On Thu, Apr 12, 2012 at 10:43 AM, Pedro Alves <pal...@redhat.com> wrote: > On 04/12/2012 04:23 PM, Gabriel Dos Reis wrote: > >> because -Os says it optimizes for size, the expectation is clear. >> -O3 does not necessarily give better optimization than -O2. > > > No, but it does mean that GCC turns on more optimization options. > > "Optimize yet more. -O3 turns on all optimizations specified by -O2 and also > turns on the -finline-functions, > -funswitch-loops, -fpredictive-commoning, -fgcse-after-reload, > -ftree-vectorize and -fipa-cp-clone options. "
I think we have perverted the meaning of "optimize yet more", and optimize yet more does not yield better/faster code :-) Yes, I understand the transformations; that does not justify for the awkward user-interface. > > Just like -W3 wouldn't necessarily generate more warnings on > your code than -W1, perhaps because your code is > already "clean" enough. It would simply be documented as: > > "-W3: Warn yet more. -W3 turns on all warnings specified by -W2 and also > ...". > > I'll also note the parallel with -glevel, not just -O. > > So, 'gcc -glevel -Wlevel -Olevel' feels quite natural to me. > > -- > Pedro Alves
