[llvm-dev] SROA and volatile memcpy/memset

[Krzysztof Parzyszek via llvm-dev]

On 11/11/2015 9:36 AM, Hal Finkel wrote:
> ----- Original Message -----
>> From: "Krzysztof Parzyszek" <kparzysz at codeaurora.org>
>>
>> Yeah, the remark about devices I made in my post was a result of a
>> "last-minute" thought to add some rationale.  It doesn't actually
>> apply
>> to SROA, since there are no devices that are mapped to the stack,
>> which
>> is what SROA is interested in.
>>
>> The concern with the testcase I attached is really about performance.
>> Would it be reasonable to control the splitting in SROA via TTI?
>
> How so?

I'm not sure which part you are referring to.  The "volatileness" of the 
structure in question does not place the same restrictions on how we can 
access it as it would be in the case of a device access.  The broken up 
loads and stores are legal in the sense that they won't cause any 
hardware issues, however they would take longer to execute because the 
resulting instructions would be marked as volatile and thus 
"non-optimizable".

-Krzysztof

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, 
hosted by The Linux Foundation