8.6 Performance optimizations

Obtaining a smooth IDE experience with accurate results provided without visible delays is a challenging task. One of the ways to achieve this experience is through compiler performance optimization, as good navigation can be provided with well-parsed source code. Clangd offers excellent examples of performance optimization, which we will explore in some detail. We will start with the optimizations for code modifications.

8.6.1 Optimizations for modified documents

As we saw in Line 4, Open document, navigation support requires the AST as the basic data structure, so we have to use the Clang frontend to obtain it. Additionally, we have to rebuild the AST when there are document modifications. Document modification is a common activity for developers, and we won’t be able to provide a good IDE experience if we always start the build process from scratch.

Source code preamble

To gain insights into the ideas used to speed up AST building for...