From e134f4888b19ac993bf1d9fc365cbf5c729ab630 Mon Sep 17 00:00:00 2001
From: David Mak <chmakac@connect.ust.hk>
Date: Thu, 13 Jun 2024 15:13:44 +0800
Subject: [PATCH] [meta] Add option to use mold as linker

---
 README.md | 13 +++++++++++++
 flake.nix | 15 ++++++++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index 40b0d077..38fab1a8 100644
--- a/README.md
+++ b/README.md
@@ -60,3 +60,16 @@ Several things to note:
 
 - If `cargo fmt` or `cargo clippy` returns an error, the pre-commit hook will fail. You should fix all errors before trying to commit again.
 - If `cargo fmt` reformats some files, the pre-commit hook will also fail. You should review the changes and, if satisfied, try to commit again.
+
+### Use Mold Linker
+
+The [Mold linker](https://github.com/rui314/mold) is available when using the Nix Flakes system, and can be enabled by adding the following to `.cargo/config.toml`:
+
+```
+[target.x86_64-unknown-linux-gnu]
+rustflags = ["-C", "link-arg=-fuse-ld=mold"]
+```
+
+Replace `x86_64-unknown-linux-gnu` with the target triple of your development platform.
+
+**Note: The use of Mold linker is experimental and should be used for development purposes only.**
diff --git a/flake.nix b/flake.nix
index a20e1f12..e833d8c8 100644
--- a/flake.nix
+++ b/flake.nix
@@ -41,9 +41,9 @@
               lockFile = ./Cargo.lock;
             };
             passthru.cargoLock = cargoLock;
-            nativeBuildInputs = [ pkgs.python3 (pkgs.wrapClangMulti pkgs.llvmPackages_14.clang) llvm-tools-irrt pkgs.llvmPackages_14.llvm.out llvm-nac3 ];
-            buildInputs = [ pkgs.python3 llvm-nac3 ];
-            checkInputs = [ (pkgs.python3.withPackages(ps: [ ps.numpy ps.scipy ])) ];
+            nativeBuildInputs = [ pkgs.python3 pkgs.mold-wrapped (pkgs.wrapClangMulti pkgs.llvmPackages_14.clang) llvm-tools-irrt pkgs.llvmPackages_14.llvm.out llvm-nac3 ];
+            buildInputs = [ pkgs.python3 pkgs.mold-wrapped llvm-nac3 ];
+            checkInputs = [ (pkgs.python3.withPackages(ps: [ ps.numpy ps.scipy ])) pkgs.mold-wrapped ];
             checkPhase =
               ''
               echo "Checking nac3standalone demos..."
@@ -68,6 +68,7 @@
               mkdir -p $standalone/bin
               cp target/x86_64-unknown-linux-gnu/release/nac3standalone $standalone/bin
               '';
+            stdenv = [ pkgs.stdenvAdapters.useMoldLinker pkgs.stdenv ];
           }
         );
         python3-mimalloc = pkgs.python3 // rec {
@@ -86,7 +87,7 @@
             src = self;
             inherit (nac3artiq) cargoLock;
             nativeBuildInputs = [ pkgs.python3 packages.x86_64-linux.llvm-tools-irrt llvm-nac3-instrumented ];
-            buildInputs = [ pkgs.python3 llvm-nac3-instrumented ];
+            buildInputs = [ pkgs.python3 pkgs.mold-wrapped llvm-nac3-instrumented ];
             cargoBuildFlags = [ "--package" "nac3artiq" "--features" "init-llvm-profile" ];
             doCheck = false;
             configurePhase =
@@ -99,6 +100,7 @@
               mkdir -p $TARGET_DIR
               cp target/x86_64-unknown-linux-gnu/release/libnac3artiq.so $TARGET_DIR/nac3artiq.so
               '';
+            stdenv = [ pkgs.stdenvAdapters.useMoldLinker pkgs.stdenv ];
           }
         );
         nac3artiq-profile = pkgs.stdenvNoCC.mkDerivation {
@@ -148,7 +150,7 @@
             src = self;
             inherit (nac3artiq) cargoLock;
             nativeBuildInputs = [ pkgs.python3 packages.x86_64-linux.llvm-tools-irrt llvm-nac3-pgo ];
-            buildInputs = [ pkgs.python3 llvm-nac3-pgo ];
+            buildInputs = [ pkgs.python3 pkgs.mold-wrapped llvm-nac3-pgo ];
             cargoBuildFlags = [ "--package" "nac3artiq" ];
             cargoTestFlags = [ "--package" "nac3ast" "--package" "nac3parser" "--package" "nac3core" "--package" "nac3artiq" ];
             installPhase =
@@ -157,6 +159,7 @@
               mkdir -p $TARGET_DIR
               cp target/x86_64-unknown-linux-gnu/release/libnac3artiq.so $TARGET_DIR/nac3artiq.so
               '';
+            stdenv = [ pkgs.stdenvAdapters.useMoldLinker pkgs.stdenv ];
           }
         );
       };
@@ -172,6 +175,7 @@
           packages.x86_64-linux.llvm-tools-irrt
           cargo
           rustc
+          mold-wrapped
           # runtime dependencies
           lld_14                           # for running kernels on the host
           (packages.x86_64-linux.python3-mimalloc.withPackages(ps: [ ps.numpy ps.scipy ]))
@@ -186,6 +190,7 @@
           export DEMO_LINALG_STUB=${packages.x86_64-linux.demo-linalg-stub}/lib/liblinalg.a
           export DEMO_LINALG_STUB32=${packages.x86_64-linux.demo-linalg-stub32}/lib/liblinalg.a
           '';
+        stdenv = [ pkgs.stdenvAdapters.useMoldLinker pkgs.stdenv ];
       };
       devShells.x86_64-linux.msys2 = pkgs.mkShell {
         name = "nac3-dev-shell-msys2";