[Interpreter] Add support for global declarations and load/store of global variables

src/interpreter/bytecodes.cc

Index: src/interpreter/bytecodes.cc
diff --git a/src/interpreter/bytecodes.cc b/src/interpreter/bytecodes.cc
index 5f43ea3370f46619c25f8ac3b065a46f5adb0207..a50e39cc2f3f97b12d6162105b7cfafffeba2b83 100644
--- a/src/interpreter/bytecodes.cc
+++ b/src/interpreter/bytecodes.cc
@@ -266,6 +266,8 @@ std::ostream& operator<<(std::ostream& os, const OperandSize& operand_size) {
 
 static const int kLastParamRegisterIndex =
     -InterpreterFrameConstants::kLastParamFromRegisterPointer / kPointerSize;
+static const int kFunctionContextRegisterIndex =
+    -InterpreterFrameConstants::kContextFromRegisterPointer / kPointerSize;
 
 
 // Registers occupy range 0-127 in 8-bit value leaving 128 unused values.
@@ -291,6 +293,16 @@ int Register::ToParameterIndex(int parameter_count) const {
 }
 
 
+Register Register::function_context() {
+  return Register(kFunctionContextRegisterIndex);
+}
+
+
+bool Register::is_function_context() const {
+  return index() == kFunctionContextRegisterIndex;
+}
+
+
 int Register::MaxParameterIndex() { return kMaxParameterIndex; }