[llvm] [DFAJumpThreading] Enable DFAJumpThread by default. (PR #157646)

[Hongyu Chen via llvm-commits]

XChy wrote:

> looking at the big outlier there (openssl/smime.ll with +175%) would be good.

#162447 resolves it partially, but the main cause remains there: the number of phi nodes increases massively, and thus SLPVectorizer slows down. Not come up with a solution for DFAJumpThreading yet. Maybe we can redesign the SSA updating method there.

https://github.com/llvm/llvm-project/pull/157646