/Ox (Enable Most Speed Optimizations)
The /Ox compiler option enables a combination of optimizations that favor speed. In some versions of the Visual Studio IDE and the compiler help message, this is called full optimization, but the /Ox compiler option enables only a subset of the speed optimization options enabled by /O2.
The /Ox compiler option enables the /O compiler options that favor speed. The /Ox compiler option does not include the additional /GF (Eliminate Duplicate Strings) and /Gy (Enable Function-Level Linking) options enabled by /O1 or /O2 (Minimize Size, Maximize Speed). The additional options applied by /O1 and /O2 can cause pointers to strings or to functions to share a target address, which can affect debugging and strict language conformance. The /Ox option is an easy way to enable most optimizations without including /GF and /Gy. For more information, see the descriptions of the /GF and /Gy options.
The /Ox compiler option is the same as using the following options in combination:
/Ob (Inline Function Expansion), where the option parameter is 2 (/Ob2)
/Ox is mutually exclusive from:
You can cancel the bias toward speed of the /Ox compiler option if you specify /Oxs, which combines the /Ox compiler option with /Os (Favor Small Code). The combined options favor smaller code size. The /Oxs option is exactly the same as specifying /Ox /Os when the options appear in that order.
To apply all available file-level optimizations for release builds, we recommend you specify /O2 (Maximize Speed) instead of /Ox, and /O1 (Minimize Size) instead of /Oxs. For even more optimization in release builds, also consider the /GL (Whole Program Optimization) compiler option and /LTCG (Link-time Code Generation) linker option.
To set this compiler option in the Visual Studio development environment
Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.
Under Configuration Properties, open C/C++ and then choose the Optimization property page.
Modify the Optimization property.
To set this compiler option programmatically
- See Optimization.