Convert diamond shaped control flow into a single conditional instruction.

runtime/vm/assembler_x64_test.cc

Index: runtime/vm/assembler_x64_test.cc
diff --git a/runtime/vm/assembler_x64_test.cc b/runtime/vm/assembler_x64_test.cc
index 2d29d9debb23edbe3be363c49f8d0bec87f913a0..bf2903d91f1551994a3fb462dce6a01d93e3e792 100644
--- a/runtime/vm/assembler_x64_test.cc
+++ b/runtime/vm/assembler_x64_test.cc
@@ -2291,6 +2291,21 @@ ASSEMBLER_TEST_RUN(ExtractSignBits, test) {
   EXPECT_EQ(1, res);
 }
 
+
+ASSEMBLER_TEST_GENERATE(TestSetCC, assembler) {
+  __ movq(RAX, Immediate(0xFFFFFFFF));
+  __ cmpq(RAX, RAX);
+  __ setcc(NOT_EQUAL, AL);
+  __ ret();
+}
+
+
+ASSEMBLER_TEST_RUN(TestSetCC, test) {
+  typedef uword (*TestSetCC)();
+  uword res = reinterpret_cast<TestSetCC>(test->entry())();
+  EXPECT_EQ(0xFFFFFF00, res);
+}
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64