Improves performance and no longer breaks the ABI (by forgetting
to call emms).
Old benchmarks:
add_8x8basis_c: 43.6 ( 1.00x)
add_8x8basis_ssse3: 12.3 ( 3.55x)
New benchmarks:
add_8x8basis_c: 43.0 ( 1.00x)
add_8x8basis_ssse3: 6.3 ( 6.79x)
Notice that the output of try_8x8basis_ssse3 changes a bit:
Before this commit, it computes certain values and adds the values
for i,i+1,i+4 and i+5 before right shifting them; now it adds
the values for i,i+1,i+8,i+9. The second pair in these lists
could be avoided (by shifting xmm0 and xmm1 before adding both together
instead of only shifting xmm0 after adding them), but the former
i,i+1 is inherent in using pmaddwd. This is the reason that this
function is not bitexact.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
