[Bug rtl-optimization/50891] move2add_note_store fails to properly track register content

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50891

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> 2011-10-28 21:20:09 
UTC ---
We have

(set (reg:DI 2) (mem))
...
(set (reg:HI 2) (const_int))
...
(set (reg:SI 2) (const_int))

Since we don't if know

(set (reg:HI 2) (const_int))

will update the whole register, move2add_note_store should
stop if the new mode is narrower than the previous mode.