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a142d0e600
Summary: An alternative to D48597. Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=37936 | PR37936 ]]. The problem is as follows: 1. `indvars` marks `%dec` as `NUW`. 2. `loop-instsimplify` runs `instsimplify`, which constant-folds `%dec` to -1 (D47908) 3. `loop-reduce` tries to do some further modification, but crashes with an type assertion in cast, because `%dec` is no longer an `Instruction`, If the runline is split into two, i.e. you first run `-indvars -loop-instsimplify`, store that into a file, and then run `-loop-reduce`, there is no crash. So it looks like the problem is due to `-loop-instsimplify` not discarding SCEV. But in this case we can just not crash if it's not an `Instruction`. This is just a local fix, unlike D48597, so there may very well be other problems. Reviewers: mkazantsev, uabelho, sanjoy, silviu.baranga, wmi Reviewed By: mkazantsev Subscribers: evstupac, javed.absar, spatel, llvm-commits Differential Revision: https://reviews.llvm.org/D48599 llvm-svn: 335950