--- /dev/null
+/* mpn_divrem_1(quot_ptr, qsize, dividend_ptr, dividend_size, divisor_limb) --
+ Divide (DIVIDEND_PTR,,DIVIDEND_SIZE) by DIVISOR_LIMB.
+ Write DIVIDEND_SIZE limbs of quotient at QUOT_PTR.
+ Return the single-limb remainder.
+ There are no constraints on the value of the divisor.
+
+ QUOT_PTR and DIVIDEND_PTR might point to the same limb.
+
+Copyright (C) 1991, 1993, 1994, 1996, 1998, 1999, 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"
+
+
+
+/* __gmpn_divmod_1_internal(quot_ptr,dividend_ptr,dividend_size,divisor_limb)
+ Divide (DIVIDEND_PTR,,DIVIDEND_SIZE) by DIVISOR_LIMB.
+ Write DIVIDEND_SIZE limbs of quotient at QUOT_PTR.
+ Return the single-limb remainder.
+ There are no constraints on the value of the divisor.
+
+ QUOT_PTR and DIVIDEND_PTR might point to the same limb. */
+
+#ifndef UMUL_TIME
+#define UMUL_TIME 1
+#endif
+
+#ifndef UDIV_TIME
+#define UDIV_TIME UMUL_TIME
+#endif
+
+static mp_limb_t
+#if __STDC__
+__gmpn_divmod_1_internal (mp_ptr quot_ptr,
+ mp_srcptr dividend_ptr, mp_size_t dividend_size,
+ mp_limb_t divisor_limb)
+#else
+__gmpn_divmod_1_internal (quot_ptr, dividend_ptr, dividend_size, divisor_limb)
+ mp_ptr quot_ptr;
+ mp_srcptr dividend_ptr;
+ mp_size_t dividend_size;
+ mp_limb_t divisor_limb;
+#endif
+{
+ mp_size_t i;
+ mp_limb_t n1, n0, r;
+ int dummy;
+
+ /* ??? Should this be handled at all? Rely on callers? */
+ if (dividend_size == 0)
+ return 0;
+
+ /* If multiplication is much faster than division, and the
+ dividend is large, pre-invert the divisor, and use
+ only multiplications in the inner loop. */
+
+ /* This test should be read:
+ Does it ever help to use udiv_qrnnd_preinv?
+ && Does what we save compensate for the inversion overhead? */
+ if (UDIV_TIME > (2 * UMUL_TIME + 6)
+ && (UDIV_TIME - (2 * UMUL_TIME + 6)) * dividend_size > UDIV_TIME)
+ {
+ int normalization_steps;
+
+ count_leading_zeros (normalization_steps, divisor_limb);
+ if (normalization_steps != 0)
+ {
+ mp_limb_t divisor_limb_inverted;
+
+ divisor_limb <<= normalization_steps;
+ invert_limb (divisor_limb_inverted, divisor_limb);
+
+ n1 = dividend_ptr[dividend_size - 1];
+ r = n1 >> (BITS_PER_MP_LIMB - normalization_steps);
+
+ /* Possible optimization:
+ if (r == 0
+ && divisor_limb > ((n1 << normalization_steps)
+ | (dividend_ptr[dividend_size - 2] >> ...)))
