6926048: Improve Zero performance

Summary: Make Zero figure out result types in a similar way to C++ interpreter implementation.
Reviewed-by: kvn
Contributed-by: gbenson@redhat.com

src/cpu/zero/vm/cppInterpreter_zero.cpp

 /*
  * Copyright 2003-2007 Sun Microsystems, Inc.  All Rights Reserved.
- * Copyright 2007, 2008, 2009 Red Hat, Inc.
+ * Copyright 2007, 2008, 2009, 2010 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -145,7 +145,7 @@ void CppInterpreter::main_loop(int recurse, TRAPS) {
     }
     else if (istate->msg() == BytecodeInterpreter::return_from_method) {
       // Copy the result into the caller's frame
-      result_slots = type2size[method->result_type()];
+      result_slots = type2size[result_type_of(method)];
       assert(result_slots >= 0 && result_slots <= 2, "what?");
       result = istate->stack() + result_slots;
       break;
@@ -394,9 +394,10 @@ void CppInterpreter::native_entry(methodOop method, intptr_t UNUSED, TRAPS) {
 
   // Push our result
   if (!HAS_PENDING_EXCEPTION) {
-    stack->set_sp(stack->sp() - type2size[method->result_type()]);
+    BasicType type = result_type_of(method);
+    stack->set_sp(stack->sp() - type2size[type]);
 
-    switch (method->result_type()) {
+    switch (type) {
     case T_VOID:
       break;
 
@@ -707,6 +708,26 @@ int AbstractInterpreter::BasicType_as_index(BasicType type) {
   return i;
 }
 
+BasicType CppInterpreter::result_type_of(methodOop method) {
+  BasicType t;
+  switch (method->result_index()) {
+    case 0 : t = T_BOOLEAN; break;
+    case 1 : t = T_CHAR;    break;
+    case 2 : t = T_BYTE;    break;
+    case 3 : t = T_SHORT;   break;
+    case 4 : t = T_INT;     break;
+    case 5 : t = T_LONG;    break;
+    case 6 : t = T_VOID;    break;
+    case 7 : t = T_FLOAT;   break;
+    case 8 : t = T_DOUBLE;  break;
+    case 9 : t = T_OBJECT;  break;
+    default: ShouldNotReachHere();
+  }
+  assert(AbstractInterpreter::BasicType_as_index(t) == method->result_index(),
+         "out of step with AbstractInterpreter::BasicType_as_index");
+  return t;
+}
+
 address InterpreterGenerator::generate_empty_entry() {
   if (!UseFastEmptyMethods)
     return NULL;

src/cpu/zero/vm/cppInterpreter_zero.hpp

 /*
  * Copyright 1997-2007 Sun Microsystems, Inc.  All Rights Reserved.
- * Copyright 2007, 2008 Red Hat, Inc.
+ * Copyright 2007, 2008, 2010 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -41,3 +41,7 @@
  private:
   // Stack overflow checks
   static bool stack_overflow_imminent(JavaThread *thread);
+
+ private:
+  // Fast result type determination
+  static BasicType result_type_of(methodOop method);