Replace flag_strict_flex_arrays with DECL_NOT_FLEXARRAY in middle-end.

We should not directly check flag_strict_flex_arrays in the
middle end. Instead, check DECL_NOT_FLEXARRAY(array_field_decl) which is set
by C/C++ FEs according to -fstrict-flex-arrays and the corresponding
attribute attached to the array_field.

As a result, We will lose the LEVEL information of -fstrict-flex-arrays in
the middle end. -Wstrict-flex-arrays will not be able to issue such
information. update the testing cases accordingly.

gcc/ChangeLog:

	* attribs.cc (strict_flex_array_level_of): Move this function to ...
	* attribs.h (strict_flex_array_level_of): Remove the declaration.
	* gimple-array-bounds.cc (array_bounds_checker::check_array_ref):
	replace the referece to strict_flex_array_level_of with
	DECL_NOT_FLEXARRAY.
	* tree.cc (component_ref_size): Likewise.

gcc/c/ChangeLog:

	* c-decl.cc (strict_flex_array_level_of): ... here.

gcc/testsuite/ChangeLog:

	* gcc.dg/Warray-bounds-flex-arrays-1.c: Delete the level information
	from the message issued by -Wstrict-flex-arrays.
	* gcc.dg/Warray-bounds-flex-arrays-2.c: Likewise.
	* gcc.dg/Warray-bounds-flex-arrays-3.c: Likewise.
	* gcc.dg/Warray-bounds-flex-arrays-4.c: Likewise.
	* gcc.dg/Warray-bounds-flex-arrays-5.c: Likewise.
	* gcc.dg/Warray-bounds-flex-arrays-6.c: Likewise.
	* gcc.dg/Wstrict-flex-arrays-2.c: Likewise.
	* gcc.dg/Wstrict-flex-arrays-3.c: Likewise.
	* gcc.dg/Wstrict-flex-arrays.c: Likewise.

1 files changed, 9 insertions, 37 deletions

diff --git a/gcc/gimple-array-bounds.cc b/gcc/gimple-array-bounds.cc
index 116200a..66fd46e 100644
--- a/gcc/gimple-array-bounds.cc
+++ b/gcc/gimple-array-bounds.cc
@@ -350,18 +350,14 @@ array_bounds_checker::check_array_ref (location_t location, tree ref,
 
   /* Set to the type of the special array member for a COMPONENT_REF.  */
   special_array_member sam{ };
-
+  tree afield_decl = NULL_TREE;
   tree arg = TREE_OPERAND (ref, 0);
-  const bool compref = TREE_CODE (arg) == COMPONENT_REF;
-  unsigned int strict_flex_array_level = flag_strict_flex_arrays;
 
-  if (compref)
+  if (TREE_CODE (arg) == COMPONENT_REF)
     {
       /* Try to determine special array member type for this COMPONENT_REF.  */
       sam = component_ref_sam_type (arg);
-      /* Get the level of strict_flex_array for this array field.  */
-      tree afield_decl = TREE_OPERAND (arg, 1);
-      strict_flex_array_level = strict_flex_array_level_of (afield_decl);
+      afield_decl = TREE_OPERAND (arg, 1);
     }
 
   get_up_bounds_for_array_ref (ref, &decl, &up_bound, &up_bound_p1);
@@ -412,39 +408,15 @@ array_bounds_checker::check_array_ref (location_t location, tree ref,
 
       /* issue warnings for -Wstrict-flex-arrays according to the level of
 	 flag_strict_flex_arrays.  */
-      if (out_of_bound && warn_strict_flex_arrays)
-      switch (strict_flex_array_level)
-	{
-	  case 3:
-	    /* Issue additional warnings for trailing arrays [0].  */
-	    if (sam == special_array_member::trail_0)
+      if ((out_of_bound && warn_strict_flex_arrays)
+	  && (((sam == special_array_member::trail_0)
+		|| (sam == special_array_member::trail_1)
+		|| (sam == special_array_member::trail_n))
+	      && DECL_NOT_FLEXARRAY (afield_decl)))
 	      warned = warning_at (location, OPT_Wstrict_flex_arrays,
 				   "trailing array %qT should not be used as "
-				   "a flexible array member for level 3",
+				   "a flexible array member",
 				   artype);
-	    /* FALLTHROUGH.  */
-	  case 2:
-	    /* Issue additional warnings for trailing arrays [1].  */
-	    if (sam == special_array_member::trail_1)
-	      warned = warning_at (location, OPT_Wstrict_flex_arrays,
-				   "trailing array %qT should not be used as "
-				   "a flexible array member for level 2 and "
-				   "above", artype);
-	    /* FALLTHROUGH.  */
-	  case 1:
-	    /* Issue warnings for trailing arrays [n].  */
-	    if (sam == special_array_member::trail_n)
-	      warned = warning_at (location, OPT_Wstrict_flex_arrays,
-				   "trailing array %qT should not be used as "
-				   "a flexible array member for level 1 and "
-				   "above", artype);
-	    break;
-	  case 0:
-	    /* Do nothing.  */
-	    break;
-	  default:
-	    gcc_unreachable ();
-	}
 
       /* Avoid more warnings when checking more significant subscripts
 	 of the same expression.  */