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

[Mel Chen via llvm-commits]

================
@@ -1652,6 +1694,29 @@ void VPReductionRecipe::print(raw_ostream &O, const Twine &Indent,
     O << " (with final reduction value stored in invariant address sank "
          "outside of loop)";
 }
+
+void VPReductionEVLRecipe::print(raw_ostream &O, const Twine &Indent,
+                                 VPSlotTracker &SlotTracker) const {
+  O << Indent << "REDUCE ";
----------------
Mel-Chen wrote:

Following from other EVL recipes, vp.reduce is already there in the printing of reduction operation.
```
O << " vp.reduce." << Instruction::getOpcodeName(RdxDesc.getOpcode()) << " (";
```

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