87 lines
2.0 KiB
C
Executable File
87 lines
2.0 KiB
C
Executable File
/*
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This program is part of the TACLeBench benchmark suite.
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Version V 1.x
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Name: bitcnt_4.c
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Author: Bob Stout
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Function: Recursive bit counting functions using table lookup
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Source: http://www.snippets.org/
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Changes: no major functional changes
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License: May be used, modified, and re-distributed freely.
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*/
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#include "bitops.h" /* from Snippets */
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static char bitcount_bits[ 256 ];
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/*
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** Count bits in each nybble
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**
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** Note: Only the first 16 table entries are used, the rest could be
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** omitted.
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*/
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void bitcount_init4( void )
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{
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int volatile i = 0;
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char bitcount_bits_tmp[ 256 ] = {
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0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
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};
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for ( i = 0; i < 256; i++ )
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bitcount_bits[ i ] = bitcount_bits_tmp[ i ];
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}
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int bitcount_ntbl_bitcnt( unsigned long x )
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{
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int cnt = bitcount_bits[ ( int )( x & 0x0000000FL ) ];
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if ( 0L != ( x >>= 4 ) )
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cnt += bitcount_ntbl_bitcnt( x );
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return cnt;
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}
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/*
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** Count bits in each byte
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*/
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int bitcount_btbl_bitcnt( unsigned long x )
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{
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#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
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int idx = sizeof(x) - 1;
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#else
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int idx = 0;
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#endif
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int cnt = bitcount_bits[( ( char * ) & x )[idx] & 0xFF];
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if ( 0L != ( x >>= 8 ) )
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cnt += bitcount_btbl_bitcnt( x );
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return cnt;
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}
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