> APE is pushing the idea that x64 is a good bytecode And x86-64 is a particularly bad bytecode, for one main reason: its strong memory ordering rules, compare

> APE is pushing the idea that x64 is a good bytecode And x86-64 is a particularly bad bytecode, for one main reason: its strong memory ordering rules, compared to nearly every other architecture. IIRC, simple things like doing a store in x86-64 have an implicit release barrier, while other architectures can freely reorder the stores unless there's an explicit barrier. This means that a x86-64 emulator on for instance ARM has to either be single-threaded (and would still have issues with shared mmap regions), have special hardware support for x86-compatible memory ordering (as found for instance on recent Apple ARM CPUs, and used for their x86-64 emulation, but not common elsewhere), or add explicit barriers everywhere (which kills the performance). The only real advantage of x86-64 as a bytecode would be that it has less registers than most other architectures (only 16 registers, while other 64-bit architectures usually have around 32 registers), which allows a 1:1 mapping of the registers on the emulator while still leaving plenty of them free for temporary use.