ic.cc

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// 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:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
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//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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#include "v8.h"

#include "accessors.h"
#include "api.h"
#include "arguments.h"
#include "codegen.h"
#include "execution.h"
#include "ic-inl.h"
#include "runtime.h"
#include "stub-cache.h"

namespace v8 {
namespace internal {

#ifdef DEBUG
char IC::TransitionMarkFromState(IC::State state) {
  switch (state) {
    case UNINITIALIZED: return '0';
    case PREMONOMORPHIC: return 'P';
    case MONOMORPHIC: return '1';
    case MONOMORPHIC_PROTOTYPE_FAILURE: return '^';
    case MEGAMORPHIC: return IsGeneric() ? 'G' : 'N';

    // We never see the debugger states here, because the state is
    // computed from the original code - not the patched code. Let
    // these cases fall through to the unreachable code below.
    case DEBUG_BREAK: break;
    case DEBUG_PREPARE_STEP_IN: break;
  }
  UNREACHABLE();
  return 0;
}

void IC::TraceIC(const char* type,
                 Handle<Object> name,
                 State old_state,
                 Code* new_target) {
  if (FLAG_trace_ic) {
    State new_state = StateFrom(new_target,
                                HEAP->undefined_value(),
                                HEAP->undefined_value());
    PrintF("[%s in ", type);
    StackFrameIterator it;
    while (it.frame()->fp() != this->fp()) it.Advance();
    StackFrame* raw_frame = it.frame();
    if (raw_frame->is_internal()) {
      Isolate* isolate = new_target->GetIsolate();
      Code* apply_builtin = isolate->builtins()->builtin(
          Builtins::kFunctionApply);
      if (raw_frame->unchecked_code() == apply_builtin) {
        PrintF("apply from ");
        it.Advance();
        raw_frame = it.frame();
      }
    }
    JavaScriptFrame::PrintTop(stdout, false, true);
    bool new_can_grow =
        Code::GetKeyedAccessGrowMode(new_target->extra_ic_state()) ==
        ALLOW_JSARRAY_GROWTH;
    PrintF(" (%c->%c%s)",
           TransitionMarkFromState(old_state),
           TransitionMarkFromState(new_state),
           new_can_grow ? ".GROW" : "");
    name->Print();
    PrintF("]\n");
  }
}

#define TRACE_GENERIC_IC(type, reason)                          \
  do {                                                          \
    if (FLAG_trace_ic) {                                        \
      PrintF("[%s patching generic stub in ", type);            \
      JavaScriptFrame::PrintTop(stdout, false, true);           \
      PrintF(" (%s)]\n", reason);                               \
    }                                                           \
  } while (false)

#else
#define TRACE_GENERIC_IC(type, reason)
#endif  // DEBUG

#define TRACE_IC(type, name, old_state, new_target)             \
  ASSERT((TraceIC(type, name, old_state, new_target), true))

IC::IC(FrameDepth depth, Isolate* isolate) : isolate_(isolate) {
  ASSERT(isolate == Isolate::Current());
  // To improve the performance of the (much used) IC code, we unfold
  // a few levels of the stack frame iteration code. This yields a
  // ~35% speedup when running DeltaBlue with the '--nouse-ic' flag.
  const Address entry =
      Isolate::c_entry_fp(isolate->thread_local_top());
  Address* pc_address =
      reinterpret_cast<Address*>(entry + ExitFrameConstants::kCallerPCOffset);
  Address fp = Memory::Address_at(entry + ExitFrameConstants::kCallerFPOffset);
  // If there's another JavaScript frame on the stack, we need to look
  // one frame further down the stack to find the frame pointer and
  // the return address stack slot.
  if (depth == EXTRA_CALL_FRAME) {
    const int kCallerPCOffset = StandardFrameConstants::kCallerPCOffset;
    pc_address = reinterpret_cast<Address*>(fp + kCallerPCOffset);
    fp = Memory::Address_at(fp + StandardFrameConstants::kCallerFPOffset);
  }
#ifdef DEBUG
  StackFrameIterator it;
  for (int i = 0; i < depth + 1; i++) it.Advance();
  StackFrame* frame = it.frame();
  ASSERT(fp == frame->fp() && pc_address == frame->pc_address());
#endif
  fp_ = fp;
  pc_address_ = pc_address;
}


#ifdef ENABLE_DEBUGGER_SUPPORT
Address IC::OriginalCodeAddress() const {
  HandleScope scope;
  // Compute the JavaScript frame for the frame pointer of this IC
  // structure. We need this to be able to find the function
  // corresponding to the frame.
  StackFrameIterator it;
  while (it.frame()->fp() != this->fp()) it.Advance();
  JavaScriptFrame* frame = JavaScriptFrame::cast(it.frame());
  // Find the function on the stack and both the active code for the
  // function and the original code.
  JSFunction* function = JSFunction::cast(frame->function());
  Handle<SharedFunctionInfo> shared(function->shared());
  Code* code = shared->code();
  ASSERT(Debug::HasDebugInfo(shared));
  Code* original_code = Debug::GetDebugInfo(shared)->original_code();
  ASSERT(original_code->IsCode());
  // Get the address of the call site in the active code. This is the
  // place where the call to DebugBreakXXX is and where the IC
  // normally would be.
  Address addr = pc() - Assembler::kCallTargetAddressOffset;
  // Return the address in the original code. This is the place where
  // the call which has been overwritten by the DebugBreakXXX resides
  // and the place where the inline cache system should look.
  intptr_t delta =
      original_code->instruction_start() - code->instruction_start();
  return addr + delta;
}
#endif


static bool HasNormalObjectsInPrototypeChain(Isolate* isolate,
                                             LookupResult* lookup,
                                             Object* receiver) {
  Object* end = lookup->IsProperty()
      ? lookup->holder() : Object::cast(isolate->heap()->null_value());
  for (Object* current = receiver;
       current != end;
       current = current->GetPrototype()) {
    if (current->IsJSObject() &&
        !JSObject::cast(current)->HasFastProperties() &&
        !current->IsJSGlobalProxy() &&
        !current->IsJSGlobalObject()) {
      return true;
    }
  }

  return false;
}


static bool TryRemoveInvalidPrototypeDependentStub(Code* target,
                                                   Object* receiver,
                                                   Object* name) {
  InlineCacheHolderFlag cache_holder =
      Code::ExtractCacheHolderFromFlags(target->flags());

  if (cache_holder == OWN_MAP && !receiver->IsJSObject()) {
    // The stub was generated for JSObject but called for non-JSObject.
    // IC::GetCodeCacheHolder is not applicable.
    return false;
  } else if (cache_holder == PROTOTYPE_MAP &&
             receiver->GetPrototype()->IsNull()) {
    // IC::GetCodeCacheHolder is not applicable.
    return false;
  }
  Map* map = IC::GetCodeCacheHolder(receiver, cache_holder)->map();

  // Decide whether the inline cache failed because of changes to the
  // receiver itself or changes to one of its prototypes.
  //
  // If there are changes to the receiver itself, the map of the
  // receiver will have changed and the current target will not be in
  // the receiver map's code cache.  Therefore, if the current target
  // is in the receiver map's code cache, the inline cache failed due
  // to prototype check failure.
  int index = map->IndexInCodeCache(name, target);
  if (index >= 0) {
    map->RemoveFromCodeCache(String::cast(name), target, index);
    return true;
  }

  return false;
}


IC::State IC::StateFrom(Code* target, Object* receiver, Object* name) {
  IC::State state = target->ic_state();

  if (state != MONOMORPHIC || !name->IsString()) return state;
  if (receiver->IsUndefined() || receiver->IsNull()) return state;

  // For keyed load/store/call, the most likely cause of cache failure is
  // that the key has changed.  We do not distinguish between
  // prototype and non-prototype failures for keyed access.
  Code::Kind kind = target->kind();
  if (kind == Code::KEYED_LOAD_IC ||
      kind == Code::KEYED_STORE_IC ||
      kind == Code::KEYED_CALL_IC) {
    return MONOMORPHIC;
  }

  // Remove the target from the code cache if it became invalid
  // because of changes in the prototype chain to avoid hitting it
  // again.
  // Call stubs handle this later to allow extra IC state
  // transitions.
  if (kind != Code::CALL_IC &&
      TryRemoveInvalidPrototypeDependentStub(target, receiver, name)) {
    return MONOMORPHIC_PROTOTYPE_FAILURE;
  }

  // The builtins object is special.  It only changes when JavaScript
  // builtins are loaded lazily.  It is important to keep inline
  // caches for the builtins object monomorphic.  Therefore, if we get
  // an inline cache miss for the builtins object after lazily loading
  // JavaScript builtins, we return uninitialized as the state to
  // force the inline cache back to monomorphic state.
  if (receiver->IsJSBuiltinsObject()) {
    return UNINITIALIZED;
  }

  return MONOMORPHIC;
}


RelocInfo::Mode IC::ComputeMode() {
  Address addr = address();
  Code* code = Code::cast(isolate()->heap()->FindCodeObject(addr));
  for (RelocIterator it(code, RelocInfo::kCodeTargetMask);
       !it.done(); it.next()) {
    RelocInfo* info = it.rinfo();
    if (info->pc() == addr) return info->rmode();
  }
  UNREACHABLE();
  return RelocInfo::NONE;
}


Failure* IC::TypeError(const char* type,
                       Handle<Object> object,
                       Handle<Object> key) {
  HandleScope scope(isolate());
  Handle<Object> args[2] = { key, object };
  Handle<Object> error = isolate()->factory()->NewTypeError(
      type, HandleVector(args, 2));
  return isolate()->Throw(*error);
}


Failure* IC::ReferenceError(const char* type, Handle<String> name) {
  HandleScope scope(isolate());
  Handle<Object> error = isolate()->factory()->NewReferenceError(
      type, HandleVector(&name, 1));
  return isolate()->Throw(*error);
}


static int ComputeTypeInfoCountDelta(IC::State old_state, IC::State new_state) {
  bool was_uninitialized =
      old_state == UNINITIALIZED || old_state == PREMONOMORPHIC;
  bool is_uninitialized =
      new_state == UNINITIALIZED || new_state == PREMONOMORPHIC;
  return (was_uninitialized && !is_uninitialized) ?  1 :
         (!was_uninitialized && is_uninitialized) ? -1 : 0;
}


void IC::PostPatching(Address address, Code* target, Code* old_target) {
  if (FLAG_type_info_threshold == 0 && !FLAG_watch_ic_patching) {
    return;
  }
  Code* host = target->GetHeap()->isolate()->
      inner_pointer_to_code_cache()->GetCacheEntry(address)->code;
  if (host->kind() != Code::FUNCTION) return;

  if (FLAG_type_info_threshold > 0 &&
      old_target->is_inline_cache_stub() &&
      target->is_inline_cache_stub()) {
    int delta = ComputeTypeInfoCountDelta(old_target->ic_state(),
                                          target->ic_state());
    // Not all Code objects have TypeFeedbackInfo.
    if (delta != 0 && host->type_feedback_info()->IsTypeFeedbackInfo()) {
      TypeFeedbackInfo* info =
          TypeFeedbackInfo::cast(host->type_feedback_info());
      info->set_ic_with_type_info_count(
          info->ic_with_type_info_count() + delta);
    }
  }
  if (FLAG_watch_ic_patching) {
    host->set_profiler_ticks(0);
    Isolate::Current()->runtime_profiler()->NotifyICChanged();
  }
  // TODO(2029): When an optimized function is patched, it would
  // be nice to propagate the corresponding type information to its
  // unoptimized version for the benefit of later inlining.
}


void IC::Clear(Address address) {
  Code* target = GetTargetAtAddress(address);

