Difference between rmw and amo

[hernanponcedeleon]

The documentation defines these realtions as

rmw : relate the read and write events emitted by matching successful load-reserve store conditional instructions, or atomic rmw instructions.
amo: relate the read and write events emitted by atomic rmw instructions.

The second part of the former sounds equivalent to the later to me.

I am right that this mean amo is a subset of rmw, and anything "extra" in rmw is related to load-reserve store conditional instructions? What is the rational of having this rather than having amo as it is, some relation x: relate the read and write events emitted by matching successful load-reserve store conditional instructions and let rmw = x | amo. Some old aarch64 models seem to be following this idea.

Or is this somehow related to the fact that some RMW instructions are represented a single event while other are split into their read and write parts?