On Fri, 13 Nov 2015, VandeVondele Joost wrote: > I'm all in favour of requiring isl and enabling graphite by default, but > would suggest to enable it with -Ofast instead. > > One reason is that certainly extracting testcases from a PGO build is > more difficult, and initially there will certainly be miscompiles with > graphite (CP2K is right now). > > Furthermore, unless graphite is particularly effective with PGO (does it > use average loop trip counts already?), I don't see a particular > connection.
The reason to choose FDO was so GRAPHITE can concentrate its computing budget on the hot parts of a program (which profile estimation isn't good enough identifying), reducing its compile-time cost. -Ofast isn't supposed to enable passes over -O3 so you're suggesting to enable it with -O3 which I think is a bit premature. But we can try doing that and revert at the end of stage3 if problems are just too big. Richard.
