[llvm-dev] SROA and volatile memcpy/memset

[Krzysztof Parzyszek via llvm-dev]

On 11/11/2015 9:40 AM, Chandler Carruth wrote:
> I'm pretty sure volatile access voids your performance warranty....
>
> I assume the issue is that the loads and stores aren't combined late in
> the back end because we propagate the volatile? I think the fix for
> performance is "don't use volatile". I'm sure you've looked at that
> option, but we'll need a lot more context on what problem you're
> actually hitting to provide more realistic options.

The testcase is a synthetic scenario that a customer gave us.  I don't 
have much more insight into it than what I can get by just looking at 
it.  I can try to find out more about the origin of it.


> I think TTI is a very bad fit here -- target customization would really
> hurt the entire canonicalization efforts of the middle end....

I see. Hmm.

-Krzysztof

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