[PATCH] D102404: [InstCombine] Add instcombine fold for extractelement + splat for scalable vectors

[Caroline via Phabricator via llvm-commits]

CarolineConcatto added a comment.

Thank you @sdesmalen for you review.
I have made the changes you've asked.



================
Comment at: llvm/lib/Analysis/InstructionSimplify.cpp:4499-4502
+    if (auto *SE = dyn_cast<ShuffleVectorInst>(Vec))
+      if (isSplatValue(SE) && IdxC->getValue().ult(NumElts))
+        if (auto *IE = dyn_cast<InsertElementInst>(SE->getOperand(0)))
+          return IE->getOperand(1);
----------------
sdesmalen wrote:
> Why not just rely on `llvm::getSplatValue` here?
> 
>   unsigned MinNumElts = VecVTy->getElementCount().getKnownMinValue();
>   if (IdxC->getValue().ult(NumElts))
>     if (auto *Splat = getSplatValue(Vec))
>       return Splat;
> 
>   
Yes, it could check for Splat.
I  like the other way because it explains/shows the instruction chain.
But your solution is cleaner, so I have changed.



Repository:
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  https://reviews.llvm.org/D102404/new/

https://reviews.llvm.org/D102404