re PR middle-end/81564 (ICE in group_case_labels_stmt())

gcc/
	PR middle-end/81564
	* tree-cfg.c (group_case_labels_stmt): Handle already deleted blocks.

gcc/testsuite/
	PR middle-end/81564
	* gcc.dg/pr81564.c: New test.

From-SVN: r250628

gcc/ChangeLog

+2017-07-27  Peter Bergner  <bergner@vnet.ibm.com>
+
+	PR middle-end/81564
+	* tree-cfg.c (group_case_labels_stmt): Handle already deleted blocks.
+
 2017-07-27  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/81573

gcc/testsuite/ChangeLog

+2017-07-27  Peter Bergner  <bergner@vnet.ibm.com>
+
+	PR middle-end/81564
+	* gcc.dg/pr81564.c: New test.
+
 2017-07-27  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/81573

gcc/testsuite/gcc.dg/pr81564.c

+/* PR middle-end/81564 ICE in group_case_labels_stmt().  */
+/* { dg-do compile }  */
+/* { dg-options "-O2" }  */
+
+struct a {
+    int b;
+    int c;
+};
+
+void
+foo (void)
+{
+  struct a *e;
+  switch (e->c)
+  {
+    case 7:
+    case 3:
+      if (__builtin_expect(!0, 0))
+	__builtin_unreachable();
+  }
+}

gcc/tree-cfg.c

@@ -1701,8 +1701,9 @@ group_case_labels_stmt (gswitch *stmt)
       gcc_assert (base_case);
       base_bb = label_to_block (CASE_LABEL (base_case));
 
-      /* Discard cases that have the same destination as the default case.  */
-      if (base_bb == default_bb)
+      /* Discard cases that have the same destination as the default case or
+	 whose destiniation blocks have already been removed as unreachable.  */
+      if (base_bb == NULL || base_bb == default_bb)
 	{
 	  i++;
 	  continue;