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

src/ic/x64/stub-cache-x64.cc

 // 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/codegen.h"
 #include "src/ic/ic.h"
 #include "src/ic/stub-cache.h"
 #include "src/interface-descriptors.h"
@@ skipping 75 matching lines @@
                               Register extra2, Register extra3) {
   Isolate* isolate = masm->isolate();
   Label miss;
   USE(extra);   // The register extra is not used on the X64 platform.
   USE(extra2);  // The register extra2 is not used on the X64 platform.
   USE(extra3);  // The register extra2 is not used on the X64 platform.
   // Make sure that code is valid. The multiplying code relies on the
   // entry size being 3 * kPointerSize.
   DCHECK(sizeof(Entry) == 3 * kPointerSize);
 
-  // Make sure the flags do not name a specific type.
-  DCHECK(Code::ExtractTypeFromFlags(flags) == 0);
-
   // Make sure that there are no register conflicts.
   DCHECK(!scratch.is(receiver));
   DCHECK(!scratch.is(name));
 
   // Check scratch register is valid, extra and extra2 are unused.
   DCHECK(!scratch.is(no_reg));
   DCHECK(extra2.is(no_reg));
   DCHECK(extra3.is(no_reg));
 
 #ifdef DEBUG
@@ skipping 50 matching lines @@
   __ bind(&miss);
   __ IncrementCounter(counters->megamorphic_stub_cache_misses(), 1);
 }
 
 
 #undef __
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64