Avoid manual object's body traversal in GC.

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 2603 matching lines @@
     bool success = SlotsBuffer::AddTo(
         slots_buffer_allocator_, target_page->slots_buffer_address(), slot_type,
         addr, SlotsBuffer::FAIL_ON_OVERFLOW);
     if (!success) {
       EvictPopularEvacuationCandidate(target_page);
     }
   }
 }
 
 
+class RecordMigratedSlotVisitor final : public ObjectVisitor {
+ public:
+  RecordMigratedSlotVisitor(MarkCompactCollector* collector,
+                            SlotsBuffer** evacuation_slots_buffer)
+      : collector_(collector),
+        evacuation_slots_buffer_(evacuation_slots_buffer) {}
+
+  V8_INLINE void VisitPointer(Object** p) override {
+    collector_->RecordMigratedSlot(*p, reinterpret_cast<Address>(p),
+                                   evacuation_slots_buffer_);
+  }
+
+  V8_INLINE void VisitPointers(Object** start, Object** end) override {
+    while (start < end) {
+      collector_->RecordMigratedSlot(*start, reinterpret_cast<Address>(start),
+                                     evacuation_slots_buffer_);
+      ++start;
+    }
+  }
+
+  V8_INLINE void VisitCodeEntry(Address code_entry_slot) override {
+    if (collector_->compacting_) {
+      Address code_entry = Memory::Address_at(code_entry_slot);
+      collector_->RecordMigratedCodeEntrySlot(code_entry, code_entry_slot,
+                                              evacuation_slots_buffer_);
+    }
+  }
+
+ private:
+  MarkCompactCollector* collector_;
+  SlotsBuffer** evacuation_slots_buffer_;
+};
+
+
 // We scavenge new space simultaneously with sweeping. This is done in two
 // passes.
 //
 // The first pass migrates all alive objects from one semispace to another or
 // promotes them to old space.  Forwarding address is written directly into
 // first word of object without any encoding.  If object is dead we write
 // NULL as a forwarding address.
 //
 // The second pass updates pointers to new space in all spaces.  It is possible
 // to encounter pointers to dead new space objects during traversal of pointers
 // to new space.  We should clear them to avoid encountering them during next
 // pointer iteration.  This is an issue if the store buffer overflows and we
 // have to scan the entire old space, including dead objects, looking for
 // pointers to new space.
 void MarkCompactCollector::MigrateObject(
     HeapObject* dst, HeapObject* src, int size, AllocationSpace dest,
     SlotsBuffer** evacuation_slots_buffer) {
   Address dst_addr = dst->address();
   Address src_addr = src->address();
   DCHECK(heap()->AllowedToBeMigrated(src, dest));
   DCHECK(dest != LO_SPACE);
   if (dest == OLD_SPACE) {
     DCHECK_OBJECT_SIZE(size);
     DCHECK(evacuation_slots_buffer != nullptr);
     DCHECK(IsAligned(size, kPointerSize));
-    switch (src->ContentType()) {
-      case HeapObjectContents::kTaggedValues:
-        MigrateObjectTagged(dst, src, size, evacuation_slots_buffer);
-        break;
 
