[llvm-dev] OptBisect implementation for new pass manager

[Fedor Sergeev via llvm-dev]

On 10/02/2018 01:37 AM, paul.robinson at sony.com wrote:
>> And that is the most tricky part - how does pass know that a particular
>> pass *invocation*
>> runs in 'skip' mode?
>>
>> It appears that the only "proper" way for passes to get "outside"
>> information is to ask for the analysis.
>> So we need special analysis deployed by OptBisect object that tells
>> those tricky passes like
>> scheduler that they need to run in 'skip' mode.
> There's a sort of architectural purity to this, but to make it properly
> pervasive it would want to be very little work on the pass author's part
> to query and act on it.
Majority of passes do not need to worry about it, since they are just run,
not trying to determine its optimization mode through a dark magic 
interaction
with OptBisect. As soon as they get run they "just run".
Thus I dont really worry about this being very little work for passes.

regards,
   Fedor.

>    At which point we are basically doing the same
> helper-in-base-class deal that we have now.  Maybe making it into an
> always-available analysis is helpful or simpler, I don't know, I don't
> do passes normally. :-)
> --paulr
>
>> regards,
>>     FEdor.
>>
>>>                                -David
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