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[gomp4] fix an ICE involving assumed-size arrays

Message ID 7a479500-a8ef-7783-a4bb-9910dcb78848@codesourcery.com
State New
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Commit Message

Cesar Philippidis Aug. 30, 2016, 9:55 p.m. UTC 
Usually a data clause would would have OMP_CLAUSE_SIZE set, but not all
do. In the latter case, lower_omp_target falls back to using size of the
type of the variable specified in the data clause. However, in the case
of assumed-size arrays, the size of the type may be NULL because its
undefined. My fix for this solution is to set the size to one byte if
the size of the type is NULL. This solution at least allows the runtime
the opportunity to remap any data already present on the accelerator.
However, if the data isn't present on the accelerator, this will likely
result in some sort of segmentation fault on the accelerator.

The OpenACC spec is not clear how the compiler should handle
assumed-sized arrays when the user does not provide an explicit data
clause with a proper subarray. It was tempting to make such implicit
variables errors, but arguably that would affect usability. Perhaps I
should a warning for implicitly used assumed-sizes arrays?

I've applied this patch to gomp-4_0-branch. It looks like OpenMP has a
similar problem.

Cesar
diff mbox

Patch

2016-08-30  Cesar Philippidis  <cesar@codesourcery.com>

	gcc/
	* omp-low.c (lower_omp_target): Handle NULL-sized types for
	assumed-sized arrays.

	libgomp/
	* testsuite/libgomp.oacc-fortran/assumed-size.f90: New test.


diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index b314523..0faf6c3 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -16534,6 +16534,12 @@  lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 	      s = OMP_CLAUSE_SIZE (c);
 	    if (s == NULL_TREE)
 	      s = TYPE_SIZE_UNIT (TREE_TYPE (ovar));
+	    /* Fortran assumed-size arrays have zero size because the
+	       type is incomplete.  Set the size to one to allow the
+	       runtime to remap any existing data that is already
+	       present on the accelerator.  */
+	    if (s == NULL_TREE)
+	      s = integer_one_node;
 	    s = fold_convert (size_type_node, s);
 	    purpose = size_int (map_idx++);
 	    CONSTRUCTOR_APPEND_ELT (vsize, purpose, s);
diff --git a/libgomp/testsuite/libgomp.oacc-fortran/assumed-size.f90 b/libgomp/testsuite/libgomp.oacc-fortran/assumed-size.f90
new file mode 100644
index 0000000..79de675
--- /dev/null
+++ b/libgomp/testsuite/libgomp.oacc-fortran/assumed-size.f90
@@ -0,0 +1,31 @@ 
+! Test if implicitly determined data clauses work with an
+! assumed-sized array variable.  Note that the array variable, 'a',
+! has been explicitly copied in and out via acc enter data and acc
+! exit data, respectively.
+
+program test
+  implicit none
+
+  integer, parameter :: n = 100
+  integer a(n), i
+
+  call dtest (a, n)
+
+  do i = 1, n
+     if (a(i) /= i) call abort
+  end do
+end program test
+
+subroutine dtest (a, n)
+  integer i, n
+  integer a(*)
+
+  !$acc enter data copyin(a(1:n))
+
+  !$acc parallel loop
+  do i = 1, n
+     a(i) = i
+  end do
+
+  !$acc exit data copyout(a(1:n))
+end subroutine dtest