m68hc11.c

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

      cum->words += int_size_in_bytes (type);
    }
  return;
}

/* Define where to put the arguments to a function.
   Value is zero to push the argument on the stack,
   or a hard register in which to store the argument.

   MODE is the argument's machine mode.
   TYPE is the data type of the argument (as a tree).
    This is null for libcalls where that information may
    not be available.
   CUM is a variable of type CUMULATIVE_ARGS which gives info about
    the preceding args and about the function being called.
   NAMED is nonzero if this argument is a named parameter
    (otherwise it is an extra parameter matching an ellipsis).  */

struct rtx_def *
m68hc11_function_arg (cum, mode, type, named)
     const CUMULATIVE_ARGS *cum;
     enum machine_mode mode;
     tree type ATTRIBUTE_UNUSED;
     int named ATTRIBUTE_UNUSED;
{
  if (cum->words != 0)
    {
      return NULL_RTX;
    }

  if (mode != BLKmode)
    {
      if (GET_MODE_SIZE (mode) == 2 * HARD_REG_SIZE)
	return gen_rtx (REG, mode, HARD_X_REGNUM);

      if (GET_MODE_SIZE (mode) > HARD_REG_SIZE)
	{
	  return NULL_RTX;
	}
      return gen_rtx (REG, mode, HARD_D_REGNUM);
    }
  return NULL_RTX;
}

/* If defined, a C expression which determines whether, and in which direction,
   to pad out an argument with extra space.  The value should be of type
   `enum direction': either `upward' to pad above the argument,
   `downward' to pad below, or `none' to inhibit padding.

   Structures are stored left shifted in their argument slot.  */
int
m68hc11_function_arg_padding (mode, type)
     enum machine_mode mode;
     tree type;
{
  if (type != 0 && AGGREGATE_TYPE_P (type))
    return upward;

  /* This is the default definition.  */
  return (!BYTES_BIG_ENDIAN
	  ? upward
	  : ((mode == BLKmode
	      ? (type && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
		 && int_size_in_bytes (type) <
		 (PARM_BOUNDARY / BITS_PER_UNIT)) : GET_MODE_BITSIZE (mode) <
	      PARM_BOUNDARY) ? downward : upward));
}


/* Function prologue and epilogue.  */

/* Emit a move after the reload pass has completed.  This is used to
   emit the prologue and epilogue.  */
static void
emit_move_after_reload (to, from, scratch)
     rtx to, from, scratch;
{
  rtx insn;

  if (TARGET_M6812 || H_REG_P (to) || H_REG_P (from))
    {
      insn = emit_move_insn (to, from);
    }
  else
    {
      emit_move_insn (scratch, from);
      insn = emit_move_insn (to, scratch);
    }

  /* Put a REG_INC note to tell the flow analysis that the instruction
     is necessary.  */
  if (IS_STACK_PUSH (to))
    {
      REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_INC,
					    XEXP (XEXP (to, 0), 0),
					    REG_NOTES (insn));
    }
  else if (IS_STACK_POP (from))
    {
      REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_INC,
					    XEXP (XEXP (from, 0), 0),
					    REG_NOTES (insn));
    }

  /* For 68HC11, put a REG_INC note on `sts _.frame' to prevent the cse-reg
     to think that sp == _.frame and later replace a x = sp with x = _.frame.
     The problem is that we are lying to gcc and use `txs' for x = sp
     (which is not really true because txs is really x = sp + 1).  */
  else if (TARGET_M6811 && SP_REG_P (from))
    {
      REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_INC,
					    from,
					    REG_NOTES (insn));
    }
}

int
m68hc11_total_frame_size ()
{
  int size;
  int regno;

  size = get_frame_size ();
  if (current_function_interrupt)
    {
      size += 3 * HARD_REG_SIZE;
    }
  if (frame_pointer_needed)
    size += HARD_REG_SIZE;

  for (regno = SOFT_REG_FIRST; regno <= SOFT_REG_LAST; regno++)
    if (regs_ever_live[regno] && !call_used_regs[regno])
      size += HARD_REG_SIZE;

  return size;
}

static void
m68hc11_output_function_epilogue (out, size)
     FILE *out ATTRIBUTE_UNUSED;
     HOST_WIDE_INT size ATTRIBUTE_UNUSED;
{
  /* We catch the function epilogue generation to have a chance
     to clear the z_replacement_completed flag.  */
  z_replacement_completed = 0;
}

void
expand_prologue ()
{
  tree func_attr;
  int size;
  int regno;
  rtx scratch;

  if (reload_completed != 1)
    abort ();

  size = get_frame_size ();

  create_regs_rtx ();

