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

src/interpreter/bytecodes.h

Index: src/interpreter/bytecodes.h
diff --git a/src/interpreter/bytecodes.h b/src/interpreter/bytecodes.h
index a3dc8220e40293380e1b543a788857cf13ce06d9..a146241a49b46153cb45d5adfa1929fd830bc7ea 100644
--- a/src/interpreter/bytecodes.h
+++ b/src/interpreter/bytecodes.h
@@ -43,8 +43,12 @@ namespace interpreter {
   V(LdaTrue, OperandType::kNone)                                               \
   V(LdaFalse, OperandType::kNone)                                              \
                                                                                \
-  /* Load globals */                                                           \
+  /* Globals */                                                                \
   V(LdaGlobal, OperandType::kIdx8)                                             \
+  V(StaGlobal, OperandType::kIdx8)                                             \
+                                                                               \
+  /* Context operations */                                                     \
+  V(LdaContextSlot, OperandType::kReg8, OperandType::kIdx8)                    \
                                                                                \
   /* Register-accumulator transfers */                                         \
   V(Ldar, OperandType::kReg8)                                                  \
@@ -163,6 +167,10 @@ class Register {
   int ToParameterIndex(int parameter_count) const;
   static int MaxParameterIndex();
 
+  // Returns the register for the function's outer context.
+  static Register function_context();
+  bool is_function_context() const;
+
   static Register FromOperand(uint8_t operand);
   uint8_t ToOperand() const;