re PR tree-optimization/87826 (ubsan: gimple-ssa-store-merging.c:281)

	PR tree-optimization/87826
	* gimple-ssa-store-merging.c (do_shift_rotate): Punt if count is
	negative or larger or equal to type's precision.

	* gcc.dg/pr87826.c: New test.

From-SVN: r265720

gcc/ChangeLog

+2018-11-01  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/87826
+	* gimple-ssa-store-merging.c (do_shift_rotate): Punt if count is
+	negative or larger or equal to type's precision.
+
 2018-10-31  Alexandre Oliva <aoliva@redhat.com>
 
 	* opts.c (default_options_table): Do not enable

gcc/gimple-ssa-store-merging.c

@@ -262,7 +262,9 @@ do_shift_rotate (enum tree_code code,
   int i, size = TYPE_PRECISION (n->type) / BITS_PER_UNIT;
   unsigned head_marker;
 
-  if (count % BITS_PER_UNIT != 0)
+  if (count < 0
+      || count >= TYPE_PRECISION (n->type)
+      || count % BITS_PER_UNIT != 0)
     return false;
   count = (count / BITS_PER_UNIT) * BITS_PER_MARKER;
 

gcc/testsuite/ChangeLog

+2018-11-01  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/87826
+	* gcc.dg/pr87826.c: New test.
+
 2018-11-01  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/46020

gcc/testsuite/gcc.dg/pr87826.c

+/* PR tree-optimization/87826 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -w" } */
+
+int c;
+
+void
+foo (int *b)
+{
+  int e;
+  for (e = 0; e < 16; ++e)
+    b[e] = c >> e * 8;
+}