[PATCH] D126533: [LAA] Relax pointer dependency with runtime pointer checks

[Dinar Temirbulatov via Phabricator via llvm-commits]

dtemirbulatov marked an inline comment as done.
dtemirbulatov added inline comments.


================
Comment at: llvm/lib/Analysis/LoopAccessAnalysis.cpp:1714-1715
+
+    if (APtr != BPtr && (SrcAffine || SinkAffine) &&
+        (SrcInvariant || SinkInvariant))
+      FoundNonConstantDistanceDependence = true;
----------------
dtemirbulatov wrote:
> fhahn wrote:
> > dtemirbulatov wrote:
> > > sdesmalen wrote:
> > > > This expression doesn't allow the case where `SrcAffine && SinkAffine && !SrcInvariant && !SinkInvariant`.
> > > > 
> > > > AIUI the distance can only be computed if:
> > > > 
> > > >   (SrcAffine && SinkAffine) ||
> > > >   (SrcAffine && SinkInvariant) ||
> > > >   (SrcInvariant && SinkAffine) ||
> > > >   (SrcInvariant && SinkInvariant)
> > > > 
> > > > By the way, I couldn't see any new test-cases. Did you forget to add these, or did I miss something?
> > > Hmm , For the case if both are invariants we don't need to emit a run-time check and I think we can ignore such cases. For both are affine type pointers I have not considered to support with the change and if I allow it I noticed performance regressions.
> > It would be good to have at least all those combinations covered in the unit tests. Do you have any insight in the cause for the performance regression. you are seeing?
> Added dedicated test.
just extra check instructions with a small number of iterations.


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https://reviews.llvm.org/D126533