IVGCVSW-2056 + IVGCVSW-2064 : move ClContextControl to the ClBackend

Change-Id: Ice19d3f763298bc14585267df389e99df846320d

37 files changed, 338 insertions, 122 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 257a49d192..b33d4b6738 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -154,6 +154,7 @@ list(APPEND armnn_sources
     include/armnn/ILayerSupport.hpp
     include/armnn/INetwork.hpp
     include/armnn/IProfiler.hpp
+    include/armnn/IBackend.hpp
     include/armnn/IRuntime.hpp
     include/armnn/LayerSupport.hpp
     include/armnn/LstmParams.hpp
diff --git a/include/armnn/ArmNN.hpp b/include/armnn/ArmNN.hpp
index f03b79d1ca..a9bb451931 100644
--- a/include/armnn/ArmNN.hpp
+++ b/include/armnn/ArmNN.hpp
@@ -7,6 +7,7 @@
 #include "BackendId.hpp"
 #include "Descriptors.hpp"
 #include "Exceptions.hpp"
+#include "IBackend.hpp"
 #include "IRuntime.hpp"
 #include "INetwork.hpp"
 #include "LayerSupport.hpp"
diff --git a/include/armnn/IBackend.hpp b/include/armnn/IBackend.hpp
new file mode 100644
index 0000000000..34df91c803
--- /dev/null
+++ b/include/armnn/IBackend.hpp
@@ -0,0 +1,22 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+#pragma once
+
+#include "BackendId.hpp"
+
+namespace armnn
+{
+
+class IBackend
+{
+protected:
+    IBackend() {}
+    virtual ~IBackend() {}
+
+public:
+    virtual const BackendId& GetId() const = 0;
+};
+
+} // namespace armnn
\ No newline at end of file
diff --git a/include/armnn/Types.hpp b/include/armnn/Types.hpp
index cd6e17be37..2249a365d2 100644
--- a/include/armnn/Types.hpp
+++ b/include/armnn/Types.hpp
@@ -139,20 +139,6 @@ enum class OutputShapeRounding
     Ceiling     = 1
 };
 
-/// Each backend should implement an IBackend.
-class IBackend
-{
-protected:
-    IBackend() {}
-    virtual ~IBackend() {}
-
-public:
-    virtual const BackendId& GetId() const = 0;
-};
-
-using IBackendSharedPtr = std::shared_ptr<IBackend>;
-using IBackendUniquePtr = std::unique_ptr<IBackend, void(*)(IBackend* backend)>;
-
 /// Device specific knowledge to be passed to the optimizer.
 class IDeviceSpec
 {
@@ -222,4 +208,6 @@ private:
 /// Define LayerGuid type.
 using LayerGuid = unsigned int;
 
+struct EmptyInitializer {};
+
 } // namespace armnn
diff --git a/src/armnn/LayerSupport.cpp b/src/armnn/LayerSupport.cpp
index 846da6086e..249c8f4654 100644
--- a/src/armnn/LayerSupport.cpp
+++ b/src/armnn/LayerSupport.cpp
@@ -39,7 +39,7 @@ void CopyErrorMessage(char* truncatedString, const char* fullString, size_t maxL
     bool isSupported; \
     try { \
         auto factoryFunc = LayerSupportRegistryInstance().GetFactory(backendId); \
-        auto layerSupportObject = factoryFunc(); \
+        auto layerSupportObject = factoryFunc(EmptyInitializer()); \
         isSupported = layerSupportObject->func(__VA_ARGS__, Optional<std::string&>(reasonIfUnsupportedFull)); \
         CopyErrorMessage(reasonIfUnsupported, reasonIfUnsupportedFull.c_str(), reasonIfUnsupportedMaxLength); \
     } catch (InvalidArgumentException e) { \
diff --git a/src/armnn/LoadedNetwork.cpp b/src/armnn/LoadedNetwork.cpp
index 40137779f6..616a0327fe 100644
--- a/src/armnn/LoadedNetwork.cpp
+++ b/src/armnn/LoadedNetwork.cpp
@@ -38,6 +38,7 @@ std::string ToErrorMessage(const char * prefix, const ExceptionType & error)
 } // anonymous
 
 std::unique_ptr<LoadedNetwork> LoadedNetwork::MakeLoadedNetwork(std::unique_ptr<OptimizedNetwork> net,
+                                                                const IRuntime::CreationOptions& options,
                                                                 std::string & errorMessage)
 {
     std::unique_ptr<LoadedNetwork> loadedNetwork;
@@ -52,7 +53,7 @@ std::unique_ptr<LoadedNetwork> LoadedNetwork::MakeLoadedNetwork(std::unique_ptr<
 
     try
     {
-        loadedNetwork.reset(new LoadedNetwork(std::move(net)));
+        loadedNetwork.reset(new LoadedNetwork(std::move(net), options));
     }
     catch (const armnn::RuntimeException& error)
     {
@@ -70,7 +71,8 @@ std::unique_ptr<LoadedNetwork> LoadedNetwork::MakeLoadedNetwork(std::unique_ptr<
     return loadedNetwork;
 }
 
