[libcxx-commits] [libcxx] [libc++] Tiny optimizations for is_permutation (PR #129565)

[Louis Dionne via libcxx-commits]

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@@ -79,31 +83,30 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __is_permutation_impl(
     _Proj1&& __proj1,
     _Proj2&& __proj2) {
   using _D1 = __iter_diff_t<_Iter1>;
+  using _Ref1 = typename iterator_traits<_Iter1>::reference;
+  using _Ref2 = typename iterator_traits<_Iter2>::reference;
+  __identity __ident;
 
   for (auto __i = __first1; __i != __last1; ++__i) {
     //  Have we already counted the number of *__i in [f1, l1)?
-    auto __match = __first1;
-    for (; __match != __i; ++__match) {
-      if (std::__invoke(__pred, std::__invoke(__proj1, *__match), std::__invoke(__proj1, *__i)))
-        break;
-    }
+    auto __match = std::find_if(__first1, __i, [&](_Ref1 __x) -> bool {
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ldionne wrote:

We should probably hold on to the result of `*__i`. Something like `_Ref1 __va = *__i`. This simplifies the code a bit and *might* be a bit faster depending on the kind of iterator.

https://github.com/llvm/llvm-project/pull/129565