[PATCH] D101699: [Support/Parallel] Add a special case for 0/1 items to llvm::parallel_for_each.

[Chris Lattner via Phabricator via llvm-commits]

lattner added a comment.

Spinning up the threadpool is expensive, but the bigger issue is that Threading.h doesn't support reentrant concurrency.  If you have a parallel for loop with one element, then that element does a parallel for loop over 10000 elements, it will run in serial.  :-(


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https://reviews.llvm.org/D101699