On Thu, Sep 14, 2017 at 11:24 AM, Richard Biener <richard.guent...@gmail.com> wrote: > On Thu, Sep 14, 2017 at 12:18 PM, Martin Liška <mli...@suse.cz> wrote: >> On 09/14/2017 12:07 PM, Markus Trippelsdorf wrote: >>> On 2017.09.14 at 11:57 +0200, Richard Biener wrote: >>>> On Wed, Sep 13, 2017 at 6:11 PM, Nikos Chantziaras <rea...@gmail.com> >>>> wrote: >>>>> On 12/09/17 16:57, Wilco Dijkstra wrote: >>>>>> >>>>>> [...] As a result users are >>>>>> required to enable several additional optimizations by hand to get good >>>>>> code. >>>>>> Other compilers enable more optimizations at -O2 (loop unrolling in LLVM >>>>>> was >>>>>> mentioned repeatedly) which GCC could/should do as well. >>>>>> [...] >>>>>> >>>>>> I'd welcome discussion and other proposals for similar improvements. >>>>> >>>>> >>>>> What's the status of graphite? It's been around for years. Isn't it mature >>>>> enough to enable these: >>>>> >>>>> -floop-interchange -ftree-loop-distribution -floop-strip-mine -floop-block >>>>> >>>>> by default for -O2? (And I'm not even sure those are the complete set of >>>>> graphite optimization flags, or just the "useful" ones.) >>>> >>>> It's not on by default at any optimization level. The main issue is the >>>> lack of maintainance and a set of known common internal compiler errors >>>> we hit. The other issue is that there's no benefit of turning those on for >>>> SPEC CPU benchmarking as far as I remember but quite a bit of extra >>>> compile-time cost. >>> >>> Not to mention the numerous wrong-code bugs. IMHO graphite should >>> deprecated as soon as possible. >>> >> >> For wrong-code bugs we've got and I recently went through, I fully agree >> with this >> approach and I would do it for GCC 8. There are PRs where order of simple 2 >> loops >> is changed, causing wrong-code as there's a data dependence. >> >> Moreover, I know that Bin was thinking about selection whether to use >> classical loop >> optimizations or Graphite (depending on options provided). This would >> simplify it ;) > > I don't think removing graphite is warranted, I still think it is the > approach to use when > handling non-perfect nests. Hi, IMHO, we should not be in a hurry to remove graphite, though we are introducing some traditional transformations. It's a quite standalone part in GCC and supports more transformations. Also as it gets more attention, never know if somebody will find time to work on it.
Thanks, bin > > Richard. > >> Martin
