[Intepreter] Always use BytecodeGraphBuilder when --turbo-from-bytecode

src/compiler.h

Index: src/compiler.h
diff --git a/src/compiler.h b/src/compiler.h
index e2f71479407bccbd139518236500017f7ae0f121..b0f39938a5787d91bef4aac9e86673efe76afabb 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -37,6 +37,7 @@ class Compiler : public AllStatic {
  public:
   enum ClearExceptionFlag { KEEP_EXCEPTION, CLEAR_EXCEPTION };
   enum ConcurrencyMode { NOT_CONCURRENT, CONCURRENT };
+  enum CompilationTier { INTERPRETED, BASELINE, OPTIMIZED };
 
   // ===========================================================================
   // The following family of methods ensures a given function is compiled. The
@@ -65,6 +66,16 @@ class Compiler : public AllStatic {
   static bool Analyze(ParseInfo* info);
   // Adds deoptimization support, requires ParseAndAnalyze.
   static bool EnsureDeoptimizationSupport(CompilationInfo* info);
+  // Ensures that bytecode is generated.
+  static bool EnsureBytecode(CompilationInfo* info);
+
+  // The next compilation tier which the function should  be compiled to for
+  // optimization.
+  static CompilationTier NextCompilationTier(JSFunction* function);
+
+  // True if the given function compilation should use Ignition for unoptimized
+  // compilation.
+  static bool ShouldUseIgnition(CompilationInfo* info);

[Michael Starzinger, 2016/07/19 09:36:02]

There seems to be only one use of this predicate outside the compiler and it is
inside an assertion. Could we instead move the assertion from the
{AstGraphBuilder} into {GetOptimizedCode} where we decide to call
{info->MarkAsOptimizeFromBytecode} or not? I really would like to avoid exposing
this predicate.

[rmcilroy, 2016/07/19 13:13:50]

Yeah I thought you might say this :). I've removed the assertion - there isn't
really any other assertion we can add to GetOptimizedCode, it should mark it
unconditinally now (or bail out of optimization if EnsureBytecode fails), so
this should be just as good.

 
   // ===========================================================================
   // The following family of methods instantiates new functions for scripts or