1/* ===-- udivsi3.c - Implement __udivsi3 -----------------------------------===
2 *
3 *                     The LLVM Compiler Infrastructure
4 *
5 * This file is dual licensed under the MIT and the University of Illinois Open
6 * Source Licenses. See LICENSE.TXT for details.
7 *
8 * ===----------------------------------------------------------------------===
9 *
10 * This file implements __udivsi3 for the compiler_rt library.
11 *
12 * ===----------------------------------------------------------------------===
13 */
14
15#include "int_lib.h"
16
17/* Returns: a / b */
18
19/* Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide */
20
21ARM_EABI_FNALIAS(uidiv, udivsi3)
22
23/* This function should not call __divsi3! */
24COMPILER_RT_ABI su_int
25__udivsi3(su_int n, su_int d)
26{
27    const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT;
28    su_int q;
29    su_int r;
30    unsigned sr;
31    /* special cases */
32    if (d == 0)
33        return 0; /* ?! */
34    if (n == 0)
35        return 0;
36    sr = __builtin_clz(d) - __builtin_clz(n);
37    /* 0 <= sr <= n_uword_bits - 1 or sr large */
38    if (sr > n_uword_bits - 1)  /* d > r */
39        return 0;
40    if (sr == n_uword_bits - 1)  /* d == 1 */
41        return n;
42    ++sr;
43    /* 1 <= sr <= n_uword_bits - 1 */
44    /* Not a special case */
45    q = n << (n_uword_bits - sr);
46    r = n >> sr;
47    su_int carry = 0;
48    for (; sr > 0; --sr)
49    {
50        /* r:q = ((r:q)  << 1) | carry */
51        r = (r << 1) | (q >> (n_uword_bits - 1));
52        q = (q << 1) | carry;
53        /* carry = 0;
54         * if (r.all >= d.all)
55         * {
56         *      r.all -= d.all;
57         *      carry = 1;
58         * }
59         */
60        const si_int s = (si_int)(d - r - 1) >> (n_uword_bits - 1);
61        carry = s & 1;
62        r -= d & s;
63    }
64    q = (q << 1) | carry;
65    return q;
66}
67