--- /dev/null
+/* Loop invariant motion.
+ Copyright (C) 2003 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, 59 Temple Place - Suite 330, Boston, MA
+02111-1307, 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"
+
+/* 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 possibilities of statement movement. */
+
+enum move_pos
+{
+ MOVE_IMPOSSIBLE, /* No movement -- side effect expression. */
+ MOVE_PRESERVE_EXECUTION, /* Must not cause the non-executed statement
+ become executed -- memory accesses, ... */
+ MOVE_POSSIBLE /* Unlimited movement. */
+};
+
+/* 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) ((struct lim_aux_data *) (stmt_ann (STMT)->common.aux))
+
+/* Description of a memory reference for store motion. */
+
+struct mem_ref
+{
+ tree *ref; /* The reference itself. */
+ tree stmt; /* The statement in that it occurs. */
+ struct mem_ref *next; /* Next use in the chain. */
+};
+
+/* 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)
+
+/* Maximum uid in the statement in the function. */
+
+static unsigned max_uid;
+
+/* 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;
+
+ for (; ; addr_p = nxt)
+ {
+ switch (TREE_CODE (*addr_p))
+ {
+ case SSA_NAME:
+ return cbck (*addr_p, addr_p, data);
+
+ case INDIRECT_REF:
+ nxt = &TREE_OPERAND (*addr_p, 0);
+ return cbck (*addr_p, nxt, data);
+
+ case BIT_FIELD_REF:
+ case COMPONENT_REF:
+ case VIEW_CONVERT_EXPR:
+ case ARRAY_RANGE_REF:
+ nxt = &TREE_OPERAND (*addr_p, 0);
+ break;
+
+ case ARRAY_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:
+ return true;
+
+ default:
+ abort ();
+ }
+ }
+}
+
+/* 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. */
+
+static 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. */
+ get_stmt_operands (stmt);
+
+ return MOVE_POSSIBLE;
+ }
+
+ if (TREE_CODE (stmt) != MODIFY_EXPR)
+ return MOVE_IMPOSSIBLE;
+
+ if (stmt_ends_bb_p (stmt))
+ return MOVE_IMPOSSIBLE;
+
+ get_stmt_operands (stmt);
+
+ 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;
+
+ return MOVE_POSSIBLE;
+}
+
+/* Suppose that operand DEF is used inside the LOOP. Returns the outermost
+ loop to that we could move the expresion 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)
+{
+ char 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 != '1'
+ && class != '2'
+ && class != 'e'
+ && class != '<')
+ return NULL;
+
+ nops = first_rtl_op (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 = xmalloc (sizeof (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 lhs, rhs;
+ unsigned cost = 1;
+
+ /* Always try to create possibilities for unswitching. */
+ if (TREE_CODE (stmt) == COND_EXPR)
+ return LIM_EXPENSIVE;
+
+ lhs = TREE_OPERAND (stmt, 0);
+ rhs = TREE_OPERAND (stmt, 1);
+
+ /* Hoisting memory references out should almost surely be a win. */
+ if (!is_gimple_variable (lhs))
+ cost += 20;
+ if (is_gimple_addr_expr_arg (rhs) && !is_gimple_variable (rhs))
+ 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 (rhs)
+ && 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:
+ /* 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);
+ use_optype uses;
+ vuse_optype vuses;
+ v_may_def_optype v_may_defs;
+ stmt_ann_t ann = stmt_ann (stmt);
+ unsigned i;
+
+ if (must_preserve_exec)
+ level = ALWAYS_EXECUTED_IN (bb);
+ else
+ level = superloop_at_depth (loop, 1);
+ lim_data->max_loop = level;
+
+ uses = USE_OPS (ann);
+ for (i = 0; i < NUM_USES (uses); i++)
+ if (!add_dependency (USE_OP (uses, i), lim_data, loop, true))
+ return false;
+
+ vuses = VUSE_OPS (ann);
+ for (i = 0; i < NUM_VUSES (vuses); i++)
