如何在汇编中的结构指针上定义函数？

Question

For example:

// dummy.go
type dummy struct {
    p uintptr
}

func (d dummy) Get(i int) uint64
//func (d *dummy) Get(i int) uint64 //no way to define *dummy in assembly

func (d dummy) Get can be defined as:

// dummy_amd64.s
#include "textflag.h"
TEXT ·dummy·Get(SB),NOSPLIT,$0
    MOVQ $42, 24(SP)
    RET

I tried

TEXT "".(*dummy).Get+0(SB),4,$0-24 //output from 6g -S
TEXT ""·(*dummy)·Get+0(SB),4,$0
TEXT ·*dummy·Get(SB),NOSPLIT,$0
//and
TEXT ·(*dummy)·Get(SB),NOSPLIT,$0

All of them gives me the same error:

syntax error, last name: "".

I'm sure I'm missing something obvious but I can't seem to figure it out.

Answer 1

This is actually not possible with the current toolchain. The context is explained in issue 4978

Note that there is a simple patch to enable this feature - but only a few people are using it.

You could write a normal assembly function (i.e. not method), and implement a call in the Go method, to this assembly function. But the extra call will not be optimized away by the compiler.

A possible workaround to this problem would be to implement some support to allow assembly functions to be inlined in Go code - which would bring more benefits. My understanding is it has been discussed in the past, but it is not planned yet.