[llvm] [VPlan] Replace ExtractLast(Elem|LanePerPart) with ExtractLast(Lane/Part) (PR #164124)

[via llvm-commits]

================
@@ -1330,11 +1326,8 @@ static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
     return Def->replaceAllUsesWith(A);
   }
 
-  if (Plan->getUF() == 1 &&
-      match(Def, m_ExtractLastLanePerPart(m_VPValue(A)))) {
-    return Def->replaceAllUsesWith(
-        Builder.createNaryOp(VPInstruction::ExtractLastElement, {A}));
-  }
+  if (Plan->getUF() == 1 && match(Def, m_ExtractLastPart(m_VPValue(A))))
+    return Def->replaceAllUsesWith(A);
----------------
ayalz wrote:

OK, it indeed affects ::execute, just seems natural to add the following here - analogous to bypassing redundant ExtractLastPart:
```
  if (Plan->hasScalarVFOnly() && match(Def, m_ExtractLastLane(m_VPValue(A))))
    return Def->replaceAllUsesWith(A);
```
or rather prevent its creation?

https://github.com/llvm/llvm-project/pull/164124