Use a dictionary-mode code cache on the map rather than a dual system.

src/x64/code-stubs-x64.cc

 // Copyright 2013 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-stubs.h"
 #include "src/api-arguments.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 3731 matching lines @@
   // Is it a fixed array?
   __ bind(&try_array);
   __ CompareRoot(FieldOperand(feedback, 0), Heap::kFixedArrayMapRootIndex);
   __ j(not_equal, &not_array);
   HandleArrayCases(masm, feedback, receiver_map, integer_slot, r11, r15, true,
                    &miss);
 
   __ bind(&not_array);
   __ CompareRoot(feedback, Heap::kmegamorphic_symbolRootIndex);
   __ j(not_equal, &miss);
-  Code::Flags code_flags = Code::RemoveTypeAndHolderFromFlags(
-      Code::ComputeHandlerFlags(Code::LOAD_IC));
+  Code::Flags code_flags =
+      Code::RemoveHolderFromFlags(Code::ComputeHandlerFlags(Code::LOAD_IC));
   masm->isolate()->stub_cache()->GenerateProbe(
       masm, Code::LOAD_IC, code_flags, receiver, name, feedback, no_reg);
 
   __ bind(&miss);
   LoadIC::GenerateMiss(masm);
 
   __ bind(&load_smi_map);
   __ LoadRoot(receiver_map, Heap::kHeapNumberMapRootIndex);
   __ jmp(&compare_map);
 }
@@ skipping 120 matching lines @@
   __ bind(&try_array);
   __ CompareRoot(FieldOperand(feedback, 0), Heap::kFixedArrayMapRootIndex);
   __ j(not_equal, &not_array);
   HandleArrayCases(masm, feedback, receiver_map, integer_slot, r14, r15, true,
                    &miss);
 
   __ bind(&not_array);
   __ CompareRoot(feedback, Heap::kmegamorphic_symbolRootIndex);
   __ j(not_equal, &miss);
 
-  Code::Flags code_flags = Code::RemoveTypeAndHolderFromFlags(
-      Code::ComputeHandlerFlags(Code::STORE_IC));
+  Code::Flags code_flags =
+      Code::RemoveHolderFromFlags(Code::ComputeHandlerFlags(Code::STORE_IC));
   masm->isolate()->stub_cache()->GenerateProbe(masm, Code::STORE_IC, code_flags,
                                                receiver, key, feedback, no_reg);
 
   __ bind(&miss);
   StoreIC::GenerateMiss(masm);
 
   __ bind(&load_smi_map);
   __ LoadRoot(receiver_map, Heap::kHeapNumberMapRootIndex);
   __ jmp(&compare_map);
 }
@@ skipping 1658 matching lines @@
                            NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64