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lenin
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PostPosted: Mon Nov 22, 2010 1:24 am    Post subject: About 'USE' in make.conf Reply with quote

My CPU is Athlon II X3 435 , how should I set 'USE' in make.conf to make compile match my CPU ? Thanks.
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chithanh
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PostPosted: Mon Nov 22, 2010 3:18 am    Post subject: Reply with quote

You don't need to set USE flags for your CPU. CFLAGS however you might want. http://en.gentoo-wiki.com/wiki/Safe_Cflags
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mattst88
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PostPosted: Mon Nov 22, 2010 6:43 am    Post subject: Reply with quote

There are use flags for assembly optimizations. Your CPU has the following.

USE="3dnow 3dnowext mmx mmxext sse sse2 sse3"
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ShadowHawkBV
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PostPosted: Sat Jun 25, 2011 3:58 pm    Post subject: Reply with quote

Quote:
There are use flags for assembly optimizations. Your CPU has the following.

USE="3dnow 3dnowext mmx mmxext sse sse2 sse3"


Do the sse keys act recursively? If I add sse3 to my USE, will sse and sse2 automatically be applied as necessary? I seem to remember that being the case for CFLAGS, but am unsure about USE.
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mattst88
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PostPosted: Sat Jun 25, 2011 4:38 pm    Post subject: Reply with quote

ShadowHawkBV wrote:
Quote:
There are use flags for assembly optimizations. Your CPU has the following.

USE="3dnow 3dnowext mmx mmxext sse sse2 sse3"


Do the sse keys act recursively? If I add sse3 to my USE, will sse and sse2 automatically be applied as necessary? I seem to remember that being the case for CFLAGS, but am unsure about USE.


No, you should add them manually.
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ShadowHawkBV
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PostPosted: Tue Jun 28, 2011 12:33 am    Post subject: Reply with quote

Thank you for the clarification.
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xaviermiller
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PostPosted: Sun Jul 31, 2011 3:40 pm    Post subject: Reply with quote

Some profiles enable "cpu" USE flags, such as amd64 (enabling SSE* MMX, ...)
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wcg
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PostPosted: Sat Aug 06, 2011 1:58 pm    Post subject: Reply with quote

"cat /proc/cpuinfo" should tell you what the cpu has available in its
instruction set (see the "flags" entry). "-march=native" in CFLAGS
in /etc/make.conf should pull in any of those that are relevant to
the current code that gcc is compiling.
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Terrel Shumway
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PostPosted: Fri Aug 26, 2011 10:27 pm    Post subject: I think it is automatic Reply with quote

/usr/portage/profiles/arch/amd64/use.mask
Quote:

# Feb 16th 2007; Simon Stelling <blubb@gentoo.org>
# Since this profile forces >=portage-2.1.2, we can unmask all
# SIMD assembler flags
-mmx
-mmxext
-sse
-sse2
-sse3
-sse4
-sse4a
-sse5
-3dnow
-3dnowext


Doesn't this mean that all of these are automatically enabled for all amd64 profiles?
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wcg
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PostPosted: Sat Aug 27, 2011 6:03 pm    Post subject: Reply with quote

Quote:
Doesn't this mean that all of these are automatically enabled for all amd64 profiles?


It would simply mean that they are not forbidden (masked). Whether they are actually
used by a particular ebuild would likely be conditional on other tests (since not all
amd64 cpus implement all of those instruction set extensions).
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