[Bug debug/54177] [4.8 Regression]: Segfault in cselib_lookup due to NULL_RTX passed from vt_add_function_parameter

[aoliva at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54177

--- Comment #3 from Alexandre Oliva <aoliva at gcc dot gnu.org> 2012-08-07 
20:08:27 UTC ---
Having reviewed teh other uses of var_lowpart, I hereby approve the patch if it
passes regstrap.  Thanks!