ISS_MSR_Rt_SHIFT
esr |= MRS_REGISTER(insn) << ISS_MSR_Rt_SHIFT;
#define ISS_MSR_Rt_MASK (0x1f << ISS_MSR_Rt_SHIFT)
#define ISS_MSR_Rt(x) (((x) & ISS_MSR_Rt_MASK) >> ISS_MSR_Rt_SHIFT)