tree.c

GCC编译器源代码

   don't use it.  */

int
chain_member_purpose (elem, chain)
     tree elem, chain;
{
  while (chain)
    {
      if (elem == TREE_PURPOSE (chain))
	return 1;
      chain = TREE_CHAIN (chain);
    }

  return 0;
}

/* Return the length of a chain of nodes chained through TREE_CHAIN.
   We expect a null pointer to mark the end of the chain.
   This is the Lisp primitive `length'.  */

int
list_length (t)
     tree t;
{
  register tree tail;
  register int len = 0;

  for (tail = t; tail; tail = TREE_CHAIN (tail))
    len++;

  return len;
}

/* Concatenate two chains of nodes (chained through TREE_CHAIN)
   by modifying the last node in chain 1 to point to chain 2.
   This is the Lisp primitive `nconc'.  */

tree
chainon (op1, op2)
     tree op1, op2;
{

  if (op1)
    {
      register tree t1;
      register tree t2;

      for (t1 = op1; TREE_CHAIN (t1); t1 = TREE_CHAIN (t1))
	;
      TREE_CHAIN (t1) = op2;
      for (t2 = op2; t2; t2 = TREE_CHAIN (t2))
        if (t2 == t1)
          abort ();  /* Circularity created.  */
      return op1;
    }
  else return op2;
}

/* Return the last node in a chain of nodes (chained through TREE_CHAIN).  */

tree
tree_last (chain)
     register tree chain;
{
  register tree next;
  if (chain)
    while (next = TREE_CHAIN (chain))
      chain = next;
  return chain;
}

/* Reverse the order of elements in the chain T,
   and return the new head of the chain (old last element).  */

tree
nreverse (t)
     tree t;
{
  register tree prev = 0, decl, next;
  for (decl = t; decl; decl = next)
    {
      next = TREE_CHAIN (decl);
      TREE_CHAIN (decl) = prev;
      prev = decl;
    }
  return prev;
}

/* Given a chain CHAIN of tree nodes,
   construct and return a list of those nodes.  */

tree
listify (chain)
     tree chain;
{
  tree result = NULL_TREE;
  tree in_tail = chain;
  tree out_tail = NULL_TREE;

  while (in_tail)
    {
      tree next = tree_cons (NULL_TREE, in_tail, NULL_TREE);
      if (out_tail)
	TREE_CHAIN (out_tail) = next;
      else
	result = next;
      out_tail = next;
      in_tail = TREE_CHAIN (in_tail);
    }

  return result;
}

/* Return a newly created TREE_LIST node whose
   purpose and value fields are PARM and VALUE.  */

tree
build_tree_list (parm, value)
     tree parm, value;
{
  register tree t = make_node (TREE_LIST);
  TREE_PURPOSE (t) = parm;
  TREE_VALUE (t) = value;
  return t;
}

/* Similar, but build on the temp_decl_obstack.  */

tree
build_decl_list (parm, value)
     tree parm, value;
{
  register tree node;
  register struct obstack *ambient_obstack = current_obstack;
  current_obstack = &temp_decl_obstack;
  node = build_tree_list (parm, value);
  current_obstack = ambient_obstack;
  return node;
}

/* Similar, but build on the expression_obstack.  */

tree
build_expr_list (parm, value)
     tree parm, value;
{
  register tree node;
  register struct obstack *ambient_obstack = current_obstack;
  current_obstack = expression_obstack;
  node = build_tree_list (parm, value);
  current_obstack = ambient_obstack;
  return node;
}

/* Return a newly created TREE_LIST node whose
   purpose and value fields are PARM and VALUE
   and whose TREE_CHAIN is CHAIN.  */

tree
tree_cons (purpose, value, chain)
     tree purpose, value, chain;
{
#if 0
  register tree node = make_node (TREE_LIST);
#else
  register int i;
  register tree node = (tree) obstack_alloc (current_obstack, sizeof (struct tree_list));
#ifdef GATHER_STATISTICS
  tree_node_counts[(int)x_kind]++;
  tree_node_sizes[(int)x_kind] += sizeof (struct tree_list);
#endif

  for (i = (sizeof (struct tree_common) / sizeof (int)) - 1; i >= 0; i--)
    ((int *) node)[i] = 0;

  TREE_SET_CODE (node, TREE_LIST);
  if (current_obstack == &permanent_obstack)
    TREE_PERMANENT (node) = 1;
#endif

  TREE_CHAIN (node) = chain;
  TREE_PURPOSE (node) = purpose;
  TREE_VALUE (node) = value;
  return node;
}

