Assembly Hall of Shame

(github.com)

122 points | by piotrgrabowski 2 hours ago

12 comments

  • layer8 1 hour ago
    Nop should be #1, because it is infinitely slow for what it does. ;)
    • jooops1 1 hour ago
      It increments rip by one.
    • mito88 43 minutes ago
      Strategy: nop does nothing. It opens the leaderboard accordingly.

      Score: 1 cycles Time: 0 nanoseconds

      • layer8 13 minutes ago
        It opens the leaderboard as #27, so in the last place.
  • Retr0id 1 hour ago
    Related, and linked in the readme: https://github.com/xoreaxeaxeax/smiiiiiiiiiiiiiiii (using the slow instructions to break SMI)
  • TomatoCo 2 hours ago
    This author also has other things like: A compiler that emits only `mov` instructions and another compiler that deliberately messes with the control flow so that, if disassembled, common debuggers will draw symbols like skulls or threats. https://github.com/xoreaxeaxeax/repsych
    • inigyou 51 minutes ago
      He also bruteforced the entire opcode space to find undocumented instructions (sandsifter).
  • spoocecow 1 hour ago
    Oh wow, glad to see Chris Domas active online again!
  • michalsustr 1 hour ago
    Very cool! Also, huh interesting. I’ve used rdtsc to measure cycle diffs but had no idea its execution takes that long. Is that common across architectures?
  • IshKebab 21 minutes ago
    Using MMIO is cheating and makes the results very boring.

    It would be much more interesting to know the results if you're only allowed to use main memory.

  • codeshaunted 2 hours ago
    what im seeing from this chart is that we should be using the nop instruction for everything
    • bee_rider 1 hour ago
      Well the best code is no code. Nop could be second best though.
      • inigyou 51 minutes ago
        Instructions unclear. Set the NX bit to ensure no code, and got a general protection fault.
  • vardump 2 hours ago
    A great resource for any performance deoptimization.
  • metadat 2 hours ago
    It’s crazy how computers still seem to get perceivably slow every few years, given how many instructions can be executed in 1ms. Shameful, even..

    What’s that law called about programmers wasting all the compute on abstraction?

    • mwigdahl 1 hour ago
      Wirth's Law I believe.
      • inigyou 49 minutes ago
        And remember to call him by name, not by value!
    • HappyPanacea 2 hours ago
      The new windows notepad is a disgrace
      • adamrezich 0 minutes ago
        The new mspaint fucked, then unfucked, then refucked my decades-old muscle memory of Win+R mspaint Enter Ctrl+E 1 Tab 1 Enter Ctrl+V to open Paint, resize canvas to minimum, then paste from clipboard. When you press Ctrl+E now, the Units control is selected by default, for some completely asinine reason!!!
    • inigyou 50 minutes ago
      Andy and Bill's Law
    • summarybot 1 hour ago
      The OS should do less not more
    • LoganDark 2 hours ago
      Huh? A millisecond is an eternity!
      • m463 1 hour ago
        I remember reading once somewhere:

        If some app responds in 10ms or less, it is INTERACTIVE.

        makes you think.

        • Xirdus 42 minutes ago
          It is literally impossible to respond to input in 10ms on most platforms, for various reasons. The USB input lag of 12-30ms and the 60Hz refresh rate of most monitors being just the first two.
  • arn3n 2 hours ago
    There’s definitely strategies here; A lot of the floating point operations use subnormals, and a lot of the worst instructions are slowed down by really, really fucking with MMIO.
  • achierius 2 hours ago
    It'd be really interesting to see whether the winning (losing?) instructions/strategies would be different on other architectures. At least right now the top spot (`fxrstor64` on MMIO, starve PCIe) seems relatively architecture-independent, but maybe something about MMIO ordering rules on e.g. POWER would be different enough to change that -- or perhaps open up new avenues?

    I wonder what the actual limit on this `fxrstor64` is right now. If you can stall the PCIe bus for that long, then why not indefinitely? Certainly there's no forward progress guarantee here.

  • 2_foos_in_a_bar 2 hours ago
    [dead]