diff --git a/clang/lib/Sema/SemaCodeComplete.cpp b/clang/lib/Sema/SemaCodeComplete.cpp
index ade6e46..81eed43 100644
--- a/clang/lib/Sema/SemaCodeComplete.cpp
+++ b/clang/lib/Sema/SemaCodeComplete.cpp
@@ -692,18 +692,6 @@
   return Result;
 }
 
-/// Determine whether \p Id is a name reserved for the implementation (C99
-/// 7.1.3, C++ [lib.global.names]).
-static bool isReservedName(const IdentifierInfo *Id,
-                           bool doubleUnderscoreOnly = false) {
-  if (Id->getLength() < 2)
-    return false;
-  const char *Name = Id->getNameStart();
-  return Name[0] == '_' &&
-         (Name[1] == '_' ||
-          (Name[1] >= 'A' && Name[1] <= 'Z' && !doubleUnderscoreOnly));
-}
-
 // Some declarations have reserved names that we don't want to ever show.
 // Filter out names reserved for the implementation if they come from a
 // system header.
@@ -713,13 +701,13 @@
     return false;
 
   // Ignore reserved names for compiler provided decls.
-  if (isReservedName(Id) && ND->getLocation().isInvalid())
+  if (Id->isReservedName() && ND->getLocation().isInvalid())
     return true;
 
   // For system headers ignore only double-underscore names.
   // This allows for system headers providing private symbols with a single
   // underscore.
-  if (isReservedName(Id, /*doubleUnderscoreOnly=*/true) &&
+  if (Id->isReservedName(/*doubleUnderscoreOnly=*/true) &&
       SemaRef.SourceMgr.isInSystemHeader(
           SemaRef.SourceMgr.getSpellingLoc(ND->getLocation())))
     return true;