[PATCH] D112060: [NARY-REASSOCIATE] Fix infinite recursion optimizing min\max

[Evgeniy via Phabricator via llvm-commits]

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To guarantee convergence of the algorithm each optimization step should decrease number of instructions when IR is modified. This property is not held in this test case. The problem is that SCEV Expander may do "unexpected" reassociation what results in creation of new min/max chains and introduction of extra instructions. As a result on each step we indefinitely optimize back and forth.

The solution is to restrict SCEV Expander to perform uncontrolled reassociations by means of "Unknown" expressions.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D112060

Files:
  llvm/lib/Transforms/Scalar/NaryReassociate.cpp
  llvm/test/Transforms/NaryReassociate/nary-req.ll

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