Thank you for the clarification. On Wed 11 Nov, 2020, 1:57 AM Jonathan Wakely, <jwakely.gcc@xxxxxxxxx> wrote: > > > On Tue, 10 Nov 2020, 19:20 Ezhil P via Gcc-help, <gcc-help@xxxxxxxxxxx> > wrote: > >> hi, >> came across this in website >> >> *https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html* >> <https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html> >> >> >> ............................................................................................................. >> >> -fprofile-use >> >> -fprofile-use=*path* >> >> Enable profile feedback-directed optimizations, and the following >> optimizations, *many of which are generally profitable only with profile >> feedback available: * >> >> -fbranch-probabilities -fprofile-values >> >> -funroll-loops -fpeel-loops -ftracer -fvpt >> >> -finline-functions -fipa-cp -fipa-cp-clone -fipa-bit-cp >> >> -fpredictive-commoning -fsplit-loops -funswitch-loops >> >> -fgcse-after-reload -ftree-loop-vectorize -ftree-slp-vectorize >> >> -fvect-cost-model=dynamic -ftree-loop-distribute-patterns >> >> -fprofile-reorder-functions >> >> >> ......................................................................................................... >> >> >> O3 optimization uses most of these flags. >> >> >> Since it has been mentioned as above I assumed that some optimization >> flags >> specified here cannot function without profile info. >> > > > No, that's not what it says. > > >> >> Can you please clarify whether the flags mentioned above can function >> without using profile information by just specifying O3? >> > > > Some of them work much better with profile information, but some work OK > even without profile information. > > The text you quoted above doesn't say they don't function, it says they > don't function **well**. And it doesn't say that is true for all of them. > > > >
