stormy16.c

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   If a scratch register is required (either with or without an intermediate
   register), you should define patterns for `reload_inM' or `reload_outM', as
   required..  These patterns, which will normally be implemented with a
   `define_expand', should be similar to the `movM' patterns, except that
   operand 2 is the scratch register.

   Define constraints for the reload register and scratch register that contain
   a single register class.  If the original reload register (whose class is
   CLASS) can meet the constraint given in the pattern, the value returned by
   these macros is used for the class of the scratch register.  Otherwise, two
   additional reload registers are required.  Their classes are obtained from
   the constraints in the insn pattern.

   X might be a pseudo-register or a `subreg' of a pseudo-register, which could
   either be in a hard register or in memory.  Use `true_regnum' to find out;
   it will return -1 if the pseudo is in memory and the hard register number if
   it is in a register.

   These macros should not be used in the case where a particular class of
   registers can only be copied to memory and not to another class of
   registers.  In that case, secondary reload registers are not needed and
   would not be helpful.  Instead, a stack location must be used to perform the
   copy and the `movM' pattern should use memory as an intermediate storage.
   This case often occurs between floating-point and general registers.  */

enum reg_class
xstormy16_secondary_reload_class (class, mode, x)
     enum reg_class class;
     enum machine_mode mode;
     rtx x;
{
  /* This chip has the interesting property that only the first eight
     registers can be moved to/from memory.  */
  if ((GET_CODE (x) == MEM
       || ((GET_CODE (x) == SUBREG || GET_CODE (x) == REG)
	   && (true_regnum (x) == -1
	       || true_regnum (x) >= FIRST_PSEUDO_REGISTER)))
      && ! reg_class_subset_p (class, EIGHT_REGS))
    return EIGHT_REGS;

  /* When reloading a PLUS, the carry register will be required
     unless the inc or dec instructions can be used.  */
  if (xstormy16_carry_plus_operand (x, mode))
    return CARRY_REGS;

  return NO_REGS;
}

/* Recognize a PLUS that needs the carry register.  */
int
xstormy16_carry_plus_operand (x, mode)
     rtx x;
     enum machine_mode mode ATTRIBUTE_UNUSED;
{
  return (GET_CODE (x) == PLUS
	  && GET_CODE (XEXP (x, 1)) == CONST_INT
	  && (INTVAL (XEXP (x, 1)) < -4 || INTVAL (XEXP (x, 1)) > 4));
}


enum reg_class
xstormy16_preferred_reload_class (x, class)
     enum reg_class class;
     rtx x;
{
  if (class == GENERAL_REGS
      && GET_CODE (x) == MEM)
    return EIGHT_REGS;

  return class;
}

#define LEGITIMATE_ADDRESS_INTEGER_P(X, OFFSET)				\
 (GET_CODE (X) == CONST_INT						\
  && (unsigned HOST_WIDE_INT) (INTVAL (X) + (OFFSET) + 2048) < 4096)

#define LEGITIMATE_ADDRESS_CONST_INT_P(X, OFFSET)			 \
 (GET_CODE (X) == CONST_INT						 \
  && INTVAL (X) + (OFFSET) >= 0						 \
  && INTVAL (X) + (OFFSET) < 0x8000					 \
  && (INTVAL (X) + (OFFSET) < 0x100 || INTVAL (X) + (OFFSET) >= 0x7F00))

int
xstormy16_legitimate_address_p (mode, x, strict)
     enum machine_mode mode ATTRIBUTE_UNUSED;
     rtx x;
     int strict;
{
  if (LEGITIMATE_ADDRESS_CONST_INT_P (x, 0))
    return 1;

  if (GET_CODE (x) == PLUS
      && LEGITIMATE_ADDRESS_INTEGER_P (XEXP (x, 1), 0))
    x = XEXP (x, 0);
  
  if (GET_CODE (x) == POST_INC
      || GET_CODE (x) == PRE_DEC)
    x = XEXP (x, 0);
  
  if (GET_CODE (x) == REG && REGNO_OK_FOR_BASE_P (REGNO (x))
      && (! strict || REGNO (x) < FIRST_PSEUDO_REGISTER))
    return 1;
  
  return 0;
}

/* Return nonzero if memory address X (an RTX) can have different
   meanings depending on the machine mode of the memory reference it
   is used for or if the address is valid for some modes but not
   others.

   Autoincrement and autodecrement addresses typically have mode-dependent
   effects because the amount of the increment or decrement is the size of the
   operand being addressed.  Some machines have other mode-dependent addresses.
   Many RISC machines have no mode-dependent addresses.

   You may assume that ADDR is a valid address for the machine.  
   
