+++ /dev/null
-/* mpn_sb_divrem_mn -- Divide natural numbers, producing both remainder and
- quotient.
-
- THE FUNCTIONS IN THIS FILE ARE INTERNAL FUNCTIONS WITH MUTABLE
- INTERFACES. IT IS ONLY SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES.
- IN FACT, IT IS ALMOST GUARANTEED THAT THEY'LL CHANGE OR DISAPPEAR IN A
- FUTURE GNU MP RELEASE.
-
-
-Copyright (C) 1993, 1994, 1995, 1996, 2000 Free Software Foundation, Inc.
-
-This file is part of the GNU MP Library.
-
-The GNU MP Library is free software; you can redistribute it and/or modify
-it under the terms of the GNU Lesser General Public License as published by
-the Free Software Foundation; either version 2.1 of the License, or (at your
-option) any later version.
-
-The GNU MP Library is distributed in the hope that it will be useful, but
-WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
-License for more details.
-
-You should have received a copy of the GNU Lesser General Public License
-along with the GNU MP Library; see the file COPYING.LIB. If not, write to
-the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
-MA 02111-1307, USA. */
-
-#include "gmp.h"
-#include "gmp-impl.h"
-#include "longlong.h"
-
-/* Divide num (NP/NSIZE) by den (DP/DSIZE) and write
- the NSIZE-DSIZE least significant quotient limbs at QP
- and the DSIZE long remainder at NP. If QEXTRA_LIMBS is
- non-zero, generate that many fraction bits and append them after the
- other quotient limbs.
- Return the most significant limb of the quotient, this is always 0 or 1.
-
- Preconditions:
- 0. NSIZE >= DSIZE.
- 1. The most significant bit of the divisor must be set.
- 2. QP must either not overlap with the input operands at all, or
- QP + DSIZE >= NP must hold true. (This means that it's
- possible to put the quotient in the high part of NUM, right after the
- remainder in NUM.
- 3. NSIZE >= DSIZE, even if QEXTRA_LIMBS is non-zero.
- 4. DSIZE >= 2. */
-
-
-#define PREINVERT_VIABLE \
- (UDIV_TIME > 2 * UMUL_TIME + 6 /* && ! TARGET_REGISTER_STARVED */)
-
-mp_limb_t
-#if __STDC__
-mpn_sb_divrem_mn (mp_ptr qp,
- mp_ptr np, mp_size_t nsize,
- mp_srcptr dp, mp_size_t dsize)
-#else
-mpn_sb_divrem_mn (qp, np, nsize, dp, dsize)
- mp_ptr qp;
- mp_ptr np;
- mp_size_t nsize;
- mp_srcptr dp;
- mp_size_t dsize;
-#endif
-{
- mp_limb_t most_significant_q_limb = 0;
- mp_size_t i;
- mp_limb_t dx, d1, n0;
- mp_limb_t dxinv;
- int have_preinv;
-
- ASSERT_ALWAYS (dsize > 2);
-
- np += nsize - dsize;
- dx = dp[dsize - 1];
- d1 = dp[dsize - 2];
- n0 = np[dsize - 1];
-
- if (n0 >= dx)
- {
- if (n0 > dx || mpn_cmp (np, dp, dsize - 1) >= 0)
- {
- mpn_sub_n (np, np, dp, dsize);
- most_significant_q_limb = 1;
- }
- }
-
- /* If multiplication is much faster than division, preinvert the
- most significant divisor limb before entering the loop. */
- if (PREINVERT_VIABLE)
- {
- have_preinv = 0;
- if ((UDIV_TIME - (2 * UMUL_TIME + 6)) * (nsize - dsize) > UDIV_TIME)
- {
- invert_limb (dxinv, dx);
- have_preinv = 1;
- }
- }
-
- for (i = nsize - dsize - 1; i >= 0; i--)
- {
- mp_limb_t q;
- mp_limb_t nx;
- mp_limb_t cy_limb;
-
- nx = np[dsize - 1];
- np--;
-
- if (nx == dx)
- {
- /* This might over-estimate q, but it's probably not worth
- the extra code here to find out. */
- q = ~(mp_limb_t) 0;
-
-#if 1
- cy_limb = mpn_submul_1 (np, dp, dsize, q);
-#else
- /* This should be faster on many machines */
- cy_limb = mpn_sub_n (np + 1, np + 1, dp, dsize);
- cy = mpn_add_n (np, np, dp, dsize);
- np[dsize] += cy;
-#endif
-
- if (nx != cy_limb)
- {
- mpn_add_n (np, np, dp, dsize);
- q--;
- }
-
- qp[i] = q;
- }
- else
- {
- mp_limb_t rx, r1, r0, p1, p0;
-
- /* "workaround" avoids a problem with gcc 2.7.2.3 i386 register
- usage when np[dsize-1] is used in an asm statement like
- umul_ppmm in udiv_qrnnd_preinv. The symptom is seg faults due
- to registers being clobbered. gcc 2.95 i386 doesn't have the
- problem. */
- {
- mp_limb_t workaround = np[dsize - 1];
- if (PREINVERT_VIABLE && have_preinv)
- udiv_qrnnd_preinv (q, r1, nx, workaround, dx, dxinv);
- else
- udiv_qrnnd (q, r1, nx, workaround, dx);
- }
- umul_ppmm (p1, p0, d1, q);
-
- r0 = np[dsize - 2];
- rx = 0;
- if (r1 < p1 || (r1 == p1 && r0 < p0))
- {
- p1 -= p0 < d1;
- p0 -= d1;
- q--;
- r1 += dx;
- rx = r1 < dx;
- }
-
- p1 += r0 < p0; /* cannot carry! */
- rx -= r1 < p1; /* may become 11..1 if q is still too large */
- r1 -= p1;
- r0 -= p0;
-
- cy_limb = mpn_submul_1 (np, dp, dsize - 2, q);
-
- {
- mp_limb_t cy1, cy2;
- cy1 = r0 < cy_limb;
- r0 -= cy_limb;
- cy2 = r1 < cy1;
- r1 -= cy1;
- np[dsize - 1] = r1;
- np[dsize - 2] = r0;
- if (cy2 != rx)
- {
- mpn_add_n (np, np, dp, dsize);
- q--;
- }
- }
- qp[i] = q;
- }
- }
-
- /* ______ ______ ______
- |__rx__|__r1__|__r0__| partial remainder
- ______ ______
- - |__p1__|__p0__| partial product to subtract
- ______ ______
- - |______|cylimb|
-
- rx is -1, 0 or 1. If rx=1, then q is correct (it should match
- carry out). If rx=-1 then q is too large. If rx=0, then q might
- be too large, but it is most likely correct.
- */
-
- return most_significant_q_limb;
-}
projects / ghc-hetmet.git / blobdiff