Re: [PATCH] Fix undefined label problem after crossjumping (PR rtl-optimization/64536)

[Jakub Jelinek <jakub at redhat dot com>]

On Fri, Jan 09, 2015 at 11:59:44AM +0100, Richard Biener wrote:
> > If you want, I can try instead of disabling it for tablejumps
> > just move the label.
> 
> Yeah, I'd prefer that - it can't be too difficult, no?

So like this (tested just on the testcase, fully bootstrap/regtest
will follow)?

> > Still, I think we should be able to optimize it somewhere else too
> > (we can remove the tablejumps not just if all jump_table_data entries
> > point to next_bb, but even when they point to some completely different bb,
> > as long as it is a single_succ_p).  And ideally also optimize it at GIMPLE,
> > but guess that is GCC 6 material.
> 
> cfgcleanup material, similar for GIMPLE I guess.

You mean that cfgcleanup changes are GCC 6 material too?

2015-01-09  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/64536
	* cfgrtl.c (rtl_tidy_fallthru_edge): Handle removal of degenerate
	tablejumps.

	* gcc.dg/pr64536.c: New test.

--- gcc/cfgrtl.c.jj	2015-01-08 18:10:23.616598916 +0100
+++ gcc/cfgrtl.c	2015-01-09 14:47:26.637855477 +0100
@@ -1791,6 +1791,24 @@ rtl_tidy_fallthru_edge (edge e)
       && (any_uncondjump_p (q)
 	  || single_succ_p (b)))
     {
+      rtx label;
+      rtx_jump_table_data *table;
+
+      if (tablejump_p (q, &label, &table))
+	{
+	  /* The label is likely mentioned in some instruction before
+	     the tablejump and might not be DCEd, so turn it into
+	     a note instead and move before the tablejump that is going to
+	     be deleted.  */
+	  const char *name = LABEL_NAME (label);
+	  PUT_CODE (label, NOTE);
+	  NOTE_KIND (label) = NOTE_INSN_DELETED_LABEL;
+	  NOTE_DELETED_LABEL_NAME (label) = name;
+	  rtx_insn *lab = safe_as_a <rtx_insn *> (label);
+	  reorder_insns (lab, lab, PREV_INSN (q));
+	  delete_insn (table);
+	}
+
 #ifdef HAVE_cc0
       /* If this was a conditional jump, we need to also delete
 	 the insn that set cc0.  */
--- gcc/testsuite/gcc.dg/pr64536.c.jj	2015-01-09 13:55:53.035267213 +0100
+++ gcc/testsuite/gcc.dg/pr64536.c	2015-01-09 13:55:53.035267213 +0100
@@ -0,0 +1,67 @@
+/* PR rtl-optimization/64536 */
+/* { dg-do link } */
+/* { dg-options "-O2" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+
+struct S { long q; } *h;
+long a, b, g, j, k, *c, *d, *e, *f, *i;
+long *baz (void)
+{
+  asm volatile ("" : : : "memory");
+  return e;
+}
+
+void
+bar (int x)
+{
+  int y;
+  for (y = 0; y < x; y++)
+    {
+      switch (b)
+	{
+	case 0:
+	case 2:
+	  a++;
+	  break;
+	case 3:
+	  a++;
+	  break;
+	case 1:
+	  a++;
+	}
+      if (d)
+	{
+	  f = baz ();
+	  g = k++;
+	  if (&h->q)
+	    {
+	      j = *f;
+	      h->q = *f;
+	    }
+	  else
+	    i = (long *) (h->q = *f);
+	  *c++ = (long) f;
+	  e += 6;
+	}
+      else
+	{
+	  f = baz ();
+	  g = k++;
+	  if (&h->q)
+	    {
+	      j = *f;
+	      h->q = *f;
+	    }
+	  else
+	    i = (long *) (h->q = *f);
+	  *c++ = (long) f;
+	  e += 6;
+	}
+    }
+}
+
+int
+main ()
+{
+  return 0;
+}


	Jakub