Because the Go assembler doesn't have those instructions built in most likely. That sort of thing is quite common in Go assembler. The assemblers are a little

Because the Go assembler doesn't have those instructions built in most likely. That sort of thing is quite common in Go assembler. The assemblers are a little primitive and they force the assembly language for each processor into a common pattern, so when you are writing ARM assembler for instance, everything is backwards. I imagine having rationalised the assemblers between processors somewhat it makes the core developers lives easier though who have to lightly touch lots of different processor assembler.