ARM Neon 列子 - Vector Add

///
// ARM Neon

/*
 * FIR 滤波器
  * 　　        y(n)=h(0)x(n) + h(1)x(n-1) + h(2)x(n-2) + ... h(N-1)x(n-N-1)
 *
 */
void TaskManger::fir_filter_c(short * y, const short *x, const short *h, int n_out, int n_coefs)
{
  int n;
  for (n = 0; n < n_out; n++)
  {
    int k, sum = 0;
    for(k = 0; k < n_coefs; k++)
    {
      sum += h[k] * x[n - n_coefs + 1 + k];
    }
    y[n] = ((sum>>15) + 1) >> 1;
  }
}

void fir_filter_neon(short * y, const short *x, const short *h, int n_out, int n_coefs)
{
  int n, k;
  int sum;
  int16x4_t h_vec;
  int16x4_t x_vec;
  int32x4_t result_vec;
  for (n = 0; n < n_out; n++)
  {
    /* Clear the scalar and vector sums */
    sum = 0;
    result_vec = vdupq_n_s32(0);      /* vdup -> duplicates a scalar into every element of the destination vector */
    for(k = 0; k < n_coefs / 4; k++)
    {
      /* Four vector multiply-accumulate operations in parallel */
      h_vec = vld1_s16(&h[k*4]);
      x_vec = vld1_s16(&x[n - n_coefs + 1 + k*4]);
      result_vec = vmlal_s16(result_vec, h_vec, x_vec);
    }

    /* Reduction operation - add each vector lane result to the sum */
    sum += vgetq_lane_s32(result_vec, 0);
    sum += vgetq_lane_s32(result_vec, 1);
    sum += vgetq_lane_s32(result_vec, 2);
    sum += vgetq_lane_s32(result_vec, 3);

    /* consume the last few data using scalar operations */
    if(n_coefs % 4)
    {
      for(k = n_coefs - (n_coefs % 4); k < n_coefs; k++)
      sum += h[k] * x[n - n_coefs + 1 + k];
    }
    /* Store the adjusted result */
    y[n] = ((sum>>15) + 1) >> 1;
  }
}

/*
 * RGB转灰度图像
 */

void reference_convert (uint8_t * __restrict dest, uint8_t * __restrict src, int n)
{
  int i;
  for (i=0; i<n; i++)
  {
    int r = *src++; // load red
    int g = *src++; // load green
    int b = *src++; // load blue

    // build weighted average:
    int y = (r*77)+(g*151)+(b*28);

    // undo the scale by 256 and write to memory:
    *dest++ = (y>>8);
  }
}

void neon_convert (uint8_t * __restrict dest, uint8_t * __restrict src, int n)
{
  int i;
  uint8x8_t rfac = vdup_n_u8 (77);
  uint8x8_t gfac = vdup_n_u8 (151);
  uint8x8_t bfac = vdup_n_u8 (28);

  n /= 8;
  for (i=0; i<n; i++)
  {
    uint16x8_t  temp;
    uint8x8x3_t rgb  = vld3_u8 (src);            // vld3 ->loads 3 vectors from memory. 就是 uint8x8_t val[3]
    uint8x8_t result;

    temp = vmull_u8 (rgb.val[0],      rfac);     // 长指令相乘
    temp = vmlal_u8 (temp,rgb.val[1], gfac);
    temp = vmlal_u8 (temp,rgb.val[2], bfac);

    result = vshrn_n_u16 (temp, 8);              // vshrn -> ri = ai >> b; 移位指针
    vst1_u8 (dest, result);                      // vst1 -> stores a vector into memory
    src  += 8*3;
    dest += 8;
  }
}

/*
 * Vector add 
 */

uint32_t TaskManger::vector_add_c(uint32_t *s, uint32_t n)
{// assert n % 4 == 0

  uint32_t sum = 0;
  for(uint32_t i = 0; i < n; i++)
    sum += *s++;
  return sum;
}

uint32_t TaskManger::vector_add_neon(uint32_t *s, uint32_t n)
{// assert n % 4 == 0

  uint32_t sum, *i;
  uint32x2_t vec64a, vec64b;
  uint32x4_t vec128 = vdupq_n_u32(0);
  for (i = s; i < (s + n); i += 4)
  {
    uint32x4_t temp128 = vld1q_u32(i);            // 从内存加载一个向量vector, vld1 -> loads a vector from memory
    vec128 = vaddq_u32(vec128, temp128);          // 向量相加uint32x4_t相加，一次加4个uint32_t,  vector add, vadd -> ri = ai + bi
  }

  vec64a = vget_low_u32(vec128);                    // returns the lower half of the 128-bit input vector.
  vec64b = vget_high_u32(vec128);                   // returns the higher half of the 128-bit input vector.

  vec64a = vadd_u32 (vec64a, vec64b);               // 再将     uint32x2_t 向量相加

  sum =  vget_lane_u32(vec64a, 0);                  // returns the value from the specified lane of a vector.
  sum += vget_lane_u32(vec64a, 1);
  return sum;
}

void TaskManger::neon_demo()
{
  //1, demo 1
#define ELE  65536

  uint32_t arry[ELE];
    struct timeval tpstart,tpend;
    float timeuse;

    printf("run neon demo 1, vector add\n");

    srand((unsigned int) time(NULL));
  for(int i = 0; i < ELE; i++)
  {
    arry[i] = rand() % 500;
  }

    // c/c++
    gettimeofday(&tpstart,NULL);
  uint32_t result2 = vector_add_c(arry, ARRAY_SIZE(arry));
    gettimeofday(&tpend,NULL);

    timeuse = 1000000*(tpend.tv_sec-tpstart.tv_sec)+ tpend.tv_usec-tpstart.tv_usec;

    printf("generator loop c add result:%d, used time:%f ms\n\n\n", result2, timeuse);

  // neon
    gettimeofday(&tpstart,NULL);
  uint32_t result1 = vector_add_neon(arry, ARRAY_SIZE(arry));
    gettimeofday(&tpend,NULL);

    timeuse = 1000000*(tpend.tv_sec-tpstart.tv_sec)+ tpend.tv_usec-tpstart.tv_usec;

    printf("neon vector add result:%d, used time:%f ms\n\n\n", result1, timeuse);
}