m32r.c

gcc-you can use this code to learn something about gcc, and inquire further into linux,

  /* See if this is an interrupt handler.  Call used registers must be saved
     for them too.  */
  fn_type = m32r_compute_function_type (current_function_decl);
  interrupt_p = M32R_INTERRUPT_P (fn_type);

  /* Calculate space needed for registers.  */

  for (regno = 0; regno < M32R_MAX_INT_REGS; regno++)
    {
      if (MUST_SAVE_REGISTER (regno, interrupt_p))
	{
	  reg_size += UNITS_PER_WORD;
	  gmask |= 1 << regno;
	}
    }

  current_frame_info.save_fp = MUST_SAVE_FRAME_POINTER;
  current_frame_info.save_lr = MUST_SAVE_RETURN_ADDR;

  reg_size += ((current_frame_info.save_fp + current_frame_info.save_lr)
	       * UNITS_PER_WORD);
  total_size += reg_size;

  /* ??? Not sure this is necessary, and I don't think the epilogue
     handler will do the right thing if this changes total_size.  */
  total_size = M32R_STACK_ALIGN (total_size);

  frame_size = total_size - (pretend_size + reg_size);

  /* Save computed information.  */
  current_frame_info.total_size   = total_size;
  current_frame_info.extra_size   = extra_size;
  current_frame_info.pretend_size = pretend_size;
  current_frame_info.var_size     = var_size;
  current_frame_info.args_size    = args_size;
  current_frame_info.reg_size	  = reg_size;
  current_frame_info.gmask	  = gmask;
  current_frame_info.initialized  = reload_completed;

  /* Ok, we're done.  */
  return total_size;
}

/* When the `length' insn attribute is used, this macro specifies the
   value to be assigned to the address of the first insn in a
   function.  If not specified, 0 is used.  */

int
m32r_first_insn_address ()
{
  if (! current_frame_info.initialized)
    m32r_compute_frame_size (get_frame_size ());

  return 0;
}

/* Expand the m32r prologue as a series of insns.  */

void
m32r_expand_prologue ()
{
  int regno;
  int frame_size;
  unsigned int gmask;

  if (! current_frame_info.initialized)
    m32r_compute_frame_size (get_frame_size ());

  gmask = current_frame_info.gmask;

  /* These cases shouldn't happen.  Catch them now.  */
  if (current_frame_info.total_size == 0 && gmask)
    abort ();

  /* Allocate space for register arguments if this is a variadic function.  */
  if (current_frame_info.pretend_size != 0)
    {
      /* Use a HOST_WIDE_INT temporary, since negating an unsigned int gives
	 the wrong result on a 64-bit host.  */
      HOST_WIDE_INT pretend_size = current_frame_info.pretend_size;
      emit_insn (gen_addsi3 (stack_pointer_rtx,
			     stack_pointer_rtx,
			     GEN_INT (-pretend_size)));
    }

  /* Save any registers we need to and set up fp.  */

  if (current_frame_info.save_fp)
    emit_insn (gen_movsi_push (stack_pointer_rtx, frame_pointer_rtx));

  gmask &= ~(FRAME_POINTER_MASK | RETURN_ADDR_MASK);

  /* Save any needed call-saved regs (and call-used if this is an
     interrupt handler).  */
  for (regno = 0; regno <= M32R_MAX_INT_REGS; ++regno)
    {
      if ((gmask & (1 << regno)) != 0)
	emit_insn (gen_movsi_push (stack_pointer_rtx,
				   gen_rtx_REG (Pmode, regno)));
    }

  if (current_frame_info.save_lr)
    emit_insn (gen_movsi_push (stack_pointer_rtx,
			       gen_rtx_REG (Pmode, RETURN_ADDR_REGNUM)));

