remove unique_ptr from allocator static allocation (#3269)

* remove unique_ptr from allocator static allocation

* - for default allocator return address of the static object on stack instead of returning ptr to dynamically allocated object

* Revert "- for default allocator return address of the static object on stack instead of returning ptr to dynamically allocated object"

This reverts commit 126b269cb298e6eb8b99b1b9a90d5aa7cf8fb948.

* use raw pointer in set_host_memory_allocator

* fix build error

src/ngraph/runtime/allocator.cpp

@@ -51,6 +51,6 @@ public:
 
 ngraph::runtime::Allocator* ngraph::runtime::get_default_allocator()
 {
-    static std::unique_ptr<DefaultAllocator> allocator(new DefaultAllocator());
-    return allocator.get();
+    static DefaultAllocator* allocator = new DefaultAllocator();
+    return allocator;
 }

src/ngraph/runtime/backend.hpp

@@ -146,7 +146,7 @@ public:
     virtual Allocator* get_host_memory_allocator() { return nullptr; }
     /// \brief Set the host memory allocator to be used by the backend
     /// \param allocator is pointer to host memory allocator object
-    virtual void set_host_memory_allocator(std::unique_ptr<Allocator> allocator) {}
+    virtual void set_host_memory_allocator(Allocator* allocator) {}
     /// \brief Returns memory allocator used by backend for device allocations
     virtual Allocator* get_device_memory_allocator()
     {

src/ngraph/runtime/cpu/cpu_backend.cpp

@@ -187,11 +187,10 @@ runtime::Allocator* runtime::cpu::CPU_Backend::get_host_memory_allocator()
     {
         return runtime::get_default_allocator();
     }
-    return m_allocator.get();
+    return m_allocator;
 }
 
-void runtime::cpu::CPU_Backend::set_host_memory_allocator(
-    std::unique_ptr<runtime::Allocator> allocator)
+void runtime::cpu::CPU_Backend::set_host_memory_allocator(Allocator* allocator)
 {
     if (m_allocator)
     {
@@ -200,7 +199,7 @@ void runtime::cpu::CPU_Backend::set_host_memory_allocator(
         throw ngraph_error(
             "Allocator already exists. Changing allocators mid-execution is not permitted.");
     }
-    m_allocator = std::move(allocator);
+    m_allocator = allocator;
 }
 
 vector<runtime::PerformanceCounter> runtime::cpu::CPU_Executable::get_performance_data() const

src/ngraph/runtime/cpu/cpu_backend.hpp

@@ -65,7 +65,7 @@ namespace ngraph
                 void remove_compiled_function(std::shared_ptr<Executable> exec) override;
 
                 Allocator* get_host_memory_allocator() override;
-                void set_host_memory_allocator(std::unique_ptr<Allocator> allocator) override;
+                void set_host_memory_allocator(Allocator* allocator) override;
 
                 bool is_supported(const Node& node) const override;
                 bool is_supported_property(const Property prop) const override;
@@ -76,7 +76,7 @@ namespace ngraph
                 std::mutex m_exec_map_mutex;
                 std::unordered_map<std::shared_ptr<Function>, std::shared_ptr<Executable>>
                     m_exec_map;
-                std::unique_ptr<Allocator> m_allocator;
+                Allocator* m_allocator;
             };
 
             class CPU_BACKEND_API CPU_Executable : public runtime::Executable