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Re: Changing CFLAGS for i386 packages on x86_64



Arjan van de Ven wrote:
On Fri, 2006-07-14 at 10:06 +0200, dragoran wrote:
Paul Howarth wrote:
On Fri, 2006-07-14 at 08:13 +0200, dragoran wrote:
On i386 most of the packages are i386 and there are some i686 one like kernel and glibc. On x86_64 there are some i386 packages installed by default too. Why are they compiled with the same settings as on i386? On x86_64 it wont hurt enabling i686 (cmov) and see2 because all x86_64 cpus support this instructions.
Doing this would result in i386 packages in the x86_64 repo that are
different from the identically-named i386 packages in the i386 repo,
wouldn't it, since all Fedora arches are built from exactly the same
SRPMS?

Paul.


no it wont because they will be i686 builds and RPM_OPT_FLAGS would be differnet so the same SRPM can be used.


but to what point?

I will actually here propose to stop doing i686 builds for most of the
things it's done now; cmov just isn't worth it, and if you want to use
SSE in 32 bit, that's not going to be cheap either (unlike 64 bit where
it's a standard part of the ABI); SSE in 32 bit is not "just used" by
gcc, only hand coded assembly uses it basically, and those can use .i386
just fine since generally they have a runtime detection mechanism.

what do you mean by not used by gcc? there are flags to use it -msse2 ...
many apps have runtime detection and use handcoded assembly but not all of them
And for optimization... even the i386 rpms are already optimized for
modern processors so there's no difference there either.



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