Go Assembly by Example: Hello

The following example is a bad example. It was obtained by using the following command on a simple Go program printing the string “hello world”: `go tool compile -S helloworld.go`
	package main
The underscore _ is to avoid an “unusued package” compiler error.	import _ "fmt"
	func hello()
	func main() { hello() }

This `#include` is needed to use Go Assembly’s constants (for example the `RODATA` that we use later on). Other pre-processor macros can be used in Go Assembly (like `#define`).	#include "textflag.h"
`DATA` allows you to store global words in memory 1, 2, 4 or 8 bytes at a time. The <> after the symbol name restricts the data to the current file.	DATA world<>+0(SB)/8, $"hello wo" DATA world<>+8(SB)/4, $"rld "
`GLOBL` makes the data global and read-only (`RODATA`) for the relevant length (12).	GLOBL world<>+0(SB), RODATA, $12 TEXT ·hello(SB),$88-0 SUBQ $88, SP MOVQ BP, 80(SP) LEAQ 80(SP), BP
A Go string is created in my_string (a pointer to the string followed by the string’s length).	LEAQ world<>+0(SB), AX MOVQ AX, my_string+48(SP) MOVQ $11, my_string+56(SP) MOVQ $0, autotmp_0+64(SP) MOVQ $0, autotmp_0+72(SP) LEAQ type·string(SB), AX MOVQ AX, (SP) LEAQ my_string+48(SP), AX MOVQ AX, 8(SP)
`convT2E` from the `runtime` package is used to create an interface.	CALL runtime·convT2E(SB) MOVQ 24(SP), AX MOVQ 16(SP), CX MOVQ CX, autotmp_0+64(SP) MOVQ AX, autotmp_0+72(SP) LEAQ autotmp_0+64(SP), AX MOVQ AX, (SP) MOVQ $1, 8(SP) MOVQ $1, 16(SP)
`fmt.Println` is called with the interface created	CALL fmt·Println(SB)
This is pretty complicated, the lesson here is: don’t try to call functions from Go’s assembly.	MOVQ 80(SP), BP ADDQ $88, SP RET

Next example: Arcsin.