Revert "Switch to std::is_trivially_move_constructible and std::is_trivially_copy_constructible"

This reverts commit c8d406c93c5bb01599990201f78d8428dd29d289.

Builds are broken with some versions of GCC.

include/llvm/ADT/FunctionExtras.h

@@ -57,7 +57,7 @@ namespace detail {
 
 template <typename T>
 using EnableIfTrivial =
-    std::enable_if_t<std::is_trivially_move_constructible<T>::value &&
+    std::enable_if_t<llvm::is_trivially_move_constructible<T>::value &&
                      std::is_trivially_destructible<T>::value>;
 
 template <typename ReturnT, typename... ParamTs> class UniqueFunctionBase {
@@ -83,8 +83,8 @@ protected:
   template <typename T>
   using AdjustedParamT = typename std::conditional<
       !std::is_reference<T>::value &&
-          std::is_trivially_copy_constructible<T>::value &&
-          std::is_trivially_move_constructible<T>::value &&
+          llvm::is_trivially_copy_constructible<T>::value &&
+          llvm::is_trivially_move_constructible<T>::value &&
           IsSizeLessThanThresholdT<T>::value,
       T, T &>::type;
 

include/llvm/ADT/SmallVector.h

@@ -278,8 +278,8 @@ public:
 /// copy these types with memcpy, there is no way for the type to observe this.
 /// This catches the important case of std::pair<POD, POD>, which is not
 /// trivially assignable.
-template <typename T, bool = (std::is_trivially_copy_constructible<T>::value) &&
-                             (std::is_trivially_move_constructible<T>::value) &&
+template <typename T, bool = (is_trivially_copy_constructible<T>::value) &&
+                             (is_trivially_move_constructible<T>::value) &&
                              std::is_trivially_destructible<T>::value>
 class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
 protected:

include/llvm/Support/type_traits.h

@@ -70,6 +70,20 @@ struct const_pointer_or_const_ref<T,
 };
 
 namespace detail {
+/// Internal utility to detect trivial copy construction.
+template<typename T> union copy_construction_triviality_helper {
+    T t;
+    copy_construction_triviality_helper() = default;
+    copy_construction_triviality_helper(const copy_construction_triviality_helper&) = default;
+    ~copy_construction_triviality_helper() = default;
+};
+/// Internal utility to detect trivial move construction.
+template<typename T> union move_construction_triviality_helper {
+    T t;
+    move_construction_triviality_helper() = default;
+    move_construction_triviality_helper(move_construction_triviality_helper&&) = default;
+    ~move_construction_triviality_helper() = default;
+};
 
 template<class T>
 union trivial_helper {
@@ -78,6 +92,29 @@ union trivial_helper {
 
 } // end namespace detail
 
+/// An implementation of `std::is_trivially_copy_constructible` since we have
+/// users with STLs that don't yet include it.
+template <typename T>
+struct is_trivially_copy_constructible
+    : std::is_copy_constructible<
+          ::llvm::detail::copy_construction_triviality_helper<T>> {};
+template <typename T>
+struct is_trivially_copy_constructible<T &> : std::true_type {};
+template <typename T>
+struct is_trivially_copy_constructible<T &&> : std::false_type {};
+
+/// An implementation of `std::is_trivially_move_constructible` since we have
+/// users with STLs that don't yet include it.
+template <typename T>
+struct is_trivially_move_constructible
+    : std::is_move_constructible<
+          ::llvm::detail::move_construction_triviality_helper<T>> {};
+template <typename T>
+struct is_trivially_move_constructible<T &> : std::true_type {};
+template <typename T>
+struct is_trivially_move_constructible<T &&> : std::true_type {};
+
+
 template <typename T>
 struct is_copy_assignable {
   template<class F>

unittests/Support/CMakeLists.txt

@@ -80,6 +80,7 @@ add_llvm_unittest(SupportTests
   TimerTest.cpp
   ToolOutputFileTest.cpp
   TypeNameTest.cpp
+  TypeTraitsTest.cpp
   TrailingObjectsTest.cpp
   TrigramIndexTest.cpp
   UnicodeTest.cpp

