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

[andrew.n.senkevich at gmail dot com]

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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