xref: /freebsd/contrib/bearssl/src/int/i32_div32.c (revision dd41de95a84d979615a2ef11df6850622bf6184e)
1 /*
2  * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
3  *
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:
11  *
12  * The above copyright notice and this permission notice shall be
13  * included in all copies or substantial portions of the Software.
14  *
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
22  * SOFTWARE.
23  */
24 
25 #include "inner.h"
26 
27 /* see inner.h */
28 uint32_t
29 br_divrem(uint32_t hi, uint32_t lo, uint32_t d, uint32_t *r)
30 {
31 	/* TODO: optimize this */
32 	uint32_t q;
33 	uint32_t ch, cf;
34 	int k;
35 
36 	q = 0;
37 	ch = EQ(hi, d);
38 	hi = MUX(ch, 0, hi);
39 	for (k = 31; k > 0; k --) {
40 		int j;
41 		uint32_t w, ctl, hi2, lo2;
42 
43 		j = 32 - k;
44 		w = (hi << j) | (lo >> k);
45 		ctl = GE(w, d) | (hi >> k);
46 		hi2 = (w - d) >> j;
47 		lo2 = lo - (d << k);
48 		hi = MUX(ctl, hi2, hi);
49 		lo = MUX(ctl, lo2, lo);
50 		q |= ctl << k;
51 	}
52 	cf = GE(lo, d) | hi;
53 	q |= cf;
54 	*r = MUX(cf, lo - d, lo);
55 	return q;
56 }
57