  // Don't clear debug break inline cache as it will remove the break point.
  if (target->ic_state() == DEBUG_BREAK) return;

  switch (target->kind()) {
    case Code::LOAD_IC: return LoadIC::Clear(address, target);
    case Code::KEYED_LOAD_IC:
      return KeyedLoadIC::Clear(address, target);
    case Code::STORE_IC: return StoreIC::Clear(address, target);
    case Code::KEYED_STORE_IC:
      return KeyedStoreIC::Clear(address, target);
    case Code::CALL_IC: return CallIC::Clear(address, target);
    case Code::KEYED_CALL_IC:  return KeyedCallIC::Clear(address, target);
    case Code::COMPARE_IC: return CompareIC::Clear(address, target);
    case Code::UNARY_OP_IC:
    case Code::BINARY_OP_IC:
    case Code::TO_BOOLEAN_IC:
      // Clearing these is tricky and does not
      // make any performance difference.
      return;
    default: UNREACHABLE();
  }
}


void CallICBase::Clear(Address address, Code* target) {
  if (target->ic_state() == UNINITIALIZED) return;
  bool contextual = CallICBase::Contextual::decode(target->extra_ic_state());
  Code* code =
      Isolate::Current()->stub_cache()->FindCallInitialize(
          target->arguments_count(),
          contextual ? RelocInfo::CODE_TARGET_CONTEXT : RelocInfo::CODE_TARGET,
          target->kind());
  SetTargetAtAddress(address, code);
}


void KeyedLoadIC::Clear(Address address, Code* target) {
  if (target->ic_state() == UNINITIALIZED) return;
  // 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, initialize_stub());
}


void LoadIC::Clear(Address address, Code* target) {
  if (target->ic_state() == UNINITIALIZED) return;
  SetTargetAtAddress(address, initialize_stub());
}


void StoreIC::Clear(Address address, Code* target) {
  if (target->ic_state() == UNINITIALIZED) return;
  SetTargetAtAddress(address,
      (Code::GetStrictMode(target->extra_ic_state()) == kStrictMode)
        ? initialize_stub_strict()
        : initialize_stub());
}


void KeyedStoreIC::Clear(Address address, Code* target) {
  if (target->ic_state() == UNINITIALIZED) return;
  SetTargetAtAddress(address,
      (Code::GetStrictMode(target->extra_ic_state()) == kStrictMode)
        ? initialize_stub_strict()
        : initialize_stub());
}


void CompareIC::Clear(Address address, Code* target) {
  // Only clear ICCompareStubs, we currently cannot clear generic CompareStubs.
  if (target->major_key() != CodeStub::CompareIC) return;
  // Only clear CompareICs that can retain objects.
  if (target->compare_state() != KNOWN_OBJECTS) return;
  Token::Value op = CompareIC::ComputeOperation(target);
  SetTargetAtAddress(address, GetRawUninitialized(op));
  PatchInlinedSmiCode(address, DISABLE_INLINED_SMI_CHECK);
}


static bool HasInterceptorGetter(JSObject* object) {
  return !object->GetNamedInterceptor()->getter()->IsUndefined();
}


static void LookupForRead(Handle<Object> object,
                          Handle<String> name,
                          LookupResult* lookup) {
  // Skip all the objects with named interceptors, but
  // without actual getter.
  while (true) {
    object->Lookup(*name, lookup);
    // Besides normal conditions (property not found or it's not
    // an interceptor), bail out if lookup is not cacheable: we won't
    // be able to IC it anyway and regular lookup should work fine.
    if (!lookup->IsFound()
        || (lookup->type() != INTERCEPTOR)
        || !lookup->IsCacheable()) {
      return;
    }

    Handle<JSObject> holder(lookup->holder());
    if (HasInterceptorGetter(*holder)) {
      return;
    }

    holder->LocalLookupRealNamedProperty(*name, lookup);
    if (lookup->IsProperty()) {
      ASSERT(lookup->type() != INTERCEPTOR);
      return;
    }

    Handle<Object> proto(holder->GetPrototype());
    if (proto->IsNull()) {
      lookup->NotFound();
      return;
    }

    object = proto;
  }
}


Handle<Object> CallICBase::TryCallAsFunction(Handle<Object> object) {
  Handle<Object> delegate = Execution::GetFunctionDelegate(object);

  if (delegate->IsJSFunction() && !object->IsJSFunctionProxy()) {
    // Patch the receiver and use the delegate as the function to
    // invoke. This is used for invoking objects as if they were functions.
    const int argc = target()->arguments_count();
    StackFrameLocator locator;
    JavaScriptFrame* frame = locator.FindJavaScriptFrame(0);
    int index = frame->ComputeExpressionsCount() - (argc + 1);
    frame->SetExpression(index, *object);
  }

  return delegate;
}


void CallICBase::ReceiverToObjectIfRequired(Handle<Object> callee,
                                            Handle<Object> object) {
  while (callee->IsJSFunctionProxy()) {
    callee = Handle<Object>(JSFunctionProxy::cast(*callee)->call_trap());
  }

  if (callee->IsJSFunction()) {
    Handle<JSFunction> function = Handle<JSFunction>::cast(callee);
    if (!function->shared()->is_classic_mode() || function->IsBuiltin()) {
      // Do not wrap receiver for strict mode functions or for builtins.
      return;
    }
  }

  // And only wrap string, number or boolean.
  if (object->IsString() || object->IsNumber() || object->IsBoolean()) {
    // Change the receiver to the result of calling ToObject on it.
    const int argc = this->target()->arguments_count();
    StackFrameLocator locator;
    JavaScriptFrame* frame = locator.FindJavaScriptFrame(0);
    int index = frame->ComputeExpressionsCount() - (argc + 1);
    frame->SetExpression(index, *isolate()->factory()->ToObject(object));
  }
}


MaybeObject* CallICBase::LoadFunction(State state,
                                      Code::ExtraICState extra_ic_state,
                                      Handle<Object> object,
                                      Handle<String> name) {
  // If the object is undefined or null it's illegal to try to get any
  // of its properties; throw a TypeError in that case.
  if (object->IsUndefined() || object->IsNull()) {
    return TypeError("non_object_property_call", object, name);
  }

  // Check if the name is trivially convertible to an index and get
  // the element if so.
  uint32_t index;
  if (name->AsArrayIndex(&index)) {
    Handle<Object> result = Object::GetElement(object, index);
    RETURN_IF_EMPTY_HANDLE(isolate(), result);
    if (result->IsJSFunction()) return *result;

    // Try to find a suitable function delegate for the object at hand.
    result = TryCallAsFunction(result);
    if (result->IsJSFunction()) return *result;

    // Otherwise, it will fail in the lookup step.
  }

  // Lookup the property in the object.
  LookupResult lookup(isolate());
  LookupForRead(object, name, &lookup);

  if (!lookup.IsProperty()) {
    // If the object does not have the requested property, check which
    // exception we need to throw.
    return IsContextual(object)
        ? ReferenceError("not_defined", name)
        : TypeError("undefined_method", object, name);
  }

  // Lookup is valid: Update inline cache and stub cache.
  if (FLAG_use_ic) {
    UpdateCaches(&lookup, state, extra_ic_state, object, name);
  }

  // Get the property.
  PropertyAttributes attr;
  Handle<Object> result =
      Object::GetProperty(object, object, &lookup, name, &attr);
  RETURN_IF_EMPTY_HANDLE(isolate(), result);

  if (lookup.type() == INTERCEPTOR && attr == ABSENT) {
    // If the object does not have the requested property, check which
    // exception we need to throw.
    return IsContextual(object)
        ? ReferenceError("not_defined", name)
        : TypeError("undefined_method", object, name);
  }

  ASSERT(!result->IsTheHole());

  // Make receiver an object if the callee requires it. Strict mode or builtin
  // functions do not wrap the receiver, non-strict functions and objects
  // called as functions do.
  ReceiverToObjectIfRequired(result, object);

  if (result->IsJSFunction()) {
    Handle<JSFunction> function = Handle<JSFunction>::cast(result);
#ifdef ENABLE_DEBUGGER_SUPPORT
    // Handle stepping into a function if step into is active.
    Debug* debug = isolate()->debug();
    if (debug->StepInActive()) {
      // Protect the result in a handle as the debugger can allocate and might
      // cause GC.
      debug->HandleStepIn(function, object, fp(), false);
    }
#endif
    return *function;
  }

  // Try to find a suitable function delegate for the object at hand.
  result = TryCallAsFunction(result);
  if (result->IsJSFunction()) return *result;

  return TypeError("property_not_function", object, name);
}


bool CallICBase::TryUpdateExtraICState(LookupResult* lookup,
                                       Handle<Object> object,
                                       Code::ExtraICState* extra_ic_state) {
  ASSERT(kind_ == Code::CALL_IC);
  if (lookup->type() != CONSTANT_FUNCTION) return false;
  JSFunction* function = lookup->GetConstantFunction();
  if (!function->shared()->HasBuiltinFunctionId()) return false;

  // Fetch the arguments passed to the called function.
  const int argc = target()->arguments_count();
  Address entry = isolate()->c_entry_fp(isolate()->thread_local_top());
  Address fp = Memory::Address_at(entry + ExitFrameConstants::kCallerFPOffset);
  Arguments args(argc + 1,
                 &Memory::Object_at(fp +
                                    StandardFrameConstants::kCallerSPOffset +
                                    argc * kPointerSize));
  switch (function->shared()->builtin_function_id()) {
    case kStringCharCodeAt:
    case kStringCharAt:
      if (object->IsString()) {
        String* string = String::cast(*object);
        // Check there's the right string value or wrapper in the receiver slot.
        ASSERT(string == args[0] || string == JSValue::cast(args[0])->value());
        // If we're in the default (fastest) state and the index is
        // out of bounds, update the state to record this fact.
        if (StringStubState::decode(*extra_ic_state) == DEFAULT_STRING_STUB &&
            argc >= 1 && args[1]->IsNumber()) {
          double index = DoubleToInteger(args.number_at(1));
          if (index < 0 || index >= string->length()) {
            *extra_ic_state =
                StringStubState::update(*extra_ic_state,
                                        STRING_INDEX_OUT_OF_BOUNDS);
            return true;
          }
        }
      }
      break;
    default:
      return false;
  }
  return false;
}


Handle<Code> CallICBase::ComputeMonomorphicStub(LookupResult* lookup,
                                                State state,
                                                Code::ExtraICState extra_state,
                                                Handle<Object> object,
                                                Handle<String> name) {
  int argc = target()->arguments_count();
  Handle<JSObject> holder(lookup->holder());
  switch (lookup->type()) {
    case FIELD: {
      int index = lookup->GetFieldIndex();
      return isolate()->stub_cache()->ComputeCallField(
          argc, kind_, extra_state, name, object, holder, index);
    }
    case CONSTANT_FUNCTION: {
      // Get the constant function and compute the code stub for this
      // call; used for rewriting to monomorphic state and making sure
      // that the code stub is in the stub cache.
      Handle<JSFunction> function(lookup->GetConstantFunction());
      return isolate()->stub_cache()->ComputeCallConstant(
          argc, kind_, extra_state, name, object, holder, function);
    }
    case NORMAL: {
      // If we return a null handle, the IC will not be patched.
      if (!object->IsJSObject()) return Handle<Code>::null();
      Handle<JSObject> receiver = Handle<JSObject>::cast(object);

      if (holder->IsGlobalObject()) {
        Handle<GlobalObject> global = Handle<GlobalObject>::cast(holder);
        Handle<JSGlobalPropertyCell> cell(global->GetPropertyCell(lookup));
        if (!cell->value()->IsJSFunction()) return Handle<Code>::null();
        Handle<JSFunction> function(JSFunction::cast(cell->value()));
        return isolate()->stub_cache()->ComputeCallGlobal(
            argc, kind_, extra_state, name, receiver, global, cell, function);
      } else {
        // There is only one shared stub for calling normalized
        // properties. It does not traverse the prototype chain, so the
        // property must be found in the receiver for the stub to be
        // applicable.
        if (!holder.is_identical_to(receiver)) return Handle<Code>::null();
        return isolate()->stub_cache()->ComputeCallNormal(
            argc, kind_, extra_state);
      }
      break;
    }
    case INTERCEPTOR:
      ASSERT(HasInterceptorGetter(*holder));
      return isolate()->stub_cache()->ComputeCallInterceptor(
          argc, kind_, extra_state, name, object, holder);
    default:
      return Handle<Code>::null();
  }
}


void CallICBase::UpdateCaches(LookupResult* lookup,
                              State state,
                              Code::ExtraICState extra_ic_state,
                              Handle<Object> object,
                              Handle<String> name) {
  // Bail out if we didn't find a result.
  if (!lookup->IsProperty() || !lookup->IsCacheable()) return;

  if (lookup->holder() != *object &&
      HasNormalObjectsInPrototypeChain(
          isolate(), lookup, object->GetPrototype())) {
    // Suppress optimization for prototype chains with slow properties objects
    // in the middle.
    return;
  }

