[interpreter] Be explicit when to test BytecodeGraphBuilder.

src/compiler.cc

 // Copyright 2012 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/compiler.h"
 
 #include <algorithm>
 
 #include "src/ast/ast-numbering.h"
 #include "src/ast/prettyprinter.h"
@@ skipping 821 matching lines @@
   CanonicalHandleScope canonical(isolate);
   TimerEventScope<TimerEventOptimizeCode> optimize_code_timer(isolate);
   TRACE_EVENT0("v8", "V8.OptimizeCode");
 
   bool use_turbofan = UseTurboFan(info.get());
   base::SmartPointer<CompilationJob> job(
       use_turbofan ? compiler::Pipeline::NewCompilationJob(info.get())
                    : new HCompilationJob(info.get()));
 
   // TruboFan can optimize directly from existing bytecode.
-  if (use_turbofan && info->shared_info()->HasBytecodeArray()) {
+  if (FLAG_turbo_from_bytecode && use_turbofan &&
+      info->shared_info()->HasBytecodeArray()) {
     info->MarkAsOptimizeFromBytecode();
   }
 
   if (mode == Compiler::CONCURRENT) {
     if (GetOptimizedCodeLater(job.get())) {
       info.Detach();  // The background recompile job owns this now.
       job.Detach();   // The background recompile job owns this now.
       return isolate->builtins()->InOptimizationQueue();
     }
   } else {
@@ skipping 960 matching lines @@
     MaybeHandle<Code> code;
     if (cached.code != nullptr) code = handle(cached.code);
     Handle<Context> native_context(function->context()->native_context());
     SharedFunctionInfo::AddToOptimizedCodeMap(shared, native_context, code,
                                               literals, BailoutId::None());
   }
 }
 
 }  // namespace internal
 }  // namespace v8