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pauldv
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PostPosted: Tue Apr 01, 2003 8:26 am    Post subject: Reply with quote

making your CFLAGS to be:
-march=pentium3 -mcpu=pentium4 should provide good scheduling while still using the safest options. march and mcpu do not have to be equal
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FlipFlop
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Joined: 03 Mar 2003
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PostPosted: Tue Apr 01, 2003 8:44 am    Post subject: Test Reply with quote

I'ev just changed my cflags to -march=pentium3 -mcpu=pentium4 -mmmx -msse -msse2 -O3 -fomit-frame-pointer -pipe -mfpmath=sse,387

(used to be just -march=pentium3 -O3 -pipe)

Then i emerged glibc and python and ran the python int conversion test line.

It worked fine .. i should see the overflow error if the settings didnt work right?
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ben_h
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PostPosted: Wed Apr 02, 2003 4:12 pm    Post subject: Reply with quote

Hi all, I thought I'd just put this in -- I've got a P4 1.8 (a Northwood), and I've just reinstalled Gentoo using

CFLAGS='--march=pentium4 -O2 -pipe'

And everything works perfectly, although the python compile test above does give me "OverflowError: float too large to convert".

Hope this helps someone. :D
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FlipFlop
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PostPosted: Thu Apr 03, 2003 7:17 am    Post subject: well Reply with quote

As i understand it that is exacly the situation where everything isn't working perfectly..
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Chris Finch
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PostPosted: Thu Apr 03, 2003 10:51 pm    Post subject: Question to Zadeh, comment on mplayer Reply with quote

Zadeh wrote:

Quote:

There are known codegen problems with SSE2 insns that are enabled when you use -march=pentium4 (equivalent to: -mcpu=pentium4 -msse2).

I've noticed some ebuilds rewrite your C[XX]FLAGS if -march=pentium4 is detected to -march=pentium3. -mcpu=pentium4 works fine though, and comments floating around in e.g. /etc/make.conf about it and switching to -march/-mcpu=pentium3 in ebuilds are just plain wrong.


Dear Zadeh, I understand "-march=pentium4" is harmful. Does your comment imply that "-mcpu=pentium4 -msse2" is equally harmful? Should I so switch off sse2 as well?

On a slightly different subject: I have noticed that while recompiling mplayer, the "-march=pentium4" option was still active, although I had switched it off in make.conf. The configure script sets the flags for itself, unless they are already set. If you have a pentium4, you can comment out the "unset" line and add the CFLAGS/CXXFLAGS definitions in the ebuild manually as follows:
Code:

        # Crashes on start when compiled with most optimizations.
        # The code have CPU detection code now, with CPU specific
        # optimizations, so extra should not be needed and is not
        # recommended by the authors
        # unset CFLAGS CXXFLAGS
        CFLAGS="-O4 -mcpu=pentium4 -pipe -ffast-math -fomit-frame-pointer"
        CXXFLAGS="$CFLAGS"

the CFLAGS are what configure would choose, minus the "-march=pentium4" option. Does anybody know of other ebuilds/configure scripts that result in a harmful compiler option?

Peter
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zeek
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PostPosted: Fri Apr 04, 2003 1:22 pm    Post subject: why not remask gcc 3.2? Reply with quote

I had this problem a few months ago also as noted here:

https://forums.gentoo.org/viewtopic.php?t=28551&highlight=glibc+conversion

why not remask gcc 3.2? (rhetorical question)
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pauldv
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PostPosted: Thu Apr 10, 2003 11:30 am    Post subject: Re: Question to Zadeh, comment on mplayer Reply with quote

Chris Finch wrote:
Zadeh wrote:

Dear Zadeh, I understand "-march=pentium4" is harmful. Does your comment imply that "-mcpu=pentium4 -msse2" is equally harmful? Should I so switch off sse2 as well?


There should never be a reason to specify -msse2 or mmx options or any. And yes the problem involves sse2, so that is harmfull too.

Quote:

On a slightly different subject: I have noticed that while recompiling mplayer, the "-march=pentium4" option was still active

Yes, mplayer does it's own optimization detection. You shouldn't want to touch that.
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