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

[Benjamin Maxwell via llvm-commits]

================
@@ -4524,3 +4525,69 @@ void VPlanTransforms::addExitUsersForFirstOrderRecurrences(VPlan &Plan,
     }
   }
 }
+
+/// Change CSA reductions to save the appropriate state.
----------------
MacDue wrote:

nit: Define CSA here, may not be clear from context. It would also be good to have an example of this transform. 
```suggestion
/// Change conditional scalar assignment (CSA) reductions to save the appropriate state.
```

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