Add LLVM based mingw-w64 targets

compiler/rustc_codegen_llvm/src/back/archive.rs

@@ -152,8 +152,10 @@ impl<'a> ArchiveBuilder<'a> for LlvmArchiveBuilder<'a> {
         };
 
         let target = &self.config.sess.target;
-        let mingw_gnu_toolchain =
+        let mingw_gnu_toolchain = target.vendor == "pc"
-            target.vendor == "pc" && target.os == "windows" && target.env == "gnu";
+            && target.os == "windows"
+            && target.env == "gnu"
+            && target.abi.is_empty();
 
         let import_name_and_ordinal_vector: Vec<(String, Option<u16>)> = dll_imports
             .iter()

compiler/rustc_llvm/build.rs

@@ -324,9 +324,10 @@ fn main() {
 
     let stdcppname = if target.contains("openbsd") {
         if target.contains("sparc64") { "estdc++" } else { "c++" }
-    } else if target.contains("freebsd") {
+    } else if target.contains("darwin")
-        "c++"
+        || target.contains("freebsd")
-    } else if target.contains("darwin") {
+        || target.contains("windows-gnullvm")
+    {
         "c++"
     } else if target.contains("netbsd") && llvm_static_stdcpp.is_some() {
         // NetBSD uses a separate library when relocation is required
@@ -365,7 +366,7 @@ fn main() {
 
     // Libstdc++ depends on pthread which Rust doesn't link on MinGW
     // since nothing else requires it.
-    if target.contains("windows-gnu") {
+    if target.ends_with("windows-gnu") {
         println!("cargo:rustc-link-lib=static:-bundle=pthread");
     }
 }

compiler/rustc_target/src/spec/aarch64_pc_windows_gnullvm.rs

@@ -0,0 +1,16 @@
+use crate::spec::Target;
+
+pub fn target() -> Target {
+    let mut base = super::windows_gnullvm_base::opts();
+    base.max_atomic_width = Some(64);
+    base.features = "+neon,+fp-armv8".into();
+    base.linker = Some("aarch64-w64-mingw32-clang".into());
+
+    Target {
+        llvm_target: "aarch64-pc-windows-gnu".into(),
+        pointer_width: 64,
+        data_layout: "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128".into(),
+        arch: "aarch64".into(),
+        options: base,
+    }
+}

compiler/rustc_target/src/spec/mod.rs

@@ -82,6 +82,7 @@ mod uefi_msvc_base;
 mod vxworks_base;
 mod wasm_base;
 mod windows_gnu_base;
+mod windows_gnullvm_base;
 mod windows_msvc_base;
 mod windows_uwp_gnu_base;
 mod windows_uwp_msvc_base;
@@ -939,6 +940,9 @@ supported_targets! {
     ("i686-uwp-windows-gnu", i686_uwp_windows_gnu),
     ("x86_64-uwp-windows-gnu", x86_64_uwp_windows_gnu),
 
+    ("aarch64-pc-windows-gnullvm", aarch64_pc_windows_gnullvm),
+    ("x86_64-pc-windows-gnullvm", x86_64_pc_windows_gnullvm),
+
     ("aarch64-pc-windows-msvc", aarch64_pc_windows_msvc),
     ("aarch64-uwp-windows-msvc", aarch64_uwp_windows_msvc),
     ("x86_64-pc-windows-msvc", x86_64_pc_windows_msvc),

compiler/rustc_target/src/spec/windows_gnullvm_base.rs

@@ -0,0 +1,52 @@
+use crate::spec::{cvs, LinkArgs, LinkerFlavor, TargetOptions};
+
+pub fn opts() -> TargetOptions {
+    let pre_link_args = LinkArgs::from([(
+        LinkerFlavor::Gcc,
+        vec![
+            // We cannot use `-nodefaultlibs` because compiler-rt has to be passed
+            // as a path since it's not added to linker search path by the default.
+            // There were attemts to make it behave like libgcc (so one can just use -l<name>)
+            // but LLVM maintainers rejected it: https://reviews.llvm.org/D51440
+            "-nolibc".into(),
+            "--unwindlib=none".into(),
+        ],
+    )]);
+    let late_link_args = LinkArgs::from([(
+        LinkerFlavor::Gcc,
+        // Order of `late_link_args*` does not matter with LLD.
+        vec![
+            "-lmingw32".into(),
+            "-lmingwex".into(),
+            "-lmsvcrt".into(),
+            "-lkernel32".into(),
+            "-luser32".into(),
+        ],
+    )]);
+
+    TargetOptions {
+        os: "windows".into(),
+        env: "gnu".into(),
+        vendor: "pc".into(),
+        abi: "llvm".into(),
+        linker: Some("clang".into()),
+        dynamic_linking: true,
+        executables: true,
+        dll_prefix: "".into(),
+        dll_suffix: ".dll".into(),
+        exe_suffix: ".exe".into(),
+        families: cvs!["windows"],
+        is_like_windows: true,
+        allows_weak_linkage: false,
+        pre_link_args,
+        late_link_args,
+        abi_return_struct_as_int: true,
+        emit_debug_gdb_scripts: false,
+        requires_uwtable: true,
+        eh_frame_header: false,
+        no_default_libraries: false,
+        has_thread_local: true,
+
+        ..Default::default()
+    }
+}