-LoadedNetwork::LoadedNetwork(std::unique_ptr<OptimizedNetwork> net)
+LoadedNetwork::LoadedNetwork(std::unique_ptr<OptimizedNetwork> net,
+                             const IRuntime::CreationOptions& options)
     : m_OptimizedNetwork(std::move(net))
     , m_WorkingMemLock(m_WorkingMemMutex, std::defer_lock)
 {
@@ -89,7 +91,7 @@ LoadedNetwork::LoadedNetwork(std::unique_ptr<OptimizedNetwork> net)
         if (m_Backends.count(backend) == 0)
         {
             auto createBackend = BackendRegistryInstance().GetFactory(backend);
-            auto it = m_Backends.emplace(std::make_pair(backend, createBackend()));
+            auto it = m_Backends.emplace(std::make_pair(backend, createBackend(EmptyInitializer())));
             m_WorkloadFactories.emplace(std::make_pair(backend,
                                                        it.first->second->CreateWorkloadFactory()));
         }
diff --git a/src/armnn/LoadedNetwork.hpp b/src/armnn/LoadedNetwork.hpp
index 51eb04f3df..21de1440f1 100644
--- a/src/armnn/LoadedNetwork.hpp
+++ b/src/armnn/LoadedNetwork.hpp
@@ -40,6 +40,7 @@ public:
     Status EnqueueWorkload(const InputTensors& inputTensors, const OutputTensors& outputTensors);
 
     static std::unique_ptr<LoadedNetwork> MakeLoadedNetwork(std::unique_ptr<OptimizedNetwork> net,
+                                                            const IRuntime::CreationOptions& options,
                                                             std::string & errorMessage);
 
     // NOTE we return by reference as the purpose of this method is only to provide
@@ -51,7 +52,7 @@ public:
     void FreeWorkingMemory();
 
 private:
-    LoadedNetwork(std::unique_ptr<OptimizedNetwork> net);
+    LoadedNetwork(std::unique_ptr<OptimizedNetwork> net, const IRuntime::CreationOptions& options);
 
     void EnqueueInput(const BindableLayer& layer, ITensorHandle* tensorHandle, const TensorInfo& tensorInfo);
 
diff --git a/src/armnn/Runtime.cpp b/src/armnn/Runtime.cpp
index e84cbe0a60..a0aca6ebc7 100644
--- a/src/armnn/Runtime.cpp
+++ b/src/armnn/Runtime.cpp
@@ -6,15 +6,10 @@
 
 #include <armnn/Version.hpp>
 #include <backends/BackendRegistry.hpp>
+#include <backends/BackendContextRegistry.hpp>
 
 #include <iostream>
 
-#ifdef ARMCOMPUTECL_ENABLED
-#include <arm_compute/core/CL/OpenCL.h>
-#include <arm_compute/core/CL/CLKernelLibrary.h>
-#include <arm_compute/runtime/CL/CLScheduler.h>
-#endif
-
 #include <boost/log/trivial.hpp>
 #include <boost/polymorphic_cast.hpp>
 
@@ -57,6 +52,7 @@ Status Runtime::LoadNetwork(NetworkId& networkIdOut,
     IOptimizedNetwork* rawNetwork = inNetwork.release();
     unique_ptr<LoadedNetwork> loadedNetwork = LoadedNetwork::MakeLoadedNetwork(
         std::unique_ptr<OptimizedNetwork>(boost::polymorphic_downcast<OptimizedNetwork*>(rawNetwork)),
+        m_Options,
         errorMessage);
 
     if (!loadedNetwork)
@@ -78,24 +74,6 @@ Status Runtime::LoadNetwork(NetworkId& networkIdOut,
 
 Status Runtime::UnloadNetwork(NetworkId networkId)
 {
-#ifdef ARMCOMPUTECL_ENABLED
-    if (arm_compute::CLScheduler::get().context()() != NULL)
-    {
-        // Waits for all queued CL requests to finish before unloading the network they may be using.
-        try
-        {
-            // Coverity fix: arm_compute::CLScheduler::sync() may throw an exception of type cl::Error.
-            arm_compute::CLScheduler::get().sync();
-        }
-        catch (const cl::Error&)
-        {
-            BOOST_LOG_TRIVIAL(warning) << "WARNING: Runtime::UnloadNetwork(): an error occurred while waiting for "
-                                          "the queued CL requests to finish";
-            return Status::Failure;
-        }
-    }
-#endif
-
     {
         std::lock_guard<std::mutex> lockGuard(m_Mutex);
 
@@ -104,14 +82,6 @@ Status Runtime::UnloadNetwork(NetworkId networkId)
             BOOST_LOG_TRIVIAL(warning) << "WARNING: Runtime::UnloadNetwork(): " << networkId << " not found!";
             return Status::Failure;
         }
-
-#ifdef ARMCOMPUTECL_ENABLED
-        if (arm_compute::CLScheduler::get().context()() != NULL && m_LoadedNetworks.empty())
-        {
-            // There are no loaded networks left, so clear the CL cache to free up memory
-            m_ClContextControl.ClearClCache();
-        }
-#endif
     }
 
