[flang][OpenMP] Declare Mapper does not map base type members properly

[jfuchs-kmt]

I am using the most recent flang version 22.0.0git (git@github.com:llvm/llvm-project.git 89f53af3fffed3e41167fbb7bc10d4885cd97c7f).

The reproducer below shows that when using a custom declare mapper for real_t, then even when we specify t%base_arr within the mapper, the array is not mapped properly in a target region.

I am compiling this reproducer with flang -O2 -fopenmp -fopenmp-version=52 -fopenmp-targets=nvptx64-nvidia-cuda main.F90 and run it with OMP_TARGET_OFFLOAD=mandatory ./a.out.

PROGRAM reproducer
    IMPLICIT NONE

    TYPE, ABSTRACT :: base_t
        REAL, ALLOCATABLE :: base_arr(:)
    END TYPE base_t

    TYPE, EXTENDS(base_t) :: real_t
        REAL, ALLOCATABLE :: real_arr(:)
    END TYPE real_t
    !$omp declare mapper(custommapper: real_t :: t) map(t%base_arr, t%real_arr)

    TYPE(real_t) :: r
    ALLOCATE(r%base_arr(10), source=1.0)
    ALLOCATE(r%real_arr(10), source=1.0)

    PRINT*, "BEFORE TARGET REGION:"
    PRINT*, "base_arr: ", r%base_arr
    PRINT*, "real_arr: ", r%real_arr
    PRINT*, ""

    !$omp target map(tofrom: r)
        r%base_arr = 2.0 ! This write has no effect since base_arr is not mapped properly
        r%real_arr = 3.0 ! This is fine
        !r%real_arr = r%base_arr(1) ! UNCOMMENT THIS --> results in (core dumped) since we read from an unmapped base_arr
    !$omp end target

    PRINT*, "AFTER TARGET REGION:"
    PRINT*, "base_arr: ", r%base_arr ! We would expect "2. ..." here
    PRINT*, "real_arr: ", r%real_arr

    DEALLOCATE(r%real_arr)
    DEALLOCATE(r%base_arr)
END PROGRAM reproducer

The error message when reading from base_arr(1) by uncommenting the third line in the target region is:

"PluginInterface" error: Failure to copy data from device to host. Pointers: host = 0x000064a6f0418ab0, device = 0x00007ac120a00200, size = 40: "unknown or internal error" error in cuMemcpyDtoHAsync: an illegal memory access was encountered
omptarget error: Copying data from device failed.
omptarget error: Call to targetDataEnd failed, abort target.
omptarget error: Failed to process data after launching the kernel.
omptarget error: Consult https://openmp.llvm.org/design/Runtimes.html for debugging options.
omptarget error: Source location information not present. Compile with -g or -gline-tables-only.
omptarget fatal error 1: failure of target construct while offloading is mandatory
Aborted (core dumped)

[kiranchandramohan]

@TIFitis @agozillon : You might be interested in this mapping bug.

[agozillon]

Thank you, don't know if we've looked into this case in general yet for the regular mapping (i.e. if you moved the custom mapper onto a regular map on the target region). But there's also a lot missing from upstream still with regards to mapping that we're slowly upstreaming.

[TIFitis]

Thanks for reporting, I'll look into this and update.

[TIFitis]

As is, the declare mapper has no effect on the code.

Either change it to a default declare mapper or add the mapper(custommapper) modifier to the target map clause.

Combining this change with #160116 lets the test run without errors.

[llvmbot]

@llvm/issue-subscribers-flang-ir

Author: None (jfuchs-kmt)

I am using the most recent `flang version 22.0.0git (git@github.com:llvm/llvm-project.git 89f53af)`.

The reproducer below shows that when using a custom declare mapper for real_t, then even when we specify t%base_arr within the mapper, the array is not mapped properly in a target region.

I am compiling this reproducer with flang -O2 -fopenmp -fopenmp-version=52 -fopenmp-targets=nvptx64-nvidia-cuda main.F90 and run it with OMP_TARGET_OFFLOAD=mandatory ./a.out.

PROGRAM reproducer
    IMPLICIT NONE

    TYPE, ABSTRACT :: base_t
        REAL, ALLOCATABLE :: base_arr(:)
    END TYPE base_t

    TYPE, EXTENDS(base_t) :: real_t
        REAL, ALLOCATABLE :: real_arr(:)
    END TYPE real_t
    !$omp declare mapper(custommapper: real_t :: t) map(t%base_arr, t%real_arr)

    TYPE(real_t) :: r
    ALLOCATE(r%base_arr(10), source=1.0)
    ALLOCATE(r%real_arr(10), source=1.0)

    PRINT*, "BEFORE TARGET REGION:"
    PRINT*, "base_arr: ", r%base_arr
    PRINT*, "real_arr: ", r%real_arr
    PRINT*, ""

    !$omp target map(tofrom: r)
        r%base_arr = 2.0 ! This write has no effect since base_arr is not mapped properly
        r%real_arr = 3.0 ! This is fine
        !r%real_arr = r%base_arr(1) ! UNCOMMENT THIS --> results in (core dumped) since we read from an unmapped base_arr
    !$omp end target

    PRINT*, "AFTER TARGET REGION:"
    PRINT*, "base_arr: ", r%base_arr ! We would expect "2. ..." here
    PRINT*, "real_arr: ", r%real_arr

    DEALLOCATE(r%real_arr)
    DEALLOCATE(r%base_arr)
END PROGRAM reproducer

The error message when reading from base_arr(1) by uncommenting the third line in the target region is:

"PluginInterface" error: Failure to copy data from device to host. Pointers: host = 0x000064a6f0418ab0, device = 0x00007ac120a00200, size = 40: "unknown or internal error" error in cuMemcpyDtoHAsync: an illegal memory access was encountered
omptarget error: Copying data from device failed.
omptarget error: Call to targetDataEnd failed, abort target.
omptarget error: Failed to process data after launching the kernel.
omptarget error: Consult https://openmp.llvm.org/design/Runtimes.html for debugging options.
omptarget error: Source location information not present. Compile with -g or -gline-tables-only.
omptarget fatal error 1: failure of target construct while offloading is mandatory
Aborted (core dumped)