Cardmarking writebarrier.

src/heap.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 188 matching lines @@
   V(closure_symbol, "(closure)")
 
 
 // Forward declaration of the GCTracer class.
 class GCTracer;
 class HeapStats;
 
 
 typedef String* (*ExternalStringTableUpdaterCallback)(Object** pointer);
 
+typedef bool (*DirtyRegionCallback)(Address start,
+                                    Address end,
+                                    ObjectSlotCallback copy_object_func);
+
 
 // The all static Heap captures the interface to the global object heap.
 // All JavaScript contexts by this process share the same object heap.
 
 class Heap : public AllStatic {
  public:
   // Configure heap size before setup. Return false if the heap has been
   // setup already.
   static bool ConfigureHeap(int max_semispace_size, int max_old_gen_size);
   static bool ConfigureHeapDefault();
@@ skipping 514 matching lines @@
   // not match the empty string.
   static String* hidden_symbol() { return hidden_symbol_; }
 
   // Iterates over all roots in the heap.
   static void IterateRoots(ObjectVisitor* v, VisitMode mode);
   // Iterates over all strong roots in the heap.
   static void IterateStrongRoots(ObjectVisitor* v, VisitMode mode);
   // Iterates over all the other roots in the heap.
   static void IterateWeakRoots(ObjectVisitor* v, VisitMode mode);
 
-  // Iterates remembered set of an old space.
-  static void IterateRSet(PagedSpace* space, ObjectSlotCallback callback);
+  enum ExpectedPageWatermarkState {
+    WATERMARK_SHOULD_BE_VALID,
+    WATERMARK_CAN_BE_INVALID
+  };
 
-  // Iterates a range of remembered set addresses starting with rset_start
-  // corresponding to the range of allocated pointers
-  // [object_start, object_end).
-  // Returns the number of bits that were set.
-  static int IterateRSetRange(Address object_start,
-                              Address object_end,
-                              Address rset_start,
-                              ObjectSlotCallback copy_object_func);
+  // For each dirty region on a page in use from an old space call
+  // visit_dirty_region callback.
+  // If either visit_dirty_region or callback can cause an allocation
+  // in old space and changes in allocation watermark then
+  // can_preallocate_during_iteration should be set to true.
+  // All pages will be marked as having invalid watermark upon
+  // iteration completion.
+  static void IterateDirtyRegions(
+      PagedSpace* space,
+      DirtyRegionCallback visit_dirty_region,
+      ObjectSlotCallback callback,
+      ExpectedPageWatermarkState expected_page_watermark_state);
+
+  // Interpret marks as a bitvector of dirty marks for regions of size
+  // Page::kRegionSize aligned by Page::kRegionAlignmentMask and covering
+  // memory interval from start to top. For each dirty region call a
+  // visit_dirty_region callback. Return updated bitvector of dirty marks.
+  static uint32_t IterateDirtyRegions(uint32_t marks,
+                                      Address start,
+                                      Address end,
+                                      DirtyRegionCallback visit_dirty_region,
+                                      ObjectSlotCallback callback);
+
+  // Iterate pointers to new space found in memory interval from start to end.
+  // Update dirty marks for page containing start address.
+  static void IterateAndMarkPointersToNewSpace(Address start,
+                                               Address end,
+                                               ObjectSlotCallback callback);
+
+  // Iterate pointers to new space found in memory interval from start to end.
+  // Return true if pointers to new space was found.
+  static bool IteratePointersInDirtyRegion(Address start,
+                                           Address end,
+                                           ObjectSlotCallback callback);
+
+
+  // Iterate pointers to new space found in memory interval from start to end.
+  // This interval is considered to belong to the map space.
+  // Return true if pointers to new space was found.
+  static bool IteratePointersInDirtyMapsRegion(Address start,
+                                               Address end,
+                                               ObjectSlotCallback callback);
+
 
   // Returns whether the object resides in new space.
   static inline bool InNewSpace(Object* object);
   static inline bool InFromSpace(Object* object);
   static inline bool InToSpace(Object* object);
 
   // Checks whether an address/object in the heap (including auxiliary
   // area and unused area).
   static bool Contains(Address addr);
   static bool Contains(HeapObject* value);
@@ skipping 81 matching lines @@
   static void TracePathToGlobal();
 #endif
 
   // Callback function passed to Heap::Iterate etc.  Copies an object if
   // necessary, the object might be promoted to an old space.  The caller must
   // ensure the precondition that the object is (a) a heap object and (b) in
   // the heap's from space.
   static void ScavengePointer(HeapObject** p);
   static inline void ScavengeObject(HeapObject** p, HeapObject* object);
 
-  // Clear a range of remembered set addresses corresponding to the object
-  // area address 'start' with size 'size_in_bytes', eg, when adding blocks
-  // to the free list.
-  static void ClearRSetRange(Address start, int size_in_bytes);
-
-  // Rebuild remembered set in old and map spaces.
-  static void RebuildRSets();
-
-  // Update an old object's remembered set
-  static int UpdateRSet(HeapObject* obj);
-
   // Commits from space if it is uncommitted.
   static void EnsureFromSpaceIsCommitted();
 
