I need to run the program in very fast speed,...
@user101931, you have to be a bit more specific about
More specific in sense of structure... For example, you have to serve an even very fast: react very quickly - with out delay - and calculate/compose a result very quickly. The next question is: do you want to take advantage of Espruino as a system and how easy it is to use? Speeding up an application is not a linear street: for some things there is no speed up, such as serially communicated. Going fully 'raw - C native - you may squeeze out a lot of power from an algorithm, but communicating the result takes a while and the overhead caused by the simplicity of use / application is only a few %.
What @Gordon means w/
it's always possible that the JS surrounding your inline C is slowing it down).
With a smart setup / combination of Espruino (JS) firmware combined w/ raw, native C programming - inline or as firmware extensions w/ own build - you can co really do great.