CPU FLAGS X86

The USE flags corresponding to the instruction sets and other features specific to the / architecture are being moved into a separate USE_EXPAND variable called CPU_FLAGS_X86.

In order not to lose CPU-specific optimizations, users will be required to update their (and ) file. For example, if the following USE flags were present:

Those flags need to be copied into:

When in doubt, consult the flag descriptions using one of the commonly available tools, e.g. from :

Most of the flag names match names, with the notable exception of   which is called   in  (please also do not confuse it with distinct  ).

To help users enable the correct USE flags, a Python script is provided that generates the correct value using. It can be found in the package:

In order to ensure safe migration and maintain compatibility with external repositories, it is recommended to preserve the old USE settings for a period of one year or until no package of interest is still using them.

External resources

 * CPU_FLAGS_X86 introduction
 * https://packages.gentoo.org/useflags/search?q=cpu_flags_x86