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

[Luke Lau via llvm-commits]

https://github.com/lukel97 updated https://github.com/llvm/llvm-project/pull/131336

>From 9241f0a64bcc1c392eb17c3510ab95b6759ee7c7 Mon Sep 17 00:00:00 2001
From: Luke Lau <luke at igalia.com>
Date: Fri, 14 Mar 2025 21:53:59 +0800
Subject: [PATCH 1/2] [VPlan] Remove createReduction. NFCI

This is split off from #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.
---
 .../include/llvm/Transforms/Utils/LoopUtils.h |  5 -----
 llvm/lib/Transforms/Utils/LoopUtils.cpp       | 18 ------------------
 .../lib/Transforms/Vectorize/VPlanRecipes.cpp | 19 ++++++++++++++++---
 3 files changed, 16 insertions(+), 26 deletions(-)

diff --git a/llvm/include/llvm/Transforms/Utils/LoopUtils.h b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
index 8f4c0c88336ac..1818ee03d2ec8 100644
--- a/llvm/include/llvm/Transforms/Utils/LoopUtils.h
+++ b/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,
diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 84c08556f8a25..7aea385c74b86 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -1345,24 +1345,6 @@ 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) {
diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index 6e396eda6aac6..d00e2a6e84908 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -666,8 +666,21 @@ 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())
@@ -2297,7 +2310,7 @@ 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);

>From 4067d4d1161f606f2871dc1fa93da46d55d423a3 Mon Sep 17 00:00:00 2001
From: Luke Lau <luke at igalia.com>
Date: Mon, 17 Mar 2025 18:54:29 +0800
Subject: [PATCH 2/2] Strengthen assertion in createSimpleReduction

---
 llvm/lib/Transforms/Utils/LoopUtils.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 7aea385c74b86..185af8631454a 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ 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();