Sort of. The ARM stuff was allowed other uses because they were pretty generic load and store multiple instructions with a lot of increment/decrement options to make up for the original Acorn's lack of a DMA engine.
On anything resembling a recent ARM core though, using the stack pointer register with anything other than a descending stack has you falling off the perf wagon as it's backed by a hardware stack engine.
On anything resembling a recent ARM core though, using the stack pointer register with anything other than a descending stack has you falling off the perf wagon as it's backed by a hardware stack engine.