On Sun, 2006-01-15 at 22:24 +0100, Tobias Schlüter wrote: > Richard Guenther wrote: > > I guess the fix for PR tree-optimization/22555 could make some difference > > if fortran uses a lot of structures with embedded arrays. Basically this > > enables decomposing these structures for aliasing purposes and should > > generate better code. > > It is perhaps noteworthy that the build times for the base run of Diego's > SPECFP tester have increased by approx. twenty percent, with no visible gain > in execution speed, between Jan 5th and Jan 6th, see > <http://people.redhat.com/dnovillo/spec2000.i686/gcc/global-build-secs_elapsed.html> > and > <http://people.redhat.com/dnovillo/spec2000.i686/gcc/global-run-secs_elapsed.html> >
Again, this is why i was not convinced that array aliasing by decomposing array's into SFT's like Richard has implemented is valuable enough that it's worth the cost. Right now, it's certainly going to decompose arrays in most cases for no real benefit. The code should determine whether there is even a possibility of optimization using the SFT information before doing it (that's really what the used part stuff is. This goes also for structures, but structures in general are always indexed by *some* constant index, so you usually get some better optimization, and thus, the effect is not as pronounced --Dan > - Tobi
