F22 System Wide Change: Harden all packages with position-independent code

[drago01]

On Mon, Jan 19, 2015 at 9:41 PM, Reindl Harald <h.reindl at thelounge.net> wrote:
>
>
> Am 19.01.2015 um 21:34 schrieb drago01:
>>
>> On Mon, Jan 19, 2015 at 3:42 PM, Reindl Harald <h.reindl at thelounge.net>
>> wrote:
>>>
>>>
>>> Am 19.01.2015 um 15:28 schrieb Gerd Hoffmann:
>>>>>>
>>>>>>
>>>>>> Would that make it impossible to run fedora on sse-only i686 CPUs?
>>>>>
>>>>>
>>>>>
>>>>> Yes, but test coverage for those CPUs is already rather poor, so I
>>>>> don't
>>>>> expect them to work anymore.
>>>>
>>>>
>>>>
>>>> See other replies, people are running such machines.
>>>>
>>>> Given x86_64 exists for many years and even embedded (see aarch64) is
>>>> moving to 64bit these days i386 clearly is for old legacy hardware.  If
>>>> you need performance you don't run a i386 machine.
>>>>
>>>> So, why bother raising the bar for i386 by requiring more cpu features?
>>>> It doesn't help anyone.
>>>
>>>
>>>
>>> "rpmrc" has optflags: for different architectures
>>>
>>> so why not optimize only "optflags: x86_64" for more recent hardware?
>>> since i686 is a complete different build anyways it won't matter
>>>
>>> on my private builders it's "-mmmx -msse2 -msse3 -msse4.1 -msse4.2 -maes
>>> -mfpmath=sse"
>>
>>
>> Because that doesn't make sense for multiple reasons:
>
>
> you show none below because it said "keep i686 flags unchanged"
>
>> 1) mmx is basically obsolete
>
>
> in theory

And in practice. Why would you want to use mmx if you have sse2+
available? (you don't).

>> 2) sse2 is the default fp ABI on x86_64 anyway and thus supported by
>> *all* x86_64 cpus
>
>
> so be it
>
>> 3) Requiring sse4.2 or even 4.1 would exclude a lot of hardware
>
>
> did i propose that?

It wasn't clear from your mail what your proposal actually is.

> i said "private builders" to show that keep supporting > 10 years old
> hardware is just silly because you waste HW capabilities - noweher did i
> propose *that* falgs
>
>> 4) You don't just throw in some compiler flags and assume it will gain
>> you anything (you'd probably have to either turn on O3 or
>> vectorization as well)
>
>
> -O3 is the default for my builds starting with 2006
>
>> .. most applications where it really matters do
>> detection at runtime (even glibc does that)
>
>
> the topic is still: hwta can be changed in the x86_64 flags *without* break
> old 32bit crap some people rely for several reasons

OK .. well there is no reason why the flags have to be shared between
x86_64 and the "32bit crap" ... if you stop carring about 32bit
*hardware* we could use sse2 just fine for i686 (people using 32bit
applications on top of x86_64 would benefit from it).