[PATCH] D13460: [IndVars] Don't break dominance in `eliminateIdentitySCEV`

[Sanjoy Das via llvm-commits]

sanjoy created this revision.
sanjoy added reviewers: atrick, hfinkel.
sanjoy added a subscriber: llvm-commits.
sanjoy added a dependency: D13459: [IndVars] Extract out eliminateIdentitySCEV, NFC.
Herald added a subscriber: sanjoy.

After r249211, `getSCEV(X) == getSCEV(Y)` does not guarantee that X and
Y are related in the dominator tree, even if X is an operand to Y (I've
included a toy example in comments, and a real example as a test case).

This commit changes `SimplifyIndVar` to require a `DominatorTree`.  I
don't think this is a problem because `ScalarEvolution` requires it
anyway.

Fixes PR25051.

Depends on D13459.

http://reviews.llvm.org/D13460

Files:
  include/llvm/Transforms/Utils/SimplifyIndVar.h
  lib/Transforms/Scalar/IndVarSimplify.cpp
  lib/Transforms/Utils/LoopUnroll.cpp
  lib/Transforms/Utils/SimplifyIndVar.cpp
  test/Transforms/IndVarSimplify/pr25051.ll

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