AW: [std-proposals] D3666R0 Bit-precise integers

The argument was that it could be used to represent specialized registers, it can't. Why are we still beating this dead horse?

From: Std-Proposals <std-proposals-bounces@lists.isocpp.org> on behalf of Sebastian Wittmeier via Std-Proposals <std-proposals@lists.isocpp.org>
Sent: Friday, September 5, 2025 1:05:01 PM
To: std-proposals@lists.isocpp.org <std-proposals@lists.isocpp.org>
Cc: Sebastian Wittmeier <wittmeier@projectalpha.org>
Subject: Re: [std-proposals] D3666R0 Bit-precise integers

Nobody (?) said it has to be done with a single store/load.

384 bits are 3x16 bytes.

-----Ursprüngliche Nachricht-----
Von: Tiago Freire via Std-Proposals <std-proposals@lists.isocpp.org>
Gesendet: Fr 05.09.2025 11:34
Betreff: Re: [std-proposals] D3666R0 Bit-precise integers
An: David Brown <david.brown@hesbynett.no>; std-proposals@lists.isocpp.org;
CC: Tiago Freire <tmiguelf@hotmail.com>;

And yet you don't understand that in some CPUs store/loads cannot strut across cache lines.

This is something that a CPU may not have the circuitry to physically do.

From: David Brown <david.brown@hesbynett.no>
Sent: Friday, September 5, 2025 9:09:40 AM
To: Tiago Freire <tmiguelf@hotmail.com>; std-proposals@lists.isocpp.org <std-proposals@lists.isocpp.org>
Subject: Re: [std-proposals] D3666R0 Bit-precise integers

On 04/09/2025 17:18, Tiago Freire wrote:
> I've not made a mistake. I've not mixed up bits and bytes. Please show
> me a quote where that happened?

In a post on 04.09.2025 08:27 you wrote in a reply to Jan Schultke "I do
mean bytes, not bits". I took that to mean you saw you had been unclear
or mixed up about bytes and bits. After all, you had been talking about
the alignments of something you wrote as "64Byte" - it was not at all
clear if you were talking about the alignment of a 64-bit type (which is
what everyone else was talking about, including the C23 standards), or
some kind of 64 /byte/ alignment (which would clearly be absurd at the
level of programming languages and/or ABIs).

I apologise if I misinterpreted you there.

>
> I don't know why you are trying to gaslight.

I am not doing that at all. I am merely frustrated in this conversation.

>
> If you don't know how CPU's work just say you don't know how it works!

I have studied the architecture of perhaps 20 or more processor designs,
from 4-bit to 64-bit and a few odd ones in-between, and written serious
assembly-level programs on most of them. The field of processor
architecture is vast, and there is a vast amount I don't know, but I
/do/ know how they work.

I also - and this is the key point - understand the difference between a
high-level programming language and its specification, and particular
implementations that might be used with it. I'm sure you have at least
a reasonable understanding of how cpus work too - but I am very sure you
don't understand the separation of programming language design and
implementation. You have to understand that distinction if you are
going to understand why _BitInt can be a useful (albeit fairly niche)
addition to C++, and why it will work both on "normal" processors and
specialist hardware. It will also help you understand why many of your
ideas are at odds with the other posters here who all want standard C++
to be improved as a programming language, rather than become some weird
hybrid assembly for a few chosen processors and your favourite assembly
instructions of the day. I sincerely hope you can understand this
distinction, and we can get back to discussions about C++ here.

It would probably be good if you didn't reply, at least not to this
mailing list. (My email address is david.brown@hesbynett.no, if you
feel further discussions would be helpful.)
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