varasm.c

gcc库的原代码,对编程有很大帮助.

    {
      bc_make_decl_rtl (decl, asmspec, top_level);
      return;
    }

  reg_number = decode_reg_name (asmspec);

  if (DECL_ASSEMBLER_NAME (decl) != NULL_TREE)
    name = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl));

  if (reg_number == -2)
    {
      /* ASMSPEC is given, and not the name of a register.  */
      name = (char *) obstack_alloc (saveable_obstack,
				     strlen (asmspec) + 2);
      name[0] = '*';
      strcpy (&name[1], asmspec);
    }

  /* For a duplicate declaration, we can be called twice on the
     same DECL node.  Don't discard the RTL already made.  */
  if (DECL_RTL (decl) == 0)
    {
      DECL_RTL (decl) = 0;

      /* First detect errors in declaring global registers.  */
      if (DECL_REGISTER (decl) && reg_number == -1)
	error_with_decl (decl,
			 "register name not specified for `%s'");
      else if (DECL_REGISTER (decl) && reg_number < 0)
	error_with_decl (decl,
			 "invalid register name for `%s'");
      else if ((reg_number >= 0 || reg_number == -3) && ! DECL_REGISTER (decl))
	error_with_decl (decl,
			 "register name given for non-register variable `%s'");
      else if (DECL_REGISTER (decl) && TREE_CODE (decl) == FUNCTION_DECL)
	error ("function declared `register'");
      else if (DECL_REGISTER (decl) && TYPE_MODE (TREE_TYPE (decl)) == BLKmode)
	error_with_decl (decl, "data type of `%s' isn't suitable for a register");
      else if (DECL_REGISTER (decl)
	       && ! HARD_REGNO_MODE_OK (reg_number, TYPE_MODE (TREE_TYPE (decl))))
	error_with_decl (decl, "register number for `%s' isn't suitable for the data type");
      /* Now handle properly declared static register variables.  */
      else if (DECL_REGISTER (decl))
	{
	  int nregs;
#if 0 /* yylex should print the warning for this */
	  if (pedantic)
	    pedwarn ("ANSI C forbids global register variables");
#endif
	  if (DECL_INITIAL (decl) != 0 && top_level)
	    {
	      DECL_INITIAL (decl) = 0;
	      error ("global register variable has initial value");
	    }
	  if (fixed_regs[reg_number] == 0
	      && function_defined && top_level)
	    error ("global register variable follows a function definition");
	  if (TREE_THIS_VOLATILE (decl))
	    warning ("volatile register variables don't work as you might wish");

	  /* If the user specified one of the eliminables registers here,
	     e.g., FRAME_POINTER_REGNUM, we don't want to get this variable
	     confused with that register and be eliminated.  Although this
	     usage is somewhat suspect, we nevertheless use the following
	     kludge to avoid setting DECL_RTL to frame_pointer_rtx.  */

	  DECL_RTL (decl)
	    = gen_rtx (REG, DECL_MODE (decl), FIRST_PSEUDO_REGISTER);
	  REGNO (DECL_RTL (decl)) = reg_number;
	  REG_USERVAR_P (DECL_RTL (decl)) = 1;

	  if (top_level)
	    {
	      /* Make this register global, so not usable for anything
		 else.  */
	      nregs = HARD_REGNO_NREGS (reg_number, DECL_MODE (decl));
	      while (nregs > 0)
		globalize_reg (reg_number + --nregs);
	    }
	}
      /* Specifying a section attribute on an uninitialized variable does not
	 (and cannot) cause it to be put in the given section.  The linker
	 can only put initialized objects in specific sections, everything
	 else goes in bss for the linker to sort out later (otherwise the
	 linker would give a duplicate definition error for each compilation
	 unit that behaved thusly).  So warn the user.  */
      else if (TREE_CODE (decl) == VAR_DECL
	       && DECL_SECTION_NAME (decl) != NULL_TREE
	       && DECL_INITIAL (decl) == NULL_TREE
	       && DECL_COMMON (decl)
	       && ! flag_no_common)
	{
	  warning_with_decl (decl,
			     "section attribute ignored for uninitialized variable `%s'");
	  /* Remove the section name so subsequent declarations won't see it.
	     We are ignoring it, remember.  */
	  DECL_SECTION_NAME (decl) = NULL_TREE;
	}

