XLF: Compiler should detect and isolate the source of non-conforming Openmp code using local pointers for data maps.

SalesForce Case: TS001878905
PMR: 80808,227,000

The use case reproducer for this issue is an OpenMP Fortran implementation that uses local, temporary pointers to do data mapping. The implementation does not conform to the OpenMP spec but the compiler does not detect the non-conformance. An error condition is intermittently detected at runtime and the program is stopped without providing sufficient clues to isolate the cause to source code line number or variables.

This RFE requests that checks be added (perhaps enabled via a new option if there are performance impacts) to catch this kind of situation at compile-time and print messages to precisely point the user to the non-confirming/invalid source code causing the error.

Example runtime error message (from use case below) that does not identify source code line numbers or variables causing the error:

1587-168 Encountered a map that partially includes the memory of a prior map on the target device 0. The encountered map starts at host address 0x7fffffffc8e0 and the prior map starts at host address 0x7fffffffc8d8. The program will stop.

The following additional example code and explanation were provided by the XLF compiler developers:

! Map Group Sets

do setID=1,nGroupSets
GSet => Quad% GrpSetPtr(setID)

!$omp target enter data map(to: GSet)
!$omp target enter data map(to: GSet% STotal)
!$omp target enter data map(to: GSet% Sigt)
enddo

In the first iteration, pointer GSet is associated with Quad% GrpSetPtr(1) and then mapped to the device.
In the second iteration, association of GSet is changed from Quad% GrpSetPtr(1) to Quad% GrpSetPtr(2), while the corresponding attached pointer from the first map still exists on the device.

This violates the following rule in the OMP 5.0 specification [323: 8-10].
"A pointer that has a corresponding attached pointer and is associated with a given pointer target
must not become associated with a different pointer target for the duration of the lifetime of the
list item to which the corresponding pointer is attached in the device data environment."