Fix 'libgomp.fortran/reverse-offload-6.f90' nvptx offloading compilation (was: [Patch] libgomp: Fix reverse offload issues)

Hi Tobias!

On 2023-02-03T11:38:29+0100, Tobias Burnus <tobias@codesourcery.com> wrote:
> Now committed as obvious as
> r13-5680-g0b1ce70a813b98ef2893779d14ad6c90c5d06a71.

I see:

    FAIL: libgomp.fortran/reverse-offload-6.f90   -O  (test for excess errors)

... due to:

    nvptx mkoffload: warning: 'omp requires reverse_offload' requires at least 'sm_35' for '-foffload-options=nvptx-none=-march=' - disabling offload-code generation for this device type

I've pushed to master branch
commit 7ab75a6e6dfd81c566f848ef0d8d06666ee15b81
"Fix 'libgomp.fortran/reverse-offload-6.f90' nvptx offloading compilation",
see attached.


Grüße
 Thomas


> I improved the wording in the commit comment a bit, compared to previous
> attachment and I have verified that those features work with AMDGCN* and
> without offloading.
>
> Tobias
>
> (* it seems as if there is still another issue with mapping, this time
> for array-descriptor variables that do not exist on the host, i.e. that
> have to be fully mapped to the host. I will look into this today or Monday.)
>
> On 02.02.23 15:13, Tobias Burnus wrote:
>> Found when testing AMD GCN offloading, the second issue came up with
>> libgomp.fortran/reverse-offload-5.f90. (But oddly not with nvptx.)
>>
>> While the first one (new test: libgomp.fortran/reverse-offload-6.f90)
>> came up when debugging the issue.
>>
>> Tobias


> commit 0b1ce70a813b98ef2893779d14ad6c90c5d06a71
> Author: Tobias Burnus <tobias@codesourcery.com>
> Date:   Fri Feb 3 11:31:53 2023 +0100
>
>     libgomp: Fix reverse offload issues
>
>     If there is nothing to map, skip the mapping and avoid attempting to
>     copy 0 bytes from addrs, sizes and kinds.
>
>     Additionally, it could happen that a non-allocated address was deallocated,
>     such as a pointer set, leading to a free for the actual data.
>
>     libgomp/
>             * target.c (gomp_target_rev): Handle mapnum == 0 and avoid
>             freeing not allocated memory.
>             * testsuite/libgomp.fortran/reverse-offload-6.f90: New test.
> ---
>  libgomp/target.c                                   |  8 +++---
>  .../libgomp.fortran/reverse-offload-6.f90          | 32 ++++++++++++++++++++++
>  2 files changed, 36 insertions(+), 4 deletions(-)
>
> diff --git a/libgomp/target.c b/libgomp/target.c
> index b16ee761a95..c1682caea13 100644
> --- a/libgomp/target.c
> +++ b/libgomp/target.c
> @@ -3324,7 +3324,7 @@ gomp_target_rev (uint64_t fn_ptr, uint64_t mapnum, uint64_t devaddrs_ptr,
>      gomp_fatal ("Cannot find reverse-offload function");
>    void (*host_fn)() = (void (*)()) n->k->host_start;
>
> -  if (devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
> +  if ((devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM) || mapnum == 0)
>      {
>        devaddrs = (uint64_t *) (uintptr_t) devaddrs_ptr;
>        sizes = (uint64_t *) (uintptr_t) sizes_ptr;
> @@ -3402,7 +3402,7 @@ gomp_target_rev (uint64_t fn_ptr, uint64_t mapnum, uint64_t devaddrs_ptr,
>         }
>      }
>
> -  if (!(devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM))
> +  if (!(devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM) && mapnum > 0)
>      {
>        size_t j, struct_cpy = 0;
>        splay_tree_key n2;
> @@ -3638,7 +3638,7 @@ gomp_target_rev (uint64_t fn_ptr, uint64_t mapnum, uint64_t devaddrs_ptr,
>
>    host_fn (devaddrs);
>
> -  if (!(devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM))
> +  if (!(devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM) && mapnum > 0)
>      {
>        uint64_t struct_cpy = 0;
>        bool clean_struct = false;
> @@ -3680,7 +3680,7 @@ gomp_target_rev (uint64_t fn_ptr, uint64_t mapnum, uint64_t devaddrs_ptr,
>             clean_struct = true;
>             struct_cpy = sizes[i];
>           }
> -       else if (cdata[i].aligned)
> +       else if (!cdata[i].present && cdata[i].aligned)
>           gomp_aligned_free ((void *) (uintptr_t) devaddrs[i]);
>         else if (!cdata[i].present)
>           free ((void *) (uintptr_t) devaddrs[i]);
> diff --git a/libgomp/testsuite/libgomp.fortran/reverse-offload-6.f90 b/libgomp/testsuite/libgomp.fortran/reverse-offload-6.f90
> new file mode 100644
> index 00000000000..04866edbba7
> --- /dev/null
> +++ b/libgomp/testsuite/libgomp.fortran/reverse-offload-6.f90
> @@ -0,0 +1,32 @@
> +!
> +! Ensure that a mapping with no argument works
> +!
> +
> +module m
> +  implicit none (type, external)
> +  integer :: x = 32
> +  integer :: dev_num2 = -1
> +contains
> +subroutine  foo()
> +  use omp_lib, only: omp_get_device_num
> +  x = x + 10
> +  dev_num2 = omp_get_device_num()
> +end
> +end module m
> +
> +use m
> +use omp_lib
> +!$omp requires reverse_offload
> +implicit none (type, external)
> +integer :: dev_num = -1
> +!$omp target map(from:dev_num)
> +  dev_num = omp_get_device_num()
> +  ! This calls GOMP_target_ext with number of maps = 0
> +  !$omp target device(ancestor:1)
> +    call foo
> +  !$omp end target
> +!$omp end target
> +
> +if (omp_get_num_devices() > 0 .and.  dev_num2 == dev_num) stop 1
> +if (x /= 42) stop 2
> +end


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