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Re: RFC: Enable multi-arch support for i386

On Mon, Aug 17, 2015 at 8:20 AM, Joseph Myers <> wrote:
> On Mon, 17 Aug 2015, H.J. Lu wrote:
>> On Mon, Aug 17, 2015 at 8:06 AM, Joseph Myers <> wrote:
>> > On Mon, 17 Aug 2015, H.J. Lu wrote:
>> >
>> >> Since _dl_x86_cpu_features is available for i386 now, we can
>> >> move sysdeps/i386/i686/multiarch to sysdeps/i386/multiarch.
>> >> That means to make multi-arch available for i486 and i586.
>> >> Should I post a patch to do it?
>> >
>> > I think the principle of having it available there makes sense.  However,
>> > various files in sysdeps/i386/i686/multiarch include other files from ../
>> > (i.e. i686 versions) or ../i486/ or ../i586/.  So you'd need to make sure
>> > such a change doesn't pessimize things or use unavailable instructions in
>> > those fallback versions - the files should include the i686/ versions if
>> > __i686__ is defined, etc., making sure to include the best version
>> > applicable to the processor for which glibc is compiled (of course i486/
>> > versions are always OK to use since i386 isn't supported any more).
>> I will detect i586/i686 at run-time and select the best one for the hardware.
> If, however, glibc is built for i686, then it's best to save on that
> conditional and the extra i486 / i586 copy of the code, and just build in
> the i686 version (whereas if it's built for i486 or i586, it's best to
> have both).

I am in the process of moving sysdeps/i386/i686/multiarch to
sysdeps/i386/multiarch. I have moved memcpy and memset
so far.  Please take a look at hjl/i486/multiarch branch.


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