From 11da511c784eca003deb90c23570f0873954e0de Mon Sep 17 00:00:00 2001 From: Duncan Wilkie Date: Sat, 18 Nov 2023 06:11:09 -0600 Subject: Initial commit. --- gmp-6.3.0/mpn/generic/sbpi1_divappr_q.c | 198 ++++++++++++++++++++++++++++++++ 1 file changed, 198 insertions(+) create mode 100644 gmp-6.3.0/mpn/generic/sbpi1_divappr_q.c (limited to 'gmp-6.3.0/mpn/generic/sbpi1_divappr_q.c') diff --git a/gmp-6.3.0/mpn/generic/sbpi1_divappr_q.c b/gmp-6.3.0/mpn/generic/sbpi1_divappr_q.c new file mode 100644 index 0000000..ef7ca26 --- /dev/null +++ b/gmp-6.3.0/mpn/generic/sbpi1_divappr_q.c @@ -0,0 +1,198 @@ +/* mpn_sbpi1_divappr_q -- Schoolbook division using the Möller-Granlund 3/2 + division algorithm, returning approximate quotient. The quotient returned + is either correct, or one too large. + + Contributed to the GNU project by Torbjorn Granlund. + + THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY + SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST + GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GMP RELEASE. + +Copyright 2007, 2009 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" + +mp_limb_t +mpn_sbpi1_divappr_q (mp_ptr qp, + mp_ptr np, mp_size_t nn, + mp_srcptr dp, mp_size_t dn, + mp_limb_t dinv) +{ + mp_limb_t qh; + mp_size_t qn, i; + mp_limb_t n1, n0; + mp_limb_t d1, d0; + mp_limb_t cy, cy1; + mp_limb_t q; + mp_limb_t flag; + + ASSERT (dn > 2); + ASSERT (nn >= dn); + ASSERT ((dp[dn-1] & GMP_NUMB_HIGHBIT) != 0); + + np += nn; + + qn = nn - dn; + if (qn + 1 < dn) + { + dp += dn - (qn + 1); + dn = qn + 1; + } + + qh = mpn_cmp (np - dn, dp, dn) >= 0; + if (qh != 0) + mpn_sub_n (np - dn, np - dn, dp, dn); + + qp += qn; + + dn -= 2; /* offset dn by 2 for main division loops, + saving two iterations in mpn_submul_1. */ + d1 = dp[dn + 1]; + d0 = dp[dn + 0]; + + np -= 2; + + n1 = np[1]; + + for (i = qn - (dn + 2); i >= 0; i--) + { + np--; + if (UNLIKELY (n1 == d1) && np[1] == d0) + { + q = GMP_NUMB_MASK; + mpn_submul_1 (np - dn, dp, dn + 2, q); + n1 = np[1]; /* update n1, last loop's value will now be invalid */ + } + else + { + udiv_qr_3by2 (q, n1, n0, n1, np[1], np[0], d1, d0, dinv); + + cy = mpn_submul_1 (np - dn, dp, dn, q); + + cy1 = n0 < cy; + n0 = (n0 - cy) & GMP_NUMB_MASK; + cy = n1 < cy1; + n1 -= cy1; + np[0] = n0; + + if (UNLIKELY (cy != 0)) + { + n1 += d1 + mpn_add_n (np - dn, np - dn, dp, dn + 1); + q--; + } + } + + *--qp = q; + } + + flag = ~CNST_LIMB(0); + + if (dn >= 0) + { + for (i = dn; i > 0; i--) + { + np--; + if (UNLIKELY (n1 >= (d1 & flag))) + { + q = GMP_NUMB_MASK; + cy = mpn_submul_1 (np - dn, dp, dn + 2, q); + + if (UNLIKELY (n1 != cy)) + { + if (n1 < (cy & flag)) + { + q--; + mpn_add_n (np - dn, np - dn, dp, dn + 2); + } + else + flag = 0; + } + n1 = np[1]; + } + else + { + udiv_qr_3by2 (q, n1, n0, n1, np[1], np[0], d1, d0, dinv); + + cy = mpn_submul_1 (np - dn, dp, dn, q); + + cy1 = n0 < cy; + n0 = (n0 - cy) & GMP_NUMB_MASK; + cy = n1 < cy1; + n1 -= cy1; + np[0] = n0; + + if (UNLIKELY (cy != 0)) + { + n1 += d1 + mpn_add_n (np - dn, np - dn, dp, dn + 1); + q--; + } + } + + *--qp = q; + + /* Truncate operands. */ + dn--; + dp++; + } + + np--; + if (UNLIKELY (n1 >= (d1 & flag))) + { + q = GMP_NUMB_MASK; + cy = mpn_submul_1 (np, dp, 2, q); + + if (UNLIKELY (n1 != cy)) + { + if (n1 < (cy & flag)) + { + q--; + add_ssaaaa (np[1], np[0], np[1], np[0], dp[1], dp[0]); + } + else + flag = 0; + } + n1 = np[1]; + } + else + { + udiv_qr_3by2 (q, n1, n0, n1, np[1], np[0], d1, d0, dinv); + + np[1] = n1; + np[0] = n0; + } + + *--qp = q; + } + + ASSERT_ALWAYS (np[1] == n1); + + return qh; +} -- cgit v1.2.3