diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -1657,6 +1657,15 @@
   return std::find(adl_begin(Range), adl_end(Range), Element) != adl_end(Range);
 }
 
+template <typename T>
+constexpr bool is_contained(T value, std::initializer_list<T> set) {
+  // TODO: Use std::find when we switch to C++20.
+  for (T v : set)
+    if (v == value)
+      return true;
+  return false;
+}
+
 /// Wrapper function around std::is_sorted to check if elements in a range \p R
 /// are sorted with respect to a comparator \p C.
 template <typename R, typename Compare> bool is_sorted(R &&Range, Compare C) {
diff --git a/llvm/unittests/ADT/STLExtrasTest.cpp b/llvm/unittests/ADT/STLExtrasTest.cpp
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -964,4 +964,28 @@
       (std::is_same<double, llvm::TypeAtIndex<2, int, float, double>>::value));
 }
 
+enum Doggos {
+  Floofer,
+  Woofer,
+  SubWoofer,
+  Pupper,
+  Pupperino,
+  Longboi,
+};
+
+TEST(STLExtrasTest, IsContainedInitializerList) {
+  {
+    bool Val = is_contained(Woofer, {Woofer, SubWoofer});
+    ASSERT_TRUE(Val);
+  }
+  {
+    bool Val = is_contained(SubWoofer, {Woofer, SubWoofer});
+    ASSERT_TRUE(Val);
+  }
+  {
+    bool Val = is_contained(Pupper, {Woofer, SubWoofer});
+    ASSERT_FALSE(Val);
+  }
+}
+
 } // namespace