[interpreter] Introduce bytecode generation pipeline.

src/interpreter/interpreter.cc

Index: src/interpreter/interpreter.cc
diff --git a/src/interpreter/interpreter.cc b/src/interpreter/interpreter.cc
index 505202c6cb3e915330d88270ec77f328b38782db..8d06ba4d07c4554ffc8307b7aceaae04f1265aef 100644
--- a/src/interpreter/interpreter.cc
+++ b/src/interpreter/interpreter.cc
@@ -45,9 +45,13 @@ void Interpreter::Initialize() {
   }
 
   // Generate bytecode handlers for all bytecodes and scales.
-  for (OperandScale operand_scale = OperandScale::kSingle;
-       operand_scale <= OperandScale::kMaxValid;
-       operand_scale = Bytecodes::NextOperandScale(operand_scale)) {
+  const OperandScale kOperandScales[] = {
+#define VALUE(Name, _) OperandScale::k##Name,
+      OPERAND_SCALE_LIST(VALUE)
+#undef VALUE
+  };
+
+  for (OperandScale operand_scale : kOperandScales) {
 #define GENERATE_CODE(Name, ...)                                               \
   {                                                                            \
     if (Bytecodes::BytecodeHasHandler(Bytecode::k##Name, operand_scale)) {     \
@@ -93,12 +97,16 @@ size_t Interpreter::GetDispatchTableIndex(Bytecode bytecode,
                                           OperandScale operand_scale) {
   static const size_t kEntriesPerOperandScale = 1u << kBitsPerByte;
   size_t index = static_cast<size_t>(bytecode);
-  OperandScale current_scale = OperandScale::kSingle;
-  while (current_scale != operand_scale) {
-    index += kEntriesPerOperandScale;
-    current_scale = Bytecodes::NextOperandScale(current_scale);
+  switch (operand_scale) {
+    case OperandScale::kSingle:
+      return index;
+    case OperandScale::kDouble:
+      return index + kEntriesPerOperandScale;
+    case OperandScale::kQuadruple:
+      return index + 2 * kEntriesPerOperandScale;
   }
-  return index;
+  UNREACHABLE();
+  return 0;
 }
 
 void Interpreter::IterateDispatchTable(ObjectVisitor* v) {
@@ -1767,6 +1775,11 @@ void Interpreter::DoIllegal(InterpreterAssembler* assembler) {
   __ Abort(kInvalidBytecode);
 }
 
+// Nop
+//
+// No operation.
+void Interpreter::DoNop(InterpreterAssembler* assembler) { __ Dispatch(); }
+
 // SuspendGenerator <generator>
 //
 // Exports the register file and stores it into the generator.  Also stores the