   // Support for partial snapshots.  After calling this we can allocate a
   // certain number of bytes using only linear allocation (with a
   // LinearAllocationScope and an AlwaysAllocateScope) without using freelists
   // or causing a GC.  It returns true of space was reserved or false if a GC is
   // needed.  For paged spaces the space requested must include the space wasted
   // at the end of each page when allocating linearly.
   static void ReserveSpace(
@@ skipping 72 matching lines @@
                                 bool check_number_string_cache = true);
 
   static Map* MapForExternalArrayType(ExternalArrayType array_type);
   static RootListIndex RootIndexForExternalArrayType(
       ExternalArrayType array_type);
 
   static void RecordStats(HeapStats* stats);
 
   // Copy block of memory from src to dst. Size of block should be aligned
   // by pointer size.
-  static inline void CopyBlock(Object** dst, Object** src, int byte_size);
+  static inline void CopyBlock(Address dst, Address src, int byte_size);
+
+  static inline void CopyBlockToOldSpaceAndUpdateRegionMarks(Address dst,
+                                                             Address src,
+                                                             int byte_size);
 
   // Optimized version of memmove for blocks with pointer size aligned sizes and
   // pointer size aligned addresses.
-  static inline void MoveBlock(Object** dst, Object** src, int byte_size);
+  static inline void MoveBlock(Address dst, Address src, int byte_size);
+
+  static inline void MoveBlockToOldSpaceAndUpdateRegionMarks(Address dst,
+                                                             Address src,
+                                                             int byte_size);
 
   // Check new space expansion criteria and expand semispaces if it was hit.
   static void CheckNewSpaceExpansionCriteria();
 
   static inline void IncrementYoungSurvivorsCounter(int survived) {
     survived_since_last_expansion_ += survived;
   }
 
   static void UpdateNewSpaceReferencesInExternalStringTable(
       ExternalStringTableUpdaterCallback updater_func);
@@ skipping 227 matching lines @@
 
 #if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
   // Record the copy of an object in the NewSpace's statistics.
   static void RecordCopiedObject(HeapObject* obj);
 
   // Record statistics before and after garbage collection.
   static void ReportStatisticsBeforeGC();
   static void ReportStatisticsAfterGC();
 #endif
 
-  // Rebuild remembered set in an old space.
-  static void RebuildRSets(PagedSpace* space);
-
-  // Rebuild remembered set in the large object space.
-  static void RebuildRSets(LargeObjectSpace* space);
-
   // Slow part of scavenge object.
   static void ScavengeObjectSlow(HeapObject** p, HeapObject* object);
 
   // Initializes a function with a shared part and prototype.
   // Returns the function.
   // Note: this code was factored out of AllocateFunction such that
   // other parts of the VM could use it. Specifically, a function that creates
   // instances of type JS_FUNCTION_TYPE benefit from the use of this function.
   // Please note this does not perform a garbage collection.
   static inline Object* InitializeFunction(JSFunction* function,
@@ skipping 68 matching lines @@
   }
 
   ~LinearAllocationScope() {
     Heap::linear_allocation_scope_depth_--;
     ASSERT(Heap::linear_allocation_scope_depth_ >= 0);
   }
 };
 
 
 #ifdef DEBUG
-// Visitor class to verify interior pointers that do not have remembered set
-// bits.  All heap object pointers have to point into the heap to a location
-// that has a map pointer at its first word.  Caveat: Heap::Contains is an
-// approximation because it can return true for objects in a heap space but
-// above the allocation pointer.
+// Visitor class to verify interior pointers in spaces that do not contain
+// or care about intergenerational references. All heap object pointers have to
+// point into the heap to a location that has a map pointer at its first word.
+// Caveat: Heap::Contains is an approximation because it can return true for
+// objects in a heap space but above the allocation pointer.
 class VerifyPointersVisitor: public ObjectVisitor {
  public:
   void VisitPointers(Object** start, Object** end) {
     for (Object** current = start; current < end; current++) {
       if ((*current)->IsHeapObject()) {
         HeapObject* object = HeapObject::cast(*current);
         ASSERT(Heap::Contains(object));
         ASSERT(object->map()->IsMap());
       }
     }
   }
 };
 
 
-// Visitor class to verify interior pointers that have remembered set bits.
-// As VerifyPointersVisitor but also checks that remembered set bits are
-// always set for pointers into new space.
-class VerifyPointersAndRSetVisitor: public ObjectVisitor {
+// Visitor class to verify interior pointers in spaces that use region marks
+// to keep track of intergenerational references.
+// As VerifyPointersVisitor but also checks that dirty marks are set
+// for regions covering intergenerational references.
+class VerifyPointersAndDirtyRegionsVisitor: public ObjectVisitor {
  public:
   void VisitPointers(Object** start, Object** end) {
     for (Object** current = start; current < end; current++) {
       if ((*current)->IsHeapObject()) {
         HeapObject* object = HeapObject::cast(*current);
         ASSERT(Heap::Contains(object));
         ASSERT(object->map()->IsMap());
         if (Heap::InNewSpace(object)) {
-          ASSERT(Page::IsRSetSet(reinterpret_cast<Address>(current), 0));
+          ASSERT(Heap::InToSpace(object));
+          Address addr = reinterpret_cast<Address>(current);
+          ASSERT(Page::FromAddress(addr)->IsRegionDirty(addr));
         }
       }
     }
   }
 };
 #endif
 
 
 // Space iterator for iterating over all spaces of the heap.
 // Returns each space in turn, and null when it is done.
@@ skipping 547 matching lines @@
 
   // To speed up scavenge collections new space string are kept
   // separate from old space strings.
   static List<Object*> new_space_strings_;
   static List<Object*> old_space_strings_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_