diff --git a/src/stub-cache.cc b/src/stub-cache.cc
index cdb4874..3371b1b 100644
--- a/src/stub-cache.cc
+++ b/src/stub-cache.cc
@@ -1,4 +1,4 @@
-// Copyright 2011 the V8 project authors. All rights reserved.
+// Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -45,18 +45,13 @@
 
 StubCache::StubCache(Isolate* isolate) : isolate_(isolate) {
   ASSERT(isolate == Isolate::Current());
-  memset(primary_, 0, sizeof(primary_[0]) * StubCache::kPrimaryTableSize);
-  memset(secondary_, 0, sizeof(secondary_[0]) * StubCache::kSecondaryTableSize);
 }
 
 
-void StubCache::Initialize(bool create_heap_objects) {
+void StubCache::Initialize() {
   ASSERT(IsPowerOf2(kPrimaryTableSize));
   ASSERT(IsPowerOf2(kSecondaryTableSize));
-  if (create_heap_objects) {
-    HandleScope scope;
-    Clear();
-  }
+  Clear();
 }
 
 
@@ -82,14 +77,15 @@
   // Compute the primary entry.
   int primary_offset = PrimaryOffset(name, flags, map);
   Entry* primary = entry(primary_, primary_offset);
-  Code* hit = primary->value;
+  Code* old_code = primary->value;
 
   // If the primary entry has useful data in it, we retire it to the
   // secondary cache before overwriting it.
-  if (hit != isolate_->builtins()->builtin(Builtins::kIllegal)) {
-    Code::Flags primary_flags = Code::RemoveTypeFromFlags(hit->flags());
-    int secondary_offset =
-        SecondaryOffset(primary->key, primary_flags, primary_offset);
+  if (old_code != isolate_->builtins()->builtin(Builtins::kIllegal)) {
+    Map* old_map = primary->map;
+    Code::Flags old_flags = Code::RemoveTypeFromFlags(old_code->flags());
+    int seed = PrimaryOffset(primary->key, old_flags, old_map);
+    int secondary_offset = SecondaryOffset(primary->key, old_flags, seed);
     Entry* secondary = entry(secondary_, secondary_offset);
     *secondary = *primary;
   }
@@ -97,12 +93,14 @@
   // Update primary cache.
   primary->key = name;
   primary->value = code;
+  primary->map = map;
+  isolate()->counters()->megamorphic_stub_cache_updates()->Increment();
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeLoadNonexistent(String* name,
-                                               JSObject* receiver) {
+Handle<Code> StubCache::ComputeLoadNonexistent(Handle<String> name,
+                                               Handle<JSObject> receiver) {
   ASSERT(receiver->IsGlobalObject() || receiver->HasFastProperties());
   // If no global objects are present in the prototype chain, the load
   // nonexistent IC stub can be shared for all names for a given map
@@ -110,558 +108,446 @@
   // there are global objects involved, we need to check global
   // property cells in the stub and therefore the stub will be
   // specific to the name.
-  String* cache_name = heap()->empty_string();
+  Handle<String> cache_name = factory()->empty_string();
   if (receiver->IsGlobalObject()) cache_name = name;
-  JSObject* last = receiver;
+  Handle<JSObject> last = receiver;
   while (last->GetPrototype() != heap()->null_value()) {
-    last = JSObject::cast(last->GetPrototype());
+    last = Handle<JSObject>(JSObject::cast(last->GetPrototype()));
     if (last->IsGlobalObject()) cache_name = name;
   }
   // Compile the stub that is either shared for all names or
   // name specific if there are global objects involved.
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(Code::LOAD_IC, NONEXISTENT);
-  Object* code = receiver->map()->FindInCodeCache(cache_name, flags);
-  if (code->IsUndefined()) {
-    LoadStubCompiler compiler;
-    { MaybeObject* maybe_code =
-          compiler.CompileLoadNonexistent(cache_name, receiver, last);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::LOAD_IC_TAG, Code::cast(code), cache_name));
-    GDBJIT(AddCode(GDBJITInterface::LOAD_IC, cache_name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(cache_name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*cache_name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  LoadStubCompiler compiler(isolate_);
+  Handle<Code> code =
+      compiler.CompileLoadNonexistent(cache_name, receiver, last);
+  PROFILE(isolate_, CodeCreateEvent(Logger::LOAD_IC_TAG, *code, *cache_name));
+  GDBJIT(AddCode(GDBJITInterface::LOAD_IC, *cache_name, *code));
+  JSObject::UpdateMapCodeCache(receiver, cache_name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeLoadField(String* name,
-                                         JSObject* receiver,
-                                         JSObject* holder,
+Handle<Code> StubCache::ComputeLoadField(Handle<String> name,
+                                         Handle<JSObject> receiver,
+                                         Handle<JSObject> holder,
                                          int field_index) {
-  ASSERT(IC::GetCodeCacheForObject(receiver, holder) == OWN_MAP);
+  ASSERT(IC::GetCodeCacheForObject(*receiver, *holder) == OWN_MAP);
   Code::Flags flags = Code::ComputeMonomorphicFlags(Code::LOAD_IC, FIELD);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    LoadStubCompiler compiler;
-    { MaybeObject* maybe_code =
-          compiler.CompileLoadField(receiver, holder, field_index, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  LoadStubCompiler compiler(isolate_);
+  Handle<Code> code =
+      compiler.CompileLoadField(receiver, holder, field_index, name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeLoadCallback(String* name,
-                                            JSObject* receiver,
-                                            JSObject* holder,
-                                            AccessorInfo* callback) {
+Handle<Code> StubCache::ComputeLoadCallback(Handle<String> name,
+                                            Handle<JSObject> receiver,
+                                            Handle<JSObject> holder,
+                                            Handle<AccessorInfo> callback) {
   ASSERT(v8::ToCData<Address>(callback->getter()) != 0);
-  ASSERT(IC::GetCodeCacheForObject(receiver, holder) == OWN_MAP);
+  ASSERT(IC::GetCodeCacheForObject(*receiver, *holder) == OWN_MAP);
   Code::Flags flags = Code::ComputeMonomorphicFlags(Code::LOAD_IC, CALLBACKS);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    LoadStubCompiler compiler;
-    { MaybeObject* maybe_code =
-          compiler.CompileLoadCallback(name, receiver, holder, callback);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  LoadStubCompiler compiler(isolate_);
+  Handle<Code> code =
+      compiler.CompileLoadCallback(name, receiver, holder, callback);
+  PROFILE(isolate_, CodeCreateEvent(Logger::LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeLoadConstant(String* name,
-                                            JSObject* receiver,
-                                            JSObject* holder,
-                                            Object* value) {
-  ASSERT(IC::GetCodeCacheForObject(receiver, holder) == OWN_MAP);
+Handle<Code> StubCache::ComputeLoadConstant(Handle<String> name,
+                                            Handle<JSObject> receiver,
+                                            Handle<JSObject> holder,
+                                            Handle<JSFunction> value) {
+  ASSERT(IC::GetCodeCacheForObject(*receiver, *holder) == OWN_MAP);
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(Code::LOAD_IC, CONSTANT_FUNCTION);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    LoadStubCompiler compiler;
-    { MaybeObject* maybe_code =
-          compiler.CompileLoadConstant(receiver, holder, value, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  LoadStubCompiler compiler(isolate_);
+  Handle<Code> code =
+        compiler.CompileLoadConstant(receiver, holder, value, name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeLoadInterceptor(String* name,
-                                               JSObject* receiver,
-                                               JSObject* holder) {
-  ASSERT(IC::GetCodeCacheForObject(receiver, holder) == OWN_MAP);
+Handle<Code> StubCache::ComputeLoadInterceptor(Handle<String> name,
+                                               Handle<JSObject> receiver,
+                                               Handle<JSObject> holder) {
+  ASSERT(IC::GetCodeCacheForObject(*receiver, *holder) == OWN_MAP);
   Code::Flags flags = Code::ComputeMonomorphicFlags(Code::LOAD_IC, INTERCEPTOR);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    LoadStubCompiler compiler;
-    { MaybeObject* maybe_code =
-          compiler.CompileLoadInterceptor(receiver, holder, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  LoadStubCompiler compiler(isolate_);
+  Handle<Code> code =
+        compiler.CompileLoadInterceptor(receiver, holder, name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeLoadNormal() {
-  return isolate_->builtins()->builtin(Builtins::kLoadIC_Normal);
+Handle<Code> StubCache::ComputeLoadNormal() {
+  return isolate_->builtins()->LoadIC_Normal();
 }
 
