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/cvs/libecb/ecb.h
Revision: 1.1
Committed: Thu May 26 16:41:12 2011 UTC (13 years, 1 month ago) by root
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Branch: MAIN
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# Content
1 /*
2 * libecb
3 *
4 * Copyright (c) 2011 Marc Alexander Lehmann
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without modifica-
8 * tion, are permitted provided that the following conditions are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright notice,
11 * this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26 * OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #ifndef ECB_H
30 #define ECB_H
31
32 #define ECB_GCC_VERSION(major,minor) (__GNUC__ > (major) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor)))
33
34 #if ECB_GCC_VERSION(3,1)
35 # define ecb_attribute(attrlist) __attribute__(attrlist)
36 # define ecb_is_constant(c) __builtin_constant_p (c)
37 # define ecb_expect(expr,value) __builtin_expect ((expr),(value))
38 # define ecb_prefetch(addr,rw,locality) __builtin_prefetch (addr, rw, locality)
39 #else
40 # define ecb_attribute(attrlist)
41 # define ecb_is_constant(c) 0
42 # define ecb_expect(expr,value) (expr)
43 # define ecb_prefetch(addr,rw,locality)
44 #endif
45
46 #if ECB_GCC_VERSION(4,5)
47 # define ecb_decltype(x) __decltype(x)
48 #elif ECB_GCC_VERSION(3,0)
49 # define ecb_decltype(x) typeof(x)
50 #endif
51
52 #define ecb_noinline ecb_attribute ((noinline))
53 #define ecb_noreturn ecb_attribute ((noreturn))
54 #define ecb_unused ecb_attribute ((unused))
55 #define ecb_const ecb_attribute ((const))
56 #define ecb_pure ecb_attribute ((pure))
57 #define ecb_hot ecb_attribute ((hot)) // 4.3
58 #define ecb_cold ecb_attribute ((cold)) // 4.3
59
60 #if ECB_GCC_VERSION(4,5)
61 # define ecb_unreachable() __builtin_unreachable ()
62 #else
63 // this seems to work fine, but gcc always emits a warning for it :/
64 static inline void ecb_unreachable () ecb_attribute ((noreturn));
65 static inline void ecb_unreachable () { }
66 #endif
67
68 // put into ifs if you are very sure that the expression
69 // is mostly true or mosty false. note that these return
70 // booleans, not the expression.
71 #define ecb_expect_false(expr) ecb_expect ((expr) ? 1 : 0, 0)
72 #define ecb_expect_true(expr) ecb_expect ((expr) ? 1 : 0, 1)
73
74 // try to tell the compiler that some condition is definitely true
75 #define ecb_assume(cond) do { if (!(cond)) unreachable (); } while (0)
76
77 // count trailing zero bits and count # of one bits
78 #if ECB_GCC_VERSION(3,4)
79 static inline int ecb_ctz (unsigned int x) { return __builtin_ctz (x); }
80 static inline int ecb_popcount (unsigned int x) { return __builtin_popcount (x); }
81 #else
82 static int ecb_ctz (unsigned int x) ecb_const
83 {
84 int r = 0;
85
86 x &= -x; // this isolates the lowest bit
87
88 if (x & 0xaaaaaaaa) r += 1;
89 if (x & 0xcccccccc) r += 2;
90 if (x & 0xf0f0f0f0) r += 4;
91 if (x & 0xff00ff00) r += 8;
92 if (x & 0xffff0000) r += 16;
93
94 return r;
95 }
96
97 static int ecb_popcount (unsigned int x) ecb_const
98 {
99 x -= (x >> 1) & 0x55555555;
100 x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
101 x = ((x >> 4) + x) & 0x0f0f0f0f;
102 x *= 0x01010101;
103
104 return x >> 24;
105 }
106 #endif
107
108 #endif
109