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 | |
21 | ARM_EABI_FNALIAS(uidiv, udivsi3) |
22 | |
23 | /* This function should not call __divsi3! */ |
24 | COMPILER_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 | |