[libc++] Accept iterators instead of raw pointers in __uninitialized_allocator_relocate

[ldionne]

This generalizes the algorithm a bit. Unfortunately, we can't make
the call sites cleaner inside std::vector because the arguments being
passed can all be fancy pointers, which may not be contiguous iterators.

[ldionne]

CC @philnik777

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Louis Dionne (ldionne)

Changes

This makes the call sites of the function a lot cleaner.

---

Full diff: https://github.com/llvm/llvm-project/pull/114552.diff

2 Files Affected:

• (modified) libcxx/include/__memory/uninitialized_algorithms.h (+16-12)
• (modified) libcxx/include/__vector/vector.h (+3-6)

diff --git a/libcxx/include/__memory/uninitialized_algorithms.h b/libcxx/include/__memory/uninitialized_algorithms.h
index 3fa948ecc43cff..9abc6bd2bcd2c3 100644
--- a/libcxx/include/__memory/uninitialized_algorithms.h
+++ b/libcxx/include/__memory/uninitialized_algorithms.h
@@ -611,20 +611,22 @@ struct __allocator_has_trivial_destroy<allocator<_Tp>, _Up> : true_type {};
 //                 [__first, __last) doesn't contain any objects
 //
 // The strong exception guarantee is provided if any of the following are true:
-// - is_nothrow_move_constructible<_Tp>
-// - is_copy_constructible<_Tp>
-// - __libcpp_is_trivially_relocatable<_Tp>
-template <class _Alloc, class _Tp>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
-__uninitialized_allocator_relocate(_Alloc& __alloc, _Tp* __first, _Tp* __last, _Tp* __result) {
+// - is_nothrow_move_constructible<_ValueType>
+// - is_copy_constructible<_ValueType>
+// - __libcpp_is_trivially_relocatable<_ValueType>
+template <class _Alloc, class _ContiguousIterator>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void __uninitialized_allocator_relocate(
+    _Alloc& __alloc, _ContiguousIterator __first, _ContiguousIterator __last, _ContiguousIterator __result) {
+  static_assert(__libcpp_is_contiguous_iterator<_ContiguousIterator>::value, "");
+  using _ValueType = typename iterator_traits<_ContiguousIterator>::value_type;
   static_assert(__is_cpp17_move_insertable<_Alloc>::value,
                 "The specified type does not meet the requirements of Cpp17MoveInsertable");
-  if (__libcpp_is_constant_evaluated() || !__libcpp_is_trivially_relocatable<_Tp>::value ||
-      !__allocator_has_trivial_move_construct<_Alloc, _Tp>::value ||
-      !__allocator_has_trivial_destroy<_Alloc, _Tp>::value) {
+  if (__libcpp_is_constant_evaluated() || !__libcpp_is_trivially_relocatable<_ValueType>::value ||
+      !__allocator_has_trivial_move_construct<_Alloc, _ValueType>::value ||
+      !__allocator_has_trivial_destroy<_Alloc, _ValueType>::value) {
     auto __destruct_first = __result;
-    auto __guard =
-        std::__make_exception_guard(_AllocatorDestroyRangeReverse<_Alloc, _Tp*>(__alloc, __destruct_first, __result));
+    auto __guard          = std::__make_exception_guard(
+        _AllocatorDestroyRangeReverse<_Alloc, _ValueType*>(__alloc, __destruct_first, __result));
     auto __iter = __first;
     while (__iter != __last) {
 #if _LIBCPP_HAS_EXCEPTIONS
@@ -639,7 +641,9 @@ __uninitialized_allocator_relocate(_Alloc& __alloc, _Tp* __first, _Tp* __last, _
     std::__allocator_destroy(__alloc, __first, __last);
   } else {
     // Casting to void* to suppress clang complaining that this is technically UB.
-    __builtin_memcpy(static_cast<void*>(__result), __first, sizeof(_Tp) * (__last - __first));
+    __builtin_memcpy(static_cast<void*>(std::__to_address(__result)),
+                     std::__to_address(__first),
+                     sizeof(_ValueType) * (__last - __first));
   }
 }
 
diff --git a/libcxx/include/__vector/vector.h b/libcxx/include/__vector/vector.h
index 844e5d6a210568..c4c37cbe839b73 100644
--- a/libcxx/include/__vector/vector.h
+++ b/libcxx/include/__vector/vector.h
@@ -737,8 +737,7 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void
 vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, allocator_type&>& __v) {
   __annotate_delete();
   auto __new_begin = __v.__begin_ - (__end_ - __begin_);
-  std::__uninitialized_allocator_relocate(
-      __alloc(), std::__to_address(__begin_), std::__to_address(__end_), std::__to_address(__new_begin));
+  std::__uninitialized_allocator_relocate(__alloc(), __begin_, __end_, __new_begin);
   __v.__begin_ = __new_begin;
   __end_       = __begin_; // All the objects have been destroyed by relocating them.
   std::swap(this->__begin_, __v.__begin_);
@@ -760,14 +759,12 @@ vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, a
 
   // Relocate [__p, __end_) first to avoid having a hole in [__begin_, __end_)
   // in case something in [__begin_, __p) throws.
-  std::__uninitialized_allocator_relocate(
-      __alloc(), std::__to_address(__p), std::__to_address(__end_), std::__to_address(__v.__end_));
+  std::__uninitialized_allocator_relocate(__alloc(), __p, __end_, __v.__end_);
   __v.__end_ += (__end_ - __p);
   __end_           = __p; // The objects in [__p, __end_) have been destroyed by relocating them.
   auto __new_begin = __v.__begin_ - (__p - __begin_);
 
-  std::__uninitialized_allocator_relocate(
-      __alloc(), std::__to_address(__begin_), std::__to_address(__p), std::__to_address(__new_begin));
+  std::__uninitialized_allocator_relocate(__alloc(), __begin_, __p, __new_begin);
   __v.__begin_ = __new_begin;
   __end_       = __begin_; // All the objects have been destroyed by relocating them.