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Annotation of OpenXM_contrib/gmp/mpn/generic/mod_34lsub1.c, Revision 1.1

1.1     ! ohara       1: /* mpn_mod_34lsub1 -- remainder modulo 2^(BITS_PER_MP_LIMB*3/4)-1.
        !             2:
        !             3:    THE FUNCTIONS IN THIS FILE ARE FOR INTERNAL USE ONLY.  THEY'RE ALMOST
        !             4:    CERTAIN TO BE SUBJECT TO INCOMPATIBLE CHANGES OR DISAPPEAR COMPLETELY IN
        !             5:    FUTURE GNU MP RELEASES.
        !             6:
        !             7: Copyright 2000, 2001, 2002 Free Software Foundation, Inc.
        !             8:
        !             9: This file is part of the GNU MP Library.
        !            10:
        !            11: The GNU MP Library is free software; you can redistribute it and/or modify
        !            12: it under the terms of the GNU Lesser General Public License as published by
        !            13: the Free Software Foundation; either version 2.1 of the License, or (at your
        !            14: option) any later version.
        !            15:
        !            16: The GNU MP Library is distributed in the hope that it will be useful, but
        !            17: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            18: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
        !            19: License for more details.
        !            20:
        !            21: You should have received a copy of the GNU Lesser General Public License
        !            22: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
        !            23: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            24: MA 02111-1307, USA. */
        !            25:
        !            26:
        !            27: #include "gmp.h"
        !            28: #include "gmp-impl.h"
        !            29:
        !            30:
        !            31: /* Calculate a remainder from {p,n} divided by 2^(BITS_PER_MP_LIMB*3/4)-1.
        !            32:    The remainder is not fully reduced, it's any limb value congruent to
        !            33:    {p,n} modulo that divisor.
        !            34:
        !            35:    This implementation is only correct when BITS_PER_MP_LIMB is a multiple
        !            36:    of 4, but that suffices for all current uses.  */
        !            37:
        !            38: #if BITS_PER_MP_LIMB % 4 == 0
        !            39:
        !            40: #define B1  (BITS_PER_MP_LIMB / 4)
        !            41: #define B2  (B1 * 2)
        !            42: #define B3  (B1 * 3)
        !            43:
        !            44: #define M1  ((CNST_LIMB(1) << B1) - 1)
        !            45: #define M2  ((CNST_LIMB(1) << B2) - 1)
        !            46: #define M3  ((CNST_LIMB(1) << B3) - 1)
        !            47:
        !            48: #define LOW0(n)      ((n) & M3)
        !            49: #define HIGH0(n)     ((n) >> B3)
        !            50:
        !            51: #define LOW1(n)      (((n) & M2) << B1)
        !            52: #define HIGH1(n)     ((n) >> B2)
        !            53:
        !            54: #define LOW2(n)      (((n) & M1) << B2)
        !            55: #define HIGH2(n)     ((n) >> B1)
        !            56:
        !            57: #define PARTS0(n)    (LOW0(n) + HIGH0(n))
        !            58: #define PARTS1(n)    (LOW1(n) + HIGH1(n))
        !            59: #define PARTS2(n)    (LOW2(n) + HIGH2(n))
        !            60:
        !            61: #define ADD(c,a,val)    \
        !            62:   do {                  \
        !            63:     mp_limb_t  l = val; \
        !            64:     a += l;             \
        !            65:     c += (a < l);       \
        !            66:   } while (0)
        !            67:
        !            68: mp_limb_t
        !            69: mpn_mod_34lsub1 (mp_srcptr p, mp_size_t n)
        !            70: {
        !            71:   mp_limb_t  c0 = 0;
        !            72:   mp_limb_t  c1 = 0;
        !            73:   mp_limb_t  c2 = 0;
        !            74:   mp_limb_t  a0, a1, a2;
        !            75:
        !            76:   ASSERT (n >= 1);
        !            77:
        !            78:   a0 = a1 = a2 = 0;
        !            79:   c0 = c1 = c2 = 0;
        !            80:
        !            81:   while ((n -= 3) >= 0)
        !            82:     {
        !            83:       ADD (c0, a0, p[0]);
        !            84:       ADD (c1, a1, p[1]);
        !            85:       ADD (c2, a2, p[2]);
        !            86:       p += 3;
        !            87:     }
        !            88:
        !            89:   if (n != -3)
        !            90:     {
        !            91:       ADD (c0, a0, p[0]);
        !            92:       if (n != -2)
        !            93:        ADD (c1, a1, p[1]);
        !            94:     }
        !            95:
        !            96:   return
        !            97:     PARTS0 (a0) + PARTS1 (a1) + PARTS2 (a2)
        !            98:     + PARTS1 (c0) + PARTS2 (c1) + PARTS0 (c2);
        !            99: }
        !           100:
        !           101: #endif