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From: Eli Zaretskii <eliz@gnu.org>
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Subject: Re: Crashes in "C-h h"
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> Cc: pipcet@gmail.com, emacs-devel@gnu.org
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Thu, 4 Jul 2019 00:15:12 -0700
> 
> 1030-lnxsrv09 $ time ./a.out 0 0
> 
> real	0m51.933s
> user	0m51.927s
> sys	0m0.001s
> 1031-lnxsrv09 $ time ./a.out 0 0 0
> 
> real	2m16.960s
> user	2m16.960s
> sys	0m0.000s
> 1032-lnxsrv09 $ time ./a.out 0 0 0 0
> 
> real	0m59.678s
> user	0m59.677s
> sys	0m0.001s

Thanks.

> This indicates that on this !USE_LSB platform, the EQ+make_fixnum code is about 
> ten times faster than the FIXNUMP+XFIXNUM code on this benchmark.

You mean twice faster (~2m vs ~1m), right?

> I'm not surprised by the performance disparity, as branch-prediction
> failures can be pretty expensive.

Which indeed means that if the object is not guaranteed to be a
fixnum, using XFIXNUM is generally suboptimal.