Notes on debugging HotSpot's JIT compilation (2023)

by lichtenbergeron 3/25/2024, 7:48:34 AM with 3 comments
  • by acimim_haon 3/26/2024, 9:21:19 AM

    I don't really see why:

      public class TestJIT {
    public static void main(String[] args) {
        for (int i = 0; i < 20_000; i++) {
            payload();
        }
    }

    public static int payload(int a, int b) {
        return a + b;
    }
  }
    shouldn't be optimized into a 'no-op'. The end-effect is the same.

  • by saagarjhaon 3/26/2024, 6:56:02 AM

    Excellent. Next time I’ll have something to refer to when making memes like this one: https://twitter.com/_saagarjha/status/1576961522936340480. Maybe I can avoid building OpenJDK too!

  • by dzaimaon 3/27/2024, 12:57:04 AM

    Some self-advertising of a linux tool I made which can display perf record data with Java JIT disassembly (doesn't need hsdis): https://github.com/dzaima/grr?tab=readme-ov-file#java-jit