case 77: /* syscall $scon, syscall Rx */
		if p.From.Type == obj.TYPE_CONST {
			if p.From.Offset > BIG || p.From.Offset < -BIG {
				c.ctxt.Diag("illegal syscall, sysnum too large: %v", p)
			}
			o1 = AOP_IRR(OP_ADDI, REGZERO, REGZERO, uint32(p.From.Offset))
		} else if p.From.Type == obj.TYPE_REG {
			o1 = LOP_RRR(OP_OR, REGZERO, uint32(p.From.Reg), uint32(p.From.Reg))
		} else {