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From: "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups: comp.arch
Subject: Re: Memory ordering
Date: Thu, 19 Dec 2024 21:08:19 -0800
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On 12/5/2024 7:19 AM, Tim Rentsch wrote:
> scott@slp53.sl.home (Scott Lurndal) writes:
> 
>> mitchalsup@aol.com (MitchAlsup1) writes:
>>
>>> On Tue, 3 Dec 2024 13:59:18 +0000, jseigh wrote:
>>>
>>>> The compiler is allow to reorder code as long as it knows the
>>>> reordering can't be observed or detected.
>>>
>>> With exceptions enabled, this would allow for almost no code
>>> movement at all.
>>>
>>>>                                            If there are places
>>>> in the code it doesn't know this can't happen it won't optimize
>>>> across it, more or less.
>>>
>>> The problem is HOW to TELL the COMPILER that these memory references
>>> are "more special" than normal--when languages give few mechanisms.
>>
>> C and C++ have the 'volatile' keyword for this purpose.
> 
> A problem with using volatile is that volatile doesn't do what
> most people think it does, especially with respect to what
> reordering is or is not allowed.

Ditto.