This is the mail archive of the libc-alpha@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Should we compile x86-64 ld.so with -mno-sse -mno-sse?


On Fri, Nov 2, 2012 at 1:35 AM, Andreas Jaeger <aj@suse.com> wrote:
> On 11/02/2012 12:20 AM, H.J. Lu wrote:
>>
>> On Thu, Nov 1, 2012 at 4:23 AM, Ondrej Bilka <neleai@seznam.cz> wrote:
>>>
>>> On Wed, Oct 31, 2012 at 04:18:10PM -0700, H.J. Lu wrote:
>>>>
>>>> On Wed, Oct 31, 2012 at 3:59 PM, Richard Henderson <rth@twiddle.net>
>>>> wrote:
>>>>>
>>>>> On 2012-11-01 03:10, Carlos O'Donell wrote:
>>>>>>
>>>>>> What use case is there for not wanting to touch SEE in ld.so?
>>>>>
>>>>>
>>>>> I can only imagine HJL is worried about AVX performance if the
>>>>> dynamic linker uses SSE insns.
>>>>>
>>>>
>>>> That is not the main reason.  We make sure that ld.so string/memory
>>>> functions never touch SSE/AVX registers.  It is not for performance,
>>>> but for correctness.  Otherwise callee will get random values in
>>>> vector registers,
>>>
>>>
>>> Or we can save and restore used xmm registers or I am missing something?
>>
>>
>> But it will introduce extra over head for every symbol lookup
>> and it wouldn't be forward compatible with AVX since we would
>> only save/restore 128bit SSE registers, not 256bit AVX registers.
>
>
> HJ, will you work on a patch?
>

I am working on it.


-- 
H.J.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]