Path: ...!feeds.phibee-telecom.net!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.arch
Subject: Re: bit addressing Byte Addressability And Beyond
Date: Thu, 2 May 2024 00:24:50 -0000 (UTC)
Organization: A noiseless patient Spider
Lines: 21
Message-ID: <v0umgh$3ekmk$5@dont-email.me>
References: <v0s17o$2okf4$2@dont-email.me> <v0s744$l3v$1@gal.iecc.com>
	<jwvcyq5qzxr.fsf-monnier+comp.arch@gnu.org> <v0tvi1$1n3a$1@gal.iecc.com>
	<jwv4jbhpf8n.fsf-monnier+comp.arch@gnu.org>
	<dd14d2b03b1a3c8825b0f712dcc566d7@www.novabbs.org>
	<v0u4ns$3b77p$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Injection-Date: Thu, 02 May 2024 02:24:50 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="871317f39d0297e5333fe0a9119501c9";
	logging-data="3625684"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+49ChRe+HVqW9TIrl0QE90"
User-Agent: Pan/0.155 (Kherson; fc5a80b8)
Cancel-Lock: sha1:AS7O5oZqMCqDKz/UKPsx6UxelKI=
Bytes: 2126

On Wed, 1 May 2024 19:21:32 -0000 (UTC), Stephen Fuld wrote:

> MitchAlsup1 wrote:
> 
>> ... looking at code one rarely sees a field in a struct that
>> is a bit-field. So, even if the cost was low, the benefits are
>> similarly low.
> 
> Sure.  But it isn't clear if that was the cause or the result of the
> hardware.

Absolutely, I would say that is very much a chicken-and-egg effect. Also, 
if you thought endian issues were complicated, look at how different 
architectures implement their bit-field instructions.

Interesting fact: in spite of all the arguments over big-endian versus 
little-endian, everybody seems to be in agreement over what “shift left” 
and “shift right” mean: “left” is always to the most significant end, 
while “right” is always to the least significant end. If you want to do 
bit packing/unpacking in endian-independent C code, you do it with shifts 
and masks.