[PATCH] D58435: [SCEV] Ensure that isHighCostExpansion takes into account what is being divided

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: sanjoy, wmi, lebedev.ri, mkazantsev.
Herald added subscribers: jdoerfert, javed.absar.

A SCEV is not low-cost just because you can divide it by a power of 2. We need to also
check what we are dividing to make sure it too is not a high-code expansion. This helps
to not expand the exit value of certain loops, helping not to bloat the code.

The change in no-iv-rewrite.ll is reverting to back before rL194116 <https://reviews.llvm.org/rL194116>, and looks a lot like
the other tests in replace-loop-exit-folds.ll.


https://reviews.llvm.org/D58435

Files:
  lib/Analysis/ScalarEvolutionExpander.cpp
  test/Transforms/IndVarSimplify/no-iv-rewrite.ll
  test/Transforms/IndVarSimplify/replace-loop-exit-folds.ll

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