[PATCH] D109111: [CSSPGO] Use preinliner decision by default when available

[Wenlei He via Phabricator via llvm-commits]

wenlei added inline comments.


================
Comment at: llvm/lib/Transforms/IPO/SampleProfile.cpp:1314
+  if (UsePreInlinerDecision &&
+      Candidate.CalleeSamples->getContext().hasAttribute(
+          ContextShouldBeInlined))
----------------
hoy wrote:
> wenlei wrote:
> > hoy wrote:
> > > wenlei wrote:
> > > > hoy wrote:
> > > > > wenlei wrote:
> > > > > > hoy wrote:
> > > > > > > Will non-inlined context be merged into the base profile by the preinliner? Wondering if we can have contexts without `ContextShouldBeInlined` in the profile after processed by the preinliner.
> > > > > > Not inlined context will all be merged currently. See the comment I added above.
> > > > > So we'll not see the context profile here? Can such context only be seen when the preinliner is off?
> > > > Correct. When preinliner is on in llvm-profgen, we will only see context profile if preinliner decides to inline. When preinliner is off, we will see all context profiles. 
> > > Thanks for the confirmation. Can you update the comment to reflect that?
> > The comment mentions that:
> > 
> > > Note that we don't need to handle negative decision from preinliner as context profile for not inlined calls are merged by preinliner already.
> Oh, I actually meant to say there shouldn't be a negative decision from preinliner, since `Candidate.CalleeSamples` would be null in that case. I might misunderstand your comment.
> I actually meant to say there shouldn't be a negative decision from preinliner, since Candidate.CalleeSamples would be null in that case.

By decision from preinliner, it literally means inline decision made by preinliner in llvm-profgen. Preinliner would reject inlining for some calls, and these are the negative decision from preinliner. 

Candidate.CalleeSamples will never be null. If preinliner makes a negative inline decision, the corresponding context profile won't exist, and we won't see the callee as inline candidate (see getInlineCandidate). That's why we don't need to handle negative decisions explicitly.


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  https://reviews.llvm.org/D109111/new/

https://reviews.llvm.org/D109111