[interpreter] Move temporary register allocator into own file.

src/identity-map.cc

 // 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.
 
 #include "src/identity-map.h"
 
 #include "src/heap/heap.h"
 #include "src/heap/heap-inl.h"
 #include "src/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 
 static const int kInitialIdentityMapSize = 4;
 static const int kResizeFactor = 4;
 
-IdentityMapBase::~IdentityMapBase() {
-  if (keys_) heap_->UnregisterStrongRoots(keys_);
+IdentityMapBase::~IdentityMapBase() { Clear(); }
+
+void IdentityMapBase::Clear() {
+  if (keys_) {
+    heap_->UnregisterStrongRoots(keys_);
+    keys_ = nullptr;
+    values_ = nullptr;
+    size_ = 0;
+    mask_ = 0;
+  }
 }
 
-
 IdentityMapBase::RawEntry IdentityMapBase::Lookup(Object* key) {
   int index = LookupIndex(key);
   return index >= 0 ? &values_[index] : nullptr;
 }
 
 
 IdentityMapBase::RawEntry IdentityMapBase::Insert(Object* key) {
   int index = InsertIndex(key);
   DCHECK_GE(index, 0);
   return &values_[index];
@@ skipping 149 matching lines @@
     DCHECK_GE(index, 0);
     values_[index] = old_values[i];
   }
 
   // Unregister old keys and register new keys.
   heap_->UnregisterStrongRoots(old_keys);
   heap_->RegisterStrongRoots(keys_, keys_ + size_);
 }
 }  // namespace internal
 }  // namespace v8