diff --git a/clang/lib/Analysis/ReachableCode.cpp b/clang/lib/Analysis/ReachableCode.cpp
--- a/clang/lib/Analysis/ReachableCode.cpp
+++ b/clang/lib/Analysis/ReachableCode.cpp
@@ -138,10 +138,10 @@
 static SourceLocation getTopMostMacro(SourceLocation Loc, SourceManager &SM) {
   assert(Loc.isMacroID());
   SourceLocation Last;
-  while (Loc.isMacroID()) {
+  do {
     Last = Loc;
     Loc = SM.getImmediateMacroCallerLoc(Loc);
-  }
+  } while (Loc.isMacroID());
   return Last;
 }