[PATCH] D51850: [IndVars][NFC] Refactor to make modifications of Changed transparent

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev created this revision.
mkazantsev added reviewers: skatkov, uabelho, sanjoy.

IndVarSimplify's design is somewhat odd in the way how it reports that
some transform has made a change. It has a `Changed` field which can
be set from within any function, which makes it hard to track whether or
not it was set properly after a transform was made. It leads to oversights
in marking it properly, see example in PR38855.

This patch removes the `Changed` field, turns it into a local and unifies
the signatures of all relevant transform functions to return boolean value
which designates whether or not this transform has made a change.


https://reviews.llvm.org/D51850

Files:
  lib/Transforms/Scalar/IndVarSimplify.cpp

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