[CMake][WinMsvc] Replace MSVC_BASE/WINSDK_BASE with LLVM_WINSYSROOT

[ychen]

Summary

• Using LLVM_WINSYSROOT would pick up DIA SDK path automatically, otherwise llvm-pdbutil has no DIA support.
• Add MSVC_VER to specify VC tools version.
• Make MSVC_VER/WINSDK_VER optional. If not specified, use the highest version number like the driver does.

[thakis]

/winsysroot is somewhat new, but I suppose that's fine (?)

Looks fine to me (haven't tried it though). The only real question below is where and how winsysroot gets added as flag :)

llvm/cmake/platforms/WinMsvc.cmake

212

clang does this internally if they're not defined. Maybe add -vctoolsversion only if MSVC_VER is defined, and -winsdkversion only if WINSDK_VER is defined?

217

MSVC_VER and WINSDK_VER are optional, so you probably should only check for the sysroot

221

given that this is only set to check for existence, maybe this variable (and the check against it) isn't needed?

223

same here

266

Do you want to add /winsysroot down here too? Or how is that flag getting added?

288

FWIW in Chromium we build our lld-link against libxml2 (with almost everything disabled) these days, and it can do /manifest handling without mt.exe if build that way.

[ychen]

Thanks for the review!

llvm/cmake/platforms/WinMsvc.cmake

212

yeah, considered that. Later I found out I still need MSVC_VER and WINSDK_VER to specify libpath for the linker. Guess we need to wait until lld-link accepts /winsysroot...

217

same. Optional for the user, still need it to specify linker libpath.

266

https://github.com/llvm/llvm-project/blob/4cc514579f467db51907567b305f21b0607b27d1/llvm/cmake/modules/HandleLLVMOptions.cmake#L463

288

Thanks for the info. I'll try removing it locally.

[ychen]

llvm/cmake/platforms/WinMsvc.cmake

288

Oh, okay. It seems LLVM Windows release build does not link libxml2 yet. Is it possible to upstream your code (https://chromium.googlesource.com/chromium/src/+/66ff126e39334b72ec6f23b6d28a60e7efbbc019/tools/clang/scripts/build.py#281) to llvm/utils/release/build_llvm_package.bat so the release lld-link works with /manifest?

[thakis]

Lg for now; once lld-link supports the flag we can make it nicer :)

llvm/cmake/platforms/WinMsvc.cmake

212

Someone over here is working on that :)

288

I wasn't aware of that script. That seems like a good thing to do, yes.

[smeenai]

llvm/cmake/platforms/WinMsvc.cmake

266

Not all parts of LLVM's build call HandleLLVMOptions, e.g. compiler-rt doesn't. We should add the flag explicitly to handle those cases as well (and I don't think having it specified twice should cause any harm). I'll put up a patch.

[vvavrychuk]

In case of Visual Studio 2019/2022, Windows SDK are installed outside of MSVS directory

C:\Program Files (x86)\Windows Kits\10

[smeenai]

In D117852#4164315, @vvavrychuk wrote:

In case of Visual Studio 2019/2022, Windows SDK are installed outside of MSVS directory

C:\Program Files (x86)\Windows Kits\10

I believe that was the case for earlier versions as well (at least 2015 and 2017), but this is intended for cross-compilation, so the idea was that you'd arrange the SDK and VC directories in the layout expected by /winsysroot.

