Improved version of LookupForRead (tnx to Kasper) + some faster paths.

1) add no GC check;
2) do not use recursion;

Review URL: http://codereview.chromium.org/155141

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2462 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ic.cc

@@ -273,28 +273,39 @@ static bool HasInterceptorGetter(JSObject* object) {
 static void LookupForRead(Object* object,
                           String* name,
                           LookupResult* lookup) {
-  object->Lookup(name, lookup);
-  if (lookup->IsNotFound() || lookup->type() != INTERCEPTOR) {
-    return;
-  }
+  AssertNoAllocation no_gc;  // pointers must stay valid
+
+  // 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 of lookup is not cacheable: we won't
+    // be able to IC it anyway and regular lookup should work fine.
+    if (lookup->IsNotFound() || lookup->type() != INTERCEPTOR ||
+        !lookup->IsCacheable()) {
+      return;
+    }
 
-  JSObject* holder = lookup->holder();
-  if (HasInterceptorGetter(holder)) {
-    return;
-  }
+    JSObject* holder = lookup->holder();
+    if (HasInterceptorGetter(holder)) {
+      return;
+    }
 
-  // There is no getter, just skip it and lookup down the proto chain
-  holder->LocalLookupRealNamedProperty(name, lookup);
-  if (lookup->IsValid()) {
-    return;
-  }
+    holder->LocalLookupRealNamedProperty(name, lookup);
+    if (lookup->IsValid()) {
+      ASSERT(lookup->type() != INTERCEPTOR);
+      return;
+    }
 
-  Object* proto = holder->GetPrototype();
-  if (proto == Heap::null_value()) {
-    return;
-  }
+    Object* proto = holder->GetPrototype();
+    if (proto->IsNull()) {
+      lookup->NotFound();
+      return;
+    }
 
-  LookupForRead(proto, name, lookup);
+    object = proto;
+  }
 }