Fix problem in final.c:alter_subreg

[Richard Kenner]

This causes testsuite failures on Alpha.

Thu Nov 15 08:36:39 2001  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>

	* final.c (alter_subreg): If simplify_subreg can't do anything,
	handle REG ourselves and abort for others.

*** final.c	2001/11/14 13:51:09	1.221
--- final.c	2001/11/15 14:48:57
*************** alter_subreg (xp)
*** 3039,3043 ****
      *xp = adjust_address (y, GET_MODE (x), SUBREG_BYTE (x));
    else
!     *xp = simplify_subreg (GET_MODE (x), y, GET_MODE (y), SUBREG_BYTE (x));
    return *xp;
  }
--- 3039,3062 ----
      *xp = adjust_address (y, GET_MODE (x), SUBREG_BYTE (x));
    else
!     {
!       rtx new = simplify_subreg (GET_MODE (x), y, GET_MODE (y),
! 				 SUBREG_BYTE (x));
! 
!       if (new != 0)
! 	*xp = new;
!       /* Simplify_subreg can't handle some REG cases, but we have to.  */
!       else if (GET_CODE (y) == REG)
! 	{
! 	  REGNO (x) = subreg_hard_regno (x, 1);
! 	  PUT_CODE (x, REG);
! 	  ORIGINAL_REGNO (x) = ORIGINAL_REGNO (y);
! 	  /* This field has a different meaning for REGs and SUBREGs.  Make
! 	     sure to clear it!  */
! 	  x->used = 0;
! 	}
!       else
! 	abort ();
!     }
! 
    return *xp;
  }