re PR tree-optimization/90213 (UBSAN: signed integer overflow:…

re PR tree-optimization/90213 (UBSAN: signed integer overflow: -5621332293356458048 * 8 cannot be represented in type 'long int')

2019-04-24  Richard Biener  <rguenther@suse.de>

	PR middle-end/90213
	* gimple-fold.c (fold_const_aggregate_ref_1): Do multiplication
	by size and BITS_PER_UNIT on poly-wide-ints.

From-SVN: r270570

gcc/ChangeLog

+2019-04-24  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/90213
+	* gimple-fold.c (fold_const_aggregate_ref_1): Do multiplication
+	by size and BITS_PER_UNIT on poly-wide-ints.
+
 2019-04-25  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/90194

gcc/gimple-fold.c

@@ -6983,14 +6983,10 @@ fold_const_aggregate_ref_1 (tree t, tree (*valueize) (tree))
 		= wi::sext (wi::to_poly_offset (idx)
 			    - wi::to_poly_offset (low_bound),
 			    TYPE_PRECISION (TREE_TYPE (idx)));
-
+	      woffset *= tree_to_uhwi (unit_size);
+	      woffset *= BITS_PER_UNIT;
 	      if (woffset.to_shwi (&offset))
 		{
-		  /* TODO: This code seems wrong, multiply then check
-		     to see if it fits.  */
-		  offset *= tree_to_uhwi (unit_size);
-		  offset *= BITS_PER_UNIT;
-
 		  base = TREE_OPERAND (t, 0);
 		  ctor = get_base_constructor (base, &offset, valueize);
 		  /* Empty constructor.  Always fold to 0.  */