      /* Now handle ordinary static variables and functions (in memory).
	 Also handle vars declared register invalidly.  */
      if (DECL_RTL (decl) == 0)
	{
	  /* Can't use just the variable's own name for a variable
	     whose scope is less than the whole file.
	     Concatenate a distinguishing number.  */
	  if (!top_level && !DECL_EXTERNAL (decl) && asmspec == 0)
	    {
	      char *label;

	      ASM_FORMAT_PRIVATE_NAME (label, name, var_labelno);
	      name = obstack_copy0 (saveable_obstack, label, strlen (label));
	      var_labelno++;
	    }

	  if (name == 0)
	    abort ();

	  DECL_RTL (decl) = gen_rtx (MEM, DECL_MODE (decl),
				     gen_rtx (SYMBOL_REF, Pmode, name));

	  /* If this variable is to be treated as volatile, show its
	     tree node has side effects.  If it has side effects, either
	     because of this test or from TREE_THIS_VOLATILE also
	     being set, show the MEM is volatile.  */
	  if (flag_volatile_global && TREE_CODE (decl) == VAR_DECL
	      && TREE_PUBLIC (decl))
	    TREE_SIDE_EFFECTS (decl) = 1;
	  if (TREE_SIDE_EFFECTS (decl))
	    MEM_VOLATILE_P (DECL_RTL (decl)) = 1;

	  if (TREE_READONLY (decl))
	    RTX_UNCHANGING_P (DECL_RTL (decl)) = 1;
	  MEM_IN_STRUCT_P (DECL_RTL (decl))
	    = AGGREGATE_TYPE_P (TREE_TYPE (decl));

	  /* Optionally set flags or add text to the name to record information
	     such as that it is a function name.
	     If the name is changed, the macro ASM_OUTPUT_LABELREF
	     will have to know how to strip this information.  */
#ifdef ENCODE_SECTION_INFO
	  ENCODE_SECTION_INFO (decl);
#endif
	}
    }
  /* If the old RTL had the wrong mode, fix the mode.  */
  else if (GET_MODE (DECL_RTL (decl)) != DECL_MODE (decl))
    {
      rtx rtl = DECL_RTL (decl);
      PUT_MODE (rtl, DECL_MODE (decl));
    }
}

/* Make the rtl for variable VAR be volatile.
   Use this only for static variables.  */

void
make_var_volatile (var)
     tree var;
{
  if (GET_CODE (DECL_RTL (var)) != MEM)
    abort ();

  MEM_VOLATILE_P (DECL_RTL (var)) = 1;
}

/* Output alignment directive to align for constant expression EXP.  */

void
assemble_constant_align (exp)
     tree exp;
{
  int align;

  /* Align the location counter as required by EXP's data type.  */
  align = TYPE_ALIGN (TREE_TYPE (exp));
#ifdef CONSTANT_ALIGNMENT
  align = CONSTANT_ALIGNMENT (exp, align);
#endif

  if (align > BITS_PER_UNIT)
    ASM_OUTPUT_ALIGN (asm_out_file, floor_log2 (align / BITS_PER_UNIT));
}

