GHC Standalone backend

Here you will find a fork of GHC where we plan on implementing a backend that will allow compiling haskell for bear metal programming. There will be no RTS or OS dependance and we hope to target much more than just x86. There are three motivations for this project

1. To bring haskell to embedded hardware in order to gain greater software safety for all systems. Many embedded computers are used all over and are used in many places where humans interact with machines. It seems wrong that there are no good type safe, pure languages available.
2. We wish to try out some ideas to extend the IO monad.
3. We want to eventually build an entire operating system purely in haskell

IO Proposal

The proposal is that we introduce a type class called Hardware that encapsulates, you guessed it... hardware!

{-# LANGUAGE FunctionalDependencies #-}

class (Monad h) => Harware h e | h -> e where
	iomap :: e -> h a -> IO a

iomap allows you to access some IO on the computer using a specific monad that encapsulates that hardware within the IO monad. So an example would be just memory. e here would be a tuple that defines a segment of memory and type h a = Vector Byte -> (a, Vector Byte). So iomap (0,256) would give us direct access the the memory in the range 0 - 256.

As an example, say we were on a system that had a terminal attached. We would write ascii bytes from address 0xB800 and they would appear on the screen. The terminal is 480x640 giving us 307,200 bytes max that we could write. We could do the following hello world program:

module Main where

import Data.Char (Ord)

-- Fill just makes sure the vector is the correct length
setText :: Int -> String -> Mem ()
setText offset s m = ((), m // (zip [offset..] $ map (toByte . ord) s))

seg = (0xB800, 0xB800 + 307200 - 1)

main = iomap seg (return "Hello World" >>= setText 0)

The code assumes vectors of the specification described here.

But it isn't just memory mapped IO, we could easily make an instance of Hardware that encapsulated GPIO pins. In the next example, we assume that someone has made a GPIO instance that represent's the pins as a large tuple of bytes:

{-# LANGUAGE PatternSynonyms #-}

 module Main where

 pattern LEDs x y z = (... x, _, _, y, z, _ , ...) -- Tuple representing the pins

 -- This code assumes that type GPIO a = (pin1,..., pinN) -> (a, (pin1,..., pinN))

 rotate :: GPIO ()
 rotate (LEDs x y z) = ((), LEDs y z x)

 initState :: GPIO ()
 initState (LEDs _ _ _) = ((),LEDs 1 0 0)

 loop = rotate >> sleep 0.5 >> loop

 main = do
 	setPinOut $ Pin 12
 	setPinOut $ Pin 15
 	setPinOut $ Pin 16
 	iomap () (initState >> loop)

GHC's Readme

The Glasgow Haskell Compiler

This is the source tree for GHC, a compiler and interactive environment for the Haskell functional programming language.

For more information, visit GHC's web site.

Information for developers of GHC can be found on the GHC issue tracker.

Getting the Source

There are two ways to get a source tree:

1. Download source tarballs

   Download the GHC source distribution:

   ghc-<version>-src.tar.xz
   

   which contains GHC itself and the "boot" libraries.

2. Check out the source code from git

   $ git clone --recursive [email protected]:ghc/ghc.git
   

   Note: cloning GHC from Github requires a special setup. See Getting a GHC repository from Github.

See the GHC team's working conventions regarding how to contribute a patch to GHC. First time contributors are encouraged to get started by just sending a Merge Request.

Building & Installing

For full information on building GHC, see the GHC Building Guide. Here follows a summary - if you get into trouble, the Building Guide has all the answers.

Before building GHC you may need to install some other tools and libraries. See, Setting up your system for building GHC.

NB. In particular, you need GHC installed in order to build GHC, because the compiler is itself written in Haskell. You also need Happy, Alex, and Cabal. For instructions on how to port GHC to a new platform, see the GHC Building Guide.

For building library documentation, you'll need Haddock. To build the compiler documentation, you need Sphinx and Xelatex (only for PDF output).

Quick start: the following gives you a default build:

$ ./boot
$ ./configure
$ make         # can also say 'make -jX' for X number of jobs
$ make install

On Windows, you need an extra repository containing some build tools. These can be downloaded for you by configure. This only needs to be done once by running:

$ ./configure --enable-tarballs-autodownload

(NB: Do you have multiple cores? Be sure to tell that to make! This can save you hours of build time depending on your system configuration, and is almost always a win regardless of how many cores you have. As a simple rule, you should have about N+1 jobs, where N is the amount of cores you have.)

The ./boot step is only necessary if this is a tree checked out from git. For source distributions downloaded from GHC's web site, this step has already been performed.

These steps give you the default build, which includes everything optimised and built in various ways (eg. profiling libs are built). It can take a long time. To customise the build, see the file HACKING.md.

Filing bugs and feature requests

If you've encountered what you believe is a bug in GHC, or you'd like to propose a feature request, please let us know! Submit an issue and we'll be sure to look into it. Remember: Filing a bug is the best way to make sure your issue isn't lost over time, so please feel free.

If you're an active user of GHC, you may also be interested in joining the glasgow-haskell-users mailing list, where developers and GHC users discuss various topics and hang out.

Hacking & Developing GHC

Once you've filed a bug, maybe you'd like to fix it yourself? That would be great, and we'd surely love your company! If you're looking to hack on GHC, check out the guidelines in the HACKING.md file in this directory - they'll get you up to speed quickly.

Contributors & Acknowledgements

GHC in its current form wouldn't exist without the hard work of its many contributors. Over time, it has grown to include the efforts and research of many institutions, highly talented people, and groups from around the world. We'd like to thank them all, and invite you to join!