 
-MaybeObject* StubCache::ComputeLoadGlobal(String* name,
-                                          JSObject* receiver,
-                                          GlobalObject* holder,
-                                          JSGlobalPropertyCell* cell,
+Handle<Code> StubCache::ComputeLoadGlobal(Handle<String> name,
+                                          Handle<JSObject> receiver,
+                                          Handle<GlobalObject> holder,
+                                          Handle<JSGlobalPropertyCell> cell,
                                           bool is_dont_delete) {
-  ASSERT(IC::GetCodeCacheForObject(receiver, holder) == OWN_MAP);
+  ASSERT(IC::GetCodeCacheForObject(*receiver, *holder) == OWN_MAP);
   Code::Flags flags = Code::ComputeMonomorphicFlags(Code::LOAD_IC, NORMAL);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    LoadStubCompiler compiler;
-    { MaybeObject* maybe_code = compiler.CompileLoadGlobal(receiver,
-                                                           holder,
-                                                           cell,
-                                                           name,
-                                                           is_dont_delete);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  LoadStubCompiler compiler(isolate_);
+  Handle<Code> code =
+      compiler.CompileLoadGlobal(receiver, holder, cell, name, is_dont_delete);
+  PROFILE(isolate_, CodeCreateEvent(Logger::LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeKeyedLoadField(String* name,
-                                              JSObject* receiver,
-                                              JSObject* holder,
+Handle<Code> StubCache::ComputeKeyedLoadField(Handle<String> name,
+                                              Handle<JSObject> receiver,
+                                              Handle<JSObject> holder,
                                               int field_index) {
-  ASSERT(IC::GetCodeCacheForObject(receiver, holder) == OWN_MAP);
+  ASSERT(IC::GetCodeCacheForObject(*receiver, *holder) == OWN_MAP);
   Code::Flags flags = Code::ComputeMonomorphicFlags(Code::KEYED_LOAD_IC, FIELD);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    KeyedLoadStubCompiler compiler;
-    { MaybeObject* maybe_code =
-          compiler.CompileLoadField(name, receiver, holder, field_index);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  KeyedLoadStubCompiler compiler(isolate_);
+  Handle<Code> code =
+      compiler.CompileLoadField(name, receiver, holder, field_index);
+  PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeKeyedLoadConstant(String* name,
-                                                 JSObject* receiver,
-                                                 JSObject* holder,
-                                                 Object* value) {
-  ASSERT(IC::GetCodeCacheForObject(receiver, holder) == OWN_MAP);
+Handle<Code> StubCache::ComputeKeyedLoadConstant(Handle<String> name,
+                                                 Handle<JSObject> receiver,
+                                                 Handle<JSObject> holder,
+                                                 Handle<JSFunction> value) {
+  ASSERT(IC::GetCodeCacheForObject(*receiver, *holder) == OWN_MAP);
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(Code::KEYED_LOAD_IC, CONSTANT_FUNCTION);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    KeyedLoadStubCompiler compiler;
-    { MaybeObject* maybe_code =
-          compiler.CompileLoadConstant(name, receiver, holder, value);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  KeyedLoadStubCompiler compiler(isolate_);
+  Handle<Code> code =
+      compiler.CompileLoadConstant(name, receiver, holder, value);
+  PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeKeyedLoadInterceptor(String* name,
-                                                    JSObject* receiver,
-                                                    JSObject* holder) {
-  ASSERT(IC::GetCodeCacheForObject(receiver, holder) == OWN_MAP);
+Handle<Code> StubCache::ComputeKeyedLoadInterceptor(Handle<String> name,
+                                                    Handle<JSObject> receiver,
+                                                    Handle<JSObject> holder) {
+  ASSERT(IC::GetCodeCacheForObject(*receiver, *holder) == OWN_MAP);
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(Code::KEYED_LOAD_IC, INTERCEPTOR);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    KeyedLoadStubCompiler compiler;
-    { MaybeObject* maybe_code =
-          compiler.CompileLoadInterceptor(receiver, holder, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  KeyedLoadStubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileLoadInterceptor(receiver, holder, name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeKeyedLoadCallback(String* name,
-                                                 JSObject* receiver,
-                                                 JSObject* holder,
-                                                 AccessorInfo* callback) {
-  ASSERT(IC::GetCodeCacheForObject(receiver, holder) == OWN_MAP);
+Handle<Code> StubCache::ComputeKeyedLoadCallback(
+    Handle<String> name,
+    Handle<JSObject> receiver,
+    Handle<JSObject> holder,
+    Handle<AccessorInfo> callback) {
+  ASSERT(IC::GetCodeCacheForObject(*receiver, *holder) == OWN_MAP);
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(Code::KEYED_LOAD_IC, CALLBACKS);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    KeyedLoadStubCompiler compiler;
-    { MaybeObject* maybe_code =
-          compiler.CompileLoadCallback(name, receiver, holder, callback);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  KeyedLoadStubCompiler compiler(isolate_);
+  Handle<Code> code =
+      compiler.CompileLoadCallback(name, receiver, holder, callback);
+  PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-
-MaybeObject* StubCache::ComputeKeyedLoadArrayLength(String* name,
-                                                    JSArray* receiver) {
+Handle<Code> StubCache::ComputeKeyedLoadArrayLength(Handle<String> name,
+                                                    Handle<JSArray> receiver) {
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(Code::KEYED_LOAD_IC, CALLBACKS);
-  ASSERT(receiver->IsJSObject());
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    KeyedLoadStubCompiler compiler;
-    { MaybeObject* maybe_code = compiler.CompileLoadArrayLength(name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  KeyedLoadStubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileLoadArrayLength(name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeKeyedLoadStringLength(String* name,
-                                                     String* receiver) {
+Handle<Code> StubCache::ComputeKeyedLoadStringLength(Handle<String> name,
+                                                     Handle<String> receiver) {
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(Code::KEYED_LOAD_IC, CALLBACKS);
-  Map* map = receiver->map();
-  Object* code = map->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    KeyedLoadStubCompiler compiler;
-    { MaybeObject* maybe_code = compiler.CompileLoadStringLength(name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result = map->UpdateCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Map> map(receiver->map());
+  Handle<Object> probe(map->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  KeyedLoadStubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileLoadStringLength(name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, *name, *code));
+  Map::UpdateCodeCache(map, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeKeyedLoadFunctionPrototype(
-    String* name,
-    JSFunction* receiver) {
+Handle<Code> StubCache::ComputeKeyedLoadFunctionPrototype(
+    Handle<String> name,
+    Handle<JSFunction> receiver) {
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(Code::KEYED_LOAD_IC, CALLBACKS);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    KeyedLoadStubCompiler compiler;
-    { MaybeObject* maybe_code = compiler.CompileLoadFunctionPrototype(name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  KeyedLoadStubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileLoadFunctionPrototype(name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::KEYED_LOAD_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeStoreField(String* name,
-                                          JSObject* receiver,
+Handle<Code> StubCache::ComputeStoreField(Handle<String> name,
+                                          Handle<JSObject> receiver,
                                           int field_index,
-                                          Map* transition,
+                                          Handle<Map> transition,
                                           StrictModeFlag strict_mode) {
-  PropertyType type = (transition == NULL) ? FIELD : MAP_TRANSITION;
+  PropertyType type = (transition.is_null()) ? FIELD : MAP_TRANSITION;
   Code::Flags flags = Code::ComputeMonomorphicFlags(
       Code::STORE_IC, type, strict_mode);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    StoreStubCompiler compiler(strict_mode);
-    { MaybeObject* maybe_code =
-          compiler.CompileStoreField(receiver, field_index, transition, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::STORE_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::STORE_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  StoreStubCompiler compiler(isolate_, strict_mode);
+  Handle<Code> code =
+      compiler.CompileStoreField(receiver, field_index, transition, name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::STORE_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::STORE_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeKeyedLoadOrStoreElement(
-    JSObject* receiver,
-    bool is_store,
+Handle<Code> StubCache::ComputeKeyedLoadOrStoreElement(
+    Handle<JSObject> receiver,
+    KeyedIC::StubKind stub_kind,
     StrictModeFlag strict_mode) {
+  KeyedAccessGrowMode grow_mode =
+      KeyedIC::GetGrowModeFromStubKind(stub_kind);
+  Code::ExtraICState extra_state =
+      Code::ComputeExtraICState(grow_mode, strict_mode);
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(
-          is_store ? Code::KEYED_STORE_IC :
-                     Code::KEYED_LOAD_IC,
+          stub_kind == KeyedIC::LOAD ? Code::KEYED_LOAD_IC
+                                     : Code::KEYED_STORE_IC,
           NORMAL,
-          strict_mode);
-  String* name = is_store
-      ? isolate()->heap()->KeyedStoreElementMonomorphic_symbol()
-      : isolate()->heap()->KeyedLoadElementMonomorphic_symbol();
-  Object* maybe_code = receiver->map()->FindInCodeCache(name, flags);
-  if (!maybe_code->IsUndefined()) return Code::cast(maybe_code);
+          extra_state);
+  Handle<String> name;
+  switch (stub_kind) {
+    case KeyedIC::LOAD:
+      name = isolate()->factory()->KeyedLoadElementMonomorphic_symbol();
+      break;
+    case KeyedIC::STORE_NO_TRANSITION:
+      name = isolate()->factory()->KeyedStoreElementMonomorphic_symbol();
+      break;
+    case KeyedIC::STORE_AND_GROW_NO_TRANSITION:
+      name = isolate()->factory()->KeyedStoreAndGrowElementMonomorphic_symbol();
+      break;
+    default:
+      UNREACHABLE();
+      break;
+  }
+  Handle<Map> receiver_map(receiver->map());
+  Handle<Object> probe(receiver_map->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
 
-  MaybeObject* maybe_new_code = NULL;
-  Map* receiver_map = receiver->map();
-  if (is_store) {
-    KeyedStoreStubCompiler compiler(strict_mode);
-    maybe_new_code = compiler.CompileStoreElement(receiver_map);
+  Handle<Code> code;
+  switch (stub_kind) {
+    case KeyedIC::LOAD: {
+      KeyedLoadStubCompiler compiler(isolate_);
+      code = compiler.CompileLoadElement(receiver_map);
+      break;
+    }
+    case KeyedIC::STORE_AND_GROW_NO_TRANSITION: {
+      KeyedStoreStubCompiler compiler(isolate_, strict_mode,
+                                      ALLOW_JSARRAY_GROWTH);
+      code = compiler.CompileStoreElement(receiver_map);
+      break;
+    }
+    case KeyedIC::STORE_NO_TRANSITION: {
+      KeyedStoreStubCompiler compiler(isolate_, strict_mode,
+                                      DO_NOT_ALLOW_JSARRAY_GROWTH);
+      code = compiler.CompileStoreElement(receiver_map);
+      break;
+    }
+    default:
+      UNREACHABLE();
+      break;
+  }
+
+  ASSERT(!code.is_null());
+
+  if (stub_kind == KeyedIC::LOAD) {
+    PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, *code, 0));
   } else {
-    KeyedLoadStubCompiler compiler;
-    maybe_new_code = compiler.CompileLoadElement(receiver_map);
+    PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_STORE_IC_TAG, *code, 0));
   }
-  Code* code;
-  if (!maybe_new_code->To(&code)) return maybe_new_code;
-  if (is_store) {
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::KEYED_STORE_IC_TAG,
-                            Code::cast(code), 0));
-  } else {
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG,
-                            Code::cast(code), 0));
-  }
-  ASSERT(code->IsCode());
-  Object* result;
-  { MaybeObject* maybe_result =
-        receiver->UpdateMapCodeCache(name, Code::cast(code));
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeStoreNormal(StrictModeFlag strict_mode) {
-  return isolate_->builtins()->builtin((strict_mode == kStrictMode)
-                            ? Builtins::kStoreIC_Normal_Strict
-                            : Builtins::kStoreIC_Normal);
+Handle<Code> StubCache::ComputeStoreNormal(StrictModeFlag strict_mode) {
+  return (strict_mode == kStrictMode)
+      ? isolate_->builtins()->Builtins::StoreIC_Normal_Strict()
+      : isolate_->builtins()->Builtins::StoreIC_Normal();
 }
 
