replace all the method typeof() to cached method. fix test issues

[cnjimbo]

1、replace all the method typeof() to cached method. 2、 fix test issues

[dadhi]

@cnjimbo Thanks for cleaning up, now the scope is much more clear.

I am still hesitating to accept the PR - need to think it over, and ideally to compare new and old benchmarks.

If you can run the benchmarks yourself, it will likely to speed up my decision.

[cnjimbo]

@dadhi well, agree with you, the full benchmark is necessary. let me figure out a way to test it

[dadhi]

@cnjimbo The side question, seems like you're deep into the performance optimizations. Maybe you have some other ideas, small or big, regarding the FEC improvements? Honestly, I would not call myself an optimization expert, so I am very open to ideas.

[dadhi]

closing for now.