[llvm-dev] Where does doInitialization() fit into the new PassManager model?

[Arthur Eubanks via llvm-dev]

I'm not super familiar with the contracts of the legacy PM so I can't speak
to doInit/doFinalization. Not sure if there would be any caching issues
with modifying IR in doFinalization.

And yes this isn't really a thing in the new PM. Some passes have a module
pass version which does global things and then a function pass version that
runs things on each function.

On Thu, Nov 11, 2021 at 6:54 AM Zhang <admin at mayuyu.io> wrote:

> Hi Arthur:
> Thanks for the hint about RNG. While we are at it, one more thing the
> documentation is a bit vague about is that:
> Can I insert GVs into the Module in doFinalization()? I know you could do
> so in doInit(). The reason I'm asking this is that so I could implement my
> passes as FunctionPass if this holds.
>
> And again, where does this sort of behavior fits into the new PM? I assume
> it's also not considered?
>
> Zhang
>
>
> ------------------ Original ------------------
> *From: * "Arthur Eubanks"<aeubanks at google.com>;
> *Date: * Wed, Nov 10, 2021 02:10 AM
> *To: * "Zhang"<admin at mayuyu.io>;
> *Cc: * "llvm-dev"<llvm-dev at lists.llvm.org>;
> *Subject: * Re: [llvm-dev] Where does doInitialization() fit into the new
> PassManager model?
>
> Yeah there's currently no equivalent of doInitialization() in the new pass
> manager. Creating a per-module RNG to work on functions seems a bit weird
> to me. Module::createRNG() attempts to be consistent based on the module
> name + a per-call site salt, but that makes so changes in one function
> affect functions visited after. It would make more sense to me to use a
> per-function RNG salted with the module name and function name. Or if you
> really want a per-module RNG you could just lazily initialize it in the
> run(Function &). (Also Module::createRNG() isn't used in tree AFAICT)
>
> On Mon, Nov 8, 2021 at 7:59 PM Zhang via llvm-dev <llvm-dev at lists.llvm.org>
> wrote:
>
>> Hi:
>> In my legacy pass, I usually use doInitialization() to call
>> Module::createRNG() to create a RandomNumberGenerator, which my
>> FunctionPass later uses.
>> How does this model fit into the new PassManager interface? Creating my
>> new pass as run(Function&F ....) and re-create my RNG each time doesn't
>> preserve its internal state, but using run(Module& M) seems a bit overkill
>> to me?
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>
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