[PATCH] libstdc++: Also disable caching of reverse_view::begin() for common_ranges

[Patrick Palka]

When the underlying range models common_range, then reverse_view::begin() is
O(1) without caching.  So we should disable the cache in this case too.

libstdc++-v3/ChangeLog:

        * include/std/ranges (reverse_view::_S_needs_cached_begin): Set to false
        whenever the underlying range models common_range.
---
 libstdc++-v3/include/std/ranges | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 2f773130979..19d3da950e7 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -3177,7 +3177,8 @@ namespace views
     private:
       _Vp _M_base = _Vp();
 
-      static constexpr bool _S_needs_cached_begin = !random_access_range<_Vp>;
+      static constexpr bool _S_needs_cached_begin
+       = !common_range<_Vp> && !random_access_range<_Vp>;
       [[no_unique_address]]
        __detail::__maybe_empty_t<_S_needs_cached_begin,
                                  __detail::_CachedPosition<_Vp>> 
_M_cached_begin;
-- 
2.25.1.377.g2d2118b814