Use weak cell to embed map in CompareNil IC.

src/objects.cc

 // Copyright 2013 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 <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/allocation-site-scopes.h"
@@ skipping 10806 matching lines @@
 void Code::FindAndReplace(const FindAndReplacePattern& pattern) {
   DCHECK(is_inline_cache_stub() || is_handler());
   DisallowHeapAllocation no_allocation;
   int mask = RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
   STATIC_ASSERT(FindAndReplacePattern::kMaxCount < 32);
   int current_pattern = 0;
   for (RelocIterator it(this, mask); !it.done(); it.next()) {
     RelocInfo* info = it.rinfo();
     Object* object = info->target_object();
     if (object->IsHeapObject()) {
-      DCHECK(!object->IsWeakCell());
+      if (object->IsWeakCell()) {
+        object = HeapObject::cast(WeakCell::cast(object)->value());
+      }
       Map* map = HeapObject::cast(object)->map();
       if (map == *pattern.find_[current_pattern]) {
         info->set_target_object(*pattern.replace_[current_pattern]);
         if (++current_pattern == pattern.count_) return;
       }
     }
   }
   UNREACHABLE();
 }
 
@@ skipping 6266 matching lines @@
   Handle<DependentCode> codes =
       DependentCode::Insert(handle(cell->dependent_code(), info->isolate()),
                             DependentCode::kPropertyCellChangedGroup,
                             info->object_wrapper());
   if (*codes != cell->dependent_code()) cell->set_dependent_code(*codes);
   info->dependencies(DependentCode::kPropertyCellChangedGroup)->Add(
       cell, info->zone());
 }
 
 } }  // namespace v8::internal