tree.c

gcc库的原代码,对编程有很大帮助.

      /* All BLOCK nodes are put where we can preserve them if nec.  */
      if (obstack != &permanent_obstack)
	obstack = saveable_obstack;
      break;

    case 's':  /* an expression with side effects */
#ifdef GATHER_STATISTICS
      kind = s_kind;
      goto usual_kind;
#endif
    case 'r':  /* a reference */
#ifdef GATHER_STATISTICS
      kind = r_kind;
      goto usual_kind;
#endif
    case 'e':  /* an expression */
    case '<':  /* a comparison expression */
    case '1':  /* a unary arithmetic expression */
    case '2':  /* a binary arithmetic expression */
#ifdef GATHER_STATISTICS
      kind = e_kind;
    usual_kind:
#endif
      obstack = expression_obstack;
      /* All BIND_EXPR nodes are put where we can preserve them if nec.  */
      if (code == BIND_EXPR && obstack != &permanent_obstack)
	obstack = saveable_obstack;
      length = sizeof (struct tree_exp)
	+ (tree_code_length[(int) code] - 1) * sizeof (char *);
      break;

    case 'c':  /* a constant */
#ifdef GATHER_STATISTICS
      kind = c_kind;
#endif
      obstack = expression_obstack;

      /* We can't use tree_code_length for INTEGER_CST, since the number of
	 words is machine-dependent due to varying length of HOST_WIDE_INT,
	 which might be wider than a pointer (e.g., long long).  Similarly
	 for REAL_CST, since the number of words is machine-dependent due
	 to varying size and alignment of `double'.  */

      if (code == INTEGER_CST)
	length = sizeof (struct tree_int_cst);
      else if (code == REAL_CST)
	length = sizeof (struct tree_real_cst);
      else
	length = sizeof (struct tree_common)
	  + tree_code_length[(int) code] * sizeof (char *);
      break;

    case 'x':  /* something random, like an identifier.  */
#ifdef GATHER_STATISTICS
      if (code == IDENTIFIER_NODE)
	kind = id_kind;
      else if (code == OP_IDENTIFIER)
	kind = op_id_kind;
      else if (code == TREE_VEC)
	kind = vec_kind;
      else
	kind = x_kind;
#endif
      length = sizeof (struct tree_common)
	+ tree_code_length[(int) code] * sizeof (char *);
      /* Identifier nodes are always permanent since they are
	 unique in a compiler run.  */
      if (code == IDENTIFIER_NODE) obstack = &permanent_obstack;
      break;

    default:
      abort ();
    }

  t = (tree) obstack_alloc (obstack, length);

#ifdef GATHER_STATISTICS
  tree_node_counts[(int)kind]++;
  tree_node_sizes[(int)kind] += length;
#endif

  /* Clear a word at a time.  */
  for (i = (length / sizeof (int)) - 1; i >= 0; i--)
    ((int *) t)[i] = 0;
  /* Clear any extra bytes.  */
  for (i = length / sizeof (int) * sizeof (int); i < length; i++)
    ((char *) t)[i] = 0;

  TREE_SET_CODE (t, code);
  if (obstack == &permanent_obstack)
    TREE_PERMANENT (t) = 1;

  switch (type)
    {
    case 's':
      TREE_SIDE_EFFECTS (t) = 1;
      TREE_TYPE (t) = void_type_node;
      break;

    case 'd':
      if (code != FUNCTION_DECL)
	DECL_ALIGN (t) = 1;
      DECL_IN_SYSTEM_HEADER (t)
	= in_system_header && (obstack == &permanent_obstack);
      DECL_SOURCE_LINE (t) = lineno;
      DECL_SOURCE_FILE (t) = (input_filename) ? input_filename : "<built-in>";
      DECL_UID (t) = next_decl_uid++;
      break;

