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

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 9d5d2a31c5ceee61652cd923ca83e8a13d1388ca..25bc632f9d8f150a456ed60e9c3d113ee0d7f1d8 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -648,9 +648,16 @@ class MacroAssembler: public Assembler {
   void SmiOrConstant(Register dst, Register src1, Smi* constant);
   void SmiXorConstant(Register dst, Register src1, Smi* constant);
 
+#if !V8_USE_31_BITS_SMI_VALUE
   void SmiShiftLeftConstant(Register dst,
                             Register src,
                             int shift_value);
+#else
+  void SmiShiftLeftConstant(Register dst,
+                            Register src,
+                            int shift_value,
+                            Label* on_not_smi_result);
+#endif
   void SmiShiftLogicalRightConstant(Register dst,
                                   Register src,
                                   int shift_value,
@@ -662,9 +669,16 @@ class MacroAssembler: public Assembler {
 
   // Shifts a smi value to the left, and returns the result if that is a smi.
   // Uses and clobbers rcx, so dst may not be rcx.
+#if !V8_USE_31_BITS_SMI_VALUE
   void SmiShiftLeft(Register dst,
                     Register src1,
                     Register src2);
+#else
+  void SmiShiftLeft(Register dst,
+                    Register src1,
+                    Register src2,
+                    Label* on_not_smi_result);
+#endif
   // Shifts a smi value to the right, shifting in zero bits at the top, and
   // returns the unsigned intepretation of the result if that is a smi.
   // Uses and clobbers rcx, so dst may not be rcx.