tree.c (array_at_struct_end_p): Handle arrays at struct end with flexarrays more conservatively.

2017-05-04  Richard Biener  <rguenther@suse.de>

	* tree.c (array_at_struct_end_p): Handle arrays at struct
	end with flexarrays more conservatively.  Refactor and treat
	arrays of arrays or aggregates more strict.  Fix
	VIEW_CONVERT_EXPR handling.  Remove allow_compref argument.
	* tree.c (array_at_struct_end_p): Adjust prototype.
	* emit-rtl.c (set_mem_attributes_minus_bitpos): Adjust.
	* gimple-fold.c (get_range_strlen): Likewise.
	* tree-chkp.c (chkp_may_narrow_to_field): Likewise.

From-SVN: r247581

1 files changed, 47 insertions, 16 deletions

diff --git a/gcc/tree.c b/gcc/tree.c
index d88c445..3bc6f1c 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -13221,18 +13221,26 @@ array_ref_up_bound (tree exp)
   return NULL_TREE;
 }
 
-/* Returns true if REF is an array reference to an array at the end of
-   a structure.  If this is the case, the array may be allocated larger
-   than its upper bound implies.  When ALLOW_COMPREF is true considers
-   REF when it's a COMPONENT_REF in addition ARRAY_REF and
-   ARRAY_RANGE_REF.  */
+/* Returns true if REF is an array reference or a component reference
+   to an array at the end of a structure.
+   If this is the case, the array may be allocated larger
+   than its upper bound implies.  */
 
 bool
-array_at_struct_end_p (tree ref, bool allow_compref)
+array_at_struct_end_p (tree ref)
 {
-  if (TREE_CODE (ref) != ARRAY_REF
-      && TREE_CODE (ref) != ARRAY_RANGE_REF
-      && (!allow_compref || TREE_CODE (ref) != COMPONENT_REF))
+  tree atype;
+
+  if (TREE_CODE (ref) == ARRAY_REF
+      || TREE_CODE (ref) == ARRAY_RANGE_REF)
+    {
+      atype = TREE_TYPE (TREE_OPERAND (ref, 0));
+      ref = TREE_OPERAND (ref, 0);
+    }
+  else if (TREE_CODE (ref) == COMPONENT_REF
+	   && TREE_CODE (TREE_TYPE (TREE_OPERAND (ref, 1))) == ARRAY_TYPE)
+    atype = TREE_TYPE (TREE_OPERAND (ref, 1));
+  else
     return false;
 
   while (handled_component_p (ref))
@@ -13240,19 +13248,42 @@ array_at_struct_end_p (tree ref, bool allow_compref)
       /* If the reference chain contains a component reference to a
          non-union type and there follows another field the reference
 	 is not at the end of a structure.  */
-      if (TREE_CODE (ref) == COMPONENT_REF
-	  && TREE_CODE (TREE_TYPE (TREE_OPERAND (ref, 0))) == RECORD_TYPE)
+      if (TREE_CODE (ref) == COMPONENT_REF)
 	{
-	  tree nextf = DECL_CHAIN (TREE_OPERAND (ref, 1));
-	  while (nextf && TREE_CODE (nextf) != FIELD_DECL)
-	    nextf = DECL_CHAIN (nextf);
-	  if (nextf)
-	    return false;
+	  if (TREE_CODE (TREE_TYPE (TREE_OPERAND (ref, 0))) == RECORD_TYPE)
+	    {
+	      tree nextf = DECL_CHAIN (TREE_OPERAND (ref, 1));
+	      while (nextf && TREE_CODE (nextf) != FIELD_DECL)
+		nextf = DECL_CHAIN (nextf);
+	      if (nextf)
+		return false;
+	    }
 	}
+      /* If we have a multi-dimensional array we do not consider
+         a non-innermost dimension as flex array if the whole
+	 multi-dimensional array is at struct end.
+	 Same for an array of aggregates with a trailing array
+	 member.  */
+      else if (TREE_CODE (ref) == ARRAY_REF)
+	return false;
+      else if (TREE_CODE (ref) == ARRAY_RANGE_REF)
+	;
+      /* If we view an underlying object as sth else then what we
+         gathered up to now is what we have to rely on.  */
+      else if (TREE_CODE (ref) == VIEW_CONVERT_EXPR)
+	break;
+      else
+	gcc_unreachable ();
 
       ref = TREE_OPERAND (ref, 0);
     }
 
+  /* The array now is at struct end.  Treat flexible arrays as
+     always subject to extend, even into just padding constrained by
+     an underlying decl.  */
+  if (! TYPE_SIZE (atype))
+    return true;
+
   tree size = NULL;
 
   if (TREE_CODE (ref) == MEM_REF