Use clause locations in OpenACC nested reduction warnings

Since the Fortran front-end now sets the clause locations correctly, we can
emit warnings with more precise locations if we encounter conflicting
operations for a variable in reduction clauses.

2019-12-10  Frederik Harwath  <frederik@codesourcery.com>

gcc/
	* omp-low.c (scan_omp_for): Use clause location in warning.

From-SVN: r279168

gcc/ChangeLog

+2019-12-10  Frederik Harwath  <frederik@codesourcery.com>
+
+	* omp-low.c (scan_omp_for): Use clause location in warning.
+
 2019-12-10  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* dwarf2out.c (loc_descriptor): Punt for MODE_VECTOR_BOOL.

gcc/omp-low.c

@@ -2473,7 +2473,7 @@ scan_omp_for (gomp_for *stmt, omp_context *outer_ctx)
 	      tree_code outer_op = OMP_CLAUSE_REDUCTION_CODE (outer_clause);
 	      if (outer_var == local_var && outer_op != local_op)
 		{
-		  warning_at (gimple_location (stmt), 0,
+		  warning_at (OMP_CLAUSE_LOCATION (local_clause), 0,
 			      "conflicting reduction operations for %qE",
 			      local_var);
 		  inform (OMP_CLAUSE_LOCATION (outer_clause),