    case 't':
      TYPE_UID (t) = next_type_uid++;
      TYPE_ALIGN (t) = 1;
      TYPE_MAIN_VARIANT (t) = t;
      TYPE_OBSTACK (t) = obstack;
      TYPE_ATTRIBUTES (t) = NULL_TREE;
#ifdef SET_DEFAULT_TYPE_ATTRIBUTES
      SET_DEFAULT_TYPE_ATTRIBUTES (t);
#endif
      break;

    case 'c':
      TREE_CONSTANT (t) = 1;
      break;
    }

  return t;
}

/* Return a new node with the same contents as NODE
   except that its TREE_CHAIN is zero and it has a fresh uid.  */

tree
copy_node (node)
     tree node;
{
  register tree t;
  register enum tree_code code = TREE_CODE (node);
  register int length;
  register int i;

  switch (TREE_CODE_CLASS (code))
    {
    case 'd':  /* A decl node */
      length = sizeof (struct tree_decl);
      break;

    case 't':  /* a type node */
      length = sizeof (struct tree_type);
      break;

    case 'b':  /* a lexical block node */
      length = sizeof (struct tree_block);
      break;

    case 'r':  /* a reference */
    case 'e':  /* an expression */
    case 's':  /* an expression with side effects */
    case '<':  /* a comparison expression */
    case '1':  /* a unary arithmetic expression */
    case '2':  /* a binary arithmetic expression */
      length = sizeof (struct tree_exp)
	+ (tree_code_length[(int) code] - 1) * sizeof (char *);
      break;

    case 'c':  /* a constant */
      /* We can't use tree_code_length for INTEGER_CST, since the number of
	 words is machine-dependent due to varying length of HOST_WIDE_INT,
	 which might be wider than a pointer (e.g., long long).  Similarly
	 for REAL_CST, since the number of words is machine-dependent due
	 to varying size and alignment of `double'.  */
      if (code == INTEGER_CST)
        {
          length = sizeof (struct tree_int_cst);
          break;
        }
      else if (code == REAL_CST)
	{
	  length = sizeof (struct tree_real_cst);
	  break;
	}

    case 'x':  /* something random, like an identifier.  */
      length = sizeof (struct tree_common)
	+ tree_code_length[(int) code] * sizeof (char *);
      if (code == TREE_VEC)
	length += (TREE_VEC_LENGTH (node) - 1) * sizeof (char *);
    }

  t = (tree) obstack_alloc (current_obstack, length);

  for (i = (length / sizeof (int)) - 1; i >= 0; i--)
    ((int *) t)[i] = ((int *) node)[i];
  /* Clear any extra bytes.  */
  for (i = length / sizeof (int) * sizeof (int); i < length; i++)
    ((char *) t)[i] = ((char *) node)[i];

  TREE_CHAIN (t) = 0;

  if (TREE_CODE_CLASS (code) == 'd')
    DECL_UID (t) = next_decl_uid++;
  else if (TREE_CODE_CLASS (code) == 't')
    {
      TYPE_UID (t) = next_type_uid++;
      TYPE_OBSTACK (t) = current_obstack;
    }

  TREE_PERMANENT (t) = (current_obstack == &permanent_obstack);

  return t;
}

/* Return a copy of a chain of nodes, chained through the TREE_CHAIN field.
   For example, this can copy a list made of TREE_LIST nodes.  */

tree
copy_list (list)
     tree list;
{
  tree head;
  register tree prev, next;

  if (list == 0)
    return 0;

  head = prev = copy_node (list);
  next = TREE_CHAIN (list);
  while (next)
    {
      TREE_CHAIN (prev) = copy_node (next);
      prev = TREE_CHAIN (prev);
      next = TREE_CHAIN (next);
    }
  return head;
}

#define HASHBITS 30

/* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
   If an identifier with that name has previously been referred to,
   the same node is returned this time.  */

tree
get_identifier (text)
     register char *text;
{
  register int hi;
  register int i;
  register tree idp;
  register int len, hash_len;