unittests/Support/TypeTraitsTest.cpp

@@ -0,0 +1,97 @@
+//===- TypeTraitsTest.cpp -------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/type_traits.h"
+#include "gtest/gtest.h"
+
+namespace {
+
+// Compile-time tests using static assert.
+namespace triviality {
+
+// Helper for compile time checking trivially copy constructible and trivially
+// move constructible type traits.
+template <typename T, bool IsTriviallyCopyConstructible,
+          bool IsTriviallyMoveConstructible>
+void TrivialityTester() {
+  static_assert(llvm::is_trivially_copy_constructible<T>::value ==
+                    IsTriviallyCopyConstructible,
+                "Mismatch in expected trivial copy construction!");
+  static_assert(llvm::is_trivially_move_constructible<T>::value ==
+                    IsTriviallyMoveConstructible,
+                "Mismatch in expected trivial move construction!");
+
+#if defined(_LIBCPP_VERSION) || defined(_MSC_VER)
+  // On compilers with support for the standard traits, make sure they agree.
+  static_assert(std::is_trivially_copy_constructible<T>::value ==
+                    IsTriviallyCopyConstructible,
+                "Mismatch in expected trivial copy construction!");
+  static_assert(std::is_trivially_move_constructible<T>::value ==
+                    IsTriviallyMoveConstructible,
+                "Mismatch in expected trivial move construction!");
+#endif
+}
+
+template void TrivialityTester<int, true, true>();
+template void TrivialityTester<void *, true, true>();
+template void TrivialityTester<int &, true, true>();
+template void TrivialityTester<int &&, false, true>();
+
+struct X {};
+struct Y {
+  Y(const Y &);
+};
+struct Z {
+  Z(const Z &);
+  Z(Z &&);
+};
+struct A {
+  A(const A &) = default;
+  A(A &&);
+};
+struct B {
+  B(const B &);
+  B(B &&) = default;
+};
+
+template void TrivialityTester<X, true, true>();
+template void TrivialityTester<Y, false, false>();
+template void TrivialityTester<Z, false, false>();
+template void TrivialityTester<A, true, false>();
+template void TrivialityTester<B, false, true>();
+
+template void TrivialityTester<Z &, true, true>();
+template void TrivialityTester<A &, true, true>();
+template void TrivialityTester<B &, true, true>();
+template void TrivialityTester<Z &&, false, true>();
+template void TrivialityTester<A &&, false, true>();
+template void TrivialityTester<B &&, false, true>();
+
+TEST(Triviality, Tester) {
+  TrivialityTester<int, true, true>();
+  TrivialityTester<void *, true, true>();
+  TrivialityTester<int &, true, true>();
+  TrivialityTester<int &&, false, true>();
+
+  TrivialityTester<X, true, true>();
+  TrivialityTester<Y, false, false>();
+  TrivialityTester<Z, false, false>();
+  TrivialityTester<A, true, false>();
+  TrivialityTester<B, false, true>();
+
+  TrivialityTester<Z &, true, true>();
+  TrivialityTester<A &, true, true>();
+  TrivialityTester<B &, true, true>();
+  TrivialityTester<Z &&, false, true>();
+  TrivialityTester<A &&, false, true>();
+  TrivialityTester<B &&, false, true>();
+}
+
+} // namespace triviality
+
+} // end anonymous namespace

utils/gn/secondary/llvm/unittests/Support/BUILD.gn

@@ -85,6 +85,7 @@ unittest("SupportTests") {
     "TrailingObjectsTest.cpp",
     "TrigramIndexTest.cpp",
     "TypeNameTest.cpp",
+    "TypeTraitsTest.cpp",
     "UnicodeTest.cpp",
     "VersionTupleTest.cpp",
     "VirtualFileSystemTest.cpp",