Sometimes we add flags that are for experimentation or development purposes and not intended for user consumption, and these tend not to be added to the User's Guide. I suspect many of the flags you mention fall into this category. I suggest for these we have a specific comment in the source "developer use only; undocumented" so that we know they don't need to go in the User's Guide. I don't like that policy. What if some of the mentioned flags could be useful for my development work but I have no idea how to use these flags because they are not documented? I think we should have these documented as well, possibly with a note saying that this is experimental/unstable.
isn't -ddump-simpl-phases useful? what's the other way to do that? I'll reply in a thread started by Johan.
Janek