===================================================================
RCS file: /home/cvs/OpenXM_contrib/gmp/mpn/generic/Attic/diveby3.c,v
retrieving revision 1.1
retrieving revision 1.1.1.2
diff -u -p -r1.1 -r1.1.1.2
--- OpenXM_contrib/gmp/mpn/generic/Attic/diveby3.c	2000/09/09 14:12:24	1.1
+++ OpenXM_contrib/gmp/mpn/generic/Attic/diveby3.c	2003/08/25 16:06:20	1.1.1.2
@@ -1,7 +1,7 @@
 /* mpn_divexact_by3 -- mpn division by 3, expecting no remainder. */
 
 /*
-Copyright (C) 2000 Free Software Foundation, Inc.
+Copyright 2000, 2001, 2002 Free Software Foundation, Inc.
 
 This file is part of the GNU MP Library.
 
@@ -26,35 +26,31 @@ MA 02111-1307, USA.
 #include "gmp-impl.h"
 
 
-/* Multiplicative inverse of 3, modulo 2^BITS_PER_MP_LIMB.
-   0xAAAAAAAB for 32 bits, 0xAAAAAAAAAAAAAAAB for 64 bits. */
-#define INVERSE_3      ((MP_LIMB_T_MAX / 3) * 2 + 1)
-
-
 /* The "c += ..."s are adding the high limb of 3*l to c.  That high limb
    will be 0, 1 or 2.  Doing two separate "+="s seems to turn out better
    code on gcc (as of 2.95.2 at least).
 
    When a subtraction of a 0,1,2 carry value causes a borrow, that leaves a
-   limb value of either 0xFF...FF or 0xFF...FE and the multiply by INVERSE_3
-   gives 0x55...55 or 0xAA...AA respectively, producing a further borrow of
-   only 0 or 1 respectively.  Hence the carry out of each stage and for the
-   return value is always only 0, 1 or 2.  */
+   limb value of either 0xFF...FF or 0xFF...FE and the multiply by
+   MODLIMB_INVERSE_3 gives 0x55...55 or 0xAA...AA respectively, producing a
+   further borrow of only 0 or 1 respectively.  Hence the carry out of each
+   stage and for the return value is always only 0, 1 or 2.
 
+   This implementation has each multiply successively dependent due to the
+   "l=s-c", but the multiply src[i]*MODLIMB_INVERSE_3 could be scheduled
+   back as far as desired, and the effect of the "-c" applied by subtracting
+   0, 1 or 2 copies or MODLIMB_INVERSE_3 from the product.  With some good
+   scheduling in assembler it might come down to a dependent chain of maybe
+   5 simple operations per limb.  */
+
 mp_limb_t
-#if __STDC__
 mpn_divexact_by3c (mp_ptr dst, mp_srcptr src, mp_size_t size, mp_limb_t c)
-#else
-mpn_divexact_by3c (dst, src, size, c)
-     mp_ptr    dst;
-     mp_srcptr src;
-     mp_size_t size;
-     mp_limb_t c;
-#endif
 {
   mp_size_t  i;
 
   ASSERT (size >= 1);
+  ASSERT (c == 0 || c == 1 || c == 2);
+  ASSERT (MPN_SAME_OR_SEPARATE_P (dst, src, size));
 
   i = 0;
   do
@@ -65,11 +61,11 @@ mpn_divexact_by3c (dst, src, size, c)
       l = s - c;
       c = (l > s);
 
-      l *= INVERSE_3;
+      l = (l * MODLIMB_INVERSE_3) & GMP_NUMB_MASK;
       dst[i] = l;
 
-      c += (l > MP_LIMB_T_MAX/3);
-      c += (l > (MP_LIMB_T_MAX/3)*2);
+      c += (l > GMP_NUMB_MAX/3);
+      c += (l > (GMP_NUMB_MAX/3)*2);
     }
   while (++i < size);