On Fri, Dec 09, 2011 at 10:35:57AM +0100, Richard Guenther wrote:
> > *shrug* Maybe just a new pass immediately before ehcleanup2?
> > It's just a quick pass over the basic blocks...
> 
> I'd just not care for the ones preceeding a return.  Not at this point
> at least.
After IRC discussion with richi I've committed the following:

2011-12-09  Jakub Jelinek  <ja...@redhat.com>
            Andrew Pinski  <apin...@cavium.com>

        PR tree-optimization/51117
        * tree-eh.c (optimize_clobbers): New function.
        (execute_lower_eh_dispatch): Call it.

--- gcc/tree-eh.c.jj    2011-12-01 11:45:06.000000000 +0100
+++ gcc/tree-eh.c       2011-12-08 17:48:58.009908793 +0100
@@ -3173,6 +3173,30 @@ struct gimple_opt_pass pass_lower_resx =
  }
 };
 
+/* Try to optimize var = {v} {CLOBBER} stmts followed just by
+   external throw.  */
+
+static void
+optimize_clobbers (basic_block bb)
+{
+  gimple_stmt_iterator gsi = gsi_last_bb (bb);
+  for (gsi_prev (&gsi); !gsi_end_p (gsi);)
+    {
+      gimple stmt = gsi_stmt (gsi);
+      if (is_gimple_debug (stmt))
+       {
+         gsi_prev (&gsi);
+         continue;
+       }
+      if (!gimple_assign_single_p (stmt)
+         || TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME
+         || !TREE_CLOBBER_P (gimple_assign_rhs1 (stmt)))
+       return;
+      unlink_stmt_vdef (stmt);
+      gsi_remove (&gsi, true);
+      release_defs (stmt);
+    }
+}
 
 /* At the end of inlining, we can lower EH_DISPATCH.  Return true when 
    we have found some duplicate labels and removed some edges.  */
@@ -3337,11 +3361,16 @@ execute_lower_eh_dispatch (void)
   FOR_EACH_BB (bb)
     {
       gimple last = last_stmt (bb);
-      if (last && gimple_code (last) == GIMPLE_EH_DISPATCH)
+      if (last == NULL)
+       continue;
+      if (gimple_code (last) == GIMPLE_EH_DISPATCH)
        {
          redirected |= lower_eh_dispatch (bb, last);
          any_rewritten = true;
        }
+      else if (gimple_code (last) == GIMPLE_RESX
+              && stmt_can_throw_external (last))
+       optimize_clobbers (bb);
     }
 
   if (redirected)


        Jakub

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