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Diffstat (limited to 'contrib/gcc/tree-ssa-loop-im.c')
| -rw-r--r-- | contrib/gcc/tree-ssa-loop-im.c | 1562 |
1 files changed, 1562 insertions, 0 deletions
diff --git a/contrib/gcc/tree-ssa-loop-im.c b/contrib/gcc/tree-ssa-loop-im.c new file mode 100644 index 0000000..db9f42f --- /dev/null +++ b/contrib/gcc/tree-ssa-loop-im.c @@ -0,0 +1,1562 @@ +/* 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 (); +} |
