/* Loop invariant motion. Copyright (C) 2003, 2004, 2005 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 2, 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 COPYING. If not, write to the Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "tree.h" #include "rtl.h" #include "tm_p.h" #include "hard-reg-set.h" #include "basic-block.h" #include "output.h" #include "diagnostic.h" #include "tree-flow.h" #include "tree-dump.h" #include "timevar.h" #include "cfgloop.h" #include "domwalk.h" #include "params.h" #include "tree-pass.h" #include "flags.h" #include "real.h" #include "hashtab.h" /* TODO: Support for predicated code motion. I.e. while (1) { if (cond) { a = inv; something; } } Where COND and INV are is invariants, but evaluating INV may trap or be invalid from some other reason if !COND. This may be transformed to if (cond) a = inv; while (1) { if (cond) something; } */ /* A type for the list of statements that have to be moved in order to be able to hoist an invariant computation. */ struct depend { tree stmt; struct depend *next; }; /* The auxiliary data kept for each statement. */ struct lim_aux_data { struct loop *max_loop; /* The outermost loop in that the statement is invariant. */ struct loop *tgt_loop; /* The loop out of that we want to move the invariant. */ struct loop *always_executed_in; /* The outermost loop for that we are sure the statement is executed if the loop is entered. */ bool sm_done; /* True iff the store motion for a memory reference in the statement has already been executed. */ unsigned cost; /* Cost of the computation performed by the statement. */ struct depend *depends; /* List of statements that must be also hoisted out of the loop when this statement is hoisted; i.e. those that define the operands of the statement and are inside of the MAX_LOOP loop. */ }; #define LIM_DATA(STMT) (TREE_CODE (STMT) == PHI_NODE \ ? NULL \ : (struct lim_aux_data *) (stmt_ann (STMT)->common.aux)) /* Description of a memory reference location for store motion. */ struct mem_ref_loc { tree *ref; /* The reference itself. */ tree stmt; /* The statement in that it occurs. */ struct mem_ref_loc *next; /* Next use in the chain. */ }; /* Description of a memory reference for store motion. */ struct mem_ref { tree mem; /* The memory itself. */ hashval_t hash; /* Its hash value. */ bool is_stored; /* True if there is a store to the location in the loop. */ struct mem_ref_loc *locs; /* The locations where it is found. */ bitmap vops; /* Vops corresponding to this memory location. */ struct mem_ref *next; /* Next memory reference in the list. Memory references are stored in a hash table, but the hash function depends on values of pointers. Thus we cannot use htab_traverse, since then we would get miscompares during bootstrap (although the produced code would be correct). */ }; /* Minimum cost of an expensive expression. */ #define LIM_EXPENSIVE ((unsigned) PARAM_VALUE (PARAM_LIM_EXPENSIVE)) /* The outermost loop for that execution of the header guarantees that the block will be executed. */ #define ALWAYS_EXECUTED_IN(BB) ((struct loop *) (BB)->aux) /* Calls CBCK for each index in memory reference ADDR_P. There are two kinds situations handled; in each of these cases, the memory reference and DATA are passed to the callback: Access to an array: ARRAY_{RANGE_}REF (base, index). In this case we also pass the pointer to the index to the callback. Pointer dereference: INDIRECT_REF (addr). In this case we also pass the pointer to addr to the callback. If the callback returns false, the whole search stops and false is returned. Otherwise the function returns true after traversing through the whole reference *ADDR_P. */ bool for_each_index (tree *addr_p, bool (*cbck) (tree, tree *, void *), void *data) { tree *nxt, *idx; for (; ; addr_p = nxt) { switch (TREE_CODE (*addr_p)) { case SSA_NAME: return cbck (*addr_p, addr_p, data); case MISALIGNED_INDIRECT_REF: case ALIGN_INDIRECT_REF: case INDIRECT_REF: nxt = &TREE_OPERAND (*addr_p, 0); return cbck (*addr_p, nxt, data); case BIT_FIELD_REF: case VIEW_CONVERT_EXPR: case REALPART_EXPR: case IMAGPART_EXPR: nxt = &TREE_OPERAND (*addr_p, 0); break; case COMPONENT_REF: /* If the component has varying offset, it behaves like index as well. */ idx = &TREE_OPERAND (*addr_p, 2); if (*idx && !cbck (*addr_p, idx, data)) return false; nxt = &TREE_OPERAND (*addr_p, 0); break; case ARRAY_REF: case ARRAY_RANGE_REF: nxt = &TREE_OPERAND (*addr_p, 0); if (!cbck (*addr_p, &TREE_OPERAND (*addr_p, 1), data)) return false; break; case VAR_DECL: case PARM_DECL: case STRING_CST: case RESULT_DECL: case VECTOR_CST: case