  /* Generate specific prologue for interrupt handlers.  */
  func_attr = TYPE_ATTRIBUTES (TREE_TYPE (current_function_decl));
  current_function_interrupt = lookup_attribute ("interrupt",
						 func_attr) != NULL_TREE;
  current_function_trap = lookup_attribute ("trap", func_attr) != NULL_TREE;
  if (lookup_attribute ("far", func_attr) != NULL_TREE)
    current_function_far = 1;
  else if (lookup_attribute ("near", func_attr) != NULL_TREE)
    current_function_far = 0;
  else
    current_function_far = TARGET_LONG_CALLS != 0;

  /* Get the scratch register to build the frame and push registers.
     If the first argument is a 32-bit quantity, the D+X registers
     are used.  Use Y to compute the frame.  Otherwise, X is cheaper.
     For 68HC12, this scratch register is not used.  */
  if (current_function_args_info.nregs == 2)
    scratch = iy_reg;
  else
    scratch = ix_reg;

  /* Save current stack frame.  */
  if (frame_pointer_needed)
    emit_move_after_reload (stack_push_word, hard_frame_pointer_rtx, scratch);

  /* For an interrupt handler, we must preserve _.tmp, _.z and _.xy.
     Other soft registers in page0 need not to be saved because they
     will be restored by C functions.  For a trap handler, we don't
     need to preserve these registers because this is a synchronous call.  */
  if (current_function_interrupt)
    {
      emit_move_after_reload (stack_push_word, m68hc11_soft_tmp_reg, scratch);
      emit_move_after_reload (stack_push_word,
			      gen_rtx (REG, HImode, SOFT_Z_REGNUM), scratch);
      emit_move_after_reload (stack_push_word,
			      gen_rtx (REG, HImode, SOFT_SAVED_XY_REGNUM),
			      scratch);
    }

  /* Allocate local variables.  */
  if (TARGET_M6812 && (size > 4 || size == 3))
    {
      emit_insn (gen_addhi3 (stack_pointer_rtx,
			     stack_pointer_rtx, GEN_INT (-size)));
    }
  else if ((!optimize_size && size > 8) || (optimize_size && size > 10))
    {
      rtx insn;

      insn = gen_rtx_PARALLEL
	(VOIDmode,
	 gen_rtvec (2,
		    gen_rtx_SET (VOIDmode,
				 stack_pointer_rtx,
				 gen_rtx_PLUS (HImode,
					       stack_pointer_rtx,
					       GEN_INT (-size))),
		    gen_rtx_CLOBBER (VOIDmode, scratch)));
      emit_insn (insn);
    }
  else
    {
      int i;

      /* Allocate by pushing scratch values.  */
      for (i = 2; i <= size; i += 2)
	emit_move_after_reload (stack_push_word, ix_reg, 0);

      if (size & 1)
	emit_insn (gen_addhi3 (stack_pointer_rtx,
			       stack_pointer_rtx, GEN_INT (-1)));
    }

  /* Create the frame pointer.  */
  if (frame_pointer_needed)
    emit_move_after_reload (hard_frame_pointer_rtx,
			    stack_pointer_rtx, scratch);

  /* Push any 2 byte pseudo hard registers that we need to save.  */
  for (regno = SOFT_REG_FIRST; regno <= SOFT_REG_LAST; regno++)
    {
      if (regs_ever_live[regno] && !call_used_regs[regno])
	{
	  emit_move_after_reload (stack_push_word,
				  gen_rtx (REG, HImode, regno), scratch);
	}
    }
}

void
expand_epilogue ()
{
  int size;
  register int regno;
  int return_size;
  rtx scratch;

  if (reload_completed != 1)
    abort ();

  size = get_frame_size ();