+ if (!add_dependency (VUSE_OP (vuses, i), lim_data, loop, false))
+ return false;
+
+ v_may_defs = V_MAY_DEF_OPS (ann);
+ for (i = 0; i < NUM_V_MAY_DEFS (v_may_defs); i++)
+ if (!add_dependency (V_MAY_DEF_OP (v_may_defs, i), 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;
+
+ if (!LIM_DATA (stmt))
+ abort ();
+
+ if (level != LIM_DATA (stmt)->max_loop
+ && !flow_loop_nested_p (LIM_DATA (stmt)->max_loop, level))
+ abort ();
+
+ 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;
+ 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;
+ }
+
+ 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 (NULL);
+ for (i = old_last_basic_block; i < (unsigned) last_basic_block; i++)
+ {
+ bb = BASIC_BLOCK (i);
+ add_bb_to_loop (bb,
+ find_common_loop (bb->succ->dest->loop_father,
+ bb->pred->src->loop_father));
+ }
+}
+
+/* Hoist the statements in basic block BB out of the loops prescribed by
+ data stored in LIM_DATA structres 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);
+ }
+}
+
+/* Hoist the statements out of the loops prescribed by data stored in
+ LIM_DATA structres 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 ();
+ rewrite_into_ssa (false);
+ bitmap_clear (vars_to_rename);
+}
+
+/* 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 definining (invariant) SSA names in expression EXPR to be
+ moved out of the LOOP. */
+
+static void
+force_move_till_expr (tree expr, struct loop *loop)
+{
+ char 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, bb_for_stmt (stmt)->loop_father, loop);
+ return;
+ }
+
+ if (class != '1'
+ && class != '2'
+ && class != 'e'
+ && class != '<')
+ return;
+
+ nops = first_rtl_op (TREE_CODE (expr));
+ for (i = 0; i < nops; i++)
+ force_move_till_expr (TREE_OPERAND (expr, i), loop);
+}
+
+/* Forces statement defining invariants in REF (and *INDEX) to be moved out of
+ the loop passed in DATA. Callback for for_each_index. */
+
+static bool
+force_move_till (tree ref, tree *index, void *data)
+{
+ tree stmt;
+
+ 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, data);
+ force_move_till_expr (lbound, data);
+ }
+
+ if (TREE_CODE (*index) != SSA_NAME)
+ return true;
+
+ stmt = SSA_NAME_DEF_STMT (*index);
+ if (IS_EMPTY_STMT (stmt))
+ return true;
+
+ set_level (stmt, bb_for_stmt (stmt)->loop_father, data);
+
+ return true;
+}
+
+/* Records memory reference *REF (that occurs in statement STMT)
+ to the list MEM_REFS. */
+
+static void
+record_mem_ref (struct mem_ref **mem_refs, tree stmt, tree *ref)
+{
+ struct mem_ref *aref = xmalloc (sizeof (struct mem_ref));
+
+ aref->stmt = stmt;
+ aref->ref = ref;
+
+ aref->next = *mem_refs;
+ *mem_refs = aref;
+}
+
+/* Releases list of memory references MEM_REFS. */
+
+static void
+free_mem_refs (struct mem_ref *mem_refs)
+{
+ struct mem_ref *act;
+
+ while (mem_refs)
+ {
+ act = mem_refs;
+ mem_refs = mem_refs->next;
+ free (act);
+ }
+}
+
+/* If VAR is defined in LOOP and the statement it is defined in does not belong
+ to the set SEEN, add the statement to QUEUE of length IN_QUEUE and
+ to the set SEEN. */
+
+static void
+maybe_queue_var (tree var, struct loop *loop,
+ sbitmap seen, tree *queue, unsigned *in_queue)
+{
+ tree stmt = SSA_NAME_DEF_STMT (var);
+ basic_block def_bb = bb_for_stmt (stmt);
+
+ if (!def_bb
+ || !flow_bb_inside_loop_p (loop, def_bb)
+ || TEST_BIT (seen, stmt_ann (stmt)->uid))
+ return;
+
+ SET_BIT (seen, stmt_ann (stmt)->uid);
+ queue[(*in_queue)++] = stmt;
+}
+
+/* Determine whether all memory references inside the LOOP that correspond
+ to virtual ssa names defined in statement STMT are equal.
