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

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/become.h"
@@ skipping 975 matching lines @@
   ASSERT(speculative_inlining_error_->IsLanguageError());
   ASSERT(!background_compilation_error_->IsSmi());
   ASSERT(background_compilation_error_->IsLanguageError());
   ASSERT(!vm_isolate_snapshot_object_table_->IsSmi());
   ASSERT(vm_isolate_snapshot_object_table_->IsArray());
 }
 
 
 // An object visitor which will mark all visited objects. This is used to
 // 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.
     ASSERT(!obj->IsMarked());
     // No forwarding corpses in the VM isolate.
     ASSERT(!obj->IsForwardingCorpse());
     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_;
 };
 
 
 #define SET_CLASS_NAME(class_name, name)                                       \
   cls = class_name##_class();                                                  \
   cls.set_name(Symbols::name());
 
 void Object::FinalizeVMIsolate(Isolate* isolate) {
   // Should only be run by the vm isolate.
   ASSERT(isolate == Dart::vm_isolate());
@@ skipping 22333 matching lines @@
   return UserTag::null();
 }
 
 
 const char* UserTag::ToCString() const {
   const String& tag_label = String::Handle(label());
   return tag_label.ToCString();
 }
 
 }  // namespace dart