Correctify instanceof and make it optimizable.

src/full-codegen/x64/full-codegen-x64.cc

Index: src/full-codegen/x64/full-codegen-x64.cc
diff --git a/src/full-codegen/x64/full-codegen-x64.cc b/src/full-codegen/x64/full-codegen-x64.cc
index f0796f7cb782f60561beb16a66df22b7ae98cf88..715678cc750c30263e1253cf5ade88d6727f6f6f 100644
--- a/src/full-codegen/x64/full-codegen-x64.cc
+++ b/src/full-codegen/x64/full-codegen-x64.cc
@@ -5041,13 +5041,13 @@ void FullCodeGenerator::VisitCompareOperation(CompareOperation* expr) {
       break;
 
     case Token::INSTANCEOF: {
-      VisitForStackValue(expr->right());
-      InstanceofStub stub(isolate(), InstanceofStub::kNoFlags);
+      VisitForAccumulatorValue(expr->right());
+      __ Pop(rdx);
+      InstanceOfStub stub(isolate());
       __ CallStub(&stub);
-      PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
-      __ testp(rax, rax);
-       // The stub returns 0 for true.
-      Split(zero, if_true, if_false, fall_through);
+      PrepareForBailoutBeforeSplit(expr, false, NULL, NULL);
+      __ CompareRoot(rax, Heap::kTrueValueRootIndex);
+      Split(equal, if_true, if_false, fall_through);
       break;
     }