Reland "Recognize and optimize a.runtimeType == b.runtimeType pattern."

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index f29f6666330b84b27306ff2ec38695791592b12a..dc5719dead4fff562e1c91cb5234879041055c9e 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -224,6 +224,9 @@ class Isolate : public BaseIsolate {
 
   ObjectStore* object_store() const { return object_store_; }
   void set_object_store(ObjectStore* value) { object_store_ = value; }
+  static intptr_t object_store_offset() {
+    return OFFSET_OF(Isolate, object_store_);
+  }
 
   ApiState* api_state() const { return api_state_; }
   void set_api_state(ApiState* value) { api_state_ = value; }
@@ -733,6 +736,11 @@ class Isolate : public BaseIsolate {
   RawUserTag* current_tag_;
   RawUserTag* default_tag_;
   RawCode* ic_miss_code_;
+  ObjectStore* object_store_;
+
+  // Note: ClassTable has different size between PRODUCT and non-product builds.

[rmacnak, 2016/10/31 20:23:30]

We don't care if product/release/debug have different field offsets. For this
and other reasons, snapshots generated in one of these modes can only run on a
VM of the same mode. The snapshot reader checks they match and issues a specific
error message.

We do care that SIMARM and XARM agree on the field offsets, which I suspect is
what you encountered. Probably from all the bool fields that were above
object_store, which ARM prefers to word align and Intel prefers to pack.

Please add Isolate::object_store_offset() to CheckOffsets in dart.cc

+  // This means precompiled code cannot reference anything below ClassTable
+  // from the precompiled code because offsets will be different.
   ClassTable class_table_;
   bool single_step_;
   bool skip_step_;  // skip the next single step.
@@ -748,7 +756,6 @@ class Isolate : public BaseIsolate {
   uint64_t pause_capability_;
   uint64_t terminate_capability_;
   bool errors_fatal_;
-  ObjectStore* object_store_;
   uword top_exit_frame_info_;
   void* init_callback_data_;
   Dart_EnvironmentCallback environment_callback_;