It depends. GCC (the Google Closure Compiler) indeed does some transformations that will improve run-time performance, but it is not its forte, and definitely n

It depends. GCC (the Google Closure Compiler) indeed does some transformations that will improve run-time performance, but it is not its forte, and definitely not its primary goal. In the benchmarks of Scala.js [1], another compiler that uses GCC behind the scenes, we have shown that: * the GCC optimizer alone often introduces performance improvements (not always, and sometimes it worsens performance) * our optimizer does better than GCC on its own * the combination of both does not improve over using only our own optimizer Scala.js uses GCC essentially for its code size improvements, not for its impact on run-time performance. [1] https://www.scala-js.org/doc/internals/performance.html#in-production-mode-fullopt https://www.scala-js.org/doc/internals/performance.html#in-p...