Adding treatment of ARM platforms if a SYCL-compatible compiler is detected

[christophriesinger]

At least since Clang 19, LLVM Clang supports SYCL and thus, the -fsycl compiler argument. Hence, if such a LLVM Clang is detected by CMake, common/cmake/dpcpp.cmake gets included. Since LLVM Clang with support for the -fsycl compiler argument is also available for ARM platforms (e.g. Clang-cl for Windows on ARM) dpcpp.cmake has to make sure no arguments are passed to Clang not supported by ARM (e.g. -msse2).

This code changes copies the treatment for ARM platforms from clang.cmake to dpcpp.cmake.

[Copilot]

Pull request overview

Updates Embree’s SYCL (DPCPP/Clang -fsycl) CMake configuration to avoid passing x86-only compile flags when building on ARM platforms, mirroring the existing ARM handling in the Clang toolchain CMake.

Changes:

• Add EMBREE_ARM-gated ISA flag definitions in dpcpp.cmake (including a macOS universal-binary x86_64 sub-case).
• Adjust default (non-ARM) SSE2 flags in dpcpp.cmake to match the pattern used in clang.cmake.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

[anthony-linaro]

I might be wrong here, but couldn't we just make a change here: https://github.com/RenderKit/embree/blob/master/CMakeLists.txt#L228, guarded by something like (untested)

if(EMBREE_ARM AND WIN32 AND ${CMAKE_CXX_COMPILER_ID} MATCHES "Clang" AND NOT COMPILER_HAS_SYCL_SUPPORT)
    set(COMPILER_HAS_SYCL_SUPPORT OFF)
endif()

Which would bypass the entire dpcpp thing? The build instructions from #439 I wrote still work if you just add -DCOMPILER_HAS_SYCL_SUPPORT=OFF to the configure line on the current tip of main, no more changes needed.