On Tue, Sep 11, 2012 at 10:41 AM, Vladimir Makarov <vmaka...@redhat.com> wrote: > On 12-09-10 6:05 AM, Bin.Cheng wrote: >> >> Hi, >> I digged into gcc mail archive and found there are several threads >> discussing about live range shrink, like: > > As I know Ghassan preferred to work on Open64 that time in AMD and never > touched GCC. > >> and >> http://gcc.gnu.org/ml/gcc-patches/2009-01/msg00188.html >> >> In these messages many people showed interests in LRS, in or out of >> sched1 pass. I am curious about the status now and have following >> questions: >> 1. Does sched-pressure patch Vlad worked is the LRS we mentioned in the >> message? > > No, the pressure-sensitive insn scheduler is not LRS. It mostly does not > increase the register pressure when it is already high. There is other more > comprehensive pressure-sensitive heuristic implemented by Richard Sandiford. > I think it is better to ask Rcihard the same question about his heuristic. > >> 2. If the answer is no, are there still someone want to do this in >> sched1? Or as Vlad once mentioned that we should implement LRS in >> another pass along with register re-materialization? > > It is still on my list of possible projects although I am busy with LRA > project now and don't know when I can start it. I know how to decrease > register pressure through rematerialization but I did not figured out yet > how to do LRS and how to combine them. > >> 3. What's the status/expectation of LRS now? > > I don't think there is any status of LRS. I only can say that introduction > of IRA made this project more doable for implementation. Before its > implementation accurate register pressure estimation just was not possible. > Hi Vlad, Thanks very much for your detailed explanation.
-- Best Regards.
