[llvm] [LV] Vectorize conditional scalar assignments (PR #158088)

[Benjamin Maxwell via llvm-commits]

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@@ -1769,6 +1772,47 @@ struct LLVM_ABI_FOR_TEST VPWidenSelectRecipe : public VPRecipeWithIRFlags,
   }
 };
 
+/// A recipe for selecting whole vector values.
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MacDue wrote:

nit: I think this would be a little clearer if you spell out that the condition is scalar:
```suggestion
/// A recipe for selecting whole vector values based on a scalar condition.
```

https://github.com/llvm/llvm-project/pull/158088