I wonder if there's anything that automatically defers collection within a loop and collects the garbage after the loop is exited. Something like Obj-C's old @autoreleasepool but inserted automatically. Static analysis has gotten so fancy that that might not be a terrible idea once you work out all the nuances (e.g. what if the loop is too short, nested loops, what happens when your entire program is a loop like game loops, etc). Could be the best of both worlds.

But generally I think it turns out that in refcounted GC systems you end up just knowing to not allocate/free in your hot loop or if you're doing it in a loop then it's probably not the thing your hot loop is dominated by.