/* Similar, but build on the temp_decl_obstack.  */

tree
decl_tree_cons (purpose, value, chain)
     tree purpose, value, chain;
{
  register tree node;
  register struct obstack *ambient_obstack = current_obstack;
  current_obstack = &temp_decl_obstack;
  node = tree_cons (purpose, value, chain);
  current_obstack = ambient_obstack;
  return node;
}

/* Similar, but build on the expression_obstack.  */

tree
expr_tree_cons (purpose, value, chain)
     tree purpose, value, chain;
{
  register tree node;
  register struct obstack *ambient_obstack = current_obstack;
  current_obstack = expression_obstack;
  node = tree_cons (purpose, value, chain);
  current_obstack = ambient_obstack;
  return node;
}

/* Same as `tree_cons' but make a permanent object.  */

tree
perm_tree_cons (purpose, value, chain)
     tree purpose, value, chain;
{
  register tree node;
  register struct obstack *ambient_obstack = current_obstack;
  current_obstack = &permanent_obstack;

  node = tree_cons (purpose, value, chain);
  current_obstack = ambient_obstack;
  return node;
}

/* Same as `tree_cons', but make this node temporary, regardless.  */

tree
temp_tree_cons (purpose, value, chain)
     tree purpose, value, chain;
{
  register tree node;
  register struct obstack *ambient_obstack = current_obstack;
  current_obstack = &temporary_obstack;

  node = tree_cons (purpose, value, chain);
  current_obstack = ambient_obstack;
  return node;
}

/* Same as `tree_cons', but save this node if the function's RTL is saved.  */

tree
saveable_tree_cons (purpose, value, chain)
     tree purpose, value, chain;
{
  register tree node;
  register struct obstack *ambient_obstack = current_obstack;
  current_obstack = saveable_obstack;

  node = tree_cons (purpose, value, chain);
  current_obstack = ambient_obstack;
  return node;
}

/* Return the size nominally occupied by an object of type TYPE
   when it resides in memory.  The value is measured in units of bytes,
   and its data type is that normally used for type sizes
   (which is the first type created by make_signed_type or
   make_unsigned_type).  */

tree
size_in_bytes (type)
     tree type;
{
  tree t;

  if (type == error_mark_node)
    return integer_zero_node;
  type = TYPE_MAIN_VARIANT (type);
  if (TYPE_SIZE (type) == 0)
    {
      incomplete_type_error (NULL_TREE, type);
      return integer_zero_node;
    }
  t = size_binop (CEIL_DIV_EXPR, TYPE_SIZE (type),
		  size_int (BITS_PER_UNIT));
  if (TREE_CODE (t) == INTEGER_CST)
    force_fit_type (t, 0);
  return t;
}

/* Return the size of TYPE (in bytes) as an integer,
   or return -1 if the size can vary.  */

int
int_size_in_bytes (type)
     tree type;
{
  unsigned int size;
  if (type == error_mark_node)
    return 0;
  type = TYPE_MAIN_VARIANT (type);
  if (TYPE_SIZE (type) == 0)
    return -1;
  if (TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
    return -1;
  if (TREE_INT_CST_HIGH (TYPE_SIZE (type)) != 0)
    {
      tree t = size_binop (CEIL_DIV_EXPR, TYPE_SIZE (type),
			   size_int (BITS_PER_UNIT));
      return TREE_INT_CST_LOW (t);
    }
  size = TREE_INT_CST_LOW (TYPE_SIZE (type));
  return (size + BITS_PER_UNIT - 1) / BITS_PER_UNIT;
}

/* Return, as a tree node, the number of elements for TYPE (which is an
   ARRAY_TYPE) minus one. This counts only elements of the top array.

   Don't let any SAVE_EXPRs escape; if we are called as part of a cleanup
   action, they would get unsaved.  */

tree
array_type_nelts (type)
     tree type;
{
  tree index_type, min, max;

  /* If they did it with unspecified bounds, then we should have already
     given an error about it before we got here.  */
  if (! TYPE_DOMAIN (type))
    return error_mark_node;

  index_type = TYPE_DOMAIN (type);
  min = TYPE_MIN_VALUE (index_type);
  max = TYPE_MAX_VALUE (index_type);

  if (! TREE_CONSTANT (min))
    {
      STRIP_NOPS (min);
      if (TREE_CODE (min) == SAVE_EXPR)
	min = build (RTL_EXPR, TREE_TYPE (TYPE_MIN_VALUE (index_type)), 0,
		     SAVE_EXPR_RTL (min));
      else
	min = TYPE_MIN_VALUE (index_type);
    }

  if (! TREE_CONSTANT (max))
    {
      STRIP_NOPS (max);
      if (TREE_CODE (max) == SAVE_EXPR)
	max = build (RTL_EXPR, TREE_TYPE (TYPE_MAX_VALUE (index_type)), 0,
		     SAVE_EXPR_RTL (max));
      else
	max = TYPE_MAX_VALUE (index_type);
    }

  return (integer_zerop (min)
	  ? max
	  : fold (build (MINUS_EXPR, TREE_TYPE (max), max, min)));
}

