[WIP] rust: enable for clangarm64

[dennisameling]

Related to #9046

I'm currently doing this work on an 8-core Intel i7-9700 with 32GB RAM instead of my Surface Pro X because of the project size and long build times

This is some first work to get Rust to compile for Windows arm64. This is a bit tricky as it's a massive project to build (and I ran into long path issues as well - moved the project to C:\_ for that). I learned the following about the Rust build process so far:

• A stage0 compiler is downloaded as indicated in mingw-w64-rust\src\rustc-1.57.0-src\src\stage0.json. In this case it downloads dist/2021-11-01/cargo-1.56.1-x86_64-pc-windows-gnu.tar.gz
• Rust will bootstrap the stage0 and stage1 compiler for x86_64-pc-windows-gnu
• Rust will try to use that compiler to target aarch64-pc-windows-gnu

The build currently fails at the last step where it tries to find crt2.o but fails. I added the COPYING {} TO {} manually as I only saw the panic show up without any further context or details.

COPYING C:/msys64/clang64/bin\llvm-dwp.exe TO C:\_\_\src\CLANG64\build\x86_64-pc-windows-gnu\stage2\lib\rustlib\x86_64-pc-windows-gnu\bin\rust-llvm-dwp.exe
  c Sysroot { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } } }
COPYING C:\_\_\src\CLANG64\build\x86_64-pc-windows-gnu\stage1-rustc\x86_64-pc-windows-gnu\release\rustc-main.exe TO C:\_\_\src\CLANG64\build\x86_64-pc-windows-gnu\stage2\bin\rustc.exe
< Assemble { target_compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } } }
> Std { target: TargetSelection { triple: "aarch64-pc-windows-gnu", file: None }, compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } } }
  > StartupObjects { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } }, target: TargetSelection { triple: "aarch64-pc-windows-gnu", file
    > Libdir { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } }, target: TargetSelection { triple: "aarch64-pc-windows-gnu", file: None
      c Sysroot { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } } }
    < Libdir { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } }, target: TargetSelection { triple: "aarch64-pc-windows-gnu", file: None
COPYING C:\_\_\src\CLANG64\build\aarch64-pc-windows-gnu\native\rtstartup\rsbegin.o TO C:\_\_\src\CLANG64\build\x86_64-pc-windows-gnu\stage2\lib\rustlib\aarch64-pc-windows-gnu\lib\rsbegin.o
COPYING C:\_\_\src\CLANG64\build\aarch64-pc-windows-gnu\native\rtstartup\rsend.o TO C:\_\_\src\CLANG64\build\x86_64-pc-windows-gnu\stage2\lib\rustlib\aarch64-pc-windows-gnu\lib\rsend.o
  < StartupObjects { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } }, target: TargetSelection { triple: "aarch64-pc-windows-gnu", file
  c Assemble { target_compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } } }
  c Libdir { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-gnu", file: None } }, target: TargetSelection { triple: "aarch64-pc-windows-gnu", file: None }
COPYING crt2.o TO C:\_\_\src\CLANG64\build\x86_64-pc-windows-gnu\stage2\lib\rustlib\aarch64-pc-windows-gnu\lib\self-contained\crt2.o
thread 'main' panicked at 'src.symlink_metadata() failed with Het systeem kan het opgegeven bestand niet vinden. (os error 2)', src\bootstrap\lib.rs:1326:24

[mati865]

You need working AArch64 toolchain so you cannot easily cross compile it using x86_64 system.
I have reverted some changes and made other and it failed after about 8 minutes with the same error as yours:

