VM: Improve receiver class check in polymorphic inlining.

runtime/vm/assembler_x64_test.cc

Index: runtime/vm/assembler_x64_test.cc
===================================================================
--- runtime/vm/assembler_x64_test.cc	(revision 38058)
+++ runtime/vm/assembler_x64_test.cc	(working copy)
@@ -2949,6 +2949,26 @@
   EXPECT_EQ(-1, res);  // Less.
 }
 
+
+ASSEMBLER_TEST_GENERATE(BitTest, assembler) {
+  __ movq(RAX, Immediate(4));
+  __ movq(R12, Immediate(2));
+  __ btq(RAX, R12);
+  Label ok;
+  __ j(CARRY, &ok);
+  __ int3();
+  __ Bind(&ok);
+  __ movq(RAX, Immediate(1));
+  __ ret();
+}
+
+
+ASSEMBLER_TEST_RUN(BitTest, test) {
+  typedef int (*BitTest)();
+  EXPECT_EQ(1, reinterpret_cast<BitTest>(test->entry())());
+}
+
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64