  // Compute the number of arguments.
  int argc = target()->arguments_count();
  bool had_proto_failure = false;
  Handle<Code> code;
  if (state == UNINITIALIZED) {
    // This is the first time we execute this inline cache.
    // Set the target to the pre monomorphic stub to delay
    // setting the monomorphic state.
    code = isolate()->stub_cache()->ComputeCallPreMonomorphic(
        argc, kind_, extra_ic_state);
  } else if (state == MONOMORPHIC) {
    if (kind_ == Code::CALL_IC &&
        TryUpdateExtraICState(lookup, object, &extra_ic_state)) {
      code = ComputeMonomorphicStub(lookup, state, extra_ic_state,
                                    object, name);
    } else if (kind_ == Code::CALL_IC &&
               TryRemoveInvalidPrototypeDependentStub(target(),
                                                      *object,
                                                      *name)) {
      had_proto_failure = true;
      code = ComputeMonomorphicStub(lookup, state, extra_ic_state,
                                    object, name);
    } else {
      code = isolate()->stub_cache()->ComputeCallMegamorphic(
          argc, kind_, extra_ic_state);
    }
  } else {
    code = ComputeMonomorphicStub(lookup, state, extra_ic_state,
                                  object, name);
  }

  // If there's no appropriate stub we simply avoid updating the caches.
  if (code.is_null()) return;

  // Patch the call site depending on the state of the cache.
  if (state == UNINITIALIZED ||
      state == PREMONOMORPHIC ||
      state == MONOMORPHIC ||
      state == MONOMORPHIC_PROTOTYPE_FAILURE) {
    set_target(*code);
  } else if (state == MEGAMORPHIC) {
    // Cache code holding map should be consistent with
    // GenerateMonomorphicCacheProbe. It is not the map which holds the stub.
    Handle<JSObject> cache_object = object->IsJSObject()
        ? Handle<JSObject>::cast(object)
        : Handle<JSObject>(JSObject::cast(object->GetPrototype()));
    // Update the stub cache.
    isolate()->stub_cache()->Set(*name, cache_object->map(), *code);
  }

  if (had_proto_failure) state = MONOMORPHIC_PROTOTYPE_FAILURE;
  TRACE_IC(kind_ == Code::CALL_IC ? "CallIC" : "KeyedCallIC",
           name, state, target());
}


MaybeObject* KeyedCallIC::LoadFunction(State state,
                                       Handle<Object> object,
                                       Handle<Object> key) {
  if (key->IsSymbol()) {
    return CallICBase::LoadFunction(state,
                                    Code::kNoExtraICState,
                                    object,
                                    Handle<String>::cast(key));
  }

  if (object->IsUndefined() || object->IsNull()) {
    return TypeError("non_object_property_call", object, key);
  }

  if (FLAG_use_ic && state != MEGAMORPHIC && object->IsHeapObject()) {
    int argc = target()->arguments_count();
    Handle<Map> map =
        isolate()->factory()->non_strict_arguments_elements_map();
    if (object->IsJSObject() &&
        Handle<JSObject>::cast(object)->elements()->map() == *map) {
      Handle<Code> code = isolate()->stub_cache()->ComputeCallArguments(
          argc, Code::KEYED_CALL_IC);
      set_target(*code);
      TRACE_IC("KeyedCallIC", key, state, target());
    } else if (!object->IsAccessCheckNeeded()) {
      Handle<Code> code = isolate()->stub_cache()->ComputeCallMegamorphic(
          argc, Code::KEYED_CALL_IC, Code::kNoExtraICState);
      set_target(*code);
      TRACE_IC("KeyedCallIC", key, state, target());
    }
  }

  Handle<Object> result = GetProperty(object, key);
  RETURN_IF_EMPTY_HANDLE(isolate(), result);

  // Make receiver an object if the callee requires it. Strict mode or builtin
  // functions do not wrap the receiver, non-strict functions and objects
  // called as functions do.
  ReceiverToObjectIfRequired(result, object);
  if (result->IsJSFunction()) return *result;

  result = TryCallAsFunction(result);
  if (result->IsJSFunction()) return *result;

  return TypeError("property_not_function", object, key);
}


MaybeObject* LoadIC::Load(State state,
                          Handle<Object> object,
                          Handle<String> name) {
  // If the object is undefined or null it's illegal to try to get any
  // of its properties; throw a TypeError in that case.
  if (object->IsUndefined() || object->IsNull()) {
    return TypeError("non_object_property_load", object, name);
  }

  if (FLAG_use_ic) {
    // Use specialized code for getting the length of strings and
    // string wrapper objects.  The length property of string wrapper
    // objects is read-only and therefore always returns the length of
    // the underlying string value.  See ECMA-262 15.5.5.1.
    if ((object->IsString() || object->IsStringWrapper()) &&
        name->Equals(isolate()->heap()->length_symbol())) {
      Handle<Code> stub;
      if (state == UNINITIALIZED) {
        stub = pre_monomorphic_stub();
      } else if (state == PREMONOMORPHIC) {
        stub = object->IsString()
            ? isolate()->builtins()->LoadIC_StringLength()
            : isolate()->builtins()->LoadIC_StringWrapperLength();
      } else if (state == MONOMORPHIC && object->IsStringWrapper()) {
        stub = isolate()->builtins()->LoadIC_StringWrapperLength();
      } else if (state != MEGAMORPHIC) {
        stub = megamorphic_stub();
      }
      if (!stub.is_null()) {
        set_target(*stub);
#ifdef DEBUG
        if (FLAG_trace_ic) PrintF("[LoadIC : +#length /string]\n");
#endif
      }
      // Get the string if we have a string wrapper object.
      Handle<Object> string = object->IsJSValue()
          ? Handle<Object>(Handle<JSValue>::cast(object)->value())
          : object;
      return Smi::FromInt(String::cast(*string)->length());
    }

    // Use specialized code for getting the length of arrays.
    if (object->IsJSArray() &&
        name->Equals(isolate()->heap()->length_symbol())) {
      Handle<Code> stub;
      if (state == UNINITIALIZED) {
        stub = pre_monomorphic_stub();
      } else if (state == PREMONOMORPHIC) {
        stub = isolate()->builtins()->LoadIC_ArrayLength();
      } else if (state != MEGAMORPHIC) {
        stub = megamorphic_stub();
      }
      if (!stub.is_null()) {
        set_target(*stub);
#ifdef DEBUG
        if (FLAG_trace_ic) PrintF("[LoadIC : +#length /array]\n");
#endif
      }
      return JSArray::cast(*object)->length();
    }

    // Use specialized code for getting prototype of functions.
    if (object->IsJSFunction() &&
        name->Equals(isolate()->heap()->prototype_symbol()) &&
        Handle<JSFunction>::cast(object)->should_have_prototype()) {
      Handle<Code> stub;
      if (state == UNINITIALIZED) {
        stub = pre_monomorphic_stub();
      } else if (state == PREMONOMORPHIC) {
        stub = isolate()->builtins()->LoadIC_FunctionPrototype();
      } else if (state != MEGAMORPHIC) {
        stub = megamorphic_stub();
      }
      if (!stub.is_null()) {
        set_target(*stub);
#ifdef DEBUG
        if (FLAG_trace_ic) PrintF("[LoadIC : +#prototype /function]\n");
#endif
      }
      return Accessors::FunctionGetPrototype(*object, 0);
    }
  }

  // Check if the name is trivially convertible to an index and get
  // the element if so.
  uint32_t index;
  if (name->AsArrayIndex(&index)) return object->GetElement(index);

  // Named lookup in the object.
  LookupResult lookup(isolate());
  LookupForRead(object, name, &lookup);

  // If we did not find a property, check if we need to throw an exception.
  if (!lookup.IsProperty()) {
    if (IsContextual(object)) {
      return ReferenceError("not_defined", name);
    }
    LOG(isolate(), SuspectReadEvent(*name, *object));
  }

  // Update inline cache and stub cache.
  if (FLAG_use_ic) {
    UpdateCaches(&lookup, state, object, name);
  }

  PropertyAttributes attr;
  if (lookup.IsFound() &&
      (lookup.type() == INTERCEPTOR || lookup.type() == HANDLER)) {
    // Get the property.
    Handle<Object> result =
        Object::GetProperty(object, object, &lookup, name, &attr);
    RETURN_IF_EMPTY_HANDLE(isolate(), result);
    // If the property is not present, check if we need to throw an
    // exception.
    if (attr == ABSENT && IsContextual(object)) {
      return ReferenceError("not_defined", name);
    }
    return *result;
  }

  // Get the property.
  return object->GetProperty(*object, &lookup, *name, &attr);
}


void LoadIC::UpdateCaches(LookupResult* lookup,
                          State state,
                          Handle<Object> object,
                          Handle<String> name) {
  // Bail out if the result is not cacheable.
  if (!lookup->IsCacheable()) return;

  // Loading properties from values is not common, so don't try to
  // deal with non-JS objects here.
  if (!object->IsJSObject()) return;
  Handle<JSObject> receiver = Handle<JSObject>::cast(object);

  if (HasNormalObjectsInPrototypeChain(isolate(), lookup, *object)) return;

  // Compute the code stub for this load.
  Handle<Code> code;
  if (state == UNINITIALIZED) {
    // This is the first time we execute this inline cache.
    // Set the target to the pre monomorphic stub to delay
    // setting the monomorphic state.
    code = pre_monomorphic_stub();
  } else if (!lookup->IsProperty()) {
    // Nonexistent property. The result is undefined.
    code = isolate()->stub_cache()->ComputeLoadNonexistent(name, receiver);
  } else {
    // Compute monomorphic stub.
    Handle<JSObject> holder(lookup->holder());
    switch (lookup->type()) {
      case FIELD:
        code = isolate()->stub_cache()->ComputeLoadField(
            name, receiver, holder, lookup->GetFieldIndex());
        break;
      case CONSTANT_FUNCTION: {
        Handle<JSFunction> constant(lookup->GetConstantFunction());
        code = isolate()->stub_cache()->ComputeLoadConstant(
            name, receiver, holder, constant);
        break;
      }
      case NORMAL:
        if (holder->IsGlobalObject()) {
          Handle<GlobalObject> global = Handle<GlobalObject>::cast(holder);
          Handle<JSGlobalPropertyCell> cell(global->GetPropertyCell(lookup));
          code = isolate()->stub_cache()->ComputeLoadGlobal(
              name, receiver, global, cell, lookup->IsDontDelete());
        } else {
          // There is only one shared stub for loading normalized
          // properties. It does not traverse the prototype chain, so the
          // property must be found in the receiver for the stub to be
          // applicable.
          if (!holder.is_identical_to(receiver)) return;
          code = isolate()->stub_cache()->ComputeLoadNormal();
        }
        break;
      case CALLBACKS: {
        Handle<Object> callback(lookup->GetCallbackObject());
        if (callback->IsAccessorInfo()) {
          Handle<AccessorInfo> info = Handle<AccessorInfo>::cast(callback);
          if (v8::ToCData<Address>(info->getter()) == 0) return;
          if (!info->IsCompatibleReceiver(*receiver)) return;
          code = isolate()->stub_cache()->ComputeLoadCallback(
              name, receiver, holder, info);
        } else if (callback->IsAccessorPair()) {
          Handle<Object> getter(Handle<AccessorPair>::cast(callback)->getter());
          if (!getter->IsJSFunction()) return;
          if (holder->IsGlobalObject()) return;
          if (!receiver->HasFastProperties()) return;
          code = isolate()->stub_cache()->ComputeLoadViaGetter(
              name, receiver, holder, Handle<JSFunction>::cast(getter));
        } else {
          ASSERT(callback->IsForeign());
          // No IC support for old-style native accessors.
          return;
        }
        break;
      }
      case INTERCEPTOR:
        ASSERT(HasInterceptorGetter(*holder));
        code = isolate()->stub_cache()->ComputeLoadInterceptor(
            name, receiver, holder);
        break;
      default:
        return;
    }
  }

