Get the latest tech news
Why is Apple Rosetta 2 fast? (2022)
Rosetta 2 is remarkably fast when compared to other x86-on-ARM emulators. I’ve spent a little time looking at how it works, out of idle curiosity, and found it to be quite unusual, so I figur…
The Apple M1 has an undocumented extension that, when enabled, ensures instructions like ADDS, SUBS and CMP compute PF and AF and store them as bits 26 and 27 of NZCV respectively, providing accurate emulation with no performance penalty. While other emulators might require inter-instruction optimisations for performance, Rosetta 2 is able to trust a fast CPU, generate code that respects its caches and predictors, and solve the messiest problems in hardware. Rosetta 2 finds groups of instructions that set up or tear down stack frames, and merges them, pairing loads and stores, and delaying stack-pointer updates.
Or read this on Hacker News