On Fri, Sep 19, 2008 at 05:09:17PM +0100, Maciej W. Rozycki wrote: > > @@ -229,6 +239,9 @@ LEAF(csum_partial) > > > > /* Still a full word to go */ > > ulw t1, (src) > > +#ifdef USE_DOUBLE > > + add t1, zero /* clear upper 32bit */ > > +#endif > > PTR_ADDIU src, 4 > > ADDC(sum, t1) > > > > Unfortunately you can't zero-extend with a single instruction (you can > use a single sll(v) to sign-extend), unless the R2 ISA provides some > suitable oddity (which I haven't checked). You want something like: > > dsll32 t1, t1, 0 > dsrl32 t1, t1, 0 > > instead. For a one's complement checksum it doesn't matter in which of the 4 halfwords the data ends is loaded. So the easiest solution is: /* Still a full word to go */ ulw t1, (src) #ifdef USE_DOUBLE dsll t1, t1, 32 /* clear lower 32bit */ #endif PTR_ADDIU src, 4 ADDC(sum, t1) Ralf
