Make DT a transitive dependency of LI.

Summary:
LoopInfoWrapperPass::verify uses DT, which means DT must be alive
even if it has no direct users.

Fixes a crash in expensive checks mode.

Reviewers: pcc, leonardchan

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64896

llvm-svn: 366388
diff --git a/llvm/lib/Analysis/LoopInfo.cpp b/llvm/lib/Analysis/LoopInfo.cpp
index c59e48a..aa5da08 100644
--- a/llvm/lib/Analysis/LoopInfo.cpp
+++ b/llvm/lib/Analysis/LoopInfo.cpp
@@ -1039,7 +1039,7 @@
 
 void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesAll();
-  AU.addRequired<DominatorTreeWrapperPass>();
+  AU.addRequiredTransitive<DominatorTreeWrapperPass>();
 }
 
 void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const {