c++performancegccoptimizationg++

What extra optimisation does g++ do with -Ofast?

In g++ 4.6 (or later), what extra optimisations does -Ofast enable other than -ffast-math?

The man page says this option "also enables optimizations that are not valid for all standard compliant programs". Where can I find more information about whether this might affect my program or not?

Solution

  • Here's a command for checking what options are enabled with -Ofast:

    $ g++ -c -Q -Ofast --help=optimizers | grep enabled

    Since I only have g++ 4.4 that doesn't support -Ofast, I can't show you the output.