--- /dev/null
+/* If-elseif-else to switch conversion pass
+ Copyright (C) 2020 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 vec<std::pair<gphi *, tree>> mapping_vec;
+
+ condition_info (gcond *cond): 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_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;
+ 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;
+};
+
+/* 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 ();
+ if (!virtual_operand_p (gimple_phi_result (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 ());
+ 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");
+ output.release ();
+ if (r)
+ return true;
+
+ output = bit_test_cluster::find_bit_tests (filtered_clusters);
+ r = output.length () < filtered_clusters.length ();
+ if (r)
+ dump_clusters (&output, "BT can be built");
+ output.release ();
+ 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;
+
+ if (!no_side_effect_bb (bb))
+ return;
+
+ tree lhs = gimple_cond_lhs (cond);
+ tree rhs = gimple_cond_rhs (cond);
+ tree_code code = gimple_cond_code (cond);
+
+ condition_info info (cond);
+
+ 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
+ || info.m_ranges[i].low == NULL_TREE
+ || info.m_ranges[i].high == NULL_TREE)
+ return;
+
+ 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)
+ return;
+
+ 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);
+ }
+
+}
+
+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_cleanup_cfg | 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: */
+ virtual bool gate (function *)
+ {
+ return (jump_table_cluster::is_enabled ()
+ || bit_test_cluster::is_enabled ());
+ }
+
+ virtual unsigned int execute (function *);
+
+}; // 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 *info = conditions_in_bbs.get (bb);
+ if (info)
+ {
+ 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;
+
+ 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 () >= 3
+ && 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);
+ }
+ }
+ }
+
+ for (unsigned i = 0; i < all_candidates.length (); i++)
+ {
+ convert_if_conditions_to_switch (all_candidates[i]);
+ delete all_candidates[i];
+ }
+
+ free (rpo);
+
+ if (!all_candidates.is_empty ())
+ {
+ free_dominance_info (CDI_DOMINATORS);
+ mark_virtual_operands_for_renaming (fun);
+ }
+
+ return 0;
+}
+
+} // anon namespace
+
+gimple_opt_pass *
+make_pass_if_to_switch (gcc::context *ctxt)
+{
+ return new pass_if_to_switch (ctxt);
+}
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