compiler/rustc_target/src/spec/x86_64_pc_windows_gnullvm.rs

@@ -0,0 +1,19 @@
+use crate::spec::{LinkerFlavor, Target};
+
+pub fn target() -> Target {
+    let mut base = super::windows_gnullvm_base::opts();
+    base.cpu = "x86-64".into();
+    let gcc_pre_link_args = base.pre_link_args.entry(LinkerFlavor::Gcc).or_default();
+    gcc_pre_link_args.push("-m64".into());
+    base.max_atomic_width = Some(64);
+    base.linker = Some("x86_64-w64-mingw32-clang".into());
+
+    Target {
+        llvm_target: "x86_64-pc-windows-gnu".into(),
+        pointer_width: 64,
+        data_layout: "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+            .into(),
+        arch: "x86_64".into(),
+        options: base,
+    }
+}

library/unwind/build.rs

@@ -36,7 +36,7 @@ fn main() {
         println!("cargo:rustc-link-lib=gcc_s");
     } else if target.contains("dragonfly") {
         println!("cargo:rustc-link-lib=gcc_pic");
-    } else if target.contains("pc-windows-gnu") {
+    } else if target.ends_with("pc-windows-gnu") {
         // This is handled in the target spec with late_link_args_[static|dynamic]
     } else if target.contains("uwp-windows-gnu") {
         println!("cargo:rustc-link-lib=unwind");

library/unwind/src/lib.rs

@@ -5,6 +5,7 @@
 #![feature(nll)]
 #![feature(staged_api)]
 #![feature(c_unwind)]
+#![feature(cfg_target_abi)]
 #![cfg_attr(not(target_env = "msvc"), feature(libc))]
 
 cfg_if::cfg_if! {
@@ -85,3 +86,7 @@ extern "C" {}
 #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))]
 #[link(name = "unwind", kind = "static", modifiers = "-bundle")]
 extern "C" {}
+
+#[cfg(all(target_os = "windows", target_env = "gnu", target_abi = "llvm"))]
+#[link(name = "unwind", kind = "static", modifiers = "-bundle")]
+extern "C" {}

src/bootstrap/compile.rs

@@ -175,6 +175,7 @@ fn copy_third_party_objects(
     }
 
     if target == "x86_64-fortanix-unknown-sgx"
+        || target.contains("pc-windows-gnullvm")
         || builder.config.llvm_libunwind == LlvmLibunwind::InTree
             && (target.contains("linux") || target.contains("fuchsia"))
     {
@@ -246,7 +247,7 @@ fn copy_self_contained_objects(
                 DependencyType::TargetSelfContained,
             );
         }
-    } else if target.contains("windows-gnu") {
+    } else if target.ends_with("windows-gnu") {
         for obj in ["crt2.o", "dllcrt2.o"].iter() {
             let src = compiler_file(builder, builder.cc(target), target, CLang::C, obj);
             let target = libdir_self_contained.join(obj);
@@ -477,7 +478,7 @@ impl Step for StartupObjects {
     fn run(self, builder: &Builder<'_>) -> Vec<(PathBuf, DependencyType)> {
         let for_compiler = self.compiler;
         let target = self.target;
-        if !target.contains("windows-gnu") {
+        if !target.ends_with("windows-gnu") {
             return vec![];
         }
 

src/bootstrap/dist.rs

@@ -285,7 +285,7 @@ impl Step for Mingw {
     /// without any extra installed software (e.g., we bundle gcc, libraries, etc).
     fn run(self, builder: &Builder<'_>) -> Option<GeneratedTarball> {
         let host = self.host;
-        if !host.contains("pc-windows-gnu") {
+        if !host.ends_with("pc-windows-gnu") {
             return None;
         }
 
