| /* SSA Jump Threading |
| Copyright (C) 2005-2019 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/>. */ |
| |
| #include "config.h" |
| #include "system.h" |
| #include "coretypes.h" |
| #include "backend.h" |
| #include "predict.h" |
| #include "tree.h" |
| #include "gimple.h" |
| #include "fold-const.h" |
| #include "cfgloop.h" |
| #include "gimple-iterator.h" |
| #include "tree-cfg.h" |
| #include "tree-ssa-threadupdate.h" |
| #include "params.h" |
| #include "tree-ssa-loop.h" |
| #include "cfganal.h" |
| #include "tree-pass.h" |
| #include "gimple-ssa.h" |
| #include "tree-phinodes.h" |
| #include "tree-inline.h" |
| #include "tree-vectorizer.h" |
| |
| class thread_jumps |
| { |
| public: |
| void find_jump_threads_backwards (basic_block bb, bool speed_p); |
| private: |
| edge profitable_jump_thread_path (basic_block bbi, tree name, tree arg, |
| bool *creates_irreducible_loop); |
| void convert_and_register_current_path (edge taken_edge); |
| void register_jump_thread_path_if_profitable (tree name, tree arg, |
| basic_block def_bb); |
| void handle_assignment (gimple *stmt, tree name, basic_block def_bb); |
| void handle_phi (gphi *phi, tree name, basic_block def_bb); |
| void fsm_find_control_statement_thread_paths (tree name); |
| bool check_subpath_and_update_thread_path (basic_block last_bb, |
| basic_block new_bb, |
| int *next_path_length); |
| |
| /* Maximum number of BBs we are allowed to thread. */ |
| int m_max_threaded_paths; |
| /* Hash to keep track of seen bbs. */ |
| hash_set<basic_block> m_visited_bbs; |
| /* Current path we're analyzing. */ |
| auto_vec<basic_block> m_path; |
| /* Tracks if we have recursed through a loop PHI node. */ |
| bool m_seen_loop_phi; |
| /* Indicate that we could increase code size to improve the |
| code path. */ |
| bool m_speed_p; |
| }; |
| |
| /* Simple helper to get the last statement from BB, which is assumed |
| to be a control statement. Return NULL if the last statement is |
| not a control statement. */ |
| |
| static gimple * |
| get_gimple_control_stmt (basic_block bb) |
| { |
| gimple_stmt_iterator gsi = gsi_last_nondebug_bb (bb); |
| |
| if (gsi_end_p (gsi)) |
| return NULL; |
| |
| gimple *stmt = gsi_stmt (gsi); |
| enum gimple_code code = gimple_code (stmt); |
| if (code == GIMPLE_COND || code == GIMPLE_SWITCH || code == GIMPLE_GOTO) |
| return stmt; |
| return NULL; |
| } |
| |
| /* Return true if the CFG contains at least one path from START_BB to |
| END_BB. When a path is found, record in PATH the blocks from |
| END_BB to START_BB. LOCAL_VISITED_BBS is used to make sure we |
| don't fall into an infinite loop. Bound the recursion to basic |
| blocks belonging to LOOP. */ |
| |
| static bool |
| fsm_find_thread_path (basic_block start_bb, basic_block end_bb, |
| vec<basic_block> &path, |
| hash_set<basic_block> &local_visited_bbs, |
| loop_p loop) |
| { |
| if (loop != start_bb->loop_father) |
| return false; |
| |
| if (start_bb == end_bb) |
| { |
| path.safe_push (start_bb); |
| return true; |
| } |
| |
| if (!local_visited_bbs.add (start_bb)) |
| { |
| edge e; |
| edge_iterator ei; |
| FOR_EACH_EDGE (e, ei, start_bb->succs) |
| if (fsm_find_thread_path (e->dest, end_bb, path, local_visited_bbs, |
| loop)) |
| { |
| path.safe_push (start_bb); |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /* Examine jump threading path PATH to which we want to add BBI. |
| |
| If the resulting path is profitable to thread, then return the |