/* Return nonzero if arg is static -- a reference to an object in
   static storage.  This is not the same as the C meaning of `static'.  */

int
staticp (arg)
     tree arg;
{
  switch (TREE_CODE (arg))
    {
    case FUNCTION_DECL:
      /* Nested functions aren't static, since taking their address
	 involves a trampoline.  */
       return decl_function_context (arg) == 0 || DECL_NO_STATIC_CHAIN (arg);
    case VAR_DECL:
      return TREE_STATIC (arg) || DECL_EXTERNAL (arg);

    case CONSTRUCTOR:
      return TREE_STATIC (arg);

    case STRING_CST:
      return 1;

      /* If we are referencing a bitfield, we can't evaluate an
	 ADDR_EXPR at compile time and so it isn't a constant.  */
    case COMPONENT_REF:
      return (! DECL_BIT_FIELD (TREE_OPERAND (arg, 1))
	      && staticp (TREE_OPERAND (arg, 0)));

    case BIT_FIELD_REF:
      return 0;

#if 0
       /* This case is technically correct, but results in setting
	  TREE_CONSTANT on ADDR_EXPRs that cannot be evaluated at
	  compile time.  */
    case INDIRECT_REF:
      return TREE_CONSTANT (TREE_OPERAND (arg, 0));
#endif

    case ARRAY_REF:
      if (TREE_CODE (TYPE_SIZE (TREE_TYPE (arg))) == INTEGER_CST
	  && TREE_CODE (TREE_OPERAND (arg, 1)) == INTEGER_CST)
	return staticp (TREE_OPERAND (arg, 0));

    default:
      return 0;
    }
}

/* Wrap a SAVE_EXPR around EXPR, if appropriate.
   Do this to any expression which may be used in more than one place,
   but must be evaluated only once.

   Normally, expand_expr would reevaluate the expression each time.
   Calling save_expr produces something that is evaluated and recorded
   the first time expand_expr is called on it.  Subsequent calls to
   expand_expr just reuse the recorded value.

   The call to expand_expr that generates code that actually computes
   the value is the first call *at compile time*.  Subsequent calls
   *at compile time* generate code to use the saved value.
   This produces correct result provided that *at run time* control
   always flows through the insns made by the first expand_expr
   before reaching the other places where the save_expr was evaluated.
   You, the caller of save_expr, must make sure this is so.

   Constants, and certain read-only nodes, are returned with no
   SAVE_EXPR because that is safe.  Expressions containing placeholders
   are not touched; see tree.def for an explanation of what these
   are used for.  */

tree
save_expr (expr)
     tree expr;
{
  register tree t = fold (expr);

  /* We don't care about whether this can be used as an lvalue in this
     context.  */
  while (TREE_CODE (t) == NON_LVALUE_EXPR)
    t = TREE_OPERAND (t, 0);

  /* If the tree evaluates to a constant, then we don't want to hide that
     fact (i.e. this allows further folding, and direct checks for constants).
     However, a read-only object that has side effects cannot be bypassed.
     Since it is no problem to reevaluate literals, we just return the 
     literal node.  */

  if (TREE_CONSTANT (t) || (TREE_READONLY (t) && ! TREE_SIDE_EFFECTS (t))
      || TREE_CODE (t) == SAVE_EXPR || TREE_CODE (t) == ERROR_MARK)
    return t;

  /* If T contains a PLACEHOLDER_EXPR, we must evaluate it each time, since
     it means that the size or offset of some field of an object depends on
     the value within another field.

     Note that it must not be the case that T contains both a PLACEHOLDER_EXPR
     and some variable since it would then need to be both evaluated once and
     evaluated more than once.  Front-ends must assure this case cannot
     happen by surrounding any such subexpressions in their own SAVE_EXPR
     and forcing evaluation at the proper time.  */
  if (contains_placeholder_p (t))
    return t;

  t = build (SAVE_EXPR, TREE_TYPE (expr), t, current_function_decl, NULL_TREE);

  /* This expression might be placed ahead of a jump to ensure that the
     value was computed on both sides of the jump.  So make sure it isn't
     eliminated as dead.  */
  TREE_SIDE_EFFECTS (t) = 1;
  return t;
}

/* Arrange for an expression to be expanded multiple independent
   times.  This is useful for cleanup actions, as the backend can
   e