combine.c

这是完整的gcc源代码

	 now supposed to appear.  */
      if (((was_replaced[0] && GET_CODE (XEXP (x, 1)) == PLUS)
	   || (was_replaced[1] && GET_CODE (XEXP (x, 0)) == PLUS))
	  ||
	  ((was_replaced[0] || was_replaced[1])
	   && GET_CODE (to) == PLUS))
	{
	  rtx offset = 0, base, index;
	  if (GET_CODE (to) != PLUS)
	    {
	      index = to;
	      base = was_replaced[0] ? XEXP (x, 1) : XEXP (x, 0);
	    }
	  else
	    {
	      index = was_replaced[0] ? XEXP (x, 1) : XEXP (x, 0);
	      base = to;
	    }
	  if (CONSTANT_ADDRESS_P (XEXP (base, 0)))
	    {
	      offset = XEXP (base, 0);
	      base = XEXP (base, 1);
	    }
	  else if (CONSTANT_ADDRESS_P (XEXP (base, 1)))
	    {
	      offset = XEXP (base, 1);
	      base = XEXP (base, 0);
	    }
	  if (offset != 0)
	    {
	      if (!undobuf.storage)
		undobuf.storage = (char *) oballoc (0);
	      if (GET_CODE (offset) == CONST_INT)
		return plus_constant (gen_rtx (PLUS, GET_MODE (index),
					       base, index),
				      INTVAL (offset));
	      if (GET_CODE (index) == CONST_INT)
		return plus_constant (gen_rtx (PLUS, GET_MODE (offset),
					       base, offset),
				      INTVAL (index));
	      return gen_rtx (PLUS, GET_MODE (index),
			      gen_rtx (PLUS, GET_MODE (index),
				       base, index),
			      offset);
	    }
	}
      break;

    case EQ:
    case NE:
      /* If comparing a subreg against zero, discard the subreg.  */
      if (was_replaced[0]
	  && GET_CODE (to) == SUBREG
	  && SUBREG_WORD (to) == 0
	  && XEXP (x, 1) == const0_rtx)
	SUBST (XEXP (x, 0), SUBREG_REG (to));

      /* If comparing a ZERO_EXTRACT against zero,
	 canonicalize to a SIGN_EXTRACT,
	 since the two are equivalent here.  */
      if (was_replaced[0]
	  && GET_CODE (to) == ZERO_EXTRACT
	  && XEXP (x, 1) == const0_rtx)
	{
	  if (!undobuf.storage)
	    undobuf.storage = (char *) oballoc (0);
	  SUBST (XEXP (x, 0),
		 gen_rtx (SIGN_EXTRACT, GET_MODE (to),
			  XEXP (to, 0), XEXP (to, 1),
			  XEXP (to, 2)));
	}
#ifndef BITS_BIG_ENDIAN
      /* If we are putting (ASHIFT 1 x) into (EQ (AND ... y) 0),
	 arrange to return (EQ (SIGN_EXTRACT y 1 x) 0),
	 which is what jump-on-bit instructions are written with.  */
      else if (XEXP (x, 1) == const0_rtx
	       && GET_CODE (XEXP (x, 0)) == AND
	       && (XEXP (XEXP (x, 0), 0) == to
		   || XEXP (XEXP (x, 0), 1) == to)
	       && GET_CODE (to) == ASHIFT
	       && XEXP (to, 0) == const1_rtx)
	{
	  register rtx y = XEXP (XEXP (x, 0),
				 XEXP (XEXP (x, 0), 0) == to);
	  if (!undobuf.storage)
	    undobuf.storage = (char *) oballoc (0);
	  SUBST (XEXP (x, 0),
		 gen_rtx (SIGN_EXTRACT, GET_MODE (to),
			  y,
			  const1_rtx, XEXP (to, 1)));
	}
#endif /* not BITS_BIG_ENDIAN */
      /* Negation is a no-op before equality test against zero.  */
      if (GET_CODE (XEXP (x, 0)) == NEG && XEXP (x, 1) == const0_rtx)
	{
	  SUBST (XEXP (x, 0), XEXP (XEXP (x, 0), 0));
	}
      if (GET_CODE (XEXP (x, 1)) == NEG && XEXP (x, 0) == const0_rtx)
	{
	  SUBST (XEXP (x, 1), XEXP (XEXP (x, 1), 0));
	}
      break;

