Use safe_dyn_cast instead of dyn_cast in find_loop_guard to fix PR92608.

2019-11-22  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

	PR tree-optimization/92608
	* tree-ssa-loop-unswitch.c (find_loop_guard): Use safe_dyn_cast instead
	of dyn_cast.

testsuite/
	* gcc.dg/torture/pr92608.c: New test.

From-SVN: r278598

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2019-11-22  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
+
+	PR tree-optimization/92608
+	* tree-ssa-loop-unswitch.c (find_loop_guard): Use safe_dyn_cast instead
+	of dyn_cast.
+
 2019-11-21  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* config/rs6000/predicates.md (extra_insn_branch_comparison_operator):

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2019-11-22  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
+
+	PR tree-optimization/92608
+	* gcc.dg/torture/pr92608.c: New test.
+
 2019-11-21  Iain Sandoe  <iain@sandoe.co.uk>
 
 	PR testsuite/92619

gcc/testsuite/gcc.dg/torture/pr92608.c

@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-funswitch-loops" } */
+
+int op, bs;
+
+void
+q0 (void)
+{
+  op += 1 % (op == bs);
+}
+
+void __attribute__ ((returns_twice))
+co (void)
+{
+}
+
+void __attribute__ ((simd))
+uq (void)
+{
+  q0 ();
+  co ();
+
+  while (bs < 1)
+    ++bs;
+}

gcc/tree-ssa-loop-unswitch.c

@@ -586,7 +586,7 @@ find_loop_guard (class loop *loop)
 	next = single_succ (header);
       else
 	{
-	  cond = dyn_cast <gcond *> (last_stmt (header));
+	  cond = safe_dyn_cast <gcond *> (last_stmt (header));
 	  if (! cond)
 	    return NULL;
 	  extract_true_false_edges_from_block (header, &te, &fe);