[llvm] [LV][EVL] Support in-loop reduction using tail folding with EVL. (PR #90184)

[Mel Chen via llvm-commits]

================
@@ -57,6 +58,11 @@ class VectorBuilder {
     return RetType();
   }
 
+  // Helper function for creating VP intrinsic call.
----------------
Mel-Chen wrote:

> or `VPBuilder`, like there's `IRBuilder`

That's unfortunate, as there is already a class named `VPBuilder` in LoopVectorizationPlanner.h.
```
/// VPlan-based builder utility analogous to IRBuilder.
class VPBuilder {
  VPBasicBlock *BB = nullptr;
```


https://github.com/llvm/llvm-project/pull/90184