Inline instance object hash code into object header on 64 bit.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 2c6422e7d0e5d68d8799ed3ba5034b6b3bc99174..67d1fa2d3a4e47deda358a78e68267b4ab590490 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -995,7 +995,7 @@ void Object::InitOnce(Isolate* isolate) {
 // premark all objects in the vm_isolate_ heap.
 class PremarkingVisitor : public ObjectVisitor {

[Vyacheslav Egorov (Google), 2017/06/07 06:21:15]

Maybe this name needs to be changed?

[erikcorry, 2017/06/16 09:26:39]

VMIsolateFixingVisitor

  public:
-  PremarkingVisitor() {}
+  PremarkingVisitor() : counter_(1337) {}
 
   void VisitObject(RawObject* obj) {
     // Free list elements should never be marked.
@@ -1005,8 +1005,28 @@ class PremarkingVisitor : public ObjectVisitor {
     if (!obj->IsFreeListElement()) {
       ASSERT(obj->IsVMHeapObject());
       obj->SetMarkBitUnsynchronized();
+#if defined(HASH_IN_OBJECT_HEADER)
+      // These objects end up in the read-only VM isolate which is shared
+      // between isolates, so we have to prepopulate them with identity hash
+      // codes, since we can't add hash codes later.
+      if (Object::GetCachedHash(obj) == 0) {
+        // Some classes have identity hash codes that depend on their contents,
+        // not per object.
+        ASSERT(!obj->IsStringInstance());
+        if (!obj->IsMint() && !obj->IsDouble() && !obj->IsBigint() &&
+            !obj->IsRawNull() && !obj->IsBool()) {
+          counter_ += 2011;  // The year Dart was announced and a prime.
+          counter_ &= 0x3fffffff;
+          if (counter_ == 0) counter_++;
+          Object::SetCachedHash(obj, counter_);
+        }
+      }
+#endif
     }
   }
+
+ private:
+  int counter_;
 };