[InstCombine] Improve infinite loop detection
This patch limits the default number of iterations performed by InstCombine. It also exposes a new option that allows to specify how many iterations is considered getting stuck in an infinite loop.
Based on experiments performed on real-world C++ programs, InstCombine seems to perform at most ~8-20 iterations, so treating 1000 iterations as an infinite loop seems like a safe choice. See D71145 for details.
The two limits can be specified via command line options.
Reviewers: spatel, lebedev.ri, nikic, xbolva00, grosser
Reviewed By: spatel
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D71673