Write assembly functions in Go by creating a `.s` file in your package, defining a global symbol with `TEXT`, and calling it from Go using `//go:nosplit` and `//go:linkname` or `//go:export` depending on direction.

How to Write Assembly Functions in Go

Write assembly functions in Go by creating a .s file in your package, defining a global symbol with TEXT, and calling it from Go using //go:nosplit and //go:linkname or //go:export depending on direction.

// myfunc.go
package main

//go:nosplit
//go:linkname myFunc myFunc
func myFunc(x int) int

// myfunc.s
TEXT ·myFunc(SB),NOSPLIT,$0
	MOVQ x+0(FP), AX
	RET

The TEXT directive defines the assembly function, NOSPLIT prevents stack splitting, and //go:linkname links the Go declaration to the assembly symbol.

You write low-level machine instructions in a separate file ending in .s to handle tasks Go can't do efficiently. The Go compiler treats this file as a native function you can call just like any other Go function. It's like writing a specialized tool in a different language that your main program can still use seamlessly.