[heap] Avoid the use of cells to point from code to new-space objects.

src/heap/remembered-set.cc

 // Copyright 2016 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/remembered-set.h"
 #include "src/heap/heap-inl.h"
 #include "src/heap/heap.h"
 #include "src/heap/mark-compact.h"
 #include "src/heap/slot-set.h"
 #include "src/heap/spaces.h"
 #include "src/heap/store-buffer.h"
+#include "src/macro-assembler.h"
 
 namespace v8 {
 namespace internal {
 
 template <PointerDirection direction>
 void RememberedSet<direction>::ClearInvalidSlots(Heap* heap) {
   STATIC_ASSERT(direction == OLD_TO_NEW);
-  PageIterator it(heap->old_space());
-  MemoryChunk* chunk;
-  while (it.has_next()) {
-    chunk = it.next();
-    SlotSet* slots = GetSlotSet(chunk);
-    if (slots != nullptr) {
-      slots->Iterate([heap, chunk](Address addr) {
-        Object** slot = reinterpret_cast<Object**>(addr);
-        return IsValidSlot(heap, chunk, slot) ? KEEP_SLOT : REMOVE_SLOT;
-      });
+  {
+    PageIterator it(heap->old_space());
+    MemoryChunk* chunk;
+    while (it.has_next()) {
+      chunk = it.next();
+      {
+        SlotSet* slots = GetSlotSet(chunk);
+        if (slots != nullptr) {
+          slots->Iterate([heap, chunk](Address addr) {
+            Object** slot = reinterpret_cast<Object**>(addr);
+            return IsValidSlot(heap, chunk, slot) ? KEEP_SLOT : REMOVE_SLOT;
+          });
+        }
+      }
+    }
+  }
+  {
+    PageIterator it(heap->code_space());
+    MemoryChunk* chunk;
+    while (it.has_next()) {
+      chunk = it.next();
+      TypedSlotSet* slots = GetTypedSlotSet(chunk);
+      if (slots != nullptr) {
+        slots->Iterate(
+            [heap, chunk](SlotType type, Address host_addr, Address addr) {
+              if (IsValidTypedSlot(heap, chunk, type, host_addr, addr)) {

[ulan, 2016/06/08 14:37:00]

Just use Marking::IsBlack(Marking::MarkBitFrom(host_addr) instead of
IsValidTypedSlot.

If the code is alive the slot will be valid.

[ahaas, 2016/06/09 10:34:32]

Done.

+                return KEEP_SLOT;
+              } else {
+                return REMOVE_SLOT;
+              }
+            });
+      }
     }
   }
 }
 
 template <PointerDirection direction>
 void RememberedSet<direction>::VerifyValidSlots(Heap* heap) {
   Iterate(heap, [heap](Address addr) {
     HeapObject* obj =
         heap->mark_compact_collector()->FindBlackObjectBySlotSlow(addr);
     if (obj == nullptr) {
@@ skipping 23 matching lines @@
     return false;
   }
   HeapObject* heap_object = HeapObject::cast(object);
   // If the target object is not black, the source slot must be part
   // of a non-black (dead) object.
   return Marking::IsBlack(Marking::MarkBitFrom(heap_object)) &&
          heap->mark_compact_collector()->IsSlotInBlackObject(
              chunk, reinterpret_cast<Address>(slot));
 }
 
+template <PointerDirection direction>
+bool RememberedSet<direction>::IsValidTypedSlot(Heap* heap, MemoryChunk* chunk,
+                                                SlotType slot_type,
+                                                Address host_addr,
+                                                Address slot) {
+  STATIC_ASSERT(direction == OLD_TO_NEW);
+  Object* object;
+  Code* code = reinterpret_cast<Code*>(host_addr);
+  switch (slot_type) {
+    case CODE_TARGET_SLOT: {
+      RelocInfo rinfo(heap->isolate(), slot, RelocInfo::CODE_TARGET, 0, code);
+      object = rinfo.target_object();
+      break;
+    }
+    case CELL_TARGET_SLOT: {
+      RelocInfo rinfo(heap->isolate(), slot, RelocInfo::CELL, 0, code);
+      object = rinfo.target_object();
+      break;
+    }
+    case EMBEDDED_OBJECT_SLOT: {
+      RelocInfo rinfo(heap->isolate(), slot, RelocInfo::EMBEDDED_OBJECT, 0,
+                      code);
+      object = rinfo.target_object();
+      break;
+    }
+    case OBJECT_SLOT: {
+      object = *reinterpret_cast<Object**>(slot);
+      break;
+    }
+    default:
+      printf("Slot type: %d\n", slot_type);
+      UNREACHABLE();
+      break;
+  }
+
+  if (!heap->InNewSpace(object)) {
+    return false;
+  }
+  HeapObject* heap_object = HeapObject::cast(object);
+  // If the target object is not black, the source slot must be part
+  // of a non-black (dead) object.
+  return Marking::IsBlack(Marking::MarkBitFrom(heap_object)) &&
+         Marking::IsBlack(Marking::MarkBitFrom(host_addr));
+}
+
 template void RememberedSet<OLD_TO_NEW>::ClearInvalidSlots(Heap* heap);
 template void RememberedSet<OLD_TO_NEW>::VerifyValidSlots(Heap* heap);
 template void RememberedSet<OLD_TO_OLD>::VerifyValidSlots(Heap* heap);
 
 }  // namespace internal
 }  // namespace v8