2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
29 br_i31_montymul(uint32_t *d
, const uint32_t *x
, const uint32_t *y
,
30 const uint32_t *m
, uint32_t m0i
)
32 size_t len
, len4
, u
, v
;
35 len
= (m
[0] + 31) >> 5;
36 len4
= len
& ~(size_t)3;
39 for (u
= 0; u
< len
; u
++) {
44 f
= MUL31_lo((d
[1] + MUL31_lo(x
[u
+ 1], y
[1])), m0i
);
47 for (v
= 0; v
< len4
; v
+= 4) {
50 z
= (uint64_t)d
[v
+ 1] + MUL31(xu
, y
[v
+ 1])
51 + MUL31(f
, m
[v
+ 1]) + r
;
53 d
[v
+ 0] = (uint32_t)z
& 0x7FFFFFFF;
54 z
= (uint64_t)d
[v
+ 2] + MUL31(xu
, y
[v
+ 2])
55 + MUL31(f
, m
[v
+ 2]) + r
;
57 d
[v
+ 1] = (uint32_t)z
& 0x7FFFFFFF;
58 z
= (uint64_t)d
[v
+ 3] + MUL31(xu
, y
[v
+ 3])
59 + MUL31(f
, m
[v
+ 3]) + r
;
61 d
[v
+ 2] = (uint32_t)z
& 0x7FFFFFFF;
62 z
= (uint64_t)d
[v
+ 4] + MUL31(xu
, y
[v
+ 4])
63 + MUL31(f
, m
[v
+ 4]) + r
;
65 d
[v
+ 3] = (uint32_t)z
& 0x7FFFFFFF;
67 for (; v
< len
; v
++) {
70 z
= (uint64_t)d
[v
+ 1] + MUL31(xu
, y
[v
+ 1])
71 + MUL31(f
, m
[v
+ 1]) + r
;
73 d
[v
] = (uint32_t)z
& 0x7FFFFFFF;
77 d
[len
] = (uint32_t)zh
& 0x7FFFFFFF;
82 * We must write back the bit length because it was overwritten in
83 * the loop (not overwriting it would require a test in the loop,
84 * which would yield bigger and slower code).
89 * d[] may still be greater than m[] at that point; notably, the
90 * 'dh' word may be non-zero.
92 br_i31_sub(d
, m
, NEQ(dh
, 0) | NOT(br_i31_sub(d
, m
, 0)));