[Dominators] Teach IDF to use level information

Summary: This patch teaches IteratedDominanceFrontier to use the level information stored in DomTreeNodes instead of calculating it manually.

Reviewers: dberlin, sanjoy, davide

Reviewed By: davide

Subscribers: davide, llvm-commits

Differential Revision: https://reviews.llvm.org/D34703

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306894 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed