On 05/13, Richard Biener wrote: > On Sun, 12 May 2019, Giuliano Belinassi wrote: > > > Hi, Richard > > > > On 05/07, Richard Biener wrote: > > > On Mon, 6 May 2019, Giuliano Belinassi wrote: > > > > > > > Hi, > > > > > > > > On 03/29, Richard Biener wrote: > > > > > On Thu, 28 Mar 2019, Giuliano Belinassi wrote: > > > > > > > > > > > Hi, Richard > > > > > > > > > > > > On 03/28, Richard Biener wrote: > > > > > > > On Wed, Mar 27, 2019 at 2:55 PM Giuliano Belinassi > > > > > > > <giuliano.belina...@usp.br> wrote: > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > On 03/26, Richard Biener wrote: > > > > > > > > > On Tue, 26 Mar 2019, David Malcolm wrote: > > > > > > > > > > > > > > > > > > > On Mon, 2019-03-25 at 19:51 -0400, nick wrote: > > > > > > > > > > > Greetings All, > > > > > > > > > > > > > > > > > > > > > > I would like to take up parallelize compilation using > > > > > > > > > > > threads or make > > > > > > > > > > > c++/c > > > > > > > > > > > memory issues not automatically promote. I did ask about > > > > > > > > > > > this before > > > > > > > > > > > but > > > > > > > > > > > not get a reply. When someone replies I'm just a little > > > > > > > > > > > concerned as > > > > > > > > > > > my writing for proposals has never been great so if > > > > > > > > > > > someone just > > > > > > > > > > > reviews > > > > > > > > > > > and doubt checks that's fine. > > > > > > > > > > > > > > > > > > > > > > As for the other things building gcc and running the > > > > > > > > > > > testsuite is > > > > > > > > > > > fine. Plus > > > > > > > > > > > I already working on gcc so I've pretty aware of most > > > > > > > > > > > things and this > > > > > > > > > > > would > > > > > > > > > > > be a great steeping stone into more serious gcc > > > > > > > > > > > development work. > > > > > > > > > > > > > > > > > > > > > > If sample code is required that's in mainline gcc I sent > > > > > > > > > > > out a trial > > > > > > > > > > > patch > > > > > > > > > > > for this issue: > > > > > > > > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88395 > > > > > > > > > > > > > > > > > > > > > > Cheers, > > > > > > > > > > > > > > > > > > > > > > Nick > > > > > > > > > > > > > > > > > > > > It's good to see that you've gotten as far as attaching a > > > > > > > > > > patch to BZ > > > > > > > > > > [1] > > > > > > > > > > > > > > > > > > > > I think someone was going to attempt the "parallelize > > > > > > > > > > compilation using > > > > > > > > > > threads" idea last year, but then pulled out before the > > > > > > > > > > summer; you may > > > > > > > > > > want to check the archives (or was that you?) > > > > > > > > > > > > > > > > > > There's also Giuliano Belinassi who is interested in the same > > > > > > > > > project > > > > > > > > > (CCed). > > > > > > > > > > > > > > > > Yes, I will apply for this project, and I will submit the final > > > > > > > > version > > > > > > > > of my proposal by the end of the week. > > > > > > > > > > > > > > > > Currently, my target is the `expand_all_functions` routine, as > > > > > > > > most of > > > > > > > > the time is spent on it according to the experiments that I > > > > > > > > performed as > > > > > > > > part of my Master's research on compiler parallelization. > > > > > > > > (-O2, --disable-checking) > > > > > > > > > > > > > > Yes, more specifically I think the realistic target is the GIMPLE > > > > > > > part > > > > > > > of execute_pass_list (cfun, g->get_passes ()->all_passes); > > > > > > > done in > > > > > > > cgraph_node::expand. If you look at passes.def you'll see > > > > > > > all_passes > > > > > > > also contains RTL expansion (pass_expand) and the RTL optimization > > > > > > > queue (pass_rest_of_compilation). The RTL part isn't a realistic > > > > > > > target. > > > > > > > Without changing the pass hierarchy the obvious part that can be > > > > > > > handled would be the pass_all_optimizations pass sub-queue of > > > > > > > all_passes since those are all passes that perform transforms on > > > > > > > the > > > > > > > GIMPLE IL where we have all functions in this state at the same > > > > > > > time > > > > > > > and where no interactions between the functions happen anymore > > > > > > > and thus functions can be processed in parallel (as much as make > > > > > > > processes individual translation units in parallel). > > > > > > > > > > > > > > > > > > > Great. So if I understood correctly, I will need to split > > > > > > cgraph_node::expand() into three parts: IPA, GIMPLE and RTL, and > > > > > > then > > > > > > refactor `expand_all_functions` so that the loop > > > > > > > > > > > > for (i = new_order_pos - 1; i >= 0; i--) > > > > > > > > > > > > use these three functions, then partition > > > > > > > > > > > > g->get_passes()->all_passes > > > > > > > > > > > > into get_passes()->gimple_passes and get_passes()->rtl_passes, so I > > > > > > can run RTL after GIMPLE is finished, to finally start the > > > > > > paralellization of per function GIMPLE passes. > > > > > > > > > > Yes, it involves refactoring of the loop - you may notice that > > > > > parts of the compilation pipeline are under control of the > > > > > pass manager (passes.c) but some is still manually driven > > > > > by symbol_table::compile. Whether it's more convenient to > > > > > get more control stuffed to the pass manager and perform the > > > > > threading under its control (I'd say that would be the cleaner > > > > > design) or to try do this in the current ad-hoc parts remains > > > > > to be seen. You can see symbol_table::compile hands over > > > > > control to the pass manager multiple times, first ipa_passes () > > > > > then all_late_ipa_passes and finally the expand_all_functions code. > > > > > > > > > > I guess it would simplify things if you'd split pass_all_passes > > > > > in passes.def at pass_expand like so: > > > > > > > > > > diff --git a/gcc/passes.def b/gcc/passes.def > > > > > index 2fcd80e53a3..bb0453b36a7 100644 > > > > > --- a/gcc/passes.def > > > > > +++ b/gcc/passes.def > > > > > @@ -403,11 +403,10 @@ along with GCC; see the file COPYING3. If not > > > > > see > > > > > NEXT_PASS (pass_spectrev1); > > > > > NEXT_PASS (pass_warn_function_noreturn); > > > > > NEXT_PASS (pass_gen_hsail); > > > > > + TERMINATE_PASS_LIST (all_passes) > > > > > > > > > > - NEXT_PASS (pass_expand); > > > > > - > > > > > - NEXT_PASS (pass_rest_of_compilation); > > > > > - PUSH_INSERT_PASSES_WITHIN (pass_rest_of_compilation) > > > > > + INSERT_PASSES_AFTER (pass_rest_of_compilation) > > > > > + NEXT_PASS (pass_expand); > > > > > NEXT_PASS (pass_instantiate_virtual_regs); > > > > > NEXT_PASS (pass_into_cfg_layout_mode); > > > > > NEXT_PASS (pass_jump); > > > > > @@ -505,6 +504,5 @@ along with GCC; see the file COPYING3. If not see > > > > > NEXT_PASS (pass_final); > > > > > POP_INSERT_PASSES () > > > > > NEXT_PASS (pass_df_finish); > > > > > - POP_INSERT_PASSES () > > > > > NEXT_PASS (pass_clean_state); > > > > > - TERMINATE_PASS_LIST (all_passes) > > > > > + TERMINATE_PASS_LIST (pass_rest_of_compilation) > > > > > > > > > > where to make things "work" again w/o threading you'd invoke > > > > > execute_pass_list (cfun, g->get_passes ()->pass_rest_of_compilation) > > > > > right after the all_passes invocation in cgraph_node::expand. > > > > > > > > > > You then can refactor things so the loop over the 'order' array > > > > > is done twice, once over all_passes (the set you then parallelize) > > > > > and once over pass_rest_of_compilation (which you can't parallelize > > > > > because of being in RTL). > > > > > > > > > > > > > I managed to get it working today. However, I found an issue with the > > > > statistics_fini_pass() and pass_init_dump_file(), which I had to > > > > comment, and force a `return false` for every case, respectively. Then I > > > > managed to compile some programs correctly with -O2. I have no idea why > > > > yet, but I will keep searching. I've attached my patch here. > > > > > > It may be that you need to adjust the GCC_PASS_LISTS define in > > > pass_manager.h, changing pass_rest_of_compilation to a pass list > > > and also remove its "old" definition in passes.c. Or it might > > > be simpler to not re-use pass_rest_of_compilation but wrap > > > the tail in a new all_passes2 or so. You'll also see > > > a call to register_dump_files (all_passes) in passes.c where > > > you probably need to do the same for the new tail. > > > > > > As usual