When Writing Assembly in Go Actually Makes Sense

Writing assembly in Go makes sense when you need to bypass the compiler's abstraction for specific low-level optimizations, such as implementing critical runtime primitives, handling architecture-specific instructions, or interfacing with hardware that requires precise control over registers and memory layout. Use the go tool asm command to assemble .s files into object files that can be linked into your Go package, typically for functions like runtime.mallocgc or syscall entry points where standard Go cannot express the required logic.

go tool asm -p runtime -o runtime.o runtime/asm.s

This command assembles runtime/asm.s into runtime.o for the runtime package, which is then linked into the final binary.

Writing assembly in Go is like manually tuning a car engine instead of letting the factory build it; you only do this when you need maximum speed or specific control that the standard tools can't provide. It matters for the core parts of the language itself, like memory management or system calls, where every tiny bit of performance counts. You would use it when the Go compiler simply cannot generate the exact machine code your hardware or operating system requires.