Improve partitioning decisions

[Jan Hubicka]

> 
> FAIL: gcc.dg/lto/20081204-2 c_lto_20081204-2_0.o-c_lto_20081204-2_0.o
> link, -w -flto -fPIC -r -nostdlib (internal compiler error)
> FAIL: gcc.dg/lto/20090914-2 c_lto_20090914-2_0.o-c_lto_20090914-2_0.o
> link, -O2 -flto -fuse-linker-plugin (internal compiler error)
> FAIL: gcc.dg/lto/20091014-1 c_lto_20091014-1_0.o-c_lto_20091014-1_0.o
> link, -fPIC -r -nostdlib -flto (internal compiler error)
> FAIL: gcc.dg/lto/20100603-1 c_lto_20100603-1_0.o-c_lto_20100603-1_0.o
> link, -O0 -flto -fuse-linker-plugin -fno-fat-lto-objects  (internal
> compiler error)
> FAIL: gcc.dg/lto/20100603-1 c_lto_20100603-1_0.o-c_lto_20100603-1_0.o
> link, -O2 -flto -fuse-linker-plugin (internal compiler error)
> FAIL: g++.dg/lto/20081120-1
> cp_lto_20081120-1_0.o-cp_lto_20081120-1_1.o link, -flto -r -nostdlib
> (internal compiler error)
> FAIL: g++.dg/lto/20081120-2
> cp_lto_20081120-2_0.o-cp_lto_20081120-2_1.o link, -flto -r -nostdlib
> (internal compiler error)

Sorry, that was last minute fix into the sanity check.  Curiously enough
the check incorrectly triggers for empty file. It is interesting we test
it so many times.

I am testing.

Index: lto-partition.c
===================================================================
--- lto-partition.c	(revision 259755)
+++ lto-partition.c	(working copy)
@@ -809,7 +809,7 @@
     next_nodes.safe_push (noreorder[noreorder_pos++]);
   /* For one partition the cost of boundary should be 0 unless we added final
      symbols here (these are not accounted) or we have accounting bug.  */
-  gcc_assert (next_nodes.length () || npartitions != 1 || !best_cost);
+  gcc_assert (next_nodes.length () || npartitions != 1 || !best_cost || best_cost == -1);
   add_sorted_nodes (next_nodes, partition);
 
   free (order);