  // Patch the call site depending on the state of the cache.
  if (state == UNINITIALIZED ||
      state == PREMONOMORPHIC ||
      state == MONOMORPHIC_PROTOTYPE_FAILURE) {
    set_target(*code);
  } else if (state == MONOMORPHIC) {
    // We are transitioning from monomorphic to megamorphic case.
    // Place the current monomorphic stub and stub compiled for
    // the receiver into stub cache.
    Map* map = target()->FindFirstMap();
    if (map != NULL) {
      isolate()->stub_cache()->Set(*name, map, target());
    }
    isolate()->stub_cache()->Set(*name, receiver->map(), *code);

    set_target(*megamorphic_stub());
  } else if (state == MEGAMORPHIC) {
    // Cache code holding map should be consistent with
    // GenerateMonomorphicCacheProbe.
    isolate()->stub_cache()->Set(*name, receiver->map(), *code);
  }

  TRACE_IC("LoadIC", name, state, target());
}


Handle<Code> KeyedLoadIC::GetElementStubWithoutMapCheck(
    bool is_js_array,
    ElementsKind elements_kind,
    KeyedAccessGrowMode grow_mode) {
  ASSERT(grow_mode == DO_NOT_ALLOW_JSARRAY_GROWTH);
  return KeyedLoadElementStub(elements_kind).GetCode();
}


Handle<Code> KeyedLoadIC::ComputePolymorphicStub(
    MapHandleList* receiver_maps,
    StrictModeFlag strict_mode,
    KeyedAccessGrowMode growth_mode) {
  CodeHandleList handler_ics(receiver_maps->length());
  for (int i = 0; i < receiver_maps->length(); ++i) {
    Handle<Map> receiver_map = receiver_maps->at(i);
    Handle<Code> cached_stub = ComputeMonomorphicStubWithoutMapCheck(
        receiver_map, strict_mode, growth_mode);
    handler_ics.Add(cached_stub);
  }
  KeyedLoadStubCompiler compiler(isolate());
  Handle<Code> code = compiler.CompileLoadPolymorphic(
      receiver_maps, &handler_ics);
  isolate()->counters()->keyed_load_polymorphic_stubs()->Increment();
  PROFILE(isolate(),
          CodeCreateEvent(Logger::KEYED_LOAD_MEGAMORPHIC_IC_TAG, *code, 0));
  return code;
}


static Handle<Object> TryConvertKey(Handle<Object> key, Isolate* isolate) {
  // This helper implements a few common fast cases for converting
  // non-smi keys of keyed loads/stores to a smi or a string.
  if (key->IsHeapNumber()) {
    double value = Handle<HeapNumber>::cast(key)->value();
    if (isnan(value)) {
      key = isolate->factory()->nan_symbol();
    } else {
      int int_value = FastD2I(value);
      if (value == int_value && Smi::IsValid(int_value)) {
        key = Handle<Smi>(Smi::FromInt(int_value));
      }
    }
  } else if (key->IsUndefined()) {
    key = isolate->factory()->undefined_symbol();
  }
  return key;
}


MaybeObject* KeyedLoadIC::Load(State state,
                               Handle<Object> object,
                               Handle<Object> key,
                               bool force_generic_stub) {
  // Check for values that can be converted into a symbol directly or
  // is representable as a smi.
  key = TryConvertKey(key, isolate());

  if (key->IsSymbol()) {
    Handle<String> name = Handle<String>::cast(key);

    // If the object is undefined or null it's illegal to try to get any
    // of its properties; throw a TypeError in that case.
    if (object->IsUndefined() || object->IsNull()) {
      return TypeError("non_object_property_load", object, name);
    }

    if (FLAG_use_ic) {
      // TODO(1073): don't ignore the current stub state.

      // Use specialized code for getting the length of strings.
      if (object->IsString() &&
          name->Equals(isolate()->heap()->length_symbol())) {
        Handle<String> string = Handle<String>::cast(object);
        Handle<Code> code =
            isolate()->stub_cache()->ComputeKeyedLoadStringLength(name, string);
        ASSERT(!code.is_null());
        set_target(*code);
        TRACE_IC("KeyedLoadIC", name, state, target());
        return Smi::FromInt(string->length());
      }

      // Use specialized code for getting the length of arrays.
      if (object->IsJSArray() &&
          name->Equals(isolate()->heap()->length_symbol())) {
        Handle<JSArray> array = Handle<JSArray>::cast(object);
        Handle<Code> code =
            isolate()->stub_cache()->ComputeKeyedLoadArrayLength(name, array);
        ASSERT(!code.is_null());
        set_target(*code);
        TRACE_IC("KeyedLoadIC", name, state, target());
        return array->length();
      }

      // Use specialized code for getting prototype of functions.
      if (object->IsJSFunction() &&
          name->Equals(isolate()->heap()->prototype_symbol()) &&
          Handle<JSFunction>::cast(object)->should_have_prototype()) {
        Handle<JSFunction> function = Handle<JSFunction>::cast(object);
        Handle<Code> code =
            isolate()->stub_cache()->ComputeKeyedLoadFunctionPrototype(
                name, function);
        ASSERT(!code.is_null());
        set_target(*code);
        TRACE_IC("KeyedLoadIC", name, state, target());
        return Accessors::FunctionGetPrototype(*object, 0);
      }
    }

    // Check if the name is trivially convertible to an index and get
    // the element or char if so.
    uint32_t index = 0;
    if (name->AsArrayIndex(&index)) {
      // Rewrite to the generic keyed load stub.
      if (FLAG_use_ic) set_target(*generic_stub());
      return Runtime::GetElementOrCharAt(isolate(), object, index);
    }

    // Named lookup.
    LookupResult lookup(isolate());
    LookupForRead(object, name, &lookup);

    // If we did not find a property, check if we need to throw an exception.
    if (!lookup.IsProperty() && IsContextual(object)) {
      return ReferenceError("not_defined", name);
    }

    if (FLAG_use_ic) {
      UpdateCaches(&lookup, state, object, name);
    }

    PropertyAttributes attr;
    if (lookup.IsFound() && lookup.type() == INTERCEPTOR) {
      // Get the property.
      Handle<Object> result =
          Object::GetProperty(object, object, &lookup, name, &attr);
      RETURN_IF_EMPTY_HANDLE(isolate(), result);
      // If the property is not present, check if we need to throw an
      // exception.
      if (attr == ABSENT && IsContextual(object)) {
        return ReferenceError("not_defined", name);
      }
      return *result;
    }

    return object->GetProperty(*object, &lookup, *name, &attr);
  }

  // Do not use ICs for objects that require access checks (including
  // the global object).
  bool use_ic = FLAG_use_ic && !object->IsAccessCheckNeeded();

  if (use_ic) {
    Handle<Code> stub = generic_stub();
    if (!force_generic_stub) {
      if (object->IsString() && key->IsNumber()) {
        if (state == UNINITIALIZED) {
          stub = string_stub();
        }
      } else if (object->IsJSObject()) {
        Handle<JSObject> receiver = Handle<JSObject>::cast(object);
        if (receiver->elements()->map() ==
            isolate()->heap()->non_strict_arguments_elements_map()) {
          stub = non_strict_arguments_stub();
        } else if (receiver->HasIndexedInterceptor()) {
          stub = indexed_interceptor_stub();
        } else if (key->IsSmi() && (target() != *non_strict_arguments_stub())) {
          stub = ComputeStub(receiver, LOAD, kNonStrictMode, stub);
        }
      }
    } else {
      TRACE_GENERIC_IC("KeyedLoadIC", "force generic");
    }
    if (!stub.is_null()) set_target(*stub);
  }

  TRACE_IC("KeyedLoadIC", key, state, target());

  // Get the property.
  return Runtime::GetObjectProperty(isolate(), object, key);
}


void KeyedLoadIC::UpdateCaches(LookupResult* lookup,
                               State state,
                               Handle<Object> object,
                               Handle<String> name) {
  // Bail out if we didn't find a result.
  if (!lookup->IsProperty() || !lookup->IsCacheable()) return;

  if (!object->IsJSObject()) return;
  Handle<JSObject> receiver = Handle<JSObject>::cast(object);

  if (HasNormalObjectsInPrototypeChain(isolate(), lookup, *object)) return;

  // Compute the code stub for this load.
  Handle<Code> code;

  if (state == UNINITIALIZED) {
    // This is the first time we execute this inline cache.
    // Set the target to the pre monomorphic stub to delay
    // setting the monomorphic state.
    code = pre_monomorphic_stub();
  } else {
    // Compute a monomorphic stub.
    Handle<JSObject> holder(lookup->holder());
    switch (lookup->type()) {
      case FIELD:
        code = isolate()->stub_cache()->ComputeKeyedLoadField(
            name, receiver, holder, lookup->GetFieldIndex());
        break;
      case CONSTANT_FUNCTION: {
        Handle<JSFunction> constant(lookup->GetConstantFunction());
        code = isolate()->stub_cache()->ComputeKeyedLoadConstant(
            name, receiver, holder, constant);
        break;
      }
      case CALLBACKS: {
        Handle<Object> callback_object(lookup->GetCallbackObject());
        if (!callback_object->IsAccessorInfo()) return;
        Handle<AccessorInfo> callback =
            Handle<AccessorInfo>::cast(callback_object);
        if (v8::ToCData<Address>(callback->getter()) == 0) return;
        if (!callback->IsCompatibleReceiver(*receiver)) return;
        code = isolate()->stub_cache()->ComputeKeyedLoadCallback(
            name, receiver, holder, callback);
        break;
      }
      case INTERCEPTOR:
        ASSERT(HasInterceptorGetter(lookup->holder()));
        code = isolate()->stub_cache()->ComputeKeyedLoadInterceptor(
            name, receiver, holder);
        break;
      default:
        // Always rewrite to the generic case so that we do not
        // repeatedly try to rewrite.
        code = generic_stub();
        break;
    }
  }

  // Patch the call site depending on the state of the cache.  Make
  // sure to always rewrite from monomorphic to megamorphic.
  ASSERT(state != MONOMORPHIC_PROTOTYPE_FAILURE);
  if (state == UNINITIALIZED || state == PREMONOMORPHIC) {
    set_target(*code);
  } else if (state == MONOMORPHIC) {
    set_target(*megamorphic_stub());
  }

  TRACE_IC("KeyedLoadIC", name, state, target());
}


static bool StoreICableLookup(LookupResult* lookup) {
  // Bail out if we didn't find a result.
  if (!lookup->IsFound() || lookup->type() == NULL_DESCRIPTOR) return false;

  // Bail out if inline caching is not allowed.
  if (!lookup->IsCacheable()) return false;

  // If the property is read-only, we leave the IC in its current state.
  if (lookup->IsReadOnly()) return false;

  return true;
}


static bool LookupForWrite(Handle<JSObject> receiver,
                           Handle<String> name,
                           LookupResult* lookup) {
  receiver->LocalLookup(*name, lookup);
  if (!StoreICableLookup(lookup)) {
    return false;
  }

  if (lookup->type() == INTERCEPTOR &&
      receiver->GetNamedInterceptor()->setter()->IsUndefined()) {
    receiver->LocalLookupRealNamedProperty(*name, lookup);
    return StoreICableLookup(lookup);
  }

  return true;
}


MaybeObject* StoreIC::Store(State state,
                            StrictModeFlag strict_mode,
                            Handle<Object> object,
                            Handle<String> name,
                            Handle<Object> value) {
  if (!object->IsJSObject()) {
    // Handle proxies.
    if (object->IsJSProxy()) {
      return JSProxy::cast(*object)->
          SetProperty(*name, *value, NONE, strict_mode);
    }

    // If the object is undefined or null it's illegal to try to set any
    // properties on it; throw a TypeError in that case.
    if (object->IsUndefined() || object->IsNull()) {
      return TypeError("non_object_property_store", object, name);
    }

    // The length property of string values is read-only. Throw in strict mode.
    if (strict_mode == kStrictMode && object->IsString() &&
        name->Equals(isolate()->heap()->length_symbol())) {
      return TypeError("strict_read_only_property", object, name);
    }
    // Ignore other stores where the receiver is not a JSObject.
    // TODO(1475): Must check prototype chains of object wrappers.
    return *value;
  }

  Handle<JSObject> receiver = Handle<JSObject>::cast(object);

  // Check if the given name is an array index.
  uint32_t index;
  if (name->AsArrayIndex(&index)) {
    Handle<Object> result =
        JSObject::SetElement(receiver, index, value, NONE, strict_mode);
    RETURN_IF_EMPTY_HANDLE(isolate(), result);
    return *value;
  }

