ios The time it takes to call a function in a for loop is gradually reduced

Question

The following is a screenshot of the code and time consumption. I called a C language function in a for loop. It took a long time at first, then the time consumption decreased with each call, and finally stabilized within a small range. How to explain this situation? Is it optimization of the iOS platform or something else? Thank you very much~

我想大声告诉你 · Answer

It should be related to method caching. You can understand this process from objc_msgSendmessage distribution.