Add a new helper RecomputeDominatorTree

It clears loop and dominance information, and builds the dominator
tree. It also dchecks that we are not calling this methods with
irreducible loops, as it is not supported.

When adding this helper we found a partial LSE bug as it was
recomputing dominator tree for irreducible loops.

Test: art/test/testrunner/testrunner.py --host --64 -b --optimizing
Bug: 304749506
Change-Id: Ia4cc72cd19779ad881fa686e52b43679fe5a64d3
5 files changed