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Difference between revisions of "News:CPU FLAGS X86"
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{{News | {{News | ||
|Summary=CPU_FLAGS_X86 are being introduced to group together USE flags managing CPU instruction sets. | |Summary=CPU_FLAGS_X86 are being introduced to group together USE flags managing CPU instruction sets. | ||
|News Format=Short | |||
|News Category=General | |News Category=General | ||
|Author=Mgorny | |Author=Mgorny | ||
|Publication Status= | |Publication Status=Published | ||
|Publication Date=2015/01/ | |Publication Date=2015/01/31 | ||
}} | }} | ||
Hello, everyone. | Hello, everyone. | ||
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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. | 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. | ||
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Revision as of 08:58, January 31, 2015
CPU FLAGS X86
Hello, everyone.
The USE flags corresponding to the instruction sets and other features specific to the x86 (including x86-64) architecture are being moved into a separate USE flag group called CPU_FLAGS_X86.
In order not to lose CPU-specific optimizations, users will be required to update their make.conf (and package.use) file. For example, if the following USE flags were present:
/etc/portage/make.conf - The original make.conf flagsUSE="mmx mmxext sse sse2 sse3"
Those flags need to be copied into:
/etc/portage/make.conf - The new make.conf flagsCPU_FLAGS_X86="mmx mmxext sse sse2 sse3"
Please note that the same CPU_FLAGS_X86 variable is used both on 32-bit and 64-bit x86 (amd64) systems.
When in doubt, you can consult the flag descriptions using one of the commonly available tools, e.g. equery uses from gentoolkit:
user $ equery uses media-video/ffmpeg
Most of the flag names match /proc/cpuinfo names, with the notable exception of SSE3 which is called 'pni' in /proc/cpuinfo (please also do not confuse it with distinct SSSE3).
To help users enable the correct USE flags, we are providing a Python script that generates the correct value using /proc/cpuinfo. It can be found in the No results package:
root # emerge -1v app-portage/cpuinfo2cpuflags user $ cpuinfo2cpuflags-x86
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.