@@ -341,7 +341,7 @@ impl Step for Rustc {
         // anything requiring us to distribute a license, but it's likely the
         // install will *also* include the rust-mingw package, which also needs
         // licenses, so to be safe we just include it here in all MinGW packages.
-        if host.contains("pc-windows-gnu") {
+        if host.ends_with("pc-windows-gnu") {
             make_win_dist(tarball.image_dir(), &tmpdir(builder), host, builder);
             tarball.add_dir(builder.src.join("src/etc/third-party"), "share/doc");
         }
@@ -1352,7 +1352,7 @@ impl Step for Extended {
         tarballs.push(builder.ensure(Rustc { compiler: builder.compiler(stage, target) }));
         tarballs.push(builder.ensure(Std { compiler, target }).expect("missing std"));
 
-        if target.contains("windows-gnu") {
+        if target.ends_with("windows-gnu") {
             tarballs.push(builder.ensure(Mingw { host: target }).expect("missing mingw"));
         }
 
@@ -1522,7 +1522,7 @@ impl Step for Extended {
                     prepare(tool);
                 }
             }
-            if target.contains("windows-gnu") {
+            if target.ends_with("windows-gnu") {
                 prepare("rust-mingw");
             }
 
@@ -1711,7 +1711,7 @@ impl Step for Extended {
                     .arg("-t")
                     .arg(etc.join("msi/remove-duplicates.xsl")),
             );
-            if target.contains("windows-gnu") {
+            if target.ends_with("windows-gnu") {
                 builder.run(
                     Command::new(&heat)
                         .current_dir(&exe)
@@ -1760,7 +1760,7 @@ impl Step for Extended {
                 if built_tools.contains("miri") {
                     cmd.arg("-dMiriDir=miri");
                 }
-                if target.contains("windows-gnu") {
+                if target.ends_with("windows-gnu") {
                     cmd.arg("-dGccDir=rust-mingw");
                 }
                 builder.run(&mut cmd);
@@ -1787,7 +1787,7 @@ impl Step for Extended {
             }
             candle("AnalysisGroup.wxs".as_ref());
 
-            if target.contains("windows-gnu") {
+            if target.ends_with("windows-gnu") {
                 candle("GccGroup.wxs".as_ref());
             }
 
@@ -1829,7 +1829,7 @@ impl Step for Extended {
                 cmd.arg("MiriGroup.wixobj");
             }
 
-            if target.contains("windows-gnu") {
+            if target.ends_with("windows-gnu") {
                 cmd.arg("GccGroup.wixobj");
             }
             // ICE57 wrongly complains about the shortcuts
@@ -1859,7 +1859,9 @@ fn add_env(builder: &Builder<'_>, cmd: &mut Command, target: TargetSelection) {
         .env("CFG_BUILD", target.triple)
         .env("CFG_CHANNEL", &builder.config.channel);
 
-    if target.contains("windows-gnu") {
+    if target.contains("windows-gnullvm") {
+        cmd.env("CFG_MINGW", "1").env("CFG_ABI", "LLVM");
+    } else if target.contains("windows-gnu") {
         cmd.env("CFG_MINGW", "1").env("CFG_ABI", "GNU");
     } else {
         cmd.env("CFG_MINGW", "0").env("CFG_ABI", "MSVC");

src/bootstrap/native.rs

@@ -1372,6 +1372,10 @@ impl Step for Libunwind {
                 cfg.define("__LIBUNWIND_IS_NATIVE_ONLY", None);
                 cfg.define("NDEBUG", None);
             }
+            if self.target.contains("windows") {
+                cfg.define("_LIBUNWIND_HIDE_SYMBOLS", "1");
+                cfg.define("_LIBUNWIND_IS_NATIVE_ONLY", "1");
+            }
         }
 
         cc_cfg.compiler(builder.cc(self.target));

