Those vary widely too, depending on what (and more importantly, how many) object shapes they see. They'll be roughly the same cost in Ignition and Sparkplug though, since they effectively call the same handlers for those loads (and way faster in TurboFan, since that one then can generate optimised code tailored to that type feedback)
Oh, so code that's entirely dominated by property loads will be much slower in Sparkplug than in TurboFan, by a factor of more than that 4×, perhaps closer to the 32× I was SWAGging for Ignition's overall relative slowdown? I guess at this point I ought to be running microbenchmarks instead of asking you to do it for me... ;)
Sorry, the 4x was my estimate of Ignition vs. Sparkplug (I guess it's closer to Iain's estimate of 2-4x). Sparkplug vs. TurboFan is crazy workload dependent. For microbenchmark-y tight loops, integer attorneys, and clean single-shape ("monomorphic") property loads, TurboFan is orders of magnitude faster. For small functions that just have non-inlineable function calls and heavily polymorphic property loads (with lots of shapes so you can't skip the property lookup), like you see in a lot of web code, they're close to on-par (because there's nothing TF can optimise away). If you put a gun to my head, I'd say it's on "average" maybe 10x? Very much a Fermi approximation though.