   On this chip, this is true if the address is valid with an offset
   of 0 but not of 6, because in that case it cannot be used as an
   address for DImode or DFmode, or if the address is a post-increment
   or pre-decrement address.  */
int
xstormy16_mode_dependent_address_p (x)
     rtx x;
{
  if (LEGITIMATE_ADDRESS_CONST_INT_P (x, 0)
      && ! LEGITIMATE_ADDRESS_CONST_INT_P (x, 6))
    return 1;
  
  if (GET_CODE (x) == PLUS
      && LEGITIMATE_ADDRESS_INTEGER_P (XEXP (x, 1), 0)
      && ! LEGITIMATE_ADDRESS_INTEGER_P (XEXP (x, 1), 6))
    return 1;

  if (GET_CODE (x) == PLUS)
    x = XEXP (x, 0);

  if (GET_CODE (x) == POST_INC
      || GET_CODE (x) == PRE_DEC)
    return 1;

  return 0;
}

/* A C expression that defines the optional machine-dependent constraint
   letters (`Q', `R', `S', `T', `U') that can be used to segregate specific
   types of operands, usually memory references, for the target machine.
   Normally this macro will not be defined.  If it is required for a particular
   target machine, it should return 1 if VALUE corresponds to the operand type
   represented by the constraint letter C.  If C is not defined as an extra
   constraint, the value returned should be 0 regardless of VALUE.  */
int
xstormy16_extra_constraint_p (x, c)
     rtx x;
     int c;
{
  switch (c)
    {
      /* 'Q' is for pushes.  */
    case 'Q':
      return (GET_CODE (x) == MEM
	      && GET_CODE (XEXP (x, 0)) == POST_INC
	      && XEXP (XEXP (x, 0), 0) == stack_pointer_rtx);

      /* 'R' is for pops.  */
    case 'R':
      return (GET_CODE (x) == MEM
	      && GET_CODE (XEXP (x, 0)) == PRE_DEC
	      && XEXP (XEXP (x, 0), 0) == stack_pointer_rtx);

      /* 'S' is for immediate memory addresses.  */
    case 'S':
      return (GET_CODE (x) == MEM
	      && GET_CODE (XEXP (x, 0)) == CONST_INT
	      && xstormy16_legitimate_address_p (VOIDmode, XEXP (x, 0), 0));

      /* 'T' is for Rx.  */
    case 'T':
      /* Not implemented yet.  */
      return 0;

      /* 'U' is for CONST_INT values not between 2 and 15 inclusive,
	 for allocating a scratch register for 32-bit shifts.  */
    case 'U':
      return (GET_CODE (x) == CONST_INT
	      && (INTVAL (x) < 2 || INTVAL (x) > 15));

    default:
      return 0;
    }
}

int
short_memory_operand (x, mode)
     rtx x;
     enum machine_mode mode;
{
  if (! memory_operand (x, mode))
    return 0;
  return (GET_CODE (XEXP (x, 0)) != PLUS);
}

int
nonimmediate_nonstack_operand (op, mode)
     rtx op;
     enum machine_mode mode;
{
  /* 'Q' is for pushes, 'R' for pops.  */
  return (nonimmediate_operand (op, mode) 
	  && ! xstormy16_extra_constraint_p (op, 'Q')
	  && ! xstormy16_extra_constraint_p (op, 'R'));
}

/* Splitter for the 'move' patterns, for modes not directly implemeted
   by hardware.  Emit insns to copy a value of mode MODE from SRC to
   DEST.

   This function is only called when reload_completed.
   */

void 
xstormy16_split_move (mode, dest, src)
     enum machine_mode mode;
     rtx dest;
     rtx src;
{
  int num_words = GET_MODE_BITSIZE (mode) / BITS_PER_WORD;
  int direction, end, i;
  int src_modifies = 0;
  int dest_modifies = 0;
  int src_volatile = 0;
  int dest_volatile = 0;
  rtx mem_operand;
  rtx auto_inc_reg_rtx = NULL_RTX;
  
  /* Check initial conditions.  */
  if (! reload_completed
      || mode == QImode || mode == HImode
      || ! nonimmediate_operand (dest, mode)
      || ! general_operand (src, mode))
    abort ();

  /* This case is not supported below, and shouldn't be generated.  */
  if (GET_CODE (dest) == MEM
      && GET_CODE (src) == MEM)
    abort ();

  /* This case is very very bad after reload, so trap it now.  */
  if (GET_CODE (dest) == SUBREG
      || GET_CODE (src) == SUBREG)
    abort ();

  /* The general idea is to copy by words, offsetting the source and
     destination.  Normally the least-significant word will be copied
     first, but for pre-dec operations it's better to copy the 
     most-significant word first.  Only one operand can be a pre-dec
     or post-inc operand.  

     It's also possible that the copy overlaps so that the direction
     must be reversed.  */
  direction = 1;
  
  if (GET_CODE (dest) == MEM)
    {
      mem_operand = XEXP (dest, 0);
      dest_modifies = side_effects_p (mem_operand);
      if (auto_inc_p (mem_operand))
        auto_inc_reg_rtx = XEXP (mem_operand, 0);
      dest_volatile = MEM_VOLATILE_P (dest);
      if (dest_volatile)
	{
	  dest = copy_rtx (dest);
	  MEM_VOLATILE_P (dest) = 0;
	}
    }
  else if (GET_CODE (src) == MEM)
    {
      mem_operand = XEXP (src, 0);
      src_modifies = side_effects_p (mem_operand);
      if (auto_inc_p (mem_operand))
        auto_inc_reg_rtx = XEXP (mem_operand, 0);
      src_volatile = MEM_VOLATILE_P (src);
      if (src_volatile)
	{
	  src = copy_rtx (src);
	  MEM_VOLATILE_P (src) = 0;
	}
    }
  else
    mem_operand = NULL_RTX;