 
-MaybeObject* StubCache::ComputeStoreGlobal(String* name,
-                                           GlobalObject* receiver,
-                                           JSGlobalPropertyCell* cell,
+Handle<Code> StubCache::ComputeStoreGlobal(Handle<String> name,
+                                           Handle<GlobalObject> receiver,
+                                           Handle<JSGlobalPropertyCell> cell,
                                            StrictModeFlag strict_mode) {
   Code::Flags flags = Code::ComputeMonomorphicFlags(
       Code::STORE_IC, NORMAL, strict_mode);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    StoreStubCompiler compiler(strict_mode);
-    { MaybeObject* maybe_code =
-          compiler.CompileStoreGlobal(receiver, cell, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::STORE_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::STORE_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  StoreStubCompiler compiler(isolate_, strict_mode);
+  Handle<Code> code = compiler.CompileStoreGlobal(receiver, cell, name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::STORE_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::STORE_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeStoreCallback(
-    String* name,
-    JSObject* receiver,
-    AccessorInfo* callback,
-    StrictModeFlag strict_mode) {
+Handle<Code> StubCache::ComputeStoreCallback(Handle<String> name,
+                                             Handle<JSObject> receiver,
+                                             Handle<AccessorInfo> callback,
+                                             StrictModeFlag strict_mode) {
   ASSERT(v8::ToCData<Address>(callback->setter()) != 0);
   Code::Flags flags = Code::ComputeMonomorphicFlags(
       Code::STORE_IC, CALLBACKS, strict_mode);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    StoreStubCompiler compiler(strict_mode);
-    { MaybeObject* maybe_code =
-          compiler.CompileStoreCallback(receiver, callback, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::STORE_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::STORE_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  StoreStubCompiler compiler(isolate_, strict_mode);
+  Handle<Code> code = compiler.CompileStoreCallback(receiver, callback, name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::STORE_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::STORE_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeStoreInterceptor(
-    String* name,
-    JSObject* receiver,
-    StrictModeFlag strict_mode) {
+Handle<Code> StubCache::ComputeStoreInterceptor(Handle<String> name,
+                                                Handle<JSObject> receiver,
+                                                StrictModeFlag strict_mode) {
   Code::Flags flags = Code::ComputeMonomorphicFlags(
       Code::STORE_IC, INTERCEPTOR, strict_mode);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    StoreStubCompiler compiler(strict_mode);
-    { MaybeObject* maybe_code =
-          compiler.CompileStoreInterceptor(receiver, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate_,
-            CodeCreateEvent(Logger::STORE_IC_TAG, Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::STORE_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  StoreStubCompiler compiler(isolate_, strict_mode);
+  Handle<Code> code = compiler.CompileStoreInterceptor(receiver, name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::STORE_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::STORE_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
-
-MaybeObject* StubCache::ComputeKeyedStoreField(String* name,
-                                               JSObject* receiver,
+Handle<Code> StubCache::ComputeKeyedStoreField(Handle<String> name,
+                                               Handle<JSObject> receiver,
                                                int field_index,
-                                               Map* transition,
+                                               Handle<Map> transition,
                                                StrictModeFlag strict_mode) {
-  PropertyType type = (transition == NULL) ? FIELD : MAP_TRANSITION;
+  PropertyType type = (transition.is_null()) ? FIELD : MAP_TRANSITION;
   Code::Flags flags = Code::ComputeMonomorphicFlags(
       Code::KEYED_STORE_IC, type, strict_mode);
-  Object* code = receiver->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    KeyedStoreStubCompiler compiler(strict_mode);
-    { MaybeObject* maybe_code =
-          compiler.CompileStoreField(receiver, field_index, transition, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    PROFILE(isolate(),
-            CodeCreateEvent(Logger::KEYED_STORE_IC_TAG,
-                            Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::KEYED_STORE_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          receiver->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Handle<Object> probe(receiver->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  KeyedStoreStubCompiler compiler(isolate(), strict_mode,
+                                  DO_NOT_ALLOW_JSARRAY_GROWTH);
+  Handle<Code> code =
+      compiler.CompileStoreField(receiver, field_index, transition, name);
+  PROFILE(isolate_, CodeCreateEvent(Logger::KEYED_STORE_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::KEYED_STORE_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(receiver, name, code);
   return code;
 }
 
+
 #define CALL_LOGGER_TAG(kind, type) \
     (kind == Code::CALL_IC ? Logger::type : Logger::KEYED_##type)
 
-MaybeObject* StubCache::ComputeCallConstant(int argc,
+Handle<Code> StubCache::ComputeCallConstant(int argc,
                                             Code::Kind kind,
-                                            Code::ExtraICState extra_ic_state,
-                                            String* name,
-                                            Object* object,
-                                            JSObject* holder,
-                                            JSFunction* function) {
+                                            Code::ExtraICState extra_state,
+                                            Handle<String> name,
+                                            Handle<Object> object,
+                                            Handle<JSObject> holder,
+                                            Handle<JSFunction> function) {
   // Compute the check type and the map.
   InlineCacheHolderFlag cache_holder =
-      IC::GetCodeCacheForObject(object, holder);
-  JSObject* map_holder = IC::GetCodeCacheHolder(object, cache_holder);
+      IC::GetCodeCacheForObject(*object, *holder);
+  Handle<JSObject> map_holder(IC::GetCodeCacheHolder(*object, cache_holder));
 
   // Compute check type based on receiver/holder.
   CheckType check = RECEIVER_MAP_CHECK;
@@ -673,51 +559,36 @@
     check = BOOLEAN_CHECK;
   }
 
-  Code::Flags flags = Code::ComputeMonomorphicFlags(kind,
-                                                    CONSTANT_FUNCTION,
-                                                    extra_ic_state,
-                                                    cache_holder,
-                                                    argc);
-  Object* code = map_holder->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    // If the function hasn't been compiled yet, we cannot do it now
-    // because it may cause GC. To avoid this issue, we return an
-    // internal error which will make sure we do not update any
-    // caches.
-    if (!function->is_compiled()) return Failure::InternalError();
-    // Compile the stub - only create stubs for fully compiled functions.
-    CallStubCompiler compiler(argc, kind, extra_ic_state, cache_holder);
-    { MaybeObject* maybe_code =
-          compiler.CompileCallConstant(object, holder, function, name, check);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    Code::cast(code)->set_check_type(check);
-    ASSERT_EQ(flags, Code::cast(code)->flags());
-    PROFILE(isolate_,
-            CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_IC_TAG),
-                            Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::CALL_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          map_holder->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Code::Flags flags =
+      Code::ComputeMonomorphicFlags(kind, CONSTANT_FUNCTION, extra_state,
+                                    cache_holder, argc);
+  Handle<Object> probe(map_holder->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  CallStubCompiler compiler(isolate_, argc, kind, extra_state, cache_holder);
+  Handle<Code> code =
+      compiler.CompileCallConstant(object, holder, function, name, check);
+  code->set_check_type(check);
+  ASSERT_EQ(flags, code->flags());
+  PROFILE(isolate_,
+          CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_IC_TAG), *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::CALL_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(map_holder, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeCallField(int argc,
+Handle<Code> StubCache::ComputeCallField(int argc,
                                          Code::Kind kind,
-                                         Code::ExtraICState extra_ic_state,
-                                         String* name,
-                                         Object* object,
-                                         JSObject* holder,
+                                         Code::ExtraICState extra_state,
+                                         Handle<String> name,
+                                         Handle<Object> object,
+                                         Handle<JSObject> holder,
                                          int index) {
   // Compute the check type and the map.
   InlineCacheHolderFlag cache_holder =
-      IC::GetCodeCacheForObject(object, holder);
-  JSObject* map_holder = IC::GetCodeCacheHolder(object, cache_holder);
+      IC::GetCodeCacheForObject(*object, *holder);
+  Handle<JSObject> map_holder(IC::GetCodeCacheHolder(*object, cache_holder));
 
   // TODO(1233596): We cannot do receiver map check for non-JS objects
   // because they may be represented as immediates without a
@@ -726,47 +597,35 @@
     object = holder;
   }
 
-  Code::Flags flags = Code::ComputeMonomorphicFlags(kind,
-                                                    FIELD,
-                                                    extra_ic_state,
-                                                    cache_holder,
-                                                    argc);
-  Object* code = map_holder->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    CallStubCompiler compiler(argc, kind, extra_ic_state, cache_holder);
-    { MaybeObject* maybe_code =
-          compiler.CompileCallField(JSObject::cast(object),
-                                    holder,
-                                    index,
-                                    name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    ASSERT_EQ(flags, Code::cast(code)->flags());
-    PROFILE(isolate_,
-            CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_IC_TAG),
-                            Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::CALL_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          map_holder->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Code::Flags flags =
+      Code::ComputeMonomorphicFlags(kind, FIELD, extra_state,
+                                    cache_holder, argc);
+  Handle<Object> probe(map_holder->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  CallStubCompiler compiler(isolate_, argc, kind, extra_state, cache_holder);
+  Handle<Code> code =
+      compiler.CompileCallField(Handle<JSObject>::cast(object),
+                                holder, index, name);
+  ASSERT_EQ(flags, code->flags());
+  PROFILE(isolate_,
+          CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_IC_TAG), *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::CALL_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(map_holder, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeCallInterceptor(
-    int argc,
-    Code::Kind kind,
-    Code::ExtraICState extra_ic_state,
-    String* name,
-    Object* object,
-    JSObject* holder) {
+Handle<Code> StubCache::ComputeCallInterceptor(int argc,
+                                               Code::Kind kind,
+                                               Code::ExtraICState extra_state,
+                                               Handle<String> name,
+                                               Handle<Object> object,
+                                               Handle<JSObject> holder) {
   // Compute the check type and the map.
   InlineCacheHolderFlag cache_holder =
-      IC::GetCodeCacheForObject(object, holder);
-  JSObject* map_holder = IC::GetCodeCacheHolder(object, cache_holder);
+      IC::GetCodeCacheForObject(*object, *holder);
+  Handle<JSObject> map_holder(IC::GetCodeCacheHolder(*object, cache_holder));
 
