I have a hard time finding a website or any document which shows which builtin functions or features are available for a specific MSVC version.

I am personally not using MSVC but my program should be able to be compiled using MSVC. For example GNU C compilers implement __builtin_unreachable() function and MSVC to my knowledge also implements __assume().

Now how would I know which version of MSVC has this builtin function so that I can use macro directives to enable it? Additionally same for GCC I have hard time finding which version supports which builtin functions or features, but at least it was quite easy to find GCC changelogs (which are not ideal many things are not documented or are missing).