reload.c

早期freebsd实现

      for (; i >= 0; i--)
	if (hard_reg_set_here_p (beg_regno, end_regno, XVECEXP (x, 0, i)))
	  return 1;
    }

  return 0;
}

/* Return 1 if ADDR is a valid memory address for mode MODE,
   and check that each pseudo reg has the proper kind of
   hard reg.  */

int
strict_memory_address_p (mode, addr)
     enum machine_mode mode;
     register rtx addr;
{
  GO_IF_LEGITIMATE_ADDRESS (mode, addr, win);
  return 0;

 win:
  return 1;
}


/* Like rtx_equal_p except that it allows a REG and a SUBREG to match
   if they are the same hard reg, and has special hacks for
   autoincrement and autodecrement.
   This is specifically intended for find_reloads to use
   in determining whether two operands match.
   X is the operand whose number is the lower of the two.

   The value is 2 if Y contains a pre-increment that matches
   a non-incrementing address in X.  */

/* ??? To be completely correct, we should arrange to pass
   for X the output operand and for Y the input operand.
   For now, we assume that the output operand has the lower number
   because that is natural in (SET output (... input ...)).  */

int
operands_match_p (x, y)
     register rtx x, y;
{
  register int i;
  register RTX_CODE code = GET_CODE (x);
  register char *fmt;
  int success_2;
      
  if (x == y)
    return 1;
  if ((code == REG || (code == SUBREG && GET_CODE (SUBREG_REG (x)) == REG))
      && (GET_CODE (y) == REG || (GET_CODE (y) == SUBREG
				  && GET_CODE (SUBREG_REG (y)) == REG)))
    {
      register int j;

      if (code == SUBREG)
	{
	  i = REGNO (SUBREG_REG (x));
	  if (i >= FIRST_PSEUDO_REGISTER)
	    goto slow;
	  i += SUBREG_WORD (x);
	}
      else
	i = REGNO (x);

      if (GET_CODE (y) == SUBREG)
	{
	  j = REGNO (SUBREG_REG (y));
	  if (j >= FIRST_PSEUDO_REGISTER)
	    goto slow;
	  j += SUBREG_WORD (y);
	}
      else
	j = REGNO (y);

      return i == j;
    }
  /* If two operands must match, because they are really a single
     operand of an assembler insn, then two postincrements are invalid
     because the assembler insn would increment only once.
     On the other hand, an postincrement matches ordinary indexing
     if the postincrement is the output operand.  */
  if (code == POST_DEC || code == POST_INC)
    return operands_match_p (XEXP (x, 0), y);
  /* Two preincrements are invalid
     because the assembler insn would increment only once.
     On the other hand, an preincrement matches ordinary indexing
     if the preincrement is the input operand.
     In this case, return 2, since some callers need to do special
     things when this happens.  */
  if (GET_CODE (y) == PRE_DEC || GET_CODE (y) == PRE_INC)
    return operands_match_p (x, XEXP (y, 0)) ? 2 : 0;

 slow:

  /* Now we have disposed of all the cases 
     in which different rtx codes can match.  */
  if (code != GET_CODE (y))
    return 0;
  if (code == LABEL_REF)
    return XEXP (x, 0) == XEXP (y, 0);
  if (code == SYMBOL_REF)
    return XSTR (x, 0) == XSTR (y, 0);

  /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.  */

  if (GET_MODE (x) != GET_MODE (y))
    return 0;

  /* Compare the elements.  If any pair of corresponding elements
     fail to match, return 0 for the whole things.  */

  success_2 = 0;
  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      int val;
      switch (fmt[i])
	{
	case 'w':
	  if (XWINT (x, i) != XWINT (y, i))
	    return 0;
	  break;

	case 'i':
	  if (XINT (x, i) != XINT (y, i))
	    return 0;
	  break;

	case 'e':
	  val = operands_match_p (XEXP (x, i), XEXP (y, i));
	  if (val == 0)
	    return 0;
	  /* If any subexpression returns 2,
	     we should return 2 if we are successful.  */
	  if (val == 2)
	    success_2 = 1;
	  break;

	case '0':
	  break;

	  /* It is believed that rtx's at this level will never
	     contain anything but integers and other rtx's,
	     except for within LABEL_REFs and SYMBOL_REFs.  */
	default:
	  abort ();
	}
    }
  return 1 + success_2;
}

/* Return the number of times character C occurs in string S.  */

int
n_occurrences (c, s)
     char c;
     char *s;
{
  int n = 0;
  while (*s)
    n += (*s++ == c);
  return n;
}

struct decomposition
{
  int reg_flag;
  int safe;
  rtx base;
  HOST_WIDE_INT start;
  HOST_WIDE_INT end;
};

/* Describe the range of registers or memory referenced by X.
   If X is a register, set REG_FLAG and put the first register 
   number into START and the last plus one into END.
   If X is a memory reference, put a base address into BASE 
   and a range of integer offsets into START and END.
   If X is pushing on the stack, we can assume it causes no trouble, 
   so we set the SAFE field.  */

static struct decomposition
decompose (x)
     rtx x;
{
  struct decomposition val;
  int all_const = 0;

  val.reg_flag = 0;
  val.safe = 0;
  if (GET_CODE (x) == MEM)
    {
      rtx base, offset = 0;
      rtx addr = XEXP (x, 0);

