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Diffstat (limited to 'contrib/syslinux/latest/com32/include/ilog2.h')
-rw-r--r-- | contrib/syslinux/latest/com32/include/ilog2.h | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/contrib/syslinux/latest/com32/include/ilog2.h b/contrib/syslinux/latest/com32/include/ilog2.h new file mode 100644 index 0000000..91a5057 --- /dev/null +++ b/contrib/syslinux/latest/com32/include/ilog2.h @@ -0,0 +1,48 @@ +/* ----------------------------------------------------------------------- * + * + * Copyright 2010 Intel Corporation; author: H. Peter Anvin + * + * Permission is hereby granted, free of charge, to any person + * obtaining a copy of this software and associated documentation + * files (the "Software"), to deal in the Software without + * restriction, including without limitation the rights to use, + * copy, modify, merge, publish, distribute, sublicense, and/or + * sell copies of the Software, and to permit persons to whom + * the Software is furnished to do so, subject to the following + * conditions: + * + * The above copyright notice and this permission notice shall + * be included in all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES + * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT + * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, + * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR + * OTHER DEALINGS IN THE SOFTWARE. + * + * ----------------------------------------------------------------------- */ + +#ifndef _ILOG2_H +#define _ILOG2_H + +/* + * Computes floor(log2(x)) -- undefined for x = 0. + */ + +#include <klibc/compiler.h> +#include <stdint.h> + +static inline __constfunc uint32_t ilog2(uint32_t __v) +{ +# if __GNUC__ >= 4 + return __builtin_clz(__v) ^ 31; +# else + asm("bsrl %1,%0" : "=r" (__v) : "rm" (__v)); + return __v; +# endif +} + +#endif /* _ILOG2_H */ |