82a68a8771
Its performance loss ranges from either being just as fast as individual loads (Skylake), a few percent slower (Alderlake), 8% slower (Zen 3), to completely disasterous (older/other CPUs). Sadly, gathers never panned out fast on x86, even with the benefit of time and implementation experience. This also saves a register, as there's no need to fill out an additional register mask. Zen 3 (16384-point transform): Before: 1561050 decicycles in av_tx (fft), 131072 runs, 0 skips After: 1449621 decicycles in av_tx (fft), 131072 runs, 0 skips Alderlake: 2% slower on big transforms (65536), to 1% (131072), to a few percent for smaller sizes.