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From: "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups: comp.arch
Subject: Re: Keeping other stuff with addresses
Date: Tue, 3 Dec 2024 16:56:47 -0800
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On 12/3/2024 8:51 AM, Stefan Monnier wrote:
>> another way to steal bits is over alignment.
> 
> Yup.  I keep lamenting that Alpha didn't go for bit-addressed memory,
> which would have given us 3 extra free bits from alignment (as well as
> allowing pointers to bits and bitfields).

;^)

Wrt stealing bits I always revert back to the original pointer when I 
use it for anything to do with the system. Now, actually using the 
stolen bits, well we can over align on a _large_ boundary and use them 
for a smallish reference count and/or version counter. We can use them 
for state machines in some clever lock-free algorithms. We just need to 
only use the stolen bits for _our_ logic. Mask them off, get back to the 
original pointer "value" before we use that pointer for what's its 
pointing too. Never deference a pointer with stolen bits!!!!!!!!!!!!!!!!!!

Fair enough?