SPR_DSCRP
if (spr == SPR_DSCR || spr == SPR_DSCRP) {
td->td_pcb->pcb_dscr = mfspr(SPR_DSCRP);
if (spr == SPR_DSCR || spr == SPR_DSCRP) {
mtspr(SPR_DSCRP, frame->fixreg[reg]);
mtspr(SPR_DSCRP, 0);
pcb->pcb_dscr = mfspr(SPR_DSCRP);