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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug fortran/102043] Wrong array types used for negative stride accesses Date: Mon, 22 Nov 2021 07:46:56 +0000 [thread overview] Message-ID: <bug-102043-4-KeY8G3KDyl@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-102043-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102043 --- Comment #24 from rguenther at suse dot de <rguenther at suse dot de> --- On Fri, 19 Nov 2021, mikael at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102043 > > --- Comment #23 from Mikael Morin <mikael at gcc dot gnu.org> --- > (In reply to Richard Biener from comment #21) > > (In reply to Bernhard Reutner-Fischer from comment #17) > > > Do we want to address arrays always at position 0 (maybe to help graphite ?) > > > > Helping graphite (and other loop optimizers) would be to not lower > > multi-dimensional accesses to a single dimension (I think that's what > > Sandras patches try to do). > > Or maybe graphite can be taught to handle flattened array access? > > Anyway, does the middle-end support out-of-order array access? > Namely for an array arr(4, 5, 6), arr(:, 1, :) is an array of size (4, 6). > Does the middle-end type system support this? Support as in not miscompile - yes. Dependence analysis is only helped if the shapes of the accesses to the same storage are compatible - a two dimensional and a three dimensional access are not. > In any case, it’s not for gcc 12. Agreed. > > The lower bound doesn't really matter here and > > is well-handled by all code. > > Well, unless the lower bound is negative. ;-) Even a negative lower bound is OK. Problematic is only if you provide an index that accesses the array below the (negative) lower bound ;) But note! In GCC a[i] with a having a lower bound of say -100 will access storage at &a + (i - -100), the lower bound is just to make the effective index >= 0 again, so it can't be used (on its own) to solve the present issue as far as I understand since you _do_ need to access the storage at an effective index < 0.
next prev parent reply other threads:[~2021-11-22 7:46 UTC|newest] Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-24 14:18 [Bug fortran/102043] New: " rguenth at gcc dot gnu.org 2021-08-25 8:42 ` [Bug fortran/102043] " rguenth at gcc dot gnu.org 2021-08-25 9:16 ` rguenth at gcc dot gnu.org 2021-08-25 10:05 ` ebotcazou at gcc dot gnu.org 2021-08-25 10:07 ` rguenth at gcc dot gnu.org 2021-08-25 10:20 ` rguenth at gcc dot gnu.org 2021-09-30 19:56 ` anlauf at gcc dot gnu.org 2021-11-08 21:23 ` hubicka at gcc dot gnu.org 2021-11-10 16:31 ` mikael at gcc dot gnu.org 2021-11-10 17:12 ` aldot at gcc dot gnu.org 2021-11-11 8:00 ` rguenth at gcc dot gnu.org 2021-11-12 18:14 ` tkoenig at gcc dot gnu.org 2021-11-12 19:30 ` mikael at gcc dot gnu.org 2021-11-14 7:57 ` tkoenig at gcc dot gnu.org 2021-11-14 9:33 ` mikael at gcc dot gnu.org 2021-11-14 9:38 ` tkoenig at gcc dot gnu.org 2021-11-14 16:07 ` aldot at gcc dot gnu.org 2021-11-14 16:18 ` aldot at gcc dot gnu.org 2021-11-14 17:00 ` mikael at gcc dot gnu.org 2021-11-14 17:13 ` mikael at gcc dot gnu.org 2021-11-14 19:42 ` tkoenig at gcc dot gnu.org 2021-11-15 10:47 ` rguenth at gcc dot gnu.org 2021-11-19 18:21 ` mikael at gcc dot gnu.org 2021-11-19 18:31 ` mikael at gcc dot gnu.org 2021-11-22 7:46 ` rguenther at suse dot de [this message] 2021-11-22 22:33 ` hubicka at gcc dot gnu.org 2021-11-27 21:43 ` mikael at gcc dot gnu.org 2021-12-11 17:47 ` mikael at gcc dot gnu.org 2021-12-11 17:53 ` mikael at gcc dot gnu.org 2021-12-12 17:04 ` mikael at gcc dot gnu.org 2021-12-12 21:26 ` mikael at gcc dot gnu.org 2022-01-03 9:09 ` rguenth at gcc dot gnu.org 2022-01-03 9:12 ` rguenth at gcc dot gnu.org 2022-03-24 9:39 ` [Bug fortran/102043] [9/10/11/12 Regression] Wrong array types used for negative stride accesses, gfortran.dg/vector_subscript_1.f90 FAILs rguenth at gcc dot gnu.org 2022-03-24 16:40 ` tschwinge at gcc dot gnu.org 2022-03-27 19:36 ` mikael at gcc dot gnu.org 2022-03-28 6:36 ` rguenther at suse dot de 2022-03-28 12:16 ` rguenth at gcc dot gnu.org 2022-03-28 12:24 ` burnus at gcc dot gnu.org 2022-03-30 6:45 ` tkoenig at gcc dot gnu.org 2022-03-30 6:48 ` rguenther at suse dot de 2022-03-30 9:07 ` rguenth at gcc dot gnu.org 2022-03-30 11:22 ` rguenth at gcc dot gnu.org 2022-04-05 10:21 ` mikael at gcc dot gnu.org 2022-04-22 20:53 ` cvs-commit at gcc dot gnu.org 2022-04-22 20:53 ` cvs-commit at gcc dot gnu.org 2022-04-22 20:53 ` cvs-commit at gcc dot gnu.org 2022-04-22 20:53 ` cvs-commit at gcc dot gnu.org 2022-04-25 6:07 ` [Bug fortran/102043] [9/10/11 " rguenth at gcc dot gnu.org 2022-04-27 9:36 ` cvs-commit at gcc dot gnu.org 2022-05-27 9:46 ` [Bug fortran/102043] [10/11 " rguenth at gcc dot gnu.org 2022-06-28 10:46 ` jakub at gcc dot gnu.org 2022-08-28 10:36 ` mikael at gcc dot gnu.org 2022-08-28 10:37 ` mikael at gcc dot gnu.org 2023-07-07 10:40 ` [Bug fortran/102043] [11 " rguenth at gcc dot gnu.org
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