Zephyr API Documentation  3.0.0
A Scalable Open Source RTOS
3.0.0
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ilog2.h
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1/*
2 * Copyright (c) 2021 Intel Corporation
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7#include <stdint.h>
8
9#include <toolchain.h>
10#include <arch/common/ffs.h>
11#include <sys/util.h>
12
36#define ilog2_compile_time_const_u32(n) \
37 ( \
38 (n < 2) ? 0 : \
39 ((n & BIT(31)) == BIT(31)) ? 31 : \
40 ((n & BIT(30)) == BIT(30)) ? 30 : \
41 ((n & BIT(29)) == BIT(29)) ? 29 : \
42 ((n & BIT(28)) == BIT(28)) ? 28 : \
43 ((n & BIT(27)) == BIT(27)) ? 27 : \
44 ((n & BIT(26)) == BIT(26)) ? 26 : \
45 ((n & BIT(25)) == BIT(25)) ? 25 : \
46 ((n & BIT(24)) == BIT(24)) ? 24 : \
47 ((n & BIT(23)) == BIT(23)) ? 23 : \
48 ((n & BIT(22)) == BIT(22)) ? 22 : \
49 ((n & BIT(21)) == BIT(21)) ? 21 : \
50 ((n & BIT(20)) == BIT(20)) ? 20 : \
51 ((n & BIT(19)) == BIT(19)) ? 19 : \
52 ((n & BIT(18)) == BIT(18)) ? 18 : \
53 ((n & BIT(17)) == BIT(17)) ? 17 : \
54 ((n & BIT(16)) == BIT(16)) ? 16 : \
55 ((n & BIT(15)) == BIT(15)) ? 15 : \
56 ((n & BIT(14)) == BIT(14)) ? 14 : \
57 ((n & BIT(13)) == BIT(13)) ? 13 : \
58 ((n & BIT(12)) == BIT(12)) ? 12 : \
59 ((n & BIT(11)) == BIT(11)) ? 11 : \
60 ((n & BIT(10)) == BIT(10)) ? 10 : \
61 ((n & BIT(9)) == BIT(9)) ? 9 : \
62 ((n & BIT(8)) == BIT(8)) ? 8 : \
63 ((n & BIT(7)) == BIT(7)) ? 7 : \
64 ((n & BIT(6)) == BIT(6)) ? 6 : \
65 ((n & BIT(5)) == BIT(5)) ? 5 : \
66 ((n & BIT(4)) == BIT(4)) ? 4 : \
67 ((n & BIT(3)) == BIT(3)) ? 3 : \
68 ((n & BIT(2)) == BIT(2)) ? 2 : \
69 1 \
70 )
71
84/*
85 * This is in #define form as this needs to also work on
86 * compile time constants. Doing this as a static inline
87 * function will result in compiler complaining with
88 * "initializer element is not constant".
89 */
90#define ilog2(n) \
91 ( \
92 __builtin_constant_p(n) ? \
93 ilog2_compile_time_const_u32(n) : \
94 find_msb_set(n) - 1 \
95 )
toolchain.h
Macros to abstract toolchain specific capabilities.
util.h
Misc utilities.