| final taken edge from the path, NULL otherwise. |
| |
| NAME is the SSA_NAME of the variable we found to have a constant |
| value on PATH. ARG is the constant value of NAME on that path. |
| |
| BBI will be appended to PATH when we have a profitable jump |
| threading path. Callers are responsible for removing BBI from PATH |
| in that case. */ |
| |
| edge |
| thread_jumps::profitable_jump_thread_path (basic_block bbi, tree name, |
| tree arg, |
| bool *creates_irreducible_loop) |
| { |
| /* Note BBI is not in the path yet, hence the +1 in the test below |
| to make sure BBI is accounted for in the path length test. */ |
| |
| /* We can get a length of 0 here when the statement that |
| makes a conditional generate a compile-time constant |
| result is in the same block as the conditional. |
| |
| That's not really a jump threading opportunity, but instead is |
| simple cprop & simplification. We could handle it here if we |
| wanted by wiring up all the incoming edges. If we run this |
| early in IPA, that might be worth doing. For now we just |
| reject that case. */ |
| if (m_path.is_empty ()) |
| return NULL; |
| |
| if (m_path.length () + 1 |
| > (unsigned) PARAM_VALUE (PARAM_MAX_FSM_THREAD_LENGTH)) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "FSM jump-thread path not considered: " |
| "the number of basic blocks on the path " |
| "exceeds PARAM_MAX_FSM_THREAD_LENGTH.\n"); |
| return NULL; |
| } |
| |
| if (m_max_threaded_paths <= 0) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "FSM jump-thread path not considered: " |
| "the number of previously recorded FSM paths to " |
| "thread exceeds PARAM_MAX_FSM_THREAD_PATHS.\n"); |
| return NULL; |
| } |
| |
| /* Add BBI to the path. |
| From this point onward, if we decide we the path is not profitable |
| to thread, we must remove BBI from the path. */ |
| m_path.safe_push (bbi); |
| |
| int n_insns = 0; |
| gimple_stmt_iterator gsi; |
| loop_p loop = m_path[0]->loop_father; |
| bool path_crosses_loops = false; |
| bool threaded_through_latch = false; |
| bool multiway_branch_in_path = false; |
| bool threaded_multiway_branch = false; |
| bool contains_hot_bb = false; |
| |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "Checking profitability of path (backwards): "); |
| |
| /* Count the number of instructions on the path: as these instructions |
| will have to be duplicated, we will not record the path if there |
| are too many instructions on the path. Also check that all the |
| blocks in the path belong to a single loop. */ |
| for (unsigned j = 0; j < m_path.length (); j++) |
| { |
| basic_block bb = m_path[j]; |
| |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, " bb:%i", bb->index); |
| /* Remember, blocks in the path are stored in opposite order |
| in the PATH array. The last entry in the array represents |
| the block with an outgoing edge that we will redirect to the |
| jump threading path. Thus we don't care about that block's |
| loop father, nor how many statements are in that block because |
| it will not be copied or whether or not it ends in a multiway |
| branch. */ |
| if (j < m_path.length () - 1) |
| { |
| int orig_n_insns = n_insns; |
| if (bb->loop_father != loop) |
| { |
| path_crosses_loops = true; |
| break; |
| } |
| |
| /* PHIs in the path will create degenerate PHIS in the |
| copied path which will then get propagated away, so |
| looking at just the duplicate path the PHIs would |
| seem unimportant. |
| |
