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

[Florian Hahn via llvm-commits]

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@@ -2390,28 +2396,47 @@ InstructionCost VPReductionRecipe::computeCost(ElementCount VF,
   auto *VectorTy = cast<VectorType>(toVectorTy(ElementTy, VF));
   unsigned Opcode = RecurrenceDescriptor::getOpcode(RdxKind);
   FastMathFlags FMFs = getFastMathFlags();
+  std::optional<FastMathFlags> OptionalFMF =
+      ElementTy->isFloatingPointTy() ? std::make_optional(FMFs) : std::nullopt;
 
-  // TODO: Support any-of and in-loop reductions.
+  // TODO: Support any-of reductions.
   assert(
       (!RecurrenceDescriptor::isAnyOfRecurrenceKind(RdxKind) ||
        ForceTargetInstructionCost.getNumOccurrences() > 0) &&
       "Any-of reduction not implemented in VPlan-based cost model currently.");
-  assert(
-      (!cast<VPReductionPHIRecipe>(getOperand(0))->isInLoop() ||
-       ForceTargetInstructionCost.getNumOccurrences() > 0) &&
-      "In-loop reduction not implemented in VPlan-based cost model currently.");
 
-  // Cost = Reduction cost + BinOp cost
-  InstructionCost Cost =
-      Ctx.TTI.getArithmeticInstrCost(Opcode, ElementTy, Ctx.CostKind);
+  // Note that TTI should model the cost of moving result to the scalar register
+  // and the binOp cost in the getReductionCost().
----------------
fhahn wrote:

```suggestion
  // and the BinOp cost in the getReductionCost().
```

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