jlebar added a comment. In https://reviews.llvm.org/D25403#573666, @mclow.lists wrote:
> Yesterday and today is the first time in a while that clang has been > seriously broken for more than an hour or so. > I'm not inclined to worry about it yet. Oh, awesome. That sounds good to me. The question about build configurations still stands, though -- should that be documented somewhere? In particular I could not successfully run check-cxx by following the directions I found by googling. I am volunteering to write the patch if we can agree on what the workflow should be. >>> I don't see how this can possibly be constexpr. >>> it calls isfinite(), which is hoisted from ::isfinite(), which comes from >>> the C library. >>> Since C knows nothing about constexpr, we're stuck. >> >> Functions that call non-constexpr things can be marked constexpr; you just >> can't evaluate them in a constexpr context (as you demonstrated). >> >> All I need is for the function to be marked as constexpr; I do not need the >> function be constexpr-evaluatable. > > Then what's the point? How can you test if it is correct? https://reviews.llvm.org/D24971 tests this. I suppose we could write a test inside libcxx, but it would be kind of ugly. > I guess I don't understand the motivation for this change. To make <complex> work in CUDA, we do the following terrible, awful, horrible, no good thing: ...well, I can just show you the code. https://github.com/llvm-project/llvm-project/blob/master/clang/lib/Headers/cuda_wrappers/complex The significant part here is #pragma clang force_cuda_host_device begin #include_next <complex> #pragma clang force_cuda_host_device end This tells clang, everything between the two pragmas is something that we can run on the host (CPU) and device (GPU). And that works fine for libstdc++. But for libc++, marking everything inside <complex> as host+device is not enough -- we also need to mark these four functions, which are called from <complex>. We could mark them as __host__ __device__ explicitly, but then we'd need checks for CUDA compilation inside of libc++, and I've been avoiding asking for that. Instead, marking these functions as constexpr works, because constexpr functions are implicitly host+device in our CUDA implementation. https://reviews.llvm.org/D25403 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