  // Use specialized code for setting the length of arrays with fast
  // properties.  Slow properties might indicate redefinition of the
  // length property.
  if (receiver->IsJSArray() &&
      name->Equals(isolate()->heap()->length_symbol()) &&
      Handle<JSArray>::cast(receiver)->AllowsSetElementsLength() &&
      receiver->HasFastProperties()) {
#ifdef DEBUG
    if (FLAG_trace_ic) PrintF("[StoreIC : +#length /array]\n");
#endif
    Handle<Code> stub = (strict_mode == kStrictMode)
        ? isolate()->builtins()->StoreIC_ArrayLength_Strict()
        : isolate()->builtins()->StoreIC_ArrayLength();
    set_target(*stub);
    return receiver->SetProperty(*name, *value, NONE, strict_mode);
  }

  // Lookup the property locally in the receiver.
  if (FLAG_use_ic && !receiver->IsJSGlobalProxy()) {
    LookupResult lookup(isolate());

    if (LookupForWrite(receiver, name, &lookup)) {
      // Generate a stub for this store.
      UpdateCaches(&lookup, state, strict_mode, receiver, name, value);
    } else {
      // Strict mode doesn't allow setting non-existent global property
      // or an assignment to a read only property.
      if (strict_mode == kStrictMode) {
        if (lookup.IsProperty() && lookup.IsReadOnly()) {
          return TypeError("strict_read_only_property", object, name);
        } else if (IsContextual(object)) {
          return ReferenceError("not_defined", name);
        }
      }
    }
  }

  if (receiver->IsJSGlobalProxy()) {
    // TODO(ulan): find out why we patch this site even with --no-use-ic
    // Generate a generic stub that goes to the runtime when we see a global
    // proxy as receiver.
    Handle<Code> stub = (strict_mode == kStrictMode)
        ? global_proxy_stub_strict()
        : global_proxy_stub();
    if (target() != *stub) {
      set_target(*stub);
      TRACE_IC("StoreIC", name, state, target());
    }
  }

  // Set the property.
  return receiver->SetProperty(*name,
                               *value,
                               NONE,
                               strict_mode,
                               JSReceiver::CERTAINLY_NOT_STORE_FROM_KEYED);
}


void StoreIC::UpdateCaches(LookupResult* lookup,
                           State state,
                           StrictModeFlag strict_mode,
                           Handle<JSObject> receiver,
                           Handle<String> name,
                           Handle<Object> value) {
  ASSERT(!receiver->IsJSGlobalProxy());
  ASSERT(StoreICableLookup(lookup));
  // These are not cacheable, so we never see such LookupResults here.
  ASSERT(lookup->type() != HANDLER);
  // We get only called for properties or transitions, see StoreICableLookup.
  ASSERT(lookup->type() != NULL_DESCRIPTOR);

  // If the property has a non-field type allowing map transitions
  // where there is extra room in the object, we leave the IC in its
  // current state.
  PropertyType type = lookup->type();

  // Compute the code stub for this store; used for rewriting to
  // monomorphic state and making sure that the code stub is in the
  // stub cache.
  Handle<JSObject> holder(lookup->holder());
  Handle<Code> code;
  switch (type) {
    case FIELD:
      code = isolate()->stub_cache()->ComputeStoreField(name,
                                                        receiver,
                                                        lookup->GetFieldIndex(),
                                                        Handle<Map>::null(),
                                                        strict_mode);
      break;
    case MAP_TRANSITION: {
      if (lookup->GetAttributes() != NONE) return;
      Handle<Map> transition(lookup->GetTransitionMap());
      int index = transition->PropertyIndexFor(*name);
      code = isolate()->stub_cache()->ComputeStoreField(
          name, receiver, index, transition, strict_mode);
      break;
    }
    case NORMAL:
      if (receiver->IsGlobalObject()) {
        // The stub generated for the global object picks the value directly
        // from the property cell. So the property must be directly on the
        // global object.
        Handle<GlobalObject> global = Handle<GlobalObject>::cast(receiver);
        Handle<JSGlobalPropertyCell> cell(global->GetPropertyCell(lookup));
        code = isolate()->stub_cache()->ComputeStoreGlobal(
            name, global, cell, strict_mode);
      } else {
        if (!holder.is_identical_to(receiver)) return;
        code = isolate()->stub_cache()->ComputeStoreNormal(strict_mode);
      }
      break;
    case CALLBACKS: {
      Handle<Object> callback(lookup->GetCallbackObject());
      if (callback->IsAccessorInfo()) {
        Handle<AccessorInfo> info = Handle<AccessorInfo>::cast(callback);
        if (v8::ToCData<Address>(info->setter()) == 0) return;
        ASSERT(info->IsCompatibleReceiver(*receiver));
        code = isolate()->stub_cache()->ComputeStoreCallback(
            name, receiver, info, strict_mode);
      } else if (callback->IsAccessorPair()) {
        Handle<Object> setter(Handle<AccessorPair>::cast(callback)->setter());
        if (!setter->IsJSFunction()) return;
        if (holder->IsGlobalObject()) return;
        if (!receiver->HasFastProperties()) return;
        code = isolate()->stub_cache()->ComputeStoreViaSetter(
            name, receiver, Handle<JSFunction>::cast(setter), strict_mode);
      } else {
        ASSERT(callback->IsForeign());
        // No IC support for old-style native accessors.
        return;
      }
      break;
    }
    case INTERCEPTOR:
      ASSERT(!receiver->GetNamedInterceptor()->setter()->IsUndefined());
      code = isolate()->stub_cache()->ComputeStoreInterceptor(
          name, receiver, strict_mode);
      break;
    case CONSTANT_FUNCTION:
    case CONSTANT_TRANSITION:
      return;
    case HANDLER:
    case NULL_DESCRIPTOR:
      UNREACHABLE();
      return;
  }

  // Patch the call site depending on the state of the cache.
  if (state == UNINITIALIZED || state == MONOMORPHIC_PROTOTYPE_FAILURE) {
    set_target(*code);
  } else if (state == MONOMORPHIC) {
    // Only move to megamorphic if the target changes.
    if (target() != *code) {
      set_target((strict_mode == kStrictMode)
                   ? megamorphic_stub_strict()
                   : megamorphic_stub());
    }
  } else if (state == MEGAMORPHIC) {
    // Update the stub cache.
    isolate()->stub_cache()->Set(*name, receiver->map(), *code);
  }

  TRACE_IC("StoreIC", name, state, target());
}


static bool AddOneReceiverMapIfMissing(MapHandleList* receiver_maps,
                                       Handle<Map> new_receiver_map) {
  ASSERT(!new_receiver_map.is_null());
  for (int current = 0; current < receiver_maps->length(); ++current) {
    if (!receiver_maps->at(current).is_null() &&
        receiver_maps->at(current).is_identical_to(new_receiver_map)) {
      return false;
    }
  }
  receiver_maps->Add(new_receiver_map);
  return true;
}


void KeyedIC::GetReceiverMapsForStub(Handle<Code> stub,
                                     MapHandleList* result) {
  ASSERT(stub->is_inline_cache_stub());
  if (!string_stub().is_null() && stub.is_identical_to(string_stub())) {
    return result->Add(isolate()->factory()->string_map());
  } else if (stub->is_keyed_load_stub() || stub->is_keyed_store_stub()) {
    if (stub->ic_state() == MONOMORPHIC) {
      result->Add(Handle<Map>(stub->FindFirstMap()));
    } else {
      ASSERT(stub->ic_state() == MEGAMORPHIC);
      AssertNoAllocation no_allocation;
      int mask = RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
      for (RelocIterator it(*stub, mask); !it.done(); it.next()) {
        RelocInfo* info = it.rinfo();
        Handle<Object> object(info->target_object());
        ASSERT(object->IsMap());
        AddOneReceiverMapIfMissing(result, Handle<Map>::cast(object));
      }
    }
  }
}


Handle<Code> KeyedIC::ComputeStub(Handle<JSObject> receiver,
                                  StubKind stub_kind,
                                  StrictModeFlag strict_mode,
                                  Handle<Code> generic_stub) {
  State ic_state = target()->ic_state();
  KeyedAccessGrowMode grow_mode = IsGrowStubKind(stub_kind)
      ? ALLOW_JSARRAY_GROWTH
      : DO_NOT_ALLOW_JSARRAY_GROWTH;

  // Don't handle megamorphic property accesses for INTERCEPTORS or CALLBACKS
  // via megamorphic stubs, since they don't have a map in their relocation info
  // and so the stubs can't be harvested for the object needed for a map check.
  if (target()->type() != NORMAL) {
    TRACE_GENERIC_IC("KeyedIC", "non-NORMAL target type");
    return generic_stub;
  }

  bool monomorphic = false;
  bool is_transition_stub = IsTransitionStubKind(stub_kind);
  Handle<Map> receiver_map(receiver->map());
  Handle<Map> monomorphic_map = receiver_map;
  MapHandleList target_receiver_maps;
  if (ic_state == UNINITIALIZED || ic_state == PREMONOMORPHIC) {
    // Optimistically assume that ICs that haven't reached the MONOMORPHIC state
    // yet will do so and stay there.
    monomorphic = true;
  } else {
    GetReceiverMapsForStub(Handle<Code>(target()), &target_receiver_maps);
    if (ic_state == MONOMORPHIC && is_transition_stub) {
      // 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.
      monomorphic = IsMoreGeneralElementsKindTransition(
          target_receiver_maps.at(0)->elements_kind(),
          receiver->GetElementsKind());
    }
  }

  if (monomorphic) {
    if (is_transition_stub) {
      monomorphic_map = ComputeTransitionedMap(receiver, stub_kind);
      ASSERT(*monomorphic_map != *receiver_map);
      stub_kind = GetNoTransitionStubKind(stub_kind);
    }
    return ComputeMonomorphicStub(
        monomorphic_map, stub_kind, strict_mode, generic_stub);
  }
  ASSERT(target() != *generic_stub);

  // Determine the list of receiver maps that this call site has seen,
  // adding the map that was just encountered.
  bool map_added =
      AddOneReceiverMapIfMissing(&target_receiver_maps, receiver_map);
  if (IsTransitionStubKind(stub_kind)) {
    Handle<Map> new_map = ComputeTransitionedMap(receiver, stub_kind);
    map_added |= AddOneReceiverMapIfMissing(&target_receiver_maps, new_map);
  }
  if (!map_added) {
    // If the miss wasn't due to an unseen map, a polymorphic stub
    // won't help, use the generic stub.
    TRACE_GENERIC_IC("KeyedIC", "same map added twice");
    return generic_stub;
  }

  // If the maximum number of receiver maps has been exceeded, use the generic
  // version of the IC.
  if (target_receiver_maps.length() > kMaxKeyedPolymorphism) {
    TRACE_GENERIC_IC("KeyedIC", "max polymorph exceeded");
    return generic_stub;
  }

  if ((Code::GetKeyedAccessGrowMode(target()->extra_ic_state()) ==
       ALLOW_JSARRAY_GROWTH)) {
    grow_mode = ALLOW_JSARRAY_GROWTH;
  }

  Handle<PolymorphicCodeCache> cache =
      isolate()->factory()->polymorphic_code_cache();
  Code::ExtraICState extra_state = Code::ComputeExtraICState(grow_mode,
                                                             strict_mode);
  Code::Flags flags = Code::ComputeFlags(kind(), MEGAMORPHIC, extra_state);
  Handle<Object> probe = cache->Lookup(&target_receiver_maps, flags);
  if (probe->IsCode()) return Handle<Code>::cast(probe);

  Handle<Code> stub =
      ComputePolymorphicStub(&target_receiver_maps, strict_mode, grow_mode);
  PolymorphicCodeCache::Update(cache, &target_receiver_maps, flags, stub);
  return stub;
}


Handle<Code> KeyedIC::ComputeMonomorphicStubWithoutMapCheck(
    Handle<Map> receiver_map,
    StrictModeFlag strict_mode,
    KeyedAccessGrowMode grow_mode) {
  if ((receiver_map->instance_type() & kNotStringTag) == 0) {
    ASSERT(!string_stub().is_null());
    return string_stub();
  } else {
    ASSERT(receiver_map->has_dictionary_elements() ||
           receiver_map->has_fast_smi_or_object_elements() ||
           receiver_map->has_fast_double_elements() ||
           receiver_map->has_external_array_elements());
    bool is_js_array = receiver_map->instance_type() == JS_ARRAY_TYPE;
    return GetElementStubWithoutMapCheck(is_js_array,
                                         receiver_map->elements_kind(),
                                         grow_mode);
  }
}


