Every new (post-2018) iPhone ships with this. iOS developers can build code for the architecture but I believe Apple currently strips it out before distribution, so its use is limited to the OS for now. I would assume at some point they’ll flip the switch to allow it; until then developers can use the toolchain to test if their code still works (generally it does, but messing with function pointers in ways unspecified by the standard can occasionally cause problems). ‘pjmlp is fairly interested in this topic so they might be able to share some more examples of it being used if they drop by the thread.