[llvm-dev] [RFC] llvm-exegesis: Automatic Measurement of Instruction Latency/Uops

[Eric Christopher via llvm-dev]

I am, of course, a huge fan of this effort. :)

>
>>
>>    -
>>
>>    [??] Make the tool work for other CPUs. This mainly depends on the
>>    presence of performance counters.
>>
>> Having these requirements documented will be great. In particular, it's
important to document what kind of functionality we need out of the PMU
rather than any particular cpu specific counter. Also performance
requirements of the counters.


Open Questions We depend on libpfm
>> <http://perfmon2.sourceforge.net/docs_v4.html>. How do we handle the
>> dependency ?
>>
>>
>> Are there options that you have in mind? It's an external MIT-licensed
>> dependency. Wouldn't CMake just detect it when it's available?
>>
>
> That's what we've done for now (see code here
> <https://reviews.llvm.org/differential/changeset/?ref=1002469&whitespace=ignore-most>).
> We're not sure what the policy is wrt external deps. Right now if the tool
> is enabled and libpfm is not on the system, we die with an error message.
> The other options would be to disable the tool in that case (I'm not sure
> how to do that). Opinions ?
>
>
> Sounds good (we can discuss this further, if necessary, in the code
> review).
>

Agreed. :)

-eric
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