spupyrev added a comment.

In D109531#2993394 <https://reviews.llvm.org/D109531#2993394>, @wmi wrote:

> In D109531#2992721 <https://reviews.llvm.org/D109531#2992721>, @hoy wrote:
>
>> In D109531#2992702 <https://reviews.llvm.org/D109531#2992702>, @wenlei wrote:
>>
>>> The change makes sense given instr PGO also happens for O0. But 
>>> practically, if a file is being built with O0, do we care about its profile 
>>> given we're not really optimizing it anyways? Functions from O0 modules are 
>>> not supposed to be inlined into O1 
>>> <https://reviews.llvm.org/owners/package/1/>+ modules either.
>>
>> We probably don't care about performance for O0 build. The change is for 
>> consistency, also makes the compiler happy which otherwise will complain 
>> about "Pseudo-probe-based profile requires SampleProfileProbePass" for O0 
>> modules that don't have probes.
>
> The complain message is emitted in SampleProfileLoader::doInitialization. 
> llvm will not run SampleProfileLoader pass for O0 module. Why there is the 
> complain?

We've encountered this exception while building an old version of gcc (8.3) 
with llvm-12. As Hongtao pointed out, they sometimes try to build targets with 
"-flto" but without "-O2/O3 <https://reviews.llvm.org/owners/package/3/>". 
Surely, the right "fix" would be to modify the gcc build scripts (which is 
possibly already done in later gcc releases); this workaround is to make sure 
we can also process "incorrect" builds.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D109531/new/

https://reviews.llvm.org/D109531

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