   // TODO(1233596): We cannot do receiver map check for non-JS objects
   // because they may be represented as immediates without a
@@ -775,135 +634,60 @@
     object = holder;
   }
 
-  Code::Flags flags = Code::ComputeMonomorphicFlags(kind,
-                                                    INTERCEPTOR,
-                                                    extra_ic_state,
-                                                    cache_holder,
-                                                    argc);
-  Object* code = map_holder->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    CallStubCompiler compiler(argc, kind, extra_ic_state, cache_holder);
-    { MaybeObject* maybe_code =
-          compiler.CompileCallInterceptor(JSObject::cast(object), holder, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    ASSERT_EQ(flags, Code::cast(code)->flags());
-    PROFILE(isolate(),
-            CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_IC_TAG),
-                            Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::CALL_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          map_holder->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+  Code::Flags flags =
+      Code::ComputeMonomorphicFlags(kind, INTERCEPTOR, extra_state,
+                                    cache_holder, argc);
+  Handle<Object> probe(map_holder->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  CallStubCompiler compiler(isolate(), argc, kind, extra_state, cache_holder);
+  Handle<Code> code =
+      compiler.CompileCallInterceptor(Handle<JSObject>::cast(object),
+                                      holder, name);
+  ASSERT_EQ(flags, code->flags());
+  PROFILE(isolate(),
+          CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_IC_TAG), *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::CALL_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(map_holder, name, code);
   return code;
 }
 
 
-MaybeObject* StubCache::ComputeCallNormal(int argc,
+Handle<Code> StubCache::ComputeCallGlobal(int argc,
                                           Code::Kind kind,
-                                          Code::ExtraICState extra_ic_state,
-                                          String* name,
-                                          JSObject* receiver) {
-  Object* code;
-  { MaybeObject* maybe_code = ComputeCallNormal(argc, kind, extra_ic_state);
-    if (!maybe_code->ToObject(&code)) return maybe_code;
-  }
-  return code;
-}
-
-
-MaybeObject* StubCache::ComputeCallGlobal(int argc,
-                                          Code::Kind kind,
-                                          Code::ExtraICState extra_ic_state,
-                                          String* name,
-                                          JSObject* receiver,
-                                          GlobalObject* holder,
-                                          JSGlobalPropertyCell* cell,
-                                          JSFunction* function) {
+                                          Code::ExtraICState extra_state,
+                                          Handle<String> name,
+                                          Handle<JSObject> receiver,
+                                          Handle<GlobalObject> holder,
+                                          Handle<JSGlobalPropertyCell> cell,
+                                          Handle<JSFunction> function) {
   InlineCacheHolderFlag cache_holder =
-      IC::GetCodeCacheForObject(receiver, holder);
-  JSObject* map_holder = IC::GetCodeCacheHolder(receiver, cache_holder);
-  Code::Flags flags = Code::ComputeMonomorphicFlags(kind,
-                                                    NORMAL,
-                                                    extra_ic_state,
-                                                    cache_holder,
-                                                    argc);
-  Object* code = map_holder->map()->FindInCodeCache(name, flags);
-  if (code->IsUndefined()) {
-    // If the function hasn't been compiled yet, we cannot do it now
-    // because it may cause GC. To avoid this issue, we return an
-    // internal error which will make sure we do not update any
-    // caches.
-    if (!function->is_compiled()) return Failure::InternalError();
-    CallStubCompiler compiler(argc, kind, extra_ic_state, cache_holder);
-    { MaybeObject* maybe_code =
-          compiler.CompileCallGlobal(receiver, holder, cell, function, name);
-      if (!maybe_code->ToObject(&code)) return maybe_code;
-    }
-    ASSERT_EQ(flags, Code::cast(code)->flags());
-    PROFILE(isolate(),
-            CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_IC_TAG),
-                            Code::cast(code), name));
-    GDBJIT(AddCode(GDBJITInterface::CALL_IC, name, Code::cast(code)));
-    Object* result;
-    { MaybeObject* maybe_result =
-          map_holder->UpdateMapCodeCache(name, Code::cast(code));
-      if (!maybe_result->ToObject(&result)) return maybe_result;
-    }
-  }
+      IC::GetCodeCacheForObject(*receiver, *holder);
+  Handle<JSObject> map_holder(IC::GetCodeCacheHolder(*receiver, cache_holder));
+  Code::Flags flags =
+      Code::ComputeMonomorphicFlags(kind, NORMAL, extra_state,
+                                    cache_holder, argc);
+  Handle<Object> probe(map_holder->map()->FindInCodeCache(*name, flags));
+  if (probe->IsCode()) return Handle<Code>::cast(probe);
+
+  CallStubCompiler compiler(isolate(), argc, kind, extra_state, cache_holder);
+  Handle<Code> code =
+      compiler.CompileCallGlobal(receiver, holder, cell, function, name);
+  ASSERT_EQ(flags, code->flags());
+  PROFILE(isolate(),
+          CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_IC_TAG), *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::CALL_IC, *name, *code));
+  JSObject::UpdateMapCodeCache(map_holder, name, code);
   return code;
 }
 
 
-static Object* GetProbeValue(Isolate* isolate, Code::Flags flags) {
-  // Use raw_unchecked... so we don't get assert failures during GC.
-  UnseededNumberDictionary* dictionary =
-      isolate->heap()->raw_unchecked_non_monomorphic_cache();
-  int entry = dictionary->FindEntry(isolate, flags);
-  if (entry != -1) return dictionary->ValueAt(entry);
-  return isolate->heap()->raw_unchecked_undefined_value();
-}
-
-
-MUST_USE_RESULT static MaybeObject* ProbeCache(Isolate* isolate,
-                                               Code::Flags flags) {
-  Heap* heap = isolate->heap();
-  Object* probe = GetProbeValue(isolate, flags);
-  if (probe != heap->undefined_value()) return probe;
-  // Seed the cache with an undefined value to make sure that any
-  // generated code object can always be inserted into the cache
-  // without causing  allocation failures.
-  Object* result;
-  { MaybeObject* maybe_result =
-        heap->non_monomorphic_cache()->AtNumberPut(flags,
-                                                   heap->undefined_value());
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
-  heap->public_set_non_monomorphic_cache(
-      UnseededNumberDictionary::cast(result));
-  return probe;
-}
-
-
-static MaybeObject* FillCache(Isolate* isolate, MaybeObject* maybe_code) {
-  Object* code;
-  if (maybe_code->ToObject(&code)) {
-    if (code->IsCode()) {
-      Heap* heap = isolate->heap();
-      int entry = heap->non_monomorphic_cache()->FindEntry(
-          Code::cast(code)->flags());
-      // The entry must be present see comment in ProbeCache.
-      ASSERT(entry != -1);
-      ASSERT(heap->non_monomorphic_cache()->ValueAt(entry) ==
-             heap->undefined_value());
-      heap->non_monomorphic_cache()->ValueAtPut(entry, code);
-      CHECK(GetProbeValue(isolate, Code::cast(code)->flags()) == code);
-    }
-  }
-  return maybe_code;
+static void FillCache(Isolate* isolate, Handle<Code> code) {
+  Handle<UnseededNumberDictionary> dictionary =
+      UnseededNumberDictionary::Set(isolate->factory()->non_monomorphic_cache(),
+                                    code->flags(),
+                                    code);
+  isolate->heap()->public_set_non_monomorphic_cache(*dictionary);
 }
 
 
@@ -913,209 +697,200 @@
   Code::ExtraICState extra_state =
       CallICBase::StringStubState::encode(DEFAULT_STRING_STUB) |
       CallICBase::Contextual::encode(mode == RelocInfo::CODE_TARGET_CONTEXT);
-  Code::Flags flags = Code::ComputeFlags(kind,
-                                         UNINITIALIZED,
-                                         extra_state,
-                                         NORMAL,
-                                         argc);
-  Object* result = ProbeCache(isolate(), flags)->ToObjectUnchecked();
-  ASSERT(result != heap()->undefined_value());
+  Code::Flags flags =
+      Code::ComputeFlags(kind, UNINITIALIZED, extra_state, NORMAL, argc);
+
+  // Use raw_unchecked... so we don't get assert failures during GC.
+  UnseededNumberDictionary* dictionary =
+      isolate()->heap()->raw_unchecked_non_monomorphic_cache();
+  int entry = dictionary->FindEntry(isolate(), flags);
+  ASSERT(entry != -1);
+  Object* code = dictionary->ValueAt(entry);
   // This might be called during the marking phase of the collector
   // hence the unchecked cast.
-  return reinterpret_cast<Code*>(result);
+  return reinterpret_cast<Code*>(code);
 }
 
 
-MaybeObject* StubCache::ComputeCallInitialize(int argc,
+Handle<Code> StubCache::ComputeCallInitialize(int argc,
                                               RelocInfo::Mode mode,
                                               Code::Kind kind) {
   Code::ExtraICState extra_state =
       CallICBase::StringStubState::encode(DEFAULT_STRING_STUB) |
       CallICBase::Contextual::encode(mode == RelocInfo::CODE_TARGET_CONTEXT);
-  Code::Flags flags = Code::ComputeFlags(kind,
-                                         UNINITIALIZED,
-                                         extra_state,
-                                         NORMAL,
-                                         argc);
-  Object* probe;
-  { MaybeObject* maybe_probe = ProbeCache(isolate_, flags);
-    if (!maybe_probe->ToObject(&probe)) return maybe_probe;
-  }
-  if (!probe->IsUndefined()) return probe;
-  StubCompiler compiler;
-  return FillCache(isolate_, compiler.CompileCallInitialize(flags));
+  Code::Flags flags =
+      Code::ComputeFlags(kind, UNINITIALIZED, extra_state, NORMAL, argc);
+  Handle<UnseededNumberDictionary> cache =
+      isolate_->factory()->non_monomorphic_cache();
+  int entry = cache->FindEntry(isolate_, flags);
+  if (entry != -1) return Handle<Code>(Code::cast(cache->ValueAt(entry)));
+
+  StubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileCallInitialize(flags);
+  FillCache(isolate_, code);
+  return code;
 }
 
