Enable building Dex with Nix

Author: sharadmv

README.md

@@ -85,6 +85,28 @@ manually. This will be ignored by git.
 
 This should work out of the box with Emacs' `lsp-haskell` package.
 
+### Building with Nix
+
+[Nix](https://nixos.org/) is a functional package manager and build system.
+
+To build with vanilla Nix:
+```bash
+$ nix-build
+```
+
+To build with flakes-enabled Nix:
+```bash
+$ nix build .#dex
+```
+The resulting `dex` binary should be in `result/bin/dex`.
+
+For development purposes, you can use a Nix environment with
+```bash
+$ nix-shell
+$ nix develop  # With flakes
+```
+and use `make` to use Stack to build Dex.
+
 ## Running
 
   * Traditional REPL: `dex repl`

default.nix

@@ -0,0 +1,72 @@
+{ pkgs ? import <nixpkgs> {},
+  llvm-hs-src ? pkgs.fetchFromGitHub {
+    owner = "llvm-hs";
+    repo = "llvm-hs";
+    rev = "llvm-12";
+    sha256 = "IG4Mh89bY+PtBJtzlXKYsPljfHP7OSQk03pV6fSmdRY=";
+  },
+  cudaPackage ? pkgs.cudaPackages.cudatoolkit_11,
+  cuda ? false,
+  optimized ? true,
+  live ? true,
+}:
+let
+  llvm-hs-pure = pkgs.haskellPackages.callCabal2nix "llvm-hs-pure" "${llvm-hs-src}/llvm-hs-pure" {
+  };
+  llvm-hs = (pkgs.haskellPackages.callCabal2nix "llvm-hs" "${llvm-hs-src}/llvm-hs" {
+    inherit llvm-hs-pure;
+  }).overrideAttrs (oldAttrs: rec {
+    buildInputs = oldAttrs.buildInputs ++ [
+      pkgs.llvm_12
+    ];
+  });
+  buildFlags = pkgs.lib.optionals optimized [
+    "-foptimized"
+  ] ++ pkgs.lib.optionals live [
+    "-flive"
+  ] ++ pkgs.lib.optionals cuda [
+    "-fcuda"
+    "--extra-include-dirs=${cudaPackage}/include"
+    "--extra-lib-dirs=${cudaPackage}/lib64/stubs"
+  ];
+  cxxFlags = [
+    "-fPIC"
+    "-std=c++11"
+    "-fno-exceptions"
+    "-fno-rtti"
+  ] ++ pkgs.lib.optional cuda "-DDEX_CUDA"
+    ++ pkgs.lib.optional live "-DDEX_LIVE";
+  buildRuntimeCommand =  ''
+      ${pkgs.clang_9}/bin/clang++ \
+      ${builtins.concatStringsSep " " cxxFlags} \
+      -c \
+      -emit-llvm  \
+      -I${pkgs.libpng}/include \
+      src/lib/dexrt.cpp  \
+      -o src/lib/dexrt.bc
+  '';
+in
+  # `callCabal2nix` converts `dex.cabal` into a Nix file and builds it.
+  # Before we do the Haskell build though, we need to first compile the Dex runtime
+  # so it's properly linked in when compiling Dex. Normally the makefile does this,
+  # so we instead sneak compiling the runtime in the configuration phase for the Haskell build.
+  (pkgs.haskellPackages.callCabal2nix "dex" ./. {
+    inherit llvm-hs;
+    inherit llvm-hs-pure;
+  }).overrideAttrs (attrs: {
+    configurePhase = ''
+    # Compile the Dex runtime
+    echo 'Compiling the Dex runtime...'
+    set -x
+    ${buildRuntimeCommand}
+    set +x
+    echo 'Done compiling the Dex runtime.'
+
+    # Run the Haskell configuration phase
+    ${attrs.configurePhase}
+    '';
+    configureFlags = builtins.concatStringsSep " " buildFlags;
+    buildInputs = attrs.buildInputs ++ (pkgs.lib.optional cuda
+      cudaPackage
+    );
+  })

flake.lock

@@ -0,0 +1,35 @@
+{
+  description = "Dex (named for \"index\") is a research language for typed, functional array processing.";
+
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    llvm-hs-src = {
+      url = "github:llvm-hs/llvm-hs/llvm-12";
+      flake = false;
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, llvm-hs-src }:
+    flake-utils.lib.eachDefaultSystem (system:
+    let
+      pkgs = (import nixpkgs {
+        inherit system;
+        config.allowUnfree = true; # Needed for CUDA
+      });
+    in rec {
+      packages.dex = (pkgs.callPackage ./. {
+        inherit pkgs;
+        inherit llvm-hs-src;
+      });
+      packages.dex-cuda = (pkgs.callPackage ./. {
+        inherit pkgs;
+        inherit llvm-hs-src;
+        withCudaSupport = true;
+      });
+      defaultPackage = packages.dex;
+
+      devShell = (import ./shell.nix {
+        inherit pkgs;
+      });
+    });
+  }

flake.nix

@@ -1,6 +1,6 @@
 # Set shell to bash to resolve symbolic links when looking up
 # executables, to support user-account installation of stack.
-SHELL=/bin/bash
+SHELL=/usr/bin/env bash
 
 STACK=$(shell command -v stack 2>/dev/null)
 ifeq (, $(STACK))

makefile

@@ -1,15 +1,16 @@
-{ nixpkgs ? import <nixpkgs> {} }:
-with nixpkgs;
-stdenv.mkDerivation {
+{ pkgs ? import <nixpkgs> {} }:
+pkgs.stdenv.mkDerivation {
   name = "dex";
-  buildInputs = [
+  buildInputs = with pkgs; [
     cabal-install
+    cacert
+    clang_12
+    git
     haskell.compiler.ghc884
-    llvm_9
-    clang_9
-    pkg-config
     libpng
-    git
-    cacert
+    llvm_12
+    pkg-config
+    stack
+    zlib
   ];
 }

shell.nix

@@ -20,3 +20,7 @@ extra-deps:
   - store-0.7.8@sha256:0b604101fd5053b6d7d56a4ef4c2addf97f4e08fe8cd06b87ef86f958afef3ae,8001
   - store-core-0.4.4.4@sha256:a19098ca8419ea4f6f387790e942a7a5d0acf62fe1beff7662f098cfb611334c,1430
   - th-utilities-0.2.4.1@sha256:b37d23c8bdabd678aee5a36dd4373049d4179e9a85f34eb437e9cd3f04f435ca,1869
+
+nix:
+  enable: false
+  packages: [ libpng llvm_12 pkg-config zlib ]