[compiler] Drop the CompareNilIC.

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index f370ce64735e994c84591d0316967d45c1cd9cd8..4f3020ed5d411af61ed2529151c0e1a37eccad17 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -67,7 +67,6 @@ namespace internal {
   V(ArraySingleArgumentConstructor)         \
   V(BinaryOpIC)                             \
   V(BinaryOpWithAllocationSite)             \
-  V(CompareNilIC)                           \
   V(CreateAllocationSite)                   \
   V(CreateWeakCell)                         \
   V(ElementsTransitionAndStore)             \
@@ -1701,96 +1700,6 @@ class CompareICStub : public PlatformCodeStub {
 };
 
 
-class CompareNilICStub : public HydrogenCodeStub  {
- public:
-  Type* GetType(Zone* zone, Handle<Map> map = Handle<Map>());
-  Type* GetInputType(Zone* zone, Handle<Map> map);
-
-  CompareNilICStub(Isolate* isolate, NilValue nil) : HydrogenCodeStub(isolate) {
-    set_sub_minor_key(NilValueBits::encode(nil));
-  }
-
-  CompareNilICStub(Isolate* isolate, ExtraICState ic_state,
-                   InitializationState init_state = INITIALIZED)
-      : HydrogenCodeStub(isolate, init_state) {
-    set_sub_minor_key(ic_state);
-  }
-
-  static Handle<Code> GetUninitialized(Isolate* isolate,
-                                       NilValue nil) {
-    return CompareNilICStub(isolate, nil, UNINITIALIZED).GetCode();
-  }
-
-  InlineCacheState GetICState() const override {
-    State state = this->state();
-    if (state.Contains(GENERIC)) {
-      return MEGAMORPHIC;
-    } else if (state.Contains(MONOMORPHIC_MAP)) {
-      return MONOMORPHIC;
-    } else {
-      return PREMONOMORPHIC;
-    }
-  }
-
-  Code::Kind GetCodeKind() const override { return Code::COMPARE_NIL_IC; }
-
-  ExtraICState GetExtraICState() const override { return sub_minor_key(); }
-
-  void UpdateStatus(Handle<Object> object);
-
-  bool IsMonomorphic() const { return state().Contains(MONOMORPHIC_MAP); }
-
-  NilValue nil_value() const { return NilValueBits::decode(sub_minor_key()); }
-
-  void ClearState() {
-    set_sub_minor_key(TypesBits::update(sub_minor_key(), 0));
-  }
-
-  void PrintState(std::ostream& os) const override;     // NOLINT
-  void PrintBaseName(std::ostream& os) const override;  // NOLINT
-
- private:
-  CompareNilICStub(Isolate* isolate, NilValue nil,
-                   InitializationState init_state)
-      : HydrogenCodeStub(isolate, init_state) {
-    set_sub_minor_key(NilValueBits::encode(nil));
-  }
-
-  enum CompareNilType {
-    UNDEFINED,
-    NULL_TYPE,
-    MONOMORPHIC_MAP,
-    GENERIC,
-    NUMBER_OF_TYPES
-  };
-
-  // At most 6 different types can be distinguished, because the Code object
-  // only has room for a single byte to hold a set and there are two more
-  // boolean flags we need to store. :-P
-  STATIC_ASSERT(NUMBER_OF_TYPES <= 6);
-
-  class State : public EnumSet<CompareNilType, byte> {
-   public:
-    State() : EnumSet<CompareNilType, byte>(0) { }
-    explicit State(byte bits) : EnumSet<CompareNilType, byte>(bits) { }
-  };
-  friend std::ostream& operator<<(std::ostream& os, const State& s);
-
-  State state() const { return State(TypesBits::decode(sub_minor_key())); }
-
-  class NilValueBits : public BitField<NilValue, 0, 1> {};
-  class TypesBits : public BitField<byte, 1, NUMBER_OF_TYPES> {};
-
-  friend class CompareNilIC;
-
-  DEFINE_CALL_INTERFACE_DESCRIPTOR(CompareNil);
-  DEFINE_HYDROGEN_CODE_STUB(CompareNilIC, HydrogenCodeStub);
-};
-
-
-std::ostream& operator<<(std::ostream& os, const CompareNilICStub::State& s);
-
-
 class CEntryStub : public PlatformCodeStub {
  public:
   CEntryStub(Isolate* isolate, int result_size,