[dev.regabi] cmd/compile: simplify fmt handling of Nodes

The existing code introduces many types in what appears to be an
attempt to avoid allocation when converting formatting argument lists.
Simplify by accepting that allocation is going to happen, especially
when Node itself turns into an interface.

Change-Id: I3c0d45ca01eace4924deb43c0ea7dc6d65943d08
Reviewed-on: https://go-review.googlesource.com/c/go/+/272929
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/fmt.go

@@ -238,72 +238,49 @@ func (o Op) oconv(s fmt.State, flag FmtFlag, mode fmtMode) {
 	fmt.Fprint(s, o.String())
 }
 
-type (
+type fmtMode int
-	fmtMode int
 
-	fmtNodeErr        Node
+type fmtNode struct {
-	fmtNodeDbg        Node
+	x *Node
-	fmtNodeTypeId     Node
+	m fmtMode
-	fmtNodeTypeIdName Node
-
-	fmtOpErr        Op
-	fmtOpDbg        Op
-	fmtOpTypeId     Op
-	fmtOpTypeIdName Op
-
-	fmtTypeErr        types.Type
-	fmtTypeDbg        types.Type
-	fmtTypeTypeId     types.Type
-	fmtTypeTypeIdName types.Type
-
-	fmtSymErr        types.Sym
-	fmtSymDbg        types.Sym
-	fmtSymTypeId     types.Sym
-	fmtSymTypeIdName types.Sym
-
-	fmtNodesErr        Nodes
-	fmtNodesDbg        Nodes
-	fmtNodesTypeId     Nodes
-	fmtNodesTypeIdName Nodes
-)
-
-func (n *fmtNodeErr) Format(s fmt.State, verb rune)        { (*Node)(n).format(s, verb, FErr) }
-func (n *fmtNodeDbg) Format(s fmt.State, verb rune)        { (*Node)(n).format(s, verb, FDbg) }
-func (n *fmtNodeTypeId) Format(s fmt.State, verb rune)     { (*Node)(n).format(s, verb, FTypeId) }
-func (n *fmtNodeTypeIdName) Format(s fmt.State, verb rune) { (*Node)(n).format(s, verb, FTypeIdName) }
-func (n *Node) Format(s fmt.State, verb rune)              { n.format(s, verb, FErr) }
-
-func (o fmtOpErr) Format(s fmt.State, verb rune)        { Op(o).format(s, verb, FErr) }
-func (o fmtOpDbg) Format(s fmt.State, verb rune)        { Op(o).format(s, verb, FDbg) }
-func (o fmtOpTypeId) Format(s fmt.State, verb rune)     { Op(o).format(s, verb, FTypeId) }
-func (o fmtOpTypeIdName) Format(s fmt.State, verb rune) { Op(o).format(s, verb, FTypeIdName) }
-func (o Op) Format(s fmt.State, verb rune)              { o.format(s, verb, FErr) }
-
-func (t *fmtTypeErr) Format(s fmt.State, verb rune) { typeFormat((*types.Type)(t), s, verb, FErr) }
-func (t *fmtTypeDbg) Format(s fmt.State, verb rune) { typeFormat((*types.Type)(t), s, verb, FDbg) }
-func (t *fmtTypeTypeId) Format(s fmt.State, verb rune) {
-	typeFormat((*types.Type)(t), s, verb, FTypeId)
 }
-func (t *fmtTypeTypeIdName) Format(s fmt.State, verb rune) {
+
-	typeFormat((*types.Type)(t), s, verb, FTypeIdName)
+func (f *fmtNode) Format(s fmt.State, verb rune) { f.x.format(s, verb, f.m) }
+
+type fmtOp struct {
+	x Op
+	m fmtMode
 }
 
+func (f *fmtOp) Format(s fmt.State, verb rune) { f.x.format(s, verb, f.m) }
+
+type fmtType struct {
+	x *types.Type
+	m fmtMode
+}
+
+func (f *fmtType) Format(s fmt.State, verb rune) { typeFormat(f.x, s, verb, f.m) }
+
+type fmtSym struct {
+	x *types.Sym
+	m fmtMode
+}
+
+func (f *fmtSym) Format(s fmt.State, verb rune) { symFormat(f.x, s, verb, f.m) }
+
+type fmtNodes struct {
+	x Nodes
+	m fmtMode
+}
+
+func (f *fmtNodes) Format(s fmt.State, verb rune) { f.x.format(s, verb, f.m) }
+
+func (n *Node) Format(s fmt.State, verb rune) { n.format(s, verb, FErr) }
+func (o Op) Format(s fmt.State, verb rune)    { o.format(s, verb, FErr) }
+
 // func (t *types.Type) Format(s fmt.State, verb rune)     // in package types
-
-func (y *fmtSymErr) Format(s fmt.State, verb rune)    { symFormat((*types.Sym)(y), s, verb, FErr) }
-func (y *fmtSymDbg) Format(s fmt.State, verb rune)    { symFormat((*types.Sym)(y), s, verb, FDbg) }
-func (y *fmtSymTypeId) Format(s fmt.State, verb rune) { symFormat((*types.Sym)(y), s, verb, FTypeId) }
-func (y *fmtSymTypeIdName) Format(s fmt.State, verb rune) {
-	symFormat((*types.Sym)(y), s, verb, FTypeIdName)
-}
-
 // func (y *types.Sym) Format(s fmt.State, verb rune)            // in package types  { y.format(s, verb, FErr) }
-
+func (n Nodes) Format(s fmt.State, verb rune) { n.format(s, verb, FErr) }
-func (n fmtNodesErr) Format(s fmt.State, verb rune)        { (Nodes)(n).format(s, verb, FErr) }
-func (n fmtNodesDbg) Format(s fmt.State, verb rune)        { (Nodes)(n).format(s, verb, FDbg) }
-func (n fmtNodesTypeId) Format(s fmt.State, verb rune)     { (Nodes)(n).format(s, verb, FTypeId) }
-func (n fmtNodesTypeIdName) Format(s fmt.State, verb rune) { (Nodes)(n).format(s, verb, FTypeIdName) }
-func (n Nodes) Format(s fmt.State, verb rune)              { n.format(s, verb, FErr) }
 
