X-Git-Url: http://git.sourceforge.jp/view?a=blobdiff_plain;f=gcc%2Ftree-ssa-dce.c;h=4e3499aa6e11c5b152c4cca9e9317b3b3c814c5f;hb=1799fbab6a341bb44efe74b182c3e42e71d1ffd7;hp=38f313daa7d71f2147d1f5f991c3d50399fead30;hpb=2a3ebafa45c591f2c37dcc249816c71c7930245b;p=pf3gnuchains%2Fgcc-fork.git diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c index 38f313daa7d..4e3499aa6e1 100644 --- a/gcc/tree-ssa-dce.c +++ b/gcc/tree-ssa-dce.c @@ -1,22 +1,22 @@ /* Dead code elimination pass for the GNU compiler. - Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008 + Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. Contributed by Ben Elliston and Andrew MacLeod Adapted to use control dependence by Steven Bosscher, SUSE Labs. - + 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 . */ @@ -87,6 +87,9 @@ static sbitmap processed; marked as necessary. */ static sbitmap last_stmt_necessary; +/* Vector indicating that BB contains statements that are live. */ +static sbitmap bb_contains_live_stmts; + /* Before we can determine whether a control branch is dead, we need to compute which blocks are control dependent on which edges. @@ -218,6 +221,8 @@ mark_stmt_necessary (gimple stmt, bool add_to_worklist) gimple_set_plf (stmt, STMT_NECESSARY, true); if (add_to_worklist) VEC_safe_push (gimple, heap, worklist, stmt); + if (bb_contains_live_stmts && !is_gimple_debug (stmt)) + SET_BIT (bb_contains_live_stmts, gimple_bb (stmt)->index); } @@ -256,6 +261,8 @@ mark_operand_necessary (tree op) } gimple_set_plf (stmt, STMT_NECESSARY, true); + if (bb_contains_live_stmts) + SET_BIT (bb_contains_live_stmts, gimple_bb (stmt)->index); VEC_safe_push (gimple, heap, worklist, stmt); } @@ -315,17 +322,18 @@ mark_stmt_if_obviously_necessary (gimple stmt, bool aggressive) case GIMPLE_ASSIGN: if (!lhs) lhs = gimple_assign_lhs (stmt); - /* These values are mildly magic bits of the EH runtime. We can't - see the entire lifetime of these values until landing pads are - generated. */ - if (TREE_CODE (lhs) == EXC_PTR_EXPR - || TREE_CODE (lhs) == FILTER_EXPR) - { - mark_stmt_necessary (stmt, true); - return; - } break; + case GIMPLE_DEBUG: + /* Debug temps without a value are not useful. ??? If we could + easily locate the debug temp bind stmt for a use thereof, + would could refrain from marking all debug temps here, and + mark them only if they're used. */ + if (gimple_debug_bind_has_value_p (stmt) + || TREE_CODE (gimple_debug_bind_get_var (stmt)) != DEBUG_EXPR_DECL) + mark_stmt_necessary (stmt, false); + return; + case GIMPLE_GOTO: gcc_assert (!simple_goto_p (stmt)); mark_stmt_necessary (stmt, true); @@ -385,6 +393,7 @@ mark_control_dependent_edges_necessary (basic_block bb, struct edge_list *el) if (TEST_BIT (last_stmt_necessary, cd_bb->index)) continue; SET_BIT (last_stmt_necessary, cd_bb->index); + SET_BIT (bb_contains_live_stmts, cd_bb->index); stmt = last_stmt (cd_bb); if (stmt && is_ctrl_stmt (stmt)) @@ -426,17 +435,42 @@ find_obviously_necessary_stmts (struct edge_list *el) } } + /* Pure and const functions are finite and thus have no infinite loops in + them. */ + if ((TREE_READONLY (current_function_decl) + || DECL_PURE_P (current_function_decl)) + && !DECL_LOOPING_CONST_OR_PURE_P (current_function_decl)) + return; + + /* Prevent the empty possibly infinite loops from being removed. */ if (el) { - /* Prevent the loops from being removed. We must keep the infinite loops, - and we currently do not have a means to recognize the finite ones. */ - FOR_EACH_BB (bb) - { - edge_iterator ei; - FOR_EACH_EDGE (e, ei, bb->succs) - if (e->flags & EDGE_DFS_BACK) - mark_control_dependent_edges_necessary (e->dest, el); - } + loop_iterator li; + struct loop *loop; + scev_initialize (); + if (mark_irreducible_loops ()) + FOR_EACH_BB (bb) + { + edge_iterator ei; + FOR_EACH_EDGE (e, ei, bb->succs) + if ((e->flags & EDGE_DFS_BACK) + && (e->flags & EDGE_IRREDUCIBLE_LOOP)) + { + if (dump_file) + fprintf (dump_file, "Marking back edge of irreducible loop %i->%i\n", + e->src->index, e->dest->index); + mark_control_dependent_edges_necessary (e->dest, el); + } + } + + FOR_EACH_LOOP (li, loop, 0) + if (!finite_loop_p (loop)) + { + if (dump_file) + fprintf (dump_file, "can not prove finiteness of loop %i\n", loop->num); + mark_control_dependent_edges_necessary (loop->latch, el); + } + scev_finalize (); } } @@ -452,29 +486,23 @@ ref_may_be_aliased (tree ref) && !may_be_aliased (ref)); } -struct ref_data { - tree base; - HOST_WIDE_INT size; - HOST_WIDE_INT offset; - HOST_WIDE_INT max_size; -}; - static bitmap visited = NULL; static unsigned int longest_chain = 0; static unsigned int total_chain = 0; +static unsigned int nr_walks = 0; static bool chain_ovfl = false; /* Worker for the walker that marks reaching definitions of REF, which is based on a non-aliased decl, necessary. It returns true whenever the defining statement of the current VDEF is a kill for REF, as no dominating may-defs are necessary for REF - anymore. DATA points to cached get_ref_base_and_extent data for REF. */ + anymore. DATA points to the basic-block that contains the + stmt that refers to REF. */ static bool -mark_aliased_reaching_defs_necessary_1 (tree ref, tree vdef, void *data) +mark_aliased_reaching_defs_necessary_1 (ao_ref *ref, tree vdef, void *data) { gimple def_stmt = SSA_NAME_DEF_STMT (vdef); - struct ref_data *refd = (struct ref_data *)data; /* All stmts we visit are necessary. */ mark_operand_necessary (vdef); @@ -485,22 +513,30 @@ mark_aliased_reaching_defs_necessary_1 (tree ref, tree vdef, void *data) { tree base, lhs = gimple_get_lhs (def_stmt); HOST_WIDE_INT size, offset, max_size; + ao_ref_base (ref); base = get_ref_base_and_extent (lhs, &offset, &size, &max_size); /* We can get MEM[symbol: sZ, index: D.8862_1] here, so base == refd->base does not always hold. */ - if (base == refd->base) + if (base == ref->base) { /* For a must-alias check we need to be able to constrain the accesses properly. */ if (size != -1 && size == max_size - && refd->max_size != -1) + && ref->max_size != -1) { - if (offset <= refd->offset - && offset + size >= refd->offset + refd->max_size) + if (offset <= ref->offset + && offset + size >= ref->offset + ref->max_size) return true; } /* Or they need to be exactly the same. */ - else if (operand_equal_p (ref, lhs, 0)) + else if (ref->ref + /* Make sure there is no induction variable involved + in the references (gcc.c-torture/execute/pr42142.c). + The simplest way is to check if the kill dominates + the use. */ + && dominated_by_p (CDI_DOMINATORS, (basic_block) data, + gimple_bb (def_stmt)) + && operand_equal_p (ref->ref, lhs, 0)) return true; } } @@ -512,17 +548,17 @@ mark_aliased_reaching_defs_necessary_1 (tree ref, tree vdef, void *data) static void mark_aliased_reaching_defs_necessary (gimple stmt, tree ref) { - struct ref_data refd; unsigned int chain; + ao_ref refd; gcc_assert (!chain_ovfl); - refd.base = get_ref_base_and_extent (ref, &refd.offset, &refd.size, - &refd.max_size); - chain = walk_aliased_vdefs (ref, gimple_vuse (stmt), + ao_ref_init (&refd, ref); + chain = walk_aliased_vdefs (&refd, gimple_vuse (stmt), mark_aliased_reaching_defs_necessary_1, - &refd, NULL); + gimple_bb (stmt), NULL); if (chain > longest_chain) longest_chain = chain; total_chain += chain; + nr_walks++; } /* Worker for the walker that marks reaching definitions of REF, which @@ -532,8 +568,8 @@ mark_aliased_reaching_defs_necessary (gimple stmt, tree ref) a non-aliased decl. */ static bool -mark_all_reaching_defs_necessary_1 (tree ref ATTRIBUTE_UNUSED, - tree vdef, void *data ATTRIBUTE_UNUSED) +mark_all_reaching_defs_necessary_1 (ao_ref *ref ATTRIBUTE_UNUSED, + tree vdef, void *data ATTRIBUTE_UNUSED) { gimple def_stmt = SSA_NAME_DEF_STMT (vdef); @@ -556,9 +592,9 @@ mark_all_reaching_defs_necessary_1 (tree ref ATTRIBUTE_UNUSED, return false; } - /* But can stop after the first necessary statement. */ mark_operand_necessary (vdef); - return true; + + return false; } static void @@ -568,10 +604,23 @@ mark_all_reaching_defs_necessary (gimple stmt) mark_all_reaching_defs_necessary_1, NULL, &visited); } +/* Return true for PHI nodes with one or identical arguments + can be removed. */ +static bool +degenerate_phi_p (gimple phi) +{ + unsigned int i; + tree op = gimple_phi_arg_def (phi, 0); + for (i = 1; i < gimple_phi_num_args (phi); i++) + if (gimple_phi_arg_def (phi, i) != op) + return false; + return true; +} + /* Propagate necessity using the operands of necessary statements. Process the uses on each statement in the worklist, and add all feeding statements which contribute to the calculation of this - value to the worklist. + value to the worklist. In conservative mode, EL is NULL. */ @@ -579,7 +628,7 @@ static void propagate_necessity (struct edge_list *el) { gimple stmt; - bool aggressive = (el ? true : false); + bool aggressive = (el ? true : false); if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "\nProcessing worklist:\n"); @@ -630,7 +679,7 @@ propagate_necessity (struct edge_list *el) mark_operand_necessary (arg); } - if (aggressive) + if (aggressive && !degenerate_phi_p (stmt)) { for (k = 0; k < gimple_phi_num_args (stmt); k++) { @@ -647,7 +696,7 @@ propagate_necessity (struct edge_list *el) else { /* Propagate through the operands. Examine all the USE, VUSE and - VDEF operands in this statement. Mark all the statements + VDEF operands in this statement. Mark all the statements which feed this statement's uses as necessary. */ ssa_op_iter iter; tree use; @@ -677,18 +726,26 @@ propagate_necessity (struct edge_list *el) For 1) we mark all reaching may-defs as necessary, stopping at dominating kills. For 2) we want to mark all dominating references necessary, but non-aliased ones which we handle - in 1). Instead of doing so for each load we rely on the - worklist to eventually reach all dominating references and - instead just mark the immediately dominating references - as necessary (but skipping non-aliased ones). */ + in 1). By keeping a global visited bitmap for references + we walk for 2) we avoid quadratic behavior for those. */ if (is_gimple_call (stmt)) { + tree callee = gimple_call_fndecl (stmt); unsigned i; + /* Calls to functions that are merely acting as barriers + or that only store to memory do not make any previous + stores necessary. */ + if (callee != NULL_TREE + && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL + && (DECL_FUNCTION_CODE (callee) == BUILT_IN_MEMSET + || DECL_FUNCTION_CODE (callee) == BUILT_IN_MALLOC + || DECL_FUNCTION_CODE (callee) == BUILT_IN_FREE)) + continue; + /* Calls implicitly load from memory, their arguments - in addition may explicitly perform memory loads. - This also ensures