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From: "jules at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/113004] New: OpenMP 5 - structs are not mapped
 element-wise by default
Date: Wed, 13 Dec 2023 20:42:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113004

            Bug ID: 113004
           Summary: OpenMP 5 - structs are not mapped element-wise by
                    default
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jules at gcc dot gnu.org
  Target Milestone: ---

According to e.g. OpenMP 5.2, "5.8.2 Mapper Identifiers and mapper Modifier=
s":

"A structure type T has a predefined default mapper that is defined as if b=
y a
declare mapper directive that specifies v in a map clause with the alloc
map-type and each structure element of v in a map clause with the tofrom
map-type."

At present, a variable of struct type will be mapped as as a single block (=
the
pre-OpenMP 5.0 legacy behaviour).

This works fine most of the time, but for example fails in the case where o=
ne
of the struct's members is a reference, demonstrated in the test case:

  libgomp/testsuite/libgomp.c++/target-49.C

Once "declare mapper" support is committed, cases where a struct with an
implicit default mapper should invoke a struct with a *non*-default mapper,
will also probably be mishandled.=