  /* Compute length of text in len.  */
  for (len = 0; text[len]; len++);

  /* Decide how much of that length to hash on */
  hash_len = len;
  if (warn_id_clash && len > id_clash_len)
    hash_len = id_clash_len;

  /* Compute hash code */
  hi = hash_len * 613 + (unsigned)text[0];
  for (i = 1; i < hash_len; i += 2)
    hi = ((hi * 613) + (unsigned)(text[i]));

  hi &= (1 << HASHBITS) - 1;
  hi %= MAX_HASH_TABLE;
  
  /* Search table for identifier */
  for (idp = hash_table[hi]; idp; idp = TREE_CHAIN (idp))
    if (IDENTIFIER_LENGTH (idp) == len
	&& IDENTIFIER_POINTER (idp)[0] == text[0]
	&& !bcmp (IDENTIFIER_POINTER (idp), text, len))
      return idp;		/* <-- return if found */

  /* Not found; optionally warn about a similar identifier */
  if (warn_id_clash && do_identifier_warnings && len >= id_clash_len)
    for (idp = hash_table[hi]; idp; idp = TREE_CHAIN (idp))
      if (!strncmp (IDENTIFIER_POINTER (idp), text, id_clash_len))
	{
	  warning ("`%s' and `%s' identical in first %d characters",
		   IDENTIFIER_POINTER (idp), text, id_clash_len);
	  break;
	}

  if (tree_code_length[(int) IDENTIFIER_NODE] < 0)
    abort ();			/* set_identifier_size hasn't been called.  */

  /* Not found, create one, add to chain */
  idp = make_node (IDENTIFIER_NODE);
  IDENTIFIER_LENGTH (idp) = len;
#ifdef GATHER_STATISTICS
  id_string_size += len;
#endif

  IDENTIFIER_POINTER (idp) = obstack_copy0 (&permanent_obstack, text, len);

  TREE_CHAIN (idp) = hash_table[hi];
  hash_table[hi] = idp;
  return idp;			/* <-- return if created */
}

/* Enable warnings on similar identifiers (if requested).
   Done after the built-in identifiers are created.  */

void
start_identifier_warnings ()
{
  do_identifier_warnings = 1;
}

/* Record the size of an identifier node for the language in use.
   SIZE is the total size in bytes.
   This is called by the language-specific files.  This must be
   called before allocating any identifiers.  */

void
set_identifier_size (size)
     int size;
{
  tree_code_length[(int) IDENTIFIER_NODE]
    = (size - sizeof (struct tree_common)) / sizeof (tree);
}

/* Return a newly constructed INTEGER_CST node whose constant value
   is specified by the two ints LOW and HI.
   The TREE_TYPE is set to `int'. 

   This function should be used via the `build_int_2' macro.  */

tree
build_int_2_wide (low, hi)
     HOST_WIDE_INT low, hi;
{
  register tree t = make_node (INTEGER_CST);
  TREE_INT_CST_LOW (t) = low;
  TREE_INT_CST_HIGH (t) = hi;
  TREE_TYPE (t) = integer_type_node;
  return t;
}

/* Return a new REAL_CST node whose type is TYPE and value is D.  */

tree
build_real (type, d)
     tree type;
     REAL_VALUE_TYPE d;
{
  tree v;
  int overflow = 0;

  /* Check for valid float value for this type on this target machine;
     if not, can print error message and store a valid value in D.  */
#ifdef CHECK_FLOAT_VALUE
  CHECK_FLOAT_VALUE (TYPE_MODE (type), d, overflow);
#endif

  v = make_node (REAL_CST);
  TREE_TYPE (v) = type;
  TREE_REAL_CST (v) = d;
  TREE_OVERFLOW (v) = TREE_CONSTANT_OVERFLOW (v) = overflow;
  return v;
}