llvm/cmake/platforms/WinMsvc.cmake

 # Cross toolchain configuration for using clang-cl on non-Windows hosts to
 # target MSVC.
 #
 # Usage:
 # cmake -G Ninja
 #    -DCMAKE_TOOLCHAIN_FILE=/path/to/this/file
 #    -DHOST_ARCH=[aarch64|arm64|armv7|arm|i686|x86|x86_64|x64]
 #    -DLLVM_NATIVE_TOOLCHAIN=/path/to/llvm/installation
-#    -DMSVC_BASE=/path/to/MSVC/system/libraries/and/includes
-#    -DWINSDK_BASE=/path/to/windows-sdk
+#    -DLLVM_WINSYSROOT=/path/to/win/sysroot
+#    -DMSVC_VER=vc tools version folder name
 #    -DWINSDK_VER=windows sdk version folder name
 #
 # HOST_ARCH:
-#    The architecture to build for.
+#   The architecture to build for.
 #
 # LLVM_NATIVE_TOOLCHAIN:
 #   *Absolute path* to a folder containing the toolchain which will be used to
 #   build.  At a minimum, this folder should have a bin directory with a
 #   copy of clang-cl, clang, clang++, and lld-link, as well as a lib directory
 #   containing clang's system resource directory.
 #
-# MSVC_BASE:
-#   *Absolute path* to the folder containing MSVC headers and system libraries.
-#   The layout of the folder matches that which is intalled by MSVC 2017 on
-#   Windows, and should look like this:
+# MSVC_VER/WINSDK_VER:
+#   (Optional) if not specified, highest version number is used if any.
 #
-# ${MSVC_BASE}
+# LLVM_WINSYSROOT and MSVC_VER work together to define a folder layout that 
+# containing MSVC headers and system libraries. The layout of the folder
+# matches that which is intalled by MSVC 2017 on Windows, and should look like
+# this:
+#
+# ${LLVM_WINSYSROOT}/VC/Tools/MSVC/${MSVC_VER}/
 #   include
 #     vector
 #     stdint.h
 #     etc...
 #   lib
 #     x64
 #       libcmt.lib
 #       msvcrt.lib
 #       etc...
 #     x86
 #       libcmt.lib
 #       msvcrt.lib
 #       etc...
 #
 # For versions of MSVC < 2017, or where you have a hermetic toolchain in a
 # custom format, you must use symlinks or restructure it to look like the above.
 #
-# WINSDK_BASE:
-#   Together with WINSDK_VER, determines the location of Windows SDK headers
-#   and libraries.
-#
-# WINSDK_VER:
-#   Together with WINSDK_BASE, determines the locations of Windows SDK headers
-#   and libraries.
-#
-# WINSDK_BASE and WINSDK_VER work together to define a folder layout that matches
-# that of the Windows SDK installation on a standard Windows machine.  It should
-# match the layout described below.
+# LLVM_WINSYSROOT and WINSDK_VER work together to define a folder layout that
+# matches that of the Windows SDK installation on a standard Windows machine.
+# It should match the layout described below.
 #
 # Note that if you install Windows SDK to a windows machine and simply copy the
 # files, it will already be in the correct layout.
 #
-# ${WINSDK_BASE}
+# ${LLVM_WINSYSROOT}/Windows Kits/10/
 #   Include
 #     ${WINSDK_VER}
 #       shared
 #       ucrt
 #       um
 #         windows.h
 #         etc...
 #   Lib
if(NOT library STREQUAL lowercase_ext_symlink_name AND
       execute_process(COMMAND "${CMAKE_COMMAND}"
                               -E create_symlink
                               "${winsdk_um_lib_dir}/${library}"
                               "${output_dir}/${lowercase_ext_symlink_name}")
     endif()
   endforeach()
 endfunction()
 
+function(get_highest_version the_dir the_ver)
+  file(GLOB entries LIST_DIRECTORIES true RELATIVE "${the_dir}" "${the_dir}/[0-9.]*")
+  foreach(entry ${entries})
+    if(IS_DIRECTORY "${the_dir}/${entry}")
+      set(${the_ver} "${entry}" PARENT_SCOPE)
+    endif()
+  endforeach()
+endfunction()
+
 set(CMAKE_SYSTEM_NAME Windows)
 set(CMAKE_SYSTEM_VERSION 10.0)
 set(CMAKE_SYSTEM_PROCESSOR AMD64)
 
 init_user_prop(HOST_ARCH)
 init_user_prop(LLVM_NATIVE_TOOLCHAIN)
-init_user_prop(MSVC_BASE)
-init_user_prop(WINSDK_BASE)
+init_user_prop(LLVM_WINSYSROOT)
+init_user_prop(MSVC_VER)
 init_user_prop(WINSDK_VER)
 