COMPLEX_CST: case INTEGER_CST: case REAL_CST: return true; case TARGET_MEM_REF: idx = &TMR_BASE (*addr_p); if (*idx && !cbck (*addr_p, idx, data)) return false; idx = &TMR_INDEX (*addr_p); if (*idx && !cbck (*addr_p, idx, data)) return false; return true; default: gcc_unreachable (); } } } /* If it is possible to hoist the statement STMT unconditionally, returns MOVE_POSSIBLE. If it is possible to hoist the statement STMT, but we must avoid making it executed if it would not be executed in the original program (e.g. because it may trap), return MOVE_PRESERVE_EXECUTION. Otherwise return MOVE_IMPOSSIBLE. */ enum move_pos movement_possibility (tree stmt) { tree lhs, rhs; if (flag_unswitch_loops && TREE_CODE (stmt) == COND_EXPR) { /* If we perform unswitching, force the operands of the invariant condition to be moved out of the loop. */ return MOVE_POSSIBLE; } if (TREE_CODE (stmt) != MODIFY_EXPR) return MOVE_IMPOSSIBLE; if (stmt_ends_bb_p (stmt)) return MOVE_IMPOSSIBLE; if (stmt_ann (stmt)->has_volatile_ops) return MOVE_IMPOSSIBLE; lhs = TREE_OPERAND (stmt, 0); if (TREE_CODE (lhs) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs)) return MOVE_IMPOSSIBLE; rhs = TREE_OPERAND (stmt, 1); if (TREE_SIDE_EFFECTS (rhs)) return MOVE_IMPOSSIBLE; if (TREE_CODE (lhs) != SSA_NAME || tree_could_trap_p (rhs)) return MOVE_PRESERVE_EXECUTION; if (get_call_expr_in (stmt)) { /* While pure or const call is guaranteed to have no side effects, we cannot move it arbitrarily. Consider code like char *s = something (); while (1) { if (s) t = strlen (s); else t = 0; } Here the strlen call cannot be moved out of the loop, even though s is invariant. In addition to possibly creating a call with invalid arguments, moving out a function call that is not executed may cause performance regressions in case the call is costly and not executed at all. */ return MOVE_PRESERVE_EXECUTION; } return MOVE_POSSIBLE; } /* Suppose that operand DEF is used inside the LOOP. Returns the outermost loop to that we could move the expression using DEF if it did not have other operands, i.e. the outermost loop enclosing LOOP in that the value of DEF is invariant. */ static struct loop * outermost_invariant_loop (tree def, struct loop *loop) { tree def_stmt; basic_block def_bb; struct loop *max_loop; if (TREE_CODE (def) != SSA_NAME) return superloop_at_depth (loop, 1); def_stmt = SSA_NAME_DEF_STMT (def); def_bb = bb_for_stmt (def_stmt); if (!def_bb) return superloop_at_depth (loop, 1); max_loop = find_common_loop (loop, def_bb->loop_father); if (LIM_DATA (def_stmt) && LIM_DATA (def_stmt)->max_loop) max_loop = find_common_loop (max_loop, LIM_DATA (def_stmt)->max_loop->outer); if (max_loop == loop) return NULL; max_loop = superloop_at_depth (loop, max_loop->depth + 1); return max_loop; } /* Returns the outermost superloop of LOOP in that the expression EXPR is invariant. */ static struct loop * outermost_invariant_loop_expr (tree expr, struct loop *loop) { enum tree_code_class class = TREE_CODE_CLASS (TREE_CODE (expr)); unsigned i, nops; struct loop *max_loop = superloop_at_depth (loop, 1), *aloop; if (TREE_CODE (expr) == SSA_NAME || TREE_CODE (expr) == INTEGER_CST || is_gimple_min_invariant (expr)) return outermost_invariant_loop (expr, loop); if (class != tcc_unary && class != tcc_binary && class != tcc_expression && class != tcc_comparison) return NULL; nops = TREE_CODE_LENGTH (TREE_CODE (expr)); for (i = 0; i < nops; i++) { aloop = outermost_invariant_loop_expr (TREE_OPERAND (expr, i), loop); if (!aloop) return NULL; if (flow_loop_nested_p (max_loop, aloop)) max_loop = aloop; } return max_loop; } /* DATA is a structure containing information associated with a statement inside LOOP. DEF is one of the operands of this statement. Find the outermost loop enclosing LOOP in that value of DEF is invariant and record this in DATA->max_loop field. If DEF itself is defined inside this loop as well (i.e. we need to hoist it out of the loop if we want to hoist the statement represented by DATA), record the statement in that DEF is defined to the DATA->depends list. Additionally if ADD_COST is true, add the cost of the computation of DEF to the DATA->cost. If DEF is not invariant in LOOP, return false. Otherwise return TRUE. */ static bool add_dependency (tree def, struct lim_aux_data *data, struct loop *loop, bool add_cost) { tree def_stmt = SSA_NAME_DEF_STMT (def); basic_block def_bb = bb_for_stmt (def_stmt); struct loop *max_loop; struct depend *dep; if (!def_bb) return true; max_loop = outermost_invariant_loop (def, loop); if (!max_loop) return false; if (flow_loop_nested_p (data->max_loop, max_loop)) data->max_loop = max_loop; if (!LIM_DATA (def_stmt)) return true; if (add_cost /* Only add the cost if the statement defining DEF is inside LOOP, i.e. if it is likely that by moving the invariants dependent on it, we will be able to avoid creating a new register for it (since it will be only used in these dependent invariants). */ && def_bb->loop_father == loop) data->cost += LIM_DATA (def_stmt)->cost; dep = XNEW (struct depend); dep->stmt = def_stmt; dep->next = data->depends; data->depends = dep; return true; } /* Returns an estimate for a cost of statement STMT. TODO -- the values here are just ad-hoc constants. The estimates should be based on target-specific values. */ static unsigned stmt_cost (tree stmt) { tree rhs; unsigned cost = 1; /* Always try to create possibilities for unswitching. */ if (TREE_CODE (stmt) == COND_EXPR) return LIM_EXPENSIVE; rhs = TREE_OPERAND (stmt, 1); /* Hoisting memory references out should almost surely be a win. */ if (stmt_references_memory_p (stmt)) cost += 20; switch (TREE_CODE (rhs)) { case CALL_EXPR: /* We should be hoisting calls if possible. */ /* Unless the call is a builtin_constant_p; this always folds to a constant, so moving it is useless. */ rhs = get_callee_fndecl (rhs); if (DECL_BUILT_IN_CLASS (rhs) == BUILT_IN_NORMAL && DECL_FUNCTION_CODE (rhs) == BUILT_IN_CONSTANT_P) return 0; cost += 20; break; case MULT_EXPR: case TRUNC_DIV_EXPR: case CEIL_DIV_EXPR: case FLOOR_DIV_EXPR: case ROUND_DIV_EXPR: case EXACT_DIV_EXPR: case CEIL_MOD_EXPR: case FLOOR_MOD_EXPR: case ROUND_MOD_EXPR: case TRUNC_MOD_EXPR: case RDIV_EXPR: /* Division and multiplication are usually expensive. */ cost += 20; break; default: break; } return cost; } /* Determine the outermost loop to that it is possible to hoist a statement STMT and store it to LIM_DATA (STMT)->max_loop. To do this we determine the outermost loop in that the value computed by STMT is invariant. If MUST_PRESERVE_EXEC is true, additionally choose such a loop that we preserve the fact whether STMT is executed. It also fills other related information to LIM_DATA (STMT). The function returns false if STMT cannot be hoisted outside of the loop it is defined in, and true otherwise. */ static bool determine_max_movement (tree stmt, bool must_preserve_exec) { basic_block bb = bb_for_stmt (stmt); struct loop *loop = bb->loop_father; struct loop *level; struct lim_aux_data *lim_data = LIM_DATA (stmt); tree val; ssa_op_iter iter; if (must_preserve_exec) level = ALWAYS_EXECUTED_IN (bb); else level = superloop_at_depth (loop, 1); lim_data->max_loop = level; FOR_EACH_SSA_TREE_OPERAND (val, stmt, iter, SSA_OP_USE) if (!add_dependency (val, lim_data, loop, true)) return false; FOR_EACH_SSA_TREE_OPERAND (val, stmt, iter, SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS) if (!add_dependency (val, lim_data, loop, false)) return false; lim_data->cost += stmt_cost (stmt); return true; } /* Suppose that some statement in ORIG_LOOP is hoisted to the loop LEVEL, and that one of the operands of this statement is computed by STMT. Ensure that STMT (together with all the statements that define its operands) is hoisted at least out of the loop LEVEL. */ static void set_level (tree stmt, struct loop *orig_loop, struct loop *level) { struct loop *stmt_loop = bb_for_stmt (stmt)->loop_father; struct depend *dep; stmt_loop = find_common_loop (orig_loop, stmt_loop); if (LIM_DATA (stmt) && LIM_DATA (stmt)->tgt_loop) stmt_loop = find_common_loop (stmt_loop, LIM_DATA (stmt)->tgt_loop->outer); if (flow_loop_nested_p (stmt_loop, level)) return; gcc_assert (LIM_DATA (stmt)); gcc_assert (level == LIM_DATA (stmt)->max_loop || flow_loop_nested_p (LIM_DATA (stmt)->max_loop, level)); LIM_DATA (stmt)->tgt_loop = level; for (dep = LIM_DATA (stmt)->depends; dep; dep = dep->next) set_level (dep->stmt, orig_loop, level); } /* Determines an outermost loop from that we want to hoist the statement STMT. For now we chose the outermost possible loop. TODO -- use profiling information to set it more sanely. */ static void set_profitable_level (tree stmt) { set_level (stmt, bb_for_stmt (stmt)->loop_father, LIM_DATA (stmt)->max_loop); } /* Returns true if STMT is not a pure call. */ static bool nonpure_call_p (tree stmt) { tree call = get_call_expr_in (stmt); if (!call) return false; return TREE_SIDE_EFFECTS (call) != 0; } /* Releases the memory occupied by DATA. */ static void free_lim_aux_data (struct lim_aux_data *data) { struct depend *dep, *next; for (dep = data->depends; dep; dep = next) { next = dep->next; free (dep); } free (data); } /* Determine the outermost loops in that statements in basic block