Fix cycle with GraphToGPU.

theano/gpuarray/opt.py

@@ -376,9 +376,20 @@ class GraphToGPU(NavigatorOptimizer):
             if new_o.type != o.type:
                 assert isinstance(o.type, tensor.TensorType)
                 assert isinstance(new_o.type, GpuArrayType)
+                assert new_o.owner
+                # This condition is needed in the case one input is an
+                # output of the graph. Without this, it would
+                # introduce cycle as we don't replace correctly that
+                # case. It would also add extra transfer to/from the
+                # gpu.
+                if (isinstance(new_o.owner.op, GpuFromHost) and
+                        new_o.owner.inputs[0].type == o.type):
+                    new_o = new_o.owner.inputs[0]
+                else:
                     new_o = host_from_gpu(new_o)
             new_nodes.append(new_o)
-        fgraph.replace_all_validate(zip(fgraph.outputs, new_nodes))
+        fgraph.replace_all_validate(zip(fgraph.outputs, new_nodes),
+                                    reason=self.__class__.__name__)
 
         return (self, toposort_timing, time_opts, node_created, process_count)