 if(NOT HOST_ARCH)
   set(HOST_ARCH x86_64)
 endif()
 if(HOST_ARCH STREQUAL "aarch64" OR HOST_ARCH STREQUAL "arm64")
   set(TRIPLE_ARCH "aarch64")
   set(WINSDK_ARCH "arm64")
 elseif(HOST_ARCH STREQUAL "armv7" OR HOST_ARCH STREQUAL "arm")
   set(TRIPLE_ARCH "armv7")
   set(WINSDK_ARCH "arm")
 elseif(HOST_ARCH STREQUAL "i686" OR HOST_ARCH STREQUAL "x86")
   set(TRIPLE_ARCH "i686")
   set(WINSDK_ARCH "x86")
 elseif(HOST_ARCH STREQUAL "x86_64" OR HOST_ARCH STREQUAL "x64")
   set(TRIPLE_ARCH "x86_64")
   set(WINSDK_ARCH "x64")
 else()
   message(SEND_ERROR "Unknown host architecture ${HOST_ARCH}. Must be aarch64 (or arm64), armv7 (or arm), i686 (or x86), or x86_64 (or x64).")
 endif()
 
-set(MSVC_INCLUDE "${MSVC_BASE}/include")
-set(ATLMFC_INCLUDE "${MSVC_BASE}/atlmfc/include")
-set(MSVC_LIB "${MSVC_BASE}/lib")
-set(ATLMFC_LIB "${MSVC_BASE}/atlmfc/lib")
-set(WINSDK_INCLUDE "${WINSDK_BASE}/Include/${WINSDK_VER}")
-set(WINSDK_LIB "${WINSDK_BASE}/Lib/${WINSDK_VER}")
-
 # Do some sanity checking to make sure we can find a native toolchain and
 # that the Windows SDK / MSVC STL directories look kosher.
 if(NOT EXISTS "${LLVM_NATIVE_TOOLCHAIN}/bin/clang-cl" OR
    NOT EXISTS "${LLVM_NATIVE_TOOLCHAIN}/bin/lld-link")
   message(SEND_ERROR
           "LLVM_NATIVE_TOOLCHAIN folder '${LLVM_NATIVE_TOOLCHAIN}' does not "
           "point to a valid directory containing bin/clang-cl and bin/lld-link "
           "binaries")
 endif()
 
-if(NOT EXISTS "${MSVC_BASE}" OR
-   NOT EXISTS "${MSVC_INCLUDE}" OR
-   NOT EXISTS "${MSVC_LIB}")
-  message(SEND_ERROR
-          "CMake variable MSVC_BASE must point to a folder containing MSVC "
-          "system headers and libraries")
+if (NOT MSVC_VER)
+  get_highest_version("${LLVM_WINSYSROOT}/VC/Tools/MSVC" MSVC_VER)
+endif()
+
+if (NOT WINSDK_VER)
+  get_highest_version("${LLVM_WINSYSROOT}/Windows Kits/10/Include" WINSDK_VER)
 endif()
 
-# Try lowercase `include`/`lib` used by xwin/msvc-wine
-if(NOT EXISTS "${WINSDK_INCLUDE}")
-  set(WINSDK_INCLUDE "${WINSDK_BASE}/include/${WINSDK_VER}")
+if (NOT LLVM_WINSYSROOT OR NOT MSVC_VER OR NOT WINSDK_VER)
+  message(SEND_ERROR
+          "Must specify CMake variable LLVM_WINSYSROOT, MSVC_VER and WINSDK_VER")
 endif()
-if(NOT EXISTS "${WINSDK_LIB}")
-  set(WINSDK_LIB "${WINSDK_BASE}/lib/${WINSDK_VER}")
+
+set(ATLMFC_LIB     "${LLVM_WINSYSROOT}/VC/Tools/MSVC/${MSVC_VER}/atlmfc/lib")
+set(MSVC_INCLUDE   "${LLVM_WINSYSROOT}/VC/Tools/MSVC/${MSVC_VER}/include")
+set(MSVC_LIB       "${LLVM_WINSYSROOT}/VC/Tools/MSVC/${MSVC_VER}/lib")
+set(WINSDK_INCLUDE "${LLVM_WINSYSROOT}/Windows Kits/10/Include/${WINSDK_VER}")
+set(WINSDK_LIB     "${LLVM_WINSYSROOT}/Windows Kits/10/Lib/${WINSDK_VER}")
+
+if (NOT EXISTS "${MSVC_INCLUDE}" OR NOT EXISTS "${MSVC_LIB}")
+  message(SEND_ERROR
+          "CMake variable LLVM_WINSYSROOT and MSVC_VER must point to a folder "
+          "containing MSVC system headers and libraries")
 endif()
 
