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Re: Here come the 128-bit pointers

From BGB <cr88192@gmail.com>
Newsgroups comp.lang.c
Subject Re: Here come the 128-bit pointers
Date 2022-01-25 02:31 -0600
Organization A noiseless patient Spider
Message-ID <ssochk$t26$1@dont-email.me> (permalink)
References <RZBHJ.39378$gX.11188@fx40.iad> <sso8kg$82t$1@dont-email.me>

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On 1/25/2022 1:25 AM, Bonita Montero wrote:
> Am 24.01.2022 um 19:12 schrieb Scott Lurndal:
> 
>> https://www.theregister.com/2022/01/21/arm_morello_testing/
>> https://www.arm.com/architecture/cpu/morello
>> https://developer.arm.com/documentation/ddi0606/latest
> 
> Where are the 128 bit pointers in Morello ?

A quick skim implies that it works like:
   64-bit pointers, no special protection;
   129-bit pointers (with 128-bit storage), capability addressing, ...

So, implicitly, it involves:
Extra big pointers;
Extra wonkiness for saving/reloading pointers;
Registers that are internally significantly wider than what it visible 
in the rest of the ISA;
...

A quick skim makes me suspect that this will have few drawbacks:
More expensive for a hardware implementation (vs normal ARM64);
Unlikely to be widely adopted, as using it would adversely impact 
existing C codebases (which tend to assume pointers are either 32 or 64 
bits, and the ability to freely cast to and from integer types and 
manipulate them at the bit level, ...).


Ideally, one would want a solution which is both "pretty much invisible" 
(code should not need to know or care) and "nearly free" (does not 
significantly impact performance, memory usage, or the relative 
implementation cost).

...

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Thread

Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-24 18:12 +0000
  Re: Here come the 128-bit pointers Dan Purgert <dan@djph.net> - 2022-01-24 18:31 +0000
  Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-24 15:41 -0600
  Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-25 08:25 +0100
    Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-25 02:31 -0600
      Re: Here come the 128-bit pointers Öö Tiib <ootiib@hot.ee> - 2022-01-25 02:04 -0800
        Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-25 14:48 +0000
        Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-25 11:54 -0600
          Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-25 18:23 +0000
            Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-25 14:17 -0600
          Re: Here come the 128-bit pointers David Brown <david.brown@hesbynett.no> - 2022-01-26 09:36 +0100
            Re: Here come the 128-bit pointers Theo <theom+news@chiark.greenend.org.uk> - 2022-01-28 22:12 +0000
      Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-25 19:49 +0100
        Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-25 15:59 -0600
          Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-25 22:25 +0000
          Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-26 09:43 +0100
            Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 15:53 +0000
              Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-26 17:25 +0100
            Re: Here come the 128-bit pointers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-26 08:34 -0800
              Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-26 17:57 +0100
              Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-26 17:10 +0000
                Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 17:27 +0000
                Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-26 17:41 +0000
                Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 18:05 +0000
                Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-26 18:23 +0000
                Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-26 14:42 -0600
                Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-26 14:30 -0600
              Re: Here come the 128-bit pointers Mateusz Viste <mateusz@xyz.invalid> - 2022-01-26 19:36 +0100
                Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 18:52 +0000
            Re: Here come the 128-bit pointers tth <tth@none.invalid> - 2022-01-26 21:01 +0100
            Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-26 20:18 +0000
              Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-26 15:35 -0600
                Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 21:50 +0000
                Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-26 20:34 -0600
                Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-27 12:11 +0000
                Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-27 13:40 -0600
        Re: Here come the 128-bit pointers William Ahern <william@25thandClement.com> - 2022-01-27 13:28 -0800
  Re: Here come the 128-bit pointers Theo Markettos <theom+news@chiark.greenend.org.uk> - 2022-01-28 23:18 +0000

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