Reapply: [ADCE][Dominators] Teach ADCE to preserve dominators
Summary:
This patch teaches ADCE to preserve both DominatorTrees and PostDominatorTrees.
I didn't notice any performance impact when bootstrapping clang with this patch.
The patch was originally committed in r311039 and reverted in r311049.
This revision fixes the problem with not adding a dependency on the
DominatorTreeWrapperPass for the LegacyPassManager.
Reviewers: dberlin, chandlerc, sanjoy, davide, grosser, brzycki
Reviewed By: davide
Subscribers: grandinj, zhendongsu, llvm-commits, david2050
Differential Revision: https://reviews.llvm.org/D35869
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311057
91177308-0d34-0410-b5e6-
96231b3b80d8