[Openmp-commits] [PATCH] D46842: [OpenMP][libomptarget] Make bitcode library building depend on clang and llvm-linker being available

[Gheorghe-Teodor Bercea via Phabricator via Openmp-commits]

gtbercea added a comment.

I am not at all convinced. I think there are absolutely no good arguments against allowing the just built compiler to build the BCLIB (as a default, this is simply a default which can be overwritten at any time by the user). The drawbacks you mention have no detrimental impact on the quality of life of the compiler developer. Developers improving other parts of the compiler who do not care about OpenMP and device offloading can just disable the building of the BCLIB because it is optional after all. The BCLIB is something that is required for performance not correctness so it can be disabled at any time. Even when BCLIB building is turned on there is no perceptible overhead to it, compared to the time it takes to compile a cpp file somewhere in the source code, the BCLIB builds instantly.

Your argument that an older version is better is actually wrong. Using an older version to build the BCLIB is always a BAD idea. The reason why you want to build the BCLIB is so that the runtime functions actually get inlined. If you use an older compiler the functions will not be inlined which defeats the purpose of having the BCLIB in the first place. I stumbled again upon this problem today after updating to the latest changes.

I do not understand why you are opposing this, so far I haven't heard a single strong argument against this.

First of all, I just tried the latest version of trunk which silently uses the CMAKE_CXX_COMPILER (which is an older clang) and even though the BCLIB is built, no function is actually inlined if you check the LLVM code. As soon as the just-built compiler is used to compile the BCLIB the functions are inlined.


Repository:
  rOMP OpenMP

https://reviews.llvm.org/D46842