>> It does not really get ignored, but the compiler performs more 
>> aggressive live range splitting (because it uses SSA in 4.x so live 
>> range splitting comes from free -- sometimes even if you don't want 
>> it...).  OTOH the optimizer is better, which is why sends are faster.
>
>   Hmm, so simple increment assigns a new value and the range is
> splitted there?

while (i < j)
   {
     *a++ = *i++;
     *b++ = *i++;
     *c++ = *i++;
   }

The increments of a/b/b are not splittable, because the value is used 
again in the next loop iteration and obviously it has to be in the same 
registers.  But the increments of i can be rewritten as

   {
     *a++ = *i; temp1 = i + 1;
     *b++ = *temp1; temp2 = temp1 + 1;
     *c++ = *temp2; i = temp2 + 1;
   }

Most of the time register allocation will allocate temp1 and temp2 to 
the same register as i ("coalescing"), but there's no guarantee that it 
will.

Paolo