varasm.c

gcc库的原代码,对编程有很大帮助.

  switch (TREE_CODE (type))
    {
    case POINTER_TYPE:
    case REFERENCE_TYPE:
      /* I'm not sure whether OFFSET_TYPE needs this treatment,
	 so I'll play safe and return 1.  */
    case OFFSET_TYPE:
      return 1;

    case RECORD_TYPE:
    case UNION_TYPE:
    case QUAL_UNION_TYPE:
      {
	tree fields;
	/* For a type that has fields, see if the fields have pointers.  */
	for (fields = TYPE_FIELDS (type); fields; fields = TREE_CHAIN (fields))
	  if (TREE_CODE (fields) == FIELD_DECL
	      && contains_pointers_p (TREE_TYPE (fields)))
	    return 1;
	return 0;
      }

    case ARRAY_TYPE:
      /* An array type contains pointers if its element type does.  */
      return contains_pointers_p (TREE_TYPE (type));

    default:
      return 0;
    }
}

/* Output text storage for constructor CONSTR. */

void
bc_output_constructor (constr, size)
     tree constr;
     int size;
{
  int i;

  /* Must always be a literal; non-literal constructors are handled
     differently. */

  if (!TREE_CONSTANT (constr))
    abort ();

  /* Always const */
  text_section ();

  /* Align */
  for (i = 0; TYPE_ALIGN (constr) >= BITS_PER_UNIT << (i + 1); i++)
    ;

  if (i > 0)
    BC_OUTPUT_ALIGN (asm_out_file, i);

  /* Output data */
  output_constant (constr, size);
}

/* Create storage for constructor CONSTR. */

void
bc_output_data_constructor (constr)
    tree constr;
{
  int i;

  /* Put in data section */
  data_section ();

  /* Align */
  for (i = 0; TYPE_ALIGN (constr) >= BITS_PER_UNIT << (i + 1); i++);
  if (i > 0)
    BC_OUTPUT_ALIGN (asm_out_file, i);

  /* The constructor is filled in at runtime. */
  BC_OUTPUT_SKIP (asm_out_file, int_size_in_bytes (TREE_TYPE (constr)));
}

/* Output something to declare an external symbol to the assembler.
   (Most assemblers don't need this, so we normally output nothing.)
   Do nothing if DECL is not external.  */

void
assemble_external (decl)
     tree decl;
{
  if (output_bytecode)
    return;

#ifdef ASM_OUTPUT_EXTERNAL
  if (TREE_CODE_CLASS (TREE_CODE (decl)) == 'd'
      && DECL_EXTERNAL (decl) && TREE_PUBLIC (decl))
    {
      rtx rtl = DECL_RTL (decl);

      if (GET_CODE (rtl) == MEM && GET_CODE (XEXP (rtl, 0)) == SYMBOL_REF
	  && ! SYMBOL_REF_USED (XEXP (rtl, 0)))
	{
	  /* Some systems do require some output.  */
	  SYMBOL_REF_USED (XEXP (rtl, 0)) = 1;
	  ASM_OUTPUT_EXTERNAL (asm_out_file, decl, XSTR (XEXP (rtl, 0), 0));
	}
    }
#endif
}

/* Similar, for calling a library function FUN.  */

void
assemble_external_libcall (fun)
     rtx fun;
{
#ifdef ASM_OUTPUT_EXTERNAL_LIBCALL
  if (!output_bytecode)
    {
      /* Declare library function name external when first used, if nec.  */
      if (! SYMBOL_REF_USED (fun))
	{
	  SYMBOL_REF_USED (fun) = 1;
	  ASM_OUTPUT_EXTERNAL_LIBCALL (asm_out_file, fun);
	}
    }
#endif
}

/* Declare the label NAME global.  */

void
assemble_global (name)
     char *name;
{
  ASM_GLOBALIZE_LABEL (asm_out_file, name);
}

/* Assemble a label named NAME.  */

void
assemble_label (name)
     char *name;
{
  if (output_bytecode)
    BC_OUTPUT_LABEL (asm_out_file, name);
  else
    ASM_OUTPUT_LABEL (asm_out_file, name);
}

/* Output to FILE a reference to the assembler name of a C-level name NAME.
   If NAME starts with a *, the rest of NAME is output verbatim.
   Otherwise NAME is transformed in an implementation-defined way
   (usually by the addition of an underscore).
   Many macros in the tm file are defined to call this function.  */

void
assemble_name (file, name)
     FILE *file;
     char *name;
{
  char *real_name;
  int save_warn_id_clash = warn_id_clash;

  STRIP_NAME_ENCODING (real_name, name);

