Last snapshot bits to get working precompiled hello_world on x64.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 44261365800636ce2ef3dd96f134bdb548af0821..0a9bc5a9e4c093b69fa36740ac9a184960264106 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -832,11 +832,16 @@ class PremarkingVisitor : public ObjectVisitor {
   explicit PremarkingVisitor(Isolate* isolate) : ObjectVisitor(isolate) {}
 
   void VisitObject(RawObject* obj) {
-    ASSERT(!obj->IsMarked());
     // Free list elements should never be marked.
     if (!obj->IsFreeListElement()) {
       ASSERT(obj->IsVMHeapObject());
-      obj->SetMarkBitUnsynchronized();
+      if (obj->IsMarked()) {
+        // Precompiled instructions are loaded pre-marked.
+        ASSERT(Object::IsRunningPrecompiledCode());

[siva, 2015/09/15 23:22:01]

Yes, here it would be ASSERT(Dart::IsRunningPrecompiledCode()) which makes it
more readable.

[rmacnak, 2015/09/16 01:34:44]

Done.

+        ASSERT(obj->IsInstructions());
+      } else {
+        obj->SetMarkBitUnsynchronized();
+      }
     }
   }
 };