AST
RESTORE_REG(AT, AST, frame, bo) ;\
SAVE_REG(AT, AST, frame, bo) ;\
bcopy(®s->r_regs[AST], &p->p_md.md_regs->ast, REGSIZE);
bcopy(&p->p_md.md_regs->ast, ®s->r_regs[AST], REGSIZE);