[llvm] [SampleFDO] Support enabling sample loader pass in O0 mode (PR #113985)

[Lei Wang via llvm-commits]

wlei-llvm wrote:

> > Should we flatten the profile first for O0 profile loading?
> 
> Is it done later for 'nonlined callee' ?

Yeah, if we disable the inlining, the `nonlined callee` profiles are promoted to the outline profile, would be reused.  But I once tried, this appears not equivalent to using a flattened profile directly(call `ProfileConverter::flattenProfile`) 

One my guess is, it could be different for a recursive function case.  The former depends on the function order, if a function has been processed, then later when it showed in an inlinee profile, even if it's promoted, but we won't run that function again. 

It's not the case for call `ProfileConverter::flattenProfile`, as it flattens the profile at the beginning.






https://github.com/llvm/llvm-project/pull/113985