Details

$ git --no-pager diff
diff --git a/0009-windows-aarch64.patch b/0009-windows-aarch64.patch
index 3aac4bd..12e3110 100644
--- a/0009-windows-aarch64.patch
+++ b/0009-windows-aarch64.patch
@@ -1,7 +1,7 @@
 diff --unified --recursive --text --color --new-file rustc-1.57.0-src-orig/compiler/rustc_target/src/spec/aarch64_pc_windows_gnu.rs rustc-1.57.0-src/compiler/rustc_target/src/spec/aarch64_pc_windows_gnu.rs
 --- rustc-1.57.0-src-orig/compiler/rustc_target/src/spec/aarch64_pc_windows_gnu.rs     1970-01-01 01:00:00.000000000 +0100
 +++ rustc-1.57.0-src/compiler/rustc_target/src/spec/aarch64_pc_windows_gnu.rs  2021-12-27 13:57:28.788805700 +0100
-@@ -0,0 +1,19 @@
+@@ -0,0 +1,20 @@
 +use crate::spec::{LinkerFlavor, Target};
 +
 +pub fn target() -> Target {
@@ -10,7 +10,7 @@ diff --unified --recursive --text --color --new-file rustc-1.57.0-src-orig/compi
 +    let gcc_pre_link_args = base.pre_link_args.entry(LinkerFlavor::Gcc).or_default();
 +    gcc_pre_link_args.push("-march=armv8-a".to_string());
 +    base.max_atomic_width = Some(64);
-+    base.linker = Some("aarch64-w64-mingw32-gcc".to_string());
++    base.linker = Some("aarch64-w64-mingw32-clang".to_string());
 +
 +    Target {
 +        llvm_target: "aarch64-pc-windows-gnu".to_string(),
@@ -18,6 +18,7 @@ diff --unified --recursive --text --color --new-file rustc-1.57.0-src-orig/compi
 +        data_layout: "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
 +            .to_string(),
 +        arch: "aarch64".to_string(),
++        function_sections: true,
 +        options: base,
 +    }
 +}
@@ -40,7 +41,7 @@ diff --unified --recursive --text --color --new-file rustc-1.57.0-src-orig/src/b
      } else if target == "x86_64-pc-windows-gnu" {
          "x86_64-w64-mingw32-gcc.exe"
 +    } else if target == "aarch64-pc-windows-gnu" {
-+        "aarch64-w64-mingw32-gcc.exe"
++        "aarch64-w64-mingw32-clang.exe"
      } else {
          "gcc.exe"
      };
diff --git a/PKGBUILD b/PKGBUILD
index c3301cd..3e525de 100644
--- a/PKGBUILD
+++ b/PKGBUILD
@@ -46,7 +46,7 @@ sha256sums=('3546f9c3b91b1f8b8efd26c94d6b50312c08210397b4072ed2748e2bd4445c1a'
             'c4e5ffeef84296d39c3e3e8f807fc8b33ce786b1e4edb21eef26b053586aca27'
             '9e2e2eb9c0684f329b1ce6598fcb66727abf84121087b24670a9cfc44a514888'
             '29f84cb8e05ce304e102e28912a3b4464add406a8ec37a6c6d717b9b7d81b67b'
-            'dcf33adc873394444fa9ef4098cd73a66d26a60e1b5b946a88449bee4372faf7'
+            '2c54ed4058fafb2bd405d0933f3d9ea6b408ea903e46b89c2b910399ec6e0154'
             '8a9b997bfd8817a29ef5efb082e7dfb79d6c0d6566ec0a1a462b6b58b9e06d81')
 validpgpkeys=('108F66205EAEB0AAA8DD5E1C85AB96E6FA1BE5FE'  # Rust Language (Tag and Release Signing Key) <rust-key@rust-lang.org>
               '474E22316ABF4785A88C6E8EA2C794A986419D8A'  # Tom Stellard <tstellar@redhat.com>
@@ -98,9 +98,9 @@ build() {
     --sysconfdir=${MINGW_PREFIX}/etc \
     --localstatedir=${MINGW_PREFIX}/var/lib \
     --build=$OSTYPE \
-    --host=$OSTYPE \
+    --host=aarch64-pc-windows-gnu \
     --target=aarch64-pc-windows-gnu \
-    --release-channel=nightly \
+    --release-channel=stable \
     --enable-ninja \
     --enable-extended \
     --disable-codegen-tests \
@@ -112,7 +112,7 @@ build() {
   DEP_OPENSSL_ROOT=${MINGW_PREFIX} \
   DEP_Z_ROOT=${MINGW_PREFIX} \
   RUST_BACKTRACE=full \
-  ${MINGW_PREFIX}/bin/python ../${_realname}c-${pkgver}-src/x.py build --verbose --stage 2 --target aarch64-pc-windows-gnu
+  ${MINGW_PREFIX}/bin/python ../${_realname}c-${pkgver}-src/x.py build --verbose --stage 2

   #create the install at a temporary directory
   DEP_NGHTTP_ROOT=${MINGW_PREFIX} \

They won't help building this on x86_64 machine but with more tweaking (like adding both clang64/ and clangarm64/ to PATH) could work. That said I think it'd be easier and faster to work on bootstrap compiler outside of makepkg.

---

The build currently fails at the last step where it tries to find crt2.o but fails. I added the COPYING {} TO {} manually as I only saw the panic show up without any further context or details.

Actually the most helpful thing here is the backtrace printed at the end. Especially these 2 lines:

  16:     0x7ff6940dc961 - bootstrap::compile::copy_self_contained_objects::h1e457a866882eb6d
                               at D:\tmp\r\src\rustc-1.57.0-src\src\bootstrap\compile.rs:252:13

Here Rust asks C compiler where to find "crt2.o" and "dllcrt2.o", there is possibility this will work on AArch64 machine (on x86_64 you'd need cross compiler for AArch64) but I think it'll need patching.

[dennisameling]

I'll close this PR for now for the following reason:

That said I think it'd be easier and faster to work on bootstrap compiler outside of makepkg.

Following up in dennisameling/rust#1 instead. Have been making some progress there.

I'm not in a rush to get Rust to work as I've got all the dependencies I need now, but would like to slowly continue contributing in this area wherever possible.