obvious fix for combine

[Jan Hubicka]

Hi,
another obvious fix for combine.c to solve the powerpc failure I've introduced.
This case an (xor (subreg ...) (const_int 0)) got simplified to
(subreg ...) and op0_mode stopped to match.

Fri May 18 22:27:35 CEST 2001  Jan Hubicka  <jh@suse.cz>

	* combine.c (combine_simplify_rtx): Celar op0_mode if simplification
	suceeded.

Index: combine.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/combine.c,v
retrieving revision 1.201
diff -c -3 -p -r1.201 combine.c
*** combine.c	2001/05/17 21:21:21	1.201
--- combine.c	2001/05/18 20:26:31
*************** combine_simplify_rtx (x, op0_mode, last,
*** 3693,3699 ****
      }
  
    if (temp)
!     x = temp, code = GET_CODE (temp);
  
    /* First see if we can apply the inverse distributive law.  */
    if (code == PLUS || code == MINUS
--- 3693,3699 ----
      }
  
    if (temp)
!     x = temp, code = GET_CODE (temp), op0_mode = VOIDmode;
  
    /* First see if we can apply the inverse distributive law.  */
    if (code == PLUS || code == MINUS