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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/102997] [12 Regression] 45% 454.calculix regression with LTO+PGO -march=native -Ofast on Zen since r12-4526-gd8edfadfc7a9795b65177a50ce44fd348858e844 Date: Mon, 08 Nov 2021 15:34:17 +0000 [thread overview] Message-ID: <bug-102997-4-VlyRZ13ZKq@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-102997-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102997 --- Comment #27 from Aldy Hernandez <aldyh at gcc dot gnu.org> --- (In reply to Richard Biener from comment #20) > (In reply to hubicka from comment #19) > > The testcase would be > > > > void test () > > { > > int i; > > if (test()) > > i=0; > > else > > i=100; > > for (;i<100 && bar ();i++) > > do_work (); > > } Updated test that compiles: int check(); int bar (); void do_work (); void test () { int i; if (check()) i=0; else i=100; for (;i<100 && bar ();i++) do_work (); } > > > > Here I think we can thread else path to return w/o any issues with loop > > nests even with -Os. > > we fail this because > > // If we crossed a loop into an outer loop without crossing the > // latch, this is just an early exit from the loop. > if (loops_crossed == 1 > && !crossed_latch > && flow_loop_nested_p (exit->dest->loop_father, > exit->src->loop_father)) > return false; > > does not trigger (loops_crossed == 2), and we then run into > > > if (loops_crossed) > { > cancel_thread (&path, "Path crosses loops"); > return true; > } > > but the loops_crossed stuff is old and not from me, not sure what that's > useful for. We could "fix" the accounting with > > diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c > index 8aac733ac25..52ec22e85e1 100644 > --- a/gcc/tree-ssa-threadupdate.c > +++ b/gcc/tree-ssa-threadupdate.c > @@ -2810,7 +2810,7 @@ jt_path_registry::cancel_invalid_paths > (vec<jump_thread_edge *> &path) > > // If we crossed a loop into an outer loop without crossing the > // latch, this is just an early exit from the loop. > - if (loops_crossed == 1 > + if (loops_crossed <= 2 > && !crossed_latch > && flow_loop_nested_p (exit->dest->loop_father, > exit->src->loop_father)) > return false; The above patch doesn't cause any difference in the generated code, at least for -O2. I also don't see any more paths registered: $ grep Registering.jump a.c.* a.c.126t.thread1: [1] Registering jump thread: (2, 4) incoming edge; (4, 8) nocopy; a.c.126t.thread1: [2] Registering jump thread: (3, 4) incoming edge; (4, 7) nocopy; a.c.192t.dom3: [4] Registering jump thread: (6, 5) incoming edge; (5, 4) joiner (4, 7) normal; > > to also allow to thread through a loop path not crossing the latch but > at least for the issue of "breaking loops" the loops_crossed stuff shouldn't > be necessary. It might still prevent us from doing such transforms when > it involves peeling. This loops crossing stuff is indeed quite old. Are you suggesting this as well? - if (loops_crossed) - { - cancel_thread (&path, "Path crosses loops"); - return true; - } Which, BTW doesn't change the behavior for this test, but I'm happy to test if you think it's not necessary.
next prev parent reply other threads:[~2021-11-08 15:34 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-10-29 10:05 [Bug middle-end/102997] New: 45% calculix regression with LTO+PGO -march=native -Ofast between ce4d1f632ff3f680550d3b186b60176022f41190 and 6fca1761a16c68740f875fc487b98b6bde8e9be7 on Zen hubicka at gcc dot gnu.org 2021-10-29 10:42 ` [Bug middle-end/102997] [12 Regression] 45% 454.calculix " rguenth at gcc dot gnu.org 2021-10-29 11:43 ` Jan Hubicka 2021-10-29 10:55 ` rguenth at gcc dot gnu.org 2021-10-29 11:00 ` rguenth at gcc dot gnu.org 2021-10-29 11:38 ` hubicka at kam dot mff.cuni.cz 2021-10-29 11:43 ` hubicka at kam dot mff.cuni.cz 2021-11-01 10:10 ` marxin at gcc dot gnu.org 2021-11-01 10:18 ` marxin at gcc dot gnu.org 2021-11-01 12:42 ` [Bug middle-end/102997] [12 Regression] 45% 454.calculix regression with LTO+PGO -march=native -Ofast on Zen since r12-4526-gd8edfadfc7a9795b65177a50ce44fd348858e844 marxin at gcc dot gnu.org 2021-11-01 15:05 ` aldyh at gcc dot gnu.org 2021-11-01 16:33 ` hubicka at kam dot mff.cuni.cz 2021-11-08 7:40 ` aldyh at gcc dot gnu.org 2021-11-08 7:43 ` aldyh at gcc dot gnu.org 2021-11-08 8:06 ` aldyh at gcc dot gnu.org 2021-11-08 8:24 ` marxin at gcc dot gnu.org 2021-11-08 8:25 ` rguenther at suse dot de 2021-11-08 8:33 ` Jan Hubicka 2021-11-08 8:33 ` hubicka at kam dot mff.cuni.cz 2021-11-08 8:34 ` aldyh at gcc dot gnu.org 2021-11-08 8:40 ` aldyh at gcc dot gnu.org 2021-11-08 8:51 ` hubicka at kam dot mff.cuni.cz 2021-11-08 9:50 ` rguenth at gcc dot gnu.org 2021-11-08 11:44 ` hubicka at kam dot mff.cuni.cz 2021-11-08 13:00 ` rguenther at suse dot de 2021-11-08 13:16 ` hubicka at kam dot mff.cuni.cz 2021-11-08 14:05 ` rguenther at suse dot de 2021-11-08 14:10 ` rguenth at gcc dot gnu.org 2021-11-08 14:19 ` rguenth at gcc dot gnu.org 2021-11-08 15:34 ` aldyh at gcc dot gnu.org [this message] 2021-11-09 7:26 ` rguenther at suse dot de 2021-11-12 13:42 ` marxin at gcc dot gnu.org 2021-11-12 13:56 ` rguenth at gcc dot gnu.org 2021-11-12 16:05 ` hubicka at kam dot mff.cuni.cz
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