[Bug c++/56742] Optimization bug lead to uncaught throw

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56742

--- Comment #4 from Kai Tietz <ktietz at gcc dot gnu.org> 2013-03-27 09:40:16 UTC ---
(In reply to comment #3)
> (In reply to comment #2)
> > Hmm, yes indeed it is the -freorder-blocks option. One solution is to 
> > disallow after reload for SEH-target to modify jumps.
> 
> That's an awfully big hammer. Perhaps it's possible to first analyze
> what is actually happening in bbreorder that causes this bug?

Well, the issue is analyzed.  The issue is that SEH is table-based EH, and so
after bb-reorder used labels for describing eh-regions are getting invalid.
If you take a look to the produces assembly for the example, you will notice
that easily.
I admit that the first patch is a bit too invasive, as it disables bb-reorder
in all cases.  But in fact we need to disable it just if there is a
catch-region. A more improved variant is:

Index: i386.c
===================================================================
--- i386.c      (Revision 197118)
+++ i386.c      (Arbeitskopie)
@@ -3941,6 +3941,20 @@
   register_pass (&insert_vzeroupper_info);
 }

+/* Implement TARGET_CANNOT_MODIFY_JUMPS_P.  */
+static bool
+ix86_cannot_modify_jumps_p (void)
+{
+  if (TARGET_SEH && reload_completed
+      && cfun && cfun->eh
+      && cfun->eh->region_tree)
+    return true;
+  return false;
+}
+
+#undef  TARGET_CANNOT_MODIFY_JUMPS_P
+#define TARGET_CANNOT_MODIFY_JUMPS_P ix86_cannot_modify_jumps_p
+
 /* Update register usage after having seen the compiler flags.  */

 static void