#include <stdio.h>
#include <stdint.h>
#include <float.h>
#include <sys/time.h>

/* VSX/Altivec registers (128 bits) */
typedef union _ppc_vsr_t {
    uint8_t u8[16];
    uint16_t u16[8];
    uint32_t u32[4];
    uint64_t u64[2];
    int8_t s8[16];
    int16_t s16[8];
    int32_t s32[4];
    int64_t s64[2];
    float f32[4];
    double f64[2];
} ppc_vsr_t;

typedef ppc_vsr_t ppc_avr_t;

#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
#define IS_LITTLE_ENDIAN (1 == *(unsigned char *)&(const int){1})

#if defined(IS_LITTLE_ENDIAN)
#define HI_IDX 1
#define LO_IDX 0
#define VsrB(i) u8[15 - (i)]
#else
#define HI_IDX 0
#define LO_IDX 1
#define VsrB(i) u8[i]
#endif

#define ITERATIONS 0x8000000

void benchmark1(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)
{
    /* Existing algorithm */
    ppc_avr_t result;
    int i;
    size_t n_elems = ARRAY_SIZE(r->u8);

    for (i = 0; i < n_elems / 2; i++) {
        result.u8[i*2+HI_IDX] = a->u8[i];
        result.u8[i*2+LO_IDX] = b->u8[i];
    }
    *r = result;    
}

void benchmark2(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)
{
    /* v3 patchset algorithm */
    ppc_avr_t result;
    int i;

    for (i = 0; i < ARRAY_SIZE(r->u8); i++) {
        result.VsrB(i) = (i & 1) ? b->VsrB(i >> 1)
                                 : a->VsrB(i >> 1);
    }
    *r = result;
}

void benchmark3(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)
{
    /* Split loop into 2 halves */
    ppc_avr_t result;
    int i;

    for (i = 0; i < ARRAY_SIZE(r->u8); i+=2) {
        result.VsrB(i) = a->VsrB(i >> 1);
    }

    for (i = 1; i < ARRAY_SIZE(r->u8); i+=2) {
        result.VsrB(i) = b->VsrB(i >> 1);
    }
    *r = result;
}

void benchmark4(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)
{
    /* Richard's merge high */
    ppc_avr_t result;    
    int i;
    int half = ARRAY_SIZE(r->u8) / 2;
    int ofs = 0;

    for (i = 0; i < half; i++) {
        result.VsrB(i * 2 + 0) = a->VsrB(i + ofs);
        result.VsrB(i * 2 + 1) = b->VsrB(i + ofs);
    }
    *r = result;
}

int elapsed_time(struct timeval *st, struct timeval *et)
{
    return ((et->tv_sec - st->tv_sec) * 1000000) + (et->tv_usec - st->tv_usec);    
}

int main(int argc, char *argv[]) 
{
    ppc_avr_t a, b, r;
    int i;
    struct timeval start_time, end_time;

    printf("Benchmark 1 - existing merge high\n");
    gettimeofday(&start_time, NULL);

    for (i = 0; i < ITERATIONS; i++) {
        benchmark1(&r, &a, &b);
    }
    
    gettimeofday(&end_time ,NULL);
    printf("Elapsed time: %d us\n\n", elapsed_time(&start_time, &end_time));
    

    printf("Benchmark 2 - v3 merge high\n");
    gettimeofday(&start_time, NULL);

    for (i = 0; i < ITERATIONS; i++) {
        benchmark2(&r, &a, &b);
    }
    
    gettimeofday(&end_time ,NULL);
    printf("Elapsed time: %d us\n\n", elapsed_time(&start_time, &end_time));
    

    printf("Benchmark 3 - 2 loops merge high\n");
    gettimeofday(&start_time, NULL);

    for (i = 0; i < ITERATIONS; i++) {
        benchmark3(&r, &a, &b);
    }

    gettimeofday(&end_time ,NULL);
    printf("Elapsed time: %d us\n\n", elapsed_time(&start_time, &end_time));


    printf("Benchmark 4 - Richard's merge high\n");
    gettimeofday(&start_time, NULL);

    for (i = 0; i < ITERATIONS; i++) {
        benchmark4(&r, &a, &b);
    }
    
    gettimeofday(&end_time ,NULL);
    printf("Elapsed time: %d us\n\n", elapsed_time(&start_time, &end_time));
}