Using unsigned shifts and masks when dealing with 64-bit addresses.

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index 6a2f3289f8941ed1993f922207a3ecb96546232f..fc2c5e548232328b8106ac98b96e47bca94a7a53 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -874,6 +874,10 @@ THREADED_TEST(ExternalWrap) {
   TestExternalPointerWrapping();
 
 #if defined(V8_HOST_ARCH_X64)
+  // Check a value with a leading 1 bit in x64 Smi encoding.
+  expected_ptr = reinterpret_cast<void*>(0x400000000);
+  TestExternalPointerWrapping();
+
   expected_ptr = reinterpret_cast<void*>(0xdeadbeefdeadbeef);
   TestExternalPointerWrapping();