I download the src of llvm 2.8 and run ./autoconf/AutoRegen.sh
However there is a little difference between origin configure file and the generated one
$diff configure configure.bak
< --enable-optimized Compile with optimizations enabled (default is YES)
Probably not. The configure file for the release branch was probably edited instead of configure.ac and so a regen will overwrite the last edit to that file. This isn't going to be fixed on the release branch so if you do regen configure it will probably have some differences (we'll make sure it doesn't happen for 2.9). That said, if this is the only difference it looks like just a comment difference and so shouldn't affect anything.
To be safe you'll probably want to explicitly set --enable-optimized or --disable-optimized depending on what you want.
It looks more like the "configure --help" output than a comment.
That’s right. I got the message of executing “configure --help”.
2011/1/3 Frits van Bommel <firstname.lastname@example.org>
Yes, still largely qualifies as comment rather than functional difference.