[Bug math/20495] x86_64 performance degradation due to AVX/SSE transition penalty

[kungfujesus06 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20495

--- Comment #10 from Adam Stylinski <kungfujesus06 at gmail dot com> ---
Interesting, I will have to try that link flag. What is the reason for that
working? Everything I can find about that flag is for hardening binaries to
prevent others from writing into the global offset table.

On Aug 25, 2016 4:03 PM, "andrew.n.senkevich at gmail dot com" <
sourceware-bugzilla@sourceware.org> wrote:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=20495
>
> --- Comment #8 from Andrew Senkevich <andrew.n.senkevich at gmail dot
com> ---
> (In reply to Adam Stylinski from comment #2)
> > Created attachment 9469 [details]
> > Slower AVX example
> >
> > Compile this with -mavx & then compile it with -msse4.  The -msse4
version
> > will be faster as it's not hitting the SSE to AVX register transition
> > penalty.
>
> You can avoid slowdown also using "-Wl,-z,now".
>
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