Testing has not been fully completed yet, but if PR merge. rav1d will become even more difficult to optimize.
How much real data alignment helps? Wouldn't -O3 with -Ofast do all code optimization for programmer. Contributor dav1d claims 1-3% growth after his optimization, depending on video dataset payload. He nullified 1% optimization in rav1d, if the real growth was 3%, rav1d will not soon be able to equalize benchmark results.
Another question in theory can Rust be faster than C? If all possible optimizations are applied.