  /* If we are returning a value in two registers, we have to preserve the
     X register and use the Y register to restore the stack and the saved
     registers.  Otherwise, use X because it's faster (and smaller).  */
  if (current_function_return_rtx == 0)
    return_size = 0;
  else if (GET_CODE (current_function_return_rtx) == MEM)
    return_size = HARD_REG_SIZE;
  else
    return_size = GET_MODE_SIZE (GET_MODE (current_function_return_rtx));

  if (return_size > HARD_REG_SIZE && return_size <= 2 * HARD_REG_SIZE)
    scratch = iy_reg;
  else
    scratch = ix_reg;

  /* Pop any 2 byte pseudo hard registers that we saved.  */
  for (regno = SOFT_REG_LAST; regno >= SOFT_REG_FIRST; regno--)
    {
      if (regs_ever_live[regno] && !call_used_regs[regno])
	{
	  emit_move_after_reload (gen_rtx (REG, HImode, regno),
				  stack_pop_word, scratch);
	}
    }

  /* de-allocate auto variables */
  if (TARGET_M6812 && (size > 4 || size == 3))
    {
      emit_insn (gen_addhi3 (stack_pointer_rtx,
			     stack_pointer_rtx, GEN_INT (size)));
    }
  else if ((!optimize_size && size > 8) || (optimize_size && size > 10))
    {
      rtx insn;

      insn = gen_rtx_PARALLEL
	(VOIDmode,
	 gen_rtvec (2,
		    gen_rtx_SET (VOIDmode,
				 stack_pointer_rtx,
				 gen_rtx_PLUS (HImode,
					       stack_pointer_rtx,
					       GEN_INT (size))),
		    gen_rtx_CLOBBER (VOIDmode, scratch)));
      emit_insn (insn);
    }
  else
    {
      int i;

      for (i = 2; i <= size; i += 2)
	emit_move_after_reload (scratch, stack_pop_word, scratch);
      if (size & 1)
	emit_insn (gen_addhi3 (stack_pointer_rtx,
			       stack_pointer_rtx, GEN_INT (1)));
    }

  /* For an interrupt handler, restore ZTMP, ZREG and XYREG.  */
  if (current_function_interrupt)
    {
      emit_move_after_reload (gen_rtx (REG, HImode, SOFT_SAVED_XY_REGNUM),
			      stack_pop_word, scratch);
      emit_move_after_reload (gen_rtx (REG, HImode, SOFT_Z_REGNUM),
			      stack_pop_word, scratch);
      emit_move_after_reload (m68hc11_soft_tmp_reg, stack_pop_word, scratch);
    }

  /* Restore previous frame pointer.  */
  if (frame_pointer_needed)
    emit_move_after_reload (hard_frame_pointer_rtx, stack_pop_word, scratch);

  /* If the trap handler returns some value, copy the value
     in D, X onto the stack so that the rti will pop the return value
     correctly.  */
  else if (current_function_trap && return_size != 0)
    {
      rtx addr_reg = stack_pointer_rtx;

      if (!TARGET_M6812)
	{
	  emit_move_after_reload (scratch, stack_pointer_rtx, 0);
	  addr_reg = scratch;
	}
      emit_move_after_reload (gen_rtx (MEM, HImode,
				       gen_rtx (PLUS, HImode, addr_reg,
						GEN_INT (1))), d_reg, 0);
      if (return_size > HARD_REG_SIZE)
	emit_move_after_reload (gen_rtx (MEM, HImode,
					 gen_rtx (PLUS, HImode, addr_reg,
						  GEN_INT (3))), ix_reg, 0);
    }

  emit_jump_insn (gen_return ());
}


/* Low and High part extraction for 68HC11.  These routines are
   similar to gen_lowpart and gen_highpart but they have been
   fixed to work for constants and 68HC11 specific registers.  */

rtx
m68hc11_gen_lowpart (mode, x)
     enum machine_mode mode;
     rtx x;
{
  /* We assume that the low part of an auto-inc mode is the same with
     the mode changed and that the caller split the larger mode in the
     correct order.  */
  if (GET_CODE (x) == MEM && m68hc11_auto_inc_p (XEXP (x, 0)))
    {
      return gen_rtx (MEM, mode, XEXP (x, 0));
    }

