One of our partners has reported the following

  Currently, the C2 peephole optimization is only enabled by default for x86 & aarch64 port.
  But we don't have any peephole rules for aarch64 port, scanning the instruction stream
  in PhasePeephole::do_transform does not make sense but a waste of time for this port.
  So I am disabling this pass for aarch64 port by default, can anyone sponsor this if approved?