Julien,
Have you looked really sharp? I expect f1() to generate
a JBC (instead of JB or JNB) and that includes the
clearing of the sbit.
Maarten
>
> Hi,
>
> I am currently having an issue (or a misunderstanding) with sdcc
> mcs51 with a sbit clearing instruction being erroneously (IMHO)
> removed.
>
> I am using sdcc-3.0.0 (as shipped in Fedora 14 repository). sdcc -v
> SDCC : mcs51/gbz80/z80/ds390/pic16/pic14/TININative/ds400/hc08 3.0.0
> #6037 (Mar 20 2011) (Linux)
>
> I have also tested with the svn development version rev 6473. sdcc -v
> SDCC : mcs51/gbz80/z80/ds390/pic16/pic14/TININative/ds400/hc08 3.0.2
> #6470 (Apr 30 2011) (Linux)
>
> The code is targeted for a 8051 included in a TI cc1110. The
> following code is a simplified version of the issue:
>
> /* compile with "sdcc -mmcs51 file.c" */
>
> #include <mcs51/cc1110.h>
>
> void f1(void) {
> UTX0IF = 0;
> U0DBUF = 'X';
> while ( !UTX0IF ) ;
> UTX0IF = 0;
> }
>
> void f2(void) {
> UTX0IF = 0;
> U0DBUF = 'X';
> while ( !UTX0IF ) {
> __asm
> nop
> __endasm;
> }
> UTX0IF = 0;
> }
>
> void f3(void) {
> IRCON2 &= ~0x02;
> U0DBUF = 'X';
> while ( (IRCON2 & 0x02) == 0 ) ;
> IRCON2 &= ~0x02;
> }
>
> void main(void) {
> f1(); f2(); f3();
> }
>
> /* End of code */
>
> When looking at the assembler code of the f1() function, the second
> sbit affectation "UTX0IF = 0;" (which should be compiled with a "clr
> _UTX0IF") has been removed (apparently by the label optimization).
>
> The f2() and f3() are alternate versions of f1(). f2() add a NOP
> into the while() statement. f3() uses the sfr instead of the sbit.
> These alternate versions are not affected by this issue.
>
> As a final note, the instruction is not removed in
> f1() when the code is compiled with the --nolabelopt option.
>
> I would expect that these three functions has the same behavior.
> Did I miss something or is this some kind of a bug?
>
> Thanks,
>
> -- Julien Olivain.
>
> ------------------------------------------------------------------------------
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