| /* If-elseif-else to switch conversion pass |
| Copyright (C) 2020-2022 Free Software Foundation, Inc. |
| |
| This file is part of GCC. |
| |
| GCC is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3, or (at your option) |
| any later version. |
| |
| GCC is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GCC; see the file COPYING3. If not see |
| <http://www.gnu.org/licenses/>. */ |
| |
| /* Algorithm of the pass runs in the following steps: |
| a) We walk basic blocks in DOMINATOR order so that we first reach |
| a first condition of a future switch. |
| b) We follow false edges of a if-else-chain and we record chain |
| of GIMPLE conditions. These blocks are only used for comparison |
| of a common SSA_NAME and we do not allow any side effect. |
| c) We remove all basic blocks (except first) of such chain and |
| GIMPLE switch replaces the condition in the first basic block. |
| d) We move all GIMPLE statements in the removed blocks into the |
| first one. */ |
| |
| #include "config.h" |
| #include "system.h" |
| #include "coretypes.h" |
| #include "backend.h" |
| #include "rtl.h" |
| #include "tree.h" |
| #include "gimple.h" |
| #include "tree-pass.h" |
| #include "ssa.h" |
| #include "gimple-pretty-print.h" |
| #include "fold-const.h" |
| #include "gimple-iterator.h" |
| #include "tree-cfg.h" |
| #include "tree-dfa.h" |
| #include "tree-cfgcleanup.h" |
| #include "alias.h" |
| #include "tree-ssa-loop.h" |
| #include "diagnostic.h" |
| #include "cfghooks.h" |
| #include "tree-into-ssa.h" |
| #include "cfganal.h" |
| #include "dbgcnt.h" |
| #include "target.h" |
| #include "alloc-pool.h" |
| #include "tree-switch-conversion.h" |
| #include "tree-ssa-reassoc.h" |
| |
| using namespace tree_switch_conversion; |
| |
| struct condition_info |
| { |
| typedef auto_vec<std::pair<gphi *, tree>> mapping_vec; |
| |
| condition_info (gcond *cond, bool has_side_effect): m_cond (cond), |
| m_bb (gimple_bb (cond)), m_forwarder_bb (NULL), m_ranges (), |
| m_true_edge (NULL), m_false_edge (NULL), |
| m_true_edge_phi_mapping (), m_false_edge_phi_mapping (), |
| m_has_side_effect (has_side_effect) |
| { |
| m_ranges.create (0); |
| } |
| |
| /* Recond PHI mapping for an original edge E and save these into |
| vector VEC. */ |
| void record_phi_mapping (edge e, mapping_vec *vec); |
| |
| gcond *m_cond; |
| basic_block m_bb; |
| basic_block m_forwarder_bb; |
| auto_vec<range_entry> m_ranges; |
| edge m_true_edge; |
| edge m_false_edge; |
| mapping_vec m_true_edge_phi_mapping; |
| mapping_vec m_false_edge_phi_mapping; |
| bool m_has_side_effect; |
| }; |
| |
| /* Recond PHI mapping for an original edge E and save these into vector VEC. */ |
| |
| void |
| condition_info::record_phi_mapping (edge e, mapping_vec *vec) |
| { |
| for (gphi_iterator gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); |
| gsi_next (&gsi)) |
| { |
| gphi *phi = gsi.phi (); |
| tree arg = PHI_ARG_DEF_FROM_EDGE (phi, e); |
| vec->safe_push (std::make_pair (phi, arg)); |
| } |
| } |
| |
| /* Master structure for one if to switch conversion candidate. */ |
| |
| struct if_chain |
| { |
| /* Default constructor. */ |
| if_chain (): m_entries () |
| { |
| m_entries.create (2); |
| } |
| |
| /* Default destructor. */ |
| ~if_chain () |
| { |
| m_entries.release (); |
| } |
| |
| /* Verify that all case ranges do not overlap. */ |
| bool check_non_overlapping_cases (); |
| |
| /* Return true when the switch can be expanded with a jump table or |
