Andrzej Giniewicz wrote: > Hi - it's my first time on that list, I hope I choose good one as gcc > have really quite number of different mailing lists :) > > lately I hit very strange behaviour, i.e. the app I wanted to build > works when I build it with -O0 but crash at -O1, I wanted to eliminate > flags that work as I usually do, by doing -O0 and adding all flags > that are on -O1 and aren't on -O0, I got their list using standard > recommended by manual way: > > g++ -c -Q -O0 --help=optimize > 0.flags > g++ -c -Q -O1 --help=optimize > 1.flags > diff 0.flags 1.flags | grep enabled > > the problem is that I was able to add all flags returned by above > commands! Is there some secret things that -O1 do instead of only > lighting those -f*** flags listened by above commands? If above > returned me: > > -fcprop-registers -fdefer-pop -fguess-branch-probability > -fif-conversion -fif-conversion2 -fipa-pure-const -fipa-reference > -fmerge-constants -fomit-frame-pointer -fsplit-wide-types -ftree-ccp > -ftree-ch -ftree-copy-prop -ftree-copyrename -ftree-dce > -ftree-dominator-opts -ftree-dse -ftree-fre -ftree-salias -ftree-sink > -ftree-sra -ftree-ter -funit-at-a-time > > is there any difference / reason why in my case: > > -O1 > > fails but: > > -O0 -fcprop-registers -fdefer-pop -fguess-branch-probability > -fif-conversion -fif-conversion2 -fipa-pure-const -fipa-reference > -fmerge-constants -fomit-frame-pointer -fsplit-wide-types -ftree-ccp > -ftree-ch -ftree-copy-prop -ftree-copyrename -ftree-dce > -ftree-dominator-opts -ftree-dse -ftree-fre -ftree-salias -ftree-sink > -ftree-sra -ftree-ter -funit-at-a-time > > works?... With -O0 you get no optimization, regardless of the other options. > I build with athlon-xp architecture but same happens when I > do i686 (with tune=generic)... it's of course Linux, and I use GCC > 4.3.2 > btw, the problem I have is during run of OGRE3D engine so quite huge > app, I managed to track the problem up to this place: > > HardwareIndexBuffer::IndexType indexType = > mCurrentSection->get32BitIndices()? HardwareIndexBuffer::IT_32BIT : > HardwareIndexBuffer::IT_16BIT; > > there IndexType is enum for only those two values that in any other > context are 0/1, and get32BitIndices is function returning bool, this > makes it kind of: > > int x = boolValue ? 0:1; What does the declaration of IndexType look like? > the problem is that any diagnostic, stwich/case/if for that value > equal HardwareIndexBuffer::IT_32BIT or HardwareIndexBuffer::IT_16BIT > fail, simple cout on it says it's 104... always, every run - every > build with anything more than -O0... it's working on -O0 thought and > -O0 with above flags... anyway for now question is rather about what > more than flags returned by those 3 mentioned lines of shell does -O1 > do because I can just go on with disabling one feature and leaving > rest in place The bug is probably in your app, not in gcc. I think you'd be much better off fixing the bug than trying to discover which optimization pass it breaks. Andrew.