/* Return a new REAL_CST node whose type is TYPE
   and whose value is the integer value of the INTEGER_CST node I.  */

#if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)

REAL_VALUE_TYPE
real_value_from_int_cst (i)
     tree i;
{
  REAL_VALUE_TYPE d;
  REAL_VALUE_TYPE e;
  /* Some 386 compilers mishandle unsigned int to float conversions,
     so introduce a temporary variable E to avoid those bugs.  */

#ifdef REAL_ARITHMETIC
  if (! TREE_UNSIGNED (TREE_TYPE (i)))
    REAL_VALUE_FROM_INT (d, TREE_INT_CST_LOW (i), TREE_INT_CST_HIGH (i));
  else
    REAL_VALUE_FROM_UNSIGNED_INT (d, TREE_INT_CST_LOW (i), TREE_INT_CST_HIGH (i));
#else /* not REAL_ARITHMETIC */
  if (TREE_INT_CST_HIGH (i) < 0 && ! TREE_UNSIGNED (TREE_TYPE (i)))
    {
      d = (double) (~ TREE_INT_CST_HIGH (i));
      e = ((double) ((HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2))
	    * (double) ((HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)));
      d *= e;
      e = (double) (unsigned HOST_WIDE_INT) (~ TREE_INT_CST_LOW (i));
      d += e;
      d = (- d - 1.0);
    }
  else
    {
      d = (double) (unsigned HOST_WIDE_INT) TREE_INT_CST_HIGH (i);
      e = ((double) ((HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2))
	    * (double) ((HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)));
      d *= e;
      e = (double) (unsigned HOST_WIDE_INT) TREE_INT_CST_LOW (i);
      d += e;
    }
#endif /* not REAL_ARITHMETIC */
  return d;
}

/* This function can't be implemented if we can't do arithmetic
   on the float representation.  */

tree
build_real_from_int_cst (type, i)
     tree type;
     tree i;
{
  tree v;
  int overflow = TREE_OVERFLOW (i);
  REAL_VALUE_TYPE d;
  jmp_buf float_error;

  v = make_node (REAL_CST);
  TREE_TYPE (v) = type;

  if (setjmp (float_error))
    {
      d = dconst0;
      overflow = 1;
      goto got_it;
    }

  set_float_handler (float_error);

  d = REAL_VALUE_TRUNCATE (TYPE_MODE (type), real_value_from_int_cst (i));

  /* Check for valid float value for this type on this target machine.  */

 got_it:
  set_float_handler (NULL_PTR);

#ifdef CHECK_FLOAT_VALUE
  CHECK_FLOAT_VALUE (TYPE_MODE (type), d, overflow);
#endif

  TREE_REAL_CST (v) = d;
  TREE_OVERFLOW (v) = TREE_CONSTANT_OVERFLOW (v) = overflow;
  return v;
}

#endif /* not REAL_IS_NOT_DOUBLE, or REAL_ARITHMETIC */

/* Return a newly constructed STRING_CST node whose value is
   the LEN characters at STR.
   The TREE_TYPE is not initialized.  */

tree
build_string (len, str)
     int len;
     char *str;
{
  /* Put the string in saveable_obstack since it will be placed in the RTL
     for an "asm" statement and will also be kept around a while if
     deferring constant output in varasm.c.  */

  register tree s = make_node (STRING_CST);
  TREE_STRING_LENGTH (s) = len;
  TREE_STRING_POINTER (s) = obstack_copy0 (saveable_obstack, str, len);
  return s;
}

/* Return a newly constructed COMPLEX_CST node whose value is
   specified by the real and imaginary parts REAL and IMAG.
   Both REAL and IMAG should be constant nodes.
   The TREE_TYPE is not initialized.  */

tree
build_complex (real, imag)
     tree real, imag;
{
  register tree t = make_node (COMPLEX_CST);

  TREE_REALPART (t) = real;
  TREE_IMAGPART (t) = imag;