[cfe-dev] [RFC] C++17 hardware constructive / destructive interference size

[JF Bastien via cfe-dev]

> On May 25, 2018, at 11:38 AM, Friedman, Eli <efriedma at codeaurora.org> wrote:
> 
> On 5/25/2018 11:29 AM, JF Bastien via cfe-dev wrote:
>> Teach the target infrastructure that hardware interference size is something they can specify (in tablegen files somewhere).
>> Allow overriding the value in sub-targets using -march or -mcpu (the sub-target defines the numeric value, and the user gets the overriden one by using -march or -mcpu).
> 
> We can't change the value based on -mcpu.  We generally allow mixing code built with different values of -mcpu.  And any code which is linked together must use the same value for hardware_destructive_interference_size, or else we violate ODR.

Interesting point. The case I’d like to cover is one where the developer wants to get the exact right value for their particular CPU, instead of a conservative answer with extra padding. How do you think we should meet this use case?


> -Eli
> -- 
> Employee of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

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