[libcxx-commits] [libcxx] [libc++] Speed up set_intersection() by fast-forwarding over ranges of non-matching elements with one-sided binary search. (PR #75230)

[Louis Dionne via libcxx-commits]

================
@@ -38,10 +43,95 @@ struct __set_intersection_result {
       : __in1_(std::move(__in_iter1)), __in2_(std::move(__in_iter2)), __out_(std::move(__out_iter)) {}
 };
 
-template <class _AlgPolicy, class _Compare, class _InIter1, class _Sent1, class _InIter2, class _Sent2, class _OutIter>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __set_intersection_result<_InIter1, _InIter2, _OutIter>
+// Helper for __set_intersection() with one-sided binary search: populate result and advance input iterators if they
+// haven't advanced in the last 2 calls. This function is very intimately related to the way it is used and doesn't
+// attempt to abstract that, it's not appropriate for general usage outside of its context. It would be a lambda of
+// __set_intersection() if that hadn't stumped the compiler in c++03 mode in some platforms.
----------------
ldionne wrote:

```suggestion
// attempt to abstract that, it's not appropriate for general usage outside of its context.
```

https://github.com/llvm/llvm-project/pull/75230