thanks for all explanation, it really helped to refine my code Sri On Mon, Jan 31, 2011 at 12:58 PM, Rajat Sharma <fs.rajat@xxxxxxxxx> wrote: >> Is is not that Code A is wrong, for not mentioning cobbler list >> 'memory' to indicate memory contents are getting updated. >> Please rectify me, if I am wrong. > > From Code B, it looks like instruction to compiler for not using extra > memory location other than ones specified for input param and output > param. Is it some sort of memory synchronization code? > >> Also, what does '+m' constraint mean, if I use in inline assembly. > > It means the memory location for param is both Readable and Writable > > Rajat > > On Mon, Jan 31, 2011 at 10:07 PM, Sri Ram Vemulpali > <sri.ram.gmu06@xxxxxxxxx> wrote: >> Hi, >> >> I have following snippet of code. >> >> Code A >> >> __asm__ __volatile__( >> " lock ;\n" >> " addl %1,%0 ;\n" >> : "=m" (my_var) >> : "ir" (my_int), "m" (my_var) >> : /* no clobber-list */ >> ); >> >> Code B >> >> __asm__ __volatile__( "decl %0; sete %1" >> : "=m" (my_var), "=q" (cond) >> : "m" (my_var) >> : "memory" >> ); >> >> In Code A memory contents are getting updated. And in Code B memory >> contents and 'cond' var are getting updated. >> In Code B in cobbler column 'memory' is used to indicate that this >> code modifies memory contents. But where as in Code A it was not >> mentioned >> >> Is is not that Code A is wrong, for not mentioning cobbler list >> 'memory' to indicate memory contents are getting updated. >> Please rectify me, if I am wrong. >> >> Also, what does '+m' constraint mean, if I use in inline assembly. >> -- >> Regards, >> Sri. >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies@xxxxxxxxxxxxxxxxx >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> > -- Regards, Sri. _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