    case ZERO_EXTEND:
      /* Nested zero-extends are equivalent to just one.  */
      if (was_replaced[0]
	  && GET_CODE (to) == ZERO_EXTEND)
	SUBST (XEXP (x, 0), XEXP (to, 0));
      /* Zero extending a constant int can be replaced
	 by a zero-extended constant.  */
      if (was_replaced[0]
	  && HOST_BITS_PER_INT >= GET_MODE_BITSIZE (GET_MODE (from))
	  && GET_CODE (to) == CONST_INT)
	{
	  int intval = INTVAL (to) & GET_MODE_MASK (GET_MODE (from));
	  if (!undobuf.storage)
	    undobuf.storage = (char *) oballoc (0);
	  return gen_rtx (CONST_INT, VOIDmode, intval);
	}
      /* Zero-extending the result of an and with a constant can be done
	 with a wider and.  */
      if (was_replaced[0]
	  && GET_CODE (to) == AND
	  && GET_CODE (XEXP (to, 1)) == CONST_INT
	  && FAKE_EXTEND_SAFE_P (GET_MODE (x), XEXP (to, 0))
	  /* Avoid getting wrong result if the constant has high bits set
	     that are irrelevant in the narrow mode where it is being used.  */
	  && 0 == (INTVAL (XEXP (to, 1))
		   & ~ GET_MODE_MASK (GET_MODE (to))))
	{
	  if (!undobuf.storage)
	    undobuf.storage = (char *) oballoc (0);
	  return gen_rtx (AND, GET_MODE (x),
			  gen_lowpart_for_combine (GET_MODE (x), XEXP (to, 0)),
			  XEXP (to, 1));
	} 
      /* Change (zero_extend:M (subreg:N (zero_extract:M ...) 0))
	 to (zero_extract:M ...) if the field extracted fits in mode N.  */
      if (GET_CODE (XEXP (x, 0)) == SUBREG
	  && GET_CODE (XEXP (XEXP (x, 0), 0)) == ZERO_EXTRACT
	  && GET_CODE (XEXP (XEXP (XEXP (x, 0), 0), 1)) == CONST_INT
	  && (INTVAL (XEXP (XEXP (XEXP (x, 0), 0), 1))
	      <= GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0)))))
	{
	  return XEXP (XEXP (x, 0), 0);
	}
      /* Change (zero_extend:M (subreg:N (and:M ... <const>) 0))
	 to (and:M ...) if the significant bits fit in mode N.  */
      if (GET_CODE (XEXP (x, 0)) == SUBREG
	  && SUBREG_REG (XEXP (x, 0)) == to
	  && SUBREG_WORD (XEXP (x, 0)) == 0
	  && GET_CODE (to) == AND
	  && GET_CODE (XEXP (to, 1)) == CONST_INT
	  && FAKE_EXTEND_SAFE_P (GET_MODE (x), XEXP (to, 0))
	  /* Avoid getting wrong result if the constant has high bits set
	     that are irrelevant in the narrow mode where it is being used.  */
	  && 0 == (INTVAL (XEXP (to, 1))
		   & ~ GET_MODE_MASK (GET_MODE (to))))
	{
	  if (!undobuf.storage)
	    undobuf.storage = (char *) oballoc (0);
	  return gen_rtx (AND, GET_MODE (x),
			  gen_lowpart_for_combine (GET_MODE (x), XEXP (to, 0)),
			  XEXP (to, 1));
	}
      /* In (zero_extend:M (subreg:N (lshiftrt:M REG))),
	 where REG was assigned from (zero_extend:M (any:N ...)),
	 remove the outer zero extension.  */
      if (GET_CODE (XEXP (x, 0)) == SUBREG
	  && SUBREG_REG (XEXP (x, 0)) == to
	  && SUBREG_WORD (XEXP (x, 0)) == 0
	  && GET_CODE (to) == LSHIFTRT)
	{
	  rtx tmp = XEXP (to, 0);

