Build errors with ARM64 on Windows

[num3ric]

cmake -S . -B build -G "Visual Studio 17 2022"^
    -A ARM64^
    -DBUILD_SHARED_LIBS=ON^
    -DOCIO_BUILD_STATIC=OFF^
    -DOCIO_BUILD_TRUELIGHT=OFF^
    -DOCIO_BUILD_APPS=OFF^
    -DOCIO_BUILD_GPU_TESTS=OFF^
    -DOCIO_BUILD_NUKE=OFF^
    -DOCIO_BUILD_DOCS=OFF^
    -DOCIO_BUILD_TESTS=OFF^
    -DOCIO_BUILD_PYGLUE=OFF^
    -DOCIO_BUILD_JNIGLUE=OFF^
    -DOCIO_STATIC_JNIGLUE=OFF^
    -DOCIO_USE_BOOST_PTR=OFF^
    -DOCIO_PYGLUE_LINK=OFF^
    -DOCIO_BUILD_PYTHON=OFF^
    -DCMAKE_INSTALL_PREFIX:PATH=.\install

cmake --build build --config Release --target INSTALL

yields the following build errors:

OpenColorIO-2.3.0\src\OpenColorIO\CPUInfo.cpp(40,12): error C3861: '_xg
etbv': identifier not found
OpenColorIO-2.3.0\src\OpenColorIO\CPUInfo.cpp(52,5): error C3861: '__cp
uid': identifier not found

[num3ric]

At first glance, it looks like the full set of preprocessor checks should be based on defined( __aarch64__ ) || defined( __arm64__ ) || defined( _M_ARM64 ) instead of just __aarch64__, but I could be wrong.

EDIT: Or maybe the fix ought to be in Cmake? I would expect this invocation to disable OCIO_ARCH_X86 actually.

EDIT 2: Maybe this is a CMake bug actually. CMAKE_SYSTEM_PROCESSOR:UNINITIALIZED=ARM64 in the cache but while running CMAKE_SYSTEM_PROCESSOR is AMD64... https://gitlab.kitware.com/cmake/cmake/-/issues/15170

EDIT 3: Adding the following in the NOT APPLE case seems to fix the issue for me:

    if(MSVC)
        set(CMAKE_SYSTEM_PROCESSOR ${MSVC_CXX_ARCHITECTURE_ID})
    endif()

[num3ric]

Tagging @markreidvfx

[doug-walker]

@num3ric , thanks for the report. Would you please provide a bit more detail about the CPU in the machine you are building on and which versions of CMake and MSVC?

[num3ric]

cmake version 3.21.1
Visual Studio 17 2022
OS Name Microsoft Windows 10 Enterprise
Version 10.0.19044 Build 19044
Processor AMD Ryzen Threadripper PRO 3995WX 64-Cores, 2695 Mhz, 64 Core(s), 64 Logical Processor(s)

[doug-walker]

Thanks for the added detail @num3ric. I was discussing this with Cedrik and we're still not clear on what you're trying to do. We see how your EDIT 3 above would work around an issue where CMAKE_SYSTEM_PROCESSOR has the unexpected value on AMD processors (and we could add AMD64 to the list in the CMake checks). But we're confused by your use of the -A ARM64 option above. Are you trying to cross-compile for a Windows ARM platform on an AMD64 machine? If so, EDIT 3 doesn't seem like it would fix that.

The ARM work we've done so far has been solely for macOS, support for other platforms was not in scope for our work and we've done no testing to support use of ARM on other platforms.

[num3ric]

Yes, it is unusual... https://devblogs.microsoft.com/cppblog/windows-arm64-support-for-cmake-projects-in-visual-studio/

To be honest, we used to support Windows ARM64 for Hololens but that's been dropped, so I don't think we use this build configuration much, if at all, anymore. It's there mostly there for "coverage".

I noticed that CMAKE_SYSTEM_PROCESSOR (which can differ from CMAKE_HOST_SYSTEM_PROCESSOR) wasn't reflecting ARM64, per cmake link above. EDIT 3 fixes the build error... but only sort of accidentally/indirectly by disabling SIMD code: OCIO_ARCH_X86 == 0 & __aarch64__ == 0. Looks like CPUInfo essentially vanishes in this case... Not an official solution by any means.

To be clear, I'm not advocating for Win ARM64 SIMD support, just looking for an error-free build. I'll dig around some more too... I saw that OpenCV may be a good reference here.

[doug-walker]

Based on @num3ric's testing, this should be fixed by PR #2089.