Check array contiguity for OpenACC/Fortran

	PR fortran/93025

	gcc/fortran/
	* openmp.c (resolve_omp_clauses): Check array references for contiguity.

	gcc/testsuite/
	* gfortran.dg/goacc/mapping-tests-2.f90: New test.
	* gfortran.dg/goacc/subarrays.f95: Expect rejection of non-contiguous
	array.

gcc/fortran/ChangeLog

 2020-01-28  Julian Brown  <julian@codesourcery.com>
 
+	PR fortran/93025
+	* openmp.c (resolve_omp_clauses): Check array references for contiguity.
+
+2020-01-28  Julian Brown  <julian@codesourcery.com>
+
 	* gfortran.h (gfc_symbol): Add comp_mark bitfield.
 	* openmp.c (resolve_omp_clauses): Disallow mixed component and
 	full-derived-type accesses to the same variable within a single

gcc/fortran/openmp.c

@@ -4536,13 +4536,28 @@ resolve_omp_clauses (gfc_code *code, gfc_omp_clauses *omp_clauses,
 		    /* Look through component refs to find last array
 		       reference.  */
 		    if (openacc && resolved)
-		      while (array_ref
-			     && (array_ref->type == REF_COMPONENT
-				 || (array_ref->type == REF_ARRAY
-				     && array_ref->next
-				     && (array_ref->next->type
-					 == REF_COMPONENT))))
-			array_ref = array_ref->next;
+		      {
+			/* The "!$acc cache" directive allows rectangular
+			   subarrays to be specified, with some restrictions
+			   on the form of bounds (not implemented).
+			   Only raise an error here if we're really sure the
+			   array isn't contiguous.  An expression such as
+			   arr(-n:n,-n:n) could be contiguous even if it looks
+			   like it may not be.  */
+			if (list != OMP_LIST_CACHE
+			    && !gfc_is_simply_contiguous (n->expr, false, true)
+			    && gfc_is_not_contiguous (n->expr))
+			  gfc_error ("Array is not contiguous at %L",
+				     &n->where);
+
+			while (array_ref
+			       && (array_ref->type == REF_COMPONENT
+				   || (array_ref->type == REF_ARRAY
+				       && array_ref->next
+				       && (array_ref->next->type
+					   == REF_COMPONENT))))
+			  array_ref = array_ref->next;
+		      }
 		  }
 		if (array_ref
 		    || (n->expr

gcc/testsuite/ChangeLog

+2020-01-28  Tobias Burnus  <tobias@codesourcery.com>
+	    Julian Brown  <julian@codesourcery.com>
+
+	* gfortran.dg/goacc/mapping-tests-2.f90: New test.
+	* gfortran.dg/goacc/subarrays.f95: Expect rejection of non-contiguous
+	array.
+
 2020-01-28  Julian Brown  <julian@codesourcery.com>
 
 	* gfortran.dg/goacc/deep-copy-2.f90: Move test here (from libgomp

gcc/testsuite/gfortran.dg/goacc/mapping-tests-2.f90

+subroutine foo
+  type t
+    integer :: i, j
+  end type t
+
+  type t2
+    type(t) :: cc(3)
+  end type t2
+
+  type(t) x, y(3)
+  type(t2) :: z(3)
+
+  ! OK - map whole aggregated variable
+!$acc enter data copyin(x)
+  ! map(to:x [len: 8])
+
+  ! OK - map two components of the aggregated variable
+!$acc enter data copyin(x%j, x%i)
+
+  ! Bad - we cannot mix full-object and component accesses
+!$acc enter data copyin(x, x%i)
+! { dg-error "Symbol .x. has mixed component and non-component accesses" "" { target "*-*-*" } 21 }
+
+  ! Bad - we cannot do a strided access of 'x'
+  ! No C/C++ equivalent
+!$acc enter data copyin(y(:)%i)
+! { dg-error "Array is not contiguous" "" { target "*-*-*" } 26 }
+
+  ! Bad - again, a strided access
+!$acc enter data copyin(z(1)%cc(:)%i)
+! { dg-error "Array is not contiguous" "" { target "*-*-*" } 30 }
+end

gcc/testsuite/gfortran.dg/goacc/subarrays.f95

@@ -27,7 +27,7 @@ program test
   ! { dg-error "'a' in MAP clause" "" { target *-*-* } .-2 }
   !$acc end parallel
 
-  !$acc parallel copy (b(1:3,2:4))
+  !$acc parallel copy (b(1:3,2:4)) ! { dg-error "Array is not contiguous" }
   !$acc end parallel
   !$acc parallel copy (b(2:3))
   ! { dg-error "Rank mismatch" "" { target *-*-* } .-1 }