[interpreter] Ensure --debug-code works with snapshots.

src/interpreter/interpreter.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/interpreter/interpreter.h"
 
 #include <fstream>
 #include <memory>
 
 #include "src/ast/prettyprinter.h"
@@ skipping 196 matching lines @@
   info()->SetCode(info()->isolate()->builtins()->InterpreterEntryTrampoline());
   return SUCCEEDED;
 }
 
 CompilationJob* Interpreter::NewCompilationJob(CompilationInfo* info) {
   return new InterpreterCompilationJob(info);
 }
 
 bool Interpreter::IsDispatchTableInitialized() {
   if (FLAG_trace_ignition || FLAG_trace_ignition_codegen ||
-      FLAG_trace_ignition_dispatches) {
+      FLAG_trace_ignition_dispatches || FLAG_debug_code) {

[rmcilroy, 2016/10/24 13:46:54]

While you are here, there is a bug that GetBytecodeHandler calls
IsDispatchTableInitialized which means any calls to GetBytecodeHandler fail if
any of these flags are set. Could you create a seperate function
(ShouldInitializeDispatchTable) which checks these flags, and have
IsDispatchTableInitialized only check dispatch_table_[0] != nullptr ?

[Michael Starzinger, 2016/10/25 09:46:12]

Done. Actually one of the try-bots ran into this bug. Thanks for the pointers.

     // Regenerate table to add bytecode tracing operations, print the assembly
-    // code generated by TurboFan or instrument handlers with dispatch counters.
+    // code generated by TurboFan, instrument handlers with dispatch counters,
+    // or insert debugging code into the bytecode handlers.
     return false;
   }
   return dispatch_table_[0] != nullptr;
 }
 
 void Interpreter::TraceCodegen(Handle<Code> code) {
 #ifdef ENABLE_DISASSEMBLER
   if (FLAG_trace_ignition_codegen) {
     OFStream os(stdout);
     code->Disassemble(nullptr, os);
@@ skipping 2407 matching lines @@
   __ StoreObjectField(generator, JSGeneratorObject::kContinuationOffset,
       __ SmiTag(new_state));
   __ SetAccumulator(old_state);
 
   __ Dispatch();
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8