Reduce double set lookups. NFC.

llvm-svn: 219504
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 6e43a3d..23f5f13 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -2483,8 +2483,7 @@
   // that is the increment of the associated for-loop.
   // Exclude loop var from the list of variables with implicitly defined data
   // sharing attributes.
-  while (VarsWithImplicitDSA.count(Var) > 0)
-    VarsWithImplicitDSA.erase(Var);
+  VarsWithImplicitDSA.erase(Var);
 
   // OpenMP [2.14.1.1, Data-sharing Attribute Rules for Variables Referenced in
   // a Construct, C/C++].