+ ...one division less... */
+
+ for (i = dividend_size - 2; i >= 0; i--)
+ {
+ n0 = dividend_ptr[i];
+ udiv_qrnnd_preinv (quot_ptr[i + 1], r, r,
+ ((n1 << normalization_steps)
+ | (n0 >> (BITS_PER_MP_LIMB - normalization_steps))),
+ divisor_limb, divisor_limb_inverted);
+ n1 = n0;
+ }
+ udiv_qrnnd_preinv (quot_ptr[0], r, r,
+ n1 << normalization_steps,
+ divisor_limb, divisor_limb_inverted);
+ return r >> normalization_steps;
+ }
+ else
+ {
+ mp_limb_t divisor_limb_inverted;
+
+ invert_limb (divisor_limb_inverted, divisor_limb);
+
+ i = dividend_size - 1;
+ r = dividend_ptr[i];
+
+ if (r >= divisor_limb)
+ r = 0;
+ else
+ {
+ quot_ptr[i] = 0;
+ i--;
+ }
+
+ for (; i >= 0; i--)
+ {
+ n0 = dividend_ptr[i];
+ udiv_qrnnd_preinv (quot_ptr[i], r, r,
+ n0, divisor_limb, divisor_limb_inverted);
+ }
+ return r;
+ }
+ }
+ else
+ {
+ if (UDIV_NEEDS_NORMALIZATION)
+ {
+ int normalization_steps;
+
+ count_leading_zeros (normalization_steps, divisor_limb);
+ if (normalization_steps != 0)
+ {
+ divisor_limb <<= normalization_steps;
+
+ n1 = dividend_ptr[dividend_size - 1];
+ r = n1 >> (BITS_PER_MP_LIMB - normalization_steps);
+
+ /* Possible optimization:
+ if (r == 0
+ && divisor_limb > ((n1 << normalization_steps)
+ | (dividend_ptr[dividend_size - 2] >> ...)))
+ ...one division less... */
+
+ for (i = dividend_size - 2; i >= 0; i--)
+ {
+ n0 = dividend_ptr[i];
+ udiv_qrnnd (quot_ptr[i + 1], r, r,
+ ((n1 << normalization_steps)
+ | (n0 >> (BITS_PER_MP_LIMB - normalization_steps))),
+ divisor_limb);
+ n1 = n0;
+ }
+ udiv_qrnnd (quot_ptr[0], r, r,
+ n1 << normalization_steps,
+ divisor_limb);
+ return r >> normalization_steps;
+ }
+ }
+ /* No normalization needed, either because udiv_qrnnd doesn't require
+ it, or because DIVISOR_LIMB is already normalized. */
+
+ i = dividend_size - 1;
+ r = dividend_ptr[i];
+
+ if (r >= divisor_limb)
+ r = 0;
+ else
+ {
+ quot_ptr[i] = 0;
+ i--;
+ }
+
+ for (; i >= 0; i--)
+ {
+ n0 = dividend_ptr[i];
+ udiv_qrnnd (quot_ptr[i], r, r, n0, divisor_limb);
+ }
+ return r;
+ }
+}
+
+
+
+mp_limb_t
+#if __STDC__
+mpn_divrem_1 (mp_ptr qp, mp_size_t qxn,
+ mp_srcptr np, mp_size_t nn,
+ mp_limb_t d)
+#else
+mpn_divrem_1 (qp, qxn, np, nn, d)
+ mp_ptr qp;
+ mp_size_t qxn;
+ mp_srcptr np;
+ mp_size_t nn;
+ mp_limb_t d;
+#endif
+{
+ mp_limb_t rlimb;
+ mp_size_t i;
+
+ /* Develop integer part of quotient. */
+ rlimb = __gmpn_divmod_1_internal (qp + qxn, np, nn, d);
+
+ /* Develop fraction part of quotient. This is not as fast as it should;
+ the preinvert stuff from __gmpn_divmod_1_internal ought to be used here
+ too. */
+ if (UDIV_NEEDS_NORMALIZATION)
+ {
+ int normalization_steps;
+
+ count_leading_zeros (normalization_steps, d);
+ if (normalization_steps != 0)
+ {
+ d <<= normalization_steps;
+ rlimb <<= normalization_steps;
+
+ for (i = qxn - 1; i >= 0; i--)
+ udiv_qrnnd (qp[i], rlimb, rlimb, 0, d);
+
+ return rlimb >> normalization_steps;
+ }
+ else
+ /* fall out */
+ ;
+ }
+
+ for (i = qxn - 1; i >= 0; i--)
+ udiv_qrnnd (qp[i], rlimb, rlimb, 0, d);
+
+ return rlimb;
+}
projects / ghc-hetmet.git / blobdiff