      if (GET_CODE (addr) == PRE_DEC || GET_CODE (addr) == PRE_INC
	  || GET_CODE (addr) == POST_DEC || GET_CODE (addr) == POST_INC)
	{
	  val.base = XEXP (addr, 0);
	  val.start = - GET_MODE_SIZE (GET_MODE (x));
	  val.end = GET_MODE_SIZE (GET_MODE (x));
	  val.safe = REGNO (val.base) == STACK_POINTER_REGNUM;
	  return val;
	}

      if (GET_CODE (addr) == CONST)
	{
	  addr = XEXP (addr, 0);
	  all_const = 1;
	}
      if (GET_CODE (addr) == PLUS)
	{
	  if (CONSTANT_P (XEXP (addr, 0)))
	    {
	      base = XEXP (addr, 1);
	      offset = XEXP (addr, 0);
	    }
	  else if (CONSTANT_P (XEXP (addr, 1)))
	    {
	      base = XEXP (addr, 0);
	      offset = XEXP (addr, 1);
	    }
	}

      if (offset == 0)
	{
	  base = addr;
	  offset = const0_rtx;
	} 
      if (GET_CODE (offset) == CONST)
	offset = XEXP (offset, 0);
      if (GET_CODE (offset) == PLUS)
	{
	  if (GET_CODE (XEXP (offset, 0)) == CONST_INT)
	    {
	      base = gen_rtx (PLUS, GET_MODE (base), base, XEXP (offset, 1));
	      offset = XEXP (offset, 0);
	    }
	  else if (GET_CODE (XEXP (offset, 1)) == CONST_INT)
	    {
	      base = gen_rtx (PLUS, GET_MODE (base), base, XEXP (offset, 0));
	      offset = XEXP (offset, 1);
	    }
	  else
	    {
	      base = gen_rtx (PLUS, GET_MODE (base), base, offset);
	      offset = const0_rtx;
	    }
	}
      else if (GET_CODE (offset) != CONST_INT)
	{
	  base = gen_rtx (PLUS, GET_MODE (base), base, offset);
	  offset = const0_rtx;
	}

      if (all_const && GET_CODE (base) == PLUS)
	base = gen_rtx (CONST, GET_MODE (base), base);

      if (GET_CODE (offset) != CONST_INT)
	abort ();

      val.start = INTVAL (offset);
      val.end = val.start + GET_MODE_SIZE (GET_MODE (x));
      val.base = base;
      return val;
    }
  else if (GET_CODE (x) == REG)
    {
      val.reg_flag = 1;
      val.start = true_regnum (x); 
      if (val.start < 0)
	{
	  /* A pseudo with no hard reg.  */
	  val.start = REGNO (x);
	  val.end = val.start + 1;
	}
      else
	/* A hard reg.  */
	val.end = val.start + HARD_REGNO_NREGS (val.start, GET_MODE (x));
    }
  else if (GET_CODE (x) == SUBREG)
    {
      if (GET_CODE (SUBREG_REG (x)) != REG)
	/* This could be more precise, but it's good enough.  */
	return decompose (SUBREG_REG (x));
      val.reg_flag = 1;
      val.start = true_regnum (x); 
      if (val.start < 0)
	return decompose (SUBREG_REG (x));
      else
	/* A hard reg.  */
	val.end = val.start + HARD_REGNO_NREGS (val.start, GET_MODE (x));
    }
  else if (CONSTANT_P (x)
	   /* This hasn't been assigned yet, so it can't conflict yet.  */
	   || GET_CODE (x) == SCRATCH)
    val.safe = 1;
  else
    abort ();
  return val;
}

/* Return 1 if altering Y will not modify the value of X.
   Y is also described by YDATA, which should be decompose (Y).  */

static int
immune_p (x, y, ydata)
     rtx x, y;
     struct decomposition ydata;
{
  struct decomposition xdata;

  if (ydata.reg_flag)
    return !refers_to_regno_for_reload_p (ydata.start, ydata.end, x, NULL_PTR);
  if (ydata.safe)
    return 1;

  if (GET_CODE (y) != MEM)
    abort ();
  /* If Y is memory and X is not, Y can't affect X.  */
  if (GET_CODE (x) != MEM)
    return 1;

  xdata =  decompose (x);

  if (! rtx_equal_p (xdata.base, ydata.base))
    {
      /* If bases are distinct symbolic constants, there is no overlap.  */
      if (CONSTANT_P (xdata.base) && CONSTANT_P (ydata.base))
	return 1;
      /* Constants and stack slots never overlap.  */
      if (CONSTANT_P (xdata.base)
	  && (ydata.base == frame_pointer_rtx
	      || ydata.base == stack_pointer_rtx))
	return 1;
      if (CONSTANT_P (ydata.base)
	  && (xdata.base == frame_pointer_rtx
	      || xdata.base == stack_pointer_rtx))
	return 1;
      /* If either base is variable, we don't know anything.  */
      return 0;
    }


  return (xdata.start >= ydata.end || ydata.start >= xdata.end);
}

/* Similar, but calls decompose.  */

int
safe_from_earlyclobber (op, clobber)
     rtx op, clobber;
{
  struct decomposition early_data;

  early_data = decompose (clobber);
  return immune_p (op, clobber, early_data);
}

/* Main entry point of this file: search the body of INSN
   for values that need reloading and record them with push_reload.
   REPLACE nonzero means record also where the values occur
   so that subst_reloads can be used.

   IND_LEVELS says how many levels of indirection are supported by this
   machine; a value of zero means that a memory reference is not a valid
   memory address.

   LIVE_KNOWN says we have valid information about which hard
   regs are live at each point in the program; this is true when
   we are called from global_alloc but false when stupid register
   allocation has been done.

   RELOAD_REG_P if nonzero is a