[llvm] ValueTracking: introduce llvm::isNotCrossLaneOperation (PR #112011)

[Nikita Popov via llvm-commits]

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@@ -791,6 +791,10 @@ bool onlyUsedByLifetimeMarkers(const Value *V);
 /// droppable instructions.
 bool onlyUsedByLifetimeMarkersOrDroppableInsts(const Value *V);
 
+/// Return true if the instruction doesn't potentially cross vector lanes. This
+/// is useful to make GVN-replacements for vector types.
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nikic wrote:

```suggestion
/// is useful when optimizing based on vector conditions.
```
Though TBH I'd just leave off the second sentence, I don't think it is helpful without a significantly more detailed explanation.

https://github.com/llvm/llvm-project/pull/112011