ABIs are a convention that everybody follows regarding how such preservation should or should not occur, for which registers. It's common to say "caller cleans

ABIs are a convention that everybody follows regarding how such preservation should or should not occur, for which registers. It's common to say "caller cleans up registers x, y, z, callee cleans up a, b, c". So yes, the caller could do it or not do it, the choices are all possible to do both ways, but that wouldn't be the agreed upon ABI, it'd be something different.