Take the Darwin version linked from your site. Run *perf record wc thefile.txt*....

danieldk on Nov 21, 2019 | parent | context | favorite | on: Beating C with 70 lines of Go

Take the Darwin version linked from your site. Run perf record wc thefile.txt. Then run perf report and you will see iswspace in the call graph.

As I show in [1], removing this call and replacing it by a character match, gives a speedup of almost 2x.

[1] https://news.ycombinator.com/item?id=21592089