oneAPI: Build the support library for Windows.

[maleadt]

Requires a bunch of hacks (libraries are named differently, and somehow end up depending on libMSVCRT.a and libOLDNAMES.a), and even then I'm running into a linker error:

# clang++ -L/workspace/destdir/bin -shared -o liboneapi_support.dll -lsycl7 ...
ld.lld: error: undefined symbol: __declspec(dllimport) sycl::_V1::ext::oneapi::level_zero::make_platform(unsigned long long)
>>> referenced by /workspace/srcdir/oneAPI.jl/deps/src/sycl.cpp:9
>>>               CMakeFiles/oneapi_support.dir/src/sycl.cpp.obj:(syclPlatformCreate)

... even though:

# nm /workspace/destdir/bin/sycl7.lib | grep make_platform
0000000000000000 T ?make_platform@level_zero@oneapi@ext@_V1@sycl@@YA?AVplatform@45@_K@Z
0000000000000000 I __imp_?make_platform@level_zero@oneapi@ext@_V1@sycl@@YA?AVplatform@45@_K@Z

Any thoughts appreciated (also on how to get rid of the ugly things I'm doing).

[maleadt]

The same error when using ld instead of ldd:

# ld ...
ld: CMakeFiles/oneapi_support.dir/src/sycl.cpp.obj: in function `syclPlatformCreate':
/workspace/srcdir/oneAPI.jl/deps/src/sycl.cpp:9: undefined reference to `__imp__ZN4sycl3_V13ext6oneapi10level_zero13make_platformEy'

# nm /workspace/destdir/bin/sycl7.lib | grep make_platform | grep level
0000000000000000 T ?make_platform@level_zero@oneapi@ext@_V1@sycl@@YA?AVplatform@45@_K@Z
0000000000000000 I __imp_?make_platform@level_zero@oneapi@ext@_V1@sycl@@YA?AVplatform@45@_K@Z

[maleadt]

mwe.cpp

#include <CL/sycl.hpp>
#include <sycl/ext/oneapi/backend/level_zero.hpp>

extern "C" int syclPlatformCreate(ze_driver_handle_t driver) {
    sycl::ext::oneapi::level_zero::make_platform((pi_native_handle) driver);
    return 0;
}

# /opt/bin/x86_64-w64-mingw32-libgfortran5-cxx11/x86_64-w64-mingw32-clang++ -isystem /workspace/destdir/include -L/workspace/destdir/bin -shared -o mwe.dll mwe.cpp -lsycl7
ld.lld: error: undefined symbol: __declspec(dllimport) sycl::_V1::ext::oneapi::level_zero::make_platform(unsigned long long)
>>> referenced by /tmp/main-0b612a.o:(syclPlatformCreate)
clang-16: error: linker command failed with exit code 1 (use -v to see invocation)

I guess this is a name mangling issue, with MinGW using a different ABI than MSVC. Compare:

# nm /workspace/destdir/bin/sycl7.lib | grep make_platform | grep level_zero
0000000000000000 T ?make_platform@level_zero@oneapi@ext@_V1@sycl@@YA?AVplatform@45@_K@Z
0000000000000000 I __imp_?make_platform@level_zero@oneapi@ext@_V1@sycl@@YA?AVplatform@45@_K@Z

vs.

# /opt/bin/x86_64-w64-mingw32-libgfortran5-cxx11/x86_64-w64-mingw32-clang++ -isystem /workspace/destdir/include -o main.o -c main.cpp

# nm main.o | grep make_platform
                 U __imp__ZN4sycl3_V13ext6oneapi10level_zero13make_platformEy

From llvm/llvm-project#60847:

The MinGW C++ ABI is very much incompatible with the MSVC ABI, and name mangling is only a very small part of it. Making the name mangling "compatible" does not magically make them compatible.

[maleadt]

Hmm, there is https://clang.llvm.org/docs/MSVCCompatibility.html, but I'm not sure how to use it. Running with -fms-compatibility breaks the sysroot's C++ headers, forcing MSVC ABI by linking clang to clang-cl doesn't seem to work, and passing --target=x86_64-pc-windows-msvc chokes on libgcc (unsupported runtime library 'libgcc' for platform 'MSVC')...

[maleadt]

Not going to bother with this. Intel should provide either MinGW-compatible C++ binaries, or a C API (which IIUC is portable across MSVC/MinGW).