Before this commit, the (32-bit only) simple idct came in three
versions: A pure MMX IDCT and idct-put and idct-add versions
which use SSE2 at the put and add stage, but still use pure MMX
for the actual IDCT.
This commit ports said IDCT to SSE2; this was entirely trivial
for the IDCT1-5 and IDCT7 parts (where one can directly use
the full register width) and was easy for IDCT6 and IDCT8
(involving a few movhps and pshufds). Unfortunately, DC_COND_INIT
and Z_COND_INIT still use only the lower half of the registers.
This saved 4658B here; the benchmarking option of the dct test tool
showed a 15% speedup.
Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
ade54335b2