[interpreter] Move temporary register allocator into own file.

src/identity-map.h

 // Copyright 2015 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_IDENTITY_MAP_H_
 #define V8_IDENTITY_MAP_H_
 
 #include "src/handles.h"
 
 namespace v8 {
@@ skipping 18 matching lines @@
         zone_(zone),
         gc_counter_(-1),
         size_(0),
         mask_(0),
         keys_(nullptr),
         values_(nullptr) {}
   ~IdentityMapBase();
 
   RawEntry GetEntry(Object* key);
   RawEntry FindEntry(Object* key);
+  void Clear();
 
  private:
   // Internal implementation should not be called directly by subclasses.
   int LookupIndex(Object* address);
   int InsertIndex(Object* address);
   void Rehash();
   void Resize();
   RawEntry Lookup(Object* key);
   RawEntry Insert(Object* key);
   int Hash(Object* address);
@@ skipping 29 matching lines @@
   // Searches this map for the given key using the object's address
   // as the identity, returning:
   //    found => a pointer to the storage location for the value
   //    not found => {nullptr}
   V* Find(Handle<Object> key) { return Find(*key); }
   V* Find(Object* key) { return reinterpret_cast<V*>(FindEntry(key)); }
 
   // Set the value for the given key.
   void Set(Handle<Object> key, V v) { Set(*key, v); }
   void Set(Object* key, V v) { *(reinterpret_cast<V*>(GetEntry(key))) = v; }
+
+  // Removes all elements from the map.
+  void Clear() { IdentityMapBase::Clear(); }
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_IDENTITY_MAP_H_