version 1.1.1.1, 2000/01/10 15:35:23 |
version 1.1.1.2, 2000/09/09 14:12:24 |
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QUOT_PTR and DIVIDEND_PTR might point to the same limb. |
QUOT_PTR and DIVIDEND_PTR might point to the same limb. |
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Copyright (C) 1996 Free Software Foundation, Inc. |
Copyright (C) 1991, 1993, 1994, 1996, 1998, 1999, 2000 Free Software |
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Foundation, Inc. |
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This file is part of the GNU MP Library. |
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 |
The GNU MP Library is free software; you can redistribute it and/or modify |
it under the terms of the GNU Library General Public License as published by |
it under the terms of the GNU Lesser General Public License as published by |
the Free Software Foundation; either version 2 of the License, or (at your |
the Free Software Foundation; either version 2.1 of the License, or (at your |
option) any later version. |
option) any later version. |
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The GNU MP Library is distributed in the hope that it will be useful, but |
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 |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
License for more details. |
License for more details. |
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You should have received a copy of the GNU Library General Public License |
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 |
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, |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
MA 02111-1307, USA. */ |
MA 02111-1307, USA. */ |
Line 29 MA 02111-1307, USA. */ |
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Line 30 MA 02111-1307, USA. */ |
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#include "gmp-impl.h" |
#include "gmp-impl.h" |
#include "longlong.h" |
#include "longlong.h" |
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mp_limb_t |
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/* __gmpn_divmod_1_internal(quot_ptr,dividend_ptr,dividend_size,divisor_limb) |
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Divide (DIVIDEND_PTR,,DIVIDEND_SIZE) by DIVISOR_LIMB. |
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Write DIVIDEND_SIZE limbs of quotient at QUOT_PTR. |
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Return the single-limb remainder. |
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There are no constraints on the value of the divisor. |
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QUOT_PTR and DIVIDEND_PTR might point to the same limb. */ |
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#ifndef UMUL_TIME |
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#define UMUL_TIME 1 |
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#endif |
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#ifndef UDIV_TIME |
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#define UDIV_TIME UMUL_TIME |
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#endif |
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static mp_limb_t |
#if __STDC__ |
#if __STDC__ |
mpn_divrem_1 (mp_ptr qp, mp_size_t qsize, |
__gmpn_divmod_1_internal (mp_ptr quot_ptr, |
mp_srcptr dividend_ptr, mp_size_t dividend_size, |
mp_srcptr dividend_ptr, mp_size_t dividend_size, |
mp_limb_t divisor_limb) |
mp_limb_t divisor_limb) |
#else |
#else |
mpn_divrem_1 (qp, qsize, dividend_ptr, dividend_size, divisor_limb) |
__gmpn_divmod_1_internal (quot_ptr, dividend_ptr, dividend_size, divisor_limb) |
mp_ptr qp; |
mp_ptr quot_ptr; |
mp_size_t qsize; |
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mp_srcptr dividend_ptr; |
mp_srcptr dividend_ptr; |
mp_size_t dividend_size; |
mp_size_t dividend_size; |
mp_limb_t divisor_limb; |
mp_limb_t divisor_limb; |
#endif |
#endif |
{ |
{ |
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mp_size_t i; |
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mp_limb_t n1, n0, r; |
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int dummy; |
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/* ??? Should this be handled at all? Rely on callers? */ |
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if (dividend_size == 0) |
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return 0; |
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/* If multiplication is much faster than division, and the |
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dividend is large, pre-invert the divisor, and use |
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only multiplications in the inner loop. */ |
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/* This test should be read: |
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Does it ever help to use udiv_qrnnd_preinv? |
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&& Does what we save compensate for the inversion overhead? */ |
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if (UDIV_TIME > (2 * UMUL_TIME + 6) |
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&& (UDIV_TIME - (2 * UMUL_TIME + 6)) * dividend_size > UDIV_TIME) |
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{ |
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int normalization_steps; |
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count_leading_zeros (normalization_steps, divisor_limb); |
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if (normalization_steps != 0) |
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{ |
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mp_limb_t divisor_limb_inverted; |
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divisor_limb <<= normalization_steps; |
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invert_limb (divisor_limb_inverted, divisor_limb); |
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n1 = dividend_ptr[dividend_size - 1]; |
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r = n1 >> (BITS_PER_MP_LIMB - normalization_steps); |
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/* Possible optimization: |
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if (r == 0 |
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&& divisor_limb > ((n1 << normalization_steps) |
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| (dividend_ptr[dividend_size - 2] >> ...))) |
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...one division less... */ |
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for (i = dividend_size - 2; i >= 0; i--) |
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{ |
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n0 = dividend_ptr[i]; |
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udiv_qrnnd_preinv (quot_ptr[i + 1], r, r, |
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((n1 << normalization_steps) |
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| (n0 >> (BITS_PER_MP_LIMB - normalization_steps))), |
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divisor_limb, divisor_limb_inverted); |
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n1 = n0; |
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} |
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udiv_qrnnd_preinv (quot_ptr[0], r, r, |
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n1 << normalization_steps, |
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divisor_limb, divisor_limb_inverted); |
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return r >> normalization_steps; |
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} |
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else |
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{ |
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mp_limb_t divisor_limb_inverted; |
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invert_limb (divisor_limb_inverted, divisor_limb); |
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i = dividend_size - 1; |
