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/* mpn_div_qr_1 -- mpn by limb division.
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Contributed to the GNU project by Niels Möller and Torbjörn Granlund
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Copyright 1991, 1993, 1994, 1996, 1998-2000, 2002, 2003, 2013 Free Software
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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 either:
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* the GNU Lesser General Public License as published by the Free
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Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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or
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* the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any
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later version.
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or both in parallel, as here.
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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 General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library. If not,
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see https://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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#ifndef DIV_QR_1_NORM_THRESHOLD
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#define DIV_QR_1_NORM_THRESHOLD 3
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#endif
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#ifndef DIV_QR_1_UNNORM_THRESHOLD
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#define DIV_QR_1_UNNORM_THRESHOLD 3
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#endif
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#if GMP_NAIL_BITS > 0
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#error Nail bits not supported
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#endif
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/* Divides {up, n} by d. Writes the n-1 low quotient limbs at {qp,
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* n-1}, and the high quote limb at *qh. Returns remainder. */
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mp_limb_t
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mpn_div_qr_1 (mp_ptr qp, mp_limb_t *qh, mp_srcptr up, mp_size_t n,
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mp_limb_t d)
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{
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unsigned cnt;
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mp_limb_t uh;
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ASSERT (n > 0);
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ASSERT (d > 0);
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if (d & GMP_NUMB_HIGHBIT)
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{
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/* Normalized case */
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mp_limb_t dinv, q;
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uh = up[--n];
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q = (uh >= d);
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*qh = q;
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uh -= (-q) & d;
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if (BELOW_THRESHOLD (n, DIV_QR_1_NORM_THRESHOLD))
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{
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cnt = 0;
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plain:
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while (n > 0)
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{
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mp_limb_t ul = up[--n];
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udiv_qrnnd (qp[n], uh, uh, ul, d);
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}
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return uh >> cnt;
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}
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invert_limb (dinv, d);
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return mpn_div_qr_1n_pi1 (qp, up, n, uh, d, dinv);
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}
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else
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{
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/* Unnormalized case */
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mp_limb_t dinv, ul;
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if (! UDIV_NEEDS_NORMALIZATION
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&& BELOW_THRESHOLD (n, DIV_QR_1_UNNORM_THRESHOLD))
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{
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uh = up[--n];
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udiv_qrnnd (*qh, uh, CNST_LIMB(0), uh, d);
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cnt = 0;
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goto plain;
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}
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count_leading_zeros (cnt, d);
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d <<= cnt;
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#if HAVE_NATIVE_div_qr_1u_pi1
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/* FIXME: Call loop doing on-the-fly normalization */
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#endif
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/* Shift up front, use qp area for shifted copy. A bit messy,
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since we have only n-1 limbs available, and shift the high
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limb manually. */
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uh = up[--n];
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ul = (uh << cnt) | mpn_lshift (qp, up, n, cnt);
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uh >>= (GMP_LIMB_BITS - cnt);
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if (UDIV_NEEDS_NORMALIZATION
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&& BELOW_THRESHOLD (n, DIV_QR_1_UNNORM_THRESHOLD))
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{
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udiv_qrnnd (*qh, uh, uh, ul, d);
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up = qp;
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goto plain;
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}
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invert_limb (dinv, d);
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udiv_qrnnd_preinv (*qh, uh, uh, ul, d, dinv);
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return mpn_div_qr_1n_pi1 (qp, qp, n, uh, d, dinv) >> cnt;
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}
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}
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