Simplify instanceof optimization; don't duplicate lookup

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 038834ca442daf22093bdb21e556920527364016..029cd808e22c1a6395e4d75a5d9084e97761c0c0 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -10828,41 +10828,19 @@ void HOptimizedGraphBuilder::VisitCompareOperation(CompareOperation* expr) {
   }
 
   if (op == Token::INSTANCEOF) {
-    // Check to see if the rhs of the instanceof is a global function not
-    // residing in new space. If it is we assume that the function will stay the
-    // same.
-    Handle<JSFunction> target = Handle<JSFunction>::null();
-    VariableProxy* proxy = expr->right()->AsVariableProxy();
-    bool global_function = (proxy != NULL) && proxy->var()->IsUnallocated();
-    if (global_function && current_info()->has_global_object()) {
-      Handle<String> name = proxy->name();
-      Handle<GlobalObject> global(current_info()->global_object());
-      LookupIterator it(global, name, LookupIterator::OWN_SKIP_INTERCEPTOR);
-      Handle<Object> value = JSObject::GetDataProperty(&it);
-      if (it.IsFound() && value->IsJSFunction()) {
-        Handle<JSFunction> candidate = Handle<JSFunction>::cast(value);
-        // If the function is in new space we assume it's more likely to
-        // change and thus prefer the general IC code.
-        if (!isolate()->heap()->InNewSpace(*candidate)) {
-          target = candidate;
-        }
-      }
-    }
-
-    // If the target is not null we have found a known global function that is
-    // assumed to stay the same for this instanceof.
-    if (target.is_null()) {
-      HInstanceOf* result = New<HInstanceOf>(left, right);
-      return ast_context()->ReturnInstruction(result, expr->id());
-    } else {
-      Add<HCheckValue>(right, target);
+    // Check to see if the rhs of the instanceof is a known function.
+    if (right->IsConstant() &&
+        HConstant::cast(right)->handle(isolate())->IsJSFunction()) {
+      Handle<Object> function = HConstant::cast(right)->handle(isolate());
+      Handle<JSFunction> target = Handle<JSFunction>::cast(function);
       HInstanceOfKnownGlobal* result =
-        New<HInstanceOfKnownGlobal>(left, target);
+          New<HInstanceOfKnownGlobal>(left, target);
       return ast_context()->ReturnInstruction(result, expr->id());
     }
 
-    // Code below assumes that we don't fall through.
-    UNREACHABLE();
+    HInstanceOf* result = New<HInstanceOf>(left, right);
+    return ast_context()->ReturnInstruction(result, expr->id());
+
   } else if (op == Token::IN) {
     HValue* function = AddLoadJSBuiltin(Builtins::IN);
     Add<HPushArguments>(left, right);