[llvm] [X86][CostModel] Cost gathers by the instructions CodeGen emits (PR #220565)

[Sumukh J Bharadwaj via llvm-commits]

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@@ -6649,34 +6657,29 @@ InstructionCost X86TTIImpl::getGSVectorCost(unsigned Opcode,
 
   // Trying to reduce IndexSize to 32 bits for vector 16.
   // By default the IndexSize is equal to pointer size.
-  unsigned IndexSize = (ST->hasAVX512() && VF >= 16)
-                           ? getIndexSizeInBits(Ptr, DL)
-                           : DL.getPointerSizeInBits();
+  unsigned IndexSize =
+      (ST->hasAVX512() && VF >= 16) ? getIndexSizeInBits(Ptr) : PtrSizeInBits;
 
   auto *IndexVTy = FixedVectorType::get(
       IntegerType::get(SrcVTy->getContext(), IndexSize), VF);
   std::pair<InstructionCost, MVT> IdxsLT = getTypeLegalizationCost(IndexVTy);
   std::pair<InstructionCost, MVT> SrcLT = getTypeLegalizationCost(SrcVTy);
   InstructionCost::CostType SplitFactor =
       std::max(IdxsLT.first, SrcLT.first).getValue();
-  if (SplitFactor > 1) {
-    // Handle splitting of vector of pointers
-    auto *SplitSrcTy =
-        FixedVectorType::get(SrcVTy->getScalarType(), VF / SplitFactor);
-    return SplitFactor * getGSVectorCost(Opcode, CostKind, SplitSrcTy, Ptr,
-                                         Alignment, AddressSpace);
-  }
-
-  // If we didn't split, this will be a single gather/scatter instruction.
+  // A vector of pointers that does not fit one register is split into
+  // SplitFactor gather/scatter instructions, each paying the overhead.
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amd-subharad wrote:

Agreed, this has been accounted into now

https://github.com/llvm/llvm-project/pull/220565