1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
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;
}
|
