Optionally use 31-bits SMI value for 64-bit system

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index 542018fddd084c20fb9fc1f024a4d8a92e41cccd..15099da8ebcbfd477c24ecdf3234db70ee4ce613 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -3056,6 +3056,10 @@ static void GenerateSmiKeyCheck(MacroAssembler* masm,
   __ ucomisd(xmm_scratch1, xmm_scratch0);
   __ j(not_equal, fail);
   __ j(parity_even, fail);  // NaN.
+#if V8_USE_31_BITS_SMI_VALUE
+  __ cmpl(scratch, Immediate(0xc0000000));
+  __ j(sign, fail);
+#endif
   __ Integer32ToSmi(key, scratch);
   __ bind(&key_ok);
 }