IVGCVSW-4212 Example of standalone dynamic reference backend

 * Add example to build dynamic reference backend
 * Add functions to clear dynamic backends
 * Fix the error when dynamic backend is not deregistered
 * Add DYARMNN_DYNAMIC_BACKEND_ENABLED to check disable empty
   dynamic backend when dynamic backend is enabled

Signed-off-by: Narumol Prangnawarat <narumol.prangnawarat@arm.com>
Change-Id: I1ef3a3f10ed6ca5ec18d0af04b007fc3bc71a3cb

3 files changed, 30 insertions, 2 deletions

diff --git a/src/armnn/BackendRegistry.cpp b/src/armnn/BackendRegistry.cpp
index 45f73b8daf..dc3e2bc254 100644
--- a/src/armnn/BackendRegistry.cpp
+++ b/src/armnn/BackendRegistry.cpp
@@ -27,6 +27,11 @@ void BackendRegistry::Register(const BackendId& id, BackendRegistry::FactoryFunc
     m_Factories[id] = factory;
 }
 
+void BackendRegistry::Deregister(const BackendId& id)
+{
+    m_Factories.erase(id);
+}
+
 bool BackendRegistry::IsBackendRegistered(const BackendId& id) const
 {
     return (m_Factories.find(id) != m_Factories.end());
diff --git a/src/armnn/DeviceSpec.hpp b/src/armnn/DeviceSpec.hpp
index 32264706fd..703a4b123f 100644
--- a/src/armnn/DeviceSpec.hpp
+++ b/src/armnn/DeviceSpec.hpp
@@ -24,14 +24,33 @@ public:
         return m_SupportedBackends;
     }
 
-    void AddSupportedBackends(const BackendIdSet& backendIds)
+    void AddSupportedBackends(const BackendIdSet& backendIds, bool isDynamic = false)
     {
         m_SupportedBackends.insert(backendIds.begin(), backendIds.end());
+        if (isDynamic)
+        {
+            m_DynamicBackends.insert(backendIds.begin(), backendIds.end());
+        }
+    }
+
+    void ClearDynamicBackends()
+    {
+        for (const auto& id : m_DynamicBackends)
+        {
+            m_SupportedBackends.erase(id);
+        }
+        m_DynamicBackends.clear();
+    }
+
+    const BackendIdSet& GetDynamicBackends() const
+    {
+        return m_DynamicBackends;
     }
 
 private:
     DeviceSpec() = delete;
     BackendIdSet m_SupportedBackends;
+    BackendIdSet m_DynamicBackends;
 };
 
 } // namespace armnn
diff --git a/src/armnn/Runtime.cpp b/src/armnn/Runtime.cpp
index 9b0ce1a345..4ad6fa59a0 100644
--- a/src/armnn/Runtime.cpp
+++ b/src/armnn/Runtime.cpp
@@ -214,6 +214,10 @@ Runtime::~Runtime()
                       << std::endl;
         }
     }
+
+    // Clear all dynamic backends.
+    DynamicBackendUtils::DeregisterDynamicBackends(m_DeviceSpec.GetDynamicBackends());
+    m_DeviceSpec.ClearDynamicBackends();
 }
 
 LoadedNetwork* Runtime::GetLoadedNetworkPtr(NetworkId networkId) const
@@ -273,7 +277,7 @@ void Runtime::LoadDynamicBackends(const std::string& overrideBackendPath)
     BackendIdSet registeredBackendIds = DynamicBackendUtils::RegisterDynamicBackends(m_DynamicBackends);
 
     // Add the registered dynamic backend ids to the list of supported backends
-    m_DeviceSpec.AddSupportedBackends(registeredBackendIds);
+    m_DeviceSpec.AddSupportedBackends(registeredBackendIds, true);
 }
 
 } // namespace armnn