| a bit test (at least partially). */ |
| bool is_beneficial (); |
| |
| /* If chain entries. */ |
| vec<condition_info *> m_entries; |
| }; |
| |
| /* Compare two case ranges by minimum value. */ |
| |
| static int |
| range_cmp (const void *a, const void *b) |
| { |
| const range_entry *re1 = *(const range_entry * const *) a; |
| const range_entry *re2 = *(const range_entry * const *) b; |
| |
| return tree_int_cst_compare (re1->low, re2->low); |
| } |
| |
| /* Verify that all case ranges do not overlap. */ |
| |
| bool |
| if_chain::check_non_overlapping_cases () |
| { |
| auto_vec<range_entry *> all_ranges; |
| for (unsigned i = 0; i < m_entries.length (); i++) |
| for (unsigned j = 0; j < m_entries[i]->m_ranges.length (); j++) |
| all_ranges.safe_push (&m_entries[i]->m_ranges[j]); |
| |
| all_ranges.qsort (range_cmp); |
| |
| for (unsigned i = 0; i < all_ranges.length () - 1; i++) |
| { |
| range_entry *left = all_ranges[i]; |
| range_entry *right = all_ranges[i + 1]; |
| if (tree_int_cst_le (left->low, right->low) |
| && tree_int_cst_le (right->low, left->high)) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /* Compare clusters by minimum value. */ |
| |
| static int |
| cluster_cmp (const void *a, const void *b) |
| { |
| simple_cluster *sc1 = *(simple_cluster * const *) a; |
| simple_cluster *sc2 = *(simple_cluster * const *) b; |
| |
| return tree_int_cst_compare (sc1->get_low (), sc2->get_high ()); |
| } |
| |
| /* Dump constructed CLUSTERS with prefix MESSAGE. */ |
| |
| static void |
| dump_clusters (vec<cluster *> *clusters, const char *message) |
| { |
| if (dump_file) |
| { |
| fprintf (dump_file, ";; %s: ", message); |
| for (unsigned i = 0; i < clusters->length (); i++) |
| (*clusters)[i]->dump (dump_file, dump_flags & TDF_DETAILS); |
| fprintf (dump_file, "\n"); |
| } |
| } |
| |
| /* Return true when the switch can be expanded with a jump table or |
| a bit test (at least partially). */ |
| |
| bool |
| if_chain::is_beneficial () |
| { |
| profile_probability prob = profile_probability::uninitialized (); |
| |
| auto_vec<cluster *> clusters; |
| clusters.create (m_entries.length ()); |
| |
| for (unsigned i = 0; i < m_entries.length (); i++) |
| { |
| condition_info *info = m_entries[i]; |
| for (unsigned j = 0; j < info->m_ranges.length (); j++) |
| { |
| range_entry *range = &info->m_ranges[j]; |
| basic_block bb = info->m_true_edge->dest; |
| bool has_forwarder = !info->m_true_edge_phi_mapping.is_empty (); |
| clusters.safe_push (new simple_cluster (range->low, range->high, |
| NULL_TREE, bb, prob, |
| has_forwarder)); |
| } |
| } |
| |
| /* Sort clusters and merge them. */ |
| auto_vec<cluster *> filtered_clusters; |
| filtered_clusters.create (16); |
| clusters.qsort (cluster_cmp); |
| simple_cluster *left = static_cast<simple_cluster *> (clusters[0]); |
| filtered_clusters.safe_push (left); |
| |
| for (unsigned i = 1; i < clusters.length (); i++) |
| { |
| simple_cluster *right = static_cast<simple_cluster *> (clusters[i]); |
| tree type = TREE_TYPE (left->get_low ()); |
| if (!left->m_has_forward_bb |
| && !right->m_has_forward_bb |
| && left->m_case_bb == right->m_case_bb) |
| { |
| if (wi::eq_p (wi::to_wide (right->get_low ()) - wi::to_wide |
| (left->get_high ()), wi::one (TYPE_PRECISION (type)))) |
| { |
| left->set_high (right->get_high ()); |
| delete right; |
| continue; |
| } |
| } |
| |
| left = static_cast<simple_cluster *> (clusters[i]); |