  if (mem_operand == NULL_RTX)
    {
      if (GET_CODE (src) == REG
	  && GET_CODE (dest) == REG
	  && reg_overlap_mentioned_p (dest, src)
	  && REGNO (dest) > REGNO (src))
	direction = -1;
    }
  else if (GET_CODE (mem_operand) == PRE_DEC
      || (GET_CODE (mem_operand) == PLUS 
	  && GET_CODE (XEXP (mem_operand, 0)) == PRE_DEC))
    direction = -1;
  else if (GET_CODE (src) == MEM
	   && reg_overlap_mentioned_p (dest, src))
    {
      int regno;
      if (GET_CODE (dest) != REG)
	abort ();
      regno = REGNO (dest);
      
      if (! refers_to_regno_p (regno, regno + num_words, mem_operand, 0))
	abort ();
      
      if (refers_to_regno_p (regno, regno + 1, mem_operand, 0))
	direction = -1;
      else if (refers_to_regno_p (regno + num_words - 1, regno + num_words,
				  mem_operand, 0))
	direction = 1;
      else
	/* This means something like
	   (set (reg:DI r0) (mem:DI (reg:HI r1)))
	   which we'd need to support by doing the set of the second word
	   last.  */
	abort ();
    }

  end = direction < 0 ? -1 : num_words;
  for (i = direction < 0 ? num_words - 1 : 0; i != end; i += direction)
    {
      rtx w_src, w_dest, insn;

      if (src_modifies)
	w_src = gen_rtx_MEM (word_mode, mem_operand);
      else
	w_src = simplify_gen_subreg (word_mode, src, mode, i * UNITS_PER_WORD);
      if (src_volatile)
	MEM_VOLATILE_P (w_src) = 1;
      if (dest_modifies)
	w_dest = gen_rtx_MEM (word_mode, mem_operand);
      else
	w_dest = simplify_gen_subreg (word_mode, dest, mode, 
				      i * UNITS_PER_WORD);
      if (dest_volatile)
	MEM_VOLATILE_P (w_dest) = 1;
      
      /* The simplify_subreg calls must always be able to simplify.  */
      if (GET_CODE (w_src) == SUBREG
	  || GET_CODE (w_dest) == SUBREG)
	abort ();
      
      insn = emit_insn (gen_rtx_SET (VOIDmode, w_dest, w_src));
      if (auto_inc_reg_rtx)
        REG_NOTES (insn) = alloc_EXPR_LIST (REG_INC,
                                            auto_inc_reg_rtx,
					    REG_NOTES (insn));
    }
}

/* Expander for the 'move' patterns.  Emit insns to copy a value of
   mode MODE from SRC to DEST.  */

void 
xstormy16_expand_move (mode, dest, src)
     enum machine_mode mode;
     rtx dest;
     rtx src;
{
  /* There are only limited immediate-to-memory move instructions.  */
  if (! reload_in_progress
      && ! reload_completed
      && GET_CODE (dest) == MEM
      && (GET_CODE (XEXP (dest, 0)) != CONST_INT
	  || ! xstormy16_legitimate_address_p (mode, XEXP (dest, 0), 0))
      && GET_CODE (src) != REG
      && GET_CODE (src) != SUBREG)
    src = copy_to_mode_reg (mode, src);

  /* Don't emit something we would immediately split.  */
  if (reload_completed
      && mode != HImode && mode != QImode)
    {
      xstormy16_split_move (mode, dest, src);
      return;
    }
  
  emit_insn (gen_rtx_SET (VOIDmode, dest, src));
}


/* Stack Layout:

   The stack is laid out as follows:

SP->
FP->	Local variables
	Register save area (up to 4 words)
	Argument register save area for stdarg (NUM_ARGUMENT_REGISTERS words)

AP->	Return address (two words)
	9th procedure parameter word
	10th procedure parameter word
	...
	last procedure parameter word

  The frame pointer location is tuned to make it most likely that all
  parameters and local variables can be accessed using a load-indexed
  instruction.  */

/* A structure to describe the layout.  */
struct xstormy16_stack_layout
{
  /* Size of the topmost three items on the stack.  */
  int locals_size;
  int register_save_size;
  int stdarg_save_size;
  /* Sum of the above items.  */
  int frame_size;
  /* Various offsets.  */
  int first_local_minus_ap;
  int sp_minus_fp;
  int fp_minus_ap;
};

/* Does REGNO need to be saved?  */
#define REG_NEEDS_SAVE(REGNUM, IFUN)					\
  ((regs_ever_live[REGNUM] && ! call_used_regs[REGNUM])			\
   || (IFUN && ! fixed_regs[REGNUM] && call_used_regs[REGNUM]		\
       && (regs_ever_live[REGNUM] || ! current_function_is_leaf)))

/* Compute the stack layout.  */
struct xstormy16_stack_layout