cmd/compile: deduplication in the source code generated by mknode

Most types in the ir package don't have hidden children, so having
their doChildrenWithHidden and editChildrenWithHidden methods call
their own doChildren and editChildren methods can save a lot of
duplicate code.

Change-Id: Ib22a29d6a9a32855f3c3191ca2d26dff94ac556b
Reviewed-on: https://go-review.googlesource.com/c/go/+/697476
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>

src/cmd/compile/internal/ir/mknode.go

@@ -258,6 +258,7 @@ func processType(t *ast.TypeSpec) {
 	var doChildrenWithHiddenBody strings.Builder
 	var editChildrenBody strings.Builder
 	var editChildrenWithHiddenBody strings.Builder
+	var hasHidden bool
 	for _, f := range fields {
 		names := f.Names
 		ft := f.Type
@@ -309,6 +310,7 @@ func processType(t *ast.TypeSpec) {
 					"if n.%s != nil {\nn.%s = edit(n.%s).(%s%s)\n}\n", name, name, name, ptr, ft)
 			}
 			if hidden {
+				hasHidden = true
 				continue
 			}
 			if isSlice {
@@ -327,19 +329,27 @@ func processType(t *ast.TypeSpec) {
 	}
 	fmt.Fprintf(&buf, "func (n *%s) copy() Node {\nc := *n\n", name)
 	buf.WriteString(copyBody.String())
-	fmt.Fprintf(&buf, "return &c\n}\n")
+	buf.WriteString("return &c\n}\n")
 	fmt.Fprintf(&buf, "func (n *%s) doChildren(do func(Node) bool) bool {\n", name)
 	buf.WriteString(doChildrenBody.String())
-	fmt.Fprintf(&buf, "return false\n}\n")
+	buf.WriteString("return false\n}\n")
 	fmt.Fprintf(&buf, "func (n *%s) doChildrenWithHidden(do func(Node) bool) bool {\n", name)
-	buf.WriteString(doChildrenWithHiddenBody.String())
-	fmt.Fprintf(&buf, "return false\n}\n")
+	if hasHidden {
+		buf.WriteString(doChildrenWithHiddenBody.String())
+		buf.WriteString("return false\n}\n")
+	} else {
+		buf.WriteString("return n.doChildren(do)\n}\n")
+	}
 	fmt.Fprintf(&buf, "func (n *%s) editChildren(edit func(Node) Node) {\n", name)
 	buf.WriteString(editChildrenBody.String())
-	fmt.Fprintf(&buf, "}\n")
+	buf.WriteString("}\n")
 	fmt.Fprintf(&buf, "func (n *%s) editChildrenWithHidden(edit func(Node) Node) {\n", name)
-	buf.WriteString(editChildrenWithHiddenBody.String())
-	fmt.Fprintf(&buf, "}\n")
+	if hasHidden {
+		buf.WriteString(editChildrenWithHiddenBody.String())
+	} else {
+		buf.WriteString("n.editChildren(edit)\n")
+	}
+	buf.WriteString("}\n")
 }
 
 func generateHelpers() {