The C++ language cannot be parsed with a context-free parser.
A large part of the build times, however, is due to optimizations.
In the early days, clang was much faster in compilation than gcc. Over the years, it has improved on optimization output but as a consequence has lost the compilation speed.
There are many examples for https://godbolt.org/ to show how much work the optimizer does. As example, the http://eigen.tuxfamily.org library relies on the optimizer to generate optimized code for all sorts of combinations of algorithms.
In the early days, clang was much faster in compilation than gcc. Over the years, it has improved on optimization output but as a consequence has lost the compilation speed.
There are many examples for https://godbolt.org/ to show how much work the optimizer does. As example, the http://eigen.tuxfamily.org library relies on the optimizer to generate optimized code for all sorts of combinations of algorithms.