Don't explicitly pass requested representations to constants; implement ConstantS

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index c295e3478dccacc8a5f83d2cecd086a0a4e4c62a..36b080ff4bdedb598cb7d5feb9d8c9559cd9915e 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -87,6 +87,7 @@ class LCodeGen;
   V(CmpT)                                       \
   V(ConstantD)                                  \
   V(ConstantI)                                  \
+  V(ConstantS)                                  \
   V(ConstantT)                                  \
   V(Context)                                    \
   V(DebugBreak)                                 \
@@ -1136,6 +1137,15 @@ class LConstantI: public LTemplateInstruction<1, 0, 0> {
 };
 
 
+class LConstantS: public LTemplateInstruction<1, 0, 0> {
+ public:
+  DECLARE_CONCRETE_INSTRUCTION(ConstantS, "constant-s")
+  DECLARE_HYDROGEN_ACCESSOR(Constant)
+
+  Smi* value() const { return Smi::FromInt(hydrogen()->Integer32Value()); }
+};
+
+
 class LConstantD: public LTemplateInstruction<1, 0, 1> {
  public:
   explicit LConstantD(LOperand* temp) {