GHC whole program compiler project

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

The wpc-plugin is a compiler plugin for GHC 9.10 or newer. It exports the STG IR (.modpak) for the compiled modules and linker metadata (.ghc_stgapp) at application link time.

Presentation video

• Why a GHC Whole Program Compiler Mode Would Be Useful (slides)
• 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.

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

Build

external stg tooling

stack install

wpc-plugin

1. Install zip-cmd, a simple CLI for the zip package

   cabal install zip-cmd
   

2. Compile the wpc-plugin The wpc-plugin has a speparate stack.yaml because it uses the plugin API of GHC 9.10.3.

   cd wpc-plugin
   stack build
   

3. Find the built libwpc-plugin.[so|dylib|dll]

   ln -s `find ~+ -type f -name 'libwpc-plugin.so' -o -name 'libwpc-plugin.dylib' -o -name 'libwpc-plugin.dll' | head -1`
   

Usage

It is required to use GHC 9.10.3.

cabal

Add the following lines to your project's cabal.project:

package *
  ghc-options:
    -fplugin-trustworthy
    -fplugin-library=PATH_TO/libwpc-plugin.so;wpc-plugin-unit;WPC.Plugin;[]

stack

Add the following lines to your project's stack.yaml:

apply-ghc-options: everything
ghc-options:
  "$everything":
      -fplugin-trustworthy
      -fplugin-library=PATH_TO/libwpc-plugin.so;wpc-plugin-unit;WPC.Plugin;[]

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