Eliminate special keyed load string stub in favor of uniform handlers.

src/ic/ic.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/base/bits.h"
@@ skipping 494 matching lines @@
     default:
       UNREACHABLE();
   }
 }
 
 
 void KeyedLoadIC::Clear(Isolate* isolate, Address address, Code* target,
                         ConstantPoolArray* constant_pool) {
   if (IsCleared(target)) return;
 
-  // If the target is the string_stub, then don't clear it. It is the
-  // perfect stub if we continue to see strings. Holding this
-  // state is not preventing learning new information.
-  if (target != *isolate->builtins()->KeyedLoadIC_String()) {
-    // Make sure to also clear the map used in inline fast cases.  If we
-    // do not clear these maps, cached code can keep objects alive
-    // through the embedded maps.
-    SetTargetAtAddress(address, *pre_monomorphic_stub(isolate), constant_pool);
-  }
+  // Make sure to also clear the map used in inline fast cases.  If we
+  // do not clear these maps, cached code can keep objects alive
+  // through the embedded maps.
+  SetTargetAtAddress(address, *pre_monomorphic_stub(isolate), constant_pool);
 }
 
 
 void CallIC::Clear(Isolate* isolate, Address address, Code* target,
                    ConstantPoolArray* constant_pool) {
   // Currently, CallIC doesn't have state changes.
 }
 
 
 void LoadIC::Clear(Isolate* isolate, Address address, Code* target,
@@ skipping 586 matching lines @@
         key = Handle<Smi>(Smi::FromInt(int_value), isolate);
       }
     }
   } else if (key->IsUndefined()) {
     key = isolate->factory()->undefined_string();
   }
   return key;
 }
 
 
-Handle<Code> KeyedLoadIC::LoadElementStub(Handle<JSObject> receiver) {
+Handle<Code> KeyedLoadIC::LoadElementStub(Handle<HeapObject> receiver) {
   Handle<Map> receiver_map(receiver->map(), isolate());
   MapHandleList target_receiver_maps;
-  if (target().is_identical_to(string_stub())) {
-    target_receiver_maps.Add(isolate()->factory()->string_map());
-  } else {
-    TargetMaps(&target_receiver_maps);
-  }
+  TargetMaps(&target_receiver_maps);
+
   if (target_receiver_maps.length() == 0) {
     return PropertyICCompiler::ComputeKeyedLoadMonomorphic(receiver_map);
   }
 
   // The first time a receiver is seen that is a transitioned version of the
   // previous monomorphic receiver type, assume the new ElementsKind is the
   // monomorphic type. This benefits global arrays that only transition
   // once, and all call sites accessing them are faster if they remain
   // monomorphic. If this optimistic assumption is not true, the IC will
   // miss again and it will become polymorphic and support both the
   // untransitioned and transitioned maps.
-  if (state() == MONOMORPHIC && IsMoreGeneralElementsKindTransition(
-                                    target_receiver_maps.at(0)->elements_kind(),
-                                    receiver->GetElementsKind())) {
+  if (state() == MONOMORPHIC && !receiver->IsString() &&
+      IsMoreGeneralElementsKindTransition(
+          target_receiver_maps.at(0)->elements_kind(),
+          Handle<JSObject>::cast(receiver)->GetElementsKind())) {
     return PropertyICCompiler::ComputeKeyedLoadMonomorphic(receiver_map);
   }
 
   DCHECK(state() != GENERIC);
 
   // Determine the list of receiver maps that this call site has seen,
   // adding the map that was just encountered.
   if (!AddOneReceiverMapIfMissing(&target_receiver_maps, receiver_map)) {
     // If the miss wasn't due to an unseen map, a polymorphic stub
     // won't help, use the generic stub.
@@ skipping 27 matching lines @@
 
   // Check for non-string values that can be converted into an
   // internalized string directly or is representable as a smi.
   key = TryConvertKey(key, isolate());
 
   if (key->IsInternalizedString() || key->IsSymbol()) {
     ASSIGN_RETURN_ON_EXCEPTION(isolate(), load_handle,
                                LoadIC::Load(object, Handle<Name>::cast(key)),
                                Object);
   } else if (FLAG_use_ic && !object->IsAccessCheckNeeded()) {
-    if (object->IsString() && key->IsNumber()) {
-      if (state() == UNINITIALIZED) stub = string_stub();
-    } else if (object->IsJSObject()) {
-      Handle<JSObject> receiver = Handle<JSObject>::cast(object);
-      if (!Object::ToSmi(isolate(), key).is_null()) {
+    if (object->IsJSObject() || (object->IsString() && key->IsNumber())) {
+      Handle<HeapObject> receiver = Handle<HeapObject>::cast(object);
+      if (object->IsString() || !Object::ToSmi(isolate(), key).is_null()) {
         stub = LoadElementStub(receiver);
       }
     }
   }
 
   if (!is_target_set()) {
     Code* generic = *generic_stub();
     if (*stub == generic) {
       TRACE_GENERIC_IC(isolate(), "KeyedLoadIC", "set generic");
     }
@@ skipping 1448 matching lines @@
 static const Address IC_utilities[] = {
 #define ADDR(name) FUNCTION_ADDR(name),
     IC_UTIL_LIST(ADDR) NULL
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) { return IC_utilities[id]; }
 }
 }  // namespace v8::internal