Add an IC for CompareNil operations

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 3ca89f08eab202ebf9e14531795a7fed54cd3f60..5203017e98c209fd19a714d504c296f201ada460 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4337,6 +4337,7 @@ class Code: public HeapObject {
   V(UNARY_OP_IC)          \
   V(BINARY_OP_IC)         \
   V(COMPARE_IC)           \
+  V(COMPARE_NIL_IC)       \
   V(TO_BOOLEAN_IC)
 
   enum Kind {
@@ -4463,6 +4464,7 @@ class Code: public HeapObject {
   inline bool is_unary_op_stub() { return kind() == UNARY_OP_IC; }
   inline bool is_binary_op_stub() { return kind() == BINARY_OP_IC; }
   inline bool is_compare_ic_stub() { return kind() == COMPARE_IC; }
+  inline bool is_compare_nil_ic_stub() { return kind() == COMPARE_NIL_IC; }
   inline bool is_to_boolean_ic_stub() { return kind() == TO_BOOLEAN_IC; }
 
   // [major_key]: For kind STUB or BINARY_OP_IC, the major key.
@@ -4541,6 +4543,9 @@ class Code: public HeapObject {
   inline byte to_boolean_state();
   inline void set_to_boolean_state(byte value);
 
+  // [compare_nil]: For kind COMPARE_NIL_IC tells what state the stub is in.
+  inline byte compare_nil_state();
+
   // [has_function_cache]: For kind STUB tells whether there is a function
   // cache is passed to the stub.
   inline bool has_function_cache();
@@ -4560,6 +4565,7 @@ class Code: public HeapObject {
   // Find the first map in an IC stub.
   Map* FindFirstMap();
   void FindAllMaps(MapHandleList* maps);
+  void ReplaceFirstMap(Map* replace);
 
   // Find the first code in an IC stub.
   Code* FindFirstCode();