grep is your best friend when figuring out what to do > > > (doing that right now myself). > > > > > > Richard. > > > > I am just posting this as an update. > > > > Just to contextualize, I've managed to fix this issue by following Biener's > > advices. However what happened next was that the pr87600-2.c was > > crashing the compiler, as discussed in IRC. The reason of the crash was > > that after the discussed modifications, the `pass->next` after `pass_expand` > > was not `pass_cleanup`, since the NEXT_PASS after `pass_expand` was > > `pass_instantiate_virtual_regs`. I fixed that by not reusing the > > `pass_rest_of_compilation`, but by creating a new pass called > > `all_rtl_passes` > > and keeping `pass_expand` before the `PUSH_INSERT_PASSES_WITHIN`. > > > > After that, I've run the full `dg.exp` testsuite and found that the > > following tests are also failing: > > > > FAIL: gcc.dg/20020919-1.c (internal compiler error) > > FAIL: gcc.dg/always_inline3.c (internal compiler error) > > FAIL: gcc.dg/dx-test.c (internal compiler error) > > FAIL: gcc.dg/pr32370.c (internal compiler error) > > FAIL: gcc.dg/pr61692.c (internal compiler error) > > FAIL: gcc.dg/pr87600-2.c (internal compiler error) > > FAIL: gcc.dg/va-arg-pack-1.c (internal compiler error) > > FAIL: g++.dg/cpp0x/Wattributes1.C -std=c++14 (test for warnings, line 125) > > FAIL: g++.dg/cpp0x/Wattributes1.C -std=c++17 (test for warnings, line 125) > > FAIL: g++.dg/opt/pr69213.C -std=gnu++98 (internal compiler error) > > FAIL: g++.dg/opt/pr69213.C -std=gnu++14 (internal compiler error) > > FAIL: g++.dg/opt/pr69213.C -std=gnu++17 (internal compiler error) > > > > Notice that pr87600-2.c is failing again, but now when trying to compile the > > `long test3 (void)` function. Interestingly, if I comment every function but > > test3(), the test passes. All tests seems to be failed in the assert: > > > > gcc_assert (TREE_ASM_WRITTEN (decl)) > > > > of cgraphunit.c:2255, and the rtl dumps seems always to be different from > > trunk. > > > > I've attached a patch to my modifications, if anyone is interested in it. > > I hope to provide a better feedback in the next days. > > Btw, if you are familiar with git I encourage you to publish your > changes on a branch. Conveniently there's a github mirror of the > GCC repository you can branch off. It might be easier to work > on a not-so-fast moving target which would mean branching off the > gcc-9-branch for example (or just not rebase your branch too often). >
I am working on a mirror that I created: https://gitlab.com/flusp/gcc/tree/giulianob_parallel I also managed to fix all problems that I mentioned earlier. Basically the check before calling the get_all_rtl_passes () was incorrect. > Thanks, > Richard. > > > > > > > > > > > > > > > > > The above patch needs more changes in pass manager code - a chance > > > > > to dive into it a little since that's where you'd change code. > > > > > > > > > > > > To simplify the taks further a useful constraint is to not have > > > > > > > a single optimization pass executed multiple times at the same > > > > > > > time > > > > > > > (otherwise you have to look at pass specific global states as > > > > > > > well), > > > > > > > thus the parallel part could be coded in a way keeping per > > > > > > > function > > > > > > > the state of what pass to execute next and have a scheduler pick > > > > > > > a function its next pass is "free", scheduling that to a fixed > > > > > > > set of > > > > > > > worker threads. There's no dependences between functions > > > > > > > for the scheduling but each pass has only one execution resource > > > > > > > in the pipeline. You can start processing an arbitrarily large > > > > > > > number > > > > > > > of functions but slow functions will keep others from advancing > > > > > > > across > > > > > > > the pass it executes on. > > > > > > > > > > > > > > > > > > > Something like a pipeline? That is certainly a start, but if one > > > > > > pass is > > > > > > very slow wouldn't it bottleneck everything? > > > > > > > > > > Yes, something like a pipeline. It's true a slow pass would > > > > > bottleneck things - as said, we can selectively make passes > > > > > thread safe in such