[PATCH] D79452: [VectorCombine] scalarize binop of inserted elements into undef

[Roman Lebedev via Phabricator via llvm-commits]

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

Seems fairly uncontroversial to me.



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Comment at: llvm/lib/Transforms/Vectorize/VectorCombine.cpp:320
+  Value *V0, *V1;
+  uint64_t Index;
+  if (!match(Ins0, m_OneUse(m_InsertElement(m_Undef(), m_Value(V0),
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Hm, do we have an interface to ask for cost of `InsertElement` with variable insert index?


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Comment at: llvm/lib/Transforms/Vectorize/VectorCombine.cpp:340-341
+  int OldCost = InsertCost + InsertCost + VectorOpCost;
+  int NewCost = ScalarOpCost + InsertCost;
+  if (OldCost < NewCost)
+    return false;
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`// We want to scalarize unless vector variant actually has lower cost`


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Comment at: llvm/lib/Transforms/Vectorize/VectorCombine.cpp:357
+  Value *Insert =
+      Builder.CreateInsertElement(UndefValue::get(VecTy), ScalarBO, Index);
+  I.replaceAllUsesWith(Insert);
----------------
This should retain the name from `I`.


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  https://reviews.llvm.org/D79452/new/

https://reviews.llvm.org/D79452