_R_S4
uc.uc_mcontext.__gregs[_REG_S4] = sc->sc_regs[_R_S4];
{ "s4", (long *)&ddb_regs.r_regs[_R_S4], DB_SETF_REGS, NULL },
gdb_regs[20] = regs->r_regs[_R_S4]; /* S4 */
case _R_S4: /* s4 */
tf->tf_regs[_R_S3], tf->tf_regs[_R_S4], tf->tf_regs[_R_S5]);