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feeeff5c JR |
1 | /* Generic unsigned 32 bit division implementation. |
2 | Copyright (C) 2009, 2011 Free Software Foundation, Inc. | |
3 | Contributed by Embecosm on behalf of Adapteva, Inc. | |
4 | ||
5 | This file is part of GCC. | |
6 | ||
7 | This file is free software; you can redistribute it and/or modify it | |
8 | under the terms of the GNU General Public License as published by the | |
9 | Free Software Foundation; either version 3, or (at your option) any | |
10 | later version. | |
11 | ||
12 | This file is distributed in the hope that it will be useful, but | |
13 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | General Public License for more details. | |
16 | ||
17 | Under Section 7 of GPL version 3, you are granted additional | |
18 | permissions described in the GCC Runtime Library Exception, version | |
19 | 3.1, as published by the Free Software Foundation. | |
20 | ||
21 | You should have received a copy of the GNU General Public License and | |
22 | a copy of the GCC Runtime Library Exception along with this program; | |
23 | see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
24 | <http://www.gnu.org/licenses/>. */ | |
25 | ||
26 | typedef union { unsigned int i; float f; } fu; | |
27 | ||
28 | unsigned int __udivsi3 (unsigned int a, unsigned int b); | |
29 | ||
30 | unsigned int | |
31 | __udivsi3 (unsigned int a, unsigned int b) | |
32 | { | |
33 | unsigned int d, t, s0, s1, s2, r0, r1; | |
34 | fu u0, u1, u2, u1b, u2b; | |
35 | ||
36 | if (b > a) | |
37 | return 0; | |
38 | if ((int) b < 0) | |
39 | return 1; | |
40 | ||
41 | /* Assuming B is nonzero, compute S0 such that 0 <= S0, | |
42 | (B << S0+1) does not overflow, | |
43 | A < 4.01 * (B << S0), with S0 choosen as small as possible | |
44 | without taking to much time calculating. */ | |
45 | #ifdef CONVERT_UNSIGNED | |
46 | u0.f = a; | |
47 | u1.f = b; | |
48 | #else /* !CONVERT_UNSIGNED */ | |
49 | u0.f = (int) a; | |
50 | u1.f = (int) b; | |
51 | #ifdef CONCISE | |
52 | if (a < 0) | |
53 | u0.i = (a >> 8) - 0x00800000 + 0x3f800000 + (31 << 23); | |
54 | #else /* To use flag seting / cmove, this can be written as: */ | |
55 | { | |
56 | unsigned c = 0xff800000 - 0x4f000000; | |
57 | t = (int)a >> 8; | |
58 | if (t >= c) | |
59 | u0.i = (t - c); | |
60 | } | |
61 | #endif | |
62 | #endif /* !CONVERT_UNSIGNED */ | |
63 | s0 = u0.i + 1 /* Compensate for rounding errors. */ | |
64 | - 0x00800000 /* adjust by one */ ; | |
65 | s0 = s0 - u1.i; | |
66 | s0 = (int)s0 >= 0 ? s0 : 0; | |
67 | s0 >>= 23; | |
68 | ||
69 | b <<= s0; | |
70 | r1 = 0; | |
71 | ||
72 | r0 = 1 << s0; | |
73 | a = ((t=a) - b); | |
74 | if (a <= t) | |
75 | { | |
76 | r1 += r0; | |
77 | a = ((t=a) - b); | |
78 | if (a <= t) | |
79 | do { | |
80 | r1 += r0; | |
81 | a = ((t=a) - b); | |
82 | } while (a <= t); | |
83 | } | |
84 | a += b; | |
85 | d = b - 1; | |
86 | ||
87 | #define STEP(n) case n: a += a; t = a - d; if (t <= a) a = t; | |
88 | switch (s0) | |
89 | { | |
90 | STEP (31) | |
91 | STEP (30) | |
92 | STEP (29) | |
93 | STEP (28) | |
94 | STEP (27) | |
95 | STEP (26) | |
96 | STEP (25) | |
97 | STEP (24) | |
98 | STEP (23) | |
99 | STEP (22) | |
100 | STEP (21) | |
101 | STEP (20) | |
102 | STEP (19) | |
103 | STEP (18) | |
104 | STEP (17) | |
105 | STEP (16) | |
106 | STEP (15) | |
107 | STEP (14) | |
108 | STEP (13) | |
109 | STEP (12) | |
110 | STEP (11) | |
111 | STEP (10) | |
112 | STEP (9) | |
113 | STEP (8) | |
114 | STEP (7) | |
115 | STEP (6) | |
116 | STEP (5) | |
117 | STEP (4) | |
118 | STEP (3) | |
119 | STEP (2) | |
120 | STEP (1) | |
121 | case 0: ; | |
122 | } | |
123 | r0 = r1 | (r0-1 & a); | |
124 | return r0; | |
125 | } |