107 lines
2.7 KiB
C
Executable File
107 lines
2.7 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_3.c
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Author: Bob Stout & Auke Reitsma
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Function: 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"
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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_init3( 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_bitcount( long int x )
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{
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return
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bitcount_bits[ ( int ) ( x & 0x0000000FUL ) ] +
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bitcount_bits[ ( int )( ( x & 0x000000F0UL ) >> 4 ) ] +
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bitcount_bits[ ( int )( ( x & 0x00000F00UL ) >> 8 ) ] +
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bitcount_bits[ ( int )( ( x & 0x0000F000UL ) >> 12 ) ] +
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bitcount_bits[ ( int )( ( x & 0x000F0000UL ) >> 16 ) ] +
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bitcount_bits[ ( int )( ( x & 0x00F00000UL ) >> 20 ) ] +
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bitcount_bits[ ( int )( ( x & 0x0F000000UL ) >> 24 ) ] +
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bitcount_bits[ ( int )( ( x & 0xF0000000UL ) >> 28 ) ];
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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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** by Bruce Wedding, works best on Watcom & Borland
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*/
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int bitcount_BW_btbl_bitcount( long int x )
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{
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union {
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unsigned char ch[ 4 ];
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long y;
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} U;
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U.y = x;
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return bitcount_bits[ U.ch[ 0 ] ] + bitcount_bits[ U.ch[ 1 ] ] +
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bitcount_bits[ U.ch[ 3 ] ] + bitcount_bits[ U.ch[ 2 ] ];
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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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** by Auke Reitsma, works best on Microsoft, Symantec, and others
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*/
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int bitcount_AR_btbl_bitcount( long int x )
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{
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unsigned char *ptr = ( unsigned char * ) & x ;
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int accu ;
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accu = bitcount_bits[ *ptr++ ];
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accu += bitcount_bits[ *ptr++ ];
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accu += bitcount_bits[ *ptr++ ];
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accu += bitcount_bits[ *ptr ];
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return accu;
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}
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