| But those PHIs, because they're assignments to objects |
| typically with lives that exist outside the thread path, |
| will tend to generate PHIs (or at least new PHI arguments) |
| at points where we leave the thread path and rejoin |
| the original blocks. So we do want to account for them. |
| |
| We ignore virtual PHIs. We also ignore cases where BB |
| has a single incoming edge. That's the most common |
| degenerate PHI we'll see here. Finally we ignore PHIs |
| that are associated with the value we're tracking as |
| that object likely dies. */ |
| if (EDGE_COUNT (bb->succs) > 1 && EDGE_COUNT (bb->preds) > 1) |
| { |
| for (gphi_iterator gsip = gsi_start_phis (bb); |
| !gsi_end_p (gsip); |
| gsi_next (&gsip)) |
| { |
| gphi *phi = gsip.phi (); |
| tree dst = gimple_phi_result (phi); |
| |
| /* Note that if both NAME and DST are anonymous |
| SSA_NAMEs, then we do not have enough information |
| to consider them associated. */ |
| if (dst != name |
| && (SSA_NAME_VAR (dst) != SSA_NAME_VAR (name) |
| || !SSA_NAME_VAR (dst)) |
| && !virtual_operand_p (dst)) |
| ++n_insns; |
| } |
| } |
| |
| if (!contains_hot_bb && m_speed_p) |
| contains_hot_bb |= optimize_bb_for_speed_p (bb); |
| for (gsi = gsi_after_labels (bb); |
| !gsi_end_p (gsi); |
| gsi_next_nondebug (&gsi)) |
| { |
| gimple *stmt = gsi_stmt (gsi); |
| /* Do not count empty statements and labels. */ |
| if (gimple_code (stmt) != GIMPLE_NOP |
| && !(gimple_code (stmt) == GIMPLE_ASSIGN |
| && gimple_assign_rhs_code (stmt) == ASSERT_EXPR) |
| && !is_gimple_debug (stmt)) |
| n_insns += estimate_num_insns (stmt, &eni_size_weights); |
| } |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, " (%i insns)", n_insns-orig_n_insns); |
| |
| /* We do not look at the block with the threaded branch |
| in this loop. So if any block with a last statement that |
| is a GIMPLE_SWITCH or GIMPLE_GOTO is seen, then we have a |
| multiway branch on our path. |
| |
| The block in PATH[0] is special, it's the block were we're |
| going to be able to eliminate its branch. */ |
| gimple *last = last_stmt (bb); |
| if (last && (gimple_code (last) == GIMPLE_SWITCH |
| || gimple_code (last) == GIMPLE_GOTO)) |
| { |
| if (j == 0) |
| threaded_multiway_branch = true; |
| else |
| multiway_branch_in_path = true; |
| } |
| } |
| |
| /* Note if we thread through the latch, we will want to include |
| the last entry in the array when determining if we thread |
| through the loop latch. */ |
| if (loop->latch == bb) |
| threaded_through_latch = true; |
| } |
| |
| gimple *stmt = get_gimple_control_stmt (m_path[0]); |
| gcc_assert (stmt); |
| |
| /* We are going to remove the control statement at the end of the |
| last block in the threading path. So don't count it against our |
| statement count. */ |
| |
| int stmt_insns = estimate_num_insns (stmt, &eni_size_weights); |
| n_insns-= stmt_insns; |
| |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "\n Control statement insns: %i\n" |
| " Overall: %i insns\n", |
| stmt_insns, n_insns); |
| |
| /* We have found a constant value for ARG. For GIMPLE_SWITCH |
| and GIMPLE_GOTO, we use it as-is. However, for a GIMPLE_COND |
| we need to substitute, fold and simplify so we can determine |
| the edge taken out of the last block. */ |
| if (gimple_code (stmt) == GIMPLE_COND) |
| { |
| enum tree_code cond_code = gimple_cond_code (stmt); |
| |
| /* We know the underyling format of the condition. */ |
| arg = fold_binary (cond_code, boolean_type_node, |
| arg, gimple_cond_rhs (stmt)); |
