[turbofan][x64] Use the root register for comparisons with certain roots.

src/heap/heap.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_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 1005 matching lines @@
 
 #define SYMBOL_ACCESSOR(name, description) inline Symbol* name();
   PUBLIC_SYMBOL_LIST(SYMBOL_ACCESSOR)
   WELL_KNOWN_SYMBOL_LIST(SYMBOL_ACCESSOR)
 #undef SYMBOL_ACCESSOR
 
   Object* root(RootListIndex index) { return roots_[index]; }
   Handle<Object> root_handle(RootListIndex index) {
     return Handle<Object>(&roots_[index]);
   }
+  template <typename T>
+  bool IsRootHandle(Handle<T> handle, RootListIndex* index) const {
+    Object** const handle_location = bit_cast<Object**>(handle.address());
+    if (handle_location >= &roots_[kRootListLength]) return false;
+    if (handle_location < &roots_[0]) return false;
+    *index = static_cast<RootListIndex>(handle_location - &roots_[0]);
+    return true;
+  }
 
   // Generated code can embed this address to get access to the roots.
   Object** roots_array_start() { return roots_; }
 
   // Sets the stub_cache_ (only used when expanding the dictionary).
   void SetRootCodeStubs(UnseededNumberDictionary* value) {
     roots_[kCodeStubsRootIndex] = value;
   }
 
   void SetRootMaterializedObjects(FixedArray* objects) {
@@ skipping 1602 matching lines @@
   }
 
  private:
   Heap* heap_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_