[PATCH] Fix PRs middle-end/15014 and middle-end/16973, removing labels with their address taken

[Andrew Pinski <pinskia@physics.uc.edu>]

The problem here is that we were getting rid of some bb as they were 
being marked as unreachable (which is true in the code flow sense) but 
should not
be removed.  I fixed this by adding an edge from the first bb to the 
label's
bb which has its address taken.  I think this is most correct solution 
as
this does not happen much we should not have to worry about losing some
optimization possibility from doing it this way.

OK? Bootstrapped and tested on powerpc-apple-darwin.

Thanks,
Andrew Pinski


Testcase:
void
f (void)
{
   static __SIZE_TYPE__ u = &&a-&&b;
   a : b :  return;
}


ChangeLog:
	* tre-cfg.c (make_edges): After making the edges but before
	cleaning up the cfg, make an edge from the first BB to ever
	BB which we take the address of the label.

Patch:
Index: tree-cfg.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-cfg.c,v
retrieving revision 2.64
diff -u -p -r2.64 tree-cfg.c
--- tree-cfg.c	2 Oct 2004 12:47:10 -0000	2.64
+++ tree-cfg.c	4 Oct 2004 14:44:19 -0000
@@ -417,6 +417,7 @@ static void
  make_edges (void)
  {
    basic_block bb;
+  basic_block target_bb;

    /* Create an edge from entry to the first block with executable
       statements in it.  */
@@ -448,6 +449,30 @@ make_edges (void)
    /* We do not care about fake edges, so remove any that the CFG
       builder inserted for completeness.  */
    remove_fake_exit_edges ();
+
+  /* Look for the block starting with the destination label.  In the
+     case of a computed label, make an edge from the entry block to the
+     computed lablel.  */
+  FOR_EACH_BB (target_bb)
+    {
+      block_stmt_iterator bsi;
+
+      for (bsi = bsi_start (target_bb); !bsi_end_p (bsi); bsi_next 
(&bsi))
+	{
+	  tree target = bsi_stmt (bsi);
+
+	  if (TREE_CODE (target) != LABEL_EXPR)
+	    break;
+
+	  if (FORCED_LABEL (LABEL_EXPR_LABEL (target))
+	      || DECL_NONLOCAL (LABEL_EXPR_LABEL (target)))
+	    {
+	      make_edge (EDGE_SUCC (ENTRY_BLOCK_PTR, 0)->dest,
+	                 target_bb, EDGE_ABNORMAL);
+	      break;
+	    }
+	}
+    }

    /* Clean up the graph and warn for unreachable code.  */
    cleanup_tree_cfg ();