diff --git a/clang/include/clang/Basic/Builtins.def b/clang/include/clang/Basic/Builtins.def
index d388afe7fae6ef..1a6c85ce2dd368 100644
--- a/clang/include/clang/Basic/Builtins.def
+++ b/clang/include/clang/Basic/Builtins.def
@@ -788,6 +788,9 @@ BUILTIN(__builtin_abort, "v", "Fnr")
 BUILTIN(__builtin_index, "c*cC*i", "Fn")
 BUILTIN(__builtin_rindex, "c*cC*i", "Fn")
 
+// ignored glibc builtin, see https://sourceware.org/bugzilla/show_bug.cgi?id=25399
+BUILTIN(__warn_memset_zero_len, "v", "nU")
+
 // Microsoft builtins.  These are only active with -fms-extensions.
 LANGBUILTIN(_alloca,          "v*z", "n", ALL_MS_LANGUAGES)
 LANGBUILTIN(__annotation,     "wC*.","n", ALL_MS_LANGUAGES)
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 09fd3087b494a1..2d20f92fbb3d23 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -3222,6 +3222,8 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
         Builder.CreateZExt(EmitSignBit(*this, EmitScalarExpr(E->getArg(0))),
                            ConvertType(E->getType())));
   }
+  case Builtin::BI__warn_memset_zero_len:
+    return RValue::getIgnored();
   case Builtin::BI__annotation: {
     // Re-encode each wide string to UTF8 and make an MDString.
     SmallVector<Metadata *, 1> Strings;
diff --git a/clang/test/CodeGen/builtins.c b/clang/test/CodeGen/builtins.c
index 591416d00cc7f0..9f2a74f6c873e4 100644
--- a/clang/test/CodeGen/builtins.c
+++ b/clang/test/CodeGen/builtins.c
@@ -453,6 +453,13 @@ void test_builtin_launder(int *p) {
   int *d = __builtin_launder(p);
 }
 
+// __warn_memset_zero_len should be NOP, see https://sourceware.org/bugzilla/show_bug.cgi?id=25399
+// CHECK-LABEL: define void @test___warn_memset_zero_len
+void test___warn_memset_zero_len() {
+  // CHECK-NOT: @__warn_memset_zero_len
+  __warn_memset_zero_len();
+}
+
 // Behavior of __builtin_os_log differs between platforms, so only test on X86
 #ifdef __x86_64__