[Support] Remove llvm::is_trivially_{copy/move}_constructible

This restores D132311, which was reverted in
29c841c (Sep 2022) due to certain files
not buildable with GCC 7.3.0. The previous attempt was reverted by
6cd9608 (Dec 2020).

This time, GCC 7.3.0 has existing build errors for a long time due to
structured bindings for many files, e.g.

```
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:9098:13: error: cannot decompose class type ‘std::pair<llvm::Value*, const llvm::SCEV*>’: both it and it
s base class ‘std::pair<llvm::Value*, const llvm::SCEV*>’ have non-static data members
   for (auto [_, Stride] : Legal->getLAI()->getSymbolicStrides()) {
             ^~~~~~~~~~~
```

... and also some `error: duplicate initialization of` instances due to llvm/Transforms/IPO/Attributor.h.

---

GCC 7.5.0 has a bug that, without this change, certain `SmallVector` with a `std::pair` element type like `SmallVector<std::pair<Instruction * const, Info>, 0> X;` lead to spurious

```
/tmp/opt/gcc-7.5.0/include/c++/7.5.0/type_traits:878:48: error: constructor required before non-static data member for ‘...’ has been parsed
```

Switching to std::is_trivially_{copy/move}_constructible fixes the error.

Author: MaskRay

llvm/include/llvm/ADT/FunctionExtras.h

@@ -59,7 +59,7 @@ namespace detail {
 
 template <typename T>
 using EnableIfTrivial =
-    std::enable_if_t<llvm::is_trivially_move_constructible<T>::value &&
+    std::enable_if_t<std::is_trivially_move_constructible<T>::value &&
                      std::is_trivially_destructible<T>::value>;
 template <typename CallableT, typename ThisT>
 using EnableUnlessSameType =
@@ -99,11 +99,11 @@ template <typename ReturnT, typename... ParamTs> class UniqueFunctionBase {
   template <typename T> struct AdjustedParamTBase {
     static_assert(!std::is_reference<T>::value,
                   "references should be handled by template specialization");
-    using type = std::conditional_t<
-        llvm::is_trivially_copy_constructible<T>::value &&
-            llvm::is_trivially_move_constructible<T>::value &&
-            IsSizeLessThanThresholdT<T>::value,
-        T, T &>;
+    using type =
+        std::conditional_t<std::is_trivially_copy_constructible<T>::value &&
+                               std::is_trivially_move_constructible<T>::value &&
+                               IsSizeLessThanThresholdT<T>::value,
+                           T, T &>;
   };
 
   // This specialization ensures that 'AdjustedParam<V<T>&>' or

llvm/include/llvm/ADT/SmallVector.h

@@ -326,8 +326,8 @@ class SmallVectorTemplateCommon
 /// 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 = (is_trivially_copy_constructible<T>::value) &&
-                             (is_trivially_move_constructible<T>::value) &&
+template <typename T, bool = (std::is_trivially_copy_constructible<T>::value) &&
+                             (std::is_trivially_move_constructible<T>::value) &&
                              std::is_trivially_destructible<T>::value>
 class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
   friend class SmallVectorTemplateCommon<T>;

llvm/include/llvm/Support/type_traits.h

@@ -69,51 +69,13 @@ struct const_pointer_or_const_ref<T, std::enable_if_t<std::is_pointer_v<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 {
     T t;
 };
 
 } // 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>

llvm/unittests/Support/TypeTraitsTest.cpp

@@ -26,10 +26,10 @@ namespace triviality {
 template <typename T, bool IsTriviallyCopyConstructible,
           bool IsTriviallyMoveConstructible>
 void TrivialityTester() {
-  static_assert(llvm::is_trivially_copy_constructible<T>::value ==
+  static_assert(std::is_trivially_copy_constructible<T>::value ==
                     IsTriviallyCopyConstructible,
                 "Mismatch in expected trivial copy construction!");
-  static_assert(llvm::is_trivially_move_constructible<T>::value ==
+  static_assert(std::is_trivially_move_constructible<T>::value ==
                     IsTriviallyMoveConstructible,
                 "Mismatch in expected trivial move construction!");
 

mlir/lib/Dialect/SparseTensor/IR/Detail/TemplateExtras.h

@@ -75,8 +75,8 @@ static constexpr bool IsZeroCostAbstraction =
     // use memcpy.  The commentary there mentions that it's intended to be
     // an approximation of `is_trivially_copyable`, so this may be redundant
     // with the above, but we include it just to make sure.
-    llvm::is_trivially_copy_constructible<T>::value &&
-    llvm::is_trivially_move_constructible<T>::value;
+    std::is_trivially_copy_constructible<T>::value &&
+    std::is_trivially_move_constructible<T>::value;
 
 //===----------------------------------------------------------------------===//