Re: Memory ordering

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.