printing: commit some refactors (probably broken)

examples/add/add.s

@@ -0,0 +1,10 @@
+
+#include "textflag.h"
+
+// func Add(x uint64, y uint64) uint64
+TEXT ·Add(SB),0,$0-24
+	MOVQ	x(FP), CX
+	MOVQ	y+8(FP), AX
+	ADDQ	CX, AX
+	MOVQ	CX, ret+16(FP)
+	RET	

examples/add/add_test.go

@@ -0,0 +1,12 @@
+package add
+
+import (
+	"testing"
+	"testing/quick"
+)
+
+//go:generate go run asm.go -out add.s -stubs stub.go
+
+func TestAdd(t *testing.T) {
+	quick.CheckEqual(Add, func(x, y uint64) uint64 { return x + y }, nil)
+}

examples/add/asm.go

@@ -1,3 +1,5 @@
+// +build ignore
+
 package main
 
 import (
@@ -5,11 +7,11 @@ import (
 )
 
 func main() {
-	TEXT("add", "func(x, y uint64) uint64")
+	TEXT("Add", "func(x, y uint64) uint64")
 	x := Load(Param("x"), GP64v())
 	y := Load(Param("y"), GP64v())
 	ADDQ(x, y)
 	Store(x, ReturnIndex(0))
 	RET()
-	EOF()
+	Generate()
 }

examples/add/stub.go

@@ -0,0 +1,3 @@
+package add
+
+func Add(x uint64, y uint64) uint64