Cleanup of class id loading sequences.

runtime/vm/assembler_x64_test.cc

Index: runtime/vm/assembler_x64_test.cc
===================================================================
--- runtime/vm/assembler_x64_test.cc	(revision 38317)
+++ runtime/vm/assembler_x64_test.cc	(working copy)
@@ -278,6 +278,25 @@
 }
 
 
+ASSEMBLER_TEST_GENERATE(Cmpb, assembler) {
+  Label done;
+  __ movq(RAX, Immediate(1));
+  __ pushq(Immediate(0xffffff11));
+  __ cmpb(Address(RSP, 0), Immediate(0x11));
+  __ j(EQUAL, &done, Assembler::kNearJump);
+  __ movq(RAX, Immediate(0));
+  __ Bind(&done);
+  __ popq(RCX);
+  __ ret();
+}
+
+
+ASSEMBLER_TEST_RUN(Cmpb, test) {
+  typedef int (*CmpbCode)();
+  EXPECT_EQ(1, reinterpret_cast<CmpbCode>(test->entry())());
+}
+
+
 ASSEMBLER_TEST_GENERATE(Increment, assembler) {
   __ movq(RAX, Immediate(0));
   __ pushq(RAX);