bug#24012: 25.0.95; forward-comment backwards takes O(n^2)

[Leo Liu]

1. Use the attached file as an example, open it in emacs in ruby-mode
2. Move point to end of buffer and eval (forward-comment (- (point)))

The last step takes about 0.25 seconds on my MacBook 3 GHz Intel Core
i7. If you double the lines of comments, the time increase by 4 folds.

Any idea why forward-comment backwards is so slow?

Leo

tt.rb
Description: tt.rb