[llvm] [VPlan] Implement VPInterleaveRecipe::computeCost. (PR #106067)

[Renato Golin via llvm-commits]

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@@ -2627,6 +2625,37 @@ void VPInterleaveRecipe::execute(VPTransformState &State) {
   }
 }
 
+InstructionCost VPInterleaveRecipe::computeCost(ElementCount VF,
+                                                VPCostContext &Ctx) const {
+  Instruction *I = getInsertPos();
+  Type *ValTy = Ctx.Types.inferScalarType(
+      getNumDefinedValues() > 0 ? getVPValue(0) : getStoredValues()[0]);
+  auto *VectorTy = cast<VectorType>(ToVectorTy(ValTy, VF));
+  unsigned AS = getLoadStoreAddressSpace(I);
+  enum TTI::TargetCostKind CostKind = TTI::TCK_RecipThroughput;
+
+  unsigned InterleaveFactor = IG->getFactor();
+  auto *WideVecTy = VectorType::get(ValTy, VF * InterleaveFactor);
+
+  // Holds the indices of existing members in the interleaved group.
+  SmallVector<unsigned, 4> Indices;
+  for (unsigned IF = 0; IF < InterleaveFactor; IF++)
+    if (IG->getMember(IF))
+      Indices.push_back(IF);
+
+  // Calculate the cost of the whole interleaved group.
+  InstructionCost Cost = Ctx.TTI.getInterleavedMemoryOpCost(
+      I->getOpcode(), WideVecTy, IG->getFactor(), Indices, IG->getAlign(), AS,
+      CostKind, getMask(), NeedsMaskForGaps);
+
+  if (!IG->isReverse())
+    return Cost;
+
+  return Cost + IG->getNumMembers() *
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rengolin wrote:

This looks a bit hard-coded. It would be better to get the attribute from `IG` and pass it to `getShuffleCost`, but this can be done in a future PR.

https://github.com/llvm/llvm-project/pull/106067