  /* Don't warn about an identifier name length clash on this name, since
     it can be a user symbol suffixed by a number.  */
  warn_id_clash = 0;
  TREE_SYMBOL_REFERENCED (get_identifier (real_name)) = 1;
  warn_id_clash = save_warn_id_clash;

  if (name[0] == '*')
    {
      if (output_bytecode)
	bc_emit_labelref (name, 0);
      else
	fputs (&name[1], file);
    }
  else
    {
      if (output_bytecode)
	BC_OUTPUT_LABELREF (file, name);
      else
	ASM_OUTPUT_LABELREF (file, name);
    }
}

/* Allocate SIZE bytes writable static space with a gensym name
   and return an RTX to refer to its address.  */

rtx
assemble_static_space (size)
     int size;
{
  char name[12];
  char *namestring;
  rtx x;
  /* Round size up to multiple of BIGGEST_ALIGNMENT bits
     so that each uninitialized object starts on such a boundary.  */
  int rounded = ((size + (BIGGEST_ALIGNMENT / BITS_PER_UNIT) - 1)
		 / (BIGGEST_ALIGNMENT / BITS_PER_UNIT)
		 * (BIGGEST_ALIGNMENT / BITS_PER_UNIT));

#if 0
  if (flag_shared_data)
    data_section ();
#endif

  ASM_GENERATE_INTERNAL_LABEL (name, "LF", const_labelno);
  ++const_labelno;

  namestring = (char *) obstack_alloc (saveable_obstack,
				       strlen (name) + 2);
  strcpy (namestring, name);

  if (output_bytecode)
    x = bc_gen_rtx (namestring, 0, (struct bc_label *) 0);
  else
    x = gen_rtx (SYMBOL_REF, Pmode, namestring);

  if (output_bytecode)
    {
      BC_OUTPUT_LOCAL (asm_out_file, name, size, rounded);
    }
  else
    {
#ifdef ASM_OUTPUT_ALIGNED_LOCAL
      ASM_OUTPUT_ALIGNED_LOCAL (asm_out_file, name, size, BIGGEST_ALIGNMENT);
#else
      ASM_OUTPUT_LOCAL (asm_out_file, name, size, rounded);
#endif
    }
  return x;
}

/* Assemble the static constant template for function entry trampolines.
   This is done at most once per compilation.
   Returns an RTX for the address of the template.  */

rtx
assemble_trampoline_template ()
{
  char label[256];
  char *name;
  int align;

  /* Shouldn't get here */
  if (output_bytecode)
    abort ();

  /* By default, put trampoline templates in read-only data section.  */

#ifdef TRAMPOLINE_SECTION
  TRAMPOLINE_SECTION ();
#else
  readonly_data_section ();
#endif

  /* Write the assembler code to define one.  */
  align = floor_log2 (FUNCTION_BOUNDARY / BITS_PER_UNIT);
  if (align > 0)
    ASM_OUTPUT_ALIGN (asm_out_file, align);

  ASM_OUTPUT_INTERNAL_LABEL (asm_out_file, "LTRAMP", 0);
  TRAMPOLINE_TEMPLATE (asm_out_file);

  /* Record the rtl to refer to it.  */
  ASM_GENERATE_INTERNAL_LABEL (label, "LTRAMP", 0);
  name
    = (char *) obstack_copy0 (&permanent_obstack, label, strlen (label));
  return gen_rtx (SYMBOL_REF, Pmode, name);
}

/* Assemble the integer constant X into an object of SIZE bytes.
   X must be either a CONST_INT or CONST_DOUBLE.

   Return 1 if we were able to output the constant, otherwise 0.  If FORCE is
   non-zero, abort if we can't output the constant.  */

int
assemble_integer (x, size, force)
     rtx x;
     int size;
     int force;
{
  /* First try to use the standard 1, 2, 4, 8, and 16 byte
     ASM_OUTPUT... macros. */

  switch (size)
    {
#ifdef ASM_OUTPUT_CHAR
    case 1:
      ASM_OUTPUT_CHAR (asm_out_file, x);
      return 1;
#endif

#ifdef ASM_OUTPUT_SHORT
    case 2:
      ASM_OUTPUT_SHORT (asm_out_file, x);
      return 1;
#endif

#ifdef ASM_OUTPUT_INT
    case 4:
      ASM_OUTPUT_INT (asm_out_file, x);
      return 1;
#endif

#ifdef ASM_OUTPUT_DOUBLE_INT
    case 8:
      ASM_OUTPUT_DOUBLE_INT (asm_out_file, x);
      return 1;
#endif

#ifdef ASM_OUTPUT_QUADRUPLE_INT
    case 16:
      ASM_OUTPUT_QUADRUPLE_INT (asm_out_file, x);
      return 1;
#endif
    }

