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. Richard. > Martin
