Re: More on Lisp structures performance

"Tim Bradshaw (as tfb at cley dot com)" <[email protected]>
Newsgroups gmane.lisp.lispworks.general
Message-ID <[email protected]>
On 24 Jan 2026, at 09:30, Yuri Davidovsky (as work at disclosure dot ie) <[email protected]> wrote:
> 
> 
> Hm. And how are you supposed to access individual 64 bit words using pointers whose addressing is aligned on 128 bits boundaries?

So the answer is that for LW I am wrong, I think.  LW can align on word boundaries (you can find such objects by just grovelling the heap with sweep-all-objects), and so has, I think, a three-bit tag, without fixnums sticking into the space of tags. Sorry: I should have tried more types in my code.

SBCL does do what I said LW does: there's a four-bit tag and all objects are double-word aligned (and, with wider fixnums, any tag whose low bit is zero is a fixnum).

--tim

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