+ If so, store the list of the references to MEM_REFS, and return one
+ of them. Otherwise store NULL to MEM_REFS and return NULL_TREE. */
+
+static tree
+single_reachable_address (struct loop *loop, tree stmt,
+ struct mem_ref **mem_refs)
+{
+ tree *queue = xmalloc (sizeof (tree) * max_uid);
+ sbitmap seen = sbitmap_alloc (max_uid);
+ tree common_ref = NULL, *aref;
+ unsigned in_queue = 1;
+ dataflow_t df;
+ unsigned i, n;
+ v_may_def_optype v_may_defs;
+ vuse_optype vuses;
+
+ sbitmap_zero (seen);
+
+ *mem_refs = NULL;
+
+ queue[0] = stmt;
+ SET_BIT (seen, stmt_ann (stmt)->uid);
+
+ while (in_queue)
+ {
+ stmt = queue[--in_queue];
+
+ if (LIM_DATA (stmt)
+ && LIM_DATA (stmt)->sm_done)
+ goto fail;
+
+ switch (TREE_CODE (stmt))
+ {
+ case MODIFY_EXPR:
+ aref = &TREE_OPERAND (stmt, 0);
+ if (is_gimple_reg (*aref)
+ || !is_gimple_lvalue (*aref))
+ aref = &TREE_OPERAND (stmt, 1);
+ if (is_gimple_reg (*aref)
+ || !is_gimple_lvalue (*aref)
+ || (common_ref && !operand_equal_p (*aref, common_ref, 0)))
+ goto fail;
+ common_ref = *aref;
+
+ record_mem_ref (mem_refs, stmt, aref);
+
+ /* Traverse also definitions of the VUSES (there may be other
+ distinct from the one we used to get to this statement). */
+ v_may_defs = STMT_V_MAY_DEF_OPS (stmt);
+ for (i = 0; i < NUM_V_MAY_DEFS (v_may_defs); i++)
+ maybe_queue_var (V_MAY_DEF_OP (v_may_defs, i), loop,
+ seen, queue, &in_queue);
+
+ vuses = STMT_VUSE_OPS (stmt);
+ for (i = 0; i < NUM_VUSES (vuses); i++)
+ maybe_queue_var (VUSE_OP (vuses, i), loop,
+ seen, queue, &in_queue);
+ break;
+
+ case PHI_NODE:
+ for (i = 0; i < (unsigned) PHI_NUM_ARGS (stmt); i++)
+ maybe_queue_var (PHI_ARG_DEF (stmt, i), loop,
+ seen, queue, &in_queue);
+ break;
+
+ default:
+ goto fail;
+ }
+
+ /* Find uses of virtual names. */
+ df = get_immediate_uses (stmt);
+ n = num_immediate_uses (df);
+
+ for (i = 0; i < n; i++)
+ {
+ stmt = immediate_use (df, i);
+
+ if (!flow_bb_inside_loop_p (loop, bb_for_stmt (stmt)))
+ continue;
+
+ if (TEST_BIT (seen, stmt_ann (stmt)->uid))
+ continue;
+ SET_BIT (seen, stmt_ann (stmt)->uid);
+
+ queue[in_queue++] = stmt;
+ }
+ }
+
+ free (queue);
+ sbitmap_free (seen);
+
+ return common_ref;
+
+fail:
+ free_mem_refs (*mem_refs);
+ *mem_refs = NULL;
+ free (queue);
+ sbitmap_free (seen);
+
+ return NULL;
+}
+
+/* Rewrites memory references in list MEM_REFS by variable TMP_VAR. */
+
+static void
+rewrite_mem_refs (tree tmp_var, struct mem_ref *mem_refs)
+{
+ v_may_def_optype v_may_defs;
+ v_must_def_optype v_must_defs;
+ vuse_optype vuses;
+ unsigned i;
+ tree var;
+
+ for (; mem_refs; mem_refs = mem_refs->next)
+ {
+ v_may_defs = STMT_V_MAY_DEF_OPS (mem_refs->stmt);
+ for (i = 0; i < NUM_V_MAY_DEFS (v_may_defs); i++)
+ {
+ var = SSA_NAME_VAR (V_MAY_DEF_RESULT (v_may_defs, i));
+ bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
+ }
+
+ v_must_defs = STMT_V_MUST_DEF_OPS (mem_refs->stmt);
+ for (i = 0; i < NUM_V_MUST_DEFS (v_must_defs); i++)
+ {
+ var = SSA_NAME_VAR (V_MUST_DEF_OP (v_must_defs, i));
+ bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
+ }
+
+ vuses = STMT_VUSE_OPS (mem_refs->stmt);
+ for (i = 0; i < NUM_VUSES (vuses); i++)
+ {
+ var = SSA_NAME_VAR (VUSE_OP (vuses, i));
+ bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
+ }
+
+ *mem_refs->ref = tmp_var;
+ modify_stmt (mem_refs->stmt);
+ }
+}
+
+/* Records request for store motion of memory reference REF from LOOP.
