Remove custom weak handling of monomorphic IC.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index dacbd837fce1cfca04e6065b1518f6d34e5804fd..750ceb3612b5fcd9a130f4b788630a2616462395 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2690,11 +2690,7 @@ class WeakFixedArray : public FixedArray {
 //
 class ConstantPoolArray: public HeapObject {
  public:
-  enum WeakObjectState {
-    NO_WEAK_OBJECTS,
-    WEAK_OBJECTS_IN_OPTIMIZED_CODE,
-    WEAK_OBJECTS_IN_IC
-  };
+  enum WeakObjectState { NO_WEAK_OBJECTS, WEAK_OBJECTS_IN_OPTIMIZED_CODE };
 
   enum Type {
     INT64 = 0,
@@ -5138,12 +5134,7 @@ class Code: public HeapObject {
   inline bool is_to_boolean_ic_stub() { return kind() == TO_BOOLEAN_IC; }
   inline bool is_keyed_stub();
   inline bool is_optimized_code() { return kind() == OPTIMIZED_FUNCTION; }
-  inline bool is_weak_stub();
-  inline void mark_as_weak_stub();
-  inline bool is_invalidated_weak_stub();
-  inline void mark_as_invalidated_weak_stub();
-
-  inline bool CanBeWeakStub() {
+  inline bool embeds_maps_weakly() {
     Kind k = kind();
     return (k == LOAD_IC || k == STORE_IC || k == KEYED_LOAD_IC ||
             k == KEYED_STORE_IC || k == COMPARE_NIL_IC) &&
@@ -5424,18 +5415,14 @@ class Code: public HeapObject {
   void VerifyEmbeddedObjectsInFullCode();
 #endif  // DEBUG
 
-  inline bool CanContainWeakObjects() {
-    return is_optimized_code() || is_weak_stub();
-  }
+  inline bool CanContainWeakObjects() { return is_optimized_code(); }
 
   inline bool IsWeakObject(Object* object) {
     return (is_optimized_code() && !is_turbofanned() &&
-            IsWeakObjectInOptimizedCode(object)) ||
-           (is_weak_stub() && IsWeakObjectInIC(object));
+            IsWeakObjectInOptimizedCode(object));
   }
 
   static inline bool IsWeakObjectInOptimizedCode(Object* object);
-  static inline bool IsWeakObjectInIC(Object* object);
 
   // Max loop nesting marker used to postpose OSR. We don't take loop
   // nesting that is deeper than 5 levels into account.
@@ -5497,9 +5484,7 @@ class Code: public HeapObject {
   static const int kHasFunctionCacheBit =
       kStackSlotsFirstBit + kStackSlotsBitCount;
   static const int kMarkedForDeoptimizationBit = kHasFunctionCacheBit + 1;
-  static const int kWeakStubBit = kMarkedForDeoptimizationBit + 1;
-  static const int kInvalidatedWeakStubBit = kWeakStubBit + 1;
-  static const int kIsTurbofannedBit = kInvalidatedWeakStubBit + 1;
+  static const int kIsTurbofannedBit = kMarkedForDeoptimizationBit + 1;
 
   STATIC_ASSERT(kStackSlotsFirstBit + kStackSlotsBitCount <= 32);
   STATIC_ASSERT(kIsTurbofannedBit + 1 <= 32);
@@ -5510,9 +5495,6 @@ class Code: public HeapObject {
   };  // NOLINT
   class MarkedForDeoptimizationField
       : public BitField<bool, kMarkedForDeoptimizationBit, 1> {};   // NOLINT
-  class WeakStubField : public BitField<bool, kWeakStubBit, 1> {};  // NOLINT
-  class InvalidatedWeakStubField
-      : public BitField<bool, kInvalidatedWeakStubBit, 1> {};  // NOLINT
   class IsTurbofannedField : public BitField<bool, kIsTurbofannedBit, 1> {
   };  // NOLINT
 
@@ -5594,11 +5576,6 @@ class CompilationInfo;
 class DependentCode: public FixedArray {
  public:
   enum DependencyGroup {
-    // Group of IC stubs that weakly embed this map and depend on being
-    // invalidated when the map is garbage collected. Dependent IC stubs form
-    // a linked list. This group stores only the head of the list. This means
-    // that the number_of_entries(kWeakICGroup) is 0 or 1.
-    kWeakICGroup,
     // Group of code that weakly embed this map and depend on being
     // deoptimized when the map is garbage collected.
     kWeakCodeGroup,
@@ -5659,7 +5636,6 @@ class DependentCode: public FixedArray {
 
   bool MarkCodeForDeoptimization(Isolate* isolate,
                                  DependentCode::DependencyGroup group);
-  void AddToDependentICList(Handle<Code> stub);
 
   // The following low-level accessors should only be used by this class
   // and the mark compact collector.
@@ -6278,8 +6254,6 @@ class Map: public HeapObject {
   static void AddDependentCode(Handle<Map> map,
                                DependentCode::DependencyGroup group,
                                Handle<Code> code);
-  static void AddDependentIC(Handle<Map> map,
-                             Handle<Code> stub);
 
   bool IsMapInArrayPrototypeChain();