[PATCH] D124769: [SLP] AdjustExtractsCost - remove redundant subvector extraction code

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: ABataev, Vasilis, reames.
Herald added subscribers: vporpo, hiraditya.
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RKSimon requested review of this revision.
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I noticed this while investigating replacing the getVectorInstrCost(Instruction::ExtractElement) calls with getScalarizationOverhead instead.

This code should be helping improve the costs of extracting an element from subvectors created during legalization, but removing it seems to have no effect - I'm guessing the getVectorInstrCost/getScalarizationOverhead improvements may have made it redundant?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D124769

Files:
  llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp


Index: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -5189,7 +5189,6 @@
   TargetTransformInfo &TTIRef = *TTI;
   auto &&AdjustExtractsCost = [this, &TTIRef, CostKind, VL, VecTy,
                                VectorizedVals, E](InstructionCost &Cost) {
-    DenseMap<Value *, int> ExtractVectorsTys;
     SmallPtrSet<Value *, 4> CheckedExtracts;
     for (auto *V : VL) {
       if (isa<UndefValue>(V))
@@ -5210,12 +5209,6 @@
       if (!EEIdx)
         continue;
       unsigned Idx = *EEIdx;
-      if (TTIRef.getNumberOfParts(VecTy) !=
-          TTIRef.getNumberOfParts(EE->getVectorOperandType())) {
-        auto It =
-            ExtractVectorsTys.try_emplace(EE->getVectorOperand(), Idx).first;
-        It->getSecond() = std::min<int>(It->second, Idx);
-      }
       // Take credit for instruction that will become dead.
       if (EE->hasOneUse()) {
         Instruction *Ext = EE->user_back();
@@ -5237,34 +5230,6 @@
       Cost -= TTIRef.getVectorInstrCost(Instruction::ExtractElement,
                                         EE->getVectorOperandType(), Idx);
     }
-    // Add a cost for subvector extracts/inserts if required.
-    for (const auto &Data : ExtractVectorsTys) {
-      auto *EEVTy = cast<FixedVectorType>(Data.first->getType());
-      unsigned NumElts = VecTy->getNumElements();
-      if (Data.second % NumElts == 0)
-        continue;
-      if (TTIRef.getNumberOfParts(EEVTy) > TTIRef.getNumberOfParts(VecTy)) {
-        unsigned Idx = (Data.second / NumElts) * NumElts;
-        unsigned EENumElts = EEVTy->getNumElements();
-        if (Idx + NumElts <= EENumElts) {
-          Cost +=
-              TTIRef.getShuffleCost(TargetTransformInfo::SK_ExtractSubvector,
-                                    EEVTy, None, Idx, VecTy);
-        } else {
-          // Need to round up the subvector type vectorization factor to avoid a
-          // crash in cost model functions. Make SubVT so that Idx + VF of SubVT
-          // <= EENumElts.
-          auto *SubVT =
-              FixedVectorType::get(VecTy->getElementType(), EENumElts - Idx);
-          Cost +=
-              TTIRef.getShuffleCost(TargetTransformInfo::SK_ExtractSubvector,
-                                    EEVTy, None, Idx, SubVT);
-        }
-      } else {
-        Cost += TTIRef.getShuffleCost(TargetTransformInfo::SK_InsertSubvector,
-                                      VecTy, None, 0, EEVTy);
-      }
-    }
   };
   if (E->State == TreeEntry::NeedToGather) {
     if (allConstant(VL))


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