C++ SSA_NAME_VERSION函数代码示例

static void 
process_replaceable (temp_expr_table_p tab, gimple stmt)
{
  tree var, def, basevar;
  int version;
  ssa_op_iter iter;
  bitmap def_vars, use_vars;

#ifdef ENABLE_CHECKING
  gcc_assert (is_replaceable_p (stmt));
#endif

  def = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_DEF);
  version = SSA_NAME_VERSION (def);
  basevar = SSA_NAME_VAR (def);
  def_vars = BITMAP_ALLOC (NULL);

  bitmap_set_bit (def_vars, DECL_UID (basevar));

  /* Add this expression to the dependency list for each use partition.  */
  FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE)
    {
      int var_version = SSA_NAME_VERSION (var);

      use_vars = tab->expr_decl_uids[var_version];
      add_dependence (tab, version, var);
      if (use_vars)
        {
	  bitmap_ior_into (def_vars, use_vars);
	  BITMAP_FREE (tab->expr_decl_uids[var_version]);
	}
      else
	bitmap_set_bit (def_vars, DECL_UID (SSA_NAME_VAR (var)));
    }

void
set_ssa_name_value (tree name, tree value)
{
  if (SSA_NAME_VERSION (name) >= ssa_name_values.length ())
    ssa_name_values.safe_grow_cleared (SSA_NAME_VERSION (name) + 1);
  ssa_name_values[SSA_NAME_VERSION (name)] = value;
}

void
set_ssa_name_value (tree name, tree value)
{
  if (SSA_NAME_VERSION (name) >= VEC_length (tree, ssa_name_values))
    VEC_safe_grow_cleared (tree, heap, ssa_name_values,
			   SSA_NAME_VERSION (name) + 1);
  VEC_replace (tree, ssa_name_values, SSA_NAME_VERSION (name), value);
}

void
set_ssa_name_value (tree name, tree value)
{
  if (SSA_NAME_VERSION (name) >= ssa_name_values.length ())
    ssa_name_values.safe_grow_cleared (SSA_NAME_VERSION (name) + 1);
  if (value && TREE_OVERFLOW_P (value))
    value = drop_tree_overflow (value);
  ssa_name_values[SSA_NAME_VERSION (name)] = value;
}

static tree
get_value (tree name)
{
  tree val;
  if (SSA_NAME_VERSION (name) >= n_copy_of)
    return NULL_TREE;
  val = copy_of[SSA_NAME_VERSION (name)].value;
  if (val && val != name)
    return val;
  return NULL_TREE;
}

tree
make_ssa_name (tree var, tree stmt)
{
    tree t;
    use_operand_p imm;

    gcc_assert (DECL_P (var)
                || TREE_CODE (var) == INDIRECT_REF);

    gcc_assert (!stmt
                || EXPR_P (stmt) || GIMPLE_STMT_P (stmt)
                || TREE_CODE (stmt) == PHI_NODE);

    /* If our free list has an element, then use it.  */
    if (FREE_SSANAMES (cfun))
    {
        t = FREE_SSANAMES (cfun);
        FREE_SSANAMES (cfun) = TREE_CHAIN (FREE_SSANAMES (cfun));
#ifdef GATHER_STATISTICS
        ssa_name_nodes_reused++;
#endif

        /* The node was cleared out when we put it on the free list, so
        there is no need to do so again here.  */
        gcc_assert (ssa_name (SSA_NAME_VERSION (t)) == NULL);
        VEC_replace (tree, SSANAMES (cfun), SSA_NAME_VERSION (t), t);
    }
    else
    {
        t = make_node (SSA_NAME);
        SSA_NAME_VERSION (t) = num_ssa_names;
        VEC_safe_push (tree, gc, SSANAMES (cfun), t);
#ifdef GATHER_STATISTICS
        ssa_name_nodes_created++;
#endif
    }

    TREE_TYPE (t) = TREE_TYPE (var);
    SSA_NAME_VAR (t) = var;
    SSA_NAME_DEF_STMT (t) = stmt;
    SSA_NAME_PTR_INFO (t) = NULL;
    SSA_NAME_IN_FREE_LIST (t) = 0;
    SSA_NAME_IS_DEFAULT_DEF (t) = 0;
    imm = &(SSA_NAME_IMM_USE_NODE (t));
    imm->use = NULL;
    imm->prev = imm;
    imm->next = imm;
    imm->stmt = t;

    return t;
}

static bool
sese_bad_liveouts_use (sese region, bitmap liveouts, basic_block bb,
		       tree use)
{
  unsigned ver;
  basic_block def_bb;

  if (TREE_CODE (use) != SSA_NAME)
    return false;

  ver = SSA_NAME_VERSION (use);