BB are invariant, and record them to the LIM_DATA associated with the statements. Callback for walk_dominator_tree. */ static void determine_invariantness_stmt (struct dom_walk_data *dw_data ATTRIBUTE_UNUSED, basic_block bb) { enum move_pos pos; block_stmt_iterator bsi; tree stmt, rhs; bool maybe_never = ALWAYS_EXECUTED_IN (bb) == NULL; struct loop *outermost = ALWAYS_EXECUTED_IN (bb); if (!bb->loop_father->outer) return; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Basic block %d (loop %d -- depth %d):\n\n", bb->index, bb->loop_father->num, bb->loop_father->depth); for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { stmt = bsi_stmt (bsi); pos = movement_possibility (stmt); if (pos == MOVE_IMPOSSIBLE) { if (nonpure_call_p (stmt)) { maybe_never = true; outermost = NULL; } continue; } /* If divisor is invariant, convert a/b to a*(1/b), allowing reciprocal to be hoisted out of loop, saving expensive divide. */ if (pos == MOVE_POSSIBLE && (rhs = TREE_OPERAND (stmt, 1)) != NULL && TREE_CODE (rhs) == RDIV_EXPR && flag_unsafe_math_optimizations && !flag_trapping_math && outermost_invariant_loop_expr (TREE_OPERAND (rhs, 1), loop_containing_stmt (stmt)) != NULL && outermost_invariant_loop_expr (rhs, loop_containing_stmt (stmt)) == NULL) { tree lhs, stmt1, stmt2, var, name; lhs = TREE_OPERAND (stmt, 0); /* stmt must be MODIFY_EXPR. */ var = create_tmp_var (TREE_TYPE (rhs), "reciptmp"); add_referenced_var (var); stmt1 = build2 (MODIFY_EXPR, void_type_node, var, build2 (RDIV_EXPR, TREE_TYPE (rhs), build_real (TREE_TYPE (rhs), dconst1), TREE_OPERAND (rhs, 1))); name = make_ssa_name (var, stmt1); TREE_OPERAND (stmt1, 0) = name; stmt2 = build2 (MODIFY_EXPR, void_type_node, lhs, build2 (MULT_EXPR, TREE_TYPE (rhs), name, TREE_OPERAND (rhs, 0))); /* Replace division stmt with reciprocal and multiply stmts. The multiply stmt is not invariant, so update iterator and avoid rescanning. */ bsi_replace (&bsi, stmt1, true); bsi_insert_after (&bsi, stmt2, BSI_NEW_STMT); SSA_NAME_DEF_STMT (lhs) = stmt2; /* Continue processing with invariant reciprocal statement. */ stmt = stmt1; } stmt_ann (stmt)->common.aux = xcalloc (1, sizeof (struct lim_aux_data)); LIM_DATA (stmt)->always_executed_in = outermost; if (maybe_never && pos == MOVE_PRESERVE_EXECUTION) continue; if (!determine_max_movement (stmt, pos == MOVE_PRESERVE_EXECUTION)) { LIM_DATA (stmt)->max_loop = NULL; continue; } if (dump_file && (dump_flags & TDF_DETAILS)) { print_generic_stmt_indented (dump_file, stmt, 0, 2); fprintf (dump_file, " invariant up to level %d, cost %d.\n\n", LIM_DATA (stmt)->max_loop->depth, LIM_DATA (stmt)->cost); } if (LIM_DATA (stmt)->cost >= LIM_EXPENSIVE) set_profitable_level (stmt); } } /* For each statement determines the outermost loop in that it is invariant, statements on whose motion it depends and the cost of the computation. This information is stored to the LIM_DATA structure associated with each statement. */ static void determine_invariantness (void) { struct dom_walk_data walk_data; memset (&walk_data, 0, sizeof (struct dom_walk_data)); walk_data.before_dom_children_before_stmts = determine_invariantness_stmt; init_walk_dominator_tree (&walk_data); walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR); fini_walk_dominator_tree (&walk_data); } /* Commits edge insertions and updates loop structures. */ void loop_commit_inserts (void) { unsigned old_last_basic_block, i; basic_block bb; old_last_basic_block = last_basic_block; bsi_commit_edge_inserts (); for (i = old_last_basic_block; i < (unsigned) last_basic_block; i++) { bb = BASIC_BLOCK (i); add_bb_to_loop (bb, find_common_loop (single_pred (bb)->loop_father, single_succ (bb)->loop_father)); } } /* Hoist the statements in basic block BB out of the loops prescribed by data stored in LIM_DATA structures associated with each statement. Callback for walk_dominator_tree. */ static void move_computations_stmt (struct dom_walk_data *dw_data ATTRIBUTE_UNUSED, basic_block bb) { struct loop *level; block_stmt_iterator bsi; tree stmt; unsigned cost = 0; if (!bb->loop_father->outer) return; for (bsi = bsi_start (bb); !bsi_end_p (bsi); ) { stmt = bsi_stmt (bsi); if (!LIM_DATA (stmt)) { bsi_next (&bsi); continue; } cost = LIM_DATA (stmt)->cost; level = LIM_DATA (stmt)->tgt_loop; free_lim_aux_data (LIM_DATA (stmt)); stmt_ann (stmt)->common.aux = NULL; if (!level) { bsi_next (&bsi); continue; } /* We do not really want to move conditionals out of the loop; we just placed it here to force its operands to be moved if necessary. */ if (TREE_CODE (stmt) == COND_EXPR) continue; if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Moving statement\n"); print_generic_stmt (dump_file, stmt, 0); fprintf (dump_file, "(cost %u) out of loop %d.