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clib/libmpeg2/motion_comp_mmx.c  view on Meta::CPAN

#include "mmx.h"

#define CPU_MMXEXT 0
#define CPU_3DNOW 1


/* MMX code - needs a rewrite */

/*
 * Motion Compensation frequently needs to average values using the
 * formula (x+y+1)>>1. Both MMXEXT and 3Dnow include one instruction
 * to compute this, but it's been left out of classic MMX.
 *
 * We need to be careful of overflows when doing this computation.
 * Rather than unpacking data to 16-bits, which reduces parallelism,
 * we use the following formulas:
 *
 * (x+y)>>1 == (x&y)+((x^y)>>1)
 * (x+y+1)>>1 == (x|y)-((x^y)>>1)
 */

/* some rounding constants */
static mmx_t mask1 = {0xfefefefefefefefeLL};
static mmx_t round4 = {0x0002000200020002LL};

/*

clib/libmpeg2/motion_comp_vis.c  view on Meta::CPAN

#ifdef ARCH_SPARC

#include <inttypes.h>

#include "mpeg2.h"
#include "attributes.h"
#include "mpeg2_internal.h"
#include "vis.h"

/* The trick used in some of this file is the formula from the MMX
 * motion comp code, which is:
 *
 * (x+y+1)>>1 == (x|y)-((x^y)>>1)
 *
 * This allows us to average 8 bytes at a time in a 64-bit FPU reg.
 * We avoid overflows by masking before we do the shift, and we
 * implement the shift by multiplying by 1/2 using mul8x16.  So in
 * VIS this is (assume 'x' is in f0, 'y' is in f2, a repeating mask
 * of '0xfe' is in f4, a repeating mask of '0x7f' is in f6, and
 * the value 0x80808080 is in f8):