CI: Add native Windows arm64 job/package

Author: kinke

.github/actions/1-setup/action.yml

@@ -59,8 +59,12 @@ runs:
       run: |
         set -eux
         cd ..
+        suffix='win64'
+        if [[ '${{ inputs.arch }}' == arm64 ]]; then
+          suffix='woa64'
+        fi
         curl -fL --retry 3 --max-time 300 -o clang.exe \
-          https://github.com/llvm/llvm-project/releases/download/llvmorg-20.1.3/LLVM-20.1.3-win64.exe
+          https://github.com/llvm/llvm-project/releases/download/llvmorg-20.1.3/LLVM-20.1.3-$suffix.exe
         ./clang.exe //S # double-slash for bash
         rm clang.exe
         # C:\Program Files\LLVM\bin should already be in PATH
@@ -163,7 +167,9 @@ runs:
         cd ..
 
         url='https://curl.se/windows/latest.cgi?p=win64-mingw.zip'
-        if [[ '${{ inputs.arch }}' == x86 ]]; then
+        if [[ '${{ inputs.arch }}' == arm64 ]]; then
+          url='https://curl.se/windows/latest.cgi?p=win64a-mingw.zip'
+        elif [[ '${{ inputs.arch }}' == x86 ]]; then
           url='https://curl.se/windows/latest.cgi?p=win32-mingw.zip'
         fi
 

.github/actions/5-install/action.yml

@@ -66,6 +66,11 @@ runs:
 
         cp libcurl/ldc2/* installed/bin/
 
+        if [[ '${{ inputs.arch }}' == arm64 ]]; then
+          echo "No MinGW-based libraries available for arm64 yet."
+          exit 0
+        fi
+
         curl -fL --retry 3 --max-time 60 -o mingw-w64-libs.7z \
           https://github.com/ldc-developers/mingw-w64-libs/releases/download/v8.0.0/mingw-w64-libs-v8.0.0.7z
         mkdir mingw-w64-libs

.github/actions/merge-windows/action.yml

@@ -67,6 +67,7 @@ runs:
         set PATH=%CD%\ldc2-multilib\lib32;%PATH%
         ldc2-multilib\bin\ldc2 -link-defaultlib-shared -m32 -run hello.d || exit /b
 
+    # TODO
     # preliminary arm64 cross-compilation support
     - name: Install ninja v1.12.1
       uses: Ahajha/gha-setup-ninja@69595b0cf872acdad8ce599142fbdc88724b9a2b

.github/workflows/main.yml

@@ -101,6 +101,16 @@ jobs:
               -DEXTRA_CXXFLAGS=-flto=full
             with_pgo: true
 
+          - job_name: Windows arm64
+            os: windows-11-arm
+            arch: arm64
+            base_cmake_flags: >-
+              -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded
+            #extra_cmake_flags: >-
+            #  "-DD_COMPILER_FLAGS=-O -flto=full -defaultlib=phobos2-ldc-lto,druntime-ldc-lto"
+            #  -DEXTRA_CXXFLAGS=-flto=full
+            #with_pgo: true
+
           - job_name: Windows x86
             os: windows-2025
             arch: x86

CMakeLists.txt

@@ -195,7 +195,10 @@ if(NOT MSVC_IDE)
 endif()
 
 if(MSVC)
-    if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+    if($ENV{VSCMD_ARG_TGT_ARCH} STREQUAL "arm64")
+        message(STATUS "Let D host compiler output arm64 object files")
+        append("-mtriple=aarch64-windows-msvc" DFLAGS_BASE)
+    elseif(CMAKE_SIZEOF_VOID_P EQUAL 8)
         message(STATUS "Let D host compiler output 64-bit object files")
         append("-m64" DFLAGS_BASE)
     else()
@@ -300,7 +303,9 @@ endif()
 if(MSVC)
     separate_arguments(LLVM_LDFLAGS WINDOWS_COMMAND "${LLVM_LDFLAGS}")
     if(NOT MSVC_IDE) # apparently not needed for VS (and spaces in path are problematic)
-        if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+        if($ENV{VSCMD_ARG_TGT_ARCH} STREQUAL "arm64")
+            list(APPEND LLVM_LDFLAGS "$ENV{VSINSTALLDIR}DIA SDK\\lib\\arm64\\diaguids.lib")
+        elseif(CMAKE_SIZEOF_VOID_P EQUAL 8)
             list(APPEND LLVM_LDFLAGS "$ENV{VSINSTALLDIR}DIA SDK\\lib\\amd64\\diaguids.lib")
         else()
             list(APPEND LLVM_LDFLAGS "$ENV{VSINSTALLDIR}DIA SDK\\lib\\diaguids.lib")
@@ -895,7 +900,9 @@ if (LDC_INSTALL_LLVM_RUNTIME_LIBS)
         copy_compilerrt_lib("libclang_rt.xray-profiling${compilerrt_suffix}.a" "libldc_rt.xray-profiling.a" FALSE)
     elseif(WIN32)
         set(compilerrt_arch_suffix "x86_64")
-        if(CMAKE_SIZEOF_VOID_P EQUAL 4)
+        if($ENV{VSCMD_ARG_TGT_ARCH} STREQUAL "arm64")
+            set(compilerrt_arch_suffix "aarch64")
+        elseif(CMAKE_SIZEOF_VOID_P EQUAL 4)
             set(compilerrt_arch_suffix "i386")
         endif()
         if(LDC_LLVM_VER LESS 2000)