[Openec] checksum of first 64k of updateme.bin not calculated correctly

[Paul Fox]

frieder wrote:
 > Hi Richard,
 > 
 > Am 01.11.2010 10:04, schrieb Richard A. Smith:
 > > On 11/01/2010 03:56 AM, Frieder Ferlemann wrote:
 > > 
 > >> Do you see problems/shortcomings (or near term problems)
 > >> with the current code?
 > >> (In terms of data, xdata, code memory or functionality?)
 > > 
 > > The existing info out on IRC is a bit premature.  I was waiting until 
 > > after 1.75 bringup to write up the announcement and the general state of 
 > > affairs.
 > 
 > Fine.

yes, it's definitely rough, still.  :-)

 > 
 > > Resource wise the KB3930 has plenty of resources, but its only a 
 > > stepping stone. There are certainly some challenges ahead for moving to 
 > > the IO3730.  It only has 32k of ROM and does not have in-ram code 
 > > execution ability.
 > > 
 > > Right now it looks like we will have to switch back to Keil because sdcc 
 > > generate code is so much larger.
 > 
 > How much space is left in data memory and in code memory?
 > (Can you give numbers for Keil versus SDCC?)
 > 
 > The memory model currently used (--model-large) for SDCC
 > is typically generating about 33% larger code than the
 > (--model-small) or about 18% larger code than the
 > stack-auto memory model.
 > (ratios from regression test results)

we should certainly look at using small, then.  when i built a
comparable set of 1.75 source on both keil and sdcc "large", keil was
about 2/3's the size.  many of our accesses are to xdata, as you
noticed, so we might not get the full gain of small, but if it could
keep us on sdcc we'd all be happier.

 > 
 > 
 > > Is sdcc 3 any better at generating smaller code?
 > 
 > If so then likely in the (low) single digit percent range.
 > BTW SDCC 3.0.0 has been released today.

great!  i'll try it.

 > 
 > 
 > The ec-1.75 source often uses code which clears/sets/
 > toggles bits within an external __xdata array.
 > SDCC does not recognize this yet.
 > Taking for example the last lines of the code generated
 > for updateme.c
 > 
 >                            1150 ;       updateme.c:423: xbi[SPICFG] &= 
 > ~(SPICFG_WEN | SPICFG_CS_LOW);
 >    0404 90 FE AD           1151         mov     dptr,#(_xbi + 0x000d)
 >    0407 E0                 1152         movx    a, at dptr
 >    0408 FA                 1153         mov     r2,a
 >    0409 53 02 E7           1154         anl     ar2,#0xE7
 >    040C 90 FE AD           1155         mov     dptr,#(_xbi + 0x000d)
 >    040F EA                 1156         mov     a,r2
 >    0410 F0                 1157         movx    @dptr,a
 > 
 > These type of accesses could be reduced to:
 > 
 >                            1150 ;       updateme.c:423: xbi[SPICFG] &= 
 > ~(SPICFG_WEN | SPICFG_CS_LOW);
 >    0404 90 FE AD           1151         mov     dptr,#(_xbi + 0x000d)
 >    0407 E0                 1152         movx    a, at dptr
 >    0409 xx E7              1154         anl     a,#0xE7
 >    040F xx                 1156         mov     r2,a
 >    0410 F0                 1157         movx    @dptr,a
 > 
 > with relatively little effort by using a peephole file.

yes, we were talking about that sort of construct just a day or two
ago.  fixing that would help a lot.

regarding optimization -- from the sdcc docs, it looks like most (all?)
optimizations are on by default, and the options exist to disable them,
correct?  so there's nothing we should be adding to the makefile to
make sure we're getting all available benefit?

paul
=---------------------
 paul fox, pgf at laptop.org