[VPlan] Remove dead AnyOf reduction case in VPReductionRecipe. NFCI (#130048)

From what I understand, we only create VPReductionRecipes for in-loop
reductions, and we don't currently support in-loop AnyOf reductions.

We only create VPReductionRecipes in the !PhiR->isInLoop() section of
adjustRecipesForReductions, and this comment from the initial patch
seems to confirm this
https://reviews.llvm.org/D108136#anchor-inline-1038338, so I think we
can remove this check in the condition logic.

I checked compiling SPEC 2017 with -prefer-inloop-predicates and the
added assertion doesn't trigger.

Author: lukel97

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -2222,6 +2222,8 @@ void VPReductionRecipe::execute(VPTransformState &State) {
   assert(!State.Lane && "Reduction being replicated.");
   Value *PrevInChain = State.get(getChainOp(), /*IsScalar*/ true);
   RecurKind Kind = RdxDesc.getRecurrenceKind();
+  assert(!RecurrenceDescriptor::isAnyOfRecurrenceKind(Kind) &&
+         "In-loop AnyOf reductions aren't currently supported");
   // Propagate the fast-math flags carried by the underlying instruction.
   IRBuilderBase::FastMathFlagGuard FMFGuard(State.Builder);
   State.Builder.setFastMathFlags(RdxDesc.getFastMathFlags());
@@ -2232,12 +2234,8 @@ void VPReductionRecipe::execute(VPTransformState &State) {
     VectorType *VecTy = dyn_cast<VectorType>(NewVecOp->getType());
     Type *ElementTy = VecTy ? VecTy->getElementType() : NewVecOp->getType();
 
-    Value *Start;
-    if (RecurrenceDescriptor::isAnyOfRecurrenceKind(Kind))
-      Start = RdxDesc.getRecurrenceStartValue();
-    else
-      Start = llvm::getRecurrenceIdentity(Kind, ElementTy,
-                                          RdxDesc.getFastMathFlags());
+    Value *Start =
+        getRecurrenceIdentity(Kind, ElementTy, RdxDesc.getFastMathFlags());
     if (State.VF.isVector())
       Start = State.Builder.CreateVectorSplat(VecTy->getElementCount(), Start);