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