| } |
| |
| /* If this path threaded through the loop latch back into the |
| same loop and the destination does not dominate the loop |
| latch, then this thread would create an irreducible loop. |
| |
| We have to know the outgoing edge to figure this out. */ |
| edge taken_edge = find_taken_edge (m_path[0], arg); |
| |
| /* There are cases where we may not be able to extract the |
| taken edge. For example, a computed goto to an absolute |
| address. Handle those cases gracefully. */ |
| if (taken_edge == NULL) |
| { |
| m_path.pop (); |
| return NULL; |
| } |
| |
| *creates_irreducible_loop = false; |
| if (threaded_through_latch |
| && loop == taken_edge->dest->loop_father |
| && (determine_bb_domination_status (loop, taken_edge->dest) |
| == DOMST_NONDOMINATING)) |
| *creates_irreducible_loop = true; |
| |
| if (path_crosses_loops) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "FSM jump-thread path not considered: " |
| "the path crosses loops.\n"); |
| m_path.pop (); |
| return NULL; |
| } |
| |
| /* Threading is profitable if the path duplicated is hot but also |
| in a case we separate cold path from hot path and permit optimization |
| of the hot path later. Be on the agressive side here. In some testcases, |
| as in PR 78407 this leads to noticeable improvements. */ |
| if (m_speed_p && (optimize_edge_for_speed_p (taken_edge) || contains_hot_bb)) |
| { |
| if (n_insns >= PARAM_VALUE (PARAM_MAX_FSM_THREAD_PATH_INSNS)) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "FSM jump-thread path not considered: " |
| "the number of instructions on the path " |
| "exceeds PARAM_MAX_FSM_THREAD_PATH_INSNS.\n"); |
| m_path.pop (); |
| return NULL; |
| } |
| } |
| else if (n_insns > 1) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "FSM jump-thread path not considered: " |
| "duplication of %i insns is needed and optimizing for size.\n", |
| n_insns); |
| m_path.pop (); |
| return NULL; |
| } |
| |
| /* We avoid creating irreducible inner loops unless we thread through |
| a multiway branch, in which case we have deemed it worth losing |
| other loop optimizations later. |
| |
| We also consider it worth creating an irreducible inner loop if |
| the number of copied statement is low relative to the length of |
| the path -- in that case there's little the traditional loop |
| optimizer would have done anyway, so an irreducible loop is not |
| so bad. */ |
| if (!threaded_multiway_branch && *creates_irreducible_loop |
| && (n_insns * (unsigned) PARAM_VALUE (PARAM_FSM_SCALE_PATH_STMTS) |
| > (m_path.length () * |
| (unsigned) PARAM_VALUE (PARAM_FSM_SCALE_PATH_BLOCKS)))) |
| |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, |
| "FSM would create irreducible loop without threading " |
| "multiway branch.\n"); |
| m_path.pop (); |
| return NULL; |
| } |
| |
| |
| /* If this path does not thread through the loop latch, then we are |
| using the FSM threader to find old style jump threads. This |
| is good, except the FSM threader does not re-use an existing |
| threading path to reduce code duplication. |
| |
| So for that case, drastically reduce the number of statements |
| we are allowed to copy. */ |
| if (!(threaded_through_latch && threaded_multiway_branch) |
| && (n_insns * PARAM_VALUE (PARAM_FSM_SCALE_PATH_STMTS) |
| >= PARAM_VALUE (PARAM_MAX_JUMP_THREAD_DUPLICATION_STMTS))) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, |
| "FSM did not thread around loop and would copy too " |