     BOOST_LOG_TRIVIAL(debug) << "Runtime::UnloadNetwork(): Unloaded network with ID: " << networkId;
@@ -131,12 +101,26 @@ const std::shared_ptr<IProfiler> Runtime::GetProfiler(NetworkId networkId) const
 }
 
 Runtime::Runtime(const CreationOptions& options)
-    : m_ClContextControl(options.m_GpuAccTunedParameters.get(),
-                         options.m_EnableGpuProfiling)
+    : m_Options{options}
     , m_NetworkIdCounter(0)
     , m_DeviceSpec{BackendRegistryInstance().GetBackendIds()}
 {
     BOOST_LOG_TRIVIAL(info) << "ArmNN v" << ARMNN_VERSION << "\n";
+
+    for (const auto& id : BackendContextRegistryInstance().GetBackendIds())
+    {
+        // Store backend contexts for the supported ones
+        if (m_DeviceSpec.GetSupportedBackends().count(id) > 0)
+        {
+            // Don't throw an exception, rather return a dummy factory if not
+            // found.
+            auto factoryFun = BackendContextRegistryInstance().GetFactory(
+                id, [](const CreationOptions&) { return IBackendContextUniquePtr(); }
+            );
+
+            m_BackendContexts.emplace(std::make_pair(id, factoryFun(options)));
+        }
+    }
 }
 
 Runtime::~Runtime()
diff --git a/src/armnn/Runtime.hpp b/src/armnn/Runtime.hpp
index 29bb6808d8..2679e3cc98 100644
--- a/src/armnn/Runtime.hpp
+++ b/src/armnn/Runtime.hpp
@@ -9,7 +9,8 @@
 #include <armnn/INetwork.hpp>
 #include <armnn/IRuntime.hpp>
 #include <armnn/Tensor.hpp>
-#include <backends/cl/ClContextControl.hpp>
+#include <armnn/BackendId.hpp>
+#include <backends/IBackendContext.hpp>
 
 #include <mutex>
 #include <unordered_map>
@@ -85,14 +86,13 @@ private:
     }
 
     mutable std::mutex m_Mutex;
-
     std::unordered_map<NetworkId, std::unique_ptr<LoadedNetwork>> m_LoadedNetworks;
-
-    ClContextControl m_ClContextControl;
-
+    CreationOptions m_Options;
     int m_NetworkIdCounter;
-
     DeviceSpec m_DeviceSpec;
+
+    using BackendContextMap = std::unordered_map<BackendId, IBackendContextUniquePtr>;
+    BackendContextMap m_BackendContexts;
 };
 
 }
diff --git a/src/backends/BackendContextRegistry.cpp b/src/backends/BackendContextRegistry.cpp
new file mode 100644
index 0000000000..0168a127af
--- /dev/null
+++ b/src/backends/BackendContextRegistry.cpp
@@ -0,0 +1,17 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+
+#include "BackendContextRegistry.hpp"
+
+namespace armnn
+{
+
+BackendContextRegistry& BackendContextRegistryInstance()
+{
+    static BackendContextRegistry instance;
+    return instance;
+}
+
+} // namespace armnn
diff --git a/src/backends/BackendContextRegistry.hpp b/src/backends/BackendContextRegistry.hpp
new file mode 100644
index 0000000000..c48d5b2c4b
--- /dev/null
+++ b/src/backends/BackendContextRegistry.hpp
@@ -0,0 +1,27 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+#pragma once
+
+#include <armnn/Types.hpp>
+#include <armnn/IRuntime.hpp>
+#include "RegistryCommon.hpp"
+#include "IBackendContext.hpp"
+
+namespace armnn
+{
+
+using BackendContextRegistry = RegistryCommon<IBackendContext,
+                                              IBackendContextUniquePtr,
+                                              IRuntime::CreationOptions>;
+
+BackendContextRegistry& BackendContextRegistryInstance();
+
+template <>
+struct RegisteredTypeName<IBackendContext>
+{
+    static const char * Name() { return "IBackendContext"; }
+};
+
+} // namespace armnn
diff --git a/src/backends/BackendRegistry.hpp b/src/backends/BackendRegistry.hpp
index 4465e95174..8f8ad37481 100644
--- a/src/backends/BackendRegistry.hpp
+++ b/src/backends/BackendRegistry.hpp
@@ -11,7 +11,9 @@
 namespace armnn
 {
 
-using BackendRegistry = RegistryCommon<IBackendInternal, IBackendInternalUniquePtr>;
+using BackendRegistry = RegistryCommon<IBackendInternal,
+                                       IBackendInternalUniquePtr,
+                                       EmptyInitializer>;
 
