C--

[Simon Peyton-Jones]

| I am trying to understand the role of cmm files in the current GHC
| compiler build process (I am guessing, they have replaced .hc files
| like PrimOps and AutoApply).

Yes, that's exactly right.

| They are compiled by the stage1 compiler. Is ability to compile cmm
| preserved in the compiler finally built at stage3 and installed?

Yes it is.

| What compiler flags are available for cmm files compilation? The
| User's guide says nothing specific. Are -E, -C, -S available (along
| with -c and -fvia-c seen in the nightly build log)?

I think -C and -S are.  I'm not sure about -E.  Try it!   You're right
that it ought to say. 

I suspect that the whole "compile Foo.cmm" route is ill-described in the
manual; even .cmm language (which is only a subset of C--) isn't
described.  Reason: we think of it as an internal thing.  But it's fine
for you to use it, and if it becomes useful to others we should document
it better.

If you can suggest specifically what would be helpful to you, and
specifically where in the manual, and better still provide some specific
words, I'll gladly paste them in.

Simon