  /* If we couldn't do it that way, there are two other possibilities: First,
     if the machine can output an explicit byte and this is a 1 byte constant,
     we can use ASM_OUTPUT_BYTE.  */

#ifdef ASM_OUTPUT_BYTE
  if (size == 1 && GET_CODE (x) == CONST_INT)
    {
      ASM_OUTPUT_BYTE (asm_out_file, INTVAL (x));
      return 1;
    }
#endif

  /* Finally, if SIZE is larger than a single word, try to output the constant
     one word at a time.  */

  if (size > UNITS_PER_WORD)
    {
      int i;
      enum machine_mode mode
	= mode_for_size (size * BITS_PER_UNIT, MODE_INT, 0);
      rtx word;

      for (i = 0; i < size / UNITS_PER_WORD; i++)
	{
	  word = operand_subword (x, i, 0, mode);

	  if (word == 0)
	    break;

	  if (! assemble_integer (word, UNITS_PER_WORD, 0))
	    break;
	}

      if (i == size / UNITS_PER_WORD)
	return 1;
      /* If we output at least one word and then could not finish,
	 there is no valid way to continue.  */
      if (i > 0)
	abort ();
    }

  if (force)
    abort ();

  return 0;
}

/* Assemble the floating-point constant D into an object of size MODE.  */

void
assemble_real (d, mode)
     REAL_VALUE_TYPE d;
     enum machine_mode mode;
{
  jmp_buf output_constant_handler;

  if (setjmp (output_constant_handler))
    {
      error ("floating point trap outputting a constant");
#ifdef REAL_IS_NOT_DOUBLE
      bzero ((char *) &d, sizeof d);
      d = dconst0;
#else
      d = 0;
#endif
    }

  set_float_handler (output_constant_handler);

  switch (mode)
    {
#ifdef ASM_OUTPUT_BYTE_FLOAT
    case QFmode:
      ASM_OUTPUT_BYTE_FLOAT (asm_out_file, d);
      break;
#endif
#ifdef ASM_OUTPUT_SHORT_FLOAT
    case HFmode:
      ASM_OUTPUT_SHORT_FLOAT (asm_out_file, d);
      break;
#endif
#ifdef ASM_OUTPUT_THREE_QUARTER_FLOAT
    case TQFmode:
      ASM_OUTPUT_THREE_QUARTER_FLOAT (asm_out_file, d);
      break;
#endif
#ifdef ASM_OUTPUT_FLOAT
    case SFmode:
      ASM_OUTPUT_FLOAT (asm_out_file, d);
      break;
#endif

#ifdef ASM_OUTPUT_DOUBLE
    case DFmode:
      ASM_OUTPUT_DOUBLE (asm_out_file, d);
      break;
#endif

#ifdef ASM_OUTPUT_LONG_DOUBLE
    case XFmode:
    case TFmode:
      ASM_OUTPUT_LONG_DOUBLE (asm_out_file, d);
      break;
#endif

    default:
      abort ();
    }

  set_float_handler (NULL_PTR);
}

/* Here we combine duplicate floating constants to make
   CONST_DOUBLE rtx's, and force those out to memory when necessary.  */

/* Chain of all CONST_DOUBLE rtx's constructed for the current function.
   They are chained through the CONST_DOUBLE_CHAIN.
   A CONST_DOUBLE rtx has CONST_DOUBLE_MEM != cc0_rtx iff it is on this chain.
   In that case, CONST_DOUBLE_MEM is either a MEM,
   or const0_rtx if no MEM has been made for this CONST_DOUBLE yet.

   (CONST_DOUBLE_MEM is used only for top-level functions.
   See force_const_mem for explanation.)  */

static rtx const_double_chain;

/* Return a CONST_DOUBLE or CONST_INT for a value specified as a pair of ints.
   For an integer, I0 is the low-order word and I1 is the high-order word.
   For a real number, I0 is the word with the low address
   and I1 is the word with the high address.  */

rtx
immed_double_const (i0, i1, mode)
     HOST_WIDE_INT i0, i1;
     enum machine_mode mode;
{
  register rtx r;
  int in_current_obstack;

  if (GET_MODE_CLASS (mode) == MODE_INT
      || GET_MODE_CLASS (mode) == MODE_PARTIAL_INT)
    {
      /* We clear out all bits that don't belong in MODE, unless they and our
	 sign bit are all one.  So we get either a reasonable negative value
	 or a reasonable unsigned value for this mode.  */
      int width = GET_MODE_BITSIZE (mode);
      if (width < HOST_BITS_PER_WIDE_INT
	  && ((i0 & ((HOST_WIDE_INT) (-1) << (width - 1)))