src/doc/rustc/src/SUMMARY.md

@@ -21,6 +21,7 @@
     - [m68k-unknown-linux-gnu](platform-support/m68k-unknown-linux-gnu.md)
     - [mips64-openwrt-linux-musl](platform-support/mips64-openwrt-linux-musl.md)
     - [nvptx64-nvidia-cuda](platform-support/nvptx64-nvidia-cuda.md)
+    - [*-pc-windows-gnullvm](platform-support/pc-windows-gnullvm.md)
     - [*-unknown-openbsd](platform-support/openbsd.md)
     - [wasm64-unknown-unknown](platform-support/wasm64-unknown-unknown.md)
     - [x86_64-unknown-none](platform-support/x86_64-unknown-none.md)

src/doc/rustc/src/platform-support.md

@@ -208,6 +208,7 @@ target | std | host | notes
 `aarch64-apple-ios-macabi` | ? |  | Apple Catalyst on ARM64
 `aarch64-apple-tvos` | * |  | ARM64 tvOS
 [`aarch64-kmc-solid_asp3`](platform-support/kmc-solid.md) | ✓ |  | ARM64 SOLID with TOPPERS/ASP3
+[`aarch64-pc-windows-gnullvm`](platform-support/pc-windows-gnullvm.md) | ✓ | ✓ |
 `aarch64-unknown-freebsd` | ✓ | ✓ | ARM64 FreeBSD
 `aarch64-unknown-hermit` | ✓ |  | ARM64 HermitCore
 `aarch64-unknown-uefi` | * |  | ARM64 UEFI
@@ -288,6 +289,7 @@ target | std | host | notes
 [`wasm64-unknown-unknown`](platform-support/wasm64-unknown-unknown.md) | ? |  | WebAssembly
 `x86_64-apple-ios-macabi` | ✓ |  | Apple Catalyst on x86_64
 `x86_64-apple-tvos` | * | | x86 64-bit tvOS
+[`x86_64-pc-windows-gnullvm`](platform-support/pc-windows-gnullvm.md) | ✓ | ✓ |
 `x86_64-pc-windows-msvc` | * |  | 64-bit Windows XP support
 `x86_64-sun-solaris` | ? |  | Deprecated target for 64-bit Solaris 10/11, illumos
 `x86_64-unknown-dragonfly` | ✓ | ✓ | 64-bit DragonFlyBSD

src/doc/rustc/src/platform-support/pc-windows-gnullvm.md

@@ -0,0 +1,48 @@
+# \*-pc-windows-gnullvm
+
+**Tier: 3**
+
+Windows targets similar to `*-pc-windows-gnu` but using UCRT as the runtime and various LLVM tools/libraries instead of GCC/Binutils.
+
+Target triples avaiable so far:
+- `aarch64-pc-windows-gnullvm`
+- `x86_64-pc-windows-gnullvm`
+
+## Target maintainers
+
+- [@mati865](https://github.com/mati865)
+
+## Requirements
+
+The easiest way to obtain these targets is cross-compilation but native build from `x86_64-pc-windows-gnu` is possible with few hacks which I don't recommend.
+Std support is expected to be on pair with `*-pc-windows-gnu`.
+
+Binaries for this target should be at least on pair with `*-pc-windows-gnu` in terms of requirements and functionality.
+
+Those targets follow Windows calling convention for `extern "C"`.
+
+Like with any other Windows target created binaries are in PE format.
+
+## Building the target
+
+For cross-compilation I recommend using [llvm-mingw](https://github.com/mstorsjo/llvm-mingw) toolchain, one change that seems necessary beside configuring corss compilers is disabling experimental `m86k` target. Otherwise LLVM build fails with `multiple definition ...` errors.
+Native bootstrapping builds require rather fragile hacks until host artifacts are avaiable so I won't describe them here.
+
+## Building Rust programs
+
+Rust does not yet ship pre-compiled artifacts for this target. To compile for
+this target, you will either need to build Rust with the target enabled (see
+"Building the target" above), or build your own copy of `core` by using
+`build-std` or similar.
+
+## Testing
+
+Created binaries work fine on Windows or Wine using native hardware. Testing AArch64 on x86_64 is problematic though and requires spending some time with QEMU.
+Once these targets bootstrap themselves on native hardware they should pass Rust testsuite.
+
+## Cross-compilation toolchains and C code
+
+Compatible C code can be built with Clang's `aarch64-pc-windows-gnu` and `x86_64-pc-windows-gnu` targets as long as LLVM based C toolchains are used.
+Those include:
+- [llvm-mingw](https://github.com/mstorsjo/llvm-mingw)
+- [MSYS2 with CLANG* environment](https://www.msys2.org/docs/environments)