Try to make the contextuality check in the IC code faster

by checking if the receiver is a global object before diving
into traversing reloc info.
Review URL: http://codereview.chromium.org/491075

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3459 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ic.cc

@@ -409,7 +409,7 @@ Object* CallIC::LoadFunction(State state,
   if (!lookup.IsValid()) {
     // If the object does not have the requested property, check which
     // exception we need to throw.
-    if (is_contextual()) {
+    if (IsContextual(object)) {
       return ReferenceError("not_defined", name);
     }
     return TypeError("undefined_method", object, name);
@@ -428,7 +428,7 @@ Object* CallIC::LoadFunction(State state,
     // If the object does not have the requested property, check which
     // exception we need to throw.
     if (attr == ABSENT) {
-      if (is_contextual()) {
+      if (IsContextual(object)) {
         return ReferenceError("not_defined", name);
       }
       return TypeError("undefined_method", object, name);
@@ -628,7 +628,7 @@ Object* LoadIC::Load(State state, Handle<Object> object, Handle<String> name) {
 
   // If lookup is invalid, check if we need to throw an exception.
   if (!lookup.IsValid()) {
-    if (FLAG_strict || is_contextual()) {
+    if (FLAG_strict || IsContextual(object)) {
       return ReferenceError("not_defined", name);
     }
     LOG(SuspectReadEvent(*name, *object));
@@ -671,7 +671,7 @@ Object* LoadIC::Load(State state, Handle<Object> object, Handle<String> name) {
     if (result->IsFailure()) return result;
     // If the property is not present, check if we need to throw an
     // exception.
-    if (attr == ABSENT && is_contextual()) {
+    if (attr == ABSENT && IsContextual(object)) {
       return ReferenceError("not_defined", name);
     }
     return result;
@@ -843,7 +843,7 @@ Object* KeyedLoadIC::Load(State state,
 
     // If lookup is invalid, check if we need to throw an exception.
     if (!lookup.IsValid()) {
-      if (FLAG_strict || is_contextual()) {
+      if (FLAG_strict || IsContextual(object)) {
         return ReferenceError("not_defined", name);
       }
     }
@@ -859,7 +859,7 @@ Object* KeyedLoadIC::Load(State state,
       if (result->IsFailure()) return result;
       // If the property is not present, check if we need to throw an
       // exception.
-      if (attr == ABSENT && is_contextual()) {
+      if (attr == ABSENT && IsContextual(object)) {
         return ReferenceError("not_defined", name);
       }
       return result;

src/ic.h

@@ -104,7 +104,16 @@ class IC {
 
   // Returns if this IC is for contextual (no explicit receiver)
   // access to properties.
-  bool is_contextual() {
+  bool IsContextual(Handle<Object> receiver) {
+    if (receiver->IsGlobalObject()) {
+      return SlowIsContextual();
+    } else {
+      ASSERT(!SlowIsContextual());
+      return false;
+    }
+  }
+
+  bool SlowIsContextual() {
     return ComputeMode() == RelocInfo::CODE_TARGET_CONTEXT;
   }
 

src/stub-cache.cc

@@ -831,7 +831,7 @@ static Object* ThrowReferenceError(String* name) {
   // can't use either LoadIC or KeyedLoadIC constructors.
   IC ic(IC::NO_EXTRA_FRAME);
   ASSERT(ic.target()->is_load_stub() || ic.target()->is_keyed_load_stub());
-  if (!ic.is_contextual()) return Heap::undefined_value();
+  if (!ic.SlowIsContextual()) return Heap::undefined_value();
 
   // Throw a reference error.
   HandleScope scope;