Basically Gunnar is correct. We look at the time stamp of the source file and compare it with the time stamp we had when the cache file was created (so the cache file data structure contains the time stamp of the original file). If there’s a difference, we’ll re-create the cache file. In addition there are various other checks that result in the cache file being re-created if the architecture differs, the Qt version changes or an internal version field is bumped for example. So no manual intervention should be needed.

What I also want to know regarding QML file caching: Is there a still performance boost if I already use Qt Quick Compiler?

第二次运行才能利用缓存信息：

The Qt Quick Compiler (commercial only in Qt 5.8) is for ahead of time compilation. It will make already the first run fast, with caching the benefits are from second run onwards.

http://blog.qt.io/blog/2017/01/23/qt-5-8-released/