Thanks for the response but I still didnt got the answer regarding whether it is possible to do loop unrolling without using -O1, -O2 or -O3. What exactly are those flags (along with funroll-all-loops) which makes loops unroll? Best regards Memon On Mon, Dec 13, 2010 at 2:46 AM, Kevin P. Fleming <kpfleming@xxxxxxxxxx> wrote: > On 12/12/2010 06:08 PM, Abdul Wahid Memon wrote: >> >> Hello everyone >> >> I have few questions regarding loop unrolling and the effect of flags >> (provided at command line) on the execution of passes. >> >> Is it possible to do loop unrolling without using -O3, -O2 and -O1? >> >> The -Q -O3 --help=optimizers options provides us the list of enabled >> and disabled optimizations at -O3 level. If I specify -O3 to compile >> any file then the total number of passes executed are around 182. And >> If I manually specify all the optimization which are enabled at -O3 >> (without specifying -O3 actually), we get the total number of passes >> as 64. So, my question is that why is there a difference of passes >> between these two cases? > > This question is asked on this list just about every month; the manual > documents the optimizer options that are controllable via flags at each > level, but there are many more optimization behaviors enabled at each level > which do not have individual controls. > > In other words, it is not possible to manually enable all optimizations that > would be enabled when using -O3; it is only possible to enable all of them > with -O3 and then disable any that you don't want enabled (which is why the > manual documents them). > > -- > Kevin P. Fleming > Digium, Inc. | Director of Software Technologies > 445 Jan Davis Drive NW - Huntsville, AL 35806 - USA > skype: kpfleming | jabber: kfleming@xxxxxxxxxx > Check us out at www.digium.com & www.asterisk.org >