Not really, this depends on the code being compiled/run, e.g.: http://www.phoronix.com/scan.php?page=article&item=gcc7-clang4-jan&num=2 http://www.phoronix.com/

Not really, this depends on the code being compiled/run, e.g.: http://www.phoronix.com/scan.php?page=article&item=gcc7-clang4-jan&num=2 http://www.phoronix.com/scan.php?page=article&item=gcc7-clan... GCC however has many more platforms supported, so in certain use cases LLVM is out of the question entirely. That being said: for OS development (and many other projects) predictable and correct is more important than fast. Optimizations that lead to these performance gains are oftentimes harmful given that code is typically far from perfect.