You could argue that each processor's errata is UB in assembly. I remember that ...

daemin on Aug 3, 2017 | parent | context | favorite | on: How I implemented my own crypto

You could argue that each processor's errata is UB in assembly. I remember that programming for the XScale we had a whole manual of errata that we had to program around. Though because it's documented it's not "Undefined", it's just "Incorrect but we know how incorrect".