diff options
Diffstat (limited to 'vendor/gmp-6.3.0/mpn/generic/div_qr_1.c')
-rw-r--r-- | vendor/gmp-6.3.0/mpn/generic/div_qr_1.c | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/vendor/gmp-6.3.0/mpn/generic/div_qr_1.c b/vendor/gmp-6.3.0/mpn/generic/div_qr_1.c new file mode 100644 index 0000000..8f80d37 --- /dev/null +++ b/vendor/gmp-6.3.0/mpn/generic/div_qr_1.c @@ -0,0 +1,125 @@ +/* mpn_div_qr_1 -- mpn by limb division. + + Contributed to the GNU project by Niels Möller and Torbjörn Granlund + +Copyright 1991, 1993, 1994, 1996, 1998-2000, 2002, 2003, 2013 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 either: + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at your + option) any later version. + +or + + * the GNU General Public License as published by the Free Software + Foundation; either version 2 of the License, or (at your option) any + later version. + +or both in parallel, as here. + +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 General Public License +for more details. + +You should have received copies of the GNU General Public License and the +GNU Lesser General Public License along with the GNU MP Library. If not, +see https://www.gnu.org/licenses/. */ + +#include "gmp-impl.h" +#include "longlong.h" + +#ifndef DIV_QR_1_NORM_THRESHOLD +#define DIV_QR_1_NORM_THRESHOLD 3 +#endif +#ifndef DIV_QR_1_UNNORM_THRESHOLD +#define DIV_QR_1_UNNORM_THRESHOLD 3 +#endif + +#if GMP_NAIL_BITS > 0 +#error Nail bits not supported +#endif + +/* Divides {up, n} by d. Writes the n-1 low quotient limbs at {qp, + * n-1}, and the high quotient limb at *qh. Returns remainder. */ +mp_limb_t +mpn_div_qr_1 (mp_ptr qp, mp_limb_t *qh, mp_srcptr up, mp_size_t n, + mp_limb_t d) +{ + unsigned cnt; + mp_limb_t uh; + + ASSERT (n > 0); + ASSERT (d > 0); + + if (d & GMP_NUMB_HIGHBIT) + { + /* Normalized case */ + mp_limb_t dinv, q; + + uh = up[--n]; + + q = (uh >= d); + *qh = q; + uh -= (-q) & d; + + if (BELOW_THRESHOLD (n, DIV_QR_1_NORM_THRESHOLD)) + { + cnt = 0; + plain: + while (n > 0) + { + mp_limb_t ul = up[--n]; + udiv_qrnnd (qp[n], uh, uh, ul, d); + } + return uh >> cnt; + } + invert_limb (dinv, d); + return mpn_div_qr_1n_pi1 (qp, up, n, uh, d, dinv); + } + else + { + /* Unnormalized case */ + mp_limb_t dinv, ul; + + if (! UDIV_NEEDS_NORMALIZATION + && BELOW_THRESHOLD (n, DIV_QR_1_UNNORM_THRESHOLD)) + { + uh = up[--n]; + udiv_qrnnd (*qh, uh, CNST_LIMB(0), uh, d); + cnt = 0; + goto plain; + } + + count_leading_zeros (cnt, d); + d <<= cnt; + +#if HAVE_NATIVE_mpn_div_qr_1u_pi1 + /* FIXME: Call loop doing on-the-fly normalization */ +#endif + + /* Shift up front, use qp area for shifted copy. A bit messy, + since we have only n-1 limbs available, and shift the high + limb manually. */ + uh = up[--n]; + ul = (uh << cnt) | mpn_lshift (qp, up, n, cnt); + uh >>= (GMP_LIMB_BITS - cnt); + + if (UDIV_NEEDS_NORMALIZATION + && BELOW_THRESHOLD (n, DIV_QR_1_UNNORM_THRESHOLD)) + { + udiv_qrnnd (*qh, uh, uh, ul, d); + up = qp; + goto plain; + } + invert_limb (dinv, d); + + udiv_qrnnd_preinv (*qh, uh, uh, ul, d, dinv); + return mpn_div_qr_1n_pi1 (qp, qp, n, uh, d, dinv) >> cnt; + } +} |