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the IR going into it and to clean up the IR produced by the vectorizers. Note that these are *off by default* right now while folks collect data on whether the performance tradeoff is reasonable. In a build of the 'opt' binary, I see about 2% compile time regression due to this change on average. This is in my mind essentially the worst expected case: very little of the opt binary is going to *benefit* from these extra passes. I've seen several benchmarks improve in performance my small amounts due to running these passes, and there are certain (rare) cases where these passes make a huge difference by either enabling the vectorizer at all or by hoisting runtime checks out of the outer loop. My primary motivation is to prevent people from seeing runtime check overhead in benchmarks where the existing passes and optimizers would be able to eliminate that. I've chosen the sequence of passes based on the kinds of things that seem likely to be relevant for the code at each stage: rotaing loops for the vectorizer, finding correlated values, loop invariants, and unswitching opportunities from any runtime checks, and cleaning up commonalities exposed by the SLP vectorizer. I'll be pinging existing threads where some of these issues have come up and will start new threads to get folks to benchmark and collect data on whether this is the right tradeoff or we should do something else. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219644 91177308-0d34-0410-b5e6-96231b3b80d8