• Martin Storsjö's avatar
    arm: vp9: Add NEON optimizations of VP9 MC functions · 68caef9d
    Martin Storsjö authored
    This work is sponsored by, and copyright, Google.
    
    The filter coefficients are signed values, where the product of the
    multiplication with one individual filter coefficient doesn't
    overflow a 16 bit signed value (the largest filter coefficient is
    127). But when the products are accumulated, the resulting sum can
    overflow the 16 bit signed range. Instead of accumulating in 32 bit,
    we accumulate the largest product (either index 3 or 4) last with a
    saturated addition.
    
    (The VP8 MC asm does something similar, but slightly simpler, by
    accumulating each half of the filter separately. In the VP9 MC
    filters, each half of the filter can also overflow though, so the
    largest component has to be handled individually.)
    
    Examples of relative speedup compared to the C version, from checkasm:
                           Cortex      A7     A8     A9    A53
    vp9_avg4_neon:                   1.71   1.15   1.42   1.49
    vp9_avg8_neon:                   2.51   3.63   3.14   2.58
    vp9_avg16_neon:                  2.95   6.76   3.01   2.84
    vp9_avg32_neon:                  3.29   6.64   2.85   3.00
    vp9_avg64_neon:                  3.47   6.67   3.14   2.80
    vp9_avg_8tap_smooth_4h_neon:     3.22   4.73   2.76   4.67
    vp9_avg_8tap_smooth_4hv_neon:    3.67   4.76   3.28   4.71
    vp9_avg_8tap_smooth_4v_neon:     5.52   7.60   4.60   6.31
    vp9_avg_8tap_smooth_8h_neon:     6.22   9.04   5.12   9.32
    vp9_avg_8tap_smooth_8hv_neon:    6.38   8.21   5.72   8.17
    vp9_avg_8tap_smooth_8v_neon:     9.22  12.66   8.15  11.10
    vp9_avg_8tap_smooth_64h_neon:    7.02  10.23   5.54  11.58
    vp9_avg_8tap_smooth_64hv_neon:   6.76   9.46   5.93   9.40
    vp9_avg_8tap_smooth_64v_neon:   10.76  14.13   9.46  13.37
    vp9_put4_neon:                   1.11   1.47   1.00   1.21
    vp9_put8_neon:                   1.23   2.17   1.94   1.48
    vp9_put16_neon:                  1.63   4.02   1.73   1.97
    vp9_put32_neon:                  1.56   4.92   2.00   1.96
    vp9_put64_neon:                  2.10   5.28   2.03   2.35
    vp9_put_8tap_smooth_4h_neon:     3.11   4.35   2.63   4.35
    vp9_put_8tap_smooth_4hv_neon:    3.67   4.69   3.25   4.71
    vp9_put_8tap_smooth_4v_neon:     5.45   7.27   4.49   6.52
    vp9_put_8tap_smooth_8h_neon:     5.97   8.18   4.81   8.56
    vp9_put_8tap_smooth_8hv_neon:    6.39   7.90   5.64   8.15
    vp9_put_8tap_smooth_8v_neon:     9.03  11.84   8.07  11.51
    vp9_put_8tap_smooth_64h_neon:    6.78   9.48   4.88  10.89
    vp9_put_8tap_smooth_64hv_neon:   6.99   8.87   5.94   9.56
    vp9_put_8tap_smooth_64v_neon:   10.69  13.30   9.43  14.34
    
    For the larger 8tap filters, the speedup vs C code is around 5-14x.
    
    This is significantly faster than libvpx's implementation of the same
    functions, at least when comparing the put_8tap_smooth_64 functions
    (compared to vpx_convolve8_horiz_neon and vpx_convolve8_vert_neon from
    libvpx).
    
    Absolute runtimes from checkasm:
                              Cortex      A7        A8        A9       A53
    vp9_put_8tap_smooth_64h_neon:    20150.3   14489.4   19733.6   10863.7
    libvpx vpx_convolve8_horiz_neon: 52623.3   19736.4   21907.7   25027.7
    
    vp9_put_8tap_smooth_64v_neon:    14455.0   12303.9   13746.4    9628.9
    libvpx vpx_convolve8_vert_neon:  42090.0   17706.2   17659.9   16941.2
    
    Thus, on the A9, the horizontal filter is only marginally faster than
    libvpx, while our version is significantly faster on the other cores,
    and the vertical filter is significantly faster on all cores. The
    difference is especially large on the A7.
    
    The libvpx implementation does the accumulation in 32 bit, which
    probably explains most of the differences.
    
    This is an adapted cherry-pick from libav commits
    ffbd1d2b,
    392caa65,
    557c1675 and
    11623217.
    Signed-off-by: 's avatarRonald S. Bultje <rsbultje@gmail.com>
    68caef9d
vp9mc_neon.S 23.9 KB