[PATCH, OpenMP] Fix nested use_device_ptr

[PATCH, OpenMP] Fix nested use_device_ptr

[Chung-Lin Tang]

[-- Attachment #1: Type: text/plain, Size: 997 bytes --]

Hi Jakub,
this patch fixes a bug in lower_omp_target, where for Fortran arrays,
the expanded sender assignment is wrongly using the variable in the
current ctx, instead of the one looked-up outside, which is causing
use_device_ptr/addr to fail to work when used inside an omp-parallel
(where the omp child_fn is split away from the original).
Just a one-character change to fix this.

The fix is inside omp-low.cc, though because the omp_array_data langhook
is used only by Fortran, this is essentially Fortran-specific.

Tested on x86_64-linux + nvptx offloading without regressions.
This is probably not a regression, but seeking to commit when stage1 opens.

Thanks,
Chung-Lin

2022-04-01  Chung-Lin Tang  <cltang@codesourcery.com>

gcc/ChangeLog:

	* omp-low.cc (lower_omp_target): Use outer context looked-up 'var' as
	argument to lang_hooks.decls.omp_array_data, instead of 'ovar' from
	current clause.
	
libgomp/ChangeLog:

	* testsuite/libgomp.fortran/use_device_ptr-4.f90: New testcase.


[-- Attachment #2: omp101.patch --]
[-- Type: text/plain, Size: 1824 bytes --]

diff --git a/gcc/omp-low.cc b/gcc/omp-low.cc
index 392bb18..bf5779b 100644
--- a/gcc/omp-low.cc
+++ b/gcc/omp-low.cc
@@ -13405,7 +13405,7 @@ lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 
 	    type = TREE_TYPE (ovar);
 	    if (lang_hooks.decls.omp_array_data (ovar, true))
-	      var = lang_hooks.decls.omp_array_data (ovar, false);
+	      var = lang_hooks.decls.omp_array_data (var, false);
 	    else if (((OMP_CLAUSE_CODE (c) == OMP_CLAUSE_USE_DEVICE_ADDR
 		      || OMP_CLAUSE_CODE (c) == OMP_CLAUSE_HAS_DEVICE_ADDR)
 		      && !omp_privatize_by_reference (ovar)
diff --git a/libgomp/testsuite/libgomp.fortran/use_device_ptr-4.f90 b/libgomp/testsuite/libgomp.fortran/use_device_ptr-4.f90
new file mode 100644
index 0000000..8c361d1
--- /dev/null
+++ b/libgomp/testsuite/libgomp.fortran/use_device_ptr-4.f90
@@ -0,0 +1,41 @@
+! { dg-do run }
+!
+! Test user_device_ptr nested within another parallel
+! construct
+!
+program test_nested_use_device_ptr
+  use iso_c_binding, only: c_loc, c_ptr
+  implicit none
+  real, allocatable, target :: arr(:,:)
+  integer :: width = 1024, height = 1024, i
+  type(c_ptr) :: devptr
+
+  allocate(arr(width,height))
+
+  !$omp target enter data map(alloc: arr)
+
+  !$omp target data use_device_ptr(arr)
+  devptr = c_loc(arr(1,1))
+  !$omp end target data
+
+  !$omp parallel default(none) shared(arr, devptr)
+  !$omp single
+
+  !$omp target data use_device_ptr(arr)
+  call thing(c_loc(arr), devptr)
+  !$omp end target data
+
+  !$omp end single
+  !$omp end parallel
+  !$omp target exit data map(delete: arr)
+
+contains
+
+  subroutine thing(myarr, devptr)
+    use iso_c_binding, only: c_ptr, c_associated
+    implicit none
+    type(c_ptr) :: myarr, devptr
+    if (.not.c_associated(myarr, devptr)) stop 1
+  end subroutine thing
+
+end program

Re: [PATCH, OpenMP] Fix nested use_device_ptr

[Jakub Jelinek]

On Fri, Apr 01, 2022 at 05:02:36PM +0800, Chung-Lin Tang wrote:
> this patch fixes a bug in lower_omp_target, where for Fortran arrays,
> the expanded sender assignment is wrongly using the variable in the
> current ctx, instead of the one looked-up outside, which is causing
> use_device_ptr/addr to fail to work when used inside an omp-parallel
> (where the omp child_fn is split away from the original).
> Just a one-character change to fix this.
> 
> The fix is inside omp-low.cc, though because the omp_array_data langhook
> is used only by Fortran, this is essentially Fortran-specific.
> 
> Tested on x86_64-linux + nvptx offloading without regressions.
> This is probably not a regression, but seeking to commit when stage1 opens.
> 
> Thanks,
> Chung-Lin
> 
> 2022-04-01  Chung-Lin Tang  <cltang@codesourcery.com>
> 
> gcc/ChangeLog:
> 
> 	* omp-low.cc (lower_omp_target): Use outer context looked-up 'var' as
> 	argument to lang_hooks.decls.omp_array_data, instead of 'ovar' from
> 	current clause.
> 	
> libgomp/ChangeLog:
> 
> 	* testsuite/libgomp.fortran/use_device_ptr-4.f90: New testcase.

Ok, thanks.

	Jakub