Correctify instanceof and make it optimizable.

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index de64541496f41ac4ce59cc7836943588804a0acb..5da9c90682a75b807ee597775f91a53b664350cb 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -435,38 +435,6 @@ function IN(x) {
 }
 
 
-// ECMA-262, section 11.8.6, page 54. To make the implementation more
-// efficient, the return value should be zero if the 'this' is an
-// instance of F, and non-zero if not. This makes it possible to avoid
-// an expensive ToBoolean conversion in the generated code.
-function INSTANCE_OF(F) {
-  var V = this;
-  if (!IS_SPEC_FUNCTION(F)) {
-    throw %MakeTypeError(kInstanceofFunctionExpected, F);
-  }
-
-  // If V is not an object, return false.
-  if (!IS_SPEC_OBJECT(V)) {
-    return 1;
-  }
-
-  // Check if function is bound, if so, get [[BoundFunction]] from it
-  // and use that instead of F.
-  var bindings = %BoundFunctionGetBindings(F);
-  if (bindings) {
-    F = bindings[kBoundFunctionIndex];  // Always a non-bound function.
-  }
-  // Get the prototype of F; if it is not an object, throw an error.
-  var O = F.prototype;
-  if (!IS_SPEC_OBJECT(O)) {
-    throw %MakeTypeError(kInstanceofNonobjectProto, O);
-  }
-
-  // Return whether or not O is in the prototype chain of V.
-  return %IsInPrototypeChain(O, V) ? 0 : 1;
-}
-
-
 function CALL_NON_FUNCTION() {
   var delegate = %GetFunctionDelegate(this);
   if (!IS_FUNCTION(delegate)) {
@@ -899,7 +867,6 @@ $toString = ToString;
   SHR,
   SHR_STRONG,
   IN,
-  INSTANCE_OF,
   CALL_NON_FUNCTION,
   CALL_NON_FUNCTION_AS_CONSTRUCTOR,
   CALL_FUNCTION_PROXY,