/* Output a string of literal assembler code
   for an `asm' keyword used between functions.  */

void
assemble_asm (string)
     tree string;
{
  if (output_bytecode)
    {
      error ("asm statements not allowed in interpreter");
      return;
    }

  app_enable ();

  if (TREE_CODE (string) == ADDR_EXPR)
    string = TREE_OPERAND (string, 0);

  fprintf (asm_out_file, "\t%s\n", TREE_STRING_POINTER (string));
}

#if 0 /* This should no longer be needed, because
	 flag_gnu_linker should be 0 on these systems,
	 which should prevent any output
	 if ASM_OUTPUT_CONSTRUCTOR and ASM_OUTPUT_DESTRUCTOR are absent.  */
#if !(defined(DBX_DEBUGGING_INFO) && !defined(FASCIST_ASSEMBLER))
#ifndef ASM_OUTPUT_CONSTRUCTOR
#define ASM_OUTPUT_CONSTRUCTOR(file, name)
#endif
#ifndef ASM_OUTPUT_DESTRUCTOR
#define ASM_OUTPUT_DESTRUCTOR(file, name)
#endif
#endif
#endif /* 0 */

/* Record an element in the table of global destructors.
   How this is done depends on what sort of assembler and linker
   are in use.

   NAME should be the name of a global function to be called
   at exit time.  This name is output using assemble_name.  */

void
assemble_destructor (name)
     char *name;
{
#ifdef ASM_OUTPUT_DESTRUCTOR
  ASM_OUTPUT_DESTRUCTOR (asm_out_file, name);
#else
  if (flag_gnu_linker)
    {
      /* Now tell GNU LD that this is part of the static destructor set.  */
      /* This code works for any machine provided you use GNU as/ld.  */
      fprintf (asm_out_file, "%s \"___DTOR_LIST__\",22,0,0,", ASM_STABS_OP);
      assemble_name (asm_out_file, name);
      fputc ('\n', asm_out_file);
    }
#endif
}

/* Likewise for global constructors.  */

void
assemble_constructor (name)
     char *name;
{
#ifdef ASM_OUTPUT_CONSTRUCTOR
  ASM_OUTPUT_CONSTRUCTOR (asm_out_file, name);
#else
  if (flag_gnu_linker)
    {
      /* Now tell GNU LD that this is part of the static constructor set.  */
      /* This code works for any machine provided you use GNU as/ld.  */
      fprintf (asm_out_file, "%s \"___CTOR_LIST__\",22,0,0,", ASM_STABS_OP);
      assemble_name (asm_out_file, name);
      fputc ('\n', asm_out_file);
    }
#endif
}

/* Likewise for entries we want to record for garbage collection.
   Garbage collection is still under development.  */

void
assemble_gc_entry (name)
     char *name;
{
#ifdef ASM_OUTPUT_GC_ENTRY
  ASM_OUTPUT_GC_ENTRY (asm_out_file, name);
#else
  if (flag_gnu_linker)
    {
      /* Now tell GNU LD that this is part of the static constructor set.  */
      fprintf (asm_out_file, "%s \"___PTR_LIST__\",22,0,0,", ASM_STABS_OP);
      assemble_name (asm_out_file, name);
      fputc ('\n', asm_out_file);
    }
#endif
}

/* Output assembler code for the constant pool of a function and associated
   with defining the name of the function.  DECL describes the function.
   NAME is the function's name.  For the constant pool, we use the current
   constant pool data.  */

void
assemble_start_function (decl, fnname)
     tree decl;
     char *fnname;
{
  int align;

  /* The following code does not need preprocessing in the assembler.  */

  app_disable ();

  output_constant_pool (fnname, decl);

  function_section (decl);

  /* Tell assembler to move to target machine's alignment for functions.  */
  align = floor_log2 (FUNCTION_BOUNDARY / BITS_PER_UNIT);
  if (align > 0)
    {
      if (output_bytecode)
	BC_OUTPUT_ALIGN (asm_out_file, align);
      else
	ASM_OUTPUT_ALIGN (asm_out_file, align);
    }

#ifdef ASM_OUTPUT_FUNCTION_PREFIX
  ASM_OUTPUT_FUNCTION_PREFIX (asm_out_file, fnname);
#endif

#ifdef SDB_DEBUGGING_INFO
  /* Output SDB definition of the function.  */
  if (write_symbols == SDB_DEBUG)
    sdbout_mark_begin_function ();
#endif

