[committed] libstdc++: Simplify std::basic_regex::assign

[Jonathan Wakely via Gcc-patches]

We know that if __is_contiguous_iterator is true then we have a pointer
or a __normal_iterator that wraps a pointer, so we don't need to use
std::__to_address.

libstdc++-v3/ChangeLog:

        * include/bits/regex.h (basic_regex::assign(Iter, Iter)): Avoid
        std::__to_address by using poitner directly or using base()
        member of __normal_iterator.

Tested powerpc64le-linux. Committed to trunk.


commit 247bac507e63b32d4dc23ef1c55f300aafea24c6
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Mon Oct 11 17:19:43 2021

    libstdc++: Simplify std::basic_regex::assign
    
    We know that if __is_contiguous_iterator is true then we have a pointer
    or a __normal_iterator that wraps a pointer, so we don't need to use
    std::__to_address.
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/regex.h (basic_regex::assign(Iter, Iter)): Avoid
            std::__to_address by using poitner directly or using base()
            member of __normal_iterator.

diff --git a/libstdc++-v3/include/bits/regex.h 
b/libstdc++-v3/include/bits/regex.h
index 3c44bcd7e33..a3990183580 100644
--- a/libstdc++-v3/include/bits/regex.h
+++ b/libstdc++-v3/include/bits/regex.h
@@ -682,15 +682,16 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        assign(_InputIterator __first, _InputIterator __last,
               flag_type __flags = ECMAScript)
        {
-#if __cplusplus >= 201703L
+#if __cpp_if_constexpr >= 201606L
          using _ValT = typename iterator_traits<_InputIterator>::value_type;
          if constexpr (__detail::__is_contiguous_iter<_InputIterator>::value
                        && is_same_v<_ValT, value_type>)
            {
              __glibcxx_requires_valid_range(__first, __last);
-             const auto __len = __last - __first;
-             const _Ch_type* __p = std::__to_address(__first);
-             _M_compile(__p, __p + __len, __flags);
+             if constexpr (is_pointer_v<_InputIterator>)
+               _M_compile(__first, __last, __flags);
+             else // __normal_iterator<_T*, C>
+               _M_compile(__first.base(), __last.base(), __flags);
            }
          else
 #endif