| filtered_clusters.safe_push (left); |
| } |
| |
| dump_clusters (&filtered_clusters, "Canonical GIMPLE case clusters"); |
| |
| vec<cluster *> output |
| = jump_table_cluster::find_jump_tables (filtered_clusters); |
| bool r = output.length () < filtered_clusters.length (); |
| if (r) |
| { |
| dump_clusters (&output, "JT can be built"); |
| release_clusters (output); |
| return true; |
| } |
| else |
| output.release (); |
| |
| output = bit_test_cluster::find_bit_tests (filtered_clusters); |
| r = output.length () < filtered_clusters.length (); |
| if (r) |
| dump_clusters (&output, "BT can be built"); |
| |
| release_clusters (output); |
| return r; |
| } |
| |
| /* Build case label with MIN and MAX values of a given basic block DEST. */ |
| |
| static tree |
| build_case_label (tree index_type, tree min, tree max, basic_block dest) |
| { |
| if (min != NULL_TREE && index_type != TREE_TYPE (min)) |
| min = fold_convert (index_type, min); |
| if (max != NULL_TREE && index_type != TREE_TYPE (max)) |
| max = fold_convert (index_type, max); |
| |
| tree label = gimple_block_label (dest); |
| return build_case_label (min, min == max ? NULL_TREE : max, label); |
| } |
| |
| /* Compare two integer constants. */ |
| |
| static int |
| label_cmp (const void *a, const void *b) |
| { |
| const_tree l1 = *(const const_tree *) a; |
| const_tree l2 = *(const const_tree *) b; |
| |
| return tree_int_cst_compare (CASE_LOW (l1), CASE_LOW (l2)); |
| } |
| |
| /* Convert a given if CHAIN into a switch GIMPLE statement. */ |
| |
| static void |
| convert_if_conditions_to_switch (if_chain *chain) |
| { |
| if (!dbg_cnt (if_to_switch)) |
| return; |
| |
| auto_vec<tree> labels; |
| unsigned entries = chain->m_entries.length (); |
| condition_info *first_cond = chain->m_entries[0]; |
| condition_info *last_cond = chain->m_entries[entries - 1]; |
| |
| edge default_edge = last_cond->m_false_edge; |
| basic_block default_bb = default_edge->dest; |
| |
| gimple_stmt_iterator gsi = gsi_for_stmt (first_cond->m_cond); |
| tree index_type = TREE_TYPE (first_cond->m_ranges[0].exp); |
| for (unsigned i = 0; i < entries; i++) |
| { |
| condition_info *info = chain->m_entries[i]; |
| basic_block case_bb = info->m_true_edge->dest; |
| |
| /* Create a forwarder block if needed. */ |
| if (!info->m_true_edge_phi_mapping.is_empty ()) |
| { |
| info->m_forwarder_bb = split_edge (info->m_true_edge); |
| case_bb = info->m_forwarder_bb; |
| } |
| |
| for (unsigned j = 0; j < info->m_ranges.length (); j++) |
| labels.safe_push (build_case_label (index_type, |
| info->m_ranges[j].low, |
| info->m_ranges[j].high, |
| case_bb)); |
| default_bb = info->m_false_edge->dest; |
| |
| if (i == 0) |
| { |
| remove_edge (first_cond->m_true_edge); |
| remove_edge (first_cond->m_false_edge); |
| } |
| else |
| delete_basic_block (info->m_bb); |
| |
| make_edge (first_cond->m_bb, case_bb, 0); |
| } |
| |
| labels.qsort (label_cmp); |
| |
| edge e = find_edge (first_cond->m_bb, default_bb); |
| if (e == NULL) |
| e = make_edge (first_cond->m_bb, default_bb, 0); |
| gswitch *s |
| = gimple_build_switch (first_cond->m_ranges[0].exp, |
| build_case_label (index_type, NULL_TREE, |
| NULL_TREE, default_bb), |
| labels); |
| |
| gsi_remove (&gsi, true); |
| gsi_insert_before (&gsi, s, GSI_NEW_STMT); |
| |
| if (dump_file) |
| { |
| fprintf (dump_file, "Expanded into a new gimple STMT: "); |
| print_gimple_stmt (dump_file, s, 0, TDF_SLIM); |
