[Support] Fix llvm::unique_function when building with GCC 4.9 by

introducing llvm::trivially_{copy,move}_constructible type traits.

This uses a completely portable implementation of these traits provided
by Richard Smith. You can see it on compiler explorer in all its glory:

  https://godbolt.org/g/QEDZjW

I have transcribed it, clang-formatted it, added some comments, and made
the tests fit into a unittest file.

I have also switched llvm::unique_function over to use these new, much
more portable traits. =D

Hopefully this will fix the build bot breakage from my prior commit.

llvm-svn: 336161

2 files changed, 78 insertions, 0 deletions

diff --git a/llvm/unittests/Support/CMakeLists.txt b/llvm/unittests/Support/CMakeLists.txt
index 655ca7fb9b4..852180c5cf9 100644
--- a/llvm/unittests/Support/CMakeLists.txt
+++ b/llvm/unittests/Support/CMakeLists.txt
@@ -59,6 +59,7 @@ add_llvm_unittest(SupportTests
   Threading.cpp
   TimerTest.cpp
   TypeNameTest.cpp
+  TypeTraitsTest.cpp
   TrailingObjectsTest.cpp
   TrigramIndexTest.cpp
   UnicodeTest.cpp
diff --git a/llvm/unittests/Support/TypeTraitsTest.cpp b/llvm/unittests/Support/TypeTraitsTest.cpp
new file mode 100644
index 00000000000..06ff9cc7b28
--- /dev/null
+++ b/llvm/unittests/Support/TypeTraitsTest.cpp
@@ -0,0 +1,77 @@
+//===- TypeTraitsTest.cpp -------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/type_traits.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 __clang__ || _MSC_VER || __GNUC__ > 5
+  // 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>();
+
+} // namespace triviality
+
+} // end anonymous namespace