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Re: volatile access optimization (C++ / x86_64)


> On Dec 30, 2014, at 1:32 PM, Matt Godbolt <matt@godbolt.org> wrote:
> 
> On Tue, Dec 30, 2014 at 5:05 AM, Torvald Riegel <triegel@redhat.com> wrote:
>> I agree with Andrew.  My understanding of volatile is that the generated
>> code must do exactly what the abstract machine would do.
> 
> That makes sense. I suppose I don't understand what the difference is
> in terms of an abstract machine of "load; add; store" versus the
> "load-add-store". At least from on x86, from the perspective of the
> memory bus, there's no difference I'm aware of.

That was my point.  The model needs to treat those two as equivalent, otherwise the model is constructed by theories that I donât understand.

	paul


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