Re: freeze for sbcl-2.6.8

Douglas Katzman via Sbcl-devel <[email protected]> Sat, 22 Aug 2026 12:07:05 -0400

Newsgroups	gmane.lisp.steel-bank.devel
Message-ID	<CAOrNasx5AJ_3jb9q=EFsGjs6mAbZJKThwj=O1xXK=uqN1V7org@mail.gmail.com>

I have the fix for that crash.   I mistakenly thought that
FPR-SAVE/FPR-RESTORE no longer need to preserve RDX when using XRSTOR but
they still do - but only for #+win32, so I'll add that.
However, Gemini claims the following theoretical performance gain by simply
avoiding XSAVE/XRSTOR entirely in the YMM case (not the avx512 of course)
which is a very interesting point -

   1. ~4x Faster: 16 * VMOVAPS runs in ~15–20 cycles vs 80+ cycles for XSAVE
   /XRSTOR.

Do you think I can commit this register changing patch + its fix for now,
and we'll leave the above suggestion for next release (despite also being a
valid fix for my crash) ?

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