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From: "burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/50564] [4.7 Regression] Front-end optimization - ICE with FORALL
Date: Sun, 09 Oct 2011 16:01:00 -0000	[thread overview]
Message-ID: <bug-50564-4-yEA0F3aHZH@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-50564-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50564

--- Comment #5 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-10-09 16:00:41 UTC ---
(In reply to comment #4)
> So, the best method is to disable front-end optimization within
> a forall loop.
> 
> I assume the same holds for DO CONCURRENT.

I think do concurrent is OK - here, the same as with a DO loop applies -- only
the user has to guarantee that the loop will yield the same result independent
of the execution order of the bounds.

However, I think the current FE optimization might have problems with
threadsafety. Assume:

!$OMP parallel do default(share)
do i = 1, 5
  A(i) = 5*cos(B(i))+8*cos(B(i))
end do

If one now transforms this into:

!$OMP parallel do default(share)
do i = 1, 5
  tmp = cos(B(i))
  A(i) = 5*tmp+8*tmp
end do

one has a problem as "tmp" is shared. Thus, one needs to make sure that all
inserted temporary variables are thread private (DECL_THREAD_LOCAL_P).


  parent reply	other threads:[~2011-10-09 16:01 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-29  8:21 [Bug fortran/50564] New: " burnus at gcc dot gnu.org
2011-09-29  8:35 ` [Bug fortran/50564] " burnus at gcc dot gnu.org
2011-09-29 13:10 ` burnus at gcc dot gnu.org
2011-09-30  6:01 ` tkoenig at gcc dot gnu.org
2011-09-30  9:30 ` burnus at gcc dot gnu.org
2011-10-08  9:31 ` tkoenig at gcc dot gnu.org
2011-10-08 21:41 ` tkoenig at gcc dot gnu.org
2011-10-09 16:01 ` burnus at gcc dot gnu.org [this message]
2011-10-09 16:15 ` burnus at gcc dot gnu.org
2011-10-09 18:11 ` tkoenig at netcologne dot de
2011-10-10  9:24 ` burnus at gcc dot gnu.org
2011-10-10 14:28 ` rguenth at gcc dot gnu.org
2011-10-10 18:57 ` tkoenig at netcologne dot de
2011-10-10 19:09 ` tkoenig at gcc dot gnu.org
2011-10-10 19:15 ` tkoenig at gcc dot gnu.org

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