| putc ('\n', dump_file); |
| } |
| |
| /* Fill up missing PHI node arguments. */ |
| for (unsigned i = 0; i < chain->m_entries.length (); ++i) |
| { |
| condition_info *info = chain->m_entries[i]; |
| for (unsigned j = 0; j < info->m_true_edge_phi_mapping.length (); ++j) |
| { |
| std::pair<gphi *, tree> item = info->m_true_edge_phi_mapping[j]; |
| add_phi_arg (item.first, item.second, |
| single_succ_edge (info->m_forwarder_bb), |
| UNKNOWN_LOCATION); |
| } |
| } |
| |
| /* Fill up missing PHI nodes for the default BB. */ |
| for (unsigned j = 0; j < last_cond->m_false_edge_phi_mapping.length (); ++j) |
| { |
| std::pair<gphi *, tree> item = last_cond->m_false_edge_phi_mapping[j]; |
| add_phi_arg (item.first, item.second, e, UNKNOWN_LOCATION); |
| } |
| } |
| |
| /* Identify an index variable used in BB in a GIMPLE condition. |
| Save information about the condition into CONDITIONS_IN_BBS. */ |
| |
| static void |
| find_conditions (basic_block bb, |
| hash_map<basic_block, condition_info *> *conditions_in_bbs) |
| { |
| gimple_stmt_iterator gsi = gsi_last_nondebug_bb (bb); |
| if (gsi_end_p (gsi)) |
| return; |
| |
| gcond *cond = dyn_cast<gcond *> (gsi_stmt (gsi)); |
| if (cond == NULL) |
| return; |
| |
| tree lhs = gimple_cond_lhs (cond); |
| tree rhs = gimple_cond_rhs (cond); |
| tree_code code = gimple_cond_code (cond); |
| |
| condition_info *info = new condition_info (cond, !no_side_effect_bb (bb)); |
| |
| gassign *def; |
| if (code == NE_EXPR |
| && TREE_CODE (lhs) == SSA_NAME |
| && (def = dyn_cast<gassign *> (SSA_NAME_DEF_STMT (lhs))) != NULL |
| && integer_zerop (rhs)) |
| { |
| enum tree_code rhs_code = gimple_assign_rhs_code (def); |
| if (rhs_code == BIT_IOR_EXPR) |
| { |
| info->m_ranges.safe_grow (2, true); |
| init_range_entry (&info->m_ranges[0], gimple_assign_rhs1 (def), NULL); |
| init_range_entry (&info->m_ranges[1], gimple_assign_rhs2 (def), NULL); |
| } |
| } |
| else |
| { |
| info->m_ranges.safe_grow (1, true); |
| init_range_entry (&info->m_ranges[0], NULL_TREE, cond); |
| } |
| |
| /* All identified ranges must have equal expression and IN_P flag. */ |
| if (!info->m_ranges.is_empty ()) |
| { |
| edge true_edge, false_edge; |
| tree expr = info->m_ranges[0].exp; |
| bool in_p = info->m_ranges[0].in_p; |
| |
| extract_true_false_edges_from_block (bb, &true_edge, &false_edge); |
| info->m_true_edge = in_p ? true_edge : false_edge; |
| info->m_false_edge = in_p ? false_edge : true_edge; |
| |
| for (unsigned i = 0; i < info->m_ranges.length (); ++i) |
| if (info->m_ranges[i].exp == NULL_TREE |
| || !INTEGRAL_TYPE_P (TREE_TYPE (info->m_ranges[i].exp)) |
| || info->m_ranges[i].low == NULL_TREE |
| || info->m_ranges[i].high == NULL_TREE |
| || (TYPE_PRECISION (TREE_TYPE (info->m_ranges[i].low)) |
| != TYPE_PRECISION (TREE_TYPE (info->m_ranges[i].high)))) |
| goto exit; |
| |
| for (unsigned i = 1; i < info->m_ranges.length (); ++i) |
| if (info->m_ranges[i].exp != expr |
| || info->m_ranges[i].in_p != in_p) |
| goto exit; |
| |
| info->record_phi_mapping (info->m_true_edge, |
| &info->m_true_edge_phi_mapping); |
| info->record_phi_mapping (info->m_false_edge, |
| &info->m_false_edge_phi_mapping); |
| conditions_in_bbs->put (bb, info); |
| return; |
| } |
| |
| exit: |
| delete info; |
| } |
| |
| namespace { |
| |
| const pass_data pass_data_if_to_switch = |
| { |
| GIMPLE_PASS, /* type */ |
| "iftoswitch", /* name */ |
| OPTGROUP_NONE, /* optinfo_flags */ |
| TV_TREE_IF_TO_SWITCH, /* tv_id */ |
