Oh. He used 14 registers to manually unroll the inner loop. IME, on modern architectures, manual unrolling doesn't win you anything (benchmarked on, among other

Oh. He used 14 registers to manually unroll the inner loop. IME, on modern architectures, manual unrolling doesn't win you anything (benchmarked on, among other things, the above-mentioned dotproduct). I wouldn't be surprised if he got close to optimal code by just NOT manually unrolling. Fewer registers used, compiler less confused.