Fix PR72715 "ICE in gfc_trans_omp_do, at fortran/trans-openmp.c:3164"

The OpenACC 'resolve_oacc_nested_loops' function duplicates most code of the
OpenMP 'resolve_omp_do', but didn't include the PR60127 "ICE with OpenMP and DO
CONCURRENT" (trunk r210331) changes.  (Probably the two functions should be
unified?)

The Fortran DO CONCURRENT construct is a way to tell the compiler that loop
iterations don't have any interdependencies -- which is information that would
very well be suitable for OpenACC/OpenMP loops.  There are some "details"
however, see the discussion/references in PR60127, so for the time being, make
this a compile-time error instead of an ICE.

	gcc/fortran/
	* openmp.c (resolve_oacc_nested_loops): Error on do concurrent
	loops.

	gcc/testsuite/
	* gfortran.dg/goacc/loop-3-2.f95: Error on do concurrent loops.
	* gfortran.dg/goacc/loop-3.f95: Likewise.
	* gfortran.dg/goacc/pr72715.f90: New test.

Reviewed-by: Thomas Schwinge <thomas@codesourcery.com>

From-SVN: r268875

gcc/fortran/ChangeLog

+2019-02-14  Cesar Philippidis  <cesar@codesourcery.com>
+
+	PR fortran/72715
+	* openmp.c (resolve_oacc_nested_loops): Error on do concurrent
+	loops.
+
 2019-02-13  Martin Liska  <mliska@suse.cz>
 
 	PR fortran/88649

gcc/fortran/openmp.c

@@ -5760,7 +5760,13 @@ resolve_oacc_nested_loops (gfc_code *code, gfc_code* do_code, int collapse,
 		     "at %L", &do_code->loc);
 	  break;
 	}
-      gcc_assert (do_code->op == EXEC_DO || do_code->op == EXEC_DO_CONCURRENT);
+      if (do_code->op == EXEC_DO_CONCURRENT)
+	{
+	  gfc_error ("!$ACC LOOP cannot be a DO CONCURRENT loop at %L",
+		     &do_code->loc);
+	  break;
+	}
+      gcc_assert (do_code->op == EXEC_DO);
       if (do_code->ext.iterator->var->ts.type != BT_INTEGER)
 	gfc_error ("!$ACC LOOP iteration variable must be of type integer at %L",
 		   &do_code->loc);

gcc/testsuite/ChangeLog

+2019-02-14  Cesar Philippidis  <cesar@codesourcery.com>
+
+	PR fortran/72715
+	* gfortran.dg/goacc/loop-3-2.f95: Error on do concurrent loops.
+	* gfortran.dg/goacc/loop-3.f95: Likewise.
+	* gfortran.dg/goacc/pr72715.f90: New test.
+
 2019-02-14  Martin Liska  <mliska@suse.cz>
 
 	PR rtl-optimization/89242

gcc/testsuite/gfortran.dg/goacc/loop-3-2.f95

@@ -27,9 +27,9 @@ subroutine test1
   !$acc end parallel
   !$acc end loop ! { dg-error "Unexpected" }
 
-  ! OpenACC supports Fortran 2008 do concurrent statement
+  ! OpenACC does not support Fortran 2008 do concurrent statement
   !$acc loop
-  do concurrent (i = 1:5)
+  do concurrent (i = 1:5) ! { dg-error "ACC LOOP cannot be a DO CONCURRENT loop" }
   end do
 
   !$acc loop

gcc/testsuite/gfortran.dg/goacc/loop-3.f95

@@ -24,9 +24,9 @@ subroutine test1
   !$acc end parallel
   !$acc end loop ! { dg-error "Unexpected" }
 
-  ! OpenACC supports Fortran 2008 do concurrent statement
+  ! OpenACC does not support Fortran 2008 do concurrent statement
   !$acc loop
-  do concurrent (i = 1:5)
+  do concurrent (i = 1:5) ! { dg-error "ACC LOOP cannot be a DO CONCURRENT loop" }
   end do
 
   !$acc loop

gcc/testsuite/gfortran.dg/goacc/pr72715.f90

+program p
+  integer :: i
+  !$acc loop
+  do concurrent (i=1:3) ! { dg-error "ACC LOOP cannot be a DO CONCURRENT loop" }
+  end do
+end program p