| "many statements.\n"); |
| m_path.pop (); |
| return NULL; |
| } |
| |
| /* When there is a multi-way branch on the path, then threading can |
| explode the CFG due to duplicating the edges for that multi-way |
| branch. So like above, only allow a multi-way branch on the path |
| if we actually thread a multi-way branch. */ |
| if (!threaded_multiway_branch && multiway_branch_in_path) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, |
| "FSM Thread through multiway branch without threading " |
| "a multiway branch.\n"); |
| m_path.pop (); |
| return NULL; |
| } |
| return taken_edge; |
| } |
| |
| /* The current path PATH is a vector of blocks forming a jump threading |
| path in reverse order. TAKEN_EDGE is the edge taken from path[0]. |
| |
| Convert the current path into the form used by register_jump_thread and |
| register it. */ |
| |
| void |
| thread_jumps::convert_and_register_current_path (edge taken_edge) |
| { |
| vec<jump_thread_edge *> *jump_thread_path = new vec<jump_thread_edge *> (); |
| |
| /* Record the edges between the blocks in PATH. */ |
| for (unsigned int j = 0; j + 1 < m_path.length (); j++) |
| { |
| basic_block bb1 = m_path[m_path.length () - j - 1]; |
| basic_block bb2 = m_path[m_path.length () - j - 2]; |
| |
| edge e = find_edge (bb1, bb2); |
| gcc_assert (e); |
| jump_thread_edge *x = new jump_thread_edge (e, EDGE_FSM_THREAD); |
| jump_thread_path->safe_push (x); |
| } |
| |
| /* Add the edge taken when the control variable has value ARG. */ |
| jump_thread_edge *x |
| = new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK); |
| jump_thread_path->safe_push (x); |
| |
| register_jump_thread (jump_thread_path); |
| --m_max_threaded_paths; |
| } |
| |
| /* While following a chain of SSA_NAME definitions, we jumped from a |
| definition in LAST_BB to a definition in NEW_BB (walking |
| backwards). |
| |
| Verify there is a single path between the blocks and none of the |
| blocks in the path is already in VISITED_BBS. If so, then update |
| VISISTED_BBS, add the new blocks to PATH and return TRUE. |
| Otherwise return FALSE. |
| |
| Store the length of the subpath in NEXT_PATH_LENGTH. */ |
| |
| bool |
| thread_jumps::check_subpath_and_update_thread_path (basic_block last_bb, |
| basic_block new_bb, |
| int *next_path_length) |
| { |
| edge e; |
| int e_count = 0; |
| edge_iterator ei; |
| auto_vec<basic_block> next_path; |
| |
| FOR_EACH_EDGE (e, ei, last_bb->preds) |
| { |
| hash_set<basic_block> local_visited_bbs; |
| |
| if (fsm_find_thread_path (new_bb, e->src, next_path, |
| local_visited_bbs, e->src->loop_father)) |
| ++e_count; |
| |
| /* If there is more than one path, stop. */ |
| if (e_count > 1) |
| return false; |
| } |
| |
| /* Stop if we have not found a path: this could occur when the recursion |
| is stopped by one of the bounds. */ |
| if (e_count == 0) |
| return false; |
| |
| /* Make sure we haven't already visited any of the nodes in |
| NEXT_PATH. Don't add them here to avoid pollution. */ |
| for (unsigned int i = 0; i + 1 < next_path.length (); i++) |
| { |
| if (m_visited_bbs.contains (next_path[i])) |
| return false; |
| } |
| |
| /* Now add the nodes to VISISTED_BBS. */ |
| for (unsigned int i = 0; i + 1 < next_path.length (); i++) |
| m_visited_bbs.add (next_path[i]); |
| |
| /* Append all the nodes from NEXT_PATH to PATH. */ |
| m_path.safe_splice (next_path); |
| *next_path_length = next_path.length (); |
| |
| return true; |
| } |
| |
