[PATCH] D52938: [CUDA] Use all 64 bits of GUID in __nv_module_id

[Artem Belevich via Phabricator via cfe-commits]

tra added a comment.

This particular change is largely cosmetic. I've just spotted this nit while I was debugging a different problem.

It's also related to module ID.

We're trying to compile NCCL 2.3 with -fcuda-rdc and we were getting duplicate symbols when we tried to link multiple object files compiled from the same source file.
E.g.

  clang++ -DPART1 -o foo-1.o  foo.cu
  clang++ -DPART2 -o foo-2.o  foo.cu
  ...
  nvlink ....

The stubs generated by nvlink ended up with conflicting names (based on module ID) that were identical for all foo-*.o.

It appears that clang generates ID based on the source file name only, so all foo-*.o end up with identical ID. 
NVCC, on the other hand, appears to generate ID based on some other factors (compiler flags? preprocessed TU source?) so each object file gets a unique ID.

For now we've worked around this by renaming the source files before compilation of each part, but we will need to find a better solution.


https://reviews.llvm.org/D52938