[DA] DivergenceAnalysis for unstructured, reducible CFGs
This is patch 2 of the new DivergenceAnalysis (https://reviews.llvm.org/D50433).
This patch contains a generic divergence analysis implementation for
unstructured, reducible Control-Flow Graphs. It contains two new classes.
The SyncDependenceAnalysis class lazily computes sync dependences, which
relate divergent branches to points of joining divergent control. The
DivergenceAnalysis class contains the generic divergence analysis
Reviewed By: nhaehnle
Subscribers: sameerds, kristina, nhaehnle, xbolva00, tschuett, mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D51491