[compiler] Sidestep optimizing of generator resumers.

src/runtime/runtime-generator.cc

 // Copyright 2014 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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/factory.h"
 #include "src/frames-inl.h"
 #include "src/objects-inl.h"
@@ skipping 185 matching lines @@
   if (generator->is_suspended()) {
     Handle<Code> code(generator->function()->code(), isolate);
     int offset = generator->continuation();
     RUNTIME_ASSERT(0 <= offset && offset < code->instruction_size());
     return Smi::FromInt(code->SourcePosition(offset));
   }
 
   return isolate->heap()->undefined_value();
 }
 
-
-// Optimization for the following three functions is disabled in
-// js/generator.js and compiler/ast-graph-builder.cc.
-
+// Optimization for builtins calling any of the following three functions is
+// disabled in js/generator.js and compiler.cc, hence they are unreachable.
 
 RUNTIME_FUNCTION(Runtime_GeneratorNext) {
   UNREACHABLE();
   return nullptr;
 }
 
-
 RUNTIME_FUNCTION(Runtime_GeneratorReturn) {
   UNREACHABLE();
   return nullptr;
 }
 
-
 RUNTIME_FUNCTION(Runtime_GeneratorThrow) {
   UNREACHABLE();
   return nullptr;
 }
+
 }  // namespace internal
 }  // namespace v8