Fix deoptmization of inlined TF InstanceOf to call ToBoolean

test/mjsunit/regress/regress-6373.js

Index: test/mjsunit/regress/regress-6373.js
diff --git a/test/mjsunit/regress/regress-6373.js b/test/mjsunit/regress/regress-6373.js
new file mode 100644
index 0000000000000000000000000000000000000000..8673e83f22ce0ea1aa7c6c0240abdaa2ef40d6b5
--- /dev/null
+++ b/test/mjsunit/regress/regress-6373.js
@@ -0,0 +1,24 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+var A = {}
+
+A[Symbol.hasInstance] = function(x) {
+  %DeoptimizeFunction(foo);
+  return 1;
+}
+
+var a = {}
+
+function foo(o) {
+  return o instanceof A;
+}
+
+foo(a);
+foo(a);
+assertTrue(foo(a) !== 1);
+%OptimizeFunctionOnNextCall(foo);
+assertTrue(foo(a) !== 1);