Handle<Code> KeyedIC::ComputeMonomorphicStub(Handle<Map> receiver_map,
                                             StubKind stub_kind,
                                             StrictModeFlag strict_mode,
                                             Handle<Code> generic_stub) {
  ElementsKind elements_kind = receiver_map->elements_kind();
  if (IsFastElementsKind(elements_kind) ||
      IsExternalArrayElementsKind(elements_kind) ||
      IsDictionaryElementsKind(elements_kind)) {
    return isolate()->stub_cache()->ComputeKeyedLoadOrStoreElement(
        receiver_map, stub_kind, strict_mode);
  } else {
    return generic_stub;
  }
}


Handle<Map> KeyedIC::ComputeTransitionedMap(Handle<JSObject> receiver,
                                            StubKind stub_kind) {
  switch (stub_kind) {
    case KeyedIC::STORE_TRANSITION_SMI_TO_OBJECT:
    case KeyedIC::STORE_TRANSITION_DOUBLE_TO_OBJECT:
    case KeyedIC::STORE_AND_GROW_TRANSITION_SMI_TO_OBJECT:
    case KeyedIC::STORE_AND_GROW_TRANSITION_DOUBLE_TO_OBJECT:
      return JSObject::GetElementsTransitionMap(receiver, FAST_ELEMENTS);
    case KeyedIC::STORE_TRANSITION_SMI_TO_DOUBLE:
    case KeyedIC::STORE_AND_GROW_TRANSITION_SMI_TO_DOUBLE:
      return JSObject::GetElementsTransitionMap(receiver, FAST_DOUBLE_ELEMENTS);
    case KeyedIC::STORE_TRANSITION_HOLEY_SMI_TO_OBJECT:
    case KeyedIC::STORE_TRANSITION_HOLEY_DOUBLE_TO_OBJECT:
    case KeyedIC::STORE_AND_GROW_TRANSITION_HOLEY_SMI_TO_OBJECT:
    case KeyedIC::STORE_AND_GROW_TRANSITION_HOLEY_DOUBLE_TO_OBJECT:
      return JSObject::GetElementsTransitionMap(receiver,
                                                FAST_HOLEY_ELEMENTS);
    case KeyedIC::STORE_TRANSITION_HOLEY_SMI_TO_DOUBLE:
    case KeyedIC::STORE_AND_GROW_TRANSITION_HOLEY_SMI_TO_DOUBLE:
      return JSObject::GetElementsTransitionMap(receiver,
                                                FAST_HOLEY_DOUBLE_ELEMENTS);
    case KeyedIC::LOAD:
    case KeyedIC::STORE_NO_TRANSITION:
    case KeyedIC::STORE_AND_GROW_NO_TRANSITION:
      UNREACHABLE();
      break;
  }
  return Handle<Map>::null();
}


Handle<Code> KeyedStoreIC::GetElementStubWithoutMapCheck(
    bool is_js_array,
    ElementsKind elements_kind,
    KeyedAccessGrowMode grow_mode) {
  return KeyedStoreElementStub(is_js_array, elements_kind, grow_mode).GetCode();
}


Handle<Code> KeyedStoreIC::ComputePolymorphicStub(
    MapHandleList* receiver_maps,
    StrictModeFlag strict_mode,
    KeyedAccessGrowMode grow_mode) {
  // Collect MONOMORPHIC stubs for all target_receiver_maps.
  CodeHandleList handler_ics(receiver_maps->length());
  MapHandleList transitioned_maps(receiver_maps->length());
  for (int i = 0; i < receiver_maps->length(); ++i) {
    Handle<Map> receiver_map(receiver_maps->at(i));
    Handle<Code> cached_stub;
    Handle<Map> transitioned_map =
        receiver_map->FindTransitionedMap(receiver_maps);
    if (!transitioned_map.is_null()) {
      cached_stub = ElementsTransitionAndStoreStub(
          receiver_map->elements_kind(),  // original elements_kind
          transitioned_map->elements_kind(),
          receiver_map->instance_type() == JS_ARRAY_TYPE,  // is_js_array
          strict_mode, grow_mode).GetCode();
    } else {
      cached_stub = ComputeMonomorphicStubWithoutMapCheck(receiver_map,
                                                          strict_mode,
                                                          grow_mode);
    }
    ASSERT(!cached_stub.is_null());
    handler_ics.Add(cached_stub);
    transitioned_maps.Add(transitioned_map);
  }
  KeyedStoreStubCompiler compiler(isolate(), strict_mode, grow_mode);
  Handle<Code> code = compiler.CompileStorePolymorphic(
      receiver_maps, &handler_ics, &transitioned_maps);
  isolate()->counters()->keyed_store_polymorphic_stubs()->Increment();
  PROFILE(isolate(),
          CodeCreateEvent(Logger::KEYED_STORE_MEGAMORPHIC_IC_TAG, *code, 0));
  return code;
}


KeyedIC::StubKind KeyedStoreIC::GetStubKind(Handle<JSObject> receiver,
                                            Handle<Object> key,
                                            Handle<Object> value) {
  ASSERT(key->IsSmi());
  int index = Smi::cast(*key)->value();
  bool allow_growth = receiver->IsJSArray() &&
      JSArray::cast(*receiver)->length()->IsSmi() &&
      index >= Smi::cast(JSArray::cast(*receiver)->length())->value();

  if (allow_growth) {
    // Handle growing array in stub if necessary.
    if (receiver->HasFastSmiElements()) {
      if (value->IsHeapNumber()) {
        if (receiver->HasFastHoleyElements()) {
          return STORE_AND_GROW_TRANSITION_HOLEY_SMI_TO_DOUBLE;
        } else {
          return STORE_AND_GROW_TRANSITION_SMI_TO_DOUBLE;
        }
      }
      if (value->IsHeapObject()) {
        if (receiver->HasFastHoleyElements()) {
          return STORE_AND_GROW_TRANSITION_HOLEY_SMI_TO_OBJECT;
        } else {
          return STORE_AND_GROW_TRANSITION_SMI_TO_OBJECT;
        }
      }
    } else if (receiver->HasFastDoubleElements()) {
      if (!value->IsSmi() && !value->IsHeapNumber()) {
        if (receiver->HasFastHoleyElements()) {
          return STORE_AND_GROW_TRANSITION_HOLEY_DOUBLE_TO_OBJECT;
        } else {
          return STORE_AND_GROW_TRANSITION_DOUBLE_TO_OBJECT;
        }
      }
    }
    return STORE_AND_GROW_NO_TRANSITION;
  } else {
    // Handle only in-bounds elements accesses.
    if (receiver->HasFastSmiElements()) {
      if (value->IsHeapNumber()) {
        if (receiver->HasFastHoleyElements()) {
          return STORE_TRANSITION_HOLEY_SMI_TO_DOUBLE;
        } else {
          return STORE_TRANSITION_SMI_TO_DOUBLE;
        }
      } else if (value->IsHeapObject()) {
        if (receiver->HasFastHoleyElements()) {
          return STORE_TRANSITION_HOLEY_SMI_TO_OBJECT;
        } else {
          return STORE_TRANSITION_SMI_TO_OBJECT;
        }
      }
    } else if (receiver->HasFastDoubleElements()) {
      if (!value->IsSmi() && !value->IsHeapNumber()) {
        if (receiver->HasFastHoleyElements()) {
          return STORE_TRANSITION_HOLEY_DOUBLE_TO_OBJECT;
        } else {
          return STORE_TRANSITION_DOUBLE_TO_OBJECT;
        }
      }
    }
    return STORE_NO_TRANSITION;
  }
}


MaybeObject* KeyedStoreIC::Store(State state,
                                 StrictModeFlag strict_mode,
                                 Handle<Object> object,
                                 Handle<Object> key,
                                 Handle<Object> value,
                                 bool force_generic) {
  // Check for values that can be converted into a symbol directly or
  // is representable as a smi.
  key = TryConvertKey(key, isolate());

  if (key->IsSymbol()) {
    Handle<String> name = Handle<String>::cast(key);

    // Handle proxies.
    if (object->IsJSProxy()) {
      return JSProxy::cast(*object)->SetProperty(
          *name, *value, NONE, strict_mode);
    }

    // If the object is undefined or null it's illegal to try to set any
    // properties on it; throw a TypeError in that case.
    if (object->IsUndefined() || object->IsNull()) {
      return TypeError("non_object_property_store", object, name);
    }

    // Ignore stores where the receiver is not a JSObject.
    if (!object->IsJSObject()) return *value;
    Handle<JSObject> receiver = Handle<JSObject>::cast(object);

    // Check if the given name is an array index.
    uint32_t index;
    if (name->AsArrayIndex(&index)) {
      Handle<Object> result =
          JSObject::SetElement(receiver, index, value, NONE, strict_mode);
      RETURN_IF_EMPTY_HANDLE(isolate(), result);
      return *value;
    }

    // Update inline cache and stub cache.
    if (FLAG_use_ic && !receiver->IsJSGlobalProxy()) {
      LookupResult lookup(isolate());
      if (LookupForWrite(receiver, name, &lookup)) {
        UpdateCaches(&lookup, state, strict_mode, receiver, name, value);
      }
    }

    // Set the property.
    return receiver->SetProperty(*name, *value, NONE, strict_mode);
  }

  // Do not use ICs for objects that require access checks (including
  // the global object).
  bool use_ic = FLAG_use_ic && !object->IsAccessCheckNeeded();
  ASSERT(!(use_ic && object->IsJSGlobalProxy()));

  if (use_ic) {
    Handle<Code> stub = (strict_mode == kStrictMode)
        ? generic_stub_strict()
        : generic_stub();
    if (object->IsJSObject()) {
      Handle<JSObject> receiver = Handle<JSObject>::cast(object);
      if (receiver->elements()->map() ==
          isolate()->heap()->non_strict_arguments_elements_map()) {
        stub = non_strict_arguments_stub();
      } else if (!force_generic) {
        if (key->IsSmi() && (target() != *non_strict_arguments_stub())) {
          StubKind stub_kind = GetStubKind(receiver, key, value);
          stub = ComputeStub(receiver, stub_kind, strict_mode, stub);
        }
      } else {
        TRACE_GENERIC_IC("KeyedStoreIC", "force generic");
      }
    }
    if (!stub.is_null()) set_target(*stub);
  }

  TRACE_IC("KeyedStoreIC", key, state, target());

  // Set the property.
  return Runtime::SetObjectProperty(
      isolate(), object , key, value, NONE, strict_mode);
}


void KeyedStoreIC::UpdateCaches(LookupResult* lookup,
                                State state,
                                StrictModeFlag strict_mode,
                                Handle<JSObject> receiver,
                                Handle<String> name,
                                Handle<Object> value) {
  ASSERT(!receiver->IsJSGlobalProxy());
  ASSERT(StoreICableLookup(lookup));
  // These are not cacheable, so we never see such LookupResults here.
  ASSERT(lookup->type() != HANDLER);
  // We get only called for properties or transitions, see StoreICableLookup.
  ASSERT(lookup->type() != NULL_DESCRIPTOR);

  // If the property has a non-field type allowing map transitions
  // where there is extra room in the object, we leave the IC in its
  // current state.
  PropertyType type = lookup->type();

  // Compute the code stub for this store; used for rewriting to
  // monomorphic state and making sure that the code stub is in the
  // stub cache.
  Handle<Code> code;

  switch (type) {
    case FIELD:
      code = isolate()->stub_cache()->ComputeKeyedStoreField(
          name, receiver, lookup->GetFieldIndex(),
          Handle<Map>::null(), strict_mode);
      break;
    case MAP_TRANSITION:
      if (lookup->GetAttributes() == NONE) {
        Handle<Map> transition(lookup->GetTransitionMap());
        int index = transition->PropertyIndexFor(*name);
        code = isolate()->stub_cache()->ComputeKeyedStoreField(
            name, receiver, index, transition, strict_mode);
        break;
      }
      // fall through.
    case NORMAL:
    case CONSTANT_FUNCTION:
    case CALLBACKS:
    case INTERCEPTOR:
    case CONSTANT_TRANSITION:
      // Always rewrite to the generic case so that we do not
      // repeatedly try to rewrite.
      code = (strict_mode == kStrictMode)
          ? generic_stub_strict()
          : generic_stub();
      break;
    case HANDLER:
    case NULL_DESCRIPTOR:
      UNREACHABLE();
      return;
  }

