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-impl.h"
36
37
38 /* Multiply {up,usize} by {vp,vsize} and write the result to
39 {prodp,usize+vsize}. Must have usize>=vsize.
40
41 Note that prodp gets usize+vsize limbs stored, even if the actual result
42 only needs usize+vsize-1.
43
44 There's no good reason to call here with vsize>=MUL_TOOM22_THRESHOLD.
45 Currently this is allowed, but it might not be in the future.
46
47 This is the most critical code for multiplication. All multiplies rely
48 on this, both small and huge. Small ones arrive here immediately, huge
49 ones arrive here as this is the base case for Karatsuba's recursive
50 algorithm. */
51
52 void
53 mpn_mul_basecase (mp_ptr rp,
54 mp_srcptr up, mp_size_t un,
55 mp_srcptr vp, mp_size_t vn)
56 {
57 ASSERT (un >= vn);
58 ASSERT (vn >= 1);
59 ASSERT (! MPN_OVERLAP_P (rp, un+vn, up, un));
60 ASSERT (! MPN_OVERLAP_P (rp, un+vn, vp, vn));
61
62 /* We first multiply by the low order limb (or depending on optional function
63 availability, limbs). This result can be stored, not added, to rp. We
64 also avoid a loop for zeroing this way. */
65
66 #if HAVE_NATIVE_mpn_mul_2
67 if (vn >= 2)
68 {
69 rp[un + 1] = mpn_mul_2 (rp, up, un, vp);
70 rp += 2, vp += 2, vn -= 2;
71 }
72 else
73 {
74 rp[un] = mpn_mul_1 (rp, up, un, vp[0]);
75 return;
76 }
77 #else
78 rp[un] = mpn_mul_1 (rp, up, un, vp[0]);
79 rp += 1, vp += 1, vn -= 1;
80 #endif
81
82 /* Now accumulate the product of up[] and the next higher limb (or depending
83 on optional function availability, limbs) from vp[]. */
84
85 #define MAX_LEFT MP_SIZE_T_MAX /* Used to simplify loops into if statements */
86
87
88 #if HAVE_NATIVE_mpn_addmul_6
89 while (vn >= 6)
90 {
91 rp[un + 6 - 1] = mpn_addmul_6 (rp, up, un, vp);
92 if (MAX_LEFT == 6)
93 return;
94 rp += 6, vp += 6, vn -= 6;
95 if (MAX_LEFT < 2 * 6)
96 break;
97 }
98 #undef MAX_LEFT
99 #define MAX_LEFT (6 - 1)
100 #endif
101
102 #if HAVE_NATIVE_mpn_addmul_5
103 while (vn >= 5)
104 {
105 rp[un + 5 - 1] = mpn_addmul_5 (rp, up, un, vp);
106 if (MAX_LEFT == 5)
107 return;
108 rp += 5, vp += 5, vn -= 5;
109 if (MAX_LEFT < 2 * 5)
110 break;
111 }
112 #undef MAX_LEFT
113 #define MAX_LEFT (5 - 1)
114 #endif
115
116 #if HAVE_NATIVE_mpn_addmul_4
117 while (vn >= 4)
118 {
119 rp[un + 4 - 1] = mpn_addmul_4 (rp, up, un, vp);
120 if (MAX_LEFT == 4)
121 return;
122 rp += 4, vp += 4, vn -= 4;
123 if (MAX_LEFT < 2 * 4)
124 break;
125 }
126 #undef MAX_LEFT
127 #define MAX_LEFT (4 - 1)
128 #endif
129
130 #if HAVE_NATIVE_mpn_addmul_3
131 while (vn >= 3)
132 {
133 rp[un + 3 - 1] = mpn_addmul_3 (rp, up, un, vp);
134 if (MAX_LEFT == 3)
135 return;
136 rp += 3, vp += 3, vn -= 3;
137 if (MAX_LEFT < 2 * 3)
138 break;
139 }
140 #undef MAX_LEFT
141 #define MAX_LEFT (3 - 1)
142 #endif
143
144 #if HAVE_NATIVE_mpn_addmul_2
145 while (vn >= 2)
146 {
147 rp[un + 2 - 1] = mpn_addmul_2 (rp, up, un, vp);
148 if (MAX_LEFT == 2)
149 return;
150 rp += 2, vp += 2, vn -= 2;
151 if (MAX_LEFT < 2 * 2)
152 break;
153 }
154 #undef MAX_LEFT
155 #define MAX_LEFT (2 - 1)
156 #endif
157
158 while (vn >= 1)
159 {
160 rp[un] = mpn_addmul_1 (rp, up, un, vp[0]);
161 if (MAX_LEFT == 1)
162 return;
163 rp += 1, vp += 1, vn -= 1;
164 }
165 }