re PR tree-optimization/83044 (ice in contains_struct_check)

	PR tree-optimization/83044
	* tree-vrp.c (vrp_prop::check_array_ref): If eltsize is not
	INTEGER_CST or is 0, clear up_bound{,_p1} and later ignore tests
	that need the upper bound.  Subtract offset from
	get_addr_base_and_unit_offset only if positive and subtract it
	before division by eltsize rather than after it.

	* gcc.dg/pr83044.c: New test.
	* c-c++-common/Warray-bounds.c (fb): Fix up MAX value.

From-SVN: r255054

gcc/ChangeLog

 2017-11-22  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/83044
+	* tree-vrp.c (vrp_prop::check_array_ref): If eltsize is not
+	INTEGER_CST or is 0, clear up_bound{,_p1} and later ignore tests
+	that need the upper bound.  Subtract offset from
+	get_addr_base_and_unit_offset only if positive and subtract it
+	before division by eltsize rather than after it.
+
 	PR debug/83084
 	* valtrack.c (propagate_for_debug_subst, propagate_for_debug): Reset
 	debug insns if they would contain UNSPEC_VOLATILE or volatile asm.

gcc/testsuite/ChangeLog

+2017-11-22  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/83044
+	* gcc.dg/pr83044.c: New test.
+	* c-c++-common/Warray-bounds.c (fb): Fix up MAX value.
+
 2017-11-22  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/79072

gcc/testsuite/c-c++-common/Warray-bounds.c

@@ -200,7 +200,7 @@ void fb (struct B *p)
 
   T (p->a1x[9].a1[0]);
 
-  enum { MAX = DIFF_MAX / sizeof *p->a1x - sizeof *p };
+  enum { MAX = (DIFF_MAX - sizeof *p) / sizeof *p->a1x };
 
   T (p->a1x[DIFF_MIN].a1);                /* { dg-warning "array subscript -\[0-9\]+ is below array bounds" } */
   T (p->a1x[-1].a1);                      /* { dg-warning "array subscript -1 is below array bounds" } */

gcc/testsuite/gcc.dg/pr83044.c

+/* PR tree-optimization/83044 */
+/* { dg-do compile } */
+/* { dg-options "-Wall -std=gnu89 -O2" } */
+
+struct A { int b[0]; };
+struct B { struct A c[0]; };
+void bar (int *);
+
+void
+foo (void)
+{
+  struct B d;
+  bar (d.c->b);
+}

gcc/tree-vrp.c

@@ -4795,24 +4795,30 @@ vrp_prop::check_array_ref (location_t location, tree ref,
 	 the size of the largest object is PTRDIFF_MAX.  */
       tree eltsize = array_ref_element_size (ref);
 
-      /* FIXME: Handle VLAs.  */
-      if (TREE_CODE (eltsize) != INTEGER_CST)
-	return;
-
-      tree maxbound = TYPE_MAX_VALUE (ptrdiff_type_node);
-
-      up_bound_p1 = int_const_binop (TRUNC_DIV_EXPR, maxbound, eltsize);
-
-      tree arg = TREE_OPERAND (ref, 0);
+      if (TREE_CODE (eltsize) != INTEGER_CST
+	  || integer_zerop (eltsize))
+	{
+	  up_bound = NULL_TREE;
+	  up_bound_p1 = NULL_TREE;
+	}
+      else
+	{
+	  tree maxbound = TYPE_MAX_VALUE (ptrdiff_type_node);
+	  tree arg = TREE_OPERAND (ref, 0);
+	  HOST_WIDE_INT off;
+
+	  if (get_addr_base_and_unit_offset (arg, &off) && off > 0)
+	    maxbound = wide_int_to_tree (sizetype,
+					 wi::sub (wi::to_wide (maxbound),
+						  off));
+	  else
+	    maxbound = fold_convert (sizetype, maxbound);
 
-      HOST_WIDE_INT off;
-      if (get_addr_base_and_unit_offset (arg, &off))
-	up_bound_p1 = wide_int_to_tree (sizetype,
-					wi::sub (wi::to_wide (up_bound_p1),
-						 off));
+	  up_bound_p1 = int_const_binop (TRUNC_DIV_EXPR, maxbound, eltsize);
 
-      up_bound = int_const_binop (MINUS_EXPR, up_bound_p1,
-				  build_int_cst (ptrdiff_type_node, 1));
+	  up_bound = int_const_binop (MINUS_EXPR, up_bound_p1,
+				      build_int_cst (ptrdiff_type_node, 1));
+	}
     }
   else
     up_bound_p1 = int_const_binop (PLUS_EXPR, up_bound,
@@ -4823,7 +4829,7 @@ vrp_prop::check_array_ref (location_t location, tree ref,
   tree artype = TREE_TYPE (TREE_OPERAND (ref, 0));
 
   /* Empty array.  */
-  if (tree_int_cst_equal (low_bound, up_bound_p1))
+  if (up_bound && tree_int_cst_equal (low_bound, up_bound_p1))
     {
       warning_at (location, OPT_Warray_bounds,
 		  "array subscript %E is above array bounds of %qT",
@@ -4843,7 +4849,8 @@ vrp_prop::check_array_ref (location_t location, tree ref,
 
   if (vr && vr->type == VR_ANTI_RANGE)
     {
-      if (TREE_CODE (up_sub) == INTEGER_CST
+      if (up_bound
+	  && TREE_CODE (up_sub) == INTEGER_CST
           && (ignore_off_by_one
 	      ? tree_int_cst_lt (up_bound, up_sub)
 	      : tree_int_cst_le (up_bound, up_sub))
@@ -4856,7 +4863,8 @@ vrp_prop::check_array_ref (location_t location, tree ref,
           TREE_NO_WARNING (ref) = 1;
         }
     }
-  else if (TREE_CODE (up_sub) == INTEGER_CST
+  else if (up_bound
+	   && TREE_CODE (up_sub) == INTEGER_CST
 	   && (ignore_off_by_one
 	       ? !tree_int_cst_le (up_sub, up_bound_p1)
 	       : !tree_int_cst_le (up_sub, up_bound)))