propagation for case 2 for stores. */ + in addition may explicitly perform memory loads. */ mark_all_reaching_defs_necessary (stmt); for (i = 0; i < gimple_call_num_args (stmt); ++i) { @@ -702,7 +759,7 @@ propagate_necessity (struct edge_list *el) } else if (gimple_assign_single_p (stmt)) { - tree lhs, rhs; + tree rhs; bool rhs_aliased = false; /* If this is a load mark things necessary. */ rhs = gimple_assign_rhs1 (stmt); @@ -714,12 +771,7 @@ propagate_necessity (struct edge_list *el) else rhs_aliased = true; } - /* If this is an aliased store, mark things necessary. - This is where we make sure to propagate for case 2. */ - lhs = gimple_assign_lhs (stmt); - if (rhs_aliased - || (TREE_CODE (lhs) != SSA_NAME - && ref_may_be_aliased (lhs))) + if (rhs_aliased) mark_all_reaching_defs_necessary (stmt); } else if (gimple_code (stmt) == GIMPLE_RETURN) @@ -753,11 +805,16 @@ propagate_necessity (struct edge_list *el) gcc_unreachable (); /* If we over-used our alias oracle budget drop to simple - mode. The cost metric allows quadratic behavior up to - a constant maximal chain and after that falls back to + mode. The cost metric allows quadratic behavior + (number of uses times number of may-defs queries) up to + a constant maximal number of queries and after that falls back to super-linear complexity. */ - if (longest_chain > 256 - && total_chain > 256 * longest_chain) + if (/* Constant but quadratic for small functions. */ + total_chain > 128 * 128 + /* Linear in the number of may-defs. */ + && total_chain > 32 * longest_chain + /* Linear in the number of uses. */ + && total_chain > nr_walks * 32) { chain_ovfl = true; if (visited) @@ -767,6 +824,37 @@ propagate_necessity (struct edge_list *el) } } +/* Replace all uses of result of PHI by underlying variable and mark it + for renaming. */ + +void +mark_virtual_phi_result_for_renaming (gimple phi) +{ + bool used = false; + imm_use_iterator iter; + use_operand_p use_p; + gimple stmt; + tree result_ssa, result_var; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Marking result for renaming : "); + print_gimple_stmt (dump_file, phi, 0, TDF_SLIM); + fprintf (dump_file, "\n"); + } + + result_ssa = gimple_phi_result (phi); + result_var = SSA_NAME_VAR (result_ssa); + FOR_EACH_IMM_USE_STMT (stmt, iter, result_ssa) + { + FOR_EACH_IMM_USE_ON_STMT (use_p, iter) + SET_USE (use_p, result_var); + update_stmt (stmt); + used = true; + } + if (used) + mark_sym_for_renaming (result_var); +} /* Remove dead PHI nodes from block BB. */ @@ -788,30 +876,21 @@ remove_dead_phis (basic_block bb) very simple dead PHI removal here. */ if (!is_gimple_reg (gimple_phi_result (phi))) { - unsigned i; - tree vuse; - /* Virtual PHI nodes with one or identical arguments can be removed. */ - vuse = gimple_phi_arg_def (phi, 0); - for (i = 1; i < gimple_phi_num_args (phi); ++i) - { - if (gimple_phi_arg_def (phi, i) != vuse) - { - vuse = NULL_TREE; - break; - } - } - if (vuse != NULL_TREE) + if (degenerate_phi_p (phi)) { tree vdef = gimple_phi_result (phi); + tree vuse = gimple_phi_arg_def (phi, 0); + use_operand_p use_p; imm_use_iterator iter; gimple use_stmt; FOR_EACH_IMM_USE_STMT (use_stmt, iter, vdef) FOR_EACH_IMM_USE_ON_STMT (use_p, iter) SET_USE (use_p, vuse); - if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (vdef)) + if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (vdef) + && TREE_CODE (vuse) == SSA_NAME) SSA_NAME_OCCURS_IN_ABNORMAL_PHI (vuse) = 1; } else @@ -838,6 +917,65 @@ remove_dead_phis (basic_block bb) return something_changed; } +/* Forward edge E to respective