  ASSERT(!code.is_null());

  // Patch the call site depending on the state of the cache.  Make
  // sure to always rewrite from monomorphic to megamorphic.
  ASSERT(state != MONOMORPHIC_PROTOTYPE_FAILURE);
  if (state == UNINITIALIZED || state == PREMONOMORPHIC) {
    set_target(*code);
  } else if (state == MONOMORPHIC) {
    set_target((strict_mode == kStrictMode)
                 ? *megamorphic_stub_strict()
                 : *megamorphic_stub());
  }

  TRACE_IC("KeyedStoreIC", name, state, target());
}


#undef TRACE_IC


// ----------------------------------------------------------------------------
// Static IC stub generators.
//

// Used from ic-<arch>.cc.
RUNTIME_FUNCTION(MaybeObject*, CallIC_Miss) {
  HandleScope scope(isolate);
  ASSERT(args.length() == 2);
  CallIC ic(isolate);
  IC::State state = IC::StateFrom(ic.target(), args[0], args[1]);
  Code::ExtraICState extra_ic_state = ic.target()->extra_ic_state();
  MaybeObject* maybe_result = ic.LoadFunction(state,
                                              extra_ic_state,
                                              args.at<Object>(0),
                                              args.at<String>(1));
  // Result could be a function or a failure.
  JSFunction* raw_function = NULL;
  if (!maybe_result->To(&raw_function)) return maybe_result;

  // The first time the inline cache is updated may be the first time the
  // function it references gets called.  If the function is lazily compiled
  // then the first call will trigger a compilation.  We check for this case
  // and we do the compilation immediately, instead of waiting for the stub
  // currently attached to the JSFunction object to trigger compilation.
  if (raw_function->is_compiled()) return raw_function;

  Handle<JSFunction> function(raw_function);
  JSFunction::CompileLazy(function, CLEAR_EXCEPTION);
  return *function;
}


// Used from ic-<arch>.cc.
RUNTIME_FUNCTION(MaybeObject*, KeyedCallIC_Miss) {
  HandleScope scope(isolate);
  ASSERT(args.length() == 2);
  KeyedCallIC ic(isolate);
  IC::State state = IC::StateFrom(ic.target(), args[0], args[1]);
  MaybeObject* maybe_result =
      ic.LoadFunction(state, args.at<Object>(0), args.at<Object>(1));
  // Result could be a function or a failure.
  JSFunction* raw_function = NULL;
  if (!maybe_result->To(&raw_function)) return maybe_result;

  if (raw_function->is_compiled()) return raw_function;

  Handle<JSFunction> function(raw_function);
  JSFunction::CompileLazy(function, CLEAR_EXCEPTION);
  return *function;
}


// Used from ic-<arch>.cc.
RUNTIME_FUNCTION(MaybeObject*, LoadIC_Miss) {
  HandleScope scope(isolate);
  ASSERT(args.length() == 2);
  LoadIC ic(isolate);
  IC::State state = IC::StateFrom(ic.target(), args[0], args[1]);
  return ic.Load(state, args.at<Object>(0), args.at<String>(1));
}


// Used from ic-<arch>.cc
RUNTIME_FUNCTION(MaybeObject*, KeyedLoadIC_Miss) {
  HandleScope scope(isolate);
  ASSERT(args.length() == 2);
  KeyedLoadIC ic(isolate);
  IC::State state = IC::StateFrom(ic.target(), args[0], args[1]);
  return ic.Load(state, args.at<Object>(0), args.at<Object>(1), false);
}


RUNTIME_FUNCTION(MaybeObject*, KeyedLoadIC_MissForceGeneric) {
  HandleScope scope(isolate);
  ASSERT(args.length() == 2);
  KeyedLoadIC ic(isolate);
  IC::State state = IC::StateFrom(ic.target(), args[0], args[1]);
  return ic.Load(state, args.at<Object>(0), args.at<Object>(1), true);
}


// Used from ic-<arch>.cc.
RUNTIME_FUNCTION(MaybeObject*, StoreIC_Miss) {
  HandleScope scope;
  ASSERT(args.length() == 3);
  StoreIC ic(isolate);
  IC::State state = IC::StateFrom(ic.target(), args[0], args[1]);
  Code::ExtraICState extra_ic_state = ic.target()->extra_ic_state();
  return ic.Store(state,
                  Code::GetStrictMode(extra_ic_state),
                  args.at<Object>(0),
                  args.at<String>(1),
                  args.at<Object>(2));
}


RUNTIME_FUNCTION(MaybeObject*, StoreIC_ArrayLength) {
  NoHandleAllocation nha;

  ASSERT(args.length() == 2);
  JSArray* receiver = JSArray::cast(args[0]);
  Object* len = args[1];

  // The generated code should filter out non-Smis before we get here.
  ASSERT(len->IsSmi());

#ifdef DEBUG
  // The length property has to be a writable callback property.
  LookupResult debug_lookup(isolate);
  receiver->LocalLookup(isolate->heap()->length_symbol(), &debug_lookup);
  ASSERT(debug_lookup.type() == CALLBACKS && !debug_lookup.IsReadOnly());
#endif

  Object* result;
  { MaybeObject* maybe_result = receiver->SetElementsLength(len);
    if (!maybe_result->ToObject(&result)) return maybe_result;
  }
  return len;
}


// Extend storage is called in a store inline cache when
// it is necessary to extend the properties array of a
// JSObject.
RUNTIME_FUNCTION(MaybeObject*, SharedStoreIC_ExtendStorage) {
  NoHandleAllocation na;
  ASSERT(args.length() == 3);

  // Convert the parameters
  JSObject* object = JSObject::cast(args[0]);
  Map* transition = Map::cast(args[1]);
  Object* value = args[2];

  // Check the object has run out out property space.
  ASSERT(object->HasFastProperties());
  ASSERT(object->map()->unused_property_fields() == 0);

  // Expand the properties array.
  FixedArray* old_storage = object->properties();
  int new_unused = transition->unused_property_fields();
  int new_size = old_storage->length() + new_unused + 1;
  Object* result;
  { MaybeObject* maybe_result = old_storage->CopySize(new_size);
    if (!maybe_result->ToObject(&result)) return maybe_result;
  }
  FixedArray* new_storage = FixedArray::cast(result);
  new_storage->set(old_storage->length(), value);

  // Set the new property value and do the map transition.
  object->set_properties(new_storage);
  object->set_map(transition);

  // Return the stored value.
  return value;
}


// Used from ic-<arch>.cc.
RUNTIME_FUNCTION(MaybeObject*, KeyedStoreIC_Miss) {
  HandleScope scope(isolate);
  ASSERT(args.length() == 3);
  KeyedStoreIC ic(isolate);
  IC::State state = IC::StateFrom(ic.target(), args[0], args[1]);
  Code::ExtraICState extra_ic_state = ic.target()->extra_ic_state();
  return ic.Store(state,
                  Code::GetStrictMode(extra_ic_state),
                  args.at<Object>(0),
                  args.at<Object>(1),
                  args.at<Object>(2),
                  false);
}


RUNTIME_FUNCTION(MaybeObject*, KeyedStoreIC_Slow) {
  NoHandleAllocation na;
  ASSERT(args.length() == 3);
  KeyedStoreIC ic(isolate);
  Code::ExtraICState extra_ic_state = ic.target()->extra_ic_state();
  Handle<Object> object = args.at<Object>(0);
  Handle<Object> key = args.at<Object>(1);
  Handle<Object> value = args.at<Object>(2);
  StrictModeFlag strict_mode = Code::GetStrictMode(extra_ic_state);
  return Runtime::SetObjectProperty(isolate,
                                    object,
                                    key,
                                    value,
                                    NONE,
                                    strict_mode);
}


RUNTIME_FUNCTION(MaybeObject*, KeyedStoreIC_MissForceGeneric) {
  HandleScope scope(isolate);
  ASSERT(args.length() == 3);
  KeyedStoreIC ic(isolate);
  IC::State state = IC::StateFrom(ic.target(), args[0], args[1]);
  Code::ExtraICState extra_ic_state = ic.target()->extra_ic_state();
  return ic.Store(state,
                  Code::GetStrictMode(extra_ic_state),
                  args.at<Object>(0),
                  args.at<Object>(1),
                  args.at<Object>(2),
                  true);
}


void UnaryOpIC::patch(Code* code) {
  set_target(code);
}


const char* UnaryOpIC::GetName(TypeInfo type_info) {
  switch (type_info) {
    case UNINITIALIZED: return "Uninitialized";
    case SMI: return "Smi";
    case HEAP_NUMBER: return "HeapNumbers";
    case GENERIC: return "Generic";
    default: return "Invalid";
  }
}


UnaryOpIC::State UnaryOpIC::ToState(TypeInfo type_info) {
  switch (type_info) {
    case UNINITIALIZED:
      return ::v8::internal::UNINITIALIZED;
    case SMI:
    case HEAP_NUMBER:
      return MONOMORPHIC;
    case GENERIC:
      return MEGAMORPHIC;
  }
  UNREACHABLE();
  return ::v8::internal::UNINITIALIZED;
}

UnaryOpIC::TypeInfo UnaryOpIC::GetTypeInfo(Handle<Object> operand) {
  ::v8::internal::TypeInfo operand_type =
      ::v8::internal::TypeInfo::TypeFromValue(operand);
  if (operand_type.IsSmi()) {
    return SMI;
  } else if (operand_type.IsNumber()) {
    return HEAP_NUMBER;
  } else {
    return GENERIC;
  }
}


UnaryOpIC::TypeInfo UnaryOpIC::ComputeNewType(
    UnaryOpIC::TypeInfo current_type,
    UnaryOpIC::TypeInfo previous_type) {
  switch (previous_type) {
    case UnaryOpIC::UNINITIALIZED:
      return current_type;
    case UnaryOpIC::SMI:
      return (current_type == UnaryOpIC::GENERIC)
          ? UnaryOpIC::GENERIC
          : UnaryOpIC::HEAP_NUMBER;
    case UnaryOpIC::HEAP_NUMBER:
      return UnaryOpIC::GENERIC;
    case UnaryOpIC::GENERIC:
      // We should never do patching if we are in GENERIC state.
      UNREACHABLE();
      return UnaryOpIC::GENERIC;
  }
  UNREACHABLE();
  return UnaryOpIC::GENERIC;
}


void BinaryOpIC::patch(Code* code) {
  set_target(code);
}


const char* BinaryOpIC::GetName(TypeInfo type_info) {
  switch (type_info) {
    case UNINITIALIZED: return "Uninitialized";
    case SMI: return "SMI";
    case INT32: return "Int32s";
    case HEAP_NUMBER: return "HeapNumbers";
    case ODDBALL: return "Oddball";
    case BOTH_STRING: return "BothStrings";
    case STRING: return "Strings";
    case GENERIC: return "Generic";
    default: return "Invalid";
  }
}


BinaryOpIC::State BinaryOpIC::ToState(TypeInfo type_info) {
  switch (type_info) {
    case UNINITIALIZED:
      return ::v8::internal::UNINITIALIZED;
    case SMI:
    case INT32:
    case HEAP_NUMBER:
    case ODDBALL:
    case BOTH_STRING:
    case STRING:
      return MONOMORPHIC;
    case GENERIC:
      return MEGAMORPHIC;
  }
  UNREACHABLE();
  return ::v8::internal::UNINITIALIZED;
}


BinaryOpIC::TypeInfo BinaryOpIC::JoinTypes(BinaryOpIC::TypeInfo x,
                                           BinaryOpIC::TypeInfo y) {
  if (x == UNINITIALIZED) return y;
  if (y == UNINITIALIZED) return x;
  if (x == y) return x;
  if (x == BOTH_STRING && y == STRING) return STRING;
  if (x == STRING && y == BOTH_STRING) return STRING;
  if (x == STRING || x == BOTH_STRING || y == STRING || y == BOTH_STRING) {
    return GENERIC;
  }
  if (x > y) return x;
  return y;
}