  /* Note that a CONST_DOUBLE rtx could represent either an integer or a
     floating-point constant.  A CONST_DOUBLE is used whenever the
     constant requires more than one word in order to be adequately
     represented.  */
  if (GET_CODE (x) == CONST_DOUBLE)
    {
      long l[2];

      if (GET_MODE_CLASS (GET_MODE (x)) == MODE_FLOAT)
	{
	  REAL_VALUE_TYPE r;

	  if (GET_MODE (x) == SFmode)
	    {
	      REAL_VALUE_FROM_CONST_DOUBLE (r, x);
	      REAL_VALUE_TO_TARGET_SINGLE (r, l[0]);
	    }
	  else
	    {
	      rtx first, second;

	      split_double (x, &first, &second);
	      return second;
	    }
	  if (mode == SImode)
	    return GEN_INT (l[0]);

	  return gen_int_mode (l[0], HImode);
	}
      else
	{
	  l[0] = CONST_DOUBLE_LOW (x);
	}
      if (mode == SImode)
	return GEN_INT (l[0]);
      else if (mode == HImode && GET_MODE (x) == SFmode)
	return gen_int_mode (l[0], HImode);
      else
	abort ();
    }

  if (mode == QImode && D_REG_P (x))
    return gen_rtx (REG, mode, HARD_B_REGNUM);

  /* gen_lowpart crashes when it is called with a SUBREG.  */
  if (GET_CODE (x) == SUBREG && SUBREG_BYTE (x) != 0)
    {
      if (mode == SImode)
	return gen_rtx_SUBREG (mode, SUBREG_REG (x), SUBREG_BYTE (x) + 4);
      else if (mode == HImode)
	return gen_rtx_SUBREG (mode, SUBREG_REG (x), SUBREG_BYTE (x) + 2);
      else
	abort ();
    }
  x = gen_lowpart (mode, x);

  /* Return a different rtx to avoid to share it in several insns
     (when used by a split pattern).  Sharing addresses within
     a MEM breaks the Z register replacement (and reloading).  */
  if (GET_CODE (x) == MEM)
    x = copy_rtx (x);
  return x;
}

rtx
m68hc11_gen_highpart (mode, x)
     enum machine_mode mode;
     rtx x;
{
  /* We assume that the high part of an auto-inc mode is the same with
     the mode changed and that the caller split the larger mode in the
     correct order.  */
  if (GET_CODE (x) == MEM && m68hc11_auto_inc_p (XEXP (x, 0)))
    {
      return gen_rtx (MEM, mode, XEXP (x, 0));
    }

  /* Note that a CONST_DOUBLE rtx could represent either an integer or a
     floating-point constant.  A CONST_DOUBLE is used whenever the
     constant requires more than one word in order to be adequately
     represented.  */
  if (GET_CODE (x) == CONST_DOUBLE)
    {
      long l[2];

      if (GET_MODE_CLASS (GET_MODE (x)) == MODE_FLOAT)
	{
	  REAL_VALUE_TYPE r;

	  if (GET_MODE (x) == SFmode)
	    {
	      REAL_VALUE_FROM_CONST_DOUBLE (r, x);
	      REAL_VALUE_TO_TARGET_SINGLE (r, l[1]);
	    }
	  else
	    {
	      rtx first, second;

	      split_double (x, &first, &second);
	      return first;
	    }
	  if (mode == SImode)
	    return GEN_INT (l[1]);

	  return gen_int_mode ((l[1] >> 16), HImode);
	}
      else
	{
	  l[1] = CONST_DOUBLE_HIGH (x);
	}

      if (mode == SImode)
	return GEN_INT (l[1]);
      else if (mode == HImode && GET_MODE_CLASS (GET_MODE (x)) == MODE_FLOAT)
	return gen_int_mode ((l[0] >> 16), HImode);
      else
	abort ();
    }
  if (GET_CODE (x) == CONST_INT)
    {
      HOST_WIDE_INT val = INTVAL (x);

      if (mode == QImode)
	{
	  return gen_int_mode (val >> 8, QImode);
	}