	  /* See if arg of LSHIFTRT is a register whose value we can find.  */
	  if (GET_CODE (tmp) == REG)
	    if (reg_n_sets[REGNO (tmp)] == 1
		&& reg_last_set[REGNO (tmp)] != 0
		&& SET_DEST (PATTERN (reg_last_set[REGNO (tmp)])) == tmp)
	      tmp = SET_SRC (PATTERN (reg_last_set[REGNO (tmp)]));
	    else
	      break;

	  if (GET_CODE (tmp) == ZERO_EXTEND
	      && GET_MODE (tmp) == GET_MODE (x)
	      && GET_MODE (XEXP (tmp, 0)) == GET_MODE (XEXP (x, 0)))
	    return SUBREG_REG (XEXP (x, 0));
	}
      break;

    case SIGN_EXTEND:
      /* Nested sign-extends are equivalent to just one.  */
      if (was_replaced[0]
	  && GET_CODE (to) == SIGN_EXTEND)
	SUBST (XEXP (x, 0), XEXP (to, 0));
      /* Sign extending a constant int can be replaced
	 by a sign-extended constant.  */
      if (was_replaced[0]
	  && HOST_BITS_PER_INT >= GET_MODE_BITSIZE (GET_MODE (from))
	  && GET_CODE (to) == CONST_INT)
	{
	  int intval = INTVAL (to);
	  if (!undobuf.storage)
	    undobuf.storage = (char *) oballoc (0);
	  if (intval > 0
	      && (intval & (1 << (GET_MODE_BITSIZE (GET_MODE (from)) - 1))))
	    intval |= ~ GET_MODE_MASK (GET_MODE (from));
	  return gen_rtx (CONST_INT, VOIDmode, intval);
	}
      /* Sign-extending the result of an and with a constant can be done
	 with a wider and, provided the high bit of the constant is 0.  */
      if (was_replaced[0]
	  && GET_CODE (to) == AND
	  && GET_CODE (XEXP (to, 1)) == CONST_INT
	  && FAKE_EXTEND_SAFE_P (GET_MODE (x), XEXP (to, 0))
	  && ((INTVAL (XEXP (to, 1))
	       & (-1 << (GET_MODE_BITSIZE (GET_MODE (to)) - 1)))
	      == 0))
	{
	  if (!undobuf.storage)
	    undobuf.storage = (char *) oballoc (0);
	  return gen_rtx (AND, GET_MODE (x),
			  gen_lowpart_for_combine (GET_MODE (x), XEXP (to, 0)),
			  XEXP (to, 1));
	 } 
      /* hacks added by tiemann.  */
      /* Change (sign_extend:M (subreg:N (and:M ... <const>) 0))
	 to (and:M ...), provided the result fits in mode N,
	 and the high bit of the constant is 0 in mode N.  */
      if (GET_CODE (XEXP (x, 0)) == SUBREG
	  && SUBREG_REG (XEXP (x, 0)) == to
	  && SUBREG_WORD (XEXP (x, 0)) == 0
	  && GET_CODE (to) == AND
	  && GET_CODE (XEXP (to, 1)) == CONST_INT
	  && FAKE_EXTEND_SAFE_P (GET_MODE (x), XEXP (to, 0))
	  && ((INTVAL (XEXP (to, 1))
	       & (-1 << (GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0))) - 1)))
	      == 0))
	{
	  if (!undobuf.storage)
	    undobuf.storage = (char *) oballoc (0);
	  return gen_rtx (AND, GET_MODE (x),
			  gen_lowpart_for_combine (GET_MODE (x), XEXP (to, 0)),
			  XEXP (to, 1));
	} 
      /* In (sign_extend:M (subreg:N (ashiftrt:M REG))),
	 where REG was assigned from (sign_extend:M (any:N ...)),
	 remove the outer sign extension.  */
      if (GET_CODE (XEXP (x, 0)) == SUBREG
	  && SUBREG_REG (XEXP (x, 0)) == to
	  && SUBREG_WORD (XEXP (x, 0)) == 0
	  && GET_CODE (to) == ASHIFTRT)
	{
	  rtx tmp = XEXP (to, 0);

