[PATCH] D157738: [OpenMP] Emit offloading entries for indirect target variables

[Jon Chesterfield via Phabricator via cfe-commits]

JonChesterfield added a comment.

If calling an indirect function pointer on the GPU requires a table lookup (keyed by host function addresses, which I didn't think we knew at GPU compile time), and we cannot distinguish indirect function pointers from function pointers, then this feature must send _every_ indirect call on the GPU through the table search in case it hits in the table and then branch on the value if it doesn't.

So if we have a few indirect openmp functions and then we call a function which makes indirect calls of a function pointer which happened to be unrelated to this feature, it's going to search that table anyway. Say qsort on a non-inlined comparison function.

This feature, as I understand it so far, therefore induces a global slowdown on every call to an unknown function. Slow function calls are a bad thing.

What am I missing?


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https://reviews.llvm.org/D157738