  /* Allocate the stack frame.  */
  frame_size = (current_frame_info.total_size
		- (current_frame_info.pretend_size
		   + current_frame_info.reg_size));

  if (frame_size == 0)
    ; /* nothing to do */
  else if (frame_size <= 32768)
    emit_insn (gen_addsi3 (stack_pointer_rtx, stack_pointer_rtx,
			   GEN_INT (-frame_size)));
  else
    {
      rtx tmp = gen_rtx_REG (Pmode, PROLOGUE_TMP_REGNUM);
      emit_insn (gen_movsi (tmp, GEN_INT (frame_size)));
      emit_insn (gen_subsi3 (stack_pointer_rtx, stack_pointer_rtx, tmp));
    }

  if (frame_pointer_needed)
    emit_insn (gen_movsi (frame_pointer_rtx, stack_pointer_rtx));

  if (current_function_profile)
    emit_insn (gen_blockage ());
}


/* Set up the stack and frame pointer (if desired) for the function.
   Note, if this is changed, you need to mirror the changes in
   m32r_compute_frame_size which calculates the prolog size.  */

static void
m32r_output_function_prologue (file, size)
     FILE * file;
     HOST_WIDE_INT size;
{
  enum m32r_function_type fn_type = m32r_compute_function_type (current_function_decl);

  /* If this is an interrupt handler, mark it as such.  */
  if (M32R_INTERRUPT_P (fn_type))
    {
      fprintf (file, "\t%s interrupt handler\n",
	       ASM_COMMENT_START);
    }

  if (! current_frame_info.initialized)
    m32r_compute_frame_size (size);

  /* This is only for the human reader.  */
  fprintf (file,
	   "\t%s PROLOGUE, vars= %d, regs= %d, args= %d, extra= %d\n",
	   ASM_COMMENT_START,
	   current_frame_info.var_size,
	   current_frame_info.reg_size / 4,
	   current_frame_info.args_size,
	   current_frame_info.extra_size);
}

/* Do any necessary cleanup after a function to restore stack, frame,
   and regs. */

static void
m32r_output_function_epilogue (file, size)
     FILE * file;
     HOST_WIDE_INT size ATTRIBUTE_UNUSED;
{
  int regno;
  int noepilogue = FALSE;
  int total_size;
  enum m32r_function_type fn_type = m32r_compute_function_type (current_function_decl);

  /* This is only for the human reader.  */
  fprintf (file, "\t%s EPILOGUE\n", ASM_COMMENT_START);

  if (!current_frame_info.initialized)
    abort ();
  total_size = current_frame_info.total_size;

  if (total_size == 0)
    {
      rtx insn = get_last_insn ();

      /* If the last insn was a BARRIER, we don't have to write any code
	 because a jump (aka return) was put there.  */
      if (GET_CODE (insn) == NOTE)
	insn = prev_nonnote_insn (insn);
      if (insn && GET_CODE (insn) == BARRIER)
	noepilogue = TRUE;
    }

  if (!noepilogue)
    {
      unsigned int var_size = current_frame_info.var_size;
      unsigned int args_size = current_frame_info.args_size;
      unsigned int gmask = current_frame_info.gmask;
      int can_trust_sp_p = !current_function_calls_alloca;
      const char * sp_str = reg_names[STACK_POINTER_REGNUM];
      const char * fp_str = reg_names[FRAME_POINTER_REGNUM];

      /* The first thing to do is point the sp at the bottom of the register
	 save area.  */
      if (can_trust_sp_p)
	{
	  unsigned int reg_offset = var_size + args_size;
	  if (reg_offset == 0)
	    ; /* nothing to do */
	  else if (reg_offset < 128)
	    fprintf (file, "\taddi %s,%s%d\n",
		     sp_str, IMMEDIATE_PREFIX, reg_offset);
	  else if (reg_offset < 32768)
	    fprintf (file, "\tadd3 %s,%s,%s%d\n",
		     sp_str, sp_str, IMMEDIATE_PREFIX, reg_offset);
	  else
	    fprintf (file, "\tld24 %s,%s%d\n\tadd %s,%s\n",
		     reg_names[PROLOGUE_TMP_REGNUM],
		     IMMEDIATE_PREFIX, reg_offset,
		     sp_str, reg_names[PROLOGUE_TMP_REGNUM]);
	}
      else if (frame_pointer_needed)
	{
	  unsigned int reg_offset = var_size + args_size;
	  if (reg_offset == 0)
	    fprintf (file, "\tmv %s,%s\n", sp_str, fp_str);
	  else if (reg_offset < 32768)
	    fprintf (file, "\tadd3 %s,%s,%s%d\n",
		     sp_str, fp_str, IMMEDIATE_PREFIX, reg_offset);
	  else
	    fprintf (file, "\tld24 %s,%s%d\n\tadd %s,%s\n",
		     reg_names[PROLOGUE_TMP_REGNUM],
		     IMMEDIATE_PREFIX, reg_offset,
		     sp_str, reg_names[PROLOGUE_TMP_REGNUM]);
	}
      else
	abort ();