 func (m fmtMode) Fprintf(s fmt.State, format string, args ...interface{}) {
 	m.prepareArgs(args)
@@ -321,85 +298,23 @@ func (m fmtMode) Sprint(args ...interface{}) string {
 }
 
 func (m fmtMode) prepareArgs(args []interface{}) {
-	switch m {
+	for i, arg := range args {
-	case FErr:
+		switch arg := arg.(type) {
-		for i, arg := range args {
+		case Op:
-			switch arg := arg.(type) {
+			args[i] = &fmtOp{arg, m}
-			case Op:
+		case *Node:
-				args[i] = fmtOpErr(arg)
+			args[i] = &fmtNode{arg, m}
-			case *Node:
+		case *types.Type:
-				args[i] = (*fmtNodeErr)(arg)
+			args[i] = &fmtType{arg, m}
-			case *types.Type:
+		case *types.Sym:
-				args[i] = (*fmtTypeErr)(arg)
+			args[i] = &fmtSym{arg, m}
-			case *types.Sym:
+		case Nodes:
-				args[i] = (*fmtSymErr)(arg)
+			args[i] = &fmtNodes{arg, m}
-			case Nodes:
+		case int32, int64, string, types.EType, constant.Value:
-				args[i] = fmtNodesErr(arg)
+			// OK: printing these types doesn't depend on mode
-			case int32, int64, string, types.EType, constant.Value:
+		default:
-				// OK: printing these types doesn't depend on mode
+			Fatalf("mode.prepareArgs type %T", arg)
-			default:
-				Fatalf("mode.prepareArgs type %T", arg)
-			}
 		}
-	case FDbg:
-		for i, arg := range args {
-			switch arg := arg.(type) {
-			case Op:
-				args[i] = fmtOpDbg(arg)
-			case *Node:
-				args[i] = (*fmtNodeDbg)(arg)
-			case *types.Type:
-				args[i] = (*fmtTypeDbg)(arg)
-			case *types.Sym:
-				args[i] = (*fmtSymDbg)(arg)
-			case Nodes:
-				args[i] = fmtNodesDbg(arg)
-			case int32, int64, string, types.EType, constant.Value:
-				// OK: printing these types doesn't depend on mode
-			default:
-				Fatalf("mode.prepareArgs type %T", arg)
-			}
-		}
-	case FTypeId:
-		for i, arg := range args {
-			switch arg := arg.(type) {
-			case Op:
-				args[i] = fmtOpTypeId(arg)
-			case *Node:
-				args[i] = (*fmtNodeTypeId)(arg)
-			case *types.Type:
-				args[i] = (*fmtTypeTypeId)(arg)
-			case *types.Sym:
-				args[i] = (*fmtSymTypeId)(arg)
-			case Nodes:
-				args[i] = fmtNodesTypeId(arg)
-			case int32, int64, string, types.EType, constant.Value:
-				// OK: printing these types doesn't depend on mode
-			default:
-				Fatalf("mode.prepareArgs type %T", arg)
-			}
-		}
-	case FTypeIdName:
-		for i, arg := range args {
-			switch arg := arg.(type) {
-			case Op:
-				args[i] = fmtOpTypeIdName(arg)
-			case *Node:
-				args[i] = (*fmtNodeTypeIdName)(arg)
-			case *types.Type:
-				args[i] = (*fmtTypeTypeIdName)(arg)
-			case *types.Sym:
-				args[i] = (*fmtSymTypeIdName)(arg)
-			case Nodes:
-				args[i] = fmtNodesTypeIdName(arg)
-			case int32, int64, string, types.EType, constant.Value:
-				// OK: printing these types doesn't depend on mode
-			default:
-				Fatalf("mode.prepareArgs type %T", arg)
-			}
-		}
-	default:
-		Fatalf("mode.prepareArgs mode %d", m)
 	}
 }