| ( PROP_cfg | PROP_ssa ), /* properties_required */ |
| 0, /* properties_provided */ |
| 0, /* properties_destroyed */ |
| 0, /* todo_flags_start */ |
| TODO_update_ssa /* todo_flags_finish */ |
| }; |
| |
| class pass_if_to_switch : public gimple_opt_pass |
| { |
| public: |
| pass_if_to_switch (gcc::context *ctxt) |
| : gimple_opt_pass (pass_data_if_to_switch, ctxt) |
| {} |
| |
| /* opt_pass methods: */ |
| bool gate (function *) final override |
| { |
| return (jump_table_cluster::is_enabled () |
| || bit_test_cluster::is_enabled ()); |
| } |
| |
| unsigned int execute (function *) final override; |
| |
| }; // class pass_if_to_switch |
| |
| unsigned int |
| pass_if_to_switch::execute (function *fun) |
| { |
| auto_vec<if_chain *> all_candidates; |
| hash_map<basic_block, condition_info *> conditions_in_bbs; |
| |
| basic_block bb; |
| FOR_EACH_BB_FN (bb, fun) |
| find_conditions (bb, &conditions_in_bbs); |
| |
| if (conditions_in_bbs.is_empty ()) |
| return 0; |
| |
| int *rpo = XNEWVEC (int, n_basic_blocks_for_fn (fun)); |
| unsigned n = pre_and_rev_post_order_compute_fn (fun, NULL, rpo, false); |
| |
| auto_bitmap seen_bbs; |
| for (int i = n - 1; i >= 0; --i) |
| { |
| basic_block bb = BASIC_BLOCK_FOR_FN (fun, rpo[i]); |
| if (bitmap_bit_p (seen_bbs, bb->index)) |
| continue; |
| |
| bitmap_set_bit (seen_bbs, bb->index); |
| condition_info **slot = conditions_in_bbs.get (bb); |
| if (slot) |
| { |
| condition_info *info = *slot; |
| if_chain *chain = new if_chain (); |
| chain->m_entries.safe_push (info); |
| /* Try to find a chain starting in this BB. */ |
| while (true) |
| { |
| if (!single_pred_p (gimple_bb (info->m_cond))) |
| break; |
| edge e = single_pred_edge (gimple_bb (info->m_cond)); |
| condition_info **info2 = conditions_in_bbs.get (e->src); |
| if (!info2 || info->m_ranges[0].exp != (*info2)->m_ranges[0].exp) |
| break; |
| |
| /* It is important that the blocks are linked through FALSE_EDGE. |
| For an expression of index != VALUE, true and false edges |
| are flipped. */ |
| if ((*info2)->m_false_edge != e) |
| break; |
| |
| /* Only the first BB in a chain can have a side effect. */ |
| if (info->m_has_side_effect) |
| break; |
| |
| chain->m_entries.safe_push (*info2); |
| bitmap_set_bit (seen_bbs, e->src->index); |
| info = *info2; |
| } |
| |
| chain->m_entries.reverse (); |
| if (chain->m_entries.length () >= 2 |
| && chain->check_non_overlapping_cases () |
| && chain->is_beneficial ()) |
| { |
| gcond *cond = chain->m_entries[0]->m_cond; |
| if (dump_enabled_p ()) |
| dump_printf_loc (MSG_OPTIMIZED_LOCATIONS, cond, |
| "Condition chain with %d BBs " |
| "transformed into a switch statement.\n", |
| chain->m_entries.length ()); |
| all_candidates.safe_push (chain); |
| } |
| else |
| delete chain; |
| } |
| } |
| |
| for (unsigned i = 0; i < all_candidates.length (); i++) |
| { |
| convert_if_conditions_to_switch (all_candidates[i]); |
| delete all_candidates[i]; |
| } |
| |
| free (rpo); |
| |
| for (hash_map<basic_block, condition_info *>::iterator it |
| = conditions_in_bbs.begin (); it != conditions_in_bbs.end (); ++it) |
| delete (*it).second; |
| |
| if (!all_candidates.is_empty ()) |
| { |
| free_dominance_info (CDI_DOMINATORS); |
| return TODO_cleanup_cfg; |
| } |
| |
| return 0; |
| } |
| |
| } // anon namespace |
| |
| gimple_opt_pass * |
| make_pass_if_to_switch (gcc::context *ctxt) |
| { |
| return new pass_if_to_switch (ctxt); |
| } |