 BackendRegistry& BackendRegistryInstance();
 
diff --git a/src/backends/CMakeLists.txt b/src/backends/CMakeLists.txt
index 045bd2ac27..843e567201 100644
--- a/src/backends/CMakeLists.txt
+++ b/src/backends/CMakeLists.txt
@@ -4,11 +4,14 @@
 #
 
 list(APPEND armnnBackendsCommon_sources
+    BackendContextRegistry.cpp
+    BackendContextRegistry.hpp
     BackendRegistry.cpp
     BackendRegistry.hpp
     CpuTensorHandle.cpp
     CpuTensorHandleFwd.hpp
     CpuTensorHandle.hpp
+    IBackendContext.hpp
     IBackendInternal.hpp
     ILayerSupport.cpp
     ITensorHandle.hpp
diff --git a/src/backends/IBackendContext.hpp b/src/backends/IBackendContext.hpp
new file mode 100644
index 0000000000..d073d12868
--- /dev/null
+++ b/src/backends/IBackendContext.hpp
@@ -0,0 +1,27 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+#pragma once
+
+#include <armnn/IRuntime.hpp>
+#include <memory>
+
+namespace armnn
+{
+
+class IBackendContext
+{
+public:
+    virtual ~IBackendContext() {}
+
+protected:
+    IBackendContext(const IRuntime::CreationOptions& options) {}
+
+private:
+    IBackendContext() = delete;
+};
+
+using IBackendContextUniquePtr = std::unique_ptr<IBackendContext>;
+
+} // namespace armnn
diff --git a/src/backends/IBackendInternal.hpp b/src/backends/IBackendInternal.hpp
index 7e44dbd676..a24b60064a 100644
--- a/src/backends/IBackendInternal.hpp
+++ b/src/backends/IBackendInternal.hpp
@@ -4,7 +4,8 @@
 //
 #pragma once
 
-#include <armnn/Types.hpp>
+#include <armnn/IBackend.hpp>
+#include <memory>
 
 namespace armnn
 {
@@ -13,8 +14,6 @@ class IWorkloadFactory;
 class IBackendInternal : public IBackend
 {
 protected:
-    // Creation must be done through a specific
-    // backend interface.
     IBackendInternal() = default;
 
 public:
diff --git a/src/backends/LayerSupportRegistry.hpp b/src/backends/LayerSupportRegistry.hpp
index a5efad05ef..6124685032 100644
--- a/src/backends/LayerSupportRegistry.hpp
+++ b/src/backends/LayerSupportRegistry.hpp
@@ -6,11 +6,13 @@
 
 #include "RegistryCommon.hpp"
 #include <armnn/ILayerSupport.hpp>
+#include <armnn/Types.hpp>
 
 namespace armnn
 {
-
-using LayerSupportRegistry = RegistryCommon<ILayerSupport, ILayerSupportSharedPtr>;
+using LayerSupportRegistry = RegistryCommon<ILayerSupport,
+                                            ILayerSupportSharedPtr,
+                                            EmptyInitializer>;
 
 LayerSupportRegistry& LayerSupportRegistryInstance();
 
diff --git a/src/backends/RegistryCommon.hpp b/src/backends/RegistryCommon.hpp
index 616a63bd53..044a9e4250 100644
--- a/src/backends/RegistryCommon.hpp
+++ b/src/backends/RegistryCommon.hpp
@@ -21,11 +21,11 @@ struct RegisteredTypeName
     static const char * Name() { return "UNKNOWN"; }
 };
 
-template <typename RegisteredType, typename PointerType>
+template <typename RegisteredType, typename PointerType, typename ParamType>
 class RegistryCommon
 {
 public:
-    using FactoryFunction = std::function<PointerType()>;
+    using FactoryFunction = std::function<PointerType(const ParamType&)>;
 
     void Register(const BackendId& id, FactoryFunction factory)
     {
@@ -52,6 +52,20 @@ public:
         return it->second;
     }
 
+    FactoryFunction GetFactory(const BackendId& id,
+                               FactoryFunction defaultFactory) const
+    {
+        auto it = m_Factories.find(id);
+        if (it == m_Factories.end())
+        {
+            return defaultFactory;
+        }
+        else
+        {
+            return it->second;
+        }
+    }
+
     size_t Size() const
     {
         return m_Factories.size();
@@ -116,4 +130,4 @@ struct StaticRegistryInitializer
     }
 };
 
-} // namespace armnn
+} // namespace armnn
\ No newline at end of file
diff --git a/src/backends/WorkloadFactory.cpp b/src/backends/WorkloadFactory.cpp
index fea383f030..2e7a24f732 100644
--- a/src/backends/WorkloadFactory.cpp
+++ b/src/backends/WorkloadFactory.cpp
@@ -64,7 +64,7 @@ bool IWorkloadFactory::IsLayerSupported(const BackendId& backendId,
 
     auto const& layerSupportRegistry = LayerSupportRegistryInstance();
     auto layerSupportFactory = layerSupportRegistry.GetFactory(backendId);
-    auto layerSupportObject = layerSupportFactory();
+    auto layerSupportObject = layerSupportFactory(EmptyInitializer());
 
     switch(layer.GetType())
     {
diff --git a/src/backends/cl/CMakeLists.txt b/src/backends/cl/CMakeLists.txt
index 7182332956..a0f1e4d9cc 100644
--- a/src/backends/cl/CMakeLists.txt
+++ b/src/backends/cl/CMakeLists.txt
@@ -3,18 +3,23 @@
 # SPDX-License-Identifier: MIT
 #
 
