On Thu, Apr 24, 2008 at 10:42:49AM -0400, Vladimir Makarov wrote: > FX wrote: > >> The best way to test IRA is to build and use the branch. It is easy to > >>compare the old RA (which is the default on the branch) and IRA (-fira > >>option switches IRA on). I'd recommend to try the following option sets: > >> -fira > >> -fira -fira-algorithm=CB > >> > > > >OK, I've done that and I see a 40% to 60% increase in compilation time > >for the first (Fortran) testcase I tried, is that expected? > > > > > Yes, that is known problem for -O0. The old allocator does not use > global allocator at -O0, IRA is used always even for -O0. The correct > comparison would be at -O2. There are several solution of the problem: > o We could make only the reload working for -O0. In this case, the > time will be the same. > o We could prevent regional allocation at -O0. In this case, the > slow down would be 20% (I guess). > o Use a very fast and simple local allocation. > o Or just ignore this. > > I'd prefer the second solution.
Ignoring it isn't an option; developers who spend most of their time in the compile/debug/test/fix loop would see a 40-60% decrease at -O0 as a very severe regression. Even 20% would get a lot of complaints.