  /* If it's in liveouts, the variable will get a new PHI node, and
     the debug use will be properly adjusted.  */
  if (bitmap_bit_p (liveouts, ver))
    return false;

  def_bb = gimple_bb (SSA_NAME_DEF_STMT (use));

  if (!def_bb
      || !bb_in_sese_p (def_bb, region)
      || bb_in_sese_p (bb, region))
    return false;

  return true;
}

static unsigned
get_stmt_uid (tree stmt)
{
  if (TREE_CODE (stmt) == PHI_NODE)
    return SSA_NAME_VERSION (PHI_RESULT (stmt)) + max_stmt_uid;

  return stmt_ann (stmt)->uid;
}

static void
init_parameter_lattice_values (void)
{
  tree parm, ssa_name;

  for (parm = DECL_ARGUMENTS (cfun->decl); parm ; parm = DECL_CHAIN (parm))
    if (is_complex_reg (parm)
	&& (ssa_name = ssa_default_def (cfun, parm)) != NULL_TREE)
      complex_lattice_values[SSA_NAME_VERSION (ssa_name)] = VARYING;
}

DEBUG_FUNCTION void
verify_ssaname_freelists (struct function *fun)
{
  if (!gimple_in_ssa_p (fun))
    return;

  bitmap names_in_il = BITMAP_ALLOC (NULL);

  /* Walk the entire IL noting every SSA_NAME we see.  */
  basic_block bb;
  FOR_EACH_BB_FN (bb, fun)
    {
      tree t;
      /* First note the result and arguments of PHI nodes.  */
      for (gphi_iterator gsi = gsi_start_phis (bb);
	   !gsi_end_p (gsi);
	   gsi_next (&gsi))
	{
	  gphi *phi = gsi.phi ();
	  t = gimple_phi_result (phi);
	  bitmap_set_bit (names_in_il, SSA_NAME_VERSION (t));

	  for (unsigned int i = 0; i < gimple_phi_num_args (phi); i++)
	    {
	      t = gimple_phi_arg_def (phi, i);
	      if (TREE_CODE (t) == SSA_NAME)
		bitmap_set_bit (names_in_il, SSA_NAME_VERSION (t));
	    }
	}

      /* Then note the operands of each statement.  */
      for (gimple_stmt_iterator gsi = gsi_start_bb (bb);
	   !gsi_end_p (gsi);
	   gsi_next (&gsi))
	{
	  ssa_op_iter iter;
	  gimple *stmt = gsi_stmt (gsi);
	  FOR_EACH_SSA_TREE_OPERAND (t, stmt, iter, SSA_OP_ALL_OPERANDS)
	    bitmap_set_bit (names_in_il, SSA_NAME_VERSION (t));
	}
    }

static void
init_parameter_lattice_values (void)
{
  tree parm, ssa_name;

  for (parm = DECL_ARGUMENTS (cfun->decl); parm ; parm = TREE_CHAIN (parm))
    if (is_complex_reg (parm)
	&& var_ann (parm) != NULL
	&& (ssa_name = gimple_default_def (cfun, parm)) != NULL_TREE)
      VEC_replace (complex_lattice_t, complex_lattice_values,
		   SSA_NAME_VERSION (ssa_name), VARYING);
}

static bool
verify_def (basic_block bb, basic_block *definition_block, tree ssa_name,
	    tree stmt, bool is_virtual)
{
  if (verify_ssa_name (ssa_name, is_virtual))
    goto err;

  if (definition_block[SSA_NAME_VERSION (ssa_name)])
    {
      error ("SSA_NAME created in two different blocks %i and %i",
	     definition_block[SSA_NAME_VERSION (ssa_name)]->index, bb->index);
      goto err;
    }

  definition_block[SSA_NAME_VERSION (ssa_name)] = bb;

  if (SSA_NAME_DEF_STMT (ssa_name) != stmt)
    {
      error ("SSA_NAME_DEF_STMT is wrong");
      fprintf (stderr, "Expected definition statement:\n");
      print_generic_stmt (stderr, SSA_NAME_DEF_STMT (ssa_name), TDF_VOPS);
      fprintf (stderr, "\nActual definition statement:\n");
      print_generic_stmt (stderr, stmt, TDF_VOPS);
      goto err;
    }

