Hello, > Steve Ellcey wrote: > > >This seems unfortunate. I was hoping I might be able to turn on loop > >unrolling for IA64 at -O2 to improve performance. I have only started > >looking into this idea but it seems to help performance quite a bit, > >though it is also increasing size quite a bit too so it may need some > >modification of the unrolling parameters to make it practical. > > To me it is obvious that optimizations are target dependent. For > instance loop unrolling is really a totally different optimization > on the ia64 as a result of the rotating registers.
that we do not use. Nevertheless, there are still compelling reasons for why unrolling is more useful on ia64 then on other architectures (importance of scheduling, insensitivity to code size growth). Another option would be to consider enabling (e.g.) -funroll-loops -fprefetch-loop-arrays by default on -O3. I think it is fairly rare for these flags to cause performance regressions (although of course more measurements to support this claim would be necessary). Zdenek
