[SCEV] Pick backedge values for phi nodes correctly
Summary:
`getConstantEvolutionLoopExitValue` and `ComputeExitCountExhaustively`
assumed all phi nodes in the loop header have the same order of incoming
values. This is not correct, and this commit changes
`getConstantEvolutionLoopExitValue` and `ComputeExitCountExhaustively`
to lookup the backedge value of a phi node using the loop's latch block.
Unfortunately, there is still some code duplication
`getConstantEvolutionLoopExitValue` and `ComputeExitCountExhaustively`.
At some point in the future we should extract out a helper class /
method that can evolve constant evolution phi nodes across iterations.
Fixes 25060. Thanks to Mattias Eriksson for the spot-on analysis!
Depends on D13457.
Reviewers: atrick, hfinkel
Subscribers: materi, llvm-commits
Differential Revision: http://reviews.llvm.org/D13458
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249712 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed