Revert of Rehash and clear deleted entries in weak collections during GC...

Revert of Rehash and clear deleted entries in weak collections during GC (patchset #8 id:140001 of https://codereview.chromium.org/1877233005/ )

Reason for revert:
[Sheriff] Speculative revert. Suspect for gc stress crashes, like:
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20GC%20Stress%20-%20custom%20snapshot/builds/5119

Original issue's description:
> Rehash and clear deleted entries in weak collections during GC
>
> Otherwise, they'll just keep growing until we run out of memory or hit the FixedArray's maximum capacity.
>
> BUG=v8:4909
> R=hpayer@chromium.org
> LOG=n
>
> Committed: https://crrev.com/e093a047796d4c0575fe63d36529e7fe89b8865d
> Cr-Commit-Position: refs/heads/master@{#35514}

TBR=hpayer@chromium.org,jochen@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4909

Review URL: https://codereview.chromium.org/1891863003

Cr-Commit-Position: refs/heads/master@{#35519}

src/heap/mark-compact.cc

@@ -2572,13 +2572,6 @@ void MarkCompactCollector::ClearWeakCollections() {
           table->RemoveEntry(i);
         }
       }
-      // Rehash if more than 25% of the entries are deleted entries.
-      // TODO(jochen): Consider to shrink the fixed array in place.
-      if ((table->NumberOfDeletedElements() << kJSWeakCollectionLoadFactorExp) >
-          table->NumberOfElements()) {
-        HandleScope scope(heap()->isolate());
-        table->Rehash(heap()->isolate()->factory()->undefined_value());
-      }
     }
     weak_collection_obj = weak_collection->next();
     weak_collection->set_next(heap()->undefined_value());

src/heap/mark-compact.h

@@ -512,10 +512,6 @@ class MarkCompactCollector {
   static const uint32_t kSingleFreeEncoding = 0;
   static const uint32_t kMultiFreeEncoding = 1;
 
-  // If the number of deleted slots in a JSWeakCollection exceeds the number
-  // of entries / 2^(factor), we rehash the table.
-  static const int kJSWeakCollectionLoadFactorExp = 1;
-
   static inline bool IsMarked(Object* obj);
   static bool IsUnmarkedHeapObjectWithHeap(Heap* heap, Object** p);
 

src/objects.cc

@@ -16867,16 +16867,6 @@ void HashTable<Derived, Shape, Key>::Rehash(Key key) {
       }
     }
   }
-  // Wipe deleted entries.
-  Heap* heap = GetHeap();
-  Object* the_hole = heap->the_hole_value();
-  Object* undefined = heap->undefined_value();
-  for (uint32_t current = 0; current < capacity; current++) {
-    if (get(EntryToIndex(current)) == the_hole) {
-      set(EntryToIndex(current), undefined);
-    }
-  }
-  SetNumberOfDeletedElements(0);
 }
 
 

test/cctest/test-weakmaps.cc

@@ -124,7 +124,7 @@ TEST(Weakness) {
   heap->CollectAllGarbage(false);
   CHECK_EQ(1, NumberOfWeakCalls);
   CHECK_EQ(0, ObjectHashTable::cast(weakmap->table())->NumberOfElements());
-  CHECK_EQ(0,
+  CHECK_EQ(2,
            ObjectHashTable::cast(weakmap->table())->NumberOfDeletedElements());
 }
 

test/cctest/test-weaksets.cc

@@ -123,8 +123,8 @@ TEST(WeakSet_Weakness) {
   heap->CollectAllGarbage(false);
   CHECK_EQ(1, NumberOfWeakCalls);
   CHECK_EQ(0, ObjectHashTable::cast(weakset->table())->NumberOfElements());
-  CHECK_EQ(0,
-           ObjectHashTable::cast(weakset->table())->NumberOfDeletedElements());
+  CHECK_EQ(
+      1, ObjectHashTable::cast(weakset->table())->NumberOfDeletedElements());
 }