{aarch64,x86_64}-*-windows-gnullvm: build host tools

compiler/rustc_llvm/build.rs

@@ -228,10 +228,10 @@ fn main() {
     let mut cmd = Command::new(&llvm_config);
     cmd.arg(llvm_link_arg).arg("--libs");
 
-    // Don't link system libs if cross-compiling unless targeting Windows.
+    // Don't link system libs if cross-compiling unless targeting Windows from Windows host.
     // On Windows system DLLs aren't linked directly, instead import libraries are used.
     // These import libraries are independent of the host.
-    if !is_crossed || target.contains("windows") {
+    if !is_crossed || target.contains("windows") && host.contains("windows") {
         cmd.arg("--system-libs");
     }
 

src/bootstrap/src/core/build_steps/compile.rs

@@ -1409,20 +1409,22 @@ fn rustc_llvm_env(builder: &Builder<'_>, cargo: &mut Cargo, target: TargetSelect
         cargo.env("LLVM_LINKER_FLAGS", llvm_linker_flags);
     }
 
-    // Building with a static libstdc++ is only supported on linux right now,
+    // Building with a static libstdc++ is only supported on Linux and windows-gnu* right now,
     // not for MSVC or macOS
     if builder.config.llvm_static_stdcpp
         && !target.contains("freebsd")
         && !target.is_msvc()
         && !target.contains("apple")
         && !target.contains("solaris")
     {
+        let libstdcxx_name =
+            if target.contains("windows-gnullvm") { "libc++.a" } else { "libstdc++.a" };
         let file = compiler_file(
             builder,
             &builder.cxx(target).unwrap(),
             target,
             CLang::Cxx,
-            "libstdc++.a",
+            libstdcxx_name,
         );
         cargo.env("LLVM_STATIC_STDCPP", file);
     }

src/bootstrap/src/core/build_steps/dist.rs

@@ -1680,7 +1680,7 @@ impl Step for Extended {
             cmd.run(builder);
         }
 
-        if target.is_windows() {
+        if target.is_windows() && self.host.is_windows() {
             let exe = tmp.join("exe");
             let _ = fs::remove_dir_all(&exe);
 

src/bootstrap/src/core/build_steps/llvm.rs

@@ -285,7 +285,8 @@ impl Step for Llvm {
             LlvmBuildStatus::ShouldBuild(m) => m,
         };
 
-        if builder.llvm_link_shared() && target.is_windows() {
+        if builder.llvm_link_shared() && target.is_windows() && !target.ends_with("windows-gnullvm")
+        {
             panic!("shared linking to LLVM is not currently supported on {}", target.triple);
         }
 

src/ci/docker/host-x86_64/dist-various-1/Dockerfile

@@ -114,9 +114,6 @@ ENV TARGETS=$TARGETS,armv7r-none-eabi
 ENV TARGETS=$TARGETS,armv7r-none-eabihf
 ENV TARGETS=$TARGETS,thumbv7neon-unknown-linux-gnueabihf
 ENV TARGETS=$TARGETS,armv7a-none-eabi
-ENV TARGETS=$TARGETS,aarch64-pc-windows-gnullvm
-ENV TARGETS=$TARGETS,i686-pc-windows-gnullvm
-ENV TARGETS=$TARGETS,x86_64-pc-windows-gnullvm
 
 ENV CFLAGS_armv5te_unknown_linux_musleabi="-march=armv5te -marm -mfloat-abi=soft" \
     CFLAGS_arm_unknown_linux_musleabi="-march=armv6 -marm" \
@@ -148,10 +145,7 @@ ENV CFLAGS_armv5te_unknown_linux_musleabi="-march=armv5te -marm -mfloat-abi=soft
     CC_riscv64imac_unknown_none_elf=riscv64-unknown-elf-gcc \
     CFLAGS_riscv64imac_unknown_none_elf=-march=rv64imac -mabi=lp64 \
     CC_riscv64gc_unknown_none_elf=riscv64-unknown-elf-gcc \
-    CFLAGS_riscv64gc_unknown_none_elf=-march=rv64gc -mabi=lp64 \
-    CC_aarch64_pc_windows_gnullvm=aarch64-w64-mingw32-clang \
-    CC_i686_pc_windows_gnullvm=i686-w64-mingw32-clang \
-    CC_x86_64_pc_windows_gnullvm=x86_64-w64-mingw32-clang
+    CFLAGS_riscv64gc_unknown_none_elf=-march=rv64gc -mabi=lp64
 
 ENV RUST_CONFIGURE_ARGS \
       --musl-root-armv5te=/musl-armv5te \

src/ci/docker/host-x86_64/dist-windows-gnullvm/Dockerfile

@@ -0,0 +1,51 @@
+FROM ubuntu:22.04
+
+WORKDIR /build
+
+ARG DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    ca-certificates \
+    cmake \
+    curl \
+    g++ \
+    git \
+    make \
+    ninja-build \
+    python3 \
+    xz-utils
+
+COPY host-x86_64/dist-windows-gnullvm/install-llvm-mingw.sh /build
+RUN ./install-llvm-mingw.sh
+
+COPY scripts/sccache.sh /scripts/
+RUN sh /scripts/sccache.sh
+
+ENV CC_aarch64_pc_windows_gnullvm=aarch64-w64-mingw32-clang \
+    CXX_aarch64_pc_windows_gnullvm=aarch64-w64-mingw32-clang++ \
+    CC_i686_pc_windows_gnullvm=i686-w64-mingw32-clang \
+    CC_x86_64_pc_windows_gnullvm=x86_64-w64-mingw32-clang \
+    CXX_x86_64_pc_windows_gnullvm=x86_64-w64-mingw32-clang++
+
+ENV HOSTS=aarch64-pc-windows-gnullvm,x86_64-pc-windows-gnullvm
+ENV TARGETS=aarch64-pc-windows-gnullvm,i686-pc-windows-gnullvm,x86_64-pc-windows-gnullvm
+
+# We are bootstrapping this target and cannot use previously built artifacts.
+# Without this option Clang is given `"-I/checkout/obj/build/aarch64-pc-windows-gnullvm/ci-llvm/include"`
+# despite no such directory existing:
+# ❯ ls obj/dist-windows-gnullvm/build/aarch64-pc-windows-gnullvm/ -1
+#  llvm
+#  stage2
+ENV NO_DOWNLOAD_CI_LLVM 1
+
+ENV RUST_CONFIGURE_ARGS \
+    --enable-extended \
+    --enable-profiler \
+    --enable-sanitizers \
+    --disable-docs \
+    --set llvm.download-ci-llvm=false \
+    --set rust.llvm-tools=false
+# LLVM cross tools are not installed into expected location so copying fails.
+# Probably will solve itself when building from Windows.
+# --enable-full-tools \
+
+ENV SCRIPT python3 ../x.py dist --host $HOSTS --target $TARGETS

src/ci/docker/host-x86_64/dist-windows-gnullvm/install-llvm-mingw.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+set -ex
+
+release_date=20250430
+archive=llvm-mingw-${release_date}-ucrt-ubuntu-22.04-x86_64.tar.xz
+curl -L https://github.com/mstorsjo/llvm-mingw/releases/download/${release_date}/${archive} | \
+tar --extract --xz --strip 1 --directory /usr/local
+
+# https://github.com/mstorsjo/llvm-mingw/issues/493
+for arch in aarch64 x86_64; do
+    ln -s $arch-w64-windows-gnu.cfg /usr/local/bin/$arch-pc-windows-gnu.cfg
+done