[compiler-guy]

If you really are targeting the x86_64 instruction set, you should be writing x86_64 instructions. Then you get exactly what the hardware does and don’t get any of those pesky compiler assumptions.

Of course you don’t get any of those pleasant optimizations either. But those optimizations are only possible because of the assumptions.

[astrange]

There's some optimizing x86 assemblers actually. Of course, now you have to follow their rules.