add label type

ast.go

@@ -17,12 +17,22 @@ type Operand interface {
 	Asm
 }
 
+type Node interface {
+	node()
+}
+
+type Label string
+
+func (l Label) node() {}
+
 // Instruction is a single instruction in a function.
 type Instruction struct {
 	Opcode   string
 	Operands []Operand
 }
 
+func (i Instruction) node() {}
+
 // File represents an assembly file.
 type File struct {
 	Functions []*Function
@@ -36,7 +46,7 @@ func NewFile() *File {
 type Function struct {
 	name   string
 	params []Parameter
-	inst   []Instruction
+	nodes  []Node
 }
 
 func NewFunction(name string) *Function {
@@ -46,7 +56,15 @@ func NewFunction(name string) *Function {
 }
 
 func (f *Function) AddInstruction(i Instruction) {
-	f.inst = append(f.inst, i)
+	f.AddNode(i)
+}
+
+func (f *Function) AddLabel(l Label) {
+	f.AddNode(l)
+}
+
+func (f *Function) AddNode(n Node) {
+	f.nodes = append(f.nodes, n)
 }
 
 // Name returns the function name.

build/context.go

@@ -26,11 +26,19 @@ func (c *Context) Function(name string) {
 }
 
 func (c *Context) Instruction(i avo.Instruction) {
+	c.node(i)
+}
+
+func (c *Context) Label(l avo.Label) {
+	c.node(l)
+}
+
+func (c *Context) node(n avo.Node) {
 	if c.function == nil {
 		c.AddErrorMessage("no active function")
 		return
 	}
-	c.function.AddInstruction(i)
+	c.function.AddNode(n)
 }
 
 //go:generate avogen -output zinstructions.go build
@@ -47,7 +55,7 @@ func (c *Context) Result() (*avo.File, []error) {
 	return c.file, c.errs
 }
 
-func (c *Context) Generate(wout, werr io.Writer) {
+func (c *Context) Main(wout, werr io.Writer) int {
 	diag := log.New(werr, "", 0)
 
 	f, errs := c.Result()
@@ -55,11 +63,14 @@ func (c *Context) Generate(wout, werr io.Writer) {
 		for _, err := range errs {
 			diag.Println(err)
 		}
-		return
+		return 1
 	}
 
 	p := avo.NewGoPrinter(wout)
 	if err := p.Print(f); err != nil {
-		diag.Fatal(err)
+		diag.Println(err)
+		return 1
 	}
+
+	return 0
 }

build/global.go

@@ -5,12 +5,15 @@ import (
 	"io"
 	"log"
 	"os"
+
+	"github.com/mmcloughlin/avo"
 )
 
 // ctx provides a global build context.
 var ctx = NewContext()
 
 func TEXT(name string)  { ctx.Function(name) }
+func LABEL(name string) { ctx.Label(avo.Label(name)) }
 
 var (
 	output = flag.String("output", "", "output filename (default stdout)")
@@ -31,5 +34,5 @@ func EOF() {
 		}
 	}
 
-	ctx.Generate(w, os.Stderr)
+	os.Exit(ctx.Main(w, os.Stderr))
 }

printer.go

@@ -69,8 +69,15 @@ func (p *GoPrinter) multicomment(lines []string) {
 func (p *GoPrinter) function(f *Function) {
 	p.printf("TEXT %s%s(SB),0,$%d-%d\n", dot, f.Name(), f.FrameBytes(), f.ArgumentBytes())
 
-	for _, i := range f.inst {
+	for _, node := range f.nodes {
-		p.printf("\t%s\t%s\n", i.Opcode, joinOperands(i.Operands))
+		switch n := node.(type) {
+		case Instruction:
+			p.printf("\t%s\t%s\n", n.Opcode, joinOperands(n.Operands))
+		case Label:
+			p.printf("%s:\n", n)
+		default:
+			panic("unexpected node type")
+		}
 	}
 }