[Bug c/48197] possible wrong code bug at -O0

[regehr at cs dot utah.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48197

--- Comment #6 from John Regehr <regehr at cs dot utah.edu> 2011-03-18 20:23:32 
UTC ---
Bleh... nevermind the longer test, it carries along my misunderstanding of the
sign extension.  Anyway, thanks!