RFC: Recommend and enable using Wild rather than Mold on Linux for local builds

.cargo/ci-config.toml

@@ -10,3 +10,15 @@
 # Here, we opted to use `[target.'cfg(all())']` instead of `[build]` because `[target.'**']` is guaranteed to be cumulative.
 [target.'cfg(all())']
 rustflags = ["-D", "warnings"]
+
+# Use Mold on Linux, because it's faster than GNU ld and LLD.
+#
+# We no longer set this in the default `config.toml` so that developers can opt in to Wild, which
+# is faster than Mold, in their own ~/.cargo/config.toml.
+[target.x86_64-unknown-linux-gnu]
+linker = "clang"
+rustflags = ["-C", "link-arg=-fuse-ld=mold"]
+
+[target.aarch64-unknown-linux-gnu]
+linker = "clang"
+rustflags = ["-C", "link-arg=-fuse-ld=mold"]

.cargo/config.toml

@@ -5,14 +5,6 @@ rustflags = ["-C", "symbol-mangling-version=v0", "--cfg", "tokio_unstable"]
 [alias]
 xtask = "run --package xtask --"
 
-[target.x86_64-unknown-linux-gnu]
-linker = "clang"
-rustflags = ["-C", "link-arg=-fuse-ld=mold"]
-
-[target.aarch64-unknown-linux-gnu]
-linker = "clang"
-rustflags = ["-C", "link-arg=-fuse-ld=mold"]
-
 [target.'cfg(target_os = "windows")']
 rustflags = [
     "--cfg",

docs/src/development/linux.md

@@ -20,6 +20,33 @@ Clone down the [Zed repository](https://github.com/zed-industries/zed).
 
 If you are looking to develop Zed collaboration features using a local collaboration server, please see: [Local Collaboration](./local-collaboration.md) docs.
 
+### Linkers {#linker}
+
+On Linux, Rust's default linker is [LLVM's `lld`](https://blog.rust-lang.org/2025/09/18/Rust-1.90.0/). Alternative linkers, especially [Wild](https://github.com/davidlattimore/wild) and [Mold](https://github.com/rui314/mold) can significantly improve clean and incremental build time.
+
+At present Zed uses Mold in CI because it's more mature. For local development Wild is recommended because it's 5-20% faster than Mold.
+
+These linkers can be installed with `script/install-mold` and `script/install-wild`.
+
+To use Wild as your default, add these lines to your `~/.cargo/config.toml`:
+
+```toml
+[target.x86_64-unknown-linux-gnu]
+linker = "clang"
+rustflags = ["-C", "link-arg=--ld-path=wild"]
+
+[target.aarch64-unknown-linux-gnu]
+linker = "clang"
+rustflags = ["-C", "link-arg=--ld-path=wild"]
+```
+
+To use Mold as your default:
+
+```toml
+[target.'cfg(target_os = "linux")']
+rustflags = ["-C", "link-arg=-fuse-ld=mold"]
+```
+
 ## Building from source
 
 Once the dependencies are installed, you can build Zed using [Cargo](https://doc.rust-lang.org/cargo/).

script/install-wild

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+# Install wild-linker official binaries from GitHub Releases.
+
+set -euo pipefail
+
+WILD_VERSION="${WILD_VERSION:-${1:-0.5.0}}"
+if [ "$(uname -s)" != "Linux" ]; then
+    echo "Error: This script is intended for Linux systems only."
+    exit 1
+elif [ -z "$WILD_VERSION" ]; then
+    echo "Usage: $0 [version]"
+    exit 1
+elif which -s wild && wild --version | grep -Fq "$WILD_VERSION" ; then
+    echo "Warning: existing wild $WILD_VERSION found at $(which wild). Skipping installation."
+    exit 0
+fi
+
+if [ "$(whoami)" = root ]; then SUDO=; else SUDO="$(command -v sudo || command -v doas || true)"; fi
+
+ARCH="$(uname -m)"
+WILD_REPO="${WILD_REPO:-https://github.com/davidlattimore/wild}"
+WILD_PACKAGE="wild-linker-${ARCH}-unknown-linux-gnu"
+WILD_URL="${WILD_URL:-$WILD_REPO}/releases/download/$WILD_VERSION/${WILD_PACKAGE}.tar.xz"
+
+echo "Downloading from $WILD_URL"
+curl -fsSL --output - "$WILD_URL" \
+    | $SUDO tar -C /usr/local/bin --strip-components=1 --no-overwrite-dir -xJf - \
+    "wild-linker-${ARCH}-unknown-linux-gnu/wild"

script/linux

@@ -11,12 +11,23 @@ fi
 function finalize {
   # after packages install (curl, etc), get the rust toolchain
   which rustup > /dev/null 2>&1 || curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
-  # verify the mold situation
-  if ! command -v mold >/dev/null 2>&1; then
-    echo "Warning: Mold binaries are unavailable on your system." >&2
-    echo "    Builds will be slower without mold. Try: script/install-mold" >&2
-  fi
-  echo "Finished installing Linux dependencies with script/linux"
+  cat <<EOF
+Note: It's recommended to install and configure Wild or Mold for faster builds.
+      Run script/install-wild or script/install-mold.
+      Then add these lines to your ~/.cargo/config.toml:
+
+[target.x86_64-unknown-linux-gnu]
+linker = "clang"
+rustflags = ["-C", "link-arg=--ld-path=wild"]
+
+[target.aarch64-unknown-linux-gnu]
+linker = "clang"
+rustflags = ["-C", "link-arg=--ld-path=wild"]
+
+
+
+Finished installing Linux dependencies with script/linux
+EOF
 }
 
 # Ubuntu, Debian, Mint, Kali, Pop!_OS, Raspbian, etc.