| /* If this is a profitable jump thread path, register it. |
| |
| NAME is an SSA NAME with a possible constant value of ARG on PATH. |
| |
| DEF_BB is the basic block that ultimately defines the constant. */ |
| |
| void |
| thread_jumps::register_jump_thread_path_if_profitable (tree name, tree arg, |
| basic_block def_bb) |
| { |
| if (TREE_CODE_CLASS (TREE_CODE (arg)) != tcc_constant) |
| return; |
| |
| bool irreducible = false; |
| edge taken_edge = profitable_jump_thread_path (def_bb, name, arg, |
| &irreducible); |
| if (taken_edge) |
| { |
| convert_and_register_current_path (taken_edge); |
| m_path.pop (); |
| |
| if (irreducible) |
| vect_free_loop_info_assumptions (m_path[0]->loop_father); |
| } |
| } |
| |
| /* Given PHI which defines NAME in block DEF_BB, recurse through the |
| PHI's arguments searching for paths where NAME will ultimately have |
| a constant value. |
| |
| PATH contains the series of blocks to traverse that will result in |
| NAME having a constant value. */ |
| |
| void |
| thread_jumps::handle_phi (gphi *phi, tree name, basic_block def_bb) |
| { |
| /* Iterate over the arguments of PHI. */ |
| for (unsigned int i = 0; i < gimple_phi_num_args (phi); i++) |
| { |
| tree arg = gimple_phi_arg_def (phi, i); |
| basic_block bbi = gimple_phi_arg_edge (phi, i)->src; |
| |
| /* Skip edges pointing outside the current loop. */ |
| if (!arg || def_bb->loop_father != bbi->loop_father) |
| continue; |
| |
| if (TREE_CODE (arg) == SSA_NAME) |
| { |
| m_path.safe_push (bbi); |
| /* Recursively follow SSA_NAMEs looking for a constant |
| definition. */ |
| fsm_find_control_statement_thread_paths (arg); |
| |
| m_path.pop (); |
| continue; |
| } |
| |
| register_jump_thread_path_if_profitable (name, arg, bbi); |
| } |
| } |
| |
| /* Return TRUE if STMT is a gimple assignment we want to either directly |
| handle or recurse through. Return FALSE otherwise. |
| |
| Note that adding more cases here requires adding cases to handle_assignment |
| below. */ |
| |
| static bool |
| handle_assignment_p (gimple *stmt) |
| { |
| if (is_gimple_assign (stmt)) |
| { |
| enum tree_code def_code = gimple_assign_rhs_code (stmt); |
| |
| /* If the RHS is an SSA_NAME, then we will recurse through it. |
| Go ahead and filter out cases where the SSA_NAME is a default |
| definition. There's little to be gained by trying to handle that. */ |
| if (def_code == SSA_NAME |
| && !SSA_NAME_IS_DEFAULT_DEF (gimple_assign_rhs1 (stmt))) |
| return true; |
| |
| /* If the RHS is a constant, then it's a terminal that we'll want |
| to handle as well. */ |
| if (TREE_CODE_CLASS (def_code) == tcc_constant) |
| return true; |
| } |
| |
| /* Anything not explicitly allowed is not handled. */ |
| return false; |
| } |
| |
| /* Given STMT which defines NAME in block DEF_BB, recurse through the |
| PHI's arguments searching for paths where NAME will ultimately have |
| a constant value. |
| |
| PATH contains the series of blocks to traverse that will result in |
| NAME having a constant value. */ |
| |
| void |
| thread_jumps::handle_assignment (gimple *stmt, tree name, basic_block def_bb) |
| { |
| tree arg = gimple_assign_rhs1 (stmt); |
| |
| if (TREE_CODE (arg) == SSA_NAME) |
| fsm_find_control_statement_thread_paths (arg); |
| |
| else |
| { |
| /* register_jump_thread_path_if_profitable will push the current |
| block onto the path. But the path will always have the current |
| block at this point. So we can just pop it. */ |
| m_path.pop (); |
| |
