Is that possible? I think you would have [1] to use a register to build up the immediate value. The assembler cannot/should not default to one, so I think the best one could do is having another macro for ADD that takes that helper register as an argument. That wouldn’t fix other instances in the AArch64 assembly code.

[1] I’m not familiar with AMD64, but maybe, you could use a thread local (edit: wouldn’t work with M:N threads. You’d need a coroutine-local. That would tie the assembler to golang, and thus would, even on that alone, be a very bad idea) or reserve space in the stack frame for it, too, but I don’t see those as realistic options

Would that be wise? The implemented solution uses a temporary register to hold the full value being added to rsp.

I don't know enough about how people use the go assembler, but I imagine it would be very surprising if `add $imm, rsp, rsp` clobbered an unrelated register when `$imm` is large enough. Especially since what's clobbered is the designated "temporary register", which I imagine is used all the time in handwritten go assembly.