[PATCH] D96803: EntryExitInstrumenter: Move to a module pass and enable at all optimization levels (PR49143)

[Arthur Eubanks via Phabricator via llvm-commits]

aeubanks added a comment.

In D96803#2571316 <https://reviews.llvm.org/D96803#2571316>, @zatrazz wrote:

> In D96803#2569436 <https://reviews.llvm.org/D96803#2569436>, @aeubanks wrote:
>
>> In D96803#2568179 <https://reviews.llvm.org/D96803#2568179>, @zatrazz wrote:
>>
>>> In D96803#2566322 <https://reviews.llvm.org/D96803#2566322>, @aeubanks wrote:
>>>
>>>> why is this now a module pass?
>>>
>>> Mainly to avoid the default rule from new pass manager to *not* apply any FunctionPass for optnone (which is the main issue for PR49143). Is there a better way to accomplish it? I noted also that createModuleToFunctionPassAdaptor basically creates a adaptor that applies the pass to all function on the module.
>>
>> It's always good to make the pass as specific as possible (e.g. prefer a function pass rather than a module pass) so it doesn't have to worry about infra. For example, just iterating over functions doesn't skip declarations.
>
> I modeled it after AlwaysInlinerPass, since it seems that it was enabled at -O0 as well.

AlwaysInlinerPass is a module pass because it does interprocedural changes. EntryExitInstrumenterPass works on one function at a time, which should be modeled as a function pass.

> To keep EntryExitInstrumenterPass a function pass and enable it with -O0 I think we will need a way to communicate to the pass manager that the pass should be run even with optnone, my understanding was that a ModulePass will the way to do it. Do we have a way to advertise that a function pass should be run regardless of ' optnone' ?

That's what `isRequired()` is for...

Basically we need two changes. One is add `isRequired()` to EntryExitInstrumenterPass, the other is to run EntryExitInstrumenterPass under -O0 as well by removing the check in BackendUtil.cpp (or by changing it to `CodeGenOpts.InstrumentFunctions || ...` as you've done). Please keep the pass as a function pass.


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