------- Comment #29 from hubicka at gcc dot gnu dot org 2008-02-08 14:54 ------- Hi, tonight results from Haydn shows 32bit scores with the loop-invariant hack disabled. http://www.suse.de/~gcctest/SPEC/CFP/sb-haydn-head-64-32o-32bit/index.html
There are no off noise speedups though I must admit that the 32bit results from Haydn are truly noisy. I also did runs by hand and those also don't seem much difference, but the noise factor is always dificult to estimate in little stuff like this. I will give it a run on britten too to double check, it was running different patch tonight. However I wonder if you do have testcases where the hack helps. In general we can 1) ignore the problem 2) disable the hack for loop-invariant only (not for GCSE). Loop-invariant is more sure about benefits and already has some heuristics to limit the pressure. I do agree that in general having too many stuff in x87 registers kills the perofmrance on very random basis. 3) come up with more cureful heuristics for loop-invariant. Perhaps based on number of loop carried variables or numebr of FP registers live across loopback edge. For 3 we would need test also benchmarks that originally exposed the problem. I see it was tested on povray, it would be nice the the test was repeated (and I can probably do that if no one volunteers ;) Honza -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23322