ABataev added inline comments.
================ Comment at: llvm/lib/Frontend/OpenMPIRBuilder.cpp:228 + getOrCreateThreadID(getOrCreateIdent(SrcLocStr))}; + bool UseCancelBarrier = !ForceSimpleCall && CancellationBlock; + Value *Result = Builder.CreateCall( ---------------- jdoerfert wrote: > ABataev wrote: > > jdoerfert wrote: > > > ABataev wrote: > > > > jdoerfert wrote: > > > > > ABataev wrote: > > > > > > jdoerfert wrote: > > > > > > > ABataev wrote: > > > > > > > > Maybe add an assert when the cancellation version is requested > > > > > > > > but the cancellation block is not set? Instead of the > > > > > > > > generating simple version of barrier. > > > > > > > The interface doesn't work that way as we do not know here if the > > > > > > > cancellation was requested except if the block was set. That is > > > > > > > basically the flag (and I expect it to continue to be that way). > > > > > > Maybe instead of `ForceSimpleBarrier` add a flag > > > > > > `EmitCancelBarrier` and if it set to true, always emit cancel > > > > > > barrier, otherwise always emit simple barrier? And add an assertion > > > > > > for non-set cancellation block or even accept it as a parameter > > > > > > here. > > > > > > > > > > > > Also, what if we have inner exception handling in the region? Will > > > > > > you handle the cleanup correctly in case of the cancelation barrier? > > > > > > Maybe instead of ForceSimpleBarrier add a flag EmitCancelBarrier > > > > > > and if it set to true, always emit cancel barrier, otherwise always > > > > > > emit simple barrier? And add an assertion for non-set cancellation > > > > > > block or even accept it as a parameter here. > > > > > > > > > > What is the difference in moving some of the boolean logic to the > > > > > caller? Also, we have test to verify we get cancellation barriers if > > > > > we need them, both unit tests and clang lit tests. > > > > > > > > > > > > > > > > Also, what if we have inner exception handling in the region? Will > > > > > > you handle the cleanup correctly in case of the cancelation barrier? > > > > > > > > > > I think so. Right now through the code in clang that does the set up > > > > > of the cancellation block, later through callbacks but we only need > > > > > that for regions where we actually go out of some scope, e.g., > > > > > parallel. > > > > 1. I'm just thinking about future users of thus interface. It woild be > > > > good if we could provide safe interface for all the users, not only > > > > clang. > > > > 2. Exit out of the OpenMP region is not allowed. But you may have inner > > > > try...catch or just simple compound statement with local vars that > > > > require constructors/destructors. And the cancellation barrier may exit > > > > out of these regions. And you need to call all required destructors. > > > > You'd better to think about it now, not later. > > > > 2. [...] You'd better to think about it now, not later. > > > > > > First, I do think about it now and I hope this was not an insinuation to > > > suggest otherwise. > > > > > > > 1. I'm just thinking about future users of thus interface. It woild be > > > > good if we could provide safe interface for all the users, not only > > > > clang. > > > > 2. Exit out of the OpenMP region is not allowed. But you may have inner > > > > try...catch or just simple compound statement with local vars that > > > > require constructors/destructors. And the cancellation barrier may exit > > > > out of these regions. And you need to call all required destructors. > > > > > > Generally speaking, we shall not add features that we cannot use or test > > > with the assumption we will use them in the future. This is suggested by > > > the LLVM best practices. If you have specific changes in mind that are > > > testable and better than what I suggested so far, please bring them > > > forward. You can also bring forward suggestions on how it might look in > > > the future but without a real use case now it is not practical to block a > > > review based on that, given that we can change the interface once the > > > time has come. > > > > > > I said before, we will need callbacks for destructors, actual handling of > > > cancellation blocks, and there are various other features missing right > > > now. Nevertheless, we cannot build them into the current interface, or > > > even try to prepare for all of them, while keeping the patches small and > > > concise. > > It won't work for clang, I'm afraid. You need a list of desructors here. > > But clang uses recursive codegen and it is very hard to walk over the call > > tree and gather all required destructors into a list. At least, it will > > require significant rework in clang frontend. > > Instead of generating the branch to cancellation block in the builder, I > > would suggest to call a single callback function provided by the frontend, > > which will generate correct branch over a chain of the destructor blocks. > > In this case, you won't need this cancellation block at all. This is what I > > meant when said that you need to think about this problem right now. That > > current solution is not very suitable for the use in the frontend. > > It won't work for clang, > > It won't work in the future or it does not work now? If the latter, do you > have a mwe to show the problem? 1. Both. 2. What is mwe? Sure, will simple test tomorrow. 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