llvm-project

9827440f - [libc++] Optimize ranges::{for_each, for_each_n} for segmented iterators (#132896)

[libc++] Optimize ranges::{for_each, for_each_n} for segmented iterators (#132896) Previously, the segmented iterator optimization was limited to `std::{for_each, for_each_n}`. This patch extends the optimization to `std::ranges::for_each` and `std::ranges::for_each_n`, ensuring consistent optimizations across these algorithms. This patch first generalizes the `std` algorithms by introducing a `Projection` parameter, which is set to `__identity` for the `std` algorithms. Then we let the `ranges` algorithms to directly call their `std` counterparts with a general `__proj` argument. Benchmarks demonstrate performance improvements of up to 21.4x for ``std::deque::iterator`` and 22.3x for ``join_view`` of ``vector<vector<char>>``. Addresses a subtask of #102817.