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r = dividend_ptr[i]; |
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if (r >= divisor_limb) |
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r = 0; |
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else |
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{ |
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quot_ptr[i] = 0; |
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i--; |
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} |
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for (; i >= 0; i--) |
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{ |
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n0 = dividend_ptr[i]; |
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udiv_qrnnd_preinv (quot_ptr[i], r, r, |
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n0, divisor_limb, divisor_limb_inverted); |
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} |
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return r; |
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} |
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} |
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else |
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{ |
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if (UDIV_NEEDS_NORMALIZATION) |
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{ |
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int normalization_steps; |
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count_leading_zeros (normalization_steps, divisor_limb); |
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if (normalization_steps != 0) |
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{ |
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divisor_limb <<= normalization_steps; |
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n1 = dividend_ptr[dividend_size - 1]; |
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r = n1 >> (BITS_PER_MP_LIMB - normalization_steps); |
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/* Possible optimization: |
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if (r == 0 |
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&& divisor_limb > ((n1 << normalization_steps) |
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| (dividend_ptr[dividend_size - 2] >> ...))) |
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...one division less... */ |
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for (i = dividend_size - 2; i >= 0; i--) |
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{ |
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n0 = dividend_ptr[i]; |
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udiv_qrnnd (quot_ptr[i + 1], r, r, |
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((n1 << normalization_steps) |
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| (n0 >> (BITS_PER_MP_LIMB - normalization_steps))), |
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divisor_limb); |
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n1 = n0; |
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} |
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udiv_qrnnd (quot_ptr[0], r, r, |
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n1 << normalization_steps, |
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divisor_limb); |
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return r >> normalization_steps; |
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} |
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} |
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/* No normalization needed, either because udiv_qrnnd doesn't require |
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it, or because DIVISOR_LIMB is already normalized. */ |
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i = dividend_size - 1; |
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r = dividend_ptr[i]; |
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if (r >= divisor_limb) |
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r = 0; |
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else |
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{ |
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quot_ptr[i] = 0; |
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i--; |
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} |
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for (; i >= 0; i--) |
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{ |
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n0 = dividend_ptr[i]; |
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udiv_qrnnd (quot_ptr[i], r, r, n0, divisor_limb); |
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} |
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return r; |
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} |
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} |
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mp_limb_t |
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#if __STDC__ |
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mpn_divrem_1 (mp_ptr qp, mp_size_t qxn, |
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mp_srcptr np, mp_size_t nn, |
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mp_limb_t d) |
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#else |
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mpn_divrem_1 (qp, qxn, np, nn, d) |
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mp_ptr qp; |
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mp_size_t qxn; |
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mp_srcptr np; |
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mp_size_t nn; |
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mp_limb_t d; |
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#endif |
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{ |
mp_limb_t rlimb; |
mp_limb_t rlimb; |
long i; |
mp_size_t i; |
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/* Develop integer part of quotient. */ |
/* Develop integer part of quotient. */ |
rlimb = mpn_divmod_1 (qp + qsize, dividend_ptr, dividend_size, divisor_limb); |
rlimb = __gmpn_divmod_1_internal (qp + qxn, np, nn, d); |
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if (qsize != 0) |
/* Develop fraction part of quotient. This is not as fast as it should; |
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the preinvert stuff from __gmpn_divmod_1_internal ought to be used here |
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too. */ |
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if (UDIV_NEEDS_NORMALIZATION) |
{ |
{ |
for (i = qsize - 1; i >= 0; i--) |
int normalization_steps; |
udiv_qrnnd (qp[i], rlimb, rlimb, 0, divisor_limb); |
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count_leading_zeros (normalization_steps, d); |
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if (normalization_steps != 0) |
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{ |
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d <<= normalization_steps; |
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rlimb <<= normalization_steps; |
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for (i = qxn - 1; i >= 0; i--) |
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udiv_qrnnd (qp[i], rlimb, rlimb, 0, d); |
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return rlimb >> normalization_steps; |
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} |
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else |
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/* fall out */ |
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; |
} |
} |
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for (i = qxn - 1; i >= 0; i--) |
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udiv_qrnnd (qp[i], rlimb, rlimb, 0, d); |
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return rlimb; |
return rlimb; |
} |
} |