+list(APPEND armnnClBackend_sources
+    ClBackendId.hpp
+    ClLayerSupport.cpp
+    ClLayerSupport.hpp
+    ClWorkloadFactory.cpp
+    ClWorkloadFactory.hpp
+)
+
 if(ARMCOMPUTECL)
     list(APPEND armnnClBackend_sources
+        ClBackendContext.cpp
+        ClBackendContext.hpp
         ClBackend.cpp
         ClBackend.hpp
-        ClBackendId.hpp
         ClContextControl.cpp
         ClContextControl.hpp
-        ClLayerSupport.cpp
-        ClLayerSupport.hpp
         ClTensorHandle.hpp
-        ClWorkloadFactory.cpp
-        ClWorkloadFactory.hpp
         OpenClTimer.cpp
         OpenClTimer.hpp
     )
@@ -24,20 +29,10 @@ if(ARMCOMPUTECL)
     if(BUILD_UNIT_TESTS)
         add_subdirectory(test)
     endif()
-
-else()
-    list(APPEND armnnClBackend_sources
-        ClBackendId.hpp
-        ClContextControl.cpp
-        ClContextControl.hpp
-        ClLayerSupport.cpp
-        ClLayerSupport.hpp
-        ClWorkloadFactory.cpp
-        ClWorkloadFactory.hpp
-    )
 endif()
 
 add_library(armnnClBackend OBJECT ${armnnClBackend_sources})
 target_include_directories(armnnClBackend PRIVATE ${PROJECT_SOURCE_DIR}/src)
 target_include_directories(armnnClBackend PRIVATE ${PROJECT_SOURCE_DIR}/src/armnn)
 target_include_directories(armnnClBackend PRIVATE ${PROJECT_SOURCE_DIR}/src/armnnUtils)
+
diff --git a/src/backends/cl/ClBackend.cpp b/src/backends/cl/ClBackend.cpp
index d6a3a89391..da91de8e48 100644
--- a/src/backends/cl/ClBackend.cpp
+++ b/src/backends/cl/ClBackend.cpp
@@ -8,8 +8,7 @@
 #include "ClWorkloadFactory.hpp"
 
 #include <backends/BackendRegistry.hpp>
-
-#include <boost/cast.hpp>
+#include <boost/log/trivial.hpp>
 
 namespace armnn
 {
@@ -21,13 +20,13 @@ static StaticRegistryInitializer<BackendRegistry> g_RegisterHelper
 {
     BackendRegistryInstance(),
     ClBackend::GetIdStatic(),
-    []()
+    [](const EmptyInitializer&)
     {
         return IBackendInternalUniquePtr(new ClBackend);
     }
 };
 
-}
+} // anonymous namespace
 
 const BackendId& ClBackend::GetIdStatic()
 {
diff --git a/src/backends/cl/ClBackend.hpp b/src/backends/cl/ClBackend.hpp
index 4eae6c92ec..201702eee3 100644
--- a/src/backends/cl/ClBackend.hpp
+++ b/src/backends/cl/ClBackend.hpp
@@ -12,8 +12,8 @@ namespace armnn
 class ClBackend : public IBackendInternal
 {
 public:
-    ClBackend()  = default;
-    ~ClBackend() = default;
+    ClBackend() = default;
+    ~ClBackend() override = default;
 