 
-Handle<Code> StubCache::ComputeCallInitialize(int argc,
-                                              RelocInfo::Mode mode) {
-  CALL_HEAP_FUNCTION(isolate_,
-                     ComputeCallInitialize(argc, mode, Code::CALL_IC),
-                     Code);
+Handle<Code> StubCache::ComputeCallInitialize(int argc, RelocInfo::Mode mode) {
+  return ComputeCallInitialize(argc, mode, Code::CALL_IC);
 }
 
 
 Handle<Code> StubCache::ComputeKeyedCallInitialize(int argc) {
-  CALL_HEAP_FUNCTION(
-      isolate_,
-      ComputeCallInitialize(argc, RelocInfo::CODE_TARGET, Code::KEYED_CALL_IC),
-      Code);
+  return ComputeCallInitialize(argc, RelocInfo::CODE_TARGET,
+                               Code::KEYED_CALL_IC);
 }
 
 
-MaybeObject* StubCache::ComputeCallPreMonomorphic(
+Handle<Code> StubCache::ComputeCallPreMonomorphic(
     int argc,
     Code::Kind kind,
-    Code::ExtraICState extra_ic_state) {
-  Code::Flags flags = Code::ComputeFlags(kind,
-                                         PREMONOMORPHIC,
-                                         extra_ic_state,
-                                         NORMAL,
-                                         argc);
-  Object* probe;
-  { MaybeObject* maybe_probe = ProbeCache(isolate_, flags);
-    if (!maybe_probe->ToObject(&probe)) return maybe_probe;
-  }
-  if (!probe->IsUndefined()) return probe;
-  StubCompiler compiler;
-  return FillCache(isolate_, compiler.CompileCallPreMonomorphic(flags));
+    Code::ExtraICState extra_state) {
+  Code::Flags flags =
+      Code::ComputeFlags(kind, PREMONOMORPHIC, extra_state, NORMAL, argc);
+  Handle<UnseededNumberDictionary> cache =
+      isolate_->factory()->non_monomorphic_cache();
+  int entry = cache->FindEntry(isolate_, flags);
+  if (entry != -1) return Handle<Code>(Code::cast(cache->ValueAt(entry)));
+
+  StubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileCallPreMonomorphic(flags);
+  FillCache(isolate_, code);
+  return code;
 }
 
 
-MaybeObject* StubCache::ComputeCallNormal(int argc,
+Handle<Code> StubCache::ComputeCallNormal(int argc,
                                           Code::Kind kind,
-                                          Code::ExtraICState extra_ic_state) {
-  Code::Flags flags = Code::ComputeFlags(kind,
-                                         MONOMORPHIC,
-                                         extra_ic_state,
-                                         NORMAL,
-                                         argc);
-  Object* probe;
-  { MaybeObject* maybe_probe = ProbeCache(isolate_, flags);
-    if (!maybe_probe->ToObject(&probe)) return maybe_probe;
-  }
-  if (!probe->IsUndefined()) return probe;
-  StubCompiler compiler;
-  return FillCache(isolate_, compiler.CompileCallNormal(flags));
+                                          Code::ExtraICState extra_state) {
+  Code::Flags flags =
+      Code::ComputeFlags(kind, MONOMORPHIC, extra_state, NORMAL, argc);
+  Handle<UnseededNumberDictionary> cache =
+      isolate_->factory()->non_monomorphic_cache();
+  int entry = cache->FindEntry(isolate_, flags);
+  if (entry != -1) return Handle<Code>(Code::cast(cache->ValueAt(entry)));
+
+  StubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileCallNormal(flags);
+  FillCache(isolate_, code);
+  return code;
 }
 
 
-MaybeObject* StubCache::ComputeCallArguments(int argc, Code::Kind kind) {
+Handle<Code> StubCache::ComputeCallArguments(int argc, Code::Kind kind) {
   ASSERT(kind == Code::KEYED_CALL_IC);
-  Code::Flags flags = Code::ComputeFlags(kind,
-                                         MEGAMORPHIC,
-                                         Code::kNoExtraICState,
-                                         NORMAL,
-                                         argc);
-  Object* probe;
-  { MaybeObject* maybe_probe = ProbeCache(isolate_, flags);
-    if (!maybe_probe->ToObject(&probe)) return maybe_probe;
-  }
-  if (!probe->IsUndefined()) return probe;
-  StubCompiler compiler;
-  return FillCache(isolate_, compiler.CompileCallArguments(flags));
+  Code::Flags flags =
+      Code::ComputeFlags(kind, MEGAMORPHIC, Code::kNoExtraICState,
+                         NORMAL, argc);
+  Handle<UnseededNumberDictionary> cache =
+      isolate_->factory()->non_monomorphic_cache();
+  int entry = cache->FindEntry(isolate_, flags);
+  if (entry != -1) return Handle<Code>(Code::cast(cache->ValueAt(entry)));
+
+  StubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileCallArguments(flags);
+  FillCache(isolate_, code);
+  return code;
 }
 
 
-MaybeObject* StubCache::ComputeCallMegamorphic(
+Handle<Code> StubCache::ComputeCallMegamorphic(
     int argc,
     Code::Kind kind,
-    Code::ExtraICState extra_ic_state) {
-  Code::Flags flags = Code::ComputeFlags(kind,
-                                         MEGAMORPHIC,
-                                         extra_ic_state,
-                                         NORMAL,
-                                         argc);
-  Object* probe;
-  { MaybeObject* maybe_probe = ProbeCache(isolate_, flags);
-    if (!maybe_probe->ToObject(&probe)) return maybe_probe;
-  }
-  if (!probe->IsUndefined()) return probe;
-  StubCompiler compiler;
-  return FillCache(isolate_, compiler.CompileCallMegamorphic(flags));
+    Code::ExtraICState extra_state) {
+  Code::Flags flags =
+      Code::ComputeFlags(kind, MEGAMORPHIC, extra_state,
+                         NORMAL, argc);
+  Handle<UnseededNumberDictionary> cache =
+      isolate_->factory()->non_monomorphic_cache();
+  int entry = cache->FindEntry(isolate_, flags);
+  if (entry != -1) return Handle<Code>(Code::cast(cache->ValueAt(entry)));
+
+  StubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileCallMegamorphic(flags);
+  FillCache(isolate_, code);
+  return code;
 }
 
 
-MaybeObject* StubCache::ComputeCallMiss(int argc,
+Handle<Code> StubCache::ComputeCallMiss(int argc,
                                         Code::Kind kind,
-                                        Code::ExtraICState extra_ic_state) {
+                                        Code::ExtraICState extra_state) {
   // MONOMORPHIC_PROTOTYPE_FAILURE state is used to make sure that miss stubs
   // and monomorphic stubs are not mixed up together in the stub cache.
-  Code::Flags flags = Code::ComputeFlags(kind,
-                                         MONOMORPHIC_PROTOTYPE_FAILURE,
-                                         extra_ic_state,
-                                         NORMAL,
-                                         argc,
-                                         OWN_MAP);
-  Object* probe;
-  { MaybeObject* maybe_probe = ProbeCache(isolate_, flags);
-    if (!maybe_probe->ToObject(&probe)) return maybe_probe;
-  }
-  if (!probe->IsUndefined()) return probe;
-  StubCompiler compiler;
-  return FillCache(isolate_, compiler.CompileCallMiss(flags));
+  Code::Flags flags =
+      Code::ComputeFlags(kind, MONOMORPHIC_PROTOTYPE_FAILURE, extra_state,
+                         NORMAL, argc, OWN_MAP);
+  Handle<UnseededNumberDictionary> cache =
+      isolate_->factory()->non_monomorphic_cache();
+  int entry = cache->FindEntry(isolate_, flags);
+  if (entry != -1) return Handle<Code>(Code::cast(cache->ValueAt(entry)));
+
+  StubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileCallMiss(flags);
+  FillCache(isolate_, code);
+  return code;
 }
 
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
-MaybeObject* StubCache::ComputeCallDebugBreak(
-    int argc,
-    Code::Kind kind) {
+Handle<Code> StubCache::ComputeCallDebugBreak(int argc,
+                                              Code::Kind kind) {
   // Extra IC state is irrelevant for debug break ICs. They jump to
   // the actual call ic to carry out the work.
-  Code::Flags flags = Code::ComputeFlags(kind,
-                                         DEBUG_BREAK,
-                                         Code::kNoExtraICState,
-                                         NORMAL,
-                                         argc);
-  Object* probe;
-  { MaybeObject* maybe_probe = ProbeCache(isolate_, flags);
-    if (!maybe_probe->ToObject(&probe)) return maybe_probe;
-  }
-  if (!probe->IsUndefined()) return probe;
-  StubCompiler compiler;
-  return FillCache(isolate_, compiler.CompileCallDebugBreak(flags));
+  Code::Flags flags =
+      Code::ComputeFlags(kind, DEBUG_BREAK, Code::kNoExtraICState,
+                         NORMAL, argc);
+  Handle<UnseededNumberDictionary> cache =
+      isolate_->factory()->non_monomorphic_cache();
+  int entry = cache->FindEntry(isolate_, flags);
+  if (entry != -1) return Handle<Code>(Code::cast(cache->ValueAt(entry)));
+
+  StubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileCallDebugBreak(flags);
+  FillCache(isolate_, code);
+  return code;
 }
 
