[VPlan] Remove createReduction. NFCI (llvm#131336)

This is split off from llvm#131300.

A VPReductionRecipe will never have a AnyOf or FindLastIV recurrence, so
when it calls createReduction it always calls createSimpleReduction.

If we replace the call then it leaves createReduction with one user in
VPInstruction::ComputeReductionResult, which we can inline and then
remove.

Author: lukel97

llvm/include/llvm/Transforms/Utils/LoopUtils.h

@@ -427,11 +427,6 @@ Value *createAnyOfReduction(IRBuilderBase &B, Value *Src,
 Value *createFindLastIVReduction(IRBuilderBase &B, Value *Src,
                                  const RecurrenceDescriptor &Desc);
 
-/// Create a generic reduction using a recurrence descriptor \p Desc
-/// Fast-math-flags are propagated using the RecurrenceDescriptor.
-Value *createReduction(IRBuilderBase &B, const RecurrenceDescriptor &Desc,
-                       Value *Src, PHINode *OrigPhi = nullptr);
-
 /// Create an ordered reduction intrinsic using the given recurrence
 /// descriptor \p Desc.
 Value *createOrderedReduction(IRBuilderBase &B,

llvm/lib/Transforms/Utils/LoopUtils.cpp

@@ -1336,7 +1336,8 @@ Value *llvm::createSimpleReduction(VectorBuilder &VBuilder, Value *Src,
                                    const RecurrenceDescriptor &Desc) {
   RecurKind Kind = Desc.getRecurrenceKind();
   assert(!RecurrenceDescriptor::isAnyOfRecurrenceKind(Kind) &&
-         "AnyOf reduction is not supported.");
+         !RecurrenceDescriptor::isFindLastIVRecurrenceKind(Kind) &&
+         "AnyOf or FindLastIV reductions are not supported.");
   Intrinsic::ID Id = getReductionIntrinsicID(Kind);
   auto *SrcTy = cast<VectorType>(Src->getType());
   Type *SrcEltTy = SrcTy->getElementType();
@@ -1345,24 +1346,6 @@ Value *llvm::createSimpleReduction(VectorBuilder &VBuilder, Value *Src,
   return VBuilder.createSimpleReduction(Id, SrcTy, Ops);
 }
 
-Value *llvm::createReduction(IRBuilderBase &B,
-                             const RecurrenceDescriptor &Desc, Value *Src,
-                             PHINode *OrigPhi) {
-  // TODO: Support in-order reductions based on the recurrence descriptor.
-  // All ops in the reduction inherit fast-math-flags from the recurrence
-  // descriptor.
-  IRBuilderBase::FastMathFlagGuard FMFGuard(B);
-  B.setFastMathFlags(Desc.getFastMathFlags());
-
-  RecurKind RK = Desc.getRecurrenceKind();
-  if (RecurrenceDescriptor::isAnyOfRecurrenceKind(RK))
-    return createAnyOfReduction(B, Src, Desc, OrigPhi);
-  if (RecurrenceDescriptor::isFindLastIVRecurrenceKind(RK))
-    return createFindLastIVReduction(B, Src, Desc);
-
-  return createSimpleReduction(B, Src, RK);
-}
-
 Value *llvm::createOrderedReduction(IRBuilderBase &B,
                                     const RecurrenceDescriptor &Desc,
                                     Value *Src, Value *Start) {

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -672,8 +672,21 @@ Value *VPInstruction::generate(VPTransformState &State) {
          RecurrenceDescriptor::isAnyOfRecurrenceKind(RK) ||
          RecurrenceDescriptor::isFindLastIVRecurrenceKind(RK)) &&
         !PhiR->isInLoop()) {
-      ReducedPartRdx =
-          createReduction(Builder, RdxDesc, ReducedPartRdx, OrigPhi);
+      // TODO: Support in-order reductions based on the recurrence descriptor.
+      // All ops in the reduction inherit fast-math-flags from the recurrence
+      // descriptor.
+      IRBuilderBase::FastMathFlagGuard FMFG(Builder);
+      Builder.setFastMathFlags(RdxDesc.getFastMathFlags());
+
+      if (RecurrenceDescriptor::isAnyOfRecurrenceKind(RK))
+        ReducedPartRdx =
+            createAnyOfReduction(Builder, ReducedPartRdx, RdxDesc, OrigPhi);
+      else if (RecurrenceDescriptor::isFindLastIVRecurrenceKind(RK))
+        ReducedPartRdx =
+            createFindLastIVReduction(Builder, ReducedPartRdx, RdxDesc);
+      else
+        ReducedPartRdx = createSimpleReduction(Builder, ReducedPartRdx, RK);
+
       // If the reduction can be performed in a smaller type, we need to extend
       // the reduction to the wider type before we branch to the original loop.
       if (PhiTy != RdxDesc.getRecurrenceType())
@@ -2306,7 +2319,7 @@ void VPReductionRecipe::execute(VPTransformState &State) {
     NextInChain = NewRed;
   } else {
     PrevInChain = State.get(getChainOp(), /*IsScalar*/ true);
-    NewRed = createReduction(State.Builder, RdxDesc, NewVecOp);
+    NewRed = createSimpleReduction(State.Builder, NewVecOp, Kind);
     if (RecurrenceDescriptor::isMinMaxRecurrenceKind(Kind))
       NextInChain = createMinMaxOp(State.Builder, RdxDesc.getRecurrenceKind(),
                                    NewRed, PrevInChain);