mmcloughlin · May 20, 2018 05:19
diff --git a/add_amd64.go b/add_amd64.go
 package asmdoc

 //go:noescape
 func addAsm(a, b float64) float64

 var Add = addGeneric

 func useAsm() bool {
 	// check cpuid bits here
 	return true
 }

 func init() {
 	if useAsm() {
 		Add = addAsm
 	}
 }
diff --git a/add_generic.go b/add_generic.go
 // +build !amd64

 package asmdoc

 // Add returns the sum of a and b.
 func Add(a, b float64) float64 {
 	return addGeneric(a, b)
 }
diff --git a/add_test.go b/add_test.go
 package asmdoc

 import "testing"

 func TestAdd(t *testing.T) {
 	if Add(3, 4) != 7 {
 		t.Error("add doesn't work")
 	}
 }
diff --git a/asm_amd64.s b/asm_amd64.s
 #include "textflag.h"

 // func addAsm(lat, lng float64) float64
 TEXT ·addAsm(SB),NOSPLIT,$0
 	MOVSD lat+0(FP), X0
 	MOVSD lng+8(FP), X1
 	ADDSD X0, X1
 	MOVQ X1, ret+16(FP)
 	RET

diff --git a/common.go b/common.go
 package asmdoc

 // addGeneric provides a pure Go implementation of add.
 func addGeneric(a, b float64) float64 {
 	return a + b
 }
diff --git a/Godoc with Assembly Function.md b/Godoc with Assembly Function.md
	#include "textflag.h"

	// func addAsm(lat, lng float64) float64
	TEXT ·addAsm(SB),NOSPLIT,$0
	MOVSD lat+0(FP), X0
	MOVSD lng+8(FP), X1
	ADDSD X0, X1
	MOVQ X1, ret+16(FP)
	RET
	package asmdoc

	// addGeneric provides a pure Go implementation of add.
	func addGeneric(a, b float64) float64 {
	return a + b
	}