Default ISA/tuning flags for GCC, --enable-kernel= level for glibc

Josh Boyer jwboyer at
Mon Jan 26 13:18:52 UTC 2009

On Mon, Jan 26, 2009 at 02:12:09PM +0100, Jakub Jelinek wrote:
>On Mon, Jan 26, 2009 at 07:45:20AM -0500, Josh Boyer wrote:
>> On Mon, Jan 26, 2009 at 11:15:01AM +0100, Jakub Jelinek wrote:
>> For ppc, the most common hardware would be the G4 PowerMacs.  Use of
>> -march=power4 would seem suboptimal there.  Which sort of sucks because
>Suboptimal is probably wrong word, it would preclude Fedora 11 running on

Yes, I was being cautious because I didn't have any coffee in me yet and
didn't want to proclaim DOOM immediately :).

>G4.  I guess we can keep -march for -m32 powerpc unchanged then, -mtune
>will be still power6.  We can default to -march=power4 for -m32 for RHEL
>only (already RHEL5 has power4 built shared glibc libraries).

OK.  So default32 for ppc, power4 for ppc64.

(btw, it's -mcpu on PowerPC, but you probably knew that already.)

>> >For the -march/-mcpu default changes, I think nothing is required from the
>> >koji build infrastructure (I don't think there are 31-bit mainframes
>> >around in koji/brew and I don't think there are 32-bit powerpcs or
>> >i386/i486s among the build boxes either), on the other side that decision
>> >has to be made almost immediately (before the world is rebuilt with gcc
>> >4.4.0).
>> I'm going to assmue that you are wanting a mass-rebuild of all of Fedora with
>> gcc 4.4.  Is that going to land this week?  From a scheduling perspective,
>> if a rebuild is going to happen it would be fairly important to have most of
>> it done by Beta.  Feature freeze is March 3rd.  Beta freeze is March 10.
>Yes, I want a mass rebuild with gcc 4.4 for Fedora 11, and new gcc can land
>into dist-f11 during this week.

OK.  We'll need to run that past FESCo, but I don't think there will be much
opposition to it.

>> >For glibc --enable-kernel= default this requires that all koji build boxes
>> >and anything else that needs to run Fedora 11 binaries runs at least 2.6.29
>> >kernels, but the change might be still delayed for a few weeks.
>> The koji build boxes all run RHEL 5.  Getting them upgraded to a not-yet-
>> released kernel seems unlikely.
>I know it is a pain, on the other hand it would really improve Fedora 11.

I agree.  Does it have to be .29, or would something slightly older (and
theoretically more stable) suffice?  The .27.x release has been in use for
F-9 and F-10 for a while now.


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