Well, in C memory is explicitly laid out, so it's not on the optimizer's menu, and in a dynamic language the runtime flexibility rules out most data-layout opti

Well, in C memory is explicitly laid out, so it's not on the optimizer's menu, and in a dynamic language the runtime flexibility rules out most data-layout optimizations beyond occasionally coalescing a dictionary into a memory-offset-based buffer. There's some experimental game languages like JAI which include these semantics as a language primitive, but it's still declared rather than implied. Fundamentally, data layout is design because it depends on actual game content, and not just code; it's categorically different than code optimization.