llvm-project

46e88169 - [libcxx] Optimize std::generate for segmented iterators (#163006)

[libcxx] Optimize std::generate for segmented iterators (#163006) Part of #102817. This patch attempts to optimize the performance of `std::generate` for segmented iterators. Below are the benchmark numbers from `libcxx\test\benchmarks\algorithms\modifying\generate.bench.cpp`. Test cases that use segmented iterators have also been added. - before ``` std::generate(deque<int>)/32 194 ns 193 ns 3733333 std::generate(deque<int>)/50 276 ns 276 ns 2488889 std::generate(deque<int>)/1024 5096 ns 5022 ns 112000 std::generate(deque<int>)/8192 40806 ns 40806 ns 17231 ``` - after ``` std::generate(deque<int>)/32 106 ns 105 ns 6400000 std::generate(deque<int>)/50 139 ns 138 ns 4977778 std::generate(deque<int>)/1024 2713 ns 2699 ns 248889 std::generate(deque<int>)/8192 18983 ns 19252 ns 37333 ``` --------- Co-authored-by: A. Jiang <de34@live.cn>