OpenCL has had a bumpy ride over the years w.r.t. to the prospects of using C++ to write kernels. First there was “OpenCL C++ kernel language”, standardized with OpenCL v2.1 – but that did not quite catch, and AFAICR never got supported on NVIDIA GPUs; and then, with OpenCL 3.0 – that was scratched entirely, in favor of C++ for OpenCL, which is “based on a Clang/LLVM compiler which implements a subset of C++17 and SPIR-V intermediate code” – and was announced/published as late as 2021.