[libcxx-commits] [libcxx] [libc++] Implement single element vector::insert in terms of emplace (PR #210284)

[Louis Dionne via libcxx-commits]

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@@ -1181,6 +1144,18 @@ vector<_Tp, _Allocator>::emplace(const_iterator __position, _Args&&... __args) {
     if (__p == __end) {
       __emplace_back_assume_capacity(std::forward<_Args>(__args)...);
     } else {
+#ifndef _LIBCPP_CXX03_LANG
+      if constexpr (sizeof...(_Args) == 1) {
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ldionne wrote:

Let's add a comment like `// If we insert a single element that is the same as the value type, avoid creating a temporary`.

https://github.com/llvm/llvm-project/pull/210284