Update tag bits atomically

runtime/vm/raw_object.h

 // 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.
 
 #ifndef VM_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/atomic.h"
 #include "vm/globals.h"
@@ skipping 301 matching lines @@
     const uword addr = reinterpret_cast<uword>(this);
     return (addr & kNewObjectBits) != kNewObjectBits;
   }
 
   // Support for GC marking bit.
   bool IsMarked() const {
     return MarkBit::decode(ptr()->tags_);
   }
   void SetMarkBit() {
     ASSERT(!IsMarked());
+    UpdateTagBit<MarkBit>(true);
+  }
+  void SetMarkBitUnsynchronized() {
+    ASSERT(!IsMarked());
     uword tags = ptr()->tags_;
     ptr()->tags_ = MarkBit::update(true, tags);
   }
   void ClearMarkBit() {
     ASSERT(IsMarked());
-    uword tags = ptr()->tags_;
-    ptr()->tags_ = MarkBit::update(false, tags);
+    UpdateTagBit<MarkBit>(false);
   }
 
   // Support for GC watched bit.
+  // TODO(iposva): Get rid of this.
   bool IsWatched() const {
     return WatchedBit::decode(ptr()->tags_);
   }
-  void SetWatchedBit() {
+  void SetWatchedBitUnsynchronized() {
     ASSERT(!IsWatched());
     uword tags = ptr()->tags_;
     ptr()->tags_ = WatchedBit::update(true, tags);
   }
-  void ClearWatchedBit() {
-    ASSERT(IsWatched());
+  void ClearWatchedBitUnsynchronized() {
     uword tags = ptr()->tags_;
     ptr()->tags_ = WatchedBit::update(false, tags);
   }
 
   // Support for object tags.
   bool IsCanonical() const {
     return CanonicalObjectTag::decode(ptr()->tags_);
   }
   void SetCanonical() {
-    uword tags = ptr()->tags_;
-    uword old_tags;
-    do {
-      old_tags = tags;
-      uword new_tags = CanonicalObjectTag::update(true, old_tags);
-      tags = AtomicOperations::CompareAndSwapWord(
-          &ptr()->tags_, old_tags, new_tags);
-    } while (tags != old_tags);
+    UpdateTagBit<CanonicalObjectTag>(true);
   }
   bool IsCreatedFromSnapshot() const {
     return CreatedFromSnapshotTag::decode(ptr()->tags_);
   }
   void SetCreatedFromSnapshot() {
-    uword tags = ptr()->tags_;
-    uword old_tags;
-    do {
-      old_tags = tags;
-      uword new_tags = CreatedFromSnapshotTag::update(true, old_tags);
-      tags = AtomicOperations::CompareAndSwapWord(
-          &ptr()->tags_, old_tags, new_tags);
-    } while (tags != old_tags);
+    UpdateTagBit<CreatedFromSnapshotTag>(true);
   }
 
   // Support for GC remembered bit.
   bool IsRemembered() const {
     return RememberedBit::decode(ptr()->tags_);
   }
   void SetRememberedBit() {
     ASSERT(!IsRemembered());
+    UpdateTagBit<RememberedBit>(true);
+  }
+  void SetRememberedBitUnsynchronized() {
+    ASSERT(!IsRemembered());
     uword tags = ptr()->tags_;
     ptr()->tags_ = RememberedBit::update(true, tags);
   }
   void ClearRememberedBit() {
+    UpdateTagBit<RememberedBit>(false);
+  }
+  void ClearRememberedBitUnsynchronized() {
     uword tags = ptr()->tags_;
     ptr()->tags_ = RememberedBit::update(false, tags);
   }
 
   bool IsDartInstance() {
     return (!IsHeapObject() || (GetClassId() >= kInstanceCid));
   }
   bool IsFreeListElement() {
     return ((GetClassId() == kFreeListElement));
   }
@@ skipping 79 matching lines @@
         reinterpret_cast<uword>(this) - kHeapObjectTag);
   }
 
   intptr_t SizeFromClass() const;
 
   intptr_t GetClassId() const {
     uword tags = ptr()->tags_;
     return ClassIdTag::decode(tags);
   }
 
+  template<class TagBitField>
+  void UpdateTagBit(bool value) {
+    uword tags = ptr()->tags_;
+    uword old_tags;
+    do {
+      old_tags = tags;
+      uword new_tags = TagBitField::update(value, old_tags);
+      tags = AtomicOperations::CompareAndSwapWord(
+          &ptr()->tags_, old_tags, new_tags);
+    } while (tags != old_tags);
+  }
+
   // All writes to heap objects should ultimately pass through one of the
   // methods below or their counterparts in Object, to ensure that the
   // write barrier is correctly applied.
 
   template<typename type>
   void StorePointer(type const* addr, type value) {
     // Ensure that this object contains the addr.
     ASSERT(Contains(reinterpret_cast<uword>(addr)));
     VerifiedMemory::Write(const_cast<type*>(addr), value);
     // Filter stores based on source and target.
@@ skipping 1634 matching lines @@
   COMPILE_ASSERT(kExternalTypedDataInt8ArrayCid ==
                  kTypedDataInt8ArrayViewCid + 15);
   COMPILE_ASSERT(kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14);
   COMPILE_ASSERT(kNullCid == kByteBufferCid + 1);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_