[tree-ssa-address] Avoid creating non-canonical RTL in gen_addr_rtx

	* tree-ssa-address.c (gen_addr_rtx): Don't handle index if it
	is const0_rtx.

	* gcc.dg/20161219.c: New test.

From-SVN: r244219

gcc/ChangeLog

+2017-01-09  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	* tree-ssa-address.c (gen_addr_rtx): Don't handle index if it
+	is const0_rtx.
+
 2017-01-09  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/78997

gcc/testsuite/ChangeLog

+2017-01-09  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	* gcc.dg/20161219.c: New test.
+
 2017-01-09  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/78997

gcc/testsuite/gcc.dg/20161219.c

+/* { dg-do assemble } */
+/* { dg-options "-O1 -w" } */
+
+static long long a[9];
+int b, c, d, e, g;
+
+static int
+fn1 (int *p1)
+{
+  b = 1;
+  for (; b >= 0; b--)
+    {
+      d = 0;
+      for (;; d++)
+	{
+	  e && (a[d] = 0);
+	  if (*p1)
+	    break;
+	  c = (int) a;
+	}
+    }
+  return 0;
+}
+
+int
+main ()
+{
+  int f = fn1 ((int *) f);
+  return f;
+}

gcc/tree-ssa-address.c

@@ -115,7 +115,7 @@ gen_addr_rtx (machine_mode address_mode,
   if (offset_p)
     *offset_p = NULL;
 
-  if (index)
+  if (index && index != const0_rtx)
     {
       act_elem = index;
       if (step)