     static const BackendId& GetIdStatic();
     const BackendId& GetId() const override { return GetIdStatic(); }
diff --git a/src/backends/cl/ClBackendContext.cpp b/src/backends/cl/ClBackendContext.cpp
new file mode 100644
index 0000000000..4d1be33fc6
--- /dev/null
+++ b/src/backends/cl/ClBackendContext.cpp
@@ -0,0 +1,111 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+
+#include "ClBackendContext.hpp"
+#include "ClBackendId.hpp"
+#include "ClContextControl.hpp"
+
+#include <backends/BackendContextRegistry.hpp>
+#include <boost/log/trivial.hpp>
+
+#include <mutex>
+
+#ifdef ARMCOMPUTECL_ENABLED
+// Needed for the CL scheduler calls
+#include <arm_compute/core/CL/OpenCL.h>
+#include <arm_compute/core/CL/CLKernelLibrary.h>
+#include <arm_compute/runtime/CL/CLScheduler.h>
+#endif
+
+namespace armnn
+{
+
+namespace
+{
+
+static StaticRegistryInitializer<BackendContextRegistry> g_RegisterHelper
+{
+    BackendContextRegistryInstance(),
+    ClBackendId(),
+    [](const IRuntime::CreationOptions& options)
+    {
+        return IBackendContextUniquePtr(new ClBackendContext{options});
+    }
+};
+
+static std::mutex g_ContextControlMutex;
+
+std::shared_ptr<ClBackendContext::ContextControlWrapper>
+GetContextControlWrapper(const IRuntime::CreationOptions& options)
+{
+    static std::weak_ptr<ClBackendContext::ContextControlWrapper> contextControlWrapper;
+
+    std::lock_guard<std::mutex> lockGuard(g_ContextControlMutex);
+    std::shared_ptr<ClBackendContext::ContextControlWrapper> result;
+
+    if (contextControlWrapper.expired())
+    {
+        result = std::make_shared<ClBackendContext::ContextControlWrapper>(options);
+        contextControlWrapper = result;
+    }
+    else
+    {
+        result = contextControlWrapper.lock();
+    }
+
+    return result;
+}
+
+} // anonymous namespace
+
+
+#ifdef ARMCOMPUTECL_ENABLED
+struct ClBackendContext::ContextControlWrapper
+{
+    ContextControlWrapper(const IRuntime::CreationOptions& options)
+    : m_ClContextControl{options.m_GpuAccTunedParameters.get(),
+                         options.m_EnableGpuProfiling}
+    {
+    }
+
+    ~ContextControlWrapper()
+    {
+        if (arm_compute::CLScheduler::get().context()() != NULL)
+        {
+            // Waits for all queued CL requests to finish before unloading the network they may be using.
+            try
+            {
+                // Coverity fix: arm_compute::CLScheduler::sync() may throw an exception of type cl::Error.
+                arm_compute::CLScheduler::get().sync();
+                m_ClContextControl.ClearClCache();
+            }
+            catch (const cl::Error&)
+            {
+                BOOST_LOG_TRIVIAL(warning) << "WARNING: Runtime::UnloadNetwork(): an error occurred while waiting for "
+                                            "the queued CL requests to finish";
+            }
+        }
+    }
+
+    ClContextControl m_ClContextControl;
+};
+#else //ARMCOMPUTECL_ENABLED
+struct ClBackendContext::ContextControlWrapper
+{
+    ContextControlWrapper(const IRuntime::CreationOptions&){}
+};
+#endif //ARMCOMPUTECL_ENABLED
+
+ClBackendContext::ClBackendContext(const IRuntime::CreationOptions& options)
+: IBackendContext{options}
+, m_ContextControl{GetContextControlWrapper(options)}
+{
+}
+
+ClBackendContext::~ClBackendContext()
+{
+}
+
+} // namespace armnn
\ No newline at end of file
diff --git a/src/backends/cl/ClBackendContext.hpp b/src/backends/cl/ClBackendContext.hpp
new file mode 100644
index 0000000000..3df403efc5
--- /dev/null
+++ b/src/backends/cl/ClBackendContext.hpp
@@ -0,0 +1,23 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+#pragma once
+
+#include <backends/IBackendContext.hpp>
+
+namespace armnn
+{
+
+class ClBackendContext : public IBackendContext
+{
+public:
+    ClBackendContext(const IRuntime::CreationOptions& options);
+    ~ClBackendContext() override;
+
+    struct ContextControlWrapper;
+private:
+    std::shared_ptr<ContextControlWrapper> m_ContextControl;
+};
+
+} // namespace armnn
\ No newline at end of file
diff --git a/src/backends/cl/ClLayerSupport.cpp b/src/backends/cl/ClLayerSupport.cpp
index 6c5704d7ab..ebb90a5abf 100644
--- a/src/backends/cl/ClLayerSupport.cpp
+++ b/src/backends/cl/ClLayerSupport.cpp
@@ -53,7 +53,7 @@ ILayerSupportSharedPtr GetLayerSupportPointer()
 static StaticRegistryInitializer<LayerSupportRegistry> g_RegisterHelper{
     LayerSupportRegistryInstance(),
     ClBackendId(),
-    []()
+    [](const EmptyInitializer&)
     {
         return GetLayerSupportPointer();
     }
diff --git a/src/backends/cl/backend.mk b/src/backends/cl/backend.mk
index 97df8e4903..8433240ae9 100644
--- a/src/backends/cl/backend.mk
+++ b/src/backends/cl/backend.mk
@@ -8,6 +8,7 @@
 # file in the root of ArmNN
 
 BACKEND_SOURCES := \
+        ClBackendContext.cpp \
         ClBackend.cpp \
         ClContextControl.cpp \
         ClLayerSupport.cpp \
@@ -54,3 +55,4 @@ BACKEND_TEST_SOURCES := \
         test/ClRuntimeTests.cpp \
         test/Fp16SupportTest.cpp \
         test/OpenClTimerTest.cpp
+
diff --git a/src/backends/common.mk b/src/backends/common.mk
index b1583b987e..152ada3532 100644
--- a/src/backends/common.mk
+++ b/src/backends/common.mk
@@ -8,6 +8,7 @@
 # file in the root of ArmNN
 
