[sdcc-devel] Patch for inc/dec on data variables (mcs51)

[Frieder F. <fri...@we...>]

Hi,

I append a patch which enables the generation
of optimized increment and decrement code
on variables in data space. 

Without the patch:

                           1238 ;parse.c:146: cur++;
   04CC                    1239 00153$:
                           1240 ;     genPlus
                           1241 ;     genPlusIncr
   04CC 74 01              1242         mov     a,#0x01
   04CE 25*09              1243         add     a,_cur
   04D0 F5*09              1244         mov     _cur,a
                           1245 ;       Peephole 180    changed mov to clr
   04D2 E4                 1246         clr     a
   04D3 35*0A              1247         addc    a,(_cur + 1)
   04D5 F5*0A              1248         mov     (_cur + 1),a

With the patch:

                           1212 ;parse.c:146: cur++;
   04A5                    1213 00153$:
                           1214 ;     genPlus
                           1215 ;     genPlusIncr
   04A5 05*09              1216         inc     _cur
   04A7 E4                 1217         clr     a
   04A8 B5*09 02           1218         cjne    a,_cur,00294$
   04AB 05*0A              1219         inc     (_cur + 1)
   04AD                    1220 00294$:


It saves about 40 bytes on the file parse.c which Johan 
recently posted. (42 to be more accurate - Douglas Adams greets here)

The code actually doing the inc/dec was already hiding there, 
it was just waiting to be enabled?)


Frieder