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Re: Optimization of conditional access to globals: thread-unsafe?


From: Michael Matz <matz@suse.de>
Date: Fri, 26 Oct 2007 19:04:10 +0200 (CEST)

> Certainly some suggestions for another memory model look quite
> similar to considering all non-automatic objects as volatile, at
> which point the question should be allowed why not simply using
> 'volatile'.

This is very much not true.

You can speculatively load these global variables as much as you like,
you just can't unconditionally store to them.

Volatile is a much different beast.

Also, it bears repeating that whatever performance argument you make
for or against this issue matters little if it breaks lots of existing
and working code.  It is also important to remind people that paper
standards count less than common sense and what effects users on a
practical level, even when those paper standards allow your favorite
optimization or transformation.

I think some people in this discussion too often use paper standards
as a crutch in their arguments.


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