[all-commits] [llvm/llvm-project] 225df7: [NFC] Add option to disable IV widening if needed

[max-azul via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 225df71951cb7b870d078167de1a375a674c79df
      https://github.com/llvm/llvm-project/commit/225df71951cb7b870d078167de1a375a674c79df
  Author: Max Kazantsev <mkazantsev at azul.com>
  Date:   2020-10-09 (Fri, 09 Oct 2020)

  Changed paths:
    M llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

  Log Message:
  -----------
  [NFC] Add option to disable IV widening if needed

IV widening is sometimes a strictly harmful transform (some examples
of this are shown in tests 11, 12 in widen-loop-comp.ll). One of the
reasons of this is that sometimes SCEV fails to prove some facts after
part of guards has been widened.

Though each single such case looks like a bug that can be addressed,
it seems that disabling of IV widening may be profitable in some cases.
We want to have an option to do so. By default, existing behavior is
preserved and IV widening is on.