There's at least two M1 optimisations targeting Apple's software stack: 1. Fast uncontended atomics. Speeds up reference counting which is used heavily by Obje

There's at least two M1 optimisations targeting Apple's software stack: 1. Fast uncontended atomics. Speeds up reference counting which is used heavily by Objective-C code base (and Swift). Increase is massive comparing to Intel. 2. Guaranteed instruction ordering mode. Allows for faster Arm code to be produced by Rosetta when emulating x86. Without it emulation overhead would be much bigger (similar to what Microsoft is experiencing).