libstdc++: Optimize __make_comp/pred_proj for empty/scalar types

When creating a composite comparator/predicate that invokes a given
projection function, we don't need to capture a scalar (such as a
function pointer or member pointer) or empty object by reference,
instead capture it by value and use [[no_unique_address]] to elide
its storage (in the empty case).  This makes using __make_comp_proj
zero-cost in the common case where both functions are empty/scalars.

libstdc++-v3/ChangeLog:

	* include/bits/ranges_algo.h (__detail::__by_ref_or_value_fn): New.
	(__detail::_Comp_proj): New.
	(__detail::__make_comp_proj): Use it instead.
	(__detail::_Pred_proj): New.
	(__detail::__make_pred_proj): Use it instead.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

0 files changed, 0 insertions, 0 deletions