get the basic add example working

pass/pass.go

@@ -2,16 +2,43 @@ package pass
 
 import "github.com/mmcloughlin/avo"
 
-// TODO(mbm): pass types
+var Compile = Concat(
+	FunctionPass(LabelTarget),
+	FunctionPass(CFG),
+	FunctionPass(Liveness),
+	FunctionPass(AllocateRegisters),
+	FunctionPass(BindRegisters),
+	FunctionPass(VerifyAllocation),
+)
 
-// FunctionPass builds a full pass that operates on all functions independently.
-func FunctionPass(p func(*avo.Function) error) func(*avo.File) error {
-	return func(f *avo.File) error {
-		for _, fn := range f.Functions {
-			if err := p(fn); err != nil {
+type Interface interface {
+	Execute(*avo.File) error
+}
+
+type Func func(*avo.File) error
+
+func (p Func) Execute(f *avo.File) error {
+	return p(f)
+}
+
+type FunctionPass func(*avo.Function) error
+
+func (p FunctionPass) Execute(f *avo.File) error {
+	for _, fn := range f.Functions {
+		if err := p(fn); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func Concat(passes ...Interface) Interface {
+	return Func(func(f *avo.File) error {
+		for _, p := range passes {
+			if err := p.Execute(f); err != nil {
 				return err
 			}
 		}
 		return nil
-	}
+	})
 }