GHC whole program compiler project

The project consists of GHC-WPC and the corresponding External STG IR and tooling.

GHC-WPC is an extended GHC that exports the STG IR (.modpak) for the compiled modules and linker metadata (.ghc_stgapp) at application link time.

The external-stg-compiler package should be compiled with GHC-WPC but the other packages i.e. external-stg compiles with vanilla GHC also.

Presentation video

• Why and How the External STG Interpreter is Useful (slides) (demo code)

Readings

• Introducing GHC whole program compiler (GHC-WPC)
• GHC-WPC thread on ghc-devs mailing list
• External STG Interpreter

External STG tools (Ext-STG)

• gen-exe main compiler driver, it produces executable from .ghc_stgapp files.
• gen-obj compiles STG IR files .o_stgbin to object code .o. (gen-exe calls it)
• ext-stg CLI tool for external STG IR, it can pretty print .o_stgbin files.

Sample applications for GHC-WPC

There is a set of prepared applications in the ghc-wpc-sample-programs repository that you can compile easily to try out GHC-WPC.

Why?

• to make it easy to develop new backends for GHC without extending Cabal with new targets
• to facilitate compiler/PL research that needs real world programs to analyse
• to allow whole program analysis (new insights might be adopted to incremental compilers)
• to escape from GHC codebase to the mainstream Haskell UX/DX that allows to use any library
• to allow program observation with arbitrary precision
• to make it easy to focus on the compiler backend development without hacking GHC
• to allow other compilers to target GHC/STG and the feature rich RTS

Usage

You'll need 13GB of free space (Sorry)

If you change the External STG IR, then GHC-WPC must be recompiled.

0. Install (exact version):

   • GHC 8.8.3
   • happy 1.19.12
   • alex 3.2.5

1. Clone this repository.

   git clone --recursive git@github.com:grin-compiler/ghc-whole-program-compiler-project.git
   

   If you did non-recursive cloning (when the ghc-wpc folder is empty) then you'll need to init submodules

   git submodule update --init --recursive
   

2. Install modpak tooling

   (cd mod-pak ; stack install)
   

3. Compile GHC-WPC in ./ghc-wpc folder with Hadrian (see ghc.dev for details).

   cd ghc-wpc
   ./boot
   ./configure
   hadrian/build-stack -j
   

   IMPORTANT: use hadrian/build-stack

4. At this point you have a working GHC-WPC.
   The next steps are about the compilation of GHC-WPC tooling and the usage of GHC-WPC.

5. Go back to the repository top folder and set the path to the local GHC-WPC build in the corresponding part of ./stack.yaml. change the following line to your GHC-WPC build path:

   extra-path:
     - /home/csaba/haskell/grin-compiler/ghc-whole-program-compiler-project/ghc-wpc/_build/stage1/bin
   

   i.e. set the USER and PROJECT part properly (./stack.yaml line 32)

   extra-path:
     - /home/USER/PROJECT/ghc-whole-program-compiler-project/ghc-wpc/_build/stage1/bin
   

6. Install the external stg tooling with the following commands:

   stack --stack-root `pwd`/.stack-root install
   

   NOTE: the stack root is set to the local folder to prevent spamming the global stack sandbox.

7. Use gen-exe and ext-stg from terminal. (it should be in PATH due to the stack install)

TODO

Ext-STG IR

• export IdInfo (without it gen-exe compiles -O0 executables)

UnZip with Zstd support

The .modpak and .fullpak files use Zstd compression method that was introduced in the Zip 6.3.8 standard in 2020.
The GHC-WPC tooling can handle Zstd zip files out of the box.
But if you'd like to unpack the .modpak and .fullpak files manually then you'll need an unzip version with Zstd support.
https://github.com/csabahruska/unzip-zstd