| register_jump_thread_path_if_profitable (name, arg, def_bb); |
| |
| /* And put the current block back onto the path so that the |
| state of the stack is unchanged when we leave. */ |
| m_path.safe_push (def_bb); |
| } |
| } |
| |
| /* We trace the value of the SSA_NAME NAME back through any phi nodes |
| looking for places where it gets a constant value and save the |
| path. */ |
| |
| void |
| thread_jumps::fsm_find_control_statement_thread_paths (tree name) |
| { |
| /* If NAME appears in an abnormal PHI, then don't try to trace its |
| value back through PHI nodes. */ |
| if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (name)) |
| return; |
| |
| gimple *def_stmt = SSA_NAME_DEF_STMT (name); |
| basic_block def_bb = gimple_bb (def_stmt); |
| |
| if (def_bb == NULL) |
| return; |
| |
| /* We allow the SSA chain to contains PHIs and simple copies and constant |
| initializations. */ |
| if (gimple_code (def_stmt) != GIMPLE_PHI |
| && gimple_code (def_stmt) != GIMPLE_ASSIGN) |
| return; |
| |
| if (gimple_code (def_stmt) == GIMPLE_PHI |
| && (gimple_phi_num_args (def_stmt) |
| >= (unsigned) PARAM_VALUE (PARAM_FSM_MAXIMUM_PHI_ARGUMENTS))) |
| return; |
| |
| if (is_gimple_assign (def_stmt) |
| && ! handle_assignment_p (def_stmt)) |
| return; |
| |
| /* Avoid infinite recursion. */ |
| if (m_visited_bbs.add (def_bb)) |
| return; |
| |
| int next_path_length = 0; |
| basic_block last_bb_in_path = m_path.last (); |
| |
| if (loop_containing_stmt (def_stmt)->header == gimple_bb (def_stmt)) |
| { |
| /* Do not walk through more than one loop PHI node. */ |
| if (m_seen_loop_phi) |
| return; |
| m_seen_loop_phi = true; |
| } |
| |
| /* Following the chain of SSA_NAME definitions, we jumped from a definition in |
| LAST_BB_IN_PATH to a definition in DEF_BB. When these basic blocks are |
| different, append to PATH the blocks from LAST_BB_IN_PATH to DEF_BB. */ |
| if (def_bb != last_bb_in_path) |
| { |
| /* When DEF_BB == LAST_BB_IN_PATH, then the first block in the path |
| will already be in VISITED_BBS. When they are not equal, then we |
| must ensure that first block is accounted for to ensure we do not |
| create bogus jump threading paths. */ |
| m_visited_bbs.add (m_path[0]); |
| if (!check_subpath_and_update_thread_path (last_bb_in_path, def_bb, |
| &next_path_length)) |
| return; |
| } |
| |
| gcc_assert (m_path.last () == def_bb); |
| |
| if (gimple_code (def_stmt) == GIMPLE_PHI) |
| handle_phi (as_a <gphi *> (def_stmt), name, def_bb); |
| else if (gimple_code (def_stmt) == GIMPLE_ASSIGN) |
| handle_assignment (def_stmt, name, def_bb); |
| |
| /* Remove all the nodes that we added from NEXT_PATH. */ |
| if (next_path_length) |
| m_path.truncate (m_path.length () - next_path_length); |
| } |
| |
| /* Search backwards from BB looking for paths where NAME (an SSA_NAME) |
| is a constant. Record such paths for jump threading. |
| |
| It is assumed that BB ends with a control statement and that by |
| finding a path where NAME is a constant, we can thread the path. |
| SPEED_P indicates that we could increase code size to improve the |
| code path. */ |
| |
| void |
| thread_jumps::find_jump_threads_backwards (basic_block bb, bool speed_p) |
| { |
| gimple *stmt = get_gimple_control_stmt (bb); |
| if (!stmt) |
| return; |
| |
| enum gimple_code code = gimple_code (stmt); |
| tree name = NULL; |
| if (code == GIMPLE_SWITCH) |
| name = gimple_switch_index (as_a <gswitch *> (stmt)); |
| else if (code == GIMPLE_GOTO) |
| name = gimple_goto_dest (stmt); |
