Anastasia added inline comments.
================ Comment at: clang/lib/Basic/TargetInfo.cpp:360 + // Set core features based on OpenCL version + for (auto CoreExt : clang::getCoreFeatures(Opts)) + getTargetOpts().OpenCLFeaturesMap[CoreExt] = true; ---------------- azabaznov wrote: > azabaznov wrote: > > Anastasia wrote: > > > azabaznov wrote: > > > > Anastasia wrote: > > > > > I still think the target map should be immutable and especially we > > > > > should not change it silently based on the language compiled even if > > > > > we have done it before but that caused incorrect behavior i.e. > > > > > successfully compiling for the architectures that didn't support the > > > > > features. > > > > > > > > > > If I look at existing targets they already set most of the core > > > > > features apart from 3d image writes. Perhaps it is reasonable to just > > > > > drop this code? I don't think it makes the issue worse, in fact, I > > > > > think it will make the behavior slightly better because now a > > > > > diagnostic will occur if there is an attempt to use the unsupported > > > > > feature although the diagnostic won't be the optimal one. After all > > > > > it will still remain the responsibility of the user to get the right > > > > > combination of a language version and a target. > > > > > > > > > > It would be reasonable however to introduce a diagnostic that would > > > > > report a mismatch between the language version and the hardware > > > > > support available. We report similar diagnostics in > > > > > `CompilerInvocation` already. But I don't think we have to do it in > > > > > this patch because it doesn't introduce any regression. We already > > > > > have a bug although the behavior of this bug will change. And perhaps > > > > > if we add `OpenCLOptions` as a part of `LangOpts` at some point this > > > > > will become straightforward to diagnose. However, I suggest we add > > > > > information about this issue in a FIXME or perhaps this deserves a > > > > > clang bug! > > > > > I still think the target map should be immutable and especially we > > > > > should not change it silently based on the language compiled > > > > > > > > I'm confused. I think we have agreed to unconditionally support core > > > > features for a specific language version. Did I miss something? > > > > > > > > > successfully compiling for the architectures that didn't support the > > > > > features. > > > > > > > > I like idea providing diagnostics in that case. Something like: > > > > "Warning: r600 target doesn't support > > > > cl_khr_3d_image_writes which is core in OpenCL C 2.0, consider using > > > > OpenCL C 3.0". I also think this should be done in a separate commit. > > > > > > > > > If I look at existing targets they already set most of the core > > > > > features apart from 3d image writes. Perhaps it is reasonable to just > > > > > drop this code? > > > > > > > > Oh, I haven't noticed that target set core features. For example > > > > //cl_khr_global_int32_base_atomics// is being set by NVPTX and AMDGPU, > > > > so I agree that this should be removed from target settings. > > > It is correct that the core features should be set unconditionally but > > > not in the `TargetInfo`. If core features are used for targets that don't > > > support them then it should not succeed silently as it does now i.e. this > > > means we need to know what is supported by the targets. > > > > > > Setting target features in `TargetInfo` is correct and should stay. We > > > should not change them here though because the language version doesn't > > > change the target capabilities. It can either expose or hide them from > > > the user but it should not modify targets. This is why `TargetInfo` is > > > immutable after its creation and this is how it should stay. I think it's > > > better if we remove the code here completely and introduce a diagnostic > > > in the subsequent patches that would just check that the features > > > required in the language version are supported by the target. > > > > > > If we do this then during the parsing we will only use feature > > > information from `OpenCLOptions` not the targets, but we will know that > > > the target have support of all the features because the check has been > > > performed earlier. > > I'm not generally against of removing core features set up, but I do have > > some questions and arguments: > > > > > It is correct that the core features should be set unconditionally but > > > not in the TargetInfo > > > > Just to make sure: where do you mean core features should be set > > unconditionally? > > > > > Setting target features in TargetInfo is correct and should stay. We > > > should not change them here though because the language version doesn't > > > change the target capabilities. It can either expose or hide them from > > > the user but it should not modify targets. This is why TargetInfo is > > > immutable after its creation and this is how it should stay > > > > I agree that `TargetInfo `should stay immutable during parsing, but for > > example here, in `TargetInfo::adjust`, current design already allows to > > change target capabilities based on language options, so I don't see what > > is conceptually wrong here. > > > > > If core features are used for targets that don't support them then it > > > should not succeed silently as it does now i.e. this means we need to > > > know what is supported by the targets. > > > > My main point in proposed design is that it is closer to specification: if > > target reports support for OpenCL C 2.0 then there is no need to extra > > checking for support of //core// features such as 3d image writes (we could > > also set for example generic address space and pipes as supported > > unconditionally later) as it is core in OpenCL C 2.0. Of course this should > > not be done silently; some diagnostics like fatal error "OpenCL C 2.0 is > > not supported in this target" or warning "core feature > > cl_khr_3d_image_writes is not supported in this target". > > > > then there is no need to extra checking for support of core features > > I mean extra checks in compiler, not in kernel code. > Just to make sure: where do you mean core features should be set > unconditionally? Why not to set them in `OpenCLOptions` directly? If you don't need any target properties for those why to do this in targets at all? After all `OpenCLFeaturesMap` will only be used to populate the `OpenCLOptions`. During the parsing, we will only use `OpenCLOptions` right? > I agree that TargetInfo should stay immutable during parsing, but for example > here, in TargetInfo::adjust, current design already allows to change target > capabilities based on language options, so I don't see what is conceptually > wrong here. Well, adjust was added to guarantee type widths for OpenCL. However, it has been introduced as a workaround and it still is. It has that fundamental problem of silently mutating the type without any guarantee of integrity i.e. what if targets doesn't support certain bitwidth? Then the code is just compiled incorrectly. There were various proposals to address this but it needs bigger refactoring - perhaps we should introduce the environment component for OpenCL. While for this use case the refactoring is too big and the workaround is very simple there are other places in clang where we could benefit from having such environment component in targets. So the gain might justify the effort. So in short unless there is a very good reason we should avoid using `adjust` because we still would like to remove it or at least remove OpenCL logic from it if possible. > My main point in proposed design is that it is closer to specification: if > target reports support for OpenCL C 2.0 then there is no need to extra > checking for support of core features such as 3d image writes (we could also > set for example generic address space and pipes as supported unconditionally > later) as it is core in OpenCL C 2.0. Of course this should not be done > silently; some diagnostics like fatal error "OpenCL C 2.0 is not supported in > this target" or warning "core feature cl_khr_3d_image_writes is not supported > in this target". I disagree spec never says that the standard should be supported on all targets even if they don't have the required functionality neither it regulate implementation aspects of mapping between language versions to targets. I think the design we should aim for: - Targets set supported HW features - Frontend verifies the features are present for the language version requested during compilation. If there is a mismatch a diagnostic should occur. - Frontend sets language options based on the requested language version and target features that are used during parsing to verify code correctness and create AST. Do you see any issue with this flow? CHANGES SINCE LAST ACTION https://reviews.llvm.org/D92277/new/ https://reviews.llvm.org/D92277 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
