Does an object with a Bumped Diffuse Shader still perform all the normal calculation if its lightmapped with single lightmap mode?

A lightmap static object in single lightmap mode using the bumped diffuse shader would have no benefits from that extra shader work right? Does having it marked as lightmapped make it switch to a different more simple shader?

If its not the default behaviour is there a way I could do all my bakes with normal map shader, and once its baked use a simpler shader, then if i click bake again have it use the bumped shader again just for the bake?