[llvm] [VPlan] Impl VPlan-based pattern match for ExtendedRed and MulAccRed (PR #113903)

[Florian Hahn via llvm-commits]

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@@ -782,19 +784,25 @@ Value *VPInstruction::generate(VPTransformState &State) {
 InstructionCost VPInstruction::computeCost(ElementCount VF,
                                            VPCostContext &Ctx) const {
   if (Instruction::isBinaryOp(getOpcode())) {
+
+    Type *ResTy = Ctx.Types.inferScalarType(this);
+    if (!vputils::onlyFirstLaneUsed(this))
+      ResTy = toVectorTy(ResTy, VF);
+
     if (!getUnderlyingValue()) {
-      // TODO: Compute cost for VPInstructions without underlying values once
-      // the legacy cost model has been retired.
-      return 0;
+      switch (getOpcode()) {
+      case Instruction::FMul:
+        return Ctx.TTI.getArithmeticInstrCost(getOpcode(), ResTy, Ctx.CostKind);
+      default:
+        // TODO: Compute cost for VPInstructions without underlying values once
+        // the legacy cost model has been retired.
+        return 0;
+      }
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fhahn wrote:

Are those changes here still needed in the latest version? I don't think we create FMul VPInstructions now?

https://github.com/llvm/llvm-project/pull/113903