On Sat, Apr 13, 2024 at 5:55 PM Richard W.M. Jones <rjo...@redhat.com> wrote:
> On Fri, Apr 12, 2024 at 07:08:36PM -0500, Neal Gompa wrote: > > I would like for us to consider evaluating a global change to -O3. I > > am not convinced that there's a good reason anymore to remain at -O2. > > FYI here are the optimizations added by gcc -O3 (over -O2), from > https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html > > -fgcse-after-reload > -fipa-cp-clone > -floop-interchange > -floop-unroll-and-jam > -fpeel-loops > -fpredictive-commoning > -fsplit-loops > -fsplit-paths > -ftree-loop-distribution > -ftree-partial-pre > -funswitch-loops > -fvect-cost-model=dynamic > -fversion-loops-for-strides > > Mainly lots of loop optimizations :-) > > For clang, -O3 is simply described as this, I can't immediately find > any more detail: > > -O3 Like -O2, except that it enables optimizations that take longer > to perform or that may generate larger code (in an attempt to make > the program run faster). > Clang enables a small number of additional optimizations at O3 (the most important of which are probably argument promotion and non-trivial loop unswitching), but probably the largest difference is that O3 uses higher cost thresholds for things like inlining and unrolling. Regards, Nikita
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