wrt performance every application is going to be different.  if you
care a *lot* about performance, you have to *test* your applications
in both 32 bit and 64 bit environments to try.  either can be faster...
   
   Some integer arithmetic on long long datatypes may be faster in 64-bit 
   mode, however I suspect compiling with gcc's -mcpu=ultrasparc may be 
   able to produce 32-bit code which handles 64-bit integer arithmetic much 
   more efficiently.

-mcpu=ultrasparc schedules the code such that the even-more-superscalar
nature of the ultrasparc can be used.  it doesn't really allow the use
of raw 64 bit arith...


.mrg.