re PR bootstrap/83396 (Bootstrap failures with Statement Frontiers)

	PR bootstrap/83396
	PR debug/83391
	* tree-cfgcleanup.c (remove_forwarder_block): Keep after
	labels debug stmts that can only appear after labels.

	* gcc.dg/torture/pr83396.c: New test.
	* g++.dg/torture/pr83391.C: New test.

Co-Authored-By: Jakub Jelinek <jakub@redhat.com>

From-SVN: r255609

gcc/ChangeLog

+2017-12-13  Alexandre Oliva <aoliva@redhat.com>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR bootstrap/83396
+	PR debug/83391
+	* tree-cfgcleanup.c (remove_forwarder_block): Keep after
+	labels debug stmts that can only appear after labels.
+
 2017-12-13  Alexander Monakov  <amonakov@ispras.ru>
 
 	PR rtl-optimization/82398

gcc/testsuite/ChangeLog

+2017-12-13  Alexandre Oliva <aoliva@redhat.com>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR bootstrap/83396
+	PR debug/83391
+	* gcc.dg/torture/pr83396.c: New test.
+	* g++.dg/torture/pr83391.C: New test.
+
 2017-12-13  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	PR rtl-optimization/83393

gcc/testsuite/g++.dg/torture/pr83391.C

+// PR debug/83391
+// { dg-do compile }
+// { dg-options "-g" }
+// { dg-additional-options "-mbranch-cost=1" { target { i?86-*-* x86_64-*-* mips*-*-* s390*-*-* avr*-*-* } } }
+
+unsigned char a;
+enum E { F, G, H } b;
+int c, d;
+
+void
+foo ()
+{
+  int e;
+  bool f;
+  E g = b;
+  while (1)
+    {
+      unsigned char h = a ? d : 0;
+      switch (g)
+	{
+	case 0:
+	  f = h <= 'Z' || h >= 'a' && h <= 'z';
+	  break;
+	case 1:
+	  {
+	    unsigned char i = h;
+	    e = 0;
+	  }
+	  if (e || h)
+	    g = H;
+	  /* FALLTHRU */
+	default:
+	  c = 0;
+	}
+    }
+}

gcc/testsuite/gcc.dg/torture/pr83396.c

+/* PR bootstrap/83396 */
+/* { dg-do compile } */
+/* { dg-options "-g" } */
+
+int fn1 (void);
+void fn2 (void *, const char *);
+void fn3 (void);
+
+void
+fn4 (long long x)
+{
+  fn3 ();
+}
+
+void
+fn5 (long long x)
+{
+  if (x)
+    fn3();
+}
+
+void
+fn6 (long long x)
+{
+  switch (fn1 ())
+    {
+    case 0:
+      fn5 (x);
+    case 2:
+      fn2 (0, "");
+      break;
+    case 1:
+    case 3:
+      fn4(x);
+    case 5:
+      fn2 (0, "");
+    }
+}

gcc/tree-cfgcleanup.c

@@ -536,9 +536,14 @@ remove_forwarder_block (basic_block bb)
      defined labels and labels with an EH landing pad number to the
      new block, so that the redirection of the abnormal edges works,
      jump targets end up in a sane place and debug information for
-     labels is retained.  */
+     labels is retained.
+
+     While at that, move any debug stmts that appear before or in between
+     labels, but not those that can only appear after labels.  */
   gsi_to = gsi_start_bb (dest);
-  for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
+  gsi = gsi_start_bb (bb);
+  gimple_stmt_iterator gsie = gsi_after_labels (bb);
+  while (gsi_stmt (gsi) != gsi_stmt (gsie))
     {
       tree decl;
       label = gsi_stmt (gsi);
@@ -557,6 +562,21 @@ remove_forwarder_block (basic_block bb)
 	gsi_next (&gsi);
     }
 
+  /* Move debug statements if the destination has a single predecessor.  */
+  if (can_move_debug_stmts && !gsi_end_p (gsi))
+    {
+      gcc_assert (gsi_stmt (gsi) == gsi_stmt (gsie));
+      gimple_stmt_iterator gsie_to = gsi_after_labels (dest);
+      do
+	{
+	  gimple *debug = gsi_stmt (gsi);
+	  gcc_assert (is_gimple_debug (debug));
+	  gsi_remove (&gsi, false);
+	  gsi_insert_before (&gsie_to, debug, GSI_SAME_STMT);
+	}
+      while (!gsi_end_p (gsi));
+    }
+
   bitmap_set_bit (cfgcleanup_altered_bbs, dest->index);
 
   /* Update the dominators.  */