JIT languages tend to have the worst language-provided locality as they are often accompanied by GCs and lack of value types (there are exceptions to this, but it's broadly the case). And a JIT cannot re-arrange heap memory layout of objects as it must be hot-swappable. This is why despite incredibly huge investments in them such languages just never reach aot performance despite how much theoretical advantage a jit could have.
AOT'd languages could re-arrange a struct for better locality however the majority (if not all) languages rigidly require the fields are laid out in the order defined for various reasons.
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JIT languages tend to have the worst language-provided locality as they are often accompanied by GCs and lack of value types (there are exceptions to this, but it's broadly the case). And a JIT cannot re-arrange heap memory layout of objects as it must be hot-swappable. This is why despite incredibly huge investments in them such languages just never reach aot performance despite how much theoretical advantage a jit could have.
AOT'd languages could re-arrange a struct for better locality however the majority (if not all) languages rigidly require the fields are laid out in the order defined for various reasons.
The as-if rule gives an escape hatch, although in practice it is hard to take advantage of, especially without whole program optimization.