Revert of Replaced different means of zone pooling/reusing by one zone segment pool

src/compiler/zone-pool.h

+// Copyright 2014 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_COMPILER_ZONE_POOL_H_
+#define V8_COMPILER_ZONE_POOL_H_
+
+#include <map>
+#include <set>
+#include <vector>
+
+#include "src/zone/zone.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+class ZonePool final {
+ public:
+  class Scope final {
+   public:
+    explicit Scope(ZonePool* zone_pool)
+        : zone_pool_(zone_pool), zone_(nullptr) {}
+    ~Scope() { Destroy(); }
+
+    Zone* zone() {
+      if (zone_ == nullptr) zone_ = zone_pool_->NewEmptyZone();
+      return zone_;
+    }
+    void Destroy() {
+      if (zone_ != nullptr) zone_pool_->ReturnZone(zone_);
+      zone_ = nullptr;
+    }
+
+   private:
+    ZonePool* const zone_pool_;
+    Zone* zone_;
+    DISALLOW_COPY_AND_ASSIGN(Scope);
+  };
+
+  class StatsScope final {
+   public:
+    explicit StatsScope(ZonePool* zone_pool);
+    ~StatsScope();
+
+    size_t GetMaxAllocatedBytes();
+    size_t GetCurrentAllocatedBytes();
+    size_t GetTotalAllocatedBytes();
+
+   private:
+    friend class ZonePool;
+    void ZoneReturned(Zone* zone);
+
+    typedef std::map<Zone*, size_t> InitialValues;
+
+    ZonePool* const zone_pool_;
+    InitialValues initial_values_;
+    size_t total_allocated_bytes_at_start_;
+    size_t max_allocated_bytes_;
+
+    DISALLOW_COPY_AND_ASSIGN(StatsScope);
+  };
+
+  explicit ZonePool(AccountingAllocator* allocator);
+  ~ZonePool();
+
+  size_t GetMaxAllocatedBytes();
+  size_t GetTotalAllocatedBytes();
+  size_t GetCurrentAllocatedBytes();
+
+ private:
+  Zone* NewEmptyZone();
+  void ReturnZone(Zone* zone);
+
+  static const size_t kMaxUnusedSize = 3;
+  typedef std::vector<Zone*> Unused;
+  typedef std::vector<Zone*> Used;
+  typedef std::vector<StatsScope*> Stats;
+
+  Unused unused_;
+  Used used_;
+  Stats stats_;
+  size_t max_allocated_bytes_;
+  size_t total_deleted_bytes_;
+  AccountingAllocator* allocator_;
+
+  DISALLOW_COPY_AND_ASSIGN(ZonePool);
+};
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+
+#endif