[PATCH] D95982: [CSSPGO] Unblock optimizations with pseudo probe instrumentation.

[Wei Mi via Phabricator via llvm-commits]

wmi accepted this revision.
wmi added a comment.
This revision is now accepted and ready to land.

LGTM.



================
Comment at: llvm/lib/Transforms/IPO/FunctionAttrs.cpp:152-157
+      // A pseudo probe call shouldn't change any function attribute since it
+      // doesn't translate to a real instruction. It comes with a memory access
+      // tag to prevent itself being removed by optimizations and not block
+      // other instructions being optimized.
+      if (isa<PseudoProbeInst>(I))
+        continue;
----------------
hoy wrote:
> wmi wrote:
> > Make it a little more general?
> > 
> >   if (auto *CB = dyn_cast<CallBase>(I))
> >     if (CB->onlyAccessesInaccessibleMemory())
> >       continue;
> I think we might want to be a bit conservative here, since in theory `onlyAccessesInaccessibleMemory` still accesses memory. This may lead to
> 1. Functions with `onlyAccessesInaccessibleMemory`  calls may not be free to be removed.
> 2. Calls with `onlyAccessesInaccessibleMemory` may not be moved around across each other.
> 
> Pseudo probe don't have such effects thus checking against pseudo probes here should have minimal impact. What do you think?
> 
> 
Right. It is better to be conservative here. 


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https://reviews.llvm.org/D95982