 
-MaybeObject* StubCache::ComputeCallDebugPrepareStepIn(
-    int argc,
-    Code::Kind kind) {
+Handle<Code> StubCache::ComputeCallDebugPrepareStepIn(int argc,
+                                                      Code::Kind kind) {
   // Extra IC state is irrelevant for debug break ICs. They jump to
   // the actual call ic to carry out the work.
-  Code::Flags flags = Code::ComputeFlags(kind,
-                                         DEBUG_PREPARE_STEP_IN,
-                                         Code::kNoExtraICState,
-                                         NORMAL,
-                                         argc);
-  Object* probe;
-  { MaybeObject* maybe_probe = ProbeCache(isolate_, flags);
-    if (!maybe_probe->ToObject(&probe)) return maybe_probe;
-  }
-  if (!probe->IsUndefined()) return probe;
-  StubCompiler compiler;
-  return FillCache(isolate_, compiler.CompileCallDebugPrepareStepIn(flags));
+  Code::Flags flags =
+      Code::ComputeFlags(kind, DEBUG_PREPARE_STEP_IN, Code::kNoExtraICState,
+                         NORMAL, argc);
+  Handle<UnseededNumberDictionary> cache =
+      isolate_->factory()->non_monomorphic_cache();
+  int entry = cache->FindEntry(isolate_, flags);
+  if (entry != -1) return Handle<Code>(Code::cast(cache->ValueAt(entry)));
+
+  StubCompiler compiler(isolate_);
+  Handle<Code> code = compiler.CompileCallDebugPrepareStepIn(flags);
+  FillCache(isolate_, code);
+  return code;
 }
 #endif
 
 
 void StubCache::Clear() {
+  Code* empty = isolate_->builtins()->builtin(Builtins::kIllegal);
   for (int i = 0; i < kPrimaryTableSize; i++) {
     primary_[i].key = heap()->empty_string();
-    primary_[i].value = isolate_->builtins()->builtin(
-        Builtins::kIllegal);
+    primary_[i].value = empty;
   }
   for (int j = 0; j < kSecondaryTableSize; j++) {
     secondary_[j].key = heap()->empty_string();
-    secondary_[j].value = isolate_->builtins()->builtin(
-        Builtins::kIllegal);
+    secondary_[j].value = empty;
   }
 }
 
 
 void StubCache::CollectMatchingMaps(SmallMapList* types,
                                     String* name,
-                                    Code::Flags flags) {
+                                    Code::Flags flags,
+                                    Handle<Context> global_context) {
   for (int i = 0; i < kPrimaryTableSize; i++) {
     if (primary_[i].key == name) {
       Map* map = primary_[i].value->FindFirstMap();
@@ -1124,7 +899,8 @@
       if (map == NULL) continue;
 
       int offset = PrimaryOffset(name, flags, map);
-      if (entry(primary_, offset) == &primary_[i]) {
+      if (entry(primary_, offset) == &primary_[i] &&
+          !TypeFeedbackOracle::CanRetainOtherContext(map, *global_context)) {
         types->Add(Handle<Map>(map));
       }
     }
@@ -1147,7 +923,8 @@
 
       // Lookup in secondary table and add matches.
       int offset = SecondaryOffset(name, flags, primary_offset);
-      if (entry(secondary_, offset) == &secondary_[i]) {
+      if (entry(secondary_, offset) == &secondary_[i] &&
+          !TypeFeedbackOracle::CanRetainOtherContext(map, *global_context)) {
         types->Add(Handle<Map>(map));
       }
     }
@@ -1342,8 +1119,8 @@
   JSObject* recv = JSObject::cast(args[0]);
   String* name = String::cast(args[1]);
   Object* value = args[2];
+  ASSERT(args.smi_at(3) == kStrictMode || args.smi_at(3) == kNonStrictMode);
   StrictModeFlag strict_mode = static_cast<StrictModeFlag>(args.smi_at(3));
-  ASSERT(strict_mode == kStrictMode || strict_mode == kNonStrictMode);
   ASSERT(recv->HasNamedInterceptor());
   PropertyAttributes attr = NONE;
   MaybeObject* result = recv->SetPropertyWithInterceptor(
@@ -1360,62 +1137,47 @@
 }
 
 
-MaybeObject* StubCompiler::CompileCallInitialize(Code::Flags flags) {
-  HandleScope scope(isolate());
+Handle<Code> StubCompiler::CompileCallInitialize(Code::Flags flags) {
   int argc = Code::ExtractArgumentsCountFromFlags(flags);
   Code::Kind kind = Code::ExtractKindFromFlags(flags);
-  Code::ExtraICState extra_ic_state = Code::ExtractExtraICStateFromFlags(flags);
+  Code::ExtraICState extra_state = Code::ExtractExtraICStateFromFlags(flags);
   if (kind == Code::CALL_IC) {
-    CallIC::GenerateInitialize(masm(), argc, extra_ic_state);
+    CallIC::GenerateInitialize(masm(), argc, extra_state);
   } else {
     KeyedCallIC::GenerateInitialize(masm(), argc);
   }
-  Object* result;
-  { MaybeObject* maybe_result =
-        GetCodeWithFlags(flags, "CompileCallInitialize");
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
+  Handle<Code> code = GetCodeWithFlags(flags, "CompileCallInitialize");
   isolate()->counters()->call_initialize_stubs()->Increment();
-  Code* code = Code::cast(result);
-  USE(code);
   PROFILE(isolate(),
           CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_INITIALIZE_TAG),
-                          code, code->arguments_count()));
-  GDBJIT(AddCode(GDBJITInterface::CALL_INITIALIZE, Code::cast(code)));
-  return result;
+                          *code, code->arguments_count()));
+  GDBJIT(AddCode(GDBJITInterface::CALL_INITIALIZE, *code));
+  return code;
 }
 
 
-MaybeObject* StubCompiler::CompileCallPreMonomorphic(Code::Flags flags) {
-  HandleScope scope(isolate());
+Handle<Code> StubCompiler::CompileCallPreMonomorphic(Code::Flags flags) {
   int argc = Code::ExtractArgumentsCountFromFlags(flags);
   // The code of the PreMonomorphic stub is the same as the code
   // of the Initialized stub.  They just differ on the code object flags.
   Code::Kind kind = Code::ExtractKindFromFlags(flags);
-  Code::ExtraICState extra_ic_state = Code::ExtractExtraICStateFromFlags(flags);
+  Code::ExtraICState extra_state = Code::ExtractExtraICStateFromFlags(flags);
   if (kind == Code::CALL_IC) {
-    CallIC::GenerateInitialize(masm(), argc, extra_ic_state);
+    CallIC::GenerateInitialize(masm(), argc, extra_state);
   } else {
     KeyedCallIC::GenerateInitialize(masm(), argc);
   }
-  Object* result;
-  { MaybeObject* maybe_result =
-        GetCodeWithFlags(flags, "CompileCallPreMonomorphic");
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
+  Handle<Code> code = GetCodeWithFlags(flags, "CompileCallPreMonomorphic");
   isolate()->counters()->call_premonomorphic_stubs()->Increment();
-  Code* code = Code::cast(result);
-  USE(code);
   PROFILE(isolate(),
           CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_PRE_MONOMORPHIC_TAG),
-                          code, code->arguments_count()));
-  GDBJIT(AddCode(GDBJITInterface::CALL_PRE_MONOMORPHIC, Code::cast(code)));
-  return result;
+                          *code, code->arguments_count()));
+  GDBJIT(AddCode(GDBJITInterface::CALL_PRE_MONOMORPHIC, *code));
+  return code;
 }
 
 
-MaybeObject* StubCompiler::CompileCallNormal(Code::Flags flags) {
-  HandleScope scope(isolate());
+Handle<Code> StubCompiler::CompileCallNormal(Code::Flags flags) {
   int argc = Code::ExtractArgumentsCountFromFlags(flags);
   Code::Kind kind = Code::ExtractKindFromFlags(flags);
   if (kind == Code::CALL_IC) {
@@ -1426,116 +1188,82 @@
   } else {
     KeyedCallIC::GenerateNormal(masm(), argc);
   }
-  Object* result;
-  { MaybeObject* maybe_result = GetCodeWithFlags(flags, "CompileCallNormal");
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
+  Handle<Code> code = GetCodeWithFlags(flags, "CompileCallNormal");
   isolate()->counters()->call_normal_stubs()->Increment();
-  Code* code = Code::cast(result);
-  USE(code);
   PROFILE(isolate(),
           CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_NORMAL_TAG),
-                          code, code->arguments_count()));
-  GDBJIT(AddCode(GDBJITInterface::CALL_NORMAL, Code::cast(code)));
-  return result;
+                          *code, code->arguments_count()));
+  GDBJIT(AddCode(GDBJITInterface::CALL_NORMAL, *code));
+  return code;
 }
 
 
-MaybeObject* StubCompiler::CompileCallMegamorphic(Code::Flags flags) {
-  HandleScope scope(isolate());
+Handle<Code> StubCompiler::CompileCallMegamorphic(Code::Flags flags) {
   int argc = Code::ExtractArgumentsCountFromFlags(flags);
   Code::Kind kind = Code::ExtractKindFromFlags(flags);
-  Code::ExtraICState extra_ic_state = Code::ExtractExtraICStateFromFlags(flags);
+  Code::ExtraICState extra_state = Code::ExtractExtraICStateFromFlags(flags);
   if (kind == Code::CALL_IC) {
-    CallIC::GenerateMegamorphic(masm(), argc, extra_ic_state);
+    CallIC::GenerateMegamorphic(masm(), argc, extra_state);
   } else {
     KeyedCallIC::GenerateMegamorphic(masm(), argc);
   }
-  Object* result;
-  { MaybeObject* maybe_result =
-        GetCodeWithFlags(flags, "CompileCallMegamorphic");
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
+  Handle<Code> code = GetCodeWithFlags(flags, "CompileCallMegamorphic");
   isolate()->counters()->call_megamorphic_stubs()->Increment();
-  Code* code = Code::cast(result);
-  USE(code);
   PROFILE(isolate(),
           CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_MEGAMORPHIC_TAG),
-                          code, code->arguments_count()));
-  GDBJIT(AddCode(GDBJITInterface::CALL_MEGAMORPHIC, Code::cast(code)));
-  return result;
+                          *code, code->arguments_count()));
+  GDBJIT(AddCode(GDBJITInterface::CALL_MEGAMORPHIC, *code));
+  return code;
 }
 
 
-MaybeObject* StubCompiler::CompileCallArguments(Code::Flags flags) {
-  HandleScope scope(isolate());
+Handle<Code> StubCompiler::CompileCallArguments(Code::Flags flags) {
   int argc = Code::ExtractArgumentsCountFromFlags(flags);
   KeyedCallIC::GenerateNonStrictArguments(masm(), argc);
-  Code::Kind kind = Code::ExtractKindFromFlags(flags);
-  Object* result;
-  { MaybeObject* maybe_result =
-        GetCodeWithFlags(flags, "CompileCallArguments");
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
-  Code* code = Code::cast(result);
-  USE(code);
+  Handle<Code> code = GetCodeWithFlags(flags, "CompileCallArguments");
   PROFILE(isolate(),
-          CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_MEGAMORPHIC_TAG),
-                          code, code->arguments_count()));
-  GDBJIT(AddCode(GDBJITInterface::CALL_MEGAMORPHIC, Code::cast(code)));
-  return result;
+          CodeCreateEvent(CALL_LOGGER_TAG(Code::ExtractKindFromFlags(flags),
+                                          CALL_MEGAMORPHIC_TAG),
+                          *code, code->arguments_count()));
+  GDBJIT(AddCode(GDBJITInterface::CALL_MEGAMORPHIC, *code));
+  return code;
 }
 
