Intel added PREFETCHW to their Broadwell processors launched in 2014, years after AMD dropped all 3DNow! instructions except the prefetch instructions. That timeline strongly suggests that the instructions aren't no-ops and likely are used by some popular software.
That list doesn't include any current mainline processors. It's all Itanium, 3DNow!, and MIPS.
Intel added PREFETCHW to their Broadwell processors launched in 2014, years after AMD dropped all 3DNow! instructions except the prefetch instructions. That timeline strongly suggests that the instructions aren't no-ops and likely are used by some popular software.