redc_2.c revision 1.1.1.2 
1/* mpn_redc_2.  Set rp[] <- up[]/R^n mod mp[].  Clobber up[].
2   mp[] is n limbs; up[] is 2n limbs.
3
4   THIS IS AN INTERNAL FUNCTION WITH A MUTABLE INTERFACE.  IT IS ONLY
5   SAFE TO REACH THIS FUNCTION THROUGH DOCUMENTED INTERFACES.
6
7Copyright (C) 2000, 2001, 2002, 2004, 2008, 2012 Free Software Foundation,
8Inc.
9
10This file is part of the GNU MP Library.
11
12The GNU MP Library is free software; you can redistribute it and/or modify
13it under the terms of the GNU Lesser General Public License as published by
14the Free Software Foundation; either version 3 of the License, or (at your
15option) any later version.
16
17The GNU MP Library is distributed in the hope that it will be useful, but
18WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
19or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
20License for more details.
21
22You should have received a copy of the GNU Lesser General Public License
23along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
24
25#include "gmp.h"
26#include "gmp-impl.h"
27#include "longlong.h"
28
29
30#if GMP_NAIL_BITS != 0
31you lose
32#endif
33
34/* For testing purposes, define our own mpn_addmul_2 if there is none already
35   available.  */
36#ifndef HAVE_NATIVE_mpn_addmul_2
37#undef mpn_addmul_2
38static mp_limb_t
39mpn_addmul_2 (mp_ptr rp, mp_srcptr up, mp_size_t n, mp_srcptr vp)
40{
41  rp[n] = mpn_addmul_1 (rp, up, n, vp[0]);
42  return mpn_addmul_1 (rp + 1, up, n, vp[1]);
43}
44#endif
45
46#if defined (__GNUC__) && defined (__ia64) && W_TYPE_SIZE == 64
47#define umul2low(ph, pl, uh, ul, vh, vl) \
48  do {									\
49    mp_limb_t _ph, _pl;							\
50    __asm__ ("xma.hu %0 = %3, %5, f0\n\t"				\
51	     "xma.l %1 = %3, %5, f0\n\t"				\
52	     ";;\n\t"							\
53	     "xma.l %0 = %3, %4, %0\n\t"				\
54	     ";;\n\t"							\
55	     "xma.l %0 = %2, %5, %0"					\
56	     : "=&f" (ph), "=&f" (pl)					\
57	     : "f" (uh), "f" (ul), "f" (vh), "f" (vl));			\
58  } while (0)
59#endif
60
61#ifndef umul2low
62#define umul2low(ph, pl, uh, ul, vh, vl) \
63  do {									\
64    mp_limb_t _ph, _pl;							\
65    umul_ppmm (_ph, _pl, ul, vl);					\
66    (ph) = _ph + (ul) * (vh) + (uh) * (vl);				\
67    (pl) = _pl;								\
68  } while (0)
69#endif
70
71mp_limb_t
72mpn_redc_2 (mp_ptr rp, mp_ptr up, mp_srcptr mp, mp_size_t n, mp_srcptr mip)
73{
74  mp_limb_t q[2];
75  mp_size_t j;
76  mp_limb_t upn;
77  mp_limb_t cy;
78
79  ASSERT (n > 0);
80  ASSERT_MPN (up, 2*n);
81
82  if ((n & 1) != 0)
83    {
84      up[0] = mpn_addmul_1 (up, mp, n, (up[0] * mip[0]) & GMP_NUMB_MASK);
85      up++;
86    }
87
88  for (j = n - 2; j >= 0; j -= 2)
89    {
90      umul2low (q[1], q[0], mip[1], mip[0], up[1], up[0]);
91      upn = up[n];		/* mpn_addmul_2 overwrites this */
92      up[1] = mpn_addmul_2 (up, mp, n, q);
93      up[0] = up[n];
94      up[n] = upn;
95      up += 2;
96    }
97
98  cy = mpn_add_n (rp, up, up - n, n);
99  return cy;
100}
101