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GCC-3.1 optimal arch flags automagically
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Klavs
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PostPosted: Thu May 30, 2002 7:56 am    Post subject: GCC-3.1 optimal arch flags automagically Reply with quote

Hi guys,

I was thinking that if we collected the optimal arch-flags for gcc-3.1 for all archs, this could be included in gentoo-iso, so emerge could automagically select the optimal flags for you - this way gentoo will automagically stay on top, as a super-optimized dist. What do you think?

Also, it would be great to know if profiling will improve speed on the given CPU-type - or is that more program dependant? from the benchmarks I've seen on gcc-3.1 with profiling it should definetely give approx. 5-10% extra - which is a lot in my mind. see https://forums.gentoo.org/viewtopic.php?t=2912 .

flags for:

Pentium


Pentium Pro (has MMX - any without?)


PII (has MMX - also other stuff?)


PIII (has MMX? - also other?)


K6-2


K6-3


Athlon

Athlon-XP
CHOST = i686-pc-linux-gnu
CXXFLAGS = -march=athlon-xp -m3dnow -msse -mfpmath=sse -mmmx -O3 -pipe
CFLAGS = -march=athlon-xp -m3dnow -msse -mfpmath=sse -mmmx -O3 -pipe

PPC

others..?
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Niek
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PostPosted: Thu May 30, 2002 10:34 am    Post subject: Reply with quote

You canfind a list of possible compile flags here: http://gcc.gnu.org/onlinedocs/gcc-3.1/gcc/i386-and-x86-64-Options.html#i386%20and%20x86-64%20Options
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kode54
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PostPosted: Thu May 30, 2002 12:36 pm    Post subject: Reply with quote

According to that document, the -mmmx, -msse, -msse2, -m3dnow, only enable (or disable in the case of the -mno_* variants) macro/functions that execute assembly instructions from the respective sets. They have nothing to do with automatic optimization of existing code.
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lx
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PostPosted: Thu May 30, 2002 12:38 pm    Post subject: Reply with quote

defining march=athlon-xp probably is enough and -m3dnow -msse -mmx is already used don't know about mfpmath buth i think so (march compiles the program for that particular architecture, 3dnow etc are part of that architecture). Besides a part of Xfree will not compile with march=athlon / march=athlon-tbird, i had to add -mno-mmx -mno-3dnow so it's probably included in march=athlon. Think that march=<architecture> -O3 gives the most optimal result and maybe -O2 should be used to avoid stability issues, if there are options that won't break the code, why aren't they included by the gcc coders????. Well that's one thing to find out then, :lol: , let's get this thing straightend out once and for all, but how do you want to test the performance gain / stability issues????

See ya, lX
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Klavs
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PostPosted: Thu May 30, 2002 2:11 pm    Post subject: Reply with quote

In regards to performance tests, I figured the way these guys has done it - isn't a bad one - see https://forums.gentoo.org/viewtopic.php?t=2912

In regards to stability - as with all code, only time and enough users will tell.. can there be any other way?
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Lovechild
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PostPosted: Thu May 30, 2002 2:53 pm    Post subject: Reply with quote

Klavs wrote:

In regards to stability - as with all code, only time and enough users will tell.. can there be any other way?


Better coders ? :lol:
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Pigeon
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PostPosted: Fri Jun 21, 2002 9:25 am    Post subject: Reply with quote

Pentium Pro's don't support MMX.

Pentium II's support MMX.

Pentium III's support MMX and SSE.

Pentium 4's support MMX, SSE, and SSE2, I think. (I know they have SSE2- don't know if they're backward compatable, though I'd assume they are)

All AMD's that are K6-3+ (I think... possibly K6-2) have 3dnow.

Which (if any) AMD processors have MMX and SSE support? I can't remember my history lessons =( (I wouldn't be suprised if none of them did... for some reason I thought SSE and MMX are proprietary)
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mglauche
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PostPosted: Fri Jun 21, 2002 10:48 am    Post subject: Reply with quote

hmm, my duron 1,3 k has:
3dnow, 3dnow+,mmx, mmx+ and sse (not sse2)

the lower durons don't have see flags
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karmakillernz
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PostPosted: Fri Jun 21, 2002 7:56 pm    Post subject: Reply with quote

Pigeon wrote:

All AMD's that are K6-3+ (I think... possibly K6-2) have 3dnow.

Which (if any) AMD processors have MMX and SSE support? I can't remember my history lessons =( (I wouldn't be suprised if none of them did... for some reason I thought SSE and MMX are proprietary)


Yea K6/2's have 3dnow (I used to have one :D) and all (at least from the K6/2) have mmx, and all Athlons have SSE (But not sse2).
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petecool
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PostPosted: Sun Jun 23, 2002 7:23 pm    Post subject: Reply with quote

Quote:
...and all Athlons have SSE (But not sse2).


That is not true, only Athlon XP and second generation Durons (they start at 1 or 1.1 Ghz, I'm not sure - they have an Xp-like core) have sse.
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Tuxisuau
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PostPosted: Mon Jun 24, 2002 4:19 am    Post subject: sse Reply with quote

Quote:

only Athlon XP and second generation Durons (they start at 1 or 1.1 Ghz, I'm not sure - they have an Xp-like core) have sse.

I'm not sure, but i think all socket A athlons (since athlon-tbird, the first one AFAIK) do have sse.[/quote]
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Safrax
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PostPosted: Mon Jun 24, 2002 3:02 pm    Post subject: Reply with quote

The slot Athlons and the TBird Athlons *DO NOT* have sse support. Only the newer Athlon-XP's (aka palomino) have SSE support.
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slik
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PostPosted: Tue Jun 25, 2002 8:31 pm    Post subject: Reply with quote

lx wrote:
defining march=athlon-xp probably is enough and -m3dnow -msse -mmx is already used don't know about mfpmath buth i think so (march compiles the program for that particular architecture, 3dnow etc are part of that architecture). Besides a part of Xfree will not compile with march=athlon / march=athlon-tbird, i had to add -mno-mmx -mno-3dnow so it's probably included in march=athlon. Think that march=<architecture> -O3 gives the most optimal result and maybe -O2 should be used to avoid stability issues, if there are options that won't break the code, why aren't they included by the gcc coders????. Well that's one thing to find out then, :lol: , let's get this thing straightend out once and for all, but how do you want to test the performance gain / stability issues????

See ya, lX


see here to find which flags are automatically set for your given -O? option
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Forge
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PostPosted: Wed Jul 03, 2002 6:02 pm    Post subject: Reply with quote

Please see my comments in this thread to determine what features your K7 does/does not have.
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