Use weak cells in map checks in polymorphic ICs.

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 3399 matching lines @@
   }
 
   if (isolate->initial_object_prototype()->map() == this) {
     return true;
   }
 
   return false;
 }
 
 
+Handle<WeakCell> Map::WeakCellForMap(Handle<Map> map) {
+  // TODO(ulan): Cache the weak cell and avoid many allocations.
+  return map->GetIsolate()->factory()->NewWeakCell(map);
+}
+
+
 static Handle<Map> AddMissingElementsTransitions(Handle<Map> map,
                                                  ElementsKind to_kind) {
   DCHECK(IsTransitionElementsKind(map->elements_kind()));
 
   Handle<Map> current_map = map;
 
   ElementsKind kind = map->elements_kind();
   if (!map->is_prototype_map()) {
     while (kind != to_kind && !IsTerminalElementsKind(kind)) {
       kind = GetNextTransitionElementsKind(kind);
@@ skipping 7104 matching lines @@
 }
 
 
 Object* Code::FindNthObject(int n, Map* match_map) {
   DCHECK(is_inline_cache_stub());
   DisallowHeapAllocation no_allocation;
   int mask = RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
   for (RelocIterator it(this, mask); !it.done(); it.next()) {
     RelocInfo* info = it.rinfo();
     Object* object = info->target_object();
+    if (object->IsWeakCell()) object = WeakCell::cast(object)->value();
     if (object->IsHeapObject()) {
       if (HeapObject::cast(object)->map() == match_map) {
         if (--n == 0) return object;
       }
     }
   }
   return NULL;
 }
 
 
@@ skipping 12 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());
       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();
 }
 
 
 void Code::FindAllMaps(MapHandleList* maps) {
   DCHECK(is_inline_cache_stub());
   DisallowHeapAllocation no_allocation;
   int mask = RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
   for (RelocIterator it(this, mask); !it.done(); it.next()) {
     RelocInfo* info = it.rinfo();
     Object* object = info->target_object();
+    if (object->IsWeakCell()) object = WeakCell::cast(object)->value();
     if (object->IsMap()) maps->Add(handle(Map::cast(object)));
   }
 }
 
 
 Code* Code::FindFirstHandler() {
   DCHECK(is_inline_cache_stub());
   DisallowHeapAllocation no_allocation;
   int mask = RelocInfo::ModeMask(RelocInfo::CODE_TARGET);
   for (RelocIterator it(this, mask); !it.done(); it.next()) {
@@ skipping 26 matching lines @@
 
 MaybeHandle<Code> Code::FindHandlerForMap(Map* map) {
   DCHECK(is_inline_cache_stub());
   int mask = RelocInfo::ModeMask(RelocInfo::CODE_TARGET) |
              RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
   bool return_next = false;
   for (RelocIterator it(this, mask); !it.done(); it.next()) {
     RelocInfo* info = it.rinfo();
     if (info->rmode() == RelocInfo::EMBEDDED_OBJECT) {
       Object* object = info->target_object();
+      if (object->IsWeakCell()) object = WeakCell::cast(object)->value();
       if (object == map) return_next = true;
     } else if (return_next) {
       Code* code = Code::GetCodeFromTargetAddress(info->target_address());
       DCHECK(code->kind() == Code::HANDLER);
       return handle(code);
     }
   }
   return MaybeHandle<Code>();
 }
 
@@ skipping 6175 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