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/* |
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* libecb |
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* |
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* Copyright (©) 2009-2011 Marc Alexander Lehmann |
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* All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without modifica- |
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* tion, are permitted provided that the following conditions are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright notice, |
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* this list of conditions and the following disclaimer. |
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* |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in the |
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* documentation and/or other materials provided with the distribution. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER- |
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* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
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* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE- |
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* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH- |
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* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED |
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* OF THE POSSIBILITY OF SUCH DAMAGE. |
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*/ |
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#ifndef ECB_H |
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#define ECB_H |
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#define ECB_GCC_VERSION(major,minor) (__GNUC__ > (major) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor))) |
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#if ECB_GCC_VERSION(3,1) |
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# define ecb_attribute(attrlist) __attribute__(attrlist) |
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# define ecb_is_constant(c) __builtin_constant_p (c) |
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# define ecb_expect(expr,value) __builtin_expect ((expr),(value)) |
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# define ecb_prefetch(addr,rw,locality) __builtin_prefetch (addr, rw, locality) |
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#else |
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# define ecb_attribute(attrlist) |
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# define ecb_is_constant(c) 0 |
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# define ecb_expect(expr,value) (expr) |
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# define ecb_prefetch(addr,rw,locality) |
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#endif |
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/* no emulation for ecb_decltype */ |
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#if ECB_GCC_VERSION(4,5) |
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# define ecb_decltype(x) __decltype(x) |
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#elif ECB_GCC_VERSION(3,0) |
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# define ecb_decltype(x) typeof(x) |
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#endif |
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#define ecb_noinline ecb_attribute ((noinline)) |
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#define ecb_noreturn ecb_attribute ((noreturn)) |
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#define ecb_unused ecb_attribute ((unused)) |
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#define ecb_const ecb_attribute ((const)) |
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#define ecb_pure ecb_attribute ((pure)) |
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#define ecb_hot ecb_attribute ((hot)) // 4.3 |
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#define ecb_cold ecb_attribute ((cold)) // 4.3 |
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#if ECB_GCC_VERSION(4,5) |
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# define ecb_unreachable() __builtin_unreachable () |
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#else |
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// this seems to work fine, but gcc always emits a warning for it :/ |
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static inline void ecb_unreachable () ecb_attribute ((noreturn)); |
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static inline void ecb_unreachable () { } |
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#endif |
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// put into ifs if you are very sure that the expression |
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// is mostly true or mosty false. note that these return |
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// booleans, not the expression. |
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#define ecb_expect_false(expr) ecb_expect ((expr) ? 1 : 0, 0) |
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#define ecb_expect_true(expr) ecb_expect ((expr) ? 1 : 0, 1) |
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// try to tell the compiler that some condition is definitely true |
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#define ecb_assume(cond) do { if (!(cond)) unreachable (); } while (0) |
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// count trailing zero bits and count # of one bits |
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#if ECB_GCC_VERSION(3,4) |
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static inline int ecb_ctz (unsigned int x) { return __builtin_ctz (x); } |
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static inline int ecb_popcount (unsigned int x) { return __builtin_popcount (x); } |
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#else |
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static int ecb_ctz (unsigned int x) ecb_const |
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{ |
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int r = 0; |
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x &= -x; // this isolates the lowest bit |
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if (x & 0xaaaaaaaa) r += 1; |
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if (x & 0xcccccccc) r += 2; |
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if (x & 0xf0f0f0f0) r += 4; |
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if (x & 0xff00ff00) r += 8; |
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if (x & 0xffff0000) r += 16; |
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return r; |
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} |
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static int ecb_popcount (unsigned int x) ecb_const |
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{ |
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x -= (x >> 1) & 0x55555555; |
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x = ((x >> 2) & 0x33333333) + (x & 0x33333333); |
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x = ((x >> 4) + x) & 0x0f0f0f0f; |
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x *= 0x01010101; |
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return x >> 24; |
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} |
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#endif |
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#endif |
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