DRAFT: Add an aarch64-msvc build running on ARM64 Windows

Author: dpaoliello

.github/workflows/ci.yml

@@ -134,6 +134,9 @@ jobs:
       - name: show the current environment
         run: src/ci/scripts/dump-environment.sh
 
+      - name: install rust
+        run: src/ci/scripts/install-rust.sh
+
       - name: install awscli
         run: src/ci/scripts/install-awscli.sh
 
@@ -212,8 +215,7 @@ jobs:
           fi
           exit ${STATUS}
         env:
-          AWS_ACCESS_KEY_ID: ${{ env.CACHES_AWS_ACCESS_KEY_ID }}
-          AWS_SECRET_ACCESS_KEY: ${{ secrets[format('AWS_SECRET_ACCESS_KEY_{0}', env.CACHES_AWS_ACCESS_KEY_ID)] }}
+          SCCACHE_S3_NO_CREDENTIALS: 1
 
       - name: create github artifacts
         run: src/ci/scripts/create-doc-artifacts.sh

src/ci/github-actions/jobs.yml

@@ -47,6 +47,10 @@ runners:
     os: windows-2025-8core-32gb
     <<: *base-job
 
+  - &job-windows-aarch64
+    os: windows-11-arm
+    <<: *base-job
+
   - &job-aarch64-linux
     # Free some disk space to avoid running out of space during the build.
     free_disk: true
@@ -100,18 +104,11 @@ envs:
 # These jobs automatically inherit envs.pr, to avoid repeating
 # it in each job definition.
 pr:
-  - name: mingw-check
-    <<: *job-linux-4c
-  - name: mingw-check-tidy
-    continue_on_error: true
-    <<: *job-linux-4c
-  - name: x86_64-gnu-llvm-19
+  - name: aarch64-msvc
     env:
-      ENABLE_GCC_CODEGEN: "1"
-      DOCKER_SCRIPT: x86_64-gnu-llvm.sh
-    <<: *job-linux-16c
-  - name: x86_64-gnu-tools
-    <<: *job-linux-16c
+      RUST_CONFIGURE_ARGS: --build=aarch64-pc-windows-msvc
+      SCRIPT: make ci-msvc
+    <<: *job-windows-aarch64
 
 # Jobs that run when you perform a try build (@bors try)
 # These jobs automatically inherit envs.try, to avoid repeating

src/ci/scripts/install-clang.sh

@@ -11,7 +11,7 @@ source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
 
 # Update both macOS's and Windows's tarballs when bumping the version here.
 # Try to keep this in sync with src/ci/docker/host-x86_64/dist-x86_64-linux/build-clang.sh
-LLVM_VERSION="18.1.4"
+LLVM_VERSION="20.1.3"
 
 if isMacOS; then
     # FIXME: This is the latest pre-built version of LLVM that's available for
@@ -54,11 +54,21 @@ elif isWindows && ! isKnownToBeMingwBuild; then
     # don't want to run the installer directly; extracting it is more reliable
     # in CI environments.
 
+    if [[ "${CI_JOB_NAME}" = *aarch64* ]]; then
+        suffix=woa64
+
+        # On Arm64, the Ring crate requires that Clang be on the PATH.
+        # https://github.com/briansmith/ring/blob/main/BUILDING.md
+        ciCommandAddPath "$(cygpath -m "$(pwd)/clang-rust/bin")"
+    else
+        suffix=win64
+    fi
+
     mkdir -p citools/clang-rust
     cd citools
-    retry curl -f "${MIRRORS_BASE}/LLVM-${LLVM_VERSION}-win64.exe" \
-        -o "LLVM-${LLVM_VERSION}-win64.exe"
-    7z x -oclang-rust/ "LLVM-${LLVM_VERSION}-win64.exe"
+    retry curl -f "${MIRRORS_BASE}/LLVM-${LLVM_VERSION}-${suffix}.exe" \
+        -o "LLVM-${LLVM_VERSION}-${suffix}.exe"
+    7z x -oclang-rust/ "LLVM-${LLVM_VERSION}-${suffix}.exe"
     ciCommandSetEnv RUST_CONFIGURE_ARGS \
         "${RUST_CONFIGURE_ARGS} --set llvm.clang-cl=$(pwd)/clang-rust/bin/clang-cl.exe"
 

src/ci/scripts/install-mingw.sh

@@ -42,5 +42,5 @@ if isWindows && isKnownToBeMingwBuild; then
 
     curl -o mingw.7z "${MIRRORS_BASE}/${mingw_archive}"
     7z x -y mingw.7z > /dev/null
-    ciCommandAddPath "$(pwd)/${mingw_dir}/bin"
+    ciCommandAddPath "$(cygpath -m "$(pwd)/${mingw_dir}/bin")"
 fi

src/ci/scripts/install-ninja.sh

@@ -12,7 +12,7 @@ if isWindows; then
     7z x -oninja ninja.zip
     rm ninja.zip
     ciCommandSetEnv "RUST_CONFIGURE_ARGS" "${RUST_CONFIGURE_ARGS} --enable-ninja"
-    ciCommandAddPath "$(pwd)/ninja"
+    ciCommandAddPath "$(cygpath -m "$(pwd)/ninja")"
 elif isMacOS; then
     brew install ninja
 fi

src/ci/scripts/install-rust.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+# For mingw builds use a vendored mingw.
+
+set -euo pipefail
+IFS=$'\n\t'
+
+source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
+
+if isWindows; then
+    case "${CI_JOB_NAME}" in
+        *aarch64*)
+            curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | \
+            sh -s -- -y -q --default-host aarch64-pc-windows-msvc
+            ciCommandAddPath "${USERPROFILE}/.cargo/bin"
+            ;;
+    esac
+fi

src/ci/scripts/install-sccache.sh

@@ -15,7 +15,7 @@ elif isWindows; then
     mkdir -p sccache
     curl -fo sccache/sccache.exe \
       "${MIRRORS_BASE}/2025-02-24-sccache-v0.10.0-x86_64-pc-windows-msvc.exe"
-    ciCommandAddPath "$(pwd)/sccache"
+    ciCommandAddPath "$(cygpath -m "$(pwd)/sccache")"
 fi
 
 # FIXME: we should probably install sccache outside the containers and then

src/doc/nomicon

@@ -42,9 +42,13 @@ macro_rules! dump_and_die {
         // there, even on i686-pc-windows-msvc. We do the best we can in
         // rust-lang/rust to test it as well, but sometimes we just gotta keep
         // landing PRs.
+        //
+        // aarch64-msvc is broken as its backtraces are truncated.
+        // See https://github.com/rust-lang/rust/issues/140489
         if cfg!(any(target_os = "android",
                     all(target_os = "linux", target_arch = "arm"),
                     all(target_env = "msvc", target_arch = "x86"),
+                    all(target_env = "msvc", target_arch = "aarch64"),
                     target_os = "freebsd",
                     target_os = "dragonfly",
                     target_os = "openbsd")) {