tracking issue for strip_prefix, strip_suffix for str

[Dylan-DPC-zz]

Cc @KodrAus

Will fill the content later. Creating this so that #66735 can be merged and tracked.

[tesuji]

The code generated by str::strip_prefix is really complicated and inefficient.
Godbolt link: https://rust.godbolt.org/z/AnEoHH
Should we add strip_prefix / strip_suffix method directly to Pattern or Searcher trait?

[CryZe]

Oof that does indeed look pretty bad.

[benesch]

I whipped up that fix here: #69784

Not sure if it's actually the ideal fix, but figured it would be a good point to launch the discussion from.

[benesch]

Ok, the code should be far more optimized now. What remains to be done? The main issue description has yet to be filled in. 😄

[lights0123]

On some criterion benchmarks that I did, I'm seeing that

fn strip_suffix(input: &str) -> &str {
	input.strip_suffix(char::is_whitespace).unwrap_or(input)
}

is much faster than trim_end, at least for newlines only. Is this only because I'm stripping off a very small amount of text, or is this function more optimized than trim_end (assuming that I didn't screw something up)? See "Standard strip suffix" versus "Standard trim end", with "unix" having the input of "50\n" and "win" being "50\r\n":