-if(NOT EXISTS "${WINSDK_BASE}" OR
-   NOT EXISTS "${WINSDK_INCLUDE}" OR
-   NOT EXISTS "${WINSDK_LIB}")
+if(NOT EXISTS "${WINSDK_INCLUDE}" OR NOT EXISTS "${WINSDK_LIB}")
   message(SEND_ERROR
-          "CMake variable WINSDK_BASE and WINSDK_VER must resolve to a valid "
-          "Windows SDK installation")
+          "CMake variable LLVM_WINSYSROOT and WINSDK_VER must resolve to a "
+          "valid Windows SDK installation")
 endif()
 
 if(NOT EXISTS "${WINSDK_INCLUDE}/um/Windows.h")
   message(SEND_ERROR "Cannot find Windows.h")
 endif()
 if(NOT EXISTS "${WINSDK_INCLUDE}/um/WINDOWS.H")
   set(case_sensitive_filesystem TRUE)
 endif()

 
 # These flags are used during build time. So if CFLAGS/CXXFLAGS/LDFLAGS is set
 # for the target, makes sure these are unset during build time.
 set(CROSS_TOOLCHAIN_FLAGS_NATIVE "${_CTF_NATIVE_DEFAULT}" CACHE STRING "")
 
 set(COMPILE_FLAGS
     -D_CRT_SECURE_NO_WARNINGS
     --target=${TRIPLE_ARCH}-windows-msvc
     -fms-compatibility-version=19.14
-    -imsvc "${ATLMFC_INCLUDE}"
-    -imsvc "${MSVC_INCLUDE}"
-    -imsvc "${WINSDK_INCLUDE}/ucrt"
-    -imsvc "${WINSDK_INCLUDE}/shared"
-    -imsvc "${WINSDK_INCLUDE}/um"
-    -imsvc "${WINSDK_INCLUDE}/winrt")
+    -vctoolsversion ${MSVC_VER}
+    -winsdkversion ${WINSDK_VER})
 
 if(case_sensitive_filesystem)
   # Ensure all sub-configures use the top-level VFS overlay instead of generating their own.
   init_user_prop(winsdk_vfs_overlay_path)
   if(NOT winsdk_vfs_overlay_path)
     set(winsdk_vfs_overlay_path "${CMAKE_BINARY_DIR}/winsdk_vfs_overlay.yaml")
     generate_winsdk_vfs_overlay("${WINSDK_INCLUDE}" "${winsdk_vfs_overlay_path}")
     init_user_prop(winsdk_vfs_overlay_path)
   endif()
   list(APPEND COMPILE_FLAGS
        -Xclang -ivfsoverlay -Xclang "${winsdk_vfs_overlay_path}")
 endif()
 
 string(REPLACE ";" " " COMPILE_FLAGS "${COMPILE_FLAGS}")
 string(APPEND CMAKE_C_FLAGS_INIT " ${COMPILE_FLAGS}")
 string(APPEND CMAKE_CXX_FLAGS_INIT " ${COMPILE_FLAGS}")
 
 set(LINK_FLAGS
     # Prevent CMake from attempting to invoke mt.exe. It only recognizes the slashed form and not the dashed form.
     /manifest:no
 
     -libpath:"${ATLMFC_LIB}/${WINSDK_ARCH}"
     -libpath:"${MSVC_LIB}/${WINSDK_ARCH}"
     -libpath:"${WINSDK_LIB}/ucrt/${WINSDK_ARCH}"
     -libpath:"${WINSDK_LIB}/um/${WINSDK_ARCH}")
 
 if(case_sensitive_filesystem)
   # Ensure all sub-configures use the top-level symlinks dir instead of generating their own.