Remove the unused HElementsKind instruction.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index a06c3bb92e18bb9b18862e82e3c35f1479e8580e..333badda9df45a763f1b231cac4cfb7df3ce4aa3 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -1574,20 +1574,6 @@ void LCodeGen::DoMapEnumLength(LMapEnumLength* instr) {
 }
 
 
-void LCodeGen::DoElementsKind(LElementsKind* instr) {
-  Register result = ToRegister(instr->result());
-  Register input = ToRegister(instr->value());
-
-  // Load map into |result|.
-  __ movp(result, FieldOperand(input, HeapObject::kMapOffset));
-  // Load the map's "bit field 2" into |result|. We only need the first byte.
-  __ movzxbq(result, FieldOperand(result, Map::kBitField2Offset));
-  // Retrieve elements_kind from bit field 2.
-  __ and_(result, Immediate(Map::kElementsKindMask));
-  __ shr(result, Immediate(Map::kElementsKindShift));
-}
-
-
 void LCodeGen::DoValueOf(LValueOf* instr) {
   Register input = ToRegister(instr->value());
   Register result = ToRegister(instr->result());