OnMouseDown Stops working in mobile build when Scripting backend is converted to IL2CPP

Whenever i change Scripting Back end from Mono to IL2CPP My Game build doesn't respond to OnMouseDown Events it works fine when build with Mono. I have tried many things but nothing seems to work.
I Also get this warning : Game scripts or other custom code contains OnMouse_ event handlers. Presence of such handlers might impact performance on handheld devices.