| else if (code == GIMPLE_COND) |
| { |
| if (TREE_CODE (gimple_cond_lhs (stmt)) == SSA_NAME |
| && TREE_CODE_CLASS (TREE_CODE (gimple_cond_rhs (stmt))) == tcc_constant |
| && (INTEGRAL_TYPE_P (TREE_TYPE (gimple_cond_lhs (stmt))) |
| || POINTER_TYPE_P (TREE_TYPE (gimple_cond_lhs (stmt))))) |
| name = gimple_cond_lhs (stmt); |
| } |
| |
| if (!name || TREE_CODE (name) != SSA_NAME) |
| return; |
| |
| /* Initialize pass local data that's different for each BB. */ |
| m_path.truncate (0); |
| m_path.safe_push (bb); |
| m_visited_bbs.empty (); |
| m_seen_loop_phi = false; |
| m_speed_p = speed_p; |
| m_max_threaded_paths = PARAM_VALUE (PARAM_MAX_FSM_THREAD_PATHS); |
| |
| fsm_find_control_statement_thread_paths (name); |
| } |
| |
| namespace { |
| |
| const pass_data pass_data_thread_jumps = |
| { |
| GIMPLE_PASS, |
| "thread", |
| OPTGROUP_NONE, |
| TV_TREE_SSA_THREAD_JUMPS, |
| ( PROP_cfg | PROP_ssa ), |
| 0, |
| 0, |
| 0, |
| TODO_update_ssa, |
| }; |
| |
| class pass_thread_jumps : public gimple_opt_pass |
| { |
| public: |
| pass_thread_jumps (gcc::context *ctxt) |
| : gimple_opt_pass (pass_data_thread_jumps, ctxt) |
| {} |
| |
| opt_pass * clone (void) { return new pass_thread_jumps (m_ctxt); } |
| virtual bool gate (function *); |
| virtual unsigned int execute (function *); |
| }; |
| |
| bool |
| pass_thread_jumps::gate (function *fun ATTRIBUTE_UNUSED) |
| { |
| return flag_expensive_optimizations; |
| } |
| |
| |
| unsigned int |
| pass_thread_jumps::execute (function *fun) |
| { |
| loop_optimizer_init (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES); |
| |
| /* Try to thread each block with more than one successor. */ |
| thread_jumps threader; |
| basic_block bb; |
| FOR_EACH_BB_FN (bb, fun) |
| { |
| if (EDGE_COUNT (bb->succs) > 1) |
| threader.find_jump_threads_backwards (bb, true); |
| } |
| bool changed = thread_through_all_blocks (true); |
| |
| loop_optimizer_finalize (); |
| return changed ? TODO_cleanup_cfg : 0; |
| } |
| |
| } |
| |
| gimple_opt_pass * |
| make_pass_thread_jumps (gcc::context *ctxt) |
| { |
| return new pass_thread_jumps (ctxt); |
| } |
| |
| namespace { |
| |
| const pass_data pass_data_early_thread_jumps = |
| { |
| GIMPLE_PASS, |
| "ethread", |
| OPTGROUP_NONE, |
| TV_TREE_SSA_THREAD_JUMPS, |
| ( PROP_cfg | PROP_ssa ), |
| 0, |
| 0, |
| 0, |
| ( TODO_cleanup_cfg | TODO_update_ssa ), |
| }; |
| |
| class pass_early_thread_jumps : public gimple_opt_pass |
| { |
| public: |
| pass_early_thread_jumps (gcc::context *ctxt) |
| : gimple_opt_pass (pass_data_early_thread_jumps, ctxt) |
| {} |
| |
| opt_pass * clone (void) { return new pass_early_thread_jumps (m_ctxt); } |
| virtual bool gate (function *); |
| virtual unsigned int execute (function *); |
| }; |
| |
| bool |
| pass_early_thread_jumps::gate (function *fun ATTRIBUTE_UNUSED) |
| { |
| return true; |
| } |
| |
| |
| unsigned int |
| pass_early_thread_jumps::execute (function *fun) |
| { |
| loop_optimizer_init (AVOID_CFG_MODIFICATIONS); |
| |
| /* Try to thread each block with more than one successor. */ |
| thread_jumps threader; |
| basic_block bb; |
| FOR_EACH_BB_FN (bb, fun) |
| { |
| if (EDGE_COUNT (bb->succs) > 1) |
| threader.find_jump_threads_backwards (bb, false); |
| } |
| thread_through_all_blocks (true); |
| |
| loop_optimizer_finalize (); |
| return 0; |
| } |
| |
| } |
| |
| gimple_opt_pass * |
| make_pass_early_thread_jumps (gcc::context *ctxt) |
| { |
| return new pass_early_thread_jumps (ctxt); |
| } |