[ic] Completely unroll polymorphic IC map checks

src/ic/ic.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_IC_H_
 #define V8_IC_H_
 
 #include "src/factory.h"
 #include "src/feedback-vector.h"
 #include "src/ic/ic-state.h"
 #include "src/macro-assembler.h"
 #include "src/messages.h"
 
 namespace v8 {
 namespace internal {
 
 //
 // IC is the base class for LoadIC, StoreIC, KeyedLoadIC, and KeyedStoreIC.
 //
 class IC {
  public:
   // Alias the inline cache state type to make the IC code more readable.
   typedef InlineCacheState State;
 
   // The IC code is either invoked with no extra frames on the stack
   // or with a single extra frame for supporting calls.
   enum FrameDepth { NO_EXTRA_FRAME = 0, EXTRA_CALL_FRAME = 1 };
 
+  // A polymorphic IC can handle at most 4 distinct maps before transitioning
+  // to megamorphic state.
+  static constexpr int kMaxPolymorphicMapCount = 4;
+
   // Construct the IC structure with the given number of extra
   // JavaScript frames on the stack.
   IC(FrameDepth depth, Isolate* isolate, FeedbackNexus* nexus = NULL);
   virtual ~IC() {}
 
   State state() const { return state_; }
   inline Address address() const;
 
   // Compute the current IC state based on the target stub, receiver and name.
   void UpdateState(Handle<Object> receiver, Handle<Object> name);
@@ skipping 447 matching lines @@
 
 // Helper for BinaryOpIC and CompareIC.
 enum InlinedSmiCheck { ENABLE_INLINED_SMI_CHECK, DISABLE_INLINED_SMI_CHECK };
 void PatchInlinedSmiCode(Isolate* isolate, Address address,
                          InlinedSmiCheck check);
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_IC_H_