It put semicolons.
I dont know gas very well and I did not think about it.
After a long time of weird behavior in which a file that was only
changed in its 'comments' was behaving different from one that was
not, I looked at the gas manual and find that semicolon is like in C
-- a statement separator.
Maybe you should try `gas-mode'
http://www.hczim.de/software/gas-mode.html
instead of asm-mode shipped with Emacs.
martin