llvm-project

8d186e21 - [LoopUnroll][NFCI] Clean up remainder followup metadata handling (#165272)

[LoopUnroll][NFCI] Clean up remainder followup metadata handling (#165272) Followup metadata for remainder loops is handled by two implementations, both added by 7244852557ca6: 1. `tryToUnrollLoop` in `LoopUnrollPass.cpp`. 2. `CloneLoopBlocks` in `LoopUnrollRuntime.cpp`. As far as I can tell, 2 is useless: I added `assert(!NewLoopID)` for the `NewLoopID` returned by the `makeFollowupLoopID` call, and it never fails throughout check-all for my build. Moreover, if 2 were useful, it appears it would have a bug caused by 7cd826a321d9. That commit skips adding loop metadata to a new remainder loop if the remainder loop itself is to be completely unrolled because it will then no longer be a loop. However, that commit incorrectly assumes that `UnrollRemainder` dictates complete unrolling of a remainder loop, and thus it skips adding loop metadata even if the remainder loop will be only partially unrolled. To avoid further confusion here, this patch removes 2. check-all continues to pass for my build. If 2 actually is useful, please advise so we can create a test that covers that usage. Near 2, this patch retains the `UnrollRemainder` guard on the `setLoopAlreadyUnrolled` call, which adds `llvm.loop.unroll.disable` to the remainder loop. That behavior exists both before and after 7cd826a321d9. The logic appears to be that remainder loop unrolling (whether complete or partial) is opt-in. That is, unless `UnrollRemainder` is true, `UnrollRuntimeLoopRemainder` skips running remainder loop unrolling, and `llvm.loop.unroll.disable` suppresses any later attempt at it. This patch also extends testing of remainder loop followup metadata to be sure remainder loop partial unrolling is handled correctly by 1.