      if (current_frame_info.save_lr)
	fprintf (file, "\tpop %s\n", reg_names[RETURN_ADDR_REGNUM]);

      /* Restore any saved registers, in reverse order of course.  */
      gmask &= ~(FRAME_POINTER_MASK | RETURN_ADDR_MASK);
      for (regno = M32R_MAX_INT_REGS - 1; regno >= 0; --regno)
	{
	  if ((gmask & (1L << regno)) != 0)
	    fprintf (file, "\tpop %s\n", reg_names[regno]);
	}

      if (current_frame_info.save_fp)
	fprintf (file, "\tpop %s\n", fp_str);

      /* Remove varargs area if present.  */
      if (current_frame_info.pretend_size != 0)
	fprintf (file, "\taddi %s,%s%d\n",
		 sp_str, IMMEDIATE_PREFIX, current_frame_info.pretend_size);
	
      /* Emit the return instruction.  */
      if (M32R_INTERRUPT_P (fn_type))
	fprintf (file, "\trte\n");
      else
	fprintf (file, "\tjmp %s\n", reg_names[RETURN_ADDR_REGNUM]);
    }

#if 0 /* no longer needed */
  /* Ensure the function cleanly ends on a 32 bit boundary.  */
  fprintf (file, "\t.fillinsn\n");
#endif

  /* Reset state info for each function.  */
  current_frame_info = zero_frame_info;
  m32r_compute_function_type (NULL_TREE);
}

/* Return nonzero if this function is known to have a null or 1 instruction
   epilogue.  */

int
direct_return ()
{
  if (!reload_completed)
    return FALSE;

  if (! current_frame_info.initialized)
    m32r_compute_frame_size (get_frame_size ());

  return current_frame_info.total_size == 0;
}


/* PIC */

/* Emit special PIC prologues and epilogues.  */

void
m32r_finalize_pic ()
{
  /* nothing to do */
}

/* Nested function support.  */

/* Emit RTL insns to initialize the variable parts of a trampoline.
   FNADDR is an RTX for the address of the function's pure code.
   CXT is an RTX for the static chain value for the function.  */

void
m32r_initialize_trampoline (tramp, fnaddr, cxt)
     rtx tramp ATTRIBUTE_UNUSED;
     rtx fnaddr ATTRIBUTE_UNUSED;
     rtx cxt ATTRIBUTE_UNUSED;
{
}

/* Set the cpu type and print out other fancy things,
   at the top of the file.  */

void
m32r_asm_file_start (file)
     FILE * file;
{
  if (flag_verbose_asm)
    fprintf (file, "%s M32R/D special options: -G %d\n",
	     ASM_COMMENT_START, g_switch_value);
}

/* Print operand X (an rtx) in assembler syntax to file FILE.
   CODE is a letter or dot (`z' in `%z0') or 0 if no letter was specified.
   For `%' followed by punctuation, CODE is the punctuation and X is null.  */

void
m32r_print_operand (file, x, code)
     FILE * file;
     rtx    x;
     int    code;
{
  rtx addr;

  switch (code)
    {
      /* The 's' and 'p' codes are used by output_block_move() to
	 indicate post-increment 's'tores and 'p're-increment loads.  */
    case 's':
      if (GET_CODE (x) == REG)
	fprintf (file, "@+%s", reg_names [REGNO (x)]);
      else
	output_operand_lossage ("invalid operand to %%s code");
      return;
      
    case 'p':
      if (GET_CODE (x) == REG)
	fprintf (file, "@%s+", reg_names [REGNO (x)]);
      else
	output_operand_lossage ("invalid operand to %%p code");
      return;

