GHC core plugins

[Max Bolingbroke]

2010/1/27 José Pedro Magalhães <jpm at cs.uu.nl>:
> Alright, ticket created: http://hackage.haskell.org/trac/ghc/ticket/3843
>
> In any case, for now I am willing to hard-code a new core-to-core pass on
> the compiler. Any pointers for where I have to look at?

I recommend you look at compiler/simplCore/CSE.lhs. It is a simple
example of a core-to-core pass.

However, in short you'll need to:
1) Create a function which implements your core to core pass, of a
type such as [CoreBind] -> [CoreBind]
 *) If that function lives in a new module, edit ghc.cabal.in to tell
the build system about the module
2) Add a constructor to the CoreToDo data type in
compiler/simplCore/CoreMonad.lhs
3) Add a case for it to the coreDumpFlag and Outputable instance
4) Add that pass to the list returned by getCoreToDo in CoreMonad. The
order of the list is the order the passes will be run in.
 *) If you want the pass to be under the control of a new flag, you'll
need to add a new dynflag - add a constructor to the DOpt data type in
compiler/main/DynFlags.lhs, and add something to build that
constructor to one of the lists that get fed to the command line
handling code in the same module. It should be fairly obvious how to
do this.
5) Add a handler for the new constructor to
compiler/simplCore/SimplCore.lhs, in the doCorePass function which
calls into the core pass function you wrote

Hope that helps,
Max