POST_DOM_BB and update PHIs. */ + +static edge +forward_edge_to_pdom (edge e, basic_block post_dom_bb) +{ + gimple_stmt_iterator gsi; + edge e2 = NULL; + edge_iterator ei; + + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Redirecting edge %i->%i to %i\n", e->src->index, + e->dest->index, post_dom_bb->index); + + e2 = redirect_edge_and_branch (e, post_dom_bb); + cfg_altered = true; + + /* If edge was already around, no updating is neccesary. */ + if (e2 != e) + return e2; + + if (!gimple_seq_empty_p (phi_nodes (post_dom_bb))) + { + /* We are sure that for every live PHI we are seeing control dependent BB. + This means that we can pick any edge to duplicate PHI args from. */ + FOR_EACH_EDGE (e2, ei, post_dom_bb->preds) + if (e2 != e) + break; + for (gsi = gsi_start_phis (post_dom_bb); !gsi_end_p (gsi);) + { + gimple phi = gsi_stmt (gsi); + tree op; + source_location locus; + + /* PHIs for virtuals have no control dependency relation on them. + We are lost here and must force renaming of the symbol. */ + if (!is_gimple_reg (gimple_phi_result (phi))) + { + mark_virtual_phi_result_for_renaming (phi); + remove_phi_node (&gsi, true); + continue; + } + + /* Dead PHI do not imply control dependency. */ + if (!gimple_plf (phi, STMT_NECESSARY)) + { + gsi_next (&gsi); + continue; + } + + op = gimple_phi_arg_def (phi, e2->dest_idx); + locus = gimple_phi_arg_location (phi, e2->dest_idx); + add_phi_arg (phi, op, e, locus); + /* The resulting PHI if not dead can only be degenerate. */ + gcc_assert (degenerate_phi_p (phi)); + gsi_next (&gsi); + } + } + return e; +} /* Remove dead statement pointed to by iterator I. Receives the basic block BB containing I so that we don't have to look it up. */ @@ -865,71 +1003,50 @@ remove_dead_stmt (gimple_stmt_iterator *i, basic_block bb) if (is_ctrl_stmt (stmt)) { basic_block post_dom_bb; + edge e, e2; + edge_iterator ei; - /* The post dominance info has to be up-to-date. */ - gcc_assert (dom_info_state (CDI_POST_DOMINATORS) == DOM_OK); - /* Get the immediate post dominator of bb. */ post_dom_bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb); - /* There are three particularly problematical cases. - - 1. Blocks that do not have an immediate post dominator. This - can happen with infinite loops. + e = find_edge (bb, post_dom_bb); - 2. Blocks that are only post dominated by the exit block. These - can also happen for infinite loops as we create fake edges - in the dominator tree. - - 3. If the post dominator has PHI nodes we may be able to compute - the right PHI args for them. - - In each of these cases we must remove the control statement - as it may reference SSA_NAMEs which are going to be removed and - we remove all but one outgoing edge from the block. */ - if (! post_dom_bb - || post_dom_bb == EXIT_BLOCK_PTR - || phi_nodes (post_dom_bb)) - ; + /* If edge is already there, try to use it. This avoids need to update + PHI nodes. Also watch for cases where post dominator does not exists + or is exit block. These can happen for infinite loops as we create + fake edges in the dominator tree. */ + if (e) + ; + else if (! post_dom_bb || post_dom_bb == EXIT_BLOCK_PTR) + e = EDGE_SUCC (bb, 0); else - { - /* Redirect the first edge out of BB to reach POST_DOM_BB. */ - redirect_edge_and_branch (EDGE_SUCC (bb, 0), post_dom_bb); - PENDING_STMT (EDGE_SUCC (bb, 0)) = NULL; - - /* It is not sufficient to set cfg_altered below during edge - removal, in case BB has two successors and one of them - is POST_DOM_BB. */ - cfg_altered = true; - } - EDGE_SUCC (bb, 0)->probability = REG_BR_PROB_BASE; - EDGE_SUCC (bb, 0)->count = bb->count; + e = forward_edge_to_pdom (EDGE_SUCC (bb, 0), post_dom_bb); + gcc_assert (e); + e->probability = REG_BR_PROB_BASE; + e->count = bb->count; /* The edge is no longer associated with a conditional, so it does not have TRUE/FALSE flags. */ - EDGE_SUCC (bb, 0)->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE); + e->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE); /* The lone outgoing edge from BB will be a fallthru edge. */ - EDGE_SUCC (bb, 0)->flags |= EDGE_FALLTHRU; - - /* Remove the remaining the outgoing edges. */ - while (!single_succ_p (bb)) - { - /* FIXME. When we remove the edge, we modify the CFG, which - in turn modifies the dominator and post-dominator tree. - Is it safe to postpone recomputing the dominator and - post-dominator tree until the end of this pass given that - the post-dominators are used above? */ - cfg_altered = true; - remove_edge (EDGE_SUCC (bb, 1)); - } + e->flags |= EDGE_FALLTHRU; + + /* Remove the remaining outgoing edges. */ + for (ei = ei_start (bb->succs); (e2 = ei_safe_edge (ei)); ) + if (e != e2) + { + cfg_altered = true; + remove_edge (e2); + } + else + ei_next (&ei); } unlink_stmt_vdef (stmt); - gsi_remove (i, true); - release_defs (stmt); + gsi_remove (i, true); + release_defs (stmt); } - /* Eliminate unnecessary statements. Any instruction not marked as necessary contributes nothing to the program, and can be deleted. */ @@ -938,29 +1055,61 @@ eliminate_unnecessary_stmts (void) { bool something_changed = false; basic_block bb; - gimple_stmt_iterator gsi; + gimple_stmt_iterator gsi, psi; gimple stmt; tree call; + VEC (basic_block, heap) *h; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "\nEliminating unnecessary statements:\n"); clear_special_calls (); - FOR_EACH_BB (bb) + /* Walking basic blocks and statements in reverse order avoids + releasing SSA names before any other DEFs that refer to them are + released. This helps avoid loss of debug information, as we get + a chance to propagate all RHSs of removed SSAs into debug uses, + rather than only the latest ones. E.g., consider: + + x_3 = y_1 + z_2; + a_5 = x_3 - b_4; + # DEBUG a => a_5 + + If we were to release x_3 before a_5, when we reached a_5 and + tried to substitute it into the debug stmt, we'd see x_3 there, + but x_3's DEF, type, etc would have already been disconnected. + By going backwards, the debug stmt first changes to: + + # DEBUG a => x_3 - b_4 + + and then to: + + # DEBUG a => y_1 + z_2 - b_4 + + as desired. */ + gcc_assert (dom_info_available_p (CDI_DOMINATORS)); + h = get_all_dominated_blocks (CDI_DOMINATORS, single_succ (ENTRY_BLOCK_PTR)); + + while (VEC_length (basic_block, h)) { + bb = VEC_pop (basic_block, h); + /* Remove dead statements. */ - for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi);) + for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi = psi) { stmt = gsi_stmt (gsi); + psi = gsi; + gsi_prev (&psi); + stats.total++; /* If GSI is not necessary then remove it. */ if (!gimple_plf (stmt, STMT_NECESSARY)) { + if (!is_gimple_debug (stmt)) + something_changed = true; remove_dead_stmt (&gsi, bb); - something_changed = true; } else if (is_gimple_call (stmt)) { @@ -982,24 +1131,90 @@ eliminate_unnecessary_stmts (void) print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); fprintf (dump_file, "\n"); } - - push_stmt_changes (gsi_stmt_ptr (&gsi)); + gimple_call_set_lhs (stmt, NULL_TREE); maybe_clean_or_replace_eh_stmt (stmt, stmt); - pop_stmt_changes (gsi_stmt_ptr (&gsi)); + update_stmt (stmt); release_ssa_name (name); } notice_special_calls (stmt); } - gsi_next (&gsi); } - else + } + } + + VEC_free (basic_block, heap, h); + + /* Since we don't track liveness of virtual PHI nodes, it is possible that we + rendered some PHI nodes unreachable while they are still in use. + Mark them for renaming. */ + if (cfg_altered) + { + basic_block prev_bb; + + find_unreachable_blocks (); + + /* Delete all unreachable basic blocks in reverse dominator order. */ + for (bb = EXIT_BLOCK_PTR->prev_bb; bb != ENTRY_BLOCK_PTR; bb = prev_bb) + { + prev_bb = bb->prev_bb; + + if (!TEST_BIT (bb_contains_live_stmts, bb->index) + || !(bb->flags & BB_REACHABLE)) { - gsi_next (&gsi); + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + if (!is_gimple_reg (gimple_phi_result (gsi_stmt (gsi)))) + { + bool found = false; + imm_use_iterator iter; + + FOR_EACH_IMM_USE_STMT (stmt, iter, gimple_phi_result (gsi_stmt (gsi))) + { + if (!(gimple_bb (stmt)->flags & BB_REACHABLE)) + continue; + if (gimple_code (stmt) == GIMPLE_PHI + || gimple_plf (stmt, STMT_NECESSARY)) + { + found = true; + BREAK_FROM_IMM_USE_STMT (iter); + } + } + if (found) + mark_virtual_phi_result_for_renaming (gsi_stmt (gsi)); + } + + if (!(bb->flags & BB_REACHABLE)) + { + /* Speed up the removal of blocks that don't + dominate others. Walking backwards, this should + be the common case. ??? Do we need to recompute + dominators because of cfg_altered? */ + if (!MAY_HAVE_DEBUG_STMTS + || !first_dom_son (CDI_DOMINATORS, bb)) + delete_basic_block (bb); + else + { + h = get_all_dominated_blocks (CDI_DOMINATORS, bb); + + while (VEC_length (basic_block, h)) + { + bb = VEC_pop (basic_block, h); + prev_bb = bb->prev_bb; + /* Rearrangements to the CFG may have failed + to update the dominators tree, so that + formerly-dominated blocks are now + otherwise reachable. */ + if (!!(bb->flags & BB_REACHABLE)) + continue; + delete_basic_block (bb); + } + + VEC_free (basic_block, heap, h); + } + } } } } - FOR_EACH_BB (bb) { /* Remove dead PHI nodes. */ @@ -1047,6 +1262,8 @@ tree_dce_init (bool aggressive) last_stmt_necessary = sbitmap_alloc (last_basic_block); sbitmap_zero (last_stmt_necessary); + bb_contains_live_stmts = sbitmap_alloc (last_basic_block); + sbitmap_zero (bb_contains_live_stmts); } processed = sbitmap_alloc (num_ssa_names + 1); @@ -1071,6 +1288,8 @@ tree_dce_done (bool aggressive) sbitmap_free (visited_control_parents); sbitmap_free (last_stmt_necessary); + sbitmap_free (bb_contains_live_stmts); + bb_contains_live_stmts = NULL; } sbitmap_free (processed); @@ -1098,6 +1317,13 @@ perform_tree_ssa_dce (bool aggressive) struct edge_list *el = NULL; bool something_changed = 0; + /* Preheaders are needed for SCEV to work. + Simple lateches and recorded exits improve chances that loop will + proved to be finite in testcases such as in loop-15.c and loop-24.c */ + if (aggressive) + loop_optimizer_init (LOOPS_NORMAL + | LOOPS_HAVE_RECORDED_EXITS); + tree_dce_init (aggressive); if (aggressive) @@ -1117,9 +1343,14 @@ perform_tree_ssa_dce (bool aggressive) find_obviously_necessary_stmts (el); + if (aggressive) + loop_optimizer_finalize (); + longest_chain = 0; total_chain = 0; + nr_walks = 0; chain_ovfl = false; + visited = BITMAP_ALLOC (NULL); propagate_necessity (el); BITMAP_FREE (visited); @@ -1147,7 +1378,7 @@ perform_tree_ssa_dce (bool aggressive) free_edge_list (el); if (something_changed) - return (TODO_update_ssa | TODO_cleanup_cfg | TODO_ggc_collect + return (TODO_update_ssa | TODO_cleanup_cfg | TODO_ggc_collect | TODO_remove_unused_locals); else return 0;