\n\n", cost, level->num); } bsi_insert_on_edge (loop_preheader_edge (level), stmt); bsi_remove (&bsi, false); } } /* Hoist the statements out of the loops prescribed by data stored in LIM_DATA structures associated with each statement.*/ static void move_computations (void) { struct dom_walk_data walk_data; memset (&walk_data, 0, sizeof (struct dom_walk_data)); walk_data.before_dom_children_before_stmts = move_computations_stmt; init_walk_dominator_tree (&walk_data); walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR); fini_walk_dominator_tree (&walk_data); loop_commit_inserts (); if (need_ssa_update_p ()) rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa); } /* Checks whether the statement defining variable *INDEX can be hoisted out of the loop passed in DATA. Callback for for_each_index. */ static bool may_move_till (tree ref, tree *index, void *data) { struct loop *loop = data, *max_loop; /* If REF is an array reference, check also that the step and the lower bound is invariant in LOOP. */ if (TREE_CODE (ref) == ARRAY_REF) { tree step = array_ref_element_size (ref); tree lbound = array_ref_low_bound (ref); max_loop = outermost_invariant_loop_expr (step, loop); if (!max_loop) return false; max_loop = outermost_invariant_loop_expr (lbound, loop); if (!max_loop) return false; } max_loop = outermost_invariant_loop (*index, loop); if (!max_loop) return false; return true; } /* Forces statements defining (invariant) SSA names in expression EXPR to be moved out of the LOOP. ORIG_LOOP is the loop in that EXPR is used. */ static void force_move_till_expr (tree expr, struct loop *orig_loop, struct loop *loop) { enum tree_code_class class = TREE_CODE_CLASS (TREE_CODE (expr)); unsigned i, nops; if (TREE_CODE (expr) == SSA_NAME) { tree stmt = SSA_NAME_DEF_STMT (expr); if (IS_EMPTY_STMT (stmt)) return; set_level (stmt, orig_loop, loop); return; } if (class != tcc_unary && class != tcc_binary && class != tcc_expression && class != tcc_comparison) return; nops = TREE_CODE_LENGTH (TREE_CODE (expr)); for (i = 0; i < nops; i++) force_move_till_expr (TREE_OPERAND (expr, i), orig_loop, loop); } /* Forces statement defining invariants in REF (and *INDEX) to be moved out of the LOOP. The reference REF is used in the loop ORIG_LOOP. Callback for for_each_index. */ struct fmt_data { struct loop *loop; struct loop *orig_loop; }; static bool force_move_till (tree ref, tree *index, void *data) { tree stmt; struct fmt_data *fmt_data = data; if (TREE_CODE (ref) == ARRAY_REF) { tree step = array_ref_element_size (ref); tree lbound = array_ref_low_bound (ref); force_move_till_expr (step, fmt_data->orig_loop, fmt_data->loop); force_move_till_expr (lbound, fmt_data->orig_loop, fmt_data->loop); } if (TREE_CODE (*index) != SSA_NAME) return true; stmt = SSA_NAME_DEF_STMT (*index); if (IS_EMPTY_STMT (stmt)) return true; set_level (stmt, fmt_data->orig_loop, fmt_data->loop); return true; } /* Records memory reference location *REF to the list MEM_REFS. The reference occurs in statement STMT. */ static void record_mem_ref_loc (struct mem_ref_loc **mem_refs, tree stmt, tree *ref) { struct mem_ref_loc *aref = XNEW (struct mem_ref_loc); aref->stmt = stmt; aref->ref = ref; aref->next = *mem_refs; *mem_refs = aref; } /* Releases list of memory reference locations MEM_REFS. */ static void free_mem_ref_locs (struct mem_ref_loc *mem_refs) { struct mem_ref_loc *act; while (mem_refs) { act = mem_refs; mem_refs = mem_refs->next; free (act); } } /* Rewrites memory references in list MEM_REFS by variable TMP_VAR. */ static void rewrite_mem_refs (tree tmp_var, struct mem_ref_loc *mem_refs) { tree var; ssa_op_iter iter; for (; mem_refs; mem_refs = mem_refs->next) { FOR_EACH_SSA_TREE_OPERAND (var, mem_refs->stmt, iter, SSA_OP_ALL_VIRTUALS) mark_sym_for_renaming (SSA_NAME_VAR (var)); *mem_refs->ref = tmp_var; update_stmt (mem_refs->stmt); } } /* The name and the length of the currently generated variable for lsm. */ #define MAX_LSM_NAME_LENGTH 40 static char lsm_tmp_name[MAX_LSM_NAME_LENGTH + 1]; static int lsm_tmp_name_length; /* Adds S to lsm_tmp_name. */ static void lsm_tmp_name_add (const char *s) { int l = strlen (s) + lsm_tmp_name_length; if (l > MAX_LSM_NAME_LENGTH) return; strcpy (lsm_tmp_name + lsm_tmp_name_length, s); lsm_tmp_name_length = l; } /* Stores the name for temporary variable that replaces REF to lsm_tmp_name. */ static void gen_lsm_tmp_name (tree ref) { const char *name; switch (TREE_CODE (ref)) { case MISALIGNED_INDIRECT_REF: case ALIGN_INDIRECT_REF: