[libcxx-commits] [libcxx] [libc++] Optimize ranges::for_each for iterating over __trees (PR #164405)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_SPECIALIZED_ALGORITHMS_H
+#define _LIBCPP___ALGORITHM_SPECIALIZED_ALGORITHMS_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// FIXME: This should really be an enum
+namespace _Algorithm {
+  struct __for_each {};
+} // namespace _Algorithm
+
+template <class, class>
+struct __iterator_pair {};
+
+template <class _Alg, class _Range>
+struct __specialized_algorithm {
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ldionne wrote:

I think this is something that can greatly simplify our optimizations for specific data structures. However, I'd like to see it introduced in a prior patch where we can refactor e.g. a `vector<bool>` operation.

https://github.com/llvm/llvm-project/pull/164405