 COMMON_SOURCES := \
+    BackendContextRegistry.cpp \
     BackendRegistry.cpp \
     CpuTensorHandle.cpp \
     ILayerSupport.cpp \
@@ -26,3 +27,4 @@ COMMON_TEST_SOURCES := \
     test/WorkloadDataValidation.cpp \
     test/TensorCopyUtils.cpp \
     test/LayerTests.cpp
+
diff --git a/src/backends/neon/CMakeLists.txt b/src/backends/neon/CMakeLists.txt
index 058553dd34..b5e6ff33f5 100644
--- a/src/backends/neon/CMakeLists.txt
+++ b/src/backends/neon/CMakeLists.txt
@@ -3,17 +3,20 @@
 # SPDX-License-Identifier: MIT
 #
 
+list(APPEND armnnNeonBackend_sources
+    NeonBackendId.hpp
+    NeonLayerSupport.cpp
+    NeonLayerSupport.hpp
+    NeonWorkloadFactory.cpp
+    NeonWorkloadFactory.hpp
+)
+
 if(ARMCOMPUTENEON)
     list(APPEND armnnNeonBackend_sources
         NeonBackend.cpp
         NeonBackend.hpp
-        NeonBackendId.hpp
         NeonInterceptorScheduler.hpp
         NeonInterceptorScheduler.cpp
-        NeonLayerSupport.cpp
-        NeonLayerSupport.hpp
-        NeonWorkloadFactory.cpp
-        NeonWorkloadFactory.hpp
         NeonTensorHandle.hpp
         NeonTimer.hpp
         NeonTimer.cpp
@@ -24,18 +27,10 @@ if(ARMCOMPUTENEON)
     if(BUILD_UNIT_TESTS)
         add_subdirectory(test)
     endif()
-
-else()
-    list(APPEND armnnNeonBackend_sources
-        NeonBackendId.hpp
-        NeonLayerSupport.cpp
-        NeonLayerSupport.hpp
-        NeonWorkloadFactory.cpp
-        NeonWorkloadFactory.hpp
-    )
 endif()
 
 add_library(armnnNeonBackend OBJECT ${armnnNeonBackend_sources})
 target_include_directories(armnnNeonBackend PRIVATE ${PROJECT_SOURCE_DIR}/src)
 target_include_directories(armnnNeonBackend PRIVATE ${PROJECT_SOURCE_DIR}/src/armnn)
 target_include_directories(armnnNeonBackend PRIVATE ${PROJECT_SOURCE_DIR}/src/armnnUtils)
+
diff --git a/src/backends/neon/NeonBackend.cpp b/src/backends/neon/NeonBackend.cpp
index e475f0232b..f8d7bb0785 100644
--- a/src/backends/neon/NeonBackend.cpp
+++ b/src/backends/neon/NeonBackend.cpp
@@ -9,8 +9,6 @@
 
 #include <backends/BackendRegistry.hpp>
 
-#include <boost/cast.hpp>
-
 namespace armnn
 {
 
@@ -21,7 +19,7 @@ static StaticRegistryInitializer<BackendRegistry> g_RegisterHelper
 {
     BackendRegistryInstance(),
     NeonBackend::GetIdStatic(),
-    []()
+    [](const EmptyInitializer&)
     {
         return IBackendInternalUniquePtr(new NeonBackend);
     }
diff --git a/src/backends/neon/NeonBackend.hpp b/src/backends/neon/NeonBackend.hpp
index e1287c784c..d74962be91 100644
--- a/src/backends/neon/NeonBackend.hpp
+++ b/src/backends/neon/NeonBackend.hpp
@@ -12,8 +12,8 @@ namespace armnn
 class NeonBackend : public IBackendInternal
 {
 public:
-    NeonBackend()  = default;
-    ~NeonBackend() = default;
+    NeonBackend() = default;
+    ~NeonBackend() override = default;
 