case INDIRECT_REF: gen_lsm_tmp_name (TREE_OPERAND (ref, 0)); lsm_tmp_name_add ("_"); break; case BIT_FIELD_REF: case VIEW_CONVERT_EXPR: case ARRAY_RANGE_REF: gen_lsm_tmp_name (TREE_OPERAND (ref, 0)); break; case REALPART_EXPR: gen_lsm_tmp_name (TREE_OPERAND (ref, 0)); lsm_tmp_name_add ("_RE"); break; case IMAGPART_EXPR: gen_lsm_tmp_name (TREE_OPERAND (ref, 0)); lsm_tmp_name_add ("_IM"); break; case COMPONENT_REF: gen_lsm_tmp_name (TREE_OPERAND (ref, 0)); lsm_tmp_name_add ("_"); name = get_name (TREE_OPERAND (ref, 1)); if (!name) name = "F"; lsm_tmp_name_add ("_"); lsm_tmp_name_add (name); case ARRAY_REF: gen_lsm_tmp_name (TREE_OPERAND (ref, 0)); lsm_tmp_name_add ("_I"); break; case SSA_NAME: ref = SSA_NAME_VAR (ref); /* Fallthru. */ case VAR_DECL: case PARM_DECL: name = get_name (ref); if (!name) name = "D"; lsm_tmp_name_add (name); break; case STRING_CST: lsm_tmp_name_add ("S"); break; case RESULT_DECL: lsm_tmp_name_add ("R"); break; default: gcc_unreachable (); } } /* Determines name for temporary variable that replaces REF. The name is accumulated into the lsm_tmp_name variable. */ static char * get_lsm_tmp_name (tree ref) { lsm_tmp_name_length = 0; gen_lsm_tmp_name (ref); lsm_tmp_name_add ("_lsm"); return lsm_tmp_name; } /* Records request for store motion of memory reference REF from LOOP. MEM_REFS is the list of occurrences of the reference REF inside LOOP; these references are rewritten by a new temporary variable. Exits from the LOOP are stored in EXITS, there are N_EXITS of them. The initialization of the temporary variable is put to the preheader of the loop, and assignments to the reference from the temporary variable are emitted to exits. */ static void schedule_sm (struct loop *loop, edge *exits, unsigned n_exits, tree ref, struct mem_ref_loc *mem_refs) { struct mem_ref_loc *aref; tree tmp_var; unsigned i; tree load, store; struct fmt_data fmt_data; if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Executing store motion of "); print_generic_expr (dump_file, ref, 0); fprintf (dump_file, " from loop %d\n", loop->num); } tmp_var = make_rename_temp (TREE_TYPE (ref), get_lsm_tmp_name (ref)); fmt_data.loop = loop; fmt_data.orig_loop = loop; for_each_index (&ref, force_move_till, &fmt_data); rewrite_mem_refs (tmp_var, mem_refs); for (aref = mem_refs; aref; aref = aref->next) if (LIM_DATA (aref->stmt)) LIM_DATA (aref->stmt)->sm_done = true; /* Emit the load & stores. */ load = build2 (MODIFY_EXPR, void_type_node, tmp_var, ref); get_stmt_ann (load)->common.aux = xcalloc (1, sizeof (struct lim_aux_data)); LIM_DATA (load)->max_loop = loop; LIM_DATA (load)->tgt_loop = loop; /* Put this into the latch, so that we are sure it will be processed after all dependencies. */ bsi_insert_on_edge (loop_latch_edge (loop), load); for (i = 0; i < n_exits; i++) { store = build2 (MODIFY_EXPR, void_type_node, unshare_expr (ref), tmp_var); bsi_insert_on_edge (exits[i], store); } } /* Check whether memory reference REF can be hoisted out of the LOOP. If this is true, prepare the statements that load the value of the memory reference to a temporary variable in the loop preheader, store it back on the loop exits, and replace all the references inside LOOP by this temporary variable. LOOP has N_EXITS stored in EXITS. CLOBBERED_VOPS is the bitmap of virtual operands that are clobbered by a call or accessed through multiple references in loop. */ static void determine_lsm_ref (struct loop *loop, edge *exits, unsigned n_exits, bitmap clobbered_vops, struct mem_ref *ref) { struct mem_ref_loc *aref; struct loop *must_exec; /* In case the memory is not stored to, there is nothing for SM to do. */ if (!ref->is_stored) return; /* If the reference is aliased with any different ref, or killed by call in function, then fail. */ if (bitmap_intersect_p (ref->vops, clobbered_vops)) return; if (tree_could_trap_p (ref->mem)) { /* If the memory access is unsafe (i.e. it might trap), ensure that some of the statements in that it occurs is always executed when the loop is entered. This way we know that by moving the load from the reference out of the loop we will not cause the error that would not occur otherwise. TODO -- in fact we would like to check for anticipability of the reference, i.e. that on each path from loop entry to loop exit at least one of the statements containing the memory reference is executed. */ for (aref = ref->locs; aref; aref = aref->next) { if (!LIM_DATA (aref->stmt)) continue; must_exec = LIM_DATA (aref->stmt)->always_executed_in; if (!must_exec) continue; if (must_exec == loop || flow_loop_nested_p (must_exec, loop)) break; } if (!aref) return; } schedule_sm (loop, exits, n_exits, ref->mem, ref->locs); } /* Hoists memory references MEM_REFS out of LOOP. CLOBBERED_VOPS is the list of vops clobbered by call in loop or accessed by multiple memory references. EXITS is the list of N_EXITS exit edges of the LOOP. */ static void hoist_memory_references (struct loop *loop, struct mem_ref *mem_refs, bitmap clobbered_vops, edge *exits, unsigned n_exits) { struct mem_ref *ref; for (ref = mem_refs; ref; ref = ref->next) determine_lsm_ref (loop, exits, n_exits, clobbered_vops, ref); } /* Checks whether LOOP (with N_EXITS exits stored in EXITS array) is suitable for a store motion optimization (i.e. whether we can insert statement on its exits). */ static bool loop_suitable_for_sm (struct loop *loop ATTRIBUTE_UNUSED, edge *exits, unsigned n_exits) { unsigned i; for (i = 0; i < n_exits; i++) if (exits[i]->flags & EDGE_ABNORMAL) return false; return true; } /* A hash function for struct mem_ref object OBJ. */ static hashval_t memref_hash (const void *obj) { const struct mem_ref *mem = obj; return mem->hash; } /* An equality function for struct mem_ref object OBJ1 with memory reference OBJ2. */ static int memref_eq (const void *obj1, const void *obj2) { const struct mem_ref *mem1 = obj1; return operand_equal_p (mem1->mem, (tree) obj2, 0); } /* Gathers memory references in statement STMT in LOOP, storing the information about them in MEM_REFS hash table. Note vops accessed through unrecognized statements in CLOBBERED_VOPS. The newly created references are also stored to MEM_REF_LIST. */ static void gather_mem_refs_stmt (struct loop *loop, htab_t mem_refs, bitmap clobbered_vops, tree stmt, struct mem_ref **mem_ref_list) { tree *lhs, *rhs, *mem = NULL; hashval_t hash; PTR *slot; struct mem_ref *ref = NULL; ssa_op_iter oi; tree vname; bool is_stored; if (ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS)) return; /* Recognize MEM = (SSA_NAME | invariant) and SSA_NAME = MEM patterns. */ if (TREE_CODE (stmt) != MODIFY_EXPR) goto fail; lhs = &TREE_OPERAND (stmt, 0); rhs = &TREE_OPERAND (stmt, 1); if (TREE_CODE (*lhs) == SSA_NAME) { if (!is_gimple_addressable (*rhs)) goto fail; mem = rhs; is_stored = false; } else if (TREE_CODE (*rhs) == SSA_NAME || is_gimple_min_invariant (*rhs)) { mem = lhs; is_stored = true; } else goto fail; /* If we cannot create an SSA name for the result, give up. */ if (!is_gimple_reg_type (TREE_TYPE (*mem)) || TREE_THIS_VOLATILE (*mem)) goto fail; /* If we cannot move the reference out of the loop, fail. */ if (!for_each_index (mem, may_move_till, loop)) goto fail; hash = iterative_hash_expr (*mem, 0); slot = htab_find_slot_with_hash (mem_refs, *mem, hash, INSERT); if (*slot) ref = *slot; else { ref = XNEW (struct mem_ref); ref->mem = *mem; ref->hash = hash; ref->locs = NULL; ref->is_stored = false; ref->vops = BITMAP_ALLOC (NULL); ref->next = *mem_ref_list; *mem_ref_list = ref; *slot = ref; } ref->is_stored |= is_stored; FOR_EACH_SSA_TREE_OPERAND (vname, stmt, oi, SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS) bitmap_set_bit (ref->vops, DECL_UID (SSA_NAME_VAR (vname))); record_mem_ref_loc (&ref->locs, stmt, mem); return; fail: FOR_EACH_SSA_TREE_OPERAND (vname, stmt, oi, SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS) bitmap_set_bit (clobbered_vops, DECL_UID (SSA_NAME_VAR (vname))); } /* Gathers memory references in LOOP. Notes vops accessed through unrecognized statements in CLOBBERED_VOPS. The list of the references found by the function is returned. */ static struct mem_ref * gather_mem_refs (struct loop *loop, bitmap clobbered_vops) { basic_block *body = get_loop_body (loop); block_stmt_iterator bsi; unsigned i; struct mem_ref *mem_ref_list = NULL; htab_t mem_refs = htab_create (100, memref_hash, memref_eq, NULL); for (i = 0; i < loop->num_nodes; i++) { for (bsi = bsi_start (body[i]); !bsi_end_p (bsi); bsi_next (&bsi)) gather_mem_refs_stmt (loop, mem_refs, clobbered_vops, bsi_stmt (bsi), &mem_ref_list); } free (body); htab_delete (mem_refs); return mem_ref_list; } /* Finds the vops accessed by more than one of the memory references described in MEM_REFS and marks them in CLOBBERED_VOPS. */ static void find_more_ref_vops (struct mem_ref *mem_refs, bitmap clobbered_vops) { bitmap_head tmp, all_vops; struct mem_ref *ref; bitmap_initialize (&tmp, &bitmap_default_obstack); bitmap_initialize (&all_vops, &bitmap_default_obstack); for (ref = mem_refs; ref; ref = ref->next) { /* The vops that are already in all_vops are accessed by more than one memory reference. */ bitmap_and (&tmp, &all_vops, ref->vops); bitmap_ior_into (clobbered_vops, &tmp); bitmap_clear (&tmp); bitmap_ior_into (&all_vops, ref->vops); } bitmap_clear (&all_vops); } /* Releases the memory occupied by REF. */ static void free_mem_ref (struct mem_ref *ref) { free_mem_ref_locs (ref->locs); BITMAP_FREE (ref->vops); free (ref); } /* Releases the memory occupied by REFS. */ static void free_mem_refs (struct mem_ref *refs) { struct mem_ref *ref, *next; for (ref = refs; ref; ref = next) { next = ref->next; free_mem_ref (ref); } } /* Try to perform store motion for all memory references modified inside LOOP. */ static void determine_lsm_loop (struct loop *loop) { unsigned n_exits; edge *exits = get_loop_exit_edges (loop, &n_exits); bitmap clobbered_vops; struct mem_ref *mem_refs; if (!loop_suitable_for_sm (loop, exits, n_exits)) { free (exits); return; } /* Find the memory references in LOOP. */ clobbered_vops = BITMAP_ALLOC (NULL); mem_refs = gather_mem_refs (loop, clobbered_vops); /* Find the vops that are used for more than one reference. */ find_more_ref_vops (mem_refs, clobbered_vops); /* Hoist all suitable memory references. */ hoist_memory_references (loop, mem_refs, clobbered_vops, exits, n_exits); free_mem_refs (mem_refs); free (exits); BITMAP_FREE (clobbered_vops); } /* Try to perform store motion for all memory references modified inside any of LOOPS. */ static void determine_lsm (struct loops *loops) { struct loop *loop; if (!loops->tree_root->inner) return; /* Pass the loops from the outermost and perform the store motion as suitable. */ loop = loops->tree_root->inner; while (1) { determine_lsm_loop (loop); if (loop->inner) { loop = loop->inner; continue; } while (!loop->next) { loop = loop->outer; if (loop == loops->tree_root) { loop_commit_inserts (); return; } } loop = loop->next; } } /* Fills ALWAYS_EXECUTED_IN information for basic blocks of LOOP, i.e. for each such basic block bb records the outermost loop for that execution of its header implies execution of bb. CONTAINS_CALL is the bitmap of blocks that contain a nonpure call. */ static void fill_always_executed_in (struct loop *loop, sbitmap contains_call) { basic_block bb = NULL, *bbs, last = NULL; unsigned i; edge e; struct loop *inn_loop = loop; if (!loop->header->aux) { bbs = get_loop_body_in_dom_order (loop); for (i = 0; i < loop->num_nodes; i++) { edge_iterator ei; bb = bbs[i]; if (dominated_by_p (CDI_DOMINATORS, loop->latch, bb)) last = bb; if (TEST_BIT (contains_call, bb->index)) break; FOR_EACH_EDGE (e, ei, bb->succs) if (!flow_bb_inside_loop_p (loop, e->dest)) break; if (e) break; /* A loop might be infinite (TODO use simple loop analysis to disprove this if possible). */ if (bb->flags & BB_IRREDUCIBLE_LOOP) break; if (!flow_bb_inside_loop_p (inn_loop, bb)) break; if (bb->loop_father->header == bb) { if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb)) break; /* In a loop that is always entered we may proceed anyway. But record that we entered it and stop once we leave it. */ inn_loop = bb->loop_father; } } while (1) { last->aux = loop; if (last == loop->header) break; last = get_immediate_dominator (CDI_DOMINATORS, last); } free (bbs); } for (loop = loop->inner; loop; loop = loop->next) fill_always_executed_in (loop, contains_call); } /* Compute the global information needed by the loop invariant motion pass. LOOPS is the loop tree. */ static void tree_ssa_lim_initialize (struct loops *loops) { sbitmap contains_call = sbitmap_alloc (last_basic_block); block_stmt_iterator bsi; struct loop *loop; basic_block bb; sbitmap_zero (contains_call); FOR_EACH_BB (bb) { for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { if (nonpure_call_p (bsi_stmt (bsi))) break; } if (!bsi_end_p (bsi)) SET_BIT (contains_call, bb->index); } for (loop = loops->tree_root->inner; loop; loop = loop->next) fill_always_executed_in (loop, contains_call); sbitmap_free (contains_call); } /* Cleans up after the invariant motion pass. */ static void tree_ssa_lim_finalize (void) { basic_block bb; FOR_EACH_BB (bb) { bb->aux = NULL; } } /* Moves invariants from LOOPS. Only "expensive" invariants are moved out -- i.e. those that are likely to be win regardless of the register pressure. */ void tree_ssa_lim (struct loops *loops) { tree_ssa_lim_initialize (loops); /* For each statement determine the outermost loop in that it is invariant and cost for computing the invariant. */ determine_invariantness (); /* For each memory reference determine whether it is possible to hoist it out of the loop. Force the necessary invariants to be moved out of the loops as well. */ determine_lsm (loops); /* Move the expressions that are expensive enough. */ move_computations (); tree_ssa_lim_finalize (); }