shenhan added inline comments.
================ Comment at: clang/test/Driver/fsplit-machine-functions-with-cuda-nvptx.c:9 + +// Check that -fsplit-machine-functions is passed to both x86 and cuda compilation and does not cause driver error. +// MFS2: -fsplit-machine-functions ---------------- MaskRay wrote: > MaskRay wrote: > > tra wrote: > > > shenhan wrote: > > > > tra wrote: > > > > > shenhan wrote: > > > > > > tra wrote: > > > > > > > We will still see a warning, right? So, for someone compiling > > > > > > > with `-Werror` that's going to be a problem. > > > > > > > > > > > > > > Also, if the warning is issued from the top-level driver, we may > > > > > > > not even be able to suppress it when we disable splitting on GPU > > > > > > > side with `-Xarch_device -fno-split-machine-functions`. > > > > > > > > > > > > > > > > > > > > > We will still see a warning, right? > > > > > > Yes, there still will be a warning. We've discussed it and we think > > > > > > that pass -fsplit-machine-functions in this case is not a proper > > > > > > usage and a warning is warranted, and it is not good that skip > > > > > > doing split silently while uses explicitly ask for it. > > > > > > > > > > > > > Also, if the warning is issued from the top-level driver > > > > > > The warning will not be issued from the top-level driver, it will > > > > > > be issued when configuring optimization passes. > > > > > > So: > > > > > > > > > > > > > > > > > > - -fsplit-machine-functions -Xarch_device > > > > > > -fno-split-machine-functions > > > > > > Will enable MFS for host, disable MFS for gpus and without any > > > > > > warnings. > > > > > > > > > > > > - -Xarch_host -fsplit-machine-functions > > > > > > The same as the above > > > > > > > > > > > > - -Xarch_host -fsplit-machine-functions -Xarch_device > > > > > > -fno-split-machine-functions > > > > > > The same as the above > > > > > > > > > > > > We've discussed it and we think that pass -fsplit-machine-functions > > > > > > in this case is not a proper usage and a warning is warranted, and > > > > > > it is not good that skip doing split silently while uses explicitly > > > > > > ask for it. > > > > > > > > > > I would agree with that assertion if we were talking exclusively > > > > > about CUDA compilation. > > > > > However, a common real world use pattern is that the flags are set > > > > > globally for all C++ compilations, and then CUDA compilations within > > > > > the project need to do whatever they need to to keep things working. > > > > > The original user intent was for the option to affect the host > > > > > compilation. There's no inherent assumption that it will do anything > > > > > useful for the GPU. > > > > > > > > > > In number of similar cases in the past we did settle on silently > > > > > ignoring some top-level flags that we do expect to encounter in real > > > > > projects, but which made no sense for the GPU. E.g. sanitizers. If > > > > > the project is built w/ sanitizer enabled, the idea is to sanitize > > > > > the host code, The GPU code continues to be built w/o sanitizer > > > > > enabled. > > > > > > > > > > Anyways, as long as we have a way to deal with it it's not a big deal > > > > > one way or another. > > > > > > > > > > > -fsplit-machine-functions -Xarch_device -fno-split-machine-functions > > > > > > Will enable MFS for host, disable MFS for gpus and without any > > > > > > warnings. > > > > > > > > > > OK. This will work. > > > > > > > > > > > > > > > In number of similar cases in the past we did settle on silently > > > > > ignoring some top-level flags that we do expect to encounter in real > > > > > projects, but which made no sense for the GPU. E.g. sanitizers. If > > > > > the project is built w/ sanitizer enabled, the idea is to sanitize > > > > > the host code, The GPU code continues to be built w/o sanitizer > > > > > enabled. > > > > > > > > Can I understand it this way - if the compiler is **only** building for > > > > CPUs, then silently ignore any optimization flags is not a good > > > > behavior. If the compiler is building CPUs and GPUs, it is still not a > > > > good behavior to silently ignore optimization flags for CPUs, but it is > > > > probably ok to silently ignore optimization flags for GPUs. > > > > > > > > > OK. This will work. > > > > Thanks for confirming. > > > > it is probably ok to silently ignore optimization flags for GPUs. > > > > > > In this case, yes. > > > > > > I think the most consistent way to handle the situation is to keep the > > > warning in place at cc1 compiler level, but change the driver behavior > > > (and document it) so that it does not pass the splitting options to > > > offloading sub-compilations. This way we'll do the sensible thing for the > > > most common use case, yet would still warn if the user tries to enable > > > the splitting where they should not (e.g. by using `-Xclang > > > -fsplit-machine-functions` during CUDA compilation) > > > > > > > > > > > > > > There are excessive spaces before `%clang`. We should keep just one space: > > `RUN: %clang` > I agree with @tra's analysis. Either do nothing on Clang side and requiring > `-fsplit-machine-functions -Xarch_device -fno-split-machine-functions` or > ignoring the option when creating a device job works for me. > > This patch changed the behavior in an unintended direction. > Either do nothing on Clang side and requiring -fsplit-machine-functions > -Xarch_device -fno-split-machine-functions or ignoring the option when > creating a device job works for me. > This patch changed the behavior in an unintended direction. Thanks Ray. Just a little bit confused, what this patch does is indeed "requiring -fsplit-machine-functions -Xarch_device -fno-split-machine-functions", before this patch, this usage will cause an error. What do you suggest? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D157750/new/ https://reviews.llvm.org/D157750 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
