[all-commits] [llvm/llvm-project] 2d1068: [libcxx] Optimize `ranges::fold_left_with_iter` fo...

[Connector Switch via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2d106844e76846073cdec161c4ab2b33497719db
      https://github.com/llvm/llvm-project/commit/2d106844e76846073cdec161c4ab2b33497719db
  Author: Connector Switch <c8ef at outlook.com>
  Date:   2026-02-05 (Thu, 05 Feb 2026)

  Changed paths:
    M libcxx/docs/ReleaseNotes/23.rst
    M libcxx/include/__algorithm/ranges_fold.h
    M libcxx/test/std/algorithms/alg.nonmodifying/alg.fold/left_folds.pass.cpp

  Log Message:
  -----------
  [libcxx] Optimize `ranges::fold_left_with_iter` for segmented iterators (#177853)

Part of https://github.com/llvm/llvm-project/issues/102817.

This patch attempts to optimize the performance of
`ranges::fold_left_with_iter` for segmented iterators.

- before

```
# | rng::fold_left(vector<int>)/8             2.78 ns         2.78 ns    241953718
# | rng::fold_left(vector<int>)/32            12.2 ns         12.2 ns     57579851
# | rng::fold_left(vector<int>)/50            19.2 ns         19.2 ns     36487764
# | rng::fold_left(vector<int>)/8192          3226 ns         3226 ns       216811
# | rng::fold_left(vector<int>)/1048576     441842 ns       441839 ns         1592
# | rng::fold_left(deque<int>)/8              2.83 ns         2.83 ns    243888678
# | rng::fold_left(deque<int>)/32             16.6 ns         16.6 ns     42297458
# | rng::fold_left(deque<int>)/50             22.3 ns         22.3 ns     31387998
# | rng::fold_left(deque<int>)/8192           2492 ns         2492 ns       281637
# | rng::fold_left(deque<int>)/1048576      324936 ns       324936 ns         2154
# | rng::fold_left(list<int>)/8               2.54 ns         2.54 ns    275946635
# | rng::fold_left(list<int>)/32              16.2 ns         16.2 ns     42901634
# | rng::fold_left(list<int>)/50              54.7 ns         54.7 ns     12767450
# | rng::fold_left(list<int>)/8192           15154 ns        15154 ns        56744
# | rng::fold_left(list<int>)/1048576      4976906 ns      4976867 ns          158
```

- after

```
# | rng::fold_left(vector<int>)/8             2.74 ns         2.74 ns    255954900
# | rng::fold_left(vector<int>)/32            12.1 ns         12.1 ns     57843462
# | rng::fold_left(vector<int>)/50            19.2 ns         19.2 ns     36422594
# | rng::fold_left(vector<int>)/8192          3202 ns         3202 ns       218265
# | rng::fold_left(vector<int>)/1048576     435718 ns       435709 ns         1609
# | rng::fold_left(deque<int>)/8              2.52 ns         2.52 ns    277288254
# | rng::fold_left(deque<int>)/32             14.1 ns         14.1 ns     52244463
# | rng::fold_left(deque<int>)/50             16.2 ns         16.2 ns     43131857
# | rng::fold_left(deque<int>)/8192           1695 ns         1695 ns       415620
# | rng::fold_left(deque<int>)/1048576      277729 ns       277731 ns         2532
# | rng::fold_left(list<int>)/8               2.55 ns         2.55 ns    277025050
# | rng::fold_left(list<int>)/32              16.2 ns         16.2 ns     43058857
# | rng::fold_left(list<int>)/50              54.7 ns         54.7 ns     12705516
# | rng::fold_left(list<int>)/8192           15236 ns        15235 ns        56840
# | rng::fold_left(list<int>)/1048576      4827263 ns      4827147 ns          152
```



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications