Clang compiles much slower and bigger Firefox binaries than GCC 8/9 (opens in new tab)

Yes. Editorializing like that breaks the site guidelines: https://news.ycombinator.com/newsguidelines.html. That led a bunch of users to correctly flag this post, which meant that https://news.ycombinator.com/item?id=18794382 made the front page even if it was posted later.

We've moved most of the comments from this thread into that one.

Indeed, and "much slower" is somewhat ambiguous as its a lot more nuanced than that based on what I've read so far. I know Firefox switched to clang+llvm for more reasons than just "binary size and program speed" alone.