void HalfFloat1Row_NEON(const uint16* src, uint16* dst, float, int width) {
  asm volatile (
  "1:                                          \n"
    MEMACCESS(0)
    "ld1        {v1.16b}, [%0], #16            \n"  // load 8 shorts
    "subs       %w2, %w2, #8                   \n"  // 8 pixels per loop
    "uxtl       v2.4s, v1.4h                   \n"  // 8 int's
    "uxtl2      v1.4s, v1.8h                   \n"
    "scvtf      v2.4s, v2.4s                   \n"  // 8 floats
    "scvtf      v1.4s, v1.4s                   \n"
    "fcvtn      v4.4h, v2.4s                   \n"  // 8 floatsgit
    "fcvtn2     v4.8h, v1.4s                   \n"
   MEMACCESS(1)
    "st1        {v4.16b}, [%1], #16            \n"  // store 8 shorts
    "b.gt       1b                             \n"
  : "+r"(src),    // %0
    "+r"(dst),    // %1
    "+r"(width)   // %2
  :
  : "cc", "memory", "v1", "v2", "v4"
  );
}

void HalfFloatRow_NEON(const uint16* src, uint16* dst, float scale, int width) {
  asm volatile (
  "1:                                          \n"
    MEMACCESS(0)
    "ld1        {v1.16b}, [%0], #16            \n"  // load 8 shorts
    "subs       %w2, %w2, #8                   \n"  // 8 pixels per loop
    "uxtl       v2.4s, v1.4h                   \n"  // 8 int's
    "uxtl2      v1.4s, v1.8h                   \n"
    "scvtf      v2.4s, v2.4s                   \n"  // 8 floats
    "scvtf      v1.4s, v1.4s                   \n"
    "fmul       v2.4s, v2.4s, %3.s[0]          \n"  // adjust exponent
    "fmul       v1.4s, v1.4s, %3.s[0]          \n"
    "uqshrn     v4.4h, v2.4s, #13              \n"  // isolate halffloat
    "uqshrn2    v4.8h, v1.4s, #13              \n"
   MEMACCESS(1)
    "st1        {v4.16b}, [%1], #16            \n"  // store 8 shorts
    "b.gt       1b                             \n"
  : "+r"(src),    // %0
    "+r"(dst),    // %1
    "+r"(width)   // %2
  : "w"(scale * 1.9259299444e-34f)    // %3
  : "cc", "memory", "v1", "v2", "v4"
  );
}

TEST=LibYUVPlanarTest.TestHalfFloatPlane_One
BUG=libyuv:560
R=hubbe@chromium.org

Review URL: https://codereview.chromium.org/2430313008 .