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From: "burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/103416] [12 Regression][OpenMP] Bogus
 firstprivate(n) map(to:n [len: 4][implicit])
Date: Thu, 25 Nov 2021 10:07:00 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103416

--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> ---
(In reply to Chung-Lin Tang from comment #1)
> Can you see if adding this patch:
> https://gcc.gnu.org/pipermail/gcc-patches/2021-November/583279.html
> fixes this problem? If so, then it should be another occurrence of PR90030

Yes and no.

That patch FIXES the issue
  libgomp: cuCtxSynchronize error: misaligned address
  libgomp: cuMemFree_v2 error: misaligned address
  libgomp: device finalization failed


BUT I still see
  #pragma omp target map(to:D.4246 [len: 4][implicit]) ...

and when adding an explicit firstprivate(n) I see

 #pragma omp target firstprivate(n) map(to:D.4246 [len: 4][implicit]) ...

which looks wrong. I understand that implicit mapping tries to solve the
problem of explicitly mapping an array section via 'omp target (enter) data=
' -
and then implicitly mapping the whole array. =E2=80=94 But I think it does =
not make
sense to add this implicit mapping if there is an implicit or explicit
'firstprivate' for that variable. =E2=80=93 That's just generates pointless=
 code,
obfuscates the dump, adds an overhead to libgomp, ...


Actually, it does not only apply to 'firstprivate' - the same also can be
caused for 'tofrom' vs. 'to' as in

#pragma omp target ... map(to:D.4217 [len: 4][implicit]) map(tofrom:n [len:
4][implicit])


for the following code:

PROGRAM target_parallel_do
  implicit none
  INTEGER :: i0, N
  COMPLEX(8) :: scalar
  N =3D 1
  !$OMP TARGET PARALLEL do map(from: scalar) private(i0) defaultmap(tofrom)
  DO i0 =3D 1, N
    scalar%re =3D n
  END DO
  !$omp end target parallel do
END PROGRAM target_parallel_do


Admittedly, I have not yet managed to construct something which causes an
observable misbehavior.=