tra added a comment. In https://reviews.llvm.org/D47849#1124638, @Hahnfeld wrote:
> IMO this goes into the right direction, we should use the fast implementation > in libdevice. If LLVM doesn't lower these calls in the NVPTX backend, I think > it's ok to use header wrappers as CUDA already does. Using wrapper headers may be OK solution for now. Ideally we should grow our own equivalent of device-side libm so we don't have to rely on libdevice bitcode. > Two questions: > > 1. Can you explain where this is important for "correctness"? Yesterday I > compiled a code using `sqrt` and it seems to spit out the correct results. > Maybe that's relevant for other functions? > 2. Incidentally I ran into a closely related problem: I can't `#include > <math.h>` in translation units compiled for offloading, Clang complains about > inline assembly for x86 (see below). Does that work for you? > > ``` In file included from /usr/include/math.h:413: > /usr/include/bits/mathinline.h:131:43: error: invalid input constraint 'x' in > asm __asm ("pmovmskb %1, %0" : "=r" (__m) : "x" (__x)); ^ > /usr/include/bits/mathinline.h:143:43: error: invalid input constraint 'x' in > asm __asm ("pmovmskb %1, %0" : "=r" (__m) : "x" (__x)); ^ 2 errors generated. > ``` Avoiding conflicts between host and device implementations of the same functions in C++ requires use of attribute-based overloading (https://goo.gl/EXnymm). For CUDA compilation, we provide device-side overloads with __device__ attributes but otherwise identical signatures. We may need to extend it to work in C mode, too. Clang already has __attribute__((overloadable)), so basic overloading mechanisms should be there already. ================ Comment at: lib/Headers/__clang_cuda_device_functions.h:1153-1155 +__DEVICE__ long long llabs(long long __a) { return __nv_llabs(__a); } #if defined(__LP64__) __DEVICE__ long labs(long __a) { return llabs(__a); }; ---------------- I think it should've been `return __nv_llabs(__a)` here and the definition of `long long llabs()` should remain back where it was. Repository: rC Clang https://reviews.llvm.org/D47849 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits