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From: "vries at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/95654] nvptx offloading: FAIL: libgomp.fortran/pr66199-5.f90 -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions execution test
Date: Thu, 17 Sep 2020 10:20:05 +0000 [thread overview]
Message-ID: <bug-95654-4-mLvwnBtpJz@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-95654-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95654
Tom de Vries <vries at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rguenth at gcc dot gnu.org
--- Comment #11 from Tom de Vries <vries at gcc dot gnu.org> ---
So, at this point we know that duplicating the BB containing VOTE_ANY causes
problems in executing. But AFAIU, we do not know why.
Is VOTE_ANY not supposed to be duplicated by design? If so, is there any
documentation of that design, that explains that?
At the nvptx level, VOTE_ANY translates to vote.ballot.b32, which does
cross-lane communication, but has defined behaviour in divergent mode AFAICT.
>From that perspective at least, there's no problem with duplicating VOTE_ANY.
My guess at this point, is that duplicating the block with VOTE_ANY has the
effect that the JIT compiler doesn't recognize control flow divergence before
XCHG_IDX, and fails to insert the proper barrier.
And XCHG_IDX translates to shfl.idx.b32, which has undefined behaviour in
divergent mode.
next prev parent reply other threads:[~2020-09-17 10:20 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-12 11:33 [Bug fortran/95654] New: " tschwinge at gcc dot gnu.org
2020-06-12 14:18 ` [Bug fortran/95654] " tschwinge at gcc dot gnu.org
2020-06-12 15:40 ` burnus at gcc dot gnu.org
2020-09-09 11:27 ` burnus at gcc dot gnu.org
2020-09-15 23:29 ` burnus at gcc dot gnu.org
2020-09-16 7:24 ` burnus at gcc dot gnu.org
2020-09-16 13:23 ` vries at gcc dot gnu.org
2020-09-16 13:33 ` vries at gcc dot gnu.org
2020-09-16 15:54 ` vries at gcc dot gnu.org
2020-09-16 15:57 ` vries at gcc dot gnu.org
2020-09-16 21:11 ` burnus at gcc dot gnu.org
2020-09-17 9:33 ` burnus at gcc dot gnu.org
2020-09-17 10:20 ` vries at gcc dot gnu.org [this message]
2020-09-17 13:53 ` vries at gcc dot gnu.org
2020-09-17 15:19 ` vries at gcc dot gnu.org
2020-09-22 17:16 ` cvs-commit at gcc dot gnu.org
2020-09-25 8:55 ` burnus at gcc dot gnu.org
2020-10-05 6:54 ` cvs-commit at gcc dot gnu.org
2020-10-05 7:01 ` vries at gcc dot gnu.org
2020-10-05 7:01 ` vries at gcc dot gnu.org
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