	  /* See if arg of LSHIFTRT is a register whose value we can find.  */
	  if (GET_CODE (tmp) == REG)
	    if (reg_n_sets[REGNO (tmp)] == 1
		&& reg_last_set[REGNO (tmp)] != 0
		&& SET_DEST (PATTERN (reg_last_set[REGNO (tmp)])) == tmp)
	      tmp = SET_SRC (PATTERN (reg_last_set[REGNO (tmp)]));
	    else
	      break;

	  if (GET_CODE (tmp) == SIGN_EXTEND
	      && GET_MODE (tmp) == GET_MODE (x)
	      && GET_MODE (XEXP (tmp, 0)) == GET_MODE (XEXP (x, 0)))
	    return SUBREG_REG (XEXP (x, 0));
	}
      break;

    case SET:
      /* In (set (zero-extract <x> <n> <y>) (and <foo> <(2**n-1) | anything>))
	 the `and' can be deleted.  This can happen when storing a bit
	 that came from a set-flag insn followed by masking to one bit.  */
      if (GET_CODE (XEXP (x, 0)) == ZERO_EXTRACT
	  && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
	  && was_replaced[1]
	  && GET_CODE (to) == AND
	  && GET_CODE (XEXP (to, 1)) == CONST_INT
	  && 0 == (((1 << INTVAL (XEXP (XEXP (x, 0), 1))) - 1)
		   & ~ INTVAL (XEXP (to, 1))))
	{
	  SUBST (XEXP (x, 1), XEXP (to, 0));
	} 
      /* In (set (zero-extract <x> <n> <y>)
		 (subreg (and <foo> <(2**n-1) | anything>)))
	 the `and' can be deleted.  */
      if (GET_CODE (XEXP (x, 0)) == ZERO_EXTRACT
	  && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
	  && GET_CODE (XEXP (x, 1)) == SUBREG
	  && SUBREG_WORD (XEXP (x, 1)) == 0
	  && GET_CODE (SUBREG_REG (XEXP (x, 1))) == AND
	  && GET_CODE (XEXP (SUBREG_REG (XEXP (x, 1)), 1)) == CONST_INT
	  && 0 == (((1 << INTVAL (XEXP (XEXP (x, 0), 1))) - 1)
		   & ~ INTVAL (XEXP (SUBREG_REG (XEXP (x, 1)), 1))))
	{
	  SUBST (SUBREG_REG (XEXP (x, 1)), XEXP (SUBREG_REG (XEXP (x, 1)), 0));
	} 
      /* (set (zero_extract ...) (and/or/xor (zero_extract ...) const)),
	 if both zero_extracts have the same location, size and position,
	 can be changed to avoid the byte extracts.  */
      if ((GET_CODE (XEXP (x, 0)) == ZERO_EXTRACT
	   || GET_CODE (XEXP (x, 0)) == SIGN_EXTRACT)
	  && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
	  && (GET_CODE (XEXP (x, 1)) == AND
	      || GET_CODE (XEXP (x, 1)) == IOR
	      || GET_CODE (XEXP (x, 1)) == XOR)
	  && rtx_equal_p (XEXP (x, 0), XEXP (XEXP (x, 1), 0))
	  && GET_CODE (XEXP (XEXP (x, 1), 0)) == GET_CODE (XEXP (x, 0))
	  && GET_CODE (XEXP (XEXP (x, 1), 1)) == CONST_INT
	  /* zero_extract can apply to a QImode even if the bits extracted
	     don't fit inside that byte.  In such a case, we may not do this
	     optimization, since the OR or AND insn really would need
