diff --git a/libcxx/include/__string b/libcxx/include/__string
--- a/libcxx/include/__string
+++ b/libcxx/include/__string
@@ -140,15 +140,14 @@
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, value_type const*, size_type)) \
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::rfind(value_type const*, size_type, size_type) const) \
   _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(value_type const*, size_type, size_type)) \
-  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::basic_string(basic_string const&)) \
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, value_type const*)) \
-  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::basic_string(basic_string const&, std::allocator<_CharType> const&)) \
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_last_not_of(value_type const*, size_type, size_type) const) \
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::~basic_string()) \
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_first_not_of(value_type const*, size_type, size_type) const) \
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, size_type, value_type)) \
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::operator=(value_type)) \
   _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(value_type const*, size_type)) \
+  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init_copy_ctor_external(value_type const*, size_type)) \
   _Func(_LIBCPP_FUNC_VIS const _CharType& basic_string<_CharType>::at(size_type) const) \
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, value_type const*, size_type)) \
   _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_first_of(value_type const*, size_type, size_type) const) \
diff --git a/libcxx/include/string b/libcxx/include/string
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -1549,9 +1549,14 @@
     inline
     void __init(size_type __n, value_type __c);
 
-    // Slow path for the (inlined) copy constructor.
+    // Slow path for the (inlined) copy constructor for 'long' strings.
     // Always externally instantiated and not inlined.
     // Asserts that __s is zero terminated.
+    // The main reason for this function to exist is because for unstable, we
+    // want to allow inlining of the copy constructor. However, we don't want
+    // to call the __init() functions as those are marked as inline which may
+    // result in over-aggressive inlining by the compiler, where our aim is
+    // to only inline the fast path code directly in the ctor.
     void __init_copy_ctor_external(const value_type* __s, size_type __sz);
 
     template <class _InputIterator>
@@ -1902,7 +1907,10 @@
 void basic_string<_CharT, _Traits, _Allocator>::__init_copy_ctor_external(
     const value_type* __s, size_type __sz) {
   pointer __p;
-  if (__sz >= __min_cap) {
+  if (__sz < __min_cap) {
+    __p = __get_short_pointer();
+    __set_short_size(__sz);
+  } else {
     if (__sz > max_size())
       this->__throw_length_error();
     size_t __cap = __recommend(__sz);
@@ -1910,9 +1918,6 @@
     __set_long_pointer(__p);
     __set_long_cap(__cap + 1);
     __set_long_size(__sz);
-  } else {
-    __p = __get_short_pointer();
-    __set_short_size(__sz);
   }
   traits_type::copy(_VSTD::__to_address(__p), __s, __sz + 1);
 }