-      case HeapObjectContents::kMixedValues:
-        MigrateObjectMixed(dst, src, size, evacuation_slots_buffer);
-        break;
-
-      case HeapObjectContents::kRawValues:
-        MigrateObjectRaw(dst, src, size);
-        break;
-    }
-
-    if (compacting_ && dst->IsJSFunction()) {
-      Address code_entry_slot = dst->address() + JSFunction::kCodeEntryOffset;
-      Address code_entry = Memory::Address_at(code_entry_slot);
-      RecordMigratedCodeEntrySlot(code_entry, code_entry_slot,
-                                  evacuation_slots_buffer);
-    }
+    heap()->MoveBlock(dst->address(), src->address(), size);
+    RecordMigratedSlotVisitor visitor(this, evacuation_slots_buffer);
+    dst->IterateBody(&visitor);
   } else if (dest == CODE_SPACE) {
     DCHECK_CODEOBJECT_SIZE(size, heap()->code_space());
     DCHECK(evacuation_slots_buffer != nullptr);
     PROFILE(isolate(), CodeMoveEvent(src_addr, dst_addr));
     heap()->MoveBlock(dst_addr, src_addr, size);
     RecordMigratedCodeObjectSlot(dst_addr, evacuation_slots_buffer);
     Code::cast(dst)->Relocate(dst_addr - src_addr);
   } else {
     DCHECK_OBJECT_SIZE(size);
     DCHECK(evacuation_slots_buffer == nullptr);
     DCHECK(dest == NEW_SPACE);
     heap()->MoveBlock(dst_addr, src_addr, size);
   }
   heap()->OnMoveEvent(dst, src, size);
   Memory::Address_at(src_addr) = dst_addr;
 }
 
 
-void MarkCompactCollector::MigrateObjectTagged(
-    HeapObject* dst, HeapObject* src, int size,
-    SlotsBuffer** evacuation_slots_buffer) {
-  Address src_slot = src->address();
-  Address dst_slot = dst->address();
-  for (int remaining = size / kPointerSize; remaining > 0; remaining--) {
-    Object* value = Memory::Object_at(src_slot);
-    Memory::Object_at(dst_slot) = value;
-    RecordMigratedSlot(value, dst_slot, evacuation_slots_buffer);
-    src_slot += kPointerSize;
-    dst_slot += kPointerSize;
-  }
-}
-
-
-void MarkCompactCollector::MigrateObjectMixed(
-    HeapObject* dst, HeapObject* src, int size,
-    SlotsBuffer** evacuation_slots_buffer) {
-  if (src->IsFixedTypedArrayBase()) {
-    heap()->MoveBlock(dst->address(), src->address(), size);
-    Address base_pointer_slot =
-        dst->address() + FixedTypedArrayBase::kBasePointerOffset;
-    RecordMigratedSlot(Memory::Object_at(base_pointer_slot), base_pointer_slot,
-                       evacuation_slots_buffer);
-  } else if (src->IsBytecodeArray()) {
-    heap()->MoveBlock(dst->address(), src->address(), size);
-    Address constant_pool_slot =
-        dst->address() + BytecodeArray::kConstantPoolOffset;
-    RecordMigratedSlot(Memory::Object_at(constant_pool_slot),
-                       constant_pool_slot, evacuation_slots_buffer);
-  } else if (src->IsJSArrayBuffer()) {
-    heap()->MoveBlock(dst->address(), src->address(), size);
-
-    // Visit inherited JSObject properties and byte length of ArrayBuffer
-    Address regular_slot =
-        dst->address() + JSArrayBuffer::BodyDescriptor::kStartOffset;
-    Address regular_slots_end =
-        dst->address() + JSArrayBuffer::kByteLengthOffset + kPointerSize;
-    while (regular_slot < regular_slots_end) {
-      RecordMigratedSlot(Memory::Object_at(regular_slot), regular_slot,
-                         evacuation_slots_buffer);
-      regular_slot += kPointerSize;
-    }
-
-    // Skip backing store and visit just internal fields
-    Address internal_field_slot = dst->address() + JSArrayBuffer::kSize;
-    Address internal_fields_end =
-        dst->address() + JSArrayBuffer::kSizeWithInternalFields;
-    while (internal_field_slot < internal_fields_end) {
-      RecordMigratedSlot(Memory::Object_at(internal_field_slot),
-                         internal_field_slot, evacuation_slots_buffer);
-      internal_field_slot += kPointerSize;
-    }
-  } else if (FLAG_unbox_double_fields) {
-    Address dst_addr = dst->address();
-    Address src_addr = src->address();
-    Address src_slot = src_addr;
-    Address dst_slot = dst_addr;
-
-    LayoutDescriptorHelper helper(src->map());
-    DCHECK(!helper.all_fields_tagged());
-    for (int remaining = size / kPointerSize; remaining > 0; remaining--) {
-      Object* value = Memory::Object_at(src_slot);
-
-      Memory::Object_at(dst_slot) = value;
-
-      if (helper.IsTagged(static_cast<int>(src_slot - src_addr))) {
-        RecordMigratedSlot(value, dst_slot, evacuation_slots_buffer);
-      }
-
-      src_slot += kPointerSize;
-      dst_slot += kPointerSize;
-    }
-  } else {
-    UNREACHABLE();
-  }
-}
-
-
-void MarkCompactCollector::MigrateObjectRaw(HeapObject* dst, HeapObject* src,
-                                            int size) {
-  heap()->MoveBlock(dst->address(), src->address(), size);
-}
-
-
 static inline void UpdateSlot(Isolate* isolate, ObjectVisitor* v,
                               SlotsBuffer::SlotType slot_type, Address addr) {
   switch (slot_type) {
     case SlotsBuffer::CODE_TARGET_SLOT: {
       RelocInfo rinfo(addr, RelocInfo::CODE_TARGET, 0, NULL);
       rinfo.Visit(isolate, v);
       break;
     }
     case SlotsBuffer::CELL_TARGET_SLOT: {
       RelocInfo rinfo(addr, RelocInfo::CELL, 0, NULL);
@@ skipping 338 matching lines @@
         InstanceType type = object->map()->instance_type();
         // Slots in maps and code can't be invalid because they are never
         // shrunk.
         if (type == MAP_TYPE || type == CODE_TYPE) return true;
 