BinaryOpIC::TypeInfo BinaryOpIC::GetTypeInfo(Handle<Object> left,
                                             Handle<Object> right) {
  ::v8::internal::TypeInfo left_type =
      ::v8::internal::TypeInfo::TypeFromValue(left);
  ::v8::internal::TypeInfo right_type =
      ::v8::internal::TypeInfo::TypeFromValue(right);

  if (left_type.IsSmi() && right_type.IsSmi()) {
    return SMI;
  }

  if (left_type.IsInteger32() && right_type.IsInteger32()) {
    // Platforms with 32-bit Smis have no distinct INT32 type.
    if (kSmiValueSize == 32) return SMI;
    return INT32;
  }

  if (left_type.IsNumber() && right_type.IsNumber()) {
    return HEAP_NUMBER;
  }

  // Patching for fast string ADD makes sense even if only one of the
  // arguments is a string.
  if (left_type.IsString())  {
    return right_type.IsString() ? BOTH_STRING : STRING;
  } else if (right_type.IsString()) {
    return STRING;
  }

  // Check for oddball objects.
  if (left->IsUndefined() && right->IsNumber()) return ODDBALL;
  if (left->IsNumber() && right->IsUndefined()) return ODDBALL;

  return GENERIC;
}


RUNTIME_FUNCTION(MaybeObject*, UnaryOp_Patch) {
  ASSERT(args.length() == 4);

  HandleScope scope(isolate);
  Handle<Object> operand = args.at<Object>(0);
  Token::Value op = static_cast<Token::Value>(args.smi_at(1));
  UnaryOverwriteMode mode = static_cast<UnaryOverwriteMode>(args.smi_at(2));
  UnaryOpIC::TypeInfo previous_type =
      static_cast<UnaryOpIC::TypeInfo>(args.smi_at(3));

  UnaryOpIC::TypeInfo type = UnaryOpIC::GetTypeInfo(operand);
  type = UnaryOpIC::ComputeNewType(type, previous_type);

  UnaryOpStub stub(op, mode, type);
  Handle<Code> code = stub.GetCode();
  if (!code.is_null()) {
    if (FLAG_trace_ic) {
      PrintF("[UnaryOpIC (%s->%s)#%s]\n",
             UnaryOpIC::GetName(previous_type),
             UnaryOpIC::GetName(type),
             Token::Name(op));
    }
    UnaryOpIC ic(isolate);
    ic.patch(*code);
  }

  Handle<JSBuiltinsObject> builtins = Handle<JSBuiltinsObject>(
      isolate->thread_local_top()->context_->builtins(), isolate);
  Object* builtin = NULL;  // Initialization calms down the compiler.
  switch (op) {
    case Token::SUB:
      builtin = builtins->javascript_builtin(Builtins::UNARY_MINUS);
      break;
    case Token::BIT_NOT:
      builtin = builtins->javascript_builtin(Builtins::BIT_NOT);
      break;
    default:
      UNREACHABLE();
  }

  Handle<JSFunction> builtin_function(JSFunction::cast(builtin), isolate);

  bool caught_exception;
  Handle<Object> result = Execution::Call(builtin_function, operand, 0, NULL,
                                          &caught_exception);
  if (caught_exception) {
    return Failure::Exception();
  }
  return *result;
}

RUNTIME_FUNCTION(MaybeObject*, BinaryOp_Patch) {
  ASSERT(args.length() == 5);

  HandleScope scope(isolate);
  Handle<Object> left = args.at<Object>(0);
  Handle<Object> right = args.at<Object>(1);
  int key = args.smi_at(2);
  Token::Value op = static_cast<Token::Value>(args.smi_at(3));
  BinaryOpIC::TypeInfo previous_type =
      static_cast<BinaryOpIC::TypeInfo>(args.smi_at(4));

  BinaryOpIC::TypeInfo type = BinaryOpIC::GetTypeInfo(left, right);
  type = BinaryOpIC::JoinTypes(type, previous_type);
  BinaryOpIC::TypeInfo result_type = BinaryOpIC::UNINITIALIZED;
  if ((type == BinaryOpIC::STRING || type == BinaryOpIC::BOTH_STRING) &&
      op != Token::ADD) {
    type = BinaryOpIC::GENERIC;
  }
  if (type == BinaryOpIC::SMI && previous_type == BinaryOpIC::SMI) {
    if (op == Token::DIV ||
        op == Token::MUL ||
        op == Token::SHR ||
        kSmiValueSize == 32) {
      // Arithmetic on two Smi inputs has yielded a heap number.
      // That is the only way to get here from the Smi stub.
      // With 32-bit Smis, all overflows give heap numbers, but with
      // 31-bit Smis, most operations overflow to int32 results.
      result_type = BinaryOpIC::HEAP_NUMBER;
    } else {
      // Other operations on SMIs that overflow yield int32s.
      result_type = BinaryOpIC::INT32;
    }
  }
  if (type == BinaryOpIC::INT32 && previous_type == BinaryOpIC::INT32) {
    // We must be here because an operation on two INT32 types overflowed.
    result_type = BinaryOpIC::HEAP_NUMBER;
  }

  BinaryOpStub stub(key, type, result_type);
  Handle<Code> code = stub.GetCode();
  if (!code.is_null()) {
    if (FLAG_trace_ic) {
      PrintF("[BinaryOpIC (%s->(%s->%s))#%s]\n",
             BinaryOpIC::GetName(previous_type),
             BinaryOpIC::GetName(type),
             BinaryOpIC::GetName(result_type),
             Token::Name(op));
    }
    BinaryOpIC ic(isolate);
    ic.patch(*code);

    // Activate inlined smi code.
    if (previous_type == BinaryOpIC::UNINITIALIZED) {
      PatchInlinedSmiCode(ic.address(), ENABLE_INLINED_SMI_CHECK);
    }
  }

  Handle<JSBuiltinsObject> builtins = Handle<JSBuiltinsObject>(
      isolate->thread_local_top()->context_->builtins(), isolate);
  Object* builtin = NULL;  // Initialization calms down the compiler.
  switch (op) {
    case Token::ADD:
      builtin = builtins->javascript_builtin(Builtins::ADD);
      break;
    case Token::SUB:
      builtin = builtins->javascript_builtin(Builtins::SUB);
      break;
    case Token::MUL:
      builtin = builtins->javascript_builtin(Builtins::MUL);
      break;
    case Token::DIV:
      builtin = builtins->javascript_builtin(Builtins::DIV);
      break;
    case Token::MOD:
      builtin = builtins->javascript_builtin(Builtins::MOD);
      break;
    case Token::BIT_AND:
      builtin = builtins->javascript_builtin(Builtins::BIT_AND);
      break;
    case Token::BIT_OR:
      builtin = builtins->javascript_builtin(Builtins::BIT_OR);
      break;
    case Token::BIT_XOR:
      builtin = builtins->javascript_builtin(Builtins::BIT_XOR);
      break;
    case Token::SHR:
      builtin = builtins->javascript_builtin(Builtins::SHR);
      break;
    case Token::SAR:
      builtin = builtins->javascript_builtin(Builtins::SAR);
      break;
    case Token::SHL:
      builtin = builtins->javascript_builtin(Builtins::SHL);
      break;
    default:
      UNREACHABLE();
  }

  Handle<JSFunction> builtin_function(JSFunction::cast(builtin), isolate);

  bool caught_exception;
  Handle<Object> builtin_args[] = { right };
  Handle<Object> result = Execution::Call(builtin_function,
                                          left,
                                          ARRAY_SIZE(builtin_args),
                                          builtin_args,
                                          &caught_exception);
  if (caught_exception) {
    return Failure::Exception();
  }
  return *result;
}


Code* CompareIC::GetRawUninitialized(Token::Value op) {
  ICCompareStub stub(op, UNINITIALIZED);
  Code* code = NULL;
  CHECK(stub.FindCodeInCache(&code));
  return code;
}


Handle<Code> CompareIC::GetUninitialized(Token::Value op) {
  ICCompareStub stub(op, UNINITIALIZED);
  return stub.GetCode();
}


CompareIC::State CompareIC::ComputeState(Code* target) {
  int key = target->major_key();
  if (key == CodeStub::Compare) return GENERIC;
  ASSERT(key == CodeStub::CompareIC);
  return static_cast<State>(target->compare_state());
}


Token::Value CompareIC::ComputeOperation(Code* target) {
  ASSERT(target->major_key() == CodeStub::CompareIC);
  return static_cast<Token::Value>(target->compare_operation());
}


const char* CompareIC::GetStateName(State state) {
  switch (state) {
    case UNINITIALIZED: return "UNINITIALIZED";
    case SMIS: return "SMIS";
    case HEAP_NUMBERS: return "HEAP_NUMBERS";
    case OBJECTS: return "OBJECTS";
    case KNOWN_OBJECTS: return "OBJECTS";
    case SYMBOLS: return "SYMBOLS";
    case STRINGS: return "STRINGS";
    case GENERIC: return "GENERIC";
    default:
      UNREACHABLE();
      return NULL;
  }
}


CompareIC::State CompareIC::TargetState(State state,
                                        bool has_inlined_smi_code,
                                        Handle<Object> x,
                                        Handle<Object> y) {
  switch (state) {
    case UNINITIALIZED:
      if (x->IsSmi() && y->IsSmi()) return SMIS;
      if (x->IsNumber() && y->IsNumber()) return HEAP_NUMBERS;
      if (Token::IsOrderedRelationalCompareOp(op_)) {
        // Ordered comparisons treat undefined as NaN, so the
        // HEAP_NUMBER stub will do the right thing.
        if ((x->IsNumber() && y->IsUndefined()) ||
            (y->IsNumber() && x->IsUndefined())) {
          return HEAP_NUMBERS;
        }
      }
      if (x->IsSymbol() && y->IsSymbol()) {
        // We compare symbols as strings if we need to determine
        // the order in a non-equality compare.
        return Token::IsEqualityOp(op_) ? SYMBOLS : STRINGS;
      }
      if (x->IsString() && y->IsString()) return STRINGS;
      if (!Token::IsEqualityOp(op_)) return GENERIC;
      if (x->IsJSObject() && y->IsJSObject()) {
        if (Handle<JSObject>::cast(x)->map() ==
            Handle<JSObject>::cast(y)->map() &&
            Token::IsEqualityOp(op_)) {
          return KNOWN_OBJECTS;
        } else {
          return OBJECTS;
        }
      }
      return GENERIC;
    case SMIS:
      return has_inlined_smi_code && x->IsNumber() && y->IsNumber()
          ? HEAP_NUMBERS
          : GENERIC;
    case SYMBOLS:
      ASSERT(Token::IsEqualityOp(op_));
      return x->IsString() && y->IsString() ? STRINGS : GENERIC;
    case HEAP_NUMBERS:
    case STRINGS:
    case OBJECTS:
    case KNOWN_OBJECTS:
    case GENERIC:
      return GENERIC;
  }
  UNREACHABLE();
  return GENERIC;
}


// Used from ic_<arch>.cc.
RUNTIME_FUNCTION(Code*, CompareIC_Miss) {
  NoHandleAllocation na;
  ASSERT(args.length() == 3);
  CompareIC ic(isolate, static_cast<Token::Value>(args.smi_at(2)));
  ic.UpdateCaches(args.at<Object>(0), args.at<Object>(1));
  return ic.target();
}


RUNTIME_FUNCTION(MaybeObject*, ToBoolean_Patch) {
  ASSERT(args.length() == 3);

  HandleScope scope(isolate);
  Handle<Object> object = args.at<Object>(0);
  Register tos = Register::from_code(args.smi_at(1));
  ToBooleanStub::Types old_types(args.smi_at(2));

  ToBooleanStub::Types new_types(old_types);
  bool to_boolean_value = new_types.Record(object);
  old_types.TraceTransition(new_types);

  ToBooleanStub stub(tos, new_types);
  Handle<Code> code = stub.GetCode();
  ToBooleanIC ic(isolate);
  ic.patch(*code);
  return Smi::FromInt(to_boolean_value ? 1 : 0);
}


void ToBooleanIC::patch(Code* code) {
  set_target(code);
}


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