From 4b19ff1b5ef684c2d9ccd4fb275aeef0a4b0b980 Mon Sep 17 00:00:00 2001
From: Richard Biener <rguenther@suse.de>
Date: Tue, 7 Feb 2023 14:01:22 +0100
Subject: [PATCH] tree-optimization/26854 - slow bitmap operations
With the compiler.i testcase from the PR one can see bitmap_set_bit
very high in the profile, originating from SSA update and alias
stmt walking. For SSA update mark_block_for_update essentially
performs redundant bitmap_set_bits and is called via
insert_updated_phi_nodes_for as
EXECUTE_IF_SET_IN_BITMAP (pruned_idf, 0, i, bi)
...
mark_block_for_update (bb);
FOR_EACH_EDGE (e, ei, bb->preds)
if (e->src->index >= 0)
mark_block_for_update (e->src);
which is quite random in the access pattern and runs into the
O(n) case of the linked list bitmap representation. Switching
blocks_to_update to tree view around insert_updated_phi_nodes_for
improves SSA update time from
tree SSA incremental : 4.26 ( 3%)
to
tree SSA incremental : 2.98 ( 2%)
Likewise the visited bitmap allocated by the alias walker benefits
from using the tree view in case of large CFGs and we see an
improvement from
alias stmt walking : 10.53 ( 9%)
to
alias stmt walking : 4.05 ( 4%)
PR tree-optimization/26854
* tree-into-ssa.cc (update_ssa): Turn blocks_to_update to tree
view around insert_updated_phi_nodes_for.
* tree-ssa-alias.cc (maybe_skip_until): Allocate visited bitmap
in tree view.
(walk_aliased_vdefs_1): Likewise.
---
gcc/tree-into-ssa.cc | 4 ++++
gcc/tree-ssa-alias.cc | 10 ++++++++--
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/gcc/tree-into-ssa.cc b/gcc/tree-into-ssa.cc
index 067d29698f90..2e3229904565 100644
--- a/gcc/tree-into-ssa.cc
+++ b/gcc/tree-into-ssa.cc
@@ -3561,6 +3561,8 @@ update_ssa (unsigned update_flags)
bitmap_initialize (&dfs[bb->index], &bitmap_default_obstack);
compute_dominance_frontiers (dfs);
+ bitmap_tree_view (blocks_to_update);
+
/* insert_update_phi_nodes_for will call add_new_name_mapping
when inserting new PHI nodes, but it will not add any
new members to OLD_SSA_NAMES. */
@@ -3574,6 +3576,8 @@ update_ssa (unsigned update_flags)
FOR_EACH_VEC_ELT (symbols_to_rename, i, sym)
insert_updated_phi_nodes_for (sym, dfs, update_flags);
+ bitmap_list_view (blocks_to_update);
+
FOR_EACH_BB_FN (bb, cfun)
bitmap_clear (&dfs[bb->index]);
free (dfs);
diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc
index 7089e8b5bf38..81bc51ed4ad8 100644
--- a/gcc/tree-ssa-alias.cc
+++ b/gcc/tree-ssa-alias.cc
@@ -3657,7 +3657,10 @@ maybe_skip_until (gimple *phi, tree &target, basic_block target_bb,
basic_block bb = gimple_bb (phi);
if (!*visited)
- *visited = BITMAP_ALLOC (NULL);
+ {
+ *visited = BITMAP_ALLOC (NULL);
+ bitmap_tree_view (*visited);
+ }
bitmap_set_bit (*visited, SSA_NAME_VERSION (PHI_RESULT (phi)));
@@ -3949,7 +3952,10 @@ walk_aliased_vdefs_1 (ao_ref *ref, tree vdef,
{
unsigned i;
if (!*visited)
- *visited = BITMAP_ALLOC (NULL);
+ {
+ *visited = BITMAP_ALLOC (NULL);
+ bitmap_tree_view (*visited);
+ }
for (i = 0; i < gimple_phi_num_args (def_stmt); ++i)
{
int res = walk_aliased_vdefs_1 (ref,
--
GitLab