[Openmp-commits] [PATCH] D83832: [OpenMP] Provide a flag to disable safety checks for GPU optimizations

[Johannes Doerfert via Phabricator via Openmp-commits]

jdoerfert added a comment.

In D83832#2152027 <https://reviews.llvm.org/D83832#2152027>, @JonChesterfield wrote:

> I think there's an unfortunate interaction with link time optimisation here. If there are external regions, but their code is combined with llvm-link before codegen, then a user could reasonably assume this flag is safe.


If you set this flag and reach a parallel region from a target region outside the translation unit, you will experience problems as calling a non-function pointer is likely not to work. If you don't do this, you are all good.

> Would it would be correct to compile the individual source assuming there may be external uses, then llvm-link the source, then run the pass assuming there are no external uses? That's of interest to the amdgcn case as we can (currently) assume the whole program is available towards the end of the compilation.

If you run O2 <https://reviews.llvm.org/owners/package/2/> after linking *and* properly set the linkage of all your non-kernel functions to internal at that point, you don't need the flag. All the safe cases will then be handled automatically, all the unsafe ones rejected. At least that is what I suspect will happen.


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