1 /* mpn_mul_basecase -- Internal routine to multiply two natural numbers
2 of length m and n.
3
4 THIS IS AN INTERNAL FUNCTION WITH A MUTABLE INTERFACE. IT IS ONLY
5 SAFE TO REACH THIS FUNCTION THROUGH DOCUMENTED INTERFACES.
6
7 Copyright 1991-1994, 1996, 1997, 2000-2002 Free Software Foundation, Inc.
8
9 This file is part of the GNU MP Library.
10
11 The GNU MP Library is free software; you can redistribute it and/or modify
12 it under the terms of either:
13
14 * the GNU Lesser General Public License as published by the Free
15 Software Foundation; either version 3 of the License, or (at your
16 option) any later version.
17
18 or
19
20 * the GNU General Public License as published by the Free Software
21 Foundation; either version 2 of the License, or (at your option) any
22 later version.
23
24 or both in parallel, as here.
25
26 The GNU MP Library is distributed in the hope that it will be useful, but
27 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
28 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
29 for more details.
30
31 You should have received copies of the GNU General Public License and the
32 GNU Lesser General Public License along with the GNU MP Library. If not,
33 see https://www.gnu.org/licenses/. */
34
35 #include "gmp.h"
36 #include "gmp-impl.h"
37
38
39 /* Multiply {up,usize} by {vp,vsize} and write the result to
40 {prodp,usize+vsize}. Must have usize>=vsize.
41
42 Note that prodp gets usize+vsize limbs stored, even if the actual result
43 only needs usize+vsize-1.
44
45 There's no good reason to call here with vsize>=MUL_TOOM22_THRESHOLD.
46 Currently this is allowed, but it might not be in the future.
47
48 This is the most critical code for multiplication. All multiplies rely
49 on this, both small and huge. Small ones arrive here immediately, huge
50 ones arrive here as this is the base case for Karatsuba's recursive
51 algorithm. */
52
53 void
mpn_mul_basecase(mp_ptr rp,mp_srcptr up,mp_size_t un,mp_srcptr vp,mp_size_t vn)54 mpn_mul_basecase (mp_ptr rp,
55 mp_srcptr up, mp_size_t un,
56 mp_srcptr vp, mp_size_t vn)
57 {
58 ASSERT (un >= vn);
59 ASSERT (vn >= 1);
60 ASSERT (! MPN_OVERLAP_P (rp, un+vn, up, un));
61 ASSERT (! MPN_OVERLAP_P (rp, un+vn, vp, vn));
62
63 /* We first multiply by the low order limb (or depending on optional function
64 availability, limbs). This result can be stored, not added, to rp. We
65 also avoid a loop for zeroing this way. */
66
67 #if HAVE_NATIVE_mpn_mul_2
68 if (vn >= 2)
69 {
70 rp[un + 1] = mpn_mul_2 (rp, up, un, vp);
71 rp += 2, vp += 2, vn -= 2;
72 }
73 else
74 {
75 rp[un] = mpn_mul_1 (rp, up, un, vp[0]);
76 return;
77 }
78 #else
79 rp[un] = mpn_mul_1 (rp, up, un, vp[0]);
80 rp += 1, vp += 1, vn -= 1;
81 #endif
82
83 /* Now accumulate the product of up[] and the next higher limb (or depending
84 on optional function availability, limbs) from vp[]. */
85
86 #define MAX_LEFT MP_SIZE_T_MAX /* Used to simplify loops into if statements */
87
88
89 #if HAVE_NATIVE_mpn_addmul_6
90 while (vn >= 6)
91 {
92 rp[un + 6 - 1] = mpn_addmul_6 (rp, up, un, vp);
93 if (MAX_LEFT == 6)
94 return;
95 rp += 6, vp += 6, vn -= 6;
96 if (MAX_LEFT < 2 * 6)
97 break;
98 }
99 #undef MAX_LEFT
100 #define MAX_LEFT (6 - 1)
101 #endif
102
103 #if HAVE_NATIVE_mpn_addmul_5
104 while (vn >= 5)
105 {
106 rp[un + 5 - 1] = mpn_addmul_5 (rp, up, un, vp);
107 if (MAX_LEFT == 5)
108 return;
109 rp += 5, vp += 5, vn -= 5;
110 if (MAX_LEFT < 2 * 5)
111 break;
112 }
113 #undef MAX_LEFT
114 #define MAX_LEFT (5 - 1)
115 #endif
116
117 #if HAVE_NATIVE_mpn_addmul_4
118 while (vn >= 4)
119 {
120 rp[un + 4 - 1] = mpn_addmul_4 (rp, up, un, vp);
121 if (MAX_LEFT == 4)
122 return;
123 rp += 4, vp += 4, vn -= 4;
124 if (MAX_LEFT < 2 * 4)
125 break;
126 }
127 #undef MAX_LEFT
128 #define MAX_LEFT (4 - 1)
129 #endif
130
131 #if HAVE_NATIVE_mpn_addmul_3
132 while (vn >= 3)
133 {
134 rp[un + 3 - 1] = mpn_addmul_3 (rp, up, un, vp);
135 if (MAX_LEFT == 3)
136 return;
137 rp += 3, vp += 3, vn -= 3;
138 if (MAX_LEFT < 2 * 3)
139 break;
140 }
141 #undef MAX_LEFT
142 #define MAX_LEFT (3 - 1)
143 #endif
144
145 #if HAVE_NATIVE_mpn_addmul_2
146 while (vn >= 2)
147 {
148 rp[un + 2 - 1] = mpn_addmul_2 (rp, up, un, vp);
149 if (MAX_LEFT == 2)
150 return;
151 rp += 2, vp += 2, vn -= 2;
152 if (MAX_LEFT < 2 * 2)
153 break;
154 }
155 #undef MAX_LEFT
156 #define MAX_LEFT (2 - 1)
157 #endif
158
159 while (vn >= 1)
160 {
161 rp[un] = mpn_addmul_1 (rp, up, un, vp[0]);
162 if (MAX_LEFT == 1)
163 return;
164 rp += 1, vp += 1, vn -= 1;
165 }
166 }
167