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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.arch
Subject: Re: Computer architects leaving Intel...
Date: Fri, 6 Sep 2024 09:17:45 +0200
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On 05/09/2024 23:39, Scott Lurndal wrote:
> Bernd Linsel <bl1-thispartdoesnotbelonghere@gmx.com> writes:
>> On 05.09.24 19:04, Terje Mathisen wrote:
>>> One of my alternatives are
>>>
>>>    unsigned u = start; // Cannot be less than zero
>>>    if (u) {
>>>       u++;
>>>       do {
>>>          u--;
>>>          data[u]...
>>>       while (u);
>>>     }
>>>
>>> This typically results in effectively the same asm code as the signed
>>> version, except for a bottom JGE (Jump (signed) Greater or Equal instead
>>> of JA (Jump Above or Equal, but my version is far more verbose.
>>>
>>> Alternatively, if you don't need all N bits of the unsigned type, then
>>> you can subtract and check if the top bit is set in the result:
>>>
>>>   %G�%@|  for (unsigned u = start; (u & TOPBIT) == 0; u--)
>>>
>>> Terje
>>>
>>
>> What about:
>>
>> for (unsigned u = start; u != ~0u; --u)
> 
> This is the form we use most when we need
> to work in reverse.
> 

In a code review, I would reject that - and all the other nonsenses 
suggested here as a way to force all loop indices to be unsigned types 
as though that rule was the 11th commandment.

Just write code that makes sense - it's /not/ hard in this case!

	for (int i = start; i >= 0; i--) ...

If you need the loop counter to be an unsigned type inside the loop 
code, make an unsigned version:

	for (int i = start; i >= 0; i--) {
		const unsigned int u = i;
		...
	}

Sometimes it amazes me the kind of nonsense people write in code because 
of obsession about particular rules.  Code clarity trumps /all/ 
stylistic rules.