8253636: C2: Adjust NodeClasses::_max_classes

Update NodeClasses::_max_classes to the max class id within the
enumeration. Update comment and assertion to reflect that NodeClasses uses now
32 bits after the addition of Opaque1 in JDK-8229495.

Reviewed-by: neliasso, kvn

src/hotspot/share/opto/node.cpp

@@ -1039,7 +1039,7 @@ bool Node::verify_jvms(const JVMState* using_jvms) const {
 
 //------------------------------init_NodeProperty------------------------------
 void Node::init_NodeProperty() {
-  assert(_max_classes <= max_jushort, "too many NodeProperty classes");
+  assert(_max_classes <= max_juint, "too many NodeProperty classes");
   assert(max_flags() <= max_jushort, "too many NodeProperty flags");
 }
 

src/hotspot/share/opto/node.hpp

@@ -608,7 +608,7 @@ class Node {
   ClassMask_##cl = ((Bit_##cl << 1) - 1) ,
 
   // This enum is used only for C2 ideal and mach nodes with is_<node>() methods
-  // so that it's values fits into 16 bits.
+  // so that its values fit into 32 bits.
   enum NodeClasses {
     Bit_Node   = 0x00000000,
     Class_Node = 0x00000000,
@@ -719,7 +719,7 @@ class Node {
     DEFINE_CLASS_ID(Halt, Node, 15)
     DEFINE_CLASS_ID(Opaque1, Node, 16)
 
-    _max_classes  = ClassMask_Halt
+    _max_classes  = ClassMask_Opaque1
   };
   #undef DEFINE_CLASS_ID