Vladimir Makarov <[EMAIL PROTECTED]> writes: > Richard Sandiford wrote: >> "H.J. Lu" <[EMAIL PROTECTED]> writes: >> >>> On Tue, Sep 2, 2008 at 8:37 AM, Vladimir Makarov <[EMAIL PROTECTED]> wrote: >>> >>>>> If using DF seems like the Right Thing, we could simply apply both >>>>> patches, which would give a similar same allocno order to the one >>>>> we have now. But it seemed better to look a bit deeper first... >>>>> >>>>> >>>> Richard, please apply the both patches. As I wrote above there is no >>>> SPECFP regression anymore with the patches. They also solves some >>>> testsuite regressions concerning EH. >>>> >>>> >>> Hi Richard, >>> >>> Could you please apply your use DF patch? It fixes EH regressions >>> as well as 434.zeusmp in SPEC CPU 2006? >>> >> >> As I said yesterday, I'm reluctant to apply the first patch, >> because without further analysis, there's a danger it's just >> papering over a deeper problem. >> >> It's interesting that it fixes EH regressions for you too though. >> That was what the patch was originally meant to do, but I thought >> I'd only seem the regressions I was fixing on MIPS, not on x86_64. >> Which target did you see them on? >> >> > Richard, please apply the both patches because I know that they will not > introduce performance regression. I'll check what happens to SPEC2000 > without the second patch (allocno ordering) later. If it is ok we could > remove the second patch.
Sorry Vlad, my reply to HJ crossed with your message. I'm really against applying the ALLOCNO_COMPARE patch. Unlike the DF patch, It isn't needed to fix a correctness regression. And it changes the heuristics _without any explanation of why this is necessary_. IMO, that's unacceptable for our shiny, new (and generally very nice) register allocator. And I think it's unacceptable even if it happens to fix a performance regression. Experience suggests that if we apply this patch now, no-one will ever look at the deeper problem, and we'll be lumped with magic goo that no-one really understands. After all, this issue is about three months old now. (And that certainly isn't meant to be a criticism. We're all busy people. But it's because we're busy people that I'm so reluctant to apply the patch.) But as I said to HJ, I'm happy to apply the DF patch in isolation, as long as we accept that the benefit of fixing a correctness regression outweighs the potential performance regression. Richard