cmd/internal/gc: separate Node param fields

Param will be converted from an anonymous to a
named field in a subsequent, automated CL.

Reduces Node size from 368 to 328.
Reduces inuse_space on the rotate tests by about 3%.

No functional changes. Passes toolstash -cmp.

Updates #9933.

Change-Id: I5867b00328abf17ee24aea6ca58876bae9d8bfed
Reviewed-on: https://go-review.googlesource.com/10210Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/internal/gc/export.go

@@ -64,7 +64,7 @@ func autoexport(n *Node, ctxt uint8) {
 	if (ctxt != PEXTERN && ctxt != PFUNC) || dclcontext != PEXTERN {
 		return
 	}
-	if n.Ntype != nil && n.Ntype.Op == OTFUNC && n.Ntype.Left != nil { // method
+	if n.Param != nil && n.Ntype != nil && n.Ntype.Op == OTFUNC && n.Ntype.Left != nil { // method
 		return
 	}
 

src/cmd/internal/gc/subr.go

@@ -371,8 +371,12 @@ func Nod(op int, nleft *Node, nright *Node) *Node {
 	switch op {
 	case OCLOSURE, ODCLFUNC:
 		n.Func = new(Func)
+		n.Param = new(Param)
 	case ONAME:
 		n.Name = new(Name)
+		n.Param = new(Param)
+	case ODCLFIELD:
+		n.Param = new(Param)
 	}
 	return n
 }

src/cmd/internal/gc/syntax.go

@@ -65,21 +65,12 @@ type Node struct {
 
 	// ONAME
 	Name     *Name
-	Ntype    *Node
 	Defn     *Node // ONAME: initializing assignment; OLABEL: labeled statement
 	Pack     *Node // real package for import . names
 	Curfn    *Node // function for local variables
 	Paramfld *Type // TFIELD for this PPARAM; also for ODOT, curfn
-
-	// ONAME func param with PHEAP
-	Outerexpr  *Node // expression copied into closure for variable
-	Stackparam *Node // OPARAM node referring to stack copy of param
-	Alloc      *Node // allocation call
-
-	// ONAME closure param with PPARAMREF
-	Outer   *Node // outer PPARAMREF in nested closure
-	Closure *Node // ONAME/PHEAP <-> ONAME/PPARAMREF
-	Top     int   // top context (Ecall, Eproc, etc)
+	Alloc    *Node // allocation call
+	*Param
 
 	// OPACK
 	Pkg *Pkg
@@ -115,6 +106,19 @@ type Name struct {
 	Needzero  bool // if it contains pointers, needs to be zeroed on function entry
 }
 
+type Param struct {
+	Ntype *Node
+
+	// ONAME func param with PHEAP
+	Outerexpr  *Node // expression copied into closure for variable
+	Stackparam *Node // OPARAM node referring to stack copy of param
+
+	// ONAME closure param with PPARAMREF
+	Outer   *Node // outer PPARAMREF in nested closure
+	Closure *Node // ONAME/PHEAP <-> ONAME/PPARAMREF
+	Top     int   // top context (Ecall, Eproc, etc)
+}
+
 // Func holds Node fields used only with function-like nodes.
 type Func struct {
 	Shortname *Node

src/cmd/internal/gc/typecheck.go

@@ -813,7 +813,7 @@ OpSwitch:
 		var l *Node
 		for l = n.Left; l != r; l = l.Left {
 			l.Addrtaken = true
-			if l.Closure != nil {
+			if l.Param != nil && l.Closure != nil {
 				l.Closure.Addrtaken = true
 			}
 		}
@@ -822,7 +822,7 @@ OpSwitch:
 			Fatal("found non-orig name node %v", l)
 		}
 		l.Addrtaken = true
-		if l.Closure != nil {
+		if l.Param != nil && l.Closure != nil {
 			l.Closure.Addrtaken = true
 		}
 		defaultlit(&n.Left, nil)
@@ -3273,13 +3273,13 @@ func checkassign(stmt *Node, n *Node) {
 		var l *Node
 		for l = n; l != r; l = l.Left {
 			l.Assigned = true
-			if l.Closure != nil {
+			if l.Param != nil && l.Closure != nil {
 				l.Closure.Assigned = true
 			}
 		}
 
 		l.Assigned = true
-		if l.Closure != nil {
+		if l.Param != nil && l.Closure != nil {
 			l.Closure.Assigned = true
 		}
 	}