diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -593,6 +593,12 @@
   let Subjects = SubjectList<[Function, GlobalVar], ErrorDiag>;
   let Documentation = [Undocumented];
 }
+def ClangBuiltinOverride : Attr {
+  let Spellings = [GCC<"__clang_builtin">];
+  let Args = [IdentifierArgument<"BuiltinName">];
+  let Subjects = SubjectList<[Function], ErrorDiag>;
+  let Documentation = [Undocumented];
+}
 
 def Aligned : InheritableAttr {
   let Spellings = [GCC<"aligned">, Declspec<"align">, Keyword<"alignas">,
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -3075,10 +3075,18 @@
 /// functions as their wrapped builtins. This shouldn't be done in general, but
 /// it's useful in Sema to diagnose calls to wrappers based on their semantics.
 unsigned FunctionDecl::getBuiltinID(bool ConsiderWrapperFunctions) const {
-  if (!getIdentifier())
-    return 0;
+  unsigned BuiltinID;
+
+  if (hasAttr<ClangBuiltinOverrideAttr>()) {
+    IdentifierInfo *II = getAttr<ClangBuiltinOverrideAttr>()->getBuiltinName();
+    BuiltinID = II->getBuiltinID();
+  } else {
+    if (!getIdentifier())
+      return 0;
+
+    BuiltinID = getIdentifier()->getBuiltinID();
+  }
 
-  unsigned BuiltinID = getIdentifier()->getBuiltinID();
   if (!BuiltinID)
     return 0;
 
@@ -3102,7 +3110,8 @@
 
   // If the function is marked "overloadable", it has a different mangled name
   // and is not the C library function.
-  if (!ConsiderWrapperFunctions && hasAttr<OverloadableAttr>())
+  if (!ConsiderWrapperFunctions && hasAttr<OverloadableAttr>() &&
+      !hasAttr<ClangBuiltinOverrideAttr>())
     return 0;
 
   if (!Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID))
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -5041,6 +5041,13 @@
       AL.getAttributeSpellingListIndex()));
 }
 
+static void handleClangBuiltinOverrideAttribute(Sema &S, Decl *D,
+                                                const ParsedAttr &AL) {
+  D->addAttr(::new (S.Context) ClangBuiltinOverrideAttr(
+      AL.getRange(), S.Context, AL.getArgAsIdent(0)->Ident,
+      AL.getAttributeSpellingListIndex()));
+}
+
 //===----------------------------------------------------------------------===//
 // Checker-specific attribute handlers.
 //===----------------------------------------------------------------------===//
@@ -7430,6 +7437,10 @@
   case ParsedAttr::AT_MSAllocator:
     handleMSAllocatorAttr(S, D, AL);
     break;
+
+  case ParsedAttr::AT_ClangBuiltinOverride:
+    handleClangBuiltinOverrideAttribute(S, D, AL);
+    break;
   }
 }
 
diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
--- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -36,6 +36,7 @@
 // CHECK-NEXT: Callback (SubjectMatchRule_function)
 // CHECK-NEXT: Capability (SubjectMatchRule_record, SubjectMatchRule_type_alias)
 // CHECK-NEXT: CarriesDependency (SubjectMatchRule_variable_is_parameter, SubjectMatchRule_objc_method, SubjectMatchRule_function)
+// CHECK-NEXT: ClangBuiltinOverride (SubjectMatchRule_function)
 // CHECK-NEXT: Cold (SubjectMatchRule_function)
 // CHECK-NEXT: Common (SubjectMatchRule_variable)
 // CHECK-NEXT: Constructor (SubjectMatchRule_function)