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On Wednesday 27 Jul 2011 17:13:21 Kfir Lavi wrote: |
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> On Wed, Jul 27, 2011 at 5:34 PM, Kfir Lavi <lavi.kfir@×××××.com> wrote: |
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> > On Wed, Jul 27, 2011 at 5:09 PM, Andy Wilkinson |
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> >> |
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> >> Another good trick I've found on the forums is to run: |
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> >> $ gcc -### -e -v -march=native /usr/include/stdlib.h |
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> >> |
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> >> The last line of output will include the various CFLAGS that |
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> >> -march=native |
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> >> |
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> >> picks. In my case (Phenom II 955): |
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> >> "/usr/libexec/gcc/x86_64-pc-linux-gnu/4.4.5/cc1" "-quiet" |
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> >> |
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> >> "/usr/include/stdlib.h" "-D_FORTIFY_SOURCE=2" *"-march=amdfam10" |
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> >> "-mcx16" "-msahf" "-mpopcnt"* "--param" "l1-cache-size=64" "--param" |
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> >> "l1-cache-line-size=64" "--param" "l2-cache-size=512" "-mtune=amdfam10" |
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> >> "-quiet" "-dumpbase" "stdlib.h" "-auxbase" "stdlib" "-o" |
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> >> "/tmp/ccR1PlNZ.s" "--output-pch=/usr/include/stdlib.h.gch" |
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> >> |
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> >> I typically use -march=native when I don't need to worry about distcc, |
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> >> or the options from that output that start with "-m". |
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> Just shared this trick in my blog. |
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> http://gentoo-what-did-you-say.blogspot.com/2011/07/finding-cpu-flags-using |
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> -gcc.html I added a link to this thread in the post. |
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It seems that on my early i7, the -march=core2 does not have all the -msse* |
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flags enabled, while native does: |
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$ diff -y --suppress-common-lines core2.txt native.txt |
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-mcx16 [disabled] | -mcx16 [enabled] |
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-mno-sse4 [enabled] | -mno-sse4 [disabled] |
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-mpopcnt [disabled] | -mpopcnt [enabled] |
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-msahf [disabled] | -msahf [enabled] |
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-msse [disabled] | -msse [enabled] |
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-msse2 [disabled] | -msse2 [enabled] |
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-msse3 [disabled] | -msse3 [enabled] |
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-msse4 [disabled] | -msse4 [enabled] |
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-msse4.1 [disabled] | -msse4.1 [enabled] |
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-msse4.2 [disabled] | -msse4.2 [enabled] |
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-mssse3 [disabled] | -mssse3 [enabled] |
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-mtune= | -mtune= core2 |
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I wonder if I should just set it to "-march=native -O2 -pipe" and forget about |
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it ... native it seems to have more stuff switched on and it would probably be |
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a-good-thing® (although my understanding of what each flag does is rather |
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cursory). |
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-- |
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Regards, |
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Mick |
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