     static const BackendId& GetIdStatic();
     const BackendId& GetId() const override { return GetIdStatic(); }
diff --git a/src/backends/neon/NeonLayerSupport.cpp b/src/backends/neon/NeonLayerSupport.cpp
index 3638212c75..71a5be3b17 100644
--- a/src/backends/neon/NeonLayerSupport.cpp
+++ b/src/backends/neon/NeonLayerSupport.cpp
@@ -49,7 +49,7 @@ ILayerSupportSharedPtr GetLayerSupportPointer()
 static StaticRegistryInitializer<LayerSupportRegistry> g_RegisterHelper{
     LayerSupportRegistryInstance(),
     NeonBackendId(),
-    []()
+    [](const EmptyInitializer&)
     {
         return GetLayerSupportPointer();
     }
diff --git a/src/backends/neon/backend.mk b/src/backends/neon/backend.mk
index 8f7e72b17c..29b3527542 100644
--- a/src/backends/neon/backend.mk
+++ b/src/backends/neon/backend.mk
@@ -49,3 +49,4 @@ BACKEND_TEST_SOURCES := \
         test/NeonOptimizedNetworkTests.cpp \
         test/NeonRuntimeTests.cpp \
         test/NeonTimerTest.cpp
+
diff --git a/src/backends/reference/CMakeLists.txt b/src/backends/reference/CMakeLists.txt
index 5f698f4e9d..e2656d552e 100644
--- a/src/backends/reference/CMakeLists.txt
+++ b/src/backends/reference/CMakeLists.txt
@@ -23,3 +23,4 @@ add_subdirectory(workloads)
 if(BUILD_UNIT_TESTS)
     add_subdirectory(test)
 endif()
+
diff --git a/src/backends/reference/RefBackend.cpp b/src/backends/reference/RefBackend.cpp
index 34348fa120..3aa4f038c5 100644
--- a/src/backends/reference/RefBackend.cpp
+++ b/src/backends/reference/RefBackend.cpp
@@ -9,8 +9,6 @@
 
 #include <backends/BackendRegistry.hpp>
 
-#include <boost/cast.hpp>
-
 namespace armnn
 {
 
@@ -21,7 +19,7 @@ static StaticRegistryInitializer<BackendRegistry> g_RegisterHelper
 {
     BackendRegistryInstance(),
     RefBackend::GetIdStatic(),
-    []()
+    [](const EmptyInitializer&)
     {
         return IBackendInternalUniquePtr(new RefBackend);
     }
diff --git a/src/backends/reference/RefBackend.hpp b/src/backends/reference/RefBackend.hpp
index 7162c9bf40..1949e77ff5 100644
--- a/src/backends/reference/RefBackend.hpp
+++ b/src/backends/reference/RefBackend.hpp
@@ -12,8 +12,8 @@ namespace armnn
 class RefBackend : public IBackendInternal
 {
 public:
-    RefBackend()  = default;
-    ~RefBackend() = default;
+    RefBackend() = default;
+    ~RefBackend() override = default;
 
     static const BackendId& GetIdStatic();
     const BackendId& GetId() const override { return GetIdStatic(); }
diff --git a/src/backends/reference/RefLayerSupport.cpp b/src/backends/reference/RefLayerSupport.cpp
index 253d9c2294..79d4ab0dd1 100644
--- a/src/backends/reference/RefLayerSupport.cpp
+++ b/src/backends/reference/RefLayerSupport.cpp
@@ -31,7 +31,7 @@ ILayerSupportSharedPtr GetLayerSupportPointer()
 static StaticRegistryInitializer<LayerSupportRegistry> g_RegisterHelper{
     LayerSupportRegistryInstance(),
     RefBackendId(),
-    []()
+    [](const EmptyInitializer&)
     {
         return GetLayerSupportPointer();
     }
diff --git a/src/backends/reference/backend.mk b/src/backends/reference/backend.mk
index 007efceb9b..8a8a78a315 100644
--- a/src/backends/reference/backend.mk
+++ b/src/backends/reference/backend.mk
@@ -71,3 +71,4 @@ BACKEND_TEST_SOURCES := \
         test/RefLayerTests.cpp \
         test/RefOptimizedNetworkTests.cpp \
         test/RefRuntimeTests.cpp
+
diff --git a/src/backends/test/BackendRegistryTests.cpp b/src/backends/test/BackendRegistryTests.cpp
index 34a2706466..bfeefda6bd 100644
--- a/src/backends/test/BackendRegistryTests.cpp
+++ b/src/backends/test/BackendRegistryTests.cpp
@@ -52,7 +52,7 @@ BOOST_AUTO_TEST_CASE(TestRegistryHelper)
     StaticRegistryInitializer<BackendRegistry> factoryHelper(
         BackendRegistryInstance(),
         "HelloWorld",
-        [&called]()
+        [&called](const EmptyInitializer&)
         {
             called = true;
             return armnn::IBackendInternalUniquePtr(nullptr);
@@ -67,7 +67,7 @@ BOOST_AUTO_TEST_CASE(TestRegistryHelper)
     // sanity check: the factory still not called
     BOOST_TEST(called == false);
 
-    factoryFunction();
+    factoryFunction(EmptyInitializer());
     BOOST_TEST(called == true);
 }
 
@@ -79,7 +79,7 @@ BOOST_AUTO_TEST_CASE(TestDirectCallToRegistry)
     bool called = false;
     BackendRegistryInstance().Register(
         "HelloWorld",
-        [&called]()
+        [&called](const EmptyInitializer&)
         {
             called = true;
             return armnn::IBackendInternalUniquePtr(nullptr);
@@ -94,7 +94,7 @@ BOOST_AUTO_TEST_CASE(TestDirectCallToRegistry)
     // sanity check: the factory still not called
     BOOST_TEST(called == false);
 
-    factoryFunction();
+    factoryFunction(EmptyInitializer());
     BOOST_TEST(called == true);
 }