• Martin Storsjö's avatar
    arm: vp9itxfm: Skip empty slices in the first pass of idct_idct 16x16 and 32x32 · 388f6e67
    Martin Storsjö authored
    This work is sponsored by, and copyright, Google.
    
    Previously all subpartitions except the eob=1 (DC) case ran with
    the same runtime:
    
                                         Cortex A7       A8       A9      A53
    vp9_inv_dct_dct_16x16_sub16_add_neon:   3188.1   2435.4   2499.0   1969.0
    vp9_inv_dct_dct_32x32_sub32_add_neon:  18531.7  16582.3  14207.6  12000.3
    
    By skipping individual 4x16 or 4x32 pixel slices in the first pass,
    we reduce the runtime of these functions like this:
    
    vp9_inv_dct_dct_16x16_sub1_add_neon:     274.6    189.5    211.7    235.8
    vp9_inv_dct_dct_16x16_sub2_add_neon:    2064.0   1534.8   1719.4   1248.7
    vp9_inv_dct_dct_16x16_sub4_add_neon:    2135.0   1477.2   1736.3   1249.5
    vp9_inv_dct_dct_16x16_sub8_add_neon:    2446.7   1828.7   1993.6   1494.7
    vp9_inv_dct_dct_16x16_sub12_add_neon:   2832.4   2118.3   2266.5   1735.1
    vp9_inv_dct_dct_16x16_sub16_add_neon:   3211.7   2475.3   2523.5   1983.1
    vp9_inv_dct_dct_32x32_sub1_add_neon:     756.2    456.7    862.0    553.9
    vp9_inv_dct_dct_32x32_sub2_add_neon:   10682.2   8190.4   8539.2   6762.5
    vp9_inv_dct_dct_32x32_sub4_add_neon:   10813.5   8014.9   8518.3   6762.8
    vp9_inv_dct_dct_32x32_sub8_add_neon:   11859.6   9313.0   9347.4   7514.5
    vp9_inv_dct_dct_32x32_sub12_add_neon:  12946.6  10752.4  10192.2   8280.2
    vp9_inv_dct_dct_32x32_sub16_add_neon:  14074.6  11946.5  11001.4   9008.6
    vp9_inv_dct_dct_32x32_sub20_add_neon:  15269.9  13662.7  11816.1   9762.6
    vp9_inv_dct_dct_32x32_sub24_add_neon:  16327.9  14940.1  12626.7  10516.0
    vp9_inv_dct_dct_32x32_sub28_add_neon:  17462.7  15776.1  13446.2  11264.7
    vp9_inv_dct_dct_32x32_sub32_add_neon:  18575.5  17157.0  14249.3  12015.1
    
    I.e. in general a very minor overhead for the full subpartition case due
    to the additional loads and cmps, but a significant speedup for the cases
    when we only need to process a small part of the actual input data.
    
    In common VP9 content in a few inspected clips, 70-90% of the non-dc-only
    16x16 and 32x32 IDCTs only have nonzero coefficients in the upper left
    8x8 or 16x16 subpartitions respectively.
    
    This is cherrypicked from libav commit
    9c8bc74c.
    Signed-off-by: 's avatarMichael Niedermayer <michael@niedermayer.cc>
    388f6e67
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