enabled_p ())
> + dump_printf_loc (MSG_NOTE, vect_location,
> + "re-using SLP tree %p for %p\n",
> + (void *)*leader, (void *)node);
> + vect_free_slp_tree (node);
> + (*leader)->refcnt += 1;
> + node = *leader;
> + }
> + return;
> + }
> +
> + bst_map->put (SLP_TREE_SCALAR_STMTS (node).copy (), node);
> + node->refcnt += 1;
Since we're not starting with zeroed refcnts, won't this end up double
counting the references?
> + /* And recurse. */
> + }
> +
> + for (slp_tree &child : SLP_TREE_CHILDREN (node))
> + if (child)
> + vect_cse_slp_nodes (bst_map, child);
> +}
> +
> /* Optimize the SLP graph of VINFO. */
>
> void
> @@ -6381,6 +6424,16 @@ vect_optimize_slp (vec_info *vinfo)
> if (vinfo->slp_instances.is_empty ())
> return;
> vect_optimize_slp_pass (vinfo).run ();
> +
> +
Super minor nit, but: one newline too many :)
LGTM otherwise FWIW.
Thanks,
Richard
> + /* Apply CSE again to nodes after permute optimization. */
> + scalar_stmts_to_slp_tree_map_t *bst_map
> + = new scalar_stmts_to_slp_tree_map_t ();
> +
> + for (auto inst : vinfo->slp_instances)
> + vect_cse_slp_nodes (bst_map, SLP_INSTANCE_TREE (inst));
> +
> + release_scalar_stmts_to_slp_tree_map (bst_map);
> }
>
> /* Gather loads reachable from the individual SLP graph entries. */