  return false;

err:
  fprintf (stderr, "while verifying SSA_NAME ");
  print_generic_expr (stderr, ssa_name, 0);
  fprintf (stderr, " in statement\n");
  print_generic_stmt (stderr, stmt, TDF_VOPS);

  return true;
}

static void
add_dependence (temp_expr_table_p tab, int version, tree var)
{
  int i;
  bitmap_iterator bi;
  unsigned x;

  i = SSA_NAME_VERSION (var);
  if (version_to_be_replaced_p (tab, i))
    {
      if (!bitmap_empty_p (tab->new_replaceable_dependencies))
        {
	  /* Version will now be killed by a write to any partition the 
	     substituted expression would have been killed by.  */
	  EXECUTE_IF_SET_IN_BITMAP (tab->new_replaceable_dependencies, 0, x, bi)
	    add_to_partition_kill_list (tab, x, version);

	  /* Rather than set partition_dependencies and in_use lists bit by 
	     bit, simply OR in the new_replaceable_dependencies bits.  */
	  if (!tab->partition_dependencies[version])
	    tab->partition_dependencies[version] = BITMAP_ALLOC (NULL);
	  bitmap_ior_into (tab->partition_dependencies[version], 
			   tab->new_replaceable_dependencies);
	  bitmap_ior_into (tab->partition_in_use, 
			   tab->new_replaceable_dependencies);
	  /* It is only necessary to add these once.  */
	  bitmap_clear (tab->new_replaceable_dependencies);
	}
    }
  else
    {
      i = var_to_partition (tab->map, var);
#ifdef ENABLE_CHECKING
      gcc_assert (i != NO_PARTITION);
      gcc_assert (tab->num_in_part[i] != 0);
#endif
      /* Only dependencies on ssa_names which are coalesced with something need
         to be tracked.  Partitions with containing only a single SSA_NAME
	 *cannot* have their value changed.  */
      if (tab->num_in_part[i] > 1)
        {
	  add_to_partition_kill_list (tab, i, version);
	  make_dependent_on_partition (tab, version, i);
	}
    }
}

static void
sese_build_liveouts_use (sese region, bitmap liveouts, basic_block bb,
			 tree use)
{
  unsigned ver;
  basic_block def_bb;

  if (TREE_CODE (use) != SSA_NAME)
    return;

  ver = SSA_NAME_VERSION (use);
  def_bb = gimple_bb (SSA_NAME_DEF_STMT (use));

  if (!def_bb
      || !bb_in_sese_p (def_bb, region)
      || bb_in_sese_p (bb, region))
    return;

  bitmap_set_bit (liveouts, ver);
}

/* Return SSA names that are unused to GGC memory and compact the SSA
   version namespace.  This is used to keep footprint of compiler during
   interprocedural optimization.  */
static unsigned int
release_dead_ssa_names (void)
{
  tree t;
  unsigned i, j;
  int n = VEC_length (tree, FREE_SSANAMES (cfun));
  referenced_var_iterator rvi;

  /* Current defs point to various dead SSA names that in turn point to
     eventually dead variables so a bunch of memory is held live.  */
  FOR_EACH_REFERENCED_VAR (cfun, t, rvi)
    set_current_def (t, NULL);

  /* Now release the freelist.  */
  VEC_free (tree, gc, FREE_SSANAMES (cfun));
  FREE_SSANAMES (cfun) = NULL;

  /* And compact the SSA number space.  We make sure to not change the
     relative order of SSA versions.  */
  for (i = 1, j = 1; i < VEC_length (tree, cfun->gimple_df->ssa_names); ++i)
    {
      tree name = ssa_name (i);
      if (name)
	{
	  if (i != j)
	    {
	      SSA_NAME_VERSION (name) = j;
	      VEC_replace (tree, cfun->gimple_df->ssa_names, j, name);
	    }
	  j++;
	}
    }
  VEC_truncate (tree, cfun->gimple_df->ssa_names, j);

  statistics_counter_event (cfun, "SSA names released", n);
  statistics_counter_event (cfun, "SSA name holes removed", i - j);
  if (dump_file)
    fprintf (dump_file, "Released %i names, %.2f%%, removed %i holes\n",
	     n, n * 100.0 / num_ssa_names, i - j);
  return 0;
}