Ian Lance Taylor wrote:
4) A discussion of dataflow. Ken Zadeck described the current state of dataflow branch. It seems stable, and just about within the compilation time guidelines set by the SC. He will do more testing and retesting this weekend, and hopes to commit it to mainline quite soon, maybe as early as next week if the testing goes well.
I am strongly disagree with clause `merging next week'. The first of all the code should be reviewed by somebody independent (Richard Henderson would be the best person IMHO but I don't know would he like to do it) because it touch too much back-back end code and give no old path. Probably other ports can be broken. And I am disagree that it is within compilation time guidelines set by SC. Ken fixed a big compilation time degradation a few days ago and preliminary what I see now (comparison with the last merge point) is x86_64 SPECInt2000 5.7% SPECFp200 8.7% ppc64 SPECInt2000 6.5% SPECFp2000 5.5% Itanium SPECInt2000 9% SPECFp2000 10.9% Besides as I understand correctly the SC criteria means that there is no degradation on code quality. There is code size degradation about 1% and some degradation on SPEC2000 (e.g. about 2% degradation on a few tests on ia64). I am afraid that merging it earlier stops progress on the df infrastructurey (e.g. Ken will work only on LTO) and that also further transition of some optimizations to the df infrastructure will make code even slower and finally again we will have slower compiler with worse code. I'll do more thorough benchmarking too and report it on the next week.
