On 22 October 2015 at 15:46, Mohamed Boussaa <mohamedboussaa3@xxxxxxxxx> wrote: > To answer my question, I have made some conclusions and assumptions: > > So let me say that compiling with O0 does not mean that no > optimizations will be applied. Wrong. > Options that reduce compilation time > and make debugging better will be turned on. Wrong. At -O0 options that would _increase_ compilation time are _not_ turned on. > In other words, O0 is optimizing in the level of compilation. Produced > binaries are not optimized in order to ease debugging process. I don't know what this means. > I give an example: This option is enabled at O0 level > > -faggressive-loop-optimizations No it isn't. > In GCC documentation: > > This option tells the loop optimizer to use language constraints to > derive bounds for the number of iterations of a loop. This assumes > that loop code does not invoke undefined behavior by for example > causing signed integer overflows or out-of-bound array accesses. The > bounds for the number of iterations of a loop are used to guide loop > unrolling and peeling and loop exit test optimizations. This option is > enabled by default. > > So for GCC 4.8.x, there are almost 50 options turned on by default. Wrong. > Can someone confirm that? No, because you're wrong, as Andrew has said twice.
