[llvm] [SLP][NFC]Remove handling of duplicates from getGatherCost (PR #135834)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Alexey Bataev (alexey-bataev)

<details>
<summary>Changes</summary>

Duplicates are handled in BoUpSLP::processBuildVector (see TryPackScalars), support for duplicates in getGatherCost is not needed anymore.


---
Full diff: https://github.com/llvm/llvm-project/pull/135834.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp (+2-32) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index cc775e4b260dc..3363d4056b300 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -15349,13 +15349,10 @@ InstructionCost BoUpSLP::getGatherCost(ArrayRef<Value *> VL, bool ForPoisonSrc,
                                        Type *ScalarTy) const {
   const unsigned VF = VL.size();
   auto *VecTy = getWidenedType(ScalarTy, VF);
-  bool DuplicateNonConst = false;
   // Find the cost of inserting/extracting values from the vector.
   // Check if the same elements are inserted several times and count them as
   // shuffle candidates.
-  APInt ShuffledElements = APInt::getZero(VF);
   APInt DemandedElements = APInt::getZero(VF);
-  DenseMap<Value *, unsigned> UniqueElements;
   constexpr TTI::TargetCostKind CostKind = TTI::TCK_RecipThroughput;
   InstructionCost Cost;
   auto EstimateInsertCost = [&](unsigned I, Value *V) {
@@ -15364,32 +15361,18 @@ InstructionCost BoUpSLP::getGatherCost(ArrayRef<Value *> VL, bool ForPoisonSrc,
       Cost += TTI->getCastInstrCost(Instruction::Trunc, ScalarTy, V->getType(),
                                     TTI::CastContextHint::None, CostKind);
   };
-  SmallVector<int> ShuffleMask(VF, PoisonMaskElem);
   SmallVector<int> ConstantShuffleMask(VF, PoisonMaskElem);
   std::iota(ConstantShuffleMask.begin(), ConstantShuffleMask.end(), 0);
   for (auto [I, V] : enumerate(VL)) {
     // No need to shuffle duplicates for constants.
-    if ((ForPoisonSrc && isConstant(V)) || isa<UndefValue>(V)) {
-      ShuffledElements.setBit(I);
-      ShuffleMask[I] = isa<PoisonValue>(V) ? PoisonMaskElem : I;
+    if ((ForPoisonSrc && isConstant(V)) || isa<UndefValue>(V))
       continue;
-    }
 
     if (isConstant(V)) {
       ConstantShuffleMask[I] = I + VF;
-      ShuffleMask[I] = I;
-      continue;
-    }
-    auto Res = UniqueElements.try_emplace(V, I);
-    if (Res.second) {
-      EstimateInsertCost(I, V);
-      ShuffleMask[I] = I;
       continue;
     }
-
-    DuplicateNonConst = true;
-    ShuffledElements.setBit(I);
-    ShuffleMask[I] = Res.first->second;
+    EstimateInsertCost(I, V);
   }
   // FIXME: add a cost for constant vector materialization.
   bool IsAnyNonUndefConst =
@@ -15398,15 +15381,6 @@ InstructionCost BoUpSLP::getGatherCost(ArrayRef<Value *> VL, bool ForPoisonSrc,
   if (!ForPoisonSrc && IsAnyNonUndefConst) {
     Cost += ::getShuffleCost(*TTI, TargetTransformInfo::SK_PermuteTwoSrc, VecTy,
                              ConstantShuffleMask);
-    // Update the shuffle mask for shuffling with incoming source (all elements
-    // are used!) or with constant subvector.
-    for_each(enumerate(ShuffleMask), [&](auto P) {
-      if ((!ForPoisonSrc && P.value() == PoisonMaskElem) ||
-          ConstantShuffleMask[P.index()] != PoisonMaskElem)
-        P.value() = P.index();
-      else if (P.value() != PoisonMaskElem)
-        P.value() += VF;
-    });
   }
 
   // 2. Insert unique non-constants.
@@ -15415,10 +15389,6 @@ InstructionCost BoUpSLP::getGatherCost(ArrayRef<Value *> VL, bool ForPoisonSrc,
                                      /*Insert=*/true,
                                      /*Extract=*/false, CostKind,
                                      ForPoisonSrc && !IsAnyNonUndefConst, VL);
-  // 3. Shuffle duplicates.
-  if (DuplicateNonConst)
-    Cost += ::getShuffleCost(*TTI, TargetTransformInfo::SK_PermuteSingleSrc,
-                             VecTy, ShuffleMask, CostKind);
   return Cost;
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/135834