cases. > > > > > > > > > > > > Passes could of course be individually marked as thread-safe > > > > > > > (multiple instances execute concurrently). > > > > > > > > > > > > > > Garbage collection is already in control of the pass manager which > > > > > > > would also be the thread scheduler. For GC the remaining issue > > > > > > > is allocation which passes occasionally do. Locking is the short > > > > > > > term solution for GSoC I guess, long-term per-thread GC pools > > > > > > > might be better (to not slow down non-threaded parts of the > > > > > > > compiler). > > > > > > > > > > > > > > Richard. > > > > > > > > > > > > > > > > > > > > > > > Thank you, > > > > > > > > Giuliano. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > IIRC Richard [CCed] was going to mentor, with me > > > > > > > > > > co-mentoring [2] - but > > > > > > > > > > I don't know if he's still interested/able to spare the > > > > > > > > > > cycles. > > > > > > > > > > > > > > > > > > I've offered mentoring to Giuliano, so yes. > > > > > > > > > > > > > > > > > > > That said, the parallel compilation one strikes me as very > > > > > > > > > > ambitious; > > > > > > > > > > it's not clear to me what could realistically be done as a > > > > > > > > > > GSoC > > > > > > > > > > project. I think a good proposal on that would come up > > > > > > > > > > with some > > > > > > > > > > subset of the problem that's doable over a summer, whilst > > > > > > > > > > also being > > > > > > > > > > useful to the project. The RTL infrastructure has a lot of > > > > > > > > > > global > > > > > > > > > > state, so maybe either focus on the gimple passes, or on > > > > > > > > > > fixing global > > > > > > > > > > state on the RTL side? (I'm not sure) > > > > > > > > > > > > > > > > > > That was the original intent for the experiment. There's also > > > > > > > > > the already somewhat parallel WPA stage in LTO compilation > > > > > > > > > mode > > > > > > > > > (but it simply forks for the sake of simplicity...). > > > > > > > > > > > > > > > > > > > Or maybe a project to be more > > > > > > > > > > explicit about regions of the code that assume that the > > > > > > > > > > garbage- > > > > > > > > > > collector can't run within them?[3] (since the GC is state > > > > > > > > > > that would > > > > > > > > > > be shared by the threads). > > > > > > > > > > > > > > > > > > The GC will be one obstackle. The original idea was to drive > > > > > > > > > parallelization on the pass level by the pass manager for the > > > > > > > > > GIMPLE passes, so serialization points would be in it. > > > > > > > > > > > > > > > > > > Richard. > > > > > > > > > > > > > > > > > > > Hope this is constructive/helpful > > > > > > > > > > Dave > > > > > > > > > > > > > > > > > > > > [1] though typically our workflow involved sending patches > > > > > > > > > > to the gcc- > > > > > > > > > > patches mailing list > > > > > > > > > > [2] as libgccjit maintainer I have an interest in global > > > > > > > > > > state within > > > > > > > > > > the compiler > > > > > > > > > > [3] I posted some ideas about this back in 2013 IIRC; > > > > > > > > > > probably > > > > > > > > > > massively bit-rotted since then. I also gave a talk at > > > > > > > > > > Cauldron 2013 > > > > > > > > > > about global state in the compiler (with a view to > > > > > > > > > > gcc-as-a-shared- > > > > > > > > > > library); likewise I expect much of the ideas there to be > > > > > > > > > > out-of-date); > > > > > > > > > > for libgccjit I went with a different approach > > > > > > > > > > > > Thank you, > > > > > > Giuliano. > > > > > > > > > > > > > > > > -- > > > > > Richard Biener <rguent...@suse.de> > > > > > SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany; > > > > > GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG > > > > > Nürnberg) > > > > > > > > > > > > > > -- > > > Richard Biener <rguent...@suse.de> > > > SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany; > > > GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg) > > Giuliano. > > > > > > -- > Richard Biener <rguent...@suse.de> > SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany; > GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg) Thank you, Giuliano.
