From b39f437757967687dd60d9d5a657cc3b421cf83d Mon Sep 17 00:00:00 2001
From: Chris Bieneman <chris.bieneman@me.com>
Date: Mon, 28 Mar 2022 16:33:16 -0500
Subject: [PATCH] [ADT] add initializer list specialization for is_contained

Adding an initializer list specialization for is_contained allows for
compile-time evaluation when called with a constant or runtime
evaluation for non-constant values.

This patch doesn't add any uses of this template, but that is coming in
a subsequent patch.

Reviewed By: pete

Differential Revision: https://reviews.llvm.org/D122079
---
 llvm/include/llvm/ADT/STLExtras.h    |  9 +++++++++
 llvm/unittests/ADT/STLExtrasTest.cpp | 25 +++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index ff2145e6861e..75d717545358 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -1657,6 +1657,15 @@ bool is_contained(R &&Range, const E &Element) {
   return std::find(adl_begin(Range), adl_end(Range), Element) != adl_end(Range);
 }
 
+template <typename T>
+constexpr bool is_contained(std::initializer_list<T> Set, T Value) {
+  // 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
index 6d4325e49f36..09ff556f3ea1 100644
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -964,4 +964,29 @@ TEST(STLExtrasTest, TypeAtIndex) {
       (std::is_same<double, llvm::TypeAtIndex<2, int, float, double>>::value));
 }
 
+enum Doggos {
+  Floofer,
+  Woofer,
+  SubWoofer,
+  Pupper,
+  Pupperino,
+  Longboi,
+};
+
+TEST(STLExtrasTest, IsContainedInitializerList) {
+  EXPECT_TRUE(is_contained({Woofer, SubWoofer}, Woofer));
+  EXPECT_TRUE(is_contained({Woofer, SubWoofer}, SubWoofer));
+  EXPECT_FALSE(is_contained({Woofer, SubWoofer}, Pupper));
+  EXPECT_FALSE(is_contained({}, Longboi));
+
+  static_assert(is_contained({Woofer, SubWoofer}, SubWoofer), "SubWoofer!");
+  static_assert(!is_contained({Woofer, SubWoofer}, Pupper), "Missing Pupper!");
+
+  EXPECT_TRUE(is_contained({1, 2, 3, 4}, 3));
+  EXPECT_FALSE(is_contained({1, 2, 3, 4}, 5));
+
+  static_assert(is_contained({1, 2, 3, 4}, 3), "It's there!");
+  static_assert(!is_contained({1, 2, 3, 4}, 5), "It's not there :(");
+}
+
 } // namespace