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b58ddff026
* merged mpfr 3.0.0 and gmp 5.0.1 in buildtools trunk git-svn-id: file:///srv/svn/repos/haiku/buildtools/trunk@37378 a95241bf-73f2-0310-859d-f6bbb57e9c96
142 lines
3.5 KiB
C
142 lines
3.5 KiB
C
/* mpn_mod_1s_2p (ap, n, b, cps)
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Divide (ap,,n) by b. Return the single-limb remainder.
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Requires that b < B / 2.
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Contributed to the GNU project by Torbjorn Granlund.
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THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH MUTABLE INTERFACES. IT IS ONLY
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SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
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GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
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Copyright 2008, 2009 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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void
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mpn_mod_1s_2p_cps (mp_limb_t cps[5], mp_limb_t b)
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{
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mp_limb_t bi;
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mp_limb_t B1modb, B2modb, B3modb;
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int cnt;
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ASSERT (b <= (~(mp_limb_t) 0) / 2);
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count_leading_zeros (cnt, b);
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b <<= cnt;
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invert_limb (bi, b);
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B1modb = -b * ((bi >> (GMP_LIMB_BITS-cnt)) | (CNST_LIMB(1) << cnt));
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ASSERT (B1modb <= b); /* NB: not fully reduced mod b */
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udiv_rnd_preinv (B2modb, B1modb, b, bi);
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udiv_rnd_preinv (B3modb, B2modb, b, bi);
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cps[0] = bi;
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cps[1] = cnt;
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cps[2] = B1modb >> cnt;
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cps[3] = B2modb >> cnt;
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cps[4] = B3modb >> cnt;
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#if WANT_ASSERT
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{
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int i;
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b = cps[2];
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for (i = 3; i <= 4; i++)
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{
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b += cps[i];
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ASSERT (b >= cps[i]);
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}
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}
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#endif
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}
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mp_limb_t
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mpn_mod_1s_2p (mp_srcptr ap, mp_size_t n, mp_limb_t b, mp_limb_t cps[5])
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{
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mp_limb_t rh, rl, bi, q, ph, pl, ch, cl, r;
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mp_limb_t B1modb, B2modb, B3modb;
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mp_size_t i;
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int cnt;
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ASSERT (n >= 1);
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B1modb = cps[2];
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B2modb = cps[3];
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B3modb = cps[4];
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if ((n & 1) != 0)
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{
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if (n == 1)
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{
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rl = ap[n - 1];
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bi = cps[0];
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cnt = cps[1];
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udiv_qrnnd_preinv (q, r, rl >> (GMP_LIMB_BITS - cnt),
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rl << cnt, b, bi);
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return r >> cnt;
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}
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umul_ppmm (ph, pl, ap[n - 2], B1modb);
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add_ssaaaa (ph, pl, ph, pl, 0, ap[n - 3]);
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umul_ppmm (rh, rl, ap[n - 1], B2modb);
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add_ssaaaa (rh, rl, rh, rl, ph, pl);
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n--;
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}
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else
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{
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umul_ppmm (rh, rl, ap[n - 1], B1modb);
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add_ssaaaa (rh, rl, rh, rl, 0, ap[n - 2]);
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}
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for (i = n - 4; i >= 0; i -= 2)
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{
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/* rr = ap[i] < B
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+ ap[i+1] * (B mod b) <= (B-1)(b-1)
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+ LO(rr) * (B^2 mod b) <= (B-1)(b-1)
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+ HI(rr) * (B^3 mod b) <= (B-1)(b-1)
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*/
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umul_ppmm (ph, pl, ap[i + 1], B1modb);
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add_ssaaaa (ph, pl, ph, pl, 0, ap[i + 0]);
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umul_ppmm (ch, cl, rl, B2modb);
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add_ssaaaa (ph, pl, ph, pl, ch, cl);
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umul_ppmm (rh, rl, rh, B3modb);
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add_ssaaaa (rh, rl, rh, rl, ph, pl);
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}
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bi = cps[0];
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cnt = cps[1];
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#if 1
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umul_ppmm (rh, cl, rh, B1modb);
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add_ssaaaa (rh, rl, rh, rl, 0, cl);
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r = (rh << cnt) | (rl >> (GMP_LIMB_BITS - cnt));
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#else
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udiv_qrnnd_preinv (q, r, rh >> (GMP_LIMB_BITS - cnt),
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(rh << cnt) | (rl >> (GMP_LIMB_BITS - cnt)), b, bi);
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ASSERT (q <= 2); /* optimize for small quotient? */
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#endif
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udiv_qrnnd_preinv (q, r, r, rl << cnt, b, bi);
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return r >> cnt;
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}
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