diff --git a/cl/compile.go b/cl/compile.go
index 05d78220..19b7e265 100644
--- a/cl/compile.go
+++ b/cl/compile.go
@@ -571,10 +571,9 @@ func (p *context) call(b llssa.Builder, act llssa.DoAction, call *ssa.CallCommon
 		if fn == "ssa:wrapnilchk" { // TODO(xsw): check nil ptr
 			arg := args[0]
 			ret = p.compileValue(b, arg)
-			// log.Println("wrapnilchk:", ret.TypeOf())
 		} else {
 			args := p.compileValues(b, args, kind)
-			ret = b.BuiltinDo(act, fn, args...)
+			ret = b.Do(act, llssa.Builtin(fn), args...)
 		}
 	case *ssa.Function:
 		aFn, pyFn, ftype := p.compileFunction(cv)
diff --git a/ssa/expr.go b/ssa/expr.go
index 5c03955b..78dc1fbc 100644
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -43,6 +43,26 @@ func (v Expr) IsNil() bool {
 
 // -----------------------------------------------------------------------------
 
+type builtinTy struct {
+	name string
+}
+
+func (p builtinTy) Underlying() types.Type {
+	panic("don't call")
+}
+
+func (p builtinTy) String() string {
+	return "builtinTy"
+}
+
+// Builtin returns a builtin function expression.
+func Builtin(name string) Expr {
+	tbi := &aType{raw: rawType{&builtinTy{name}}, kind: vkBuiltin}
+	return Expr{Type: tbi}
+}
+
+// -----------------------------------------------------------------------------
+
 type pyVarTy struct {
 	mod  Expr
 	name string
@@ -742,6 +762,9 @@ func (b Builder) Call(fn Expr, args ...Expr) (ret Expr) {
 	case vkFuncDecl:
 		sig = raw.(*types.Signature)
 		ll = fn.ll
+	case vkBuiltin:
+		bi := raw.(*builtinTy)
+		return b.BuiltinCall(bi.name, args...)
 	default:
 		log.Panicf("unreachable: %d(%T)\n", kind, raw)
 	}
@@ -791,11 +814,6 @@ func (b Builder) Do(da DoAction, fn Expr, args ...Expr) (ret Expr) {
 // `fn` indicates the function: one of the built-in functions from the
 // Go spec (excluding "make" and "new").
 func (b Builder) BuiltinCall(fn string, args ...Expr) (ret Expr) {
-	return b.BuiltinDo(Call, fn, args...)
-}
-
-// BuiltinDo call a builtin function with an action.
-func (b Builder) BuiltinDo(da DoAction, fn string, args ...Expr) (ret Expr) {
 	switch fn {
 	case "len":
 		if len(args) == 1 {
diff --git a/ssa/type.go b/ssa/type.go
index f75b9fe3..0d1fda99 100644
--- a/ssa/type.go
+++ b/ssa/type.go
@@ -44,6 +44,7 @@ const (
 	vkFuncDecl
 	vkFuncPtr
 	vkClosure
+	vkBuiltin
 	vkPyFuncRef
 	vkPyVarRef
 	vkTuple