    case 'R' :
      /* Write second word of DImode or DFmode reference,
	 register or memory.  */
      if (GET_CODE (x) == REG)
	fputs (reg_names[REGNO (x)+1], file);
      else if (GET_CODE (x) == MEM)
	{
	  fprintf (file, "@(");
	  /* Handle possible auto-increment.  Since it is pre-increment and
	     we have already done it, we can just use an offset of four.  */
	  /* ??? This is taken from rs6000.c I think.  I don't think it is
	     currently necessary, but keep it around.  */
	  if (GET_CODE (XEXP (x, 0)) == PRE_INC
	      || GET_CODE (XEXP (x, 0)) == PRE_DEC)
	    output_address (plus_constant (XEXP (XEXP (x, 0), 0), 4));
	  else
	    output_address (plus_constant (XEXP (x, 0), 4));
	  fputc (')', file);
	}
      else
	output_operand_lossage ("invalid operand to %%R code");
      return;

    case 'H' : /* High word */
    case 'L' : /* Low word */
      if (GET_CODE (x) == REG)
	{
	  /* L = least significant word, H = most significant word */
	  if ((WORDS_BIG_ENDIAN != 0) ^ (code == 'L'))
	    fputs (reg_names[REGNO (x)], file);
	  else
	    fputs (reg_names[REGNO (x)+1], file);
	}
      else if (GET_CODE (x) == CONST_INT
	       || GET_CODE (x) == CONST_DOUBLE)
	{
	  rtx first, second;

	  split_double (x, &first, &second);
	  fprintf (file, HOST_WIDE_INT_PRINT_HEX,
		   code == 'L' ? INTVAL (first) : INTVAL (second));
	}
      else
	output_operand_lossage ("invalid operand to %%H/%%L code");
      return;

    case 'A' :
      {
	char str[30];

	if (GET_CODE (x) != CONST_DOUBLE
	    || GET_MODE_CLASS (GET_MODE (x)) != MODE_FLOAT)
	  fatal_insn ("bad insn for 'A'", x);

	real_to_decimal (str, CONST_DOUBLE_REAL_VALUE (x), sizeof (str), 0, 1);
	fprintf (file, "%s", str);
	return;
      }

    case 'B' : /* Bottom half */
    case 'T' : /* Top half */
      /* Output the argument to a `seth' insn (sets the Top half-word).
	 For constants output arguments to a seth/or3 pair to set Top and
	 Bottom halves.  For symbols output arguments to a seth/add3 pair to
	 set Top and Bottom halves.  The difference exists because for
	 constants seth/or3 is more readable but for symbols we need to use
	 the same scheme as `ld' and `st' insns (16 bit addend is signed).  */
      switch (GET_CODE (x))
	{
	case CONST_INT :
	case CONST_DOUBLE :
	  {
	    rtx first, second;

	    split_double (x, &first, &second);
	    x = WORDS_BIG_ENDIAN ? second : first;
	    fprintf (file,
#if HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_INT
		     "0x%x",
#else
		     "0x%lx",
#endif
		     (code == 'B'
		      ? INTVAL (x) & 0xffff
		      : (INTVAL (x) >> 16) & 0xffff));
	  }
	  return;
	case CONST :
	case SYMBOL_REF :
	  if (code == 'B'
	      && small_data_operand (x, VOIDmode))
	    {
	      fputs ("sda(", file);
	      output_addr_const (file, x);
	      fputc (')', file);
	      return;
	    }
	  /* fall through */
	case LABEL_REF :
	  fputs (code == 'T' ? "shigh(" : "low(", file);
	  output_addr_const (file, x);
	  fputc (')', file);
	  return;
	default :
	  output_operand_lossage ("invalid operand to %%T/%%B code");
	  return;
	}
      break;

    case 'U' :
      /* ??? wip */
      /* Output a load/store with update indicator if appropriate.  */
      if (GET_CODE (x) == MEM)
	{
	  if (GET_CODE (XEXP (x, 0)) == PRE_INC
	      || GET_CODE (XEXP (x, 0)) == PRE_DEC)
	    fputs (".a", file);
	}
      else
	output