For C/C++ pointers, default implicit mapping firstprivatizes the pointer
but if the memory it points to is mapped, the it is updated to point to
the device memory (by attaching a zero sized array section of the pointed-to
storage).
However, if the pointed-to storage wasn't mapped, the pointer was set to
NULL on the device side (OpenMP 5.0/5.1 semantic). With this commit, the
pointer retains the on-host address in that case (OpenMP 5.2 semantic).
The new semantic avoids an explicit map/firstprivate/is_device_ptr in the
following sensible cases: Special values (e.g. pointer or 0x1, 0x2 etc.),
explicitly device allocated memory (e.g. omp_target_alloc), and with
(unified) shared memory.
(Note: With (U)SM, mappings still must be tracked, at least when
omp_target_associate_ptr does not fail when passing in two destinct pointers.)
libgomp/
PR middle-end/110270
* target.c (gomp_map_vars_internal): Copy host value instead of NULL
for GOMP_MAP_ZERO_LEN_ARRAY_SECTION if not mapped.
* libgomp.texi (OpenMP 5.2 Impl.): Mark as 'Y'.
* testsuite/libgomp.c/target-19.c: Update expected value.
* testsuite/libgomp.c++/target-18.C: Likewise.
* testsuite/libgomp.c++/target-19.C: Likewise.
* testsuite/libgomp.c-c++-common/requires-unified-addr-2.c: New test.
* testsuite/libgomp.c-c++-common/target-implicit-map-3.c: New test.
* testsuite/libgomp.c-c++-common/target-implicit-map-4.c: New test.
