Re: [SFN] Bootstrap broken

[Jakub Jelinek <jakub at redhat dot com>]

On Wed, Dec 13, 2017 at 10:28:22AM +0100, Jakub Jelinek wrote:
> Formatting, this should be
>   bool can_move_early_debug_stmts
>     = ...
> and the line is too long, so needs to be wrapped.
> 
> Furthermore, I must say I don't understand why
> can_move_early_debug_stmts should care whether there are any labels in
> dest bb or not.  That sounds very risky for introducing non-# DEBUG BEGIN_STMT
> debug insns before labels if it could happen.  Though, if
> gsi_stmt (gsi) == gsi_stmt (gsie), then the loop right below it will not
> do anything and nothing cares about can_move_early_debug_stmts afterwards.
> So, in short, can_move_early_debug_stmts is used only if
> gsi_stmt (gsi) != gsi_stmt (gsie), and therefore
> can_move_early_debug_stmts if it is used is can_move_debug_stmts && (1 || ...);
> 
> So, can we get rid of can_move_early_debug_stmts altogether and just use
> can_move_debug_stmts in there instead?
> 
> Another thing I find risky is that you compute gsie_to so early and don't
> update it.  If you don't need it above for can_move_early_debug_stmts, can
> you just do it back where it used to be done,

Here it is everything in patch form, in case some volunteers are willing to
test it on their targets, because we need faster turn-arounds for this.

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.

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

--- gcc/tree-cfgcleanup.c.jj	2017-12-12 09:48:26.813393301 +0100
+++ gcc/tree-cfgcleanup.c	2017-12-13 11:39:03.373065381 +0100
@@ -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.  */
--- gcc/testsuite/g++.dg/torture/pr83391.C.jj
+++ gcc/testsuite/g++.dg/torture/pr83391.C
@@ -0,0 +1,36 @@
+// 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.jj
+++ gcc/testsuite/gcc.dg/torture/pr83396.c
@@ -0,0 +1,38 @@
+/* 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, "");
+    }
+}


	Jakub