Difference between pages "Template:PageNeedsUpdates" and "News:CPU FLAGS X86"

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{{News
[[Category:Needs Updates]]
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|Summary=CPU_FLAGS_X86 are being introduced to group together USE flags managing CPU instruction sets.
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|News Format=Extended
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|News Category=General
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|Author=Mgorny
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|Publication Status=Published
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|Publication Date=2015/01/31
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}}
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Hello, everyone.
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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.
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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:
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{{file|name=/etc/portage/make.conf|desc=The original make.conf flags|body=
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USE="mmx mmxext sse sse2 sse3"
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}}
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Those flags need to be copied into:
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{{file|name=/etc/portage/make.conf|desc=The new make.conf flags|body=
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CPU_FLAGS_X86="mmx mmxext sse sse2 sse3"
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}}
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Please note that the same CPU_FLAGS_X86 variable is used both on 32-bit and 64-bit x86 (amd64) systems.
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When in doubt, you can consult the flag descriptions using one of the commonly available tools, e.g. ''equery uses'' from gentoolkit:
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{{console|body=
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$##i## equery uses media-video/ffmpeg
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}}
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Most of the flag names match /proc/cpuinfo names, with the notable exception of SSE3 which is called 'pni' in /proc/cpuinfo (please also do not confuse it with distinct SSSE3).
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To help users enable the correct USE flags, we are providing a Python script that generates the correct value using /proc/cpuinfo. It can be found in the {{Package|app-portage/cpuinfo2cpuflags}} package:
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{{console|body=
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###i## emerge -1v app-portage/cpuinfo2cpuflags
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$##i## cpuinfo2cpuflags-x86
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}}
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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.
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{{NewsFooter}}

Latest revision as of 08:59, January 31, 2015

CPU FLAGS X86

CPU_FLAGS_X86 are being introduced to group together USE flags managing CPU instruction sets.

By Mgorny / January 31, 2015

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 flags
USE="mmx mmxext sse sse2 sse3"

Those flags need to be copied into:

/etc/portage/make.conf - The new make.conf flags
CPU_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:

$ 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 app-portage/cpuinfo2cpuflags (package not on wiki - please add) package:

# emerge -1v app-portage/cpuinfo2cpuflags
$ 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.

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