Is this really true? Does't the runtime of some arithmetic instructions (like IDIV) depend on the argument?
https://developer.arm.com/documentation/ddi0601/2025-06/AArc...
and the set of instructions you can safely use is listed.
I believe Intel has a similar thing.
It doesn't tell you "yes" or "no", but it does tell you "definitely not" or "maybe". This information is useful even if it's not the whole story.