#ifdef DBX_DEBUGGING_INFO
  /* Output DBX definition of the function.  */
  if (write_symbols == DBX_DEBUG)
    dbxout_begin_function (decl);
#endif

  /* Make function name accessible from other files, if appropriate.  */

  if (TREE_PUBLIC (decl))
    {
      if (!first_global_object_name)
	{
	  char *p;

	  STRIP_NAME_ENCODING (p, fnname);
	  first_global_object_name = permalloc (strlen (p) + 1);
	  strcpy (first_global_object_name, p);
	}

#ifdef ASM_WEAKEN_LABEL
      if (DECL_WEAK (decl))
	ASM_WEAKEN_LABEL (asm_out_file, fnname);
      else
#endif
      if (output_bytecode)
	BC_GLOBALIZE_LABEL (asm_out_file, fnname);
      else
	ASM_GLOBALIZE_LABEL (asm_out_file, fnname);
    }

  /* Do any machine/system dependent processing of the function name */
#ifdef ASM_DECLARE_FUNCTION_NAME
  ASM_DECLARE_FUNCTION_NAME (asm_out_file, fnname, current_function_decl);
#else
  /* Standard thing is just output label for the function.  */
  if (output_bytecode)
    BC_OUTPUT_LABEL (asm_out_file, fnname);
  else
    ASM_OUTPUT_LABEL (asm_out_file, fnname);
#endif /* ASM_DECLARE_FUNCTION_NAME */
}

/* Output assembler code associated with defining the size of the
   function.  DECL describes the function.  NAME is the function's name.  */

void
assemble_end_function (decl, fnname)
     tree decl;
     char *fnname;
{
#ifdef ASM_DECLARE_FUNCTION_SIZE
  ASM_DECLARE_FUNCTION_SIZE (asm_out_file, fnname, decl);
#endif
}

/* Assemble code to leave SIZE bytes of zeros.  */

void
assemble_zeros (size)
     int size;
{
  if (output_bytecode)
    {
      bc_emit_const_skip (size);
      return;
    }

#ifdef ASM_NO_SKIP_IN_TEXT
  /* The `space' pseudo in the text section outputs nop insns rather than 0s,
     so we must output 0s explicitly in the text section.  */
  if (ASM_NO_SKIP_IN_TEXT && in_text_section ())
    {
      int i;

      for (i = 0; i < size - 20; i += 20)
	{
#ifdef ASM_BYTE_OP
	  fprintf (asm_out_file,
		   "%s 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0\n", ASM_BYTE_OP);
#else
	  fprintf (asm_out_file,
		   "\tbyte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0\n");
#endif
	}
      if (i < size)
        {
#ifdef ASM_BYTE_OP
	  fprintf (asm_out_file, "%s 0", ASM_BYTE_OP);
#else
	  fprintf (asm_out_file, "\tbyte 0");
#endif
	  i++;
	  for (; i < size; i++)
	    fprintf (asm_out_file, ",0");
	  fprintf (asm_out_file, "\n");
	}
    }
  else
#endif
    if (size > 0)
      {
	if (output_bytecode)
	  BC_OUTPUT_SKIP (asm_out_file, size);
	else
	  ASM_OUTPUT_SKIP (asm_out_file, size);
      }
}

/* Assemble an alignment pseudo op for an ALIGN-bit boundary.  */

void
assemble_align (align)
     int align;
{
  if (align > BITS_PER_UNIT)
    ASM_OUTPUT_ALIGN (asm_out_file, floor_log2 (align / BITS_PER_UNIT));
}

/* Assemble a string constant with the specified C string as contents.  */

void
assemble_string (p, size)
     char *p;
     int size;
{
  register int i;
  int pos = 0;
  int maximum = 2000;

  if (output_bytecode)
    {
      bc_emit (p, size);
      return;
    }

  /* If the string is very long, split it up.  */

  while (pos < size)
    {
      int thissize = size - pos;
      if (thissize > maximum)
	thissize = maximum;