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From: "dave at sr71 dot net" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug libc/18402] FPU use in application before main()
Date: Tue, 12 May 2015 16:40:00 -0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=18402

--- Comment #9 from Dave Hansen <dave at sr71 dot net> ---
(In reply to H.J. Lu from comment #8)
> (In reply to H.J. Lu from comment #7)
> > It is not ld.so which calls strrchr.  It is __init_misc in libc.so.
> 
> If we want to get rid of SSE optimized strrchr before main, we
> need a different strrchr.  However, if program or compiler call
> any string/memory functions, SSE registers may be used to optimize
> those string/memory functions.  The question is how much SSE usage
> impacts performance on real applications.

There's also the matter that the kernel tries to be lazy about allocating and
saving/restoring FPU state.  If the task is virtually guaranteed to have FPU
state, then we should reconsider the lazy mode being the default.

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