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Not a direct compiler optimization, but consider memcpy() vs memmove() as an example. If you know two regions of memory do not overlap you can call memcpy() for a direct optimized copy, but if they overlap you must call memmove() and introduce an intermediate copy.

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memmove does not (in any implementation I’ve ever heard of) introduce an intermediate copy, it just performs the copy loop in the reverse direction to handle the overlap (and can’t always vectorize in the same way memcpy can).

It makes sense, but when would you ever memcpy with overlap? I would think any situation that lets that happen is from a bug, like you have an incorrect buffer length or an incorrect destination address.

Inserting an element in an array is something along the lines of memmove(arr + idx + 1, arr + idx, (length - idx) * sizeof(*arr)); arr[idx] = foo;

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