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53 lines
1.0 KiB
53 lines
1.0 KiB
/*
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* UCW Library -- Bit Operations
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*
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* (c) 2005 Martin Mares <mj@ucw.cz>
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* (c) 2012 Pavel Charvat <pchar@ucw.cz>
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*
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* This software may be freely distributed and used according to the terms
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* of the GNU Lesser General Public License.
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*/
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#ifndef _UCW_BITOPS_H
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#define _UCW_BITOPS_H
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#ifdef CONFIG_UCW_CLEAN_ABI
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#define bit_fls ucw_bit_fls
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#define ffs_table ucw_ffs_table
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#endif
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/* Find highest bit set (i.e., the floor of the binary logarithm) (bit-fls.c) */
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int bit_fls(u32 x); /* bit_fls(0)=-1 */
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/* Find lowest bit set, undefined for zero argument (bit-ffs.c) */
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extern const byte ffs_table[256];
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#ifdef __pentium4 /* On other ia32 machines, the C version is faster */
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static inline uint bit_ffs(uint w)
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{
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asm("bsfl %1,%0" :"=r" (w) :"rm" (w));
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return w;
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}
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#else
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static inline uint bit_ffs(uint w)
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{
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uint b = (w & 0xffff) ? 0 : 16;
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b += ((w >> b) & 0xff) ? 0 : 8;
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return b + ffs_table[(w >> b) & 0xff];
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}
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#endif
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/* Count the number of bits set */
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static inline uint bit_count(uint w)
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{
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return __builtin_popcount(w);
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}
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#endif
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