         // Consider slots in objects that contain ONLY raw data as invalid.
         return false;
       }
 
       case HeapObjectContents::kMixedValues: {
+        int offset = static_cast<int>(slot - object->address());
         if (object->IsFixedTypedArrayBase()) {
-          return static_cast<int>(slot - object->address()) ==
-                 FixedTypedArrayBase::kBasePointerOffset;
+          return offset == FixedTypedArrayBase::kBasePointerOffset;
         } else if (object->IsBytecodeArray()) {
-          return static_cast<int>(slot - object->address()) ==
-                 BytecodeArray::kConstantPoolOffset;
+          return offset == BytecodeArray::kConstantPoolOffset;
         } else if (object->IsJSArrayBuffer()) {
-          int off = static_cast<int>(slot - object->address());
-          return (off >= JSArrayBuffer::BodyDescriptor::kStartOffset &&
-                  off <= JSArrayBuffer::kByteLengthOffset) ||
-                 (off >= JSArrayBuffer::kSize &&
-                  off < JSArrayBuffer::kSizeWithInternalFields);
+          return (offset >= JSArrayBuffer::kPropertiesOffset &&
+                  offset <= JSArrayBuffer::kByteLengthOffset) ||
+                 (offset >= JSArrayBuffer::kSize &&
+                  offset < JSArrayBuffer::kSizeWithInternalFields);
         } else if (FLAG_unbox_double_fields) {
           // Filter out slots that happen to point to unboxed double fields.
           LayoutDescriptorHelper helper(object->map());
           DCHECK(!helper.all_fields_tagged());
-          return helper.IsTagged(static_cast<int>(slot - object->address()));
+          return helper.IsTagged(offset);
         }
         break;
       }
     }
     UNREACHABLE();
     return true;
 }
 
 
 void MarkCompactCollector::VerifyIsSlotInLiveObject(Address slot,
@@ skipping 1418 matching lines @@
     MarkBit mark_bit = Marking::MarkBitFrom(host);
     if (Marking::IsBlack(mark_bit)) {
       RelocInfo rinfo(pc, RelocInfo::CODE_TARGET, 0, host);
       RecordRelocSlot(&rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8