Andreas Rheinhardt 5c830fccf4 avcodec/x86/snowdsp: Add SSSE3 inner_add_yblock ...

Compared to the MMX version, this version benefits from wider
registers and pmaddubsw. It also has fewer unnecessary loads
and stores: On x64, the MMX version has 12 unnecessary GPR loads
and 6 stores in each line when width is eight; for width 16,
there are 17 unnecessary GPR loads and six stores per line.
Even the 32bit SSSE3 version only has six loads and zero stores
per line more than the x64 version. Furthermore, in contrast
to the MMX version, the SSSE3 version also does not clobber
the array of block pointers given to it.

Benchmarks:
inner_add_yblock_2_c:                                   29.2 ( 1.00x)
inner_add_yblock_2_mmx:                                 32.5 ( 0.90x)
inner_add_yblock_2_ssse3:                               28.6 ( 1.02x)
inner_add_yblock_4_c:                                   85.2 ( 1.00x)
inner_add_yblock_4_mmx:                                 89.2 ( 0.96x)
inner_add_yblock_4_ssse3:                               84.5 ( 1.01x)
inner_add_yblock_8_c:                                  302.0 ( 1.00x)
inner_add_yblock_8_mmx:                                 77.0 ( 3.92x)
inner_add_yblock_8_ssse3:                               30.6 ( 9.85x)
inner_add_yblock_16_c:                                1164.7 ( 1.00x)
inner_add_yblock_16_mmx:                               260.4 ( 4.47x)
inner_add_yblock_16_ssse3:                              82.3 (14.15x)

Both the MMX and SSSE3 versions leave the size 2 and 4 cases
to ff_snow_inner_add_yblock_c() (but the MMX version has
a prologue at the beginning that it needs to undo before
the call, leading to the higher overhead for these sizes).
I don't know why the SSSE3 version is marginally faster than
the C version in these cases.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

2026-04-13 12:51:35 +02:00

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