+ MEM_REFS is the list of occurences 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 *mem_refs)
+{
+ struct mem_ref *aref;
+ tree tmp_var;
+ unsigned i;
+ tree load, store;
+
+ tmp_var = make_rename_temp (TREE_TYPE (ref), "lsm_tmp");
+
+ for_each_index (&ref, force_move_till, loop);
+
+ 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 = build (MODIFY_EXPR, void_type_node, tmp_var, ref);
+ modify_stmt (load);
+ 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 = build (MODIFY_EXPR, void_type_node,
+ unshare_expr (ref), tmp_var);
+ bsi_insert_on_edge (exits[i], store);
+ }
+}
+
+/* Determine whether all memory references inside LOOP corresponding to the
+ virtual ssa name REG are equal to each other, and whether the address of
+ this common reference can be hoisted outside 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. */
+
+static void
+determine_lsm_reg (struct loop *loop, edge *exits, unsigned n_exits, tree reg)
+{
+ tree ref;
+ struct mem_ref *mem_refs, *aref;
+ struct loop *must_exec;
+
+ if (is_gimple_reg (reg))
+ return;
+
+ ref = single_reachable_address (loop, SSA_NAME_DEF_STMT (reg), &mem_refs);
+ if (!ref)
+ return;
+
+ if (!for_each_index (&ref, may_move_till, loop))
+ {
+ free_mem_refs (mem_refs);
+ return;
+ }
+
+ if (tree_could_trap_p (ref))
+ {
+ /* 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 = mem_refs; 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)
+ {
+ free_mem_refs (mem_refs);
+ return;
+ }
+ }
+
+ schedule_sm (loop, exits, n_exits, ref, mem_refs);
+ free_mem_refs (mem_refs);
+}
+
+/* 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;
+}
+
+/* Try to perform store motion for all memory references modified inside
+ LOOP. */
+
+static void
+determine_lsm_loop (struct loop *loop)
+{
+ tree phi;
+ unsigned n_exits;
+ edge *exits = get_loop_exit_edges (loop, &n_exits);
+
+ if (!loop_suitable_for_sm (loop, exits, n_exits))
+ {
+ free (exits);
+ return;
+ }
+
+ for (phi = phi_nodes (loop->header); phi; phi = TREE_CHAIN (phi))
+ determine_lsm_reg (loop, exits, n_exits, PHI_RESULT (phi));
+
+ free (exits);
+}
+
+/* Try to perform store motion for all memory references modified inside
+ any of LOOPS. */
+
+static void
+determine_lsm (struct loops *loops)
+{
+ struct loop *loop;
+ basic_block bb;
+
+ /* Create a UID for each statement in the function. Ordering of the
+ UIDs is not important for this pass. */
+ max_uid = 0;
+ FOR_EACH_BB (bb)
+ {
+ block_stmt_iterator bsi;
+ tree phi;
+
+ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+ stmt_ann (bsi_stmt (bsi))->uid = max_uid++;
+
+ for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi))
+ stmt_ann (phi)->uid = max_uid++;
+ }
+
+ compute_immediate_uses (TDFA_USE_VOPS, NULL);
+
+ /* Pass the loops from the outermost. For each virtual operand loop phi node
+ check whether all the references inside the loop correspond to a single
+ address, and if so, move them. */
+
+ 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)
+ {
+ free_df ();
+ 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++)
+ {
+ bb = bbs[i];
+
+ if (dominated_by_p (CDI_DOMINATORS, loop->latch, bb))
+ last = bb;
+
+ if (TEST_BIT (contains_call, bb->index))
+ break;
+
+ for (e = bb->succ; e; e = e->succ_next)
+ 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 ();
+}
projects / gcc.git / commitdiff