tree 625ce04c623881d6f4941a20d136833776a2c436
parent b78e72600fdaa0b1d126c34d85aa3c11af32bf78
author Johannes Doerfert <johannes@jdoerfert.de> 1684446580 -0700
committer Copybara-Service <copybara-worker@google.com> 1686008479 -0700

[OpenMP] Improve default block count selection fow low block counts

If a combined loop has insufficient parallelism (= low trip count), we
might end up with too few teams/blocks. To counter that we can reduce
the number of threads per team we use. This patch implements a heuristic
and exposes a new environment variable to control the minimum of threads
to be employed in this case.

Issue reported by:
Felipe Cabarcas Jaramillo <cabarcas@udel.edu> (@fel-cab).

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D152014

GitOrigin-RevId: 6629a96a8ce5f07c72bd4931180a3ca9fc535cbb