BImode arithmetic simplifications

[Richard Henderson <rth at cygnus dot com>]

Combine already knew that

	(not (and (ne x 0) (ne y 0)))

simplifies to

	(ior (not (ne x 0)) (not (ne y 0)))

This allows it to continue so that we get

	(ior (eq x 0) (eq y 0))


r~


        * combine.c (combine_simplify_rtx): Use gen_unary to distribute
        the NOT for De Morgan's rule.
        * simplify-rtx.c (simplify_unary_operation): Simplify a BImode NOT
        of a comparison to the reverse comparison.

Index: combine.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/combine.c,v
retrieving revision 1.152
diff -c -p -d -r1.152 combine.c
*** combine.c	2000/09/18 18:08:19	1.152
--- combine.c	2000/09/18 18:22:15
*************** combine_simplify_rtx (x, op0_mode, last,
*** 3933,3953 ****
        if (GET_CODE (XEXP (x, 0)) == IOR || GET_CODE (XEXP (x, 0)) == AND)
   	{
  	  rtx in1 = XEXP (XEXP (x, 0), 0), in2 = XEXP (XEXP (x, 0), 1);
  
! 	  if (GET_CODE (in1) == NOT)
! 	    in1 = XEXP (in1, 0);
! 	  else
! 	    in1 = gen_rtx_combine (NOT, GET_MODE (in1), in1);
  
! 	  if (GET_CODE (in2) == NOT)
! 	    in2 = XEXP (in2, 0);
! 	  else if (GET_CODE (in2) == CONST_INT
! 		   && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
! 	    in2 = GEN_INT (GET_MODE_MASK (mode) & ~INTVAL (in2));
! 	  else
! 	    in2 = gen_rtx_combine (NOT, GET_MODE (in2), in2);
  
! 	  if (GET_CODE (in2) == NOT)
  	    {
  	      rtx tem = in2;
  	      in2 = in1; in1 = tem;
--- 3933,3949 ----
        if (GET_CODE (XEXP (x, 0)) == IOR || GET_CODE (XEXP (x, 0)) == AND)
   	{
  	  rtx in1 = XEXP (XEXP (x, 0), 0), in2 = XEXP (XEXP (x, 0), 1);
+ 	  enum machine_mode op_mode;
  
! 	  op_mode = GET_MODE (in1);
! 	  in1 = gen_unary (NOT, op_mode, op_mode, in1);
  
! 	  op_mode = GET_MODE (in2);
! 	  if (op_mode == VOIDmode)
! 	    op_mode = mode;
! 	  in2 = gen_unary (NOT, op_mode, op_mode, in2);
  
! 	  if (GET_CODE (in2) == NOT && GET_CODE (in1) != NOT)
  	    {
  	      rtx tem = in2;
  	      in2 = in1; in1 = tem;
Index: simplify-rtx.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/simplify-rtx.c,v
retrieving revision 1.27
diff -c -p -d -r1.27 simplify-rtx.c
*** simplify-rtx.c	2000/09/17 14:33:37	1.27
--- simplify-rtx.c	2000/09/18 18:22:15
*************** simplify_unary_operation (code, mode, op
*** 583,592 ****
  	 aren't constant.  */
        switch (code)
  	{
- 	case NEG:
  	case NOT:
! 	  /* (not (not X)) == X, similarly for NEG.  */
! 	  if (GET_CODE (op) == code)
  	    return XEXP (op, 0);
  	  break;
  
--- 583,603 ----
  	 aren't constant.  */
        switch (code)
  	{
  	case NOT:
! 	  /* (not (not X)) == X.  */
! 	  if (GET_CODE (op) == NOT)
! 	    return XEXP (op, 0);
! 
! 	  /* (not (eq X Y)) == (ne X Y), etc.  */
! 	  if (mode == BImode && GET_RTX_CLASS (GET_CODE (op)) == '<'
! 	      && can_reverse_comparison_p (op, NULL_RTX))
! 	    return gen_rtx_fmt_ee (reverse_condition (GET_CODE (op)),
! 				   op_mode, XEXP (op, 0), XEXP (op, 1));
! 	  break;
! 
! 	case NEG:
! 	  /* (neg (neg X)) == X.  */
! 	  if (GET_CODE (op) == NEG)
  	    return XEXP (op, 0);
  	  break;