COMPMID-1478: Stop relying on static default OpenCL objects in cl2.hpp

This causes problems when ACL is used as a shared library on Android.
Fixes some problems related to creation / destruction order between the Graph's CL backend and core / runtime

Change-Id: I716d63fd42f4586df1ffbb6fa97e4db06d3a781b
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/143228
Tested-by: Jenkins <bsgcomp@arm.com>
Reviewed-by: Michele DiGiorgio <michele.digiorgio@arm.com>
Reviewed-by: Gian Marco Iodice <gianmarco.iodice@arm.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/src/graph/backends/CL/CLDeviceBackend.cpp b/src/graph/backends/CL/CLDeviceBackend.cpp
index 6717f9f8e3..f35daf4ae5 100644
--- a/src/graph/backends/CL/CLDeviceBackend.cpp
+++ b/src/graph/backends/CL/CLDeviceBackend.cpp
@@ -63,7 +63,7 @@ bool file_exists(const std::string &filename)
 static detail::BackendRegistrar<CLDeviceBackend> CLDeviceBackend_registrar(Target::CL);
 
 CLDeviceBackend::CLDeviceBackend()
-    : _initialized(false), _tuner(), _allocator(nullptr), _tuner_file()
+    : _context_count(0), _tuner(), _allocator(nullptr), _tuner_file()
 {
 }
 
@@ -90,13 +90,23 @@ void CLDeviceBackend::initialize_backend()
     _allocator = support::cpp14::make_unique<CLBufferAllocator>();
 }
 
+void CLDeviceBackend::release_backend_context(GraphContext &ctx)
+{
+    ARM_COMPUTE_UNUSED(ctx);
+    _context_count--;
+    if(_context_count == 0) // No more context using the backend: free resources
+    {
+        _allocator = nullptr;
+    }
+}
+
 void CLDeviceBackend::setup_backend_context(GraphContext &ctx)
 {
     // Force backend initialization
-    if(!_initialized)
+    _context_count++;
+    if(_context_count == 1)
     {
         initialize_backend();
-        _initialized = true;
     }
 
     // Setup tuner