[PATCH] D103988: SampleFDO] place the discriminator flag variable into the used list.

Tue Jun 15 17:01:17 PDT 2021

hoy added a comment.

In D103988#2820746 <https://reviews.llvm.org/D103988#2820746>, @xur wrote:

> In D103988#2820735 <https://reviews.llvm.org/D103988#2820735>, @MaskRay wrote:
>
>> CommonLinkage doesn't work.
>>
>> Whether `appendToUsed` is needed depends on whether the runtime has a live section referencing `__llvm_fs_discriminator__`.
>> If the runtime has the guarantee, no need for `appendToUsed`.
>>
>> Otherwise, the first revision `appendToUsed` with `WeakODRLinkage` looks good to me.
>>
>> `appendToUsed` with `ExternalLinkage` in a comdat works as well, but comdat will need extra code when Mach-O wants this feature.
>
> Fangri, thanks for reviewing this. This variable will NOT be referenced by compiler runtime library -- only be referenced by AutoFDO offline tool (to generate AFDO profile).
>
> It seems that Fangri (as a linker expert) prefers my first implementation.
>
> I'm OK either way. Hoy: what is your thought?

Sounds good to me. Didn't know that linker could GC common symbols. Sorry about that.

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https://reviews.llvm.org/D103988