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i7-8700 Coffee Lake S system compilation logic
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bagas
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Joined: 29 Jun 2018
Posts: 45

PostPosted: Fri Oct 12, 2018 9:49 am    Post subject: i7-8700 Coffee Lake S system compilation logic Reply with quote

Hello
Tell me what logic of compilation / assembly of the system is better to specify for the processor intel i7-8700.
I have not forgotten anything?
make.conf
Code:
CHOST="x86_64-pc-linux-gnu"
CFLAGS="-march=skylake -O2 -pipe"
CXXFLAGS="${CFLAGS}"
FFLAGS="${CFLAGS}"
CPU_FLAGS_X86="mtrr sse sse2 sse3 ss ssse3 pae mmx mmxext sse4.1 sse4.2 avx2 aes"
MAKEOPTS="-j12"
CC=gcc
CXX=g++
FEATURES="-parallel-fetch -collision-protect -xattr"
DISTDIR="/mnt/distfiles"
PORTAGE_TMPDIR="/mnt/tmp"
GENTOO_MIRRORS="http://mirror.yandex.ru/gentoo-distfiles"
VIDEO_CARDS="intel i965"
ALSA_CARDS="hda-intel"
INPUT_DEVICES="mouse keyboard"
LINGUAS="ru en"
GRUB_PLATFORMS="pc"
USE="freetype -gnome -samba -cups thunar consolekit policykit pam udev bash-completion unicode 7zip xorg esd xvmc dxr3 audiofile vidix aalib vcd -hal xvid lua bzip2 dbus a52 aac amr accessibility oss mng vorbis crypt python perl flac -arts ieee1394 -kdevelop xine tiff djvu glib mtrr dvd slang lzo -kde alsa cdr sse sse2 ss ssse3 sse4.1 sse4.2 avx2 aes pae mp3 X mmx ogg -ipv6 -kdeenablefinal -kdehiddenvisibility jpeg gif -sudo pnp png usb pdf -multilib pdo"
ACCEPT_LICENSE="AdobeFlash-11.x AdobeFlash-10.3 Nero-EULA-US AdobeFlash-10 skype-eula skype-4.0.0.7-copyright dlj-1.1 google-chrome OPERA-12"
EMERGE_DEFAULT_OPTS="--autounmask=n"
PHP_INI_VERSION=production
L10N="ru"
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toralf
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Joined: 01 Feb 2004
Posts: 3607
Location: Hamburg

PostPosted: Fri Oct 12, 2018 10:09 am    Post subject: Reply with quote

/me wonders if a generic
Code:
CFLAGS="-march=native -O2 -pipe"
would work too?
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bagas
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Joined: 29 Jun 2018
Posts: 45

PostPosted: Fri Oct 12, 2018 10:41 am    Post subject: Reply with quote

toralf wrote:
/me wonders if a generic
Code:
CFLAGS="-march=native -O2 -pipe"
would work too?

You want to say that this aggressive setting to compile CFLAGS="-march=skylake -O2 -pipe" ?
And it is better to use CFLAGS="-march=native -O2 -pipe"?
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fedeliallalinea
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PostPosted: Fri Oct 12, 2018 11:21 am    Post subject: Reply with quote

bagas wrote:
You want to say that this aggressive setting to compile CFLAGS="-march=skylake -O2 -pipe" ?
And it is better to use CFLAGS="-march=native -O2 -pipe"?

Teorically if your cpu is really skylake there is no difference. "-march=native causes the compiler to auto-detect the architecture of the build computer." (man gcc).

You can check difference with
Code:
$ gcc -march=native -Q --help=target | grep march
$ gcc -march=native -v -Q --help=target
$ gcc -march=skylake -v -Q --help=target

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bagas
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PostPosted: Fri Oct 12, 2018 1:23 pm    Post subject: Reply with quote

fedeliallalinea wrote:
bagas wrote:
You want to say that this aggressive setting to compile CFLAGS="-march=skylake -O2 -pipe" ?
And it is better to use CFLAGS="-march=native -O2 -pipe"?

Teorically if your cpu is really skylake there is no difference. "-march=native causes the compiler to auto-detect the architecture of the build computer." (man gcc).

You can check difference with
Code:
$ gcc -march=native -Q --help=target | grep march
$ gcc -march=native -v -Q --help=target
$ gcc -march=skylake -v -Q --help=target

You are right, I will specify native to be automatically detected.
I have a family of processors Coffee Lake S .

And CPU_FLAGS_X86 indicated the correct?
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fedeliallalinea
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PostPosted: Fri Oct 12, 2018 1:52 pm    Post subject: Reply with quote

bagas wrote:
And CPU_FLAGS_X86 indicated the correct?

For these you can use app-portage/cpuid2cpuflags
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Duncan Mac Leod
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PostPosted: Sun Oct 14, 2018 9:22 pm    Post subject: Reply with quote

I have used CFLAGS="-march=core-avx2 -O2 -pipe" for my Skylake and Kaby Lake CPUs, even for my Skylakes running under VMware, without any problems.

I would also use this setting on a Coffee Lake CPU if I would own one :wink:

Just my 2 cents...
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