[llvm] [SLP] Check for extracts, being replaced by original scalars, for user nodes (PR #149572)

[Gaëtan Bossu via llvm-commits]

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@@ -10700,6 +10801,15 @@ void BoUpSLP::buildTreeRec(ArrayRef<Value *> VLRef, unsigned Depth,
     return;
   }
 
+  // Postpone vectorization, if the node is not profitable because of the
+  // external uses.
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gbossu wrote:

Nit: "external uses" is a bit confusing, as we are looking at instructions in the tree, not outside of it. Maybe rephrase as `because of scalar uses`?

https://github.com/llvm/llvm-project/pull/149572