	     to fit in a byte.  */
	  && (INTVAL (XEXP (XEXP (x, 0), 1)) + INTVAL (XEXP (XEXP (x, 0), 2))
	      < GET_MODE_BITSIZE (GET_MODE (XEXP (XEXP (x, 0), 0)))))
	{
	  int shiftcount;
	  int fieldsize;
	  int newmask;
#ifdef BITS_BIG_ENDIAN
	  shiftcount
	    = GET_MODE_BITSIZE (GET_MODE (XEXP (XEXP (x, 0), 0)))
	      - INTVAL (XEXP (XEXP (x, 0), 1)) - INTVAL (XEXP (XEXP (x, 0), 2));
#else
	  shiftcount
	    = INTVAL (XEXP (XEXP (x, 0), 2));
#endif
	  fieldsize = INTVAL (XEXP (XEXP (x, 0), 1));
	  newmask = ((INTVAL (XEXP (XEXP (x, 1), 1)) << shiftcount)
		     + (GET_CODE (XEXP (x, 1)) == AND
			/* For AND, preserve the bits outside this field.  */
			? ((1 << shiftcount) - 1
			   + (-1 << (shiftcount + fieldsize)))
			: 0));
	  if (GET_MODE_BITSIZE (GET_MODE (XEXP (XEXP (x, 0), 0)))
	      < HOST_BITS_PER_INT)
	    newmask &= (1 << GET_MODE_BITSIZE (GET_MODE (XEXP (XEXP (x, 0), 0)))) - 1;
	  if (!undobuf.storage)
	    undobuf.storage = (char *) oballoc (0);
	  return
	    gen_rtx (SET, VOIDmode,
		     XEXP (XEXP (x, 0), 0),
		     gen_rtx (GET_CODE (XEXP (x, 1)),
			      GET_MODE (XEXP (XEXP (x, 0), 0)),
			      XEXP (XEXP (XEXP (x, 1), 0), 0),
			      gen_rtx (CONST_INT, VOIDmode, newmask)));
	}
      /* Can simplify (set (cc0) (compare (zero/sign_extend FOO) CONST))
	 to (set (cc0) (compare FOO CONST)) if CONST fits in FOO's mode
	 and we are only testing equality.
	 In fact, this is valid for zero_extend if what follows is an
	 unsigned comparison, and for sign_extend with a signed comparison.  */
      if (SET_DEST (x) == cc0_rtx
	  && GET_CODE (SET_SRC (x)) == COMPARE
	  && (GET_CODE (XEXP (SET_SRC (x), 0)) == ZERO_EXTEND
	      || GET_CODE (XEXP (SET_SRC (x), 0)) == SIGN_EXTEND)
	  && next_insn_tests_no_inequality (subst_insn)
	  && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
	  /* This is overly cautious by one bit, but saves worrying about
	     whether it is zero-extension or sign extension.  */
	  && ((unsigned) INTVAL (XEXP (SET_SRC (x), 1))
	      < (1 << (GET_MODE_BITSIZE (GET_MODE (XEXP (XEXP (SET_SRC (x), 0), 0))) - 1))))
	SUBST (XEXP (SET_SRC (x), 0), XEXP (XEXP (SET_SRC (x), 0), 0));
      break;

    case AND:
      if (GET_CODE (XEXP (x, 1)) == CONST_INT)
	{
	  rtx tem = simplify_and_const_int (x, to);
	  if (tem)
	    return tem;
	}
      break;

    case IOR:
    case XOR:
      /* (ior (ior x c1) c2) => (ior x c1|c2); likewise for xor.  */
      if (GET_CODE (XEXP (x, 1)) == CONST_INT
	  && GET_CODE (XEXP (x, 0)) == code