cmd/gc: prevent ngotype from allocating.

R=golang-dev, dave, rsc
CC=golang-dev
https://golang.org/cl/6904061

src/cmd/gc/go.h

@@ -1211,6 +1211,7 @@ void	dumptypestructs(void);
 Type*	methodfunc(Type *f, Type*);
 Node*	typename(Type *t);
 Sym*	typesym(Type *t);
+Sym*	typenamesym(Type *t);
 Sym*	tracksym(Type *t);
 Sym*	typesymprefix(char *prefix, Type *t);
 int	haspointers(Type *t);

src/cmd/gc/reflect.c

@@ -652,8 +652,8 @@ typesymprefix(char *prefix, Type *t)
 	return s;
 }
 
-Node*
-typename(Type *t)
+Sym*
+typenamesym(Type *t)
 {
 	Sym *s;
 	Node *n;
@@ -674,7 +674,16 @@ typename(Type *t)
 
 		signatlist = list(signatlist, typenod(t));
 	}
+	return s->def->sym;
+}
+
+Node*
+typename(Type *t)
+{
+	Sym *s;
+	Node *n;
 
+	s = typenamesym(t);
 	n = nod(OADDR, s->def, N);
 	n->type = ptrto(s->def->type);
 	n->addable = 1;

src/cmd/gc/subr.c

@@ -3517,7 +3517,7 @@ ngotype(Node *n)
 {
 	if(n->sym != S && n->realtype != T)
 	if(strncmp(n->sym->name, "autotmp_", 8) != 0)
-		return typename(n->realtype)->left->sym;
+		return typenamesym(n->realtype);
 
 	return S;
 }