[libcxx-commits] [PATCH] D112152: [libc++] Unroll loop in std::find_if and define other std::find variants in terms of it

[Mark de Wever via Phabricator via libcxx-commits]

Mordante added inline comments.


================
Comment at: libcxx/test/std/algorithms/alg.nonmodifying/alg.find/find_if.pass.cpp:62
 
+int main(int, char**) {
+  test();
----------------
Quuxplusone wrote:
> Mordante wrote:
> > Since the algorithm is no longer straight forward I think it would be good to validate the number of times the predicate is evaluated. Just to make sure we didn't accidentally increase the number of evaluations.
> +1, I think your current implementation has 4 instances of `break` that should be `return __first`, and this causes 1 extra evaluation of `__pred` in most cases.
I too wondered about why not a `return` instead of a `break`. Initially I also expected one extra evaluation, but upon further studying the algorithm I _think_ it's correct. `switch (__last - __first)` should be larger than 3 when the `for` loop exits in one of the `break`s.


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  https://reviews.llvm.org/D112152/new/

https://reviews.llvm.org/D112152