 
-MaybeObject* StubCompiler::CompileCallMiss(Code::Flags flags) {
-  HandleScope scope(isolate());
+Handle<Code> StubCompiler::CompileCallMiss(Code::Flags flags) {
   int argc = Code::ExtractArgumentsCountFromFlags(flags);
   Code::Kind kind = Code::ExtractKindFromFlags(flags);
-  Code::ExtraICState extra_ic_state = Code::ExtractExtraICStateFromFlags(flags);
+  Code::ExtraICState extra_state = Code::ExtractExtraICStateFromFlags(flags);
   if (kind == Code::CALL_IC) {
-    CallIC::GenerateMiss(masm(), argc, extra_ic_state);
+    CallIC::GenerateMiss(masm(), argc, extra_state);
   } else {
     KeyedCallIC::GenerateMiss(masm(), argc);
   }
-  Object* result;
-  { MaybeObject* maybe_result = GetCodeWithFlags(flags, "CompileCallMiss");
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
+  Handle<Code> code = GetCodeWithFlags(flags, "CompileCallMiss");
   isolate()->counters()->call_megamorphic_stubs()->Increment();
-  Code* code = Code::cast(result);
-  USE(code);
   PROFILE(isolate(),
           CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_MISS_TAG),
-                          code, code->arguments_count()));
-  GDBJIT(AddCode(GDBJITInterface::CALL_MISS, Code::cast(code)));
-  return result;
+                          *code, code->arguments_count()));
+  GDBJIT(AddCode(GDBJITInterface::CALL_MISS, *code));
+  return code;
 }
 
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
-MaybeObject* StubCompiler::CompileCallDebugBreak(Code::Flags flags) {
-  HandleScope scope(isolate());
+Handle<Code> StubCompiler::CompileCallDebugBreak(Code::Flags flags) {
   Debug::GenerateCallICDebugBreak(masm());
-  Object* result;
-  { MaybeObject* maybe_result =
-        GetCodeWithFlags(flags, "CompileCallDebugBreak");
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
-  Code* code = Code::cast(result);
-  USE(code);
-  Code::Kind kind = Code::ExtractKindFromFlags(flags);
-  USE(kind);
+  Handle<Code> code = GetCodeWithFlags(flags, "CompileCallDebugBreak");
   PROFILE(isolate(),
-          CodeCreateEvent(CALL_LOGGER_TAG(kind, CALL_DEBUG_BREAK_TAG),
-                          code, code->arguments_count()));
-  return result;
+          CodeCreateEvent(CALL_LOGGER_TAG(Code::ExtractKindFromFlags(flags),
+                                          CALL_DEBUG_BREAK_TAG),
+                          *code, code->arguments_count()));
+  return code;
 }
 
 
-MaybeObject* StubCompiler::CompileCallDebugPrepareStepIn(Code::Flags flags) {
-  HandleScope scope(isolate());
-  // Use the same code for the the step in preparations as we do for
-  // the miss case.
+Handle<Code> StubCompiler::CompileCallDebugPrepareStepIn(Code::Flags flags) {
+  // Use the same code for the the step in preparations as we do for the
+  // miss case.
   int argc = Code::ExtractArgumentsCountFromFlags(flags);
   Code::Kind kind = Code::ExtractKindFromFlags(flags);
   if (kind == Code::CALL_IC) {
@@ -1544,133 +1272,96 @@
   } else {
     KeyedCallIC::GenerateMiss(masm(), argc);
   }
-  Object* result;
-  { MaybeObject* maybe_result =
-        GetCodeWithFlags(flags, "CompileCallDebugPrepareStepIn");
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
-  Code* code = Code::cast(result);
-  USE(code);
+  Handle<Code> code = GetCodeWithFlags(flags, "CompileCallDebugPrepareStepIn");
   PROFILE(isolate(),
           CodeCreateEvent(
               CALL_LOGGER_TAG(kind, CALL_DEBUG_PREPARE_STEP_IN_TAG),
-              code,
+              *code,
               code->arguments_count()));
-  return result;
+  return code;
 }
-#endif
+#endif  // ENABLE_DEBUGGER_SUPPORT
 
 #undef CALL_LOGGER_TAG
 
-MaybeObject* StubCompiler::GetCodeWithFlags(Code::Flags flags,
-                                            const char* name) {
-  // Check for allocation failures during stub compilation.
-  if (failure_->IsFailure()) return failure_;
 
+Handle<Code> StubCompiler::GetCodeWithFlags(Code::Flags flags,
+                                            const char* name) {
   // Create code object in the heap.
   CodeDesc desc;
   masm_.GetCode(&desc);
-  MaybeObject* result = heap()->CreateCode(desc, flags, masm_.CodeObject());
+  Handle<Code> code = factory()->NewCode(desc, flags, masm_.CodeObject());
 #ifdef ENABLE_DISASSEMBLER
-  if (FLAG_print_code_stubs && !result->IsFailure()) {
-    Code::cast(result->ToObjectUnchecked())->Disassemble(name);
-  }
+  if (FLAG_print_code_stubs) code->Disassemble(name);
 #endif
-  return result;
+  return code;
 }
 
 
-MaybeObject* StubCompiler::GetCodeWithFlags(Code::Flags flags, String* name) {
-  if (FLAG_print_code_stubs && (name != NULL)) {
-    return GetCodeWithFlags(flags, *name->ToCString());
-  }
-  return GetCodeWithFlags(flags, reinterpret_cast<char*>(NULL));
+Handle<Code> StubCompiler::GetCodeWithFlags(Code::Flags flags,
+                                            Handle<String> name) {
+  return (FLAG_print_code_stubs && !name.is_null())
+      ? GetCodeWithFlags(flags, *name->ToCString())
+      : GetCodeWithFlags(flags, reinterpret_cast<char*>(NULL));
 }
 
 
-void StubCompiler::LookupPostInterceptor(JSObject* holder,
-                                         String* name,
+void StubCompiler::LookupPostInterceptor(Handle<JSObject> holder,
+                                         Handle<String> name,
                                          LookupResult* lookup) {
-  holder->LocalLookupRealNamedProperty(name, lookup);
-  if (!lookup->IsProperty()) {
-    lookup->NotFound();
-    Object* proto = holder->GetPrototype();
-    if (!proto->IsNull()) {
-      proto->Lookup(name, lookup);
-    }
-  }
+  holder->LocalLookupRealNamedProperty(*name, lookup);
+  if (lookup->IsProperty()) return;
+
+  lookup->NotFound();
+  if (holder->GetPrototype()->IsNull()) return;
+
+  holder->GetPrototype()->Lookup(*name, lookup);
 }
 
 
-
-MaybeObject* LoadStubCompiler::GetCode(PropertyType type, String* name) {
+Handle<Code> LoadStubCompiler::GetCode(PropertyType type, Handle<String> name) {
   Code::Flags flags = Code::ComputeMonomorphicFlags(Code::LOAD_IC, type);
-  MaybeObject* result = GetCodeWithFlags(flags, name);
-  if (!result->IsFailure()) {
-    PROFILE(isolate(),
-            CodeCreateEvent(Logger::LOAD_IC_TAG,
-                            Code::cast(result->ToObjectUnchecked()),
-                            name));
-    GDBJIT(AddCode(GDBJITInterface::LOAD_IC,
-                   name,
-                   Code::cast(result->ToObjectUnchecked())));
-  }
-  return result;
+  Handle<Code> code = GetCodeWithFlags(flags, name);
+  PROFILE(isolate(), CodeCreateEvent(Logger::LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::LOAD_IC, *name, *code));
+  return code;
 }
 
 
-MaybeObject* KeyedLoadStubCompiler::GetCode(PropertyType type,
-                                            String* name,
+Handle<Code> KeyedLoadStubCompiler::GetCode(PropertyType type,
+                                            Handle<String> name,
                                             InlineCacheState state) {
   Code::Flags flags = Code::ComputeFlags(
       Code::KEYED_LOAD_IC, state, Code::kNoExtraICState, type);
-  MaybeObject* result = GetCodeWithFlags(flags, name);
-  if (!result->IsFailure()) {
-    PROFILE(isolate(),
-            CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG,
-                            Code::cast(result->ToObjectUnchecked()),
-                            name));
-    GDBJIT(AddCode(GDBJITInterface::LOAD_IC,
-                   name,
-                   Code::cast(result->ToObjectUnchecked())));
-  }
-  return result;
+  Handle<Code> code = GetCodeWithFlags(flags, name);
+  PROFILE(isolate(), CodeCreateEvent(Logger::KEYED_LOAD_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::LOAD_IC, *name, *code));
+  return code;
 }
 
 
-MaybeObject* StoreStubCompiler::GetCode(PropertyType type, String* name) {
+Handle<Code> StoreStubCompiler::GetCode(PropertyType type,
+                                        Handle<String> name) {
   Code::Flags flags =
       Code::ComputeMonomorphicFlags(Code::STORE_IC, type, strict_mode_);
-  MaybeObject* result = GetCodeWithFlags(flags, name);
-  if (!result->IsFailure()) {
-    PROFILE(isolate(),
-            CodeCreateEvent(Logger::STORE_IC_TAG,
-                            Code::cast(result->ToObjectUnchecked()),
-                            name));
-    GDBJIT(AddCode(GDBJITInterface::STORE_IC,
-                   name,
-                   Code::cast(result->ToObjectUnchecked())));
-  }
-  return result;
+  Handle<Code> code = GetCodeWithFlags(flags, name);
+  PROFILE(isolate(), CodeCreateEvent(Logger::STORE_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::STORE_IC, *name, *code));
+  return code;
 }
 
 
-MaybeObject* KeyedStoreStubCompiler::GetCode(PropertyType type,
-                                             String* name,
+Handle<Code> KeyedStoreStubCompiler::GetCode(PropertyType type,
+                                             Handle<String> name,
                                              InlineCacheState state) {
+  Code::ExtraICState extra_state =
+      Code::ComputeExtraICState(grow_mode_, strict_mode_);
   Code::Flags flags =
-      Code::ComputeFlags(Code::KEYED_STORE_IC, state, strict_mode_, type);
-  MaybeObject* result = GetCodeWithFlags(flags, name);
-  if (!result->IsFailure()) {
-    PROFILE(isolate(),
-            CodeCreateEvent(Logger::KEYED_STORE_IC_TAG,
-                            Code::cast(result->ToObjectUnchecked()),
-                            name));
-    GDBJIT(AddCode(GDBJITInterface::KEYED_STORE_IC,
-                   name,
-                   Code::cast(result->ToObjectUnchecked())));
-  }
-  return result;
+      Code::ComputeFlags(Code::KEYED_STORE_IC, state, extra_state, type);
+  Handle<Code> code = GetCodeWithFlags(flags, name);
+  PROFILE(isolate(), CodeCreateEvent(Logger::KEYED_STORE_IC_TAG, *code, *name));
+  GDBJIT(AddCode(GDBJITInterface::KEYED_STORE_IC, *name, *code));
+  return code;
 }
 
 
@@ -1680,50 +1371,49 @@
 }
 
 
-CallStubCompiler::CallStubCompiler(int argc,
+CallStubCompiler::CallStubCompiler(Isolate* isolate,
+                                   int argc,
                                    Code::Kind kind,
-                                   Code::ExtraICState extra_ic_state,
+                                   Code::ExtraICState extra_state,
                                    InlineCacheHolderFlag cache_holder)
-    : arguments_(argc),
+    : StubCompiler(isolate),
+      arguments_(argc),
       kind_(kind),
-      extra_ic_state_(extra_ic_state),
+      extra_state_(extra_state),
       cache_holder_(cache_holder) {
 }
 
 
-bool CallStubCompiler::HasCustomCallGenerator(JSFunction* function) {
-  SharedFunctionInfo* info = function->shared();
-  if (info->HasBuiltinFunctionId()) {
-    BuiltinFunctionId id = info->builtin_function_id();
+bool CallStubCompiler::HasCustomCallGenerator(Handle<JSFunction> function) {
+  if (function->shared()->HasBuiltinFunctionId()) {
+    BuiltinFunctionId id = function->shared()->builtin_function_id();
 #define CALL_GENERATOR_CASE(name) if (id == k##name) return true;
     CUSTOM_CALL_IC_GENERATORS(CALL_GENERATOR_CASE)
 #undef CALL_GENERATOR_CASE
   }
+
   CallOptimization optimization(function);
-  if (optimization.is_simple_api_call()) {
-    return true;
-  }
-  return false;
+  return optimization.is_simple_api_call();
 }
 
 
-MaybeObject* CallStubCompiler::CompileCustomCall(Object* object,
-                                                 JSObject* holder,
-                                                 JSGlobalPropertyCell* cell,
-                                                 JSFunction* function,
-                                                 String* fname) {
+Handle<Code> CallStubCompiler::CompileCustomCall(
+    Handle<Object> object,
+    Handle<JSObject> holder,
+    Handle<JSGlobalPropertyCell> cell,
+    Handle<JSFunction> function,
+    Handle<String> fname) {
   ASSERT(HasCustomCallGenerator(function));
 
-  SharedFunctionInfo* info = function->shared();
-  if (info->HasBuiltinFunctionId()) {
-    BuiltinFunctionId id = info->builtin_function_id();
-#define CALL_GENERATOR_CASE(name)                           \
-    if (id == k##name) {                                    \
-      return CallStubCompiler::Compile##name##Call(object,  \
-                                                  holder,   \
-                                                  cell,     \
-                                                  function, \
-                                                  fname);   \
+  if (function->shared()->HasBuiltinFunctionId()) {
+    BuiltinFunctionId id = function->shared()->builtin_function_id();
+#define CALL_GENERATOR_CASE(name)                               \
+    if (id == k##name) {                                        \
+      return CallStubCompiler::Compile##name##Call(object,      \
+                                                   holder,      \
+                                                   cell,        \
+                                                   function,    \
+                                                   fname);      \
     }
     CUSTOM_CALL_IC_GENERATORS(CALL_GENERATOR_CASE)
 #undef CALL_GENERATOR_CASE
@@ -1739,100 +1429,99 @@
 }
 
 
-MaybeObject* CallStubCompiler::GetCode(PropertyType type, String* name) {
+Handle<Code> CallStubCompiler::GetCode(PropertyType type, Handle<String> name) {
   int argc = arguments_.immediate();
   Code::Flags flags = Code::ComputeMonomorphicFlags(kind_,
                                                     type,
-                                                    extra_ic_state_,
+                                                    extra_state_,
                                                     cache_holder_,
                                                     argc);
   return GetCodeWithFlags(flags, name);
 }
 
 
-MaybeObject* CallStubCompiler::GetCode(JSFunction* function) {
-  String* function_name = NULL;
+Handle<Code> CallStubCompiler::GetCode(Handle<JSFunction> function) {
+  Handle<String> function_name;
   if (function->shared()->name()->IsString()) {
-    function_name = String::cast(function->shared()->name());
+    function_name = Handle<String>(String::cast(function->shared()->name()));
   }
   return GetCode(CONSTANT_FUNCTION, function_name);
 }
 
 
-MaybeObject* ConstructStubCompiler::GetCode() {
+Handle<Code> ConstructStubCompiler::GetCode() {
   Code::Flags flags = Code::ComputeFlags(Code::STUB);
-  Object* result;
-  { MaybeObject* maybe_result = GetCodeWithFlags(flags, "ConstructStub");
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
-  Code* code = Code::cast(result);
-  USE(code);
-  PROFILE(isolate(), CodeCreateEvent(Logger::STUB_TAG, code, "ConstructStub"));
-  GDBJIT(AddCode(GDBJITInterface::STUB, "ConstructStub", Code::cast(code)));
-  return result;
+  Handle<Code> code = GetCodeWithFlags(flags, "ConstructStub");
+  PROFILE(isolate(), CodeCreateEvent(Logger::STUB_TAG, *code, "ConstructStub"));
+  GDBJIT(AddCode(GDBJITInterface::STUB, "ConstructStub", *code));
+  return code;
 }
 
 
 CallOptimization::CallOptimization(LookupResult* lookup) {
-  if (!lookup->IsProperty() || !lookup->IsCacheable() ||
-      lookup->type() != CONSTANT_FUNCTION) {
-    Initialize(NULL);
-  } else {
+  if (lookup->IsFound() &&
+      lookup->IsCacheable() &&
+      lookup->type() == CONSTANT_FUNCTION) {
     // We only optimize constant function calls.
-    Initialize(lookup->GetConstantFunction());
+    Initialize(Handle<JSFunction>(lookup->GetConstantFunction()));
+  } else {
+    Initialize(Handle<JSFunction>::null());
   }
 }
 
-CallOptimization::CallOptimization(JSFunction* function) {
+CallOptimization::CallOptimization(Handle<JSFunction> function) {
   Initialize(function);
 }
 
 
-int CallOptimization::GetPrototypeDepthOfExpectedType(JSObject* object,
-                                                      JSObject* holder) const {
-  ASSERT(is_simple_api_call_);
-  if (expected_receiver_type_ == NULL) return 0;
+int CallOptimization::GetPrototypeDepthOfExpectedType(
+    Handle<JSObject> object,
+    Handle<JSObject> holder) const {
+  ASSERT(is_simple_api_call());
+  if (expected_receiver_type_.is_null()) return 0;
   int depth = 0;
-  while (object != holder) {
-    if (object->IsInstanceOf(expected_receiver_type_)) return depth;
-    object = JSObject::cast(object->GetPrototype());
+  while (!object.is_identical_to(holder)) {
+    if (object->IsInstanceOf(*expected_receiver_type_)) return depth;
+    object = Handle<JSObject>(JSObject::cast(object->GetPrototype()));
     ++depth;
   }
-  if (holder->IsInstanceOf(expected_receiver_type_)) return depth;
+  if (holder->IsInstanceOf(*expected_receiver_type_)) return depth;
   return kInvalidProtoDepth;
 }
 
 
-void CallOptimization::Initialize(JSFunction* function) {
-  constant_function_ = NULL;
+void CallOptimization::Initialize(Handle<JSFunction> function) {
+  constant_function_ = Handle<JSFunction>::null();
   is_simple_api_call_ = false;
-  expected_receiver_type_ = NULL;
-  api_call_info_ = NULL;
+  expected_receiver_type_ = Handle<FunctionTemplateInfo>::null();
+  api_call_info_ = Handle<CallHandlerInfo>::null();
 
-  if (function == NULL || !function->is_compiled()) return;
+  if (function.is_null() || !function->is_compiled()) return;
 
   constant_function_ = function;
   AnalyzePossibleApiFunction(function);
 }
 
 
-void CallOptimization::AnalyzePossibleApiFunction(JSFunction* function) {
-  SharedFunctionInfo* sfi = function->shared();
-  if (!sfi->IsApiFunction()) return;
-  FunctionTemplateInfo* info = sfi->get_api_func_data();
+void CallOptimization::AnalyzePossibleApiFunction(Handle<JSFunction> function) {
+  if (!function->shared()->IsApiFunction()) return;
+  Handle<FunctionTemplateInfo> info(function->shared()->get_api_func_data());
 
   // Require a C++ callback.
   if (info->call_code()->IsUndefined()) return;
-  api_call_info_ = CallHandlerInfo::cast(info->call_code());
+  api_call_info_ =
+      Handle<CallHandlerInfo>(CallHandlerInfo::cast(info->call_code()));
 
   // Accept signatures that either have no restrictions at all or
   // only have restrictions on the receiver.
   if (!info->signature()->IsUndefined()) {
-    SignatureInfo* signature = SignatureInfo::cast(info->signature());
+    Handle<SignatureInfo> signature =
+        Handle<SignatureInfo>(SignatureInfo::cast(info->signature()));
     if (!signature->args()->IsUndefined()) return;
     if (!signature->receiver()->IsUndefined()) {
       expected_receiver_type_ =
-          FunctionTemplateInfo::cast(signature->receiver());
+          Handle<FunctionTemplateInfo>(
+              FunctionTemplateInfo::cast(signature->receiver()));
     }
   }