Patch to fix lshift_double and rshift_double

[John Wehle]

These routines attempt to shift by HOST_BITS_PER_WIDE_INT when
called with count equal to 2 * HOST_BITS_PER_WIDE_INT.  This
produces unexpected results since shifting by the host word size
is undefined according to ANSI.

ChangeLog:

Thu Dec 30 03:34:10 EST 1999  John Wehle  (john@feith.com)

	* fold-const.c (lshift_double, rshift_double): Handle
	shifting by 2 * HOST_BITS_PER_WIDE_INT correctly.

Enjoy!

-- John Wehle
------------------8<------------------------8<------------------------
*** gcc/fold-const.c.ORIGINAL	Sun Oct 31 20:11:20 1999
--- gcc/fold-const.c	Thu Dec 30 03:15:51 1999
*************** lshift_double (l1, h1, count, prec, lv, 
*** 360,366 ****
      count %= prec;
  #endif
  
!   if (count >= HOST_BITS_PER_WIDE_INT)
      {
        *hv = (unsigned HOST_WIDE_INT) l1 << (count - HOST_BITS_PER_WIDE_INT);
        *lv = 0;
--- 360,373 ----
      count %= prec;
  #endif
  
!   if (count >= 2 * HOST_BITS_PER_WIDE_INT)
!     {
!       /* Shifting by the host word size is undefined according to the
! 	 ANSI standard, so we must handle this as a special case.  */
!       *hv = 0;
!       *lv = 0;
!     }
!   else if (count >= HOST_BITS_PER_WIDE_INT)
      {
        *hv = (unsigned HOST_WIDE_INT) l1 << (count - HOST_BITS_PER_WIDE_INT);
        *lv = 0;
*************** rshift_double (l1, h1, count, prec, lv, 
*** 395,401 ****
      count %= prec;
  #endif
  
!   if (count >= HOST_BITS_PER_WIDE_INT)
      {
        *hv = signmask;
        *lv = ((signmask << (2 * HOST_BITS_PER_WIDE_INT - count - 1) << 1)
--- 402,415 ----
      count %= prec;
  #endif
  
!   if (count >= 2 * HOST_BITS_PER_WIDE_INT)
!     {
!       /* Shifting by the host word size is undefined according to the
! 	 ANSI standard, so we must handle this as a special case.  */
!       *hv = signmask;
!       *lv = signmask;
!     }
!   else if (count >= HOST_BITS_PER_WIDE_INT)
      {
        *hv = signmask;
        *lv = ((signmask << (2 * HOST_BITS_PER_WIDE_INT - count - 1) << 1)
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