Looking at my 8051 standard header file:

#if defined (SDCC)			/* SDCC */
...
#define XBYTE ((unsigned char xdata *) 0) /* NOT volatile cos duff code */

 

You can normally access memory mapped peripherals with the XBYTE macro e.g.

#define lcd_status      XBYTE[LCD_PORT]
#define lcd_data        XBYTE[LCD_PORT+1]
#define lcd_ctl         XBYTE[LCD_PORT+3]

 

I have no idea why I added the above comment for SDCC, just that it is there.
The regular XBYTE macro uses volatile for other compilers.

I seldom use 8051, and my SDCC is elderly.
From a semantic point of view, you should use volatile.

You may prefer using different macros. For example

#define XMEM(ads) ((unsigned char xdata *) 0)[x] /* NOT volatile cos duff code */

 

or use the __at modifier in a different macro.

David.