Fix asan failures on OpenMP.

llvm-svn: 301536
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index fb13669..9c6948b 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -833,6 +833,8 @@
   auto I = std::prev(StartI);
   do {
     ++I;
+    if (I == EndI)
+      break;
     if (!DPred(I->Directive) && !isParallelOrTaskRegion(I->Directive))
       continue;
     DSAVarData DVar = getDSA(I, D);