tree-ssa-loop-im.c: New file.

	* tree-ssa-loop-im.c: New file.
	* Makefile.in (tree-ssa-loop-im.o): Add.
	* cfgloop.c (superloop_at_depth): New function.
	* cfgloop.h (superloop_at_depth): Declare.
	* common.opt (ftree-lim): New flag.
	* expr.c (array_ref_up_bound): New function.
	* params.def (PARAM_LIM_EXPENSIVE): New parameter.
	* timevar.def (TV_LIM): New timevar.
	* tree-dfa.c (compute_immediate_uses): Respect TDFA_USE flags when
	computing immediate uses of a phi node.
	* tree-flow.h (struct tree_ann_common_d): Add aux field.
	(loop_commit_inserts, for_each_index, tree_ssa_lim): Declare.
	* tree-optimize.c (init_tree_optimization_passes): Add pass_lim.
	* tree-pass.h (pass_lim): Declare.
	* tree-ssa-loop.c (tree_ssa_loop_im, gate_tree_ssa_loop_im): New
	functions.
	(pass_lim): New pass structure.
	* tree-eh.c (tree_could_trap_p): Handle ARRAY_REFs correctly.
	* tree.c (in_array_bounds_p): New function.
	* tree.h (TREE_THIS_NOTRAP): Define also for ARRAY_REFs.
	(in_array_bounds_p, array_ref_up_bound): Declare.
	* doc/invoke.texi (-ftree-lim, --param lim-expensive): Document.
	* doc/passes.texi (tree-ssa-loop-im.c): Document.

From-SVN: r84441

1 files changed, 1299 insertions, 0 deletions

diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
new file mode 100644
index 0000000..e7afc24
--- /dev/null
+++ b/gcc/tree-ssa-loop-im.c
@@ -0,0 +1,1299 @@
+/* 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 ();
+}