SPCF_SHOULDYIELD
if (spc->spc_flags & SPCF_SHOULDYIELD) {
spc->spc_flags |= SPCF_SHOULDYIELD;
spc->spc_flags |= SPCF_SHOULDYIELD;
spc->spc_flags |= SPCF_SHOULDYIELD;
#define SPCF_SWITCHCLEAR (SPCF_SEENRR|SPCF_SHOULDYIELD)