!fixup, Update after merge, using std::array.

After 6dba5f6, we can pass nullopt that prevent wrong cost from the extended
reduction.

Also remove the ArrayRef since the elements will be used after free.

Author: ElvisWang123

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -2417,9 +2417,14 @@ VPExtendedReductionRecipe::computeCost(ElementCount VF,
   auto *SrcVecTy =
       cast<VectorType>(toVectorTy(Ctx.Types.inferScalarType(getVecOp()), VF));
 
+  if (RedTy->isFloatingPointTy())
+    return Ctx.TTI.getExtendedReductionCost(Opcode, isZExt(), RedTy, SrcVecTy,
+                                            getFastMathFlags(), Ctx.CostKind);
+
+  // Cannot get correct cost when quering TTI with FMFs not contains `reassoc`
+  // for non-FP reductions.
   return Ctx.TTI.getExtendedReductionCost(Opcode, isZExt(), RedTy, SrcVecTy,
-                                          RdxDesc.getFastMathFlags(),
-                                          Ctx.CostKind);
+                                          std::nullopt, Ctx.CostKind);
 }
 
 InstructionCost

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -2146,7 +2146,7 @@ expandVPMulAccumulateReduction(VPMulAccumulateReductionRecipe *MulAcc) {
   }
 
   // Generate VPWidenRecipe.
-  ArrayRef<VPValue *> MulOps = {Op0, Op1};
+  std::array<VPValue *, 2> MulOps = {Op0, Op1};
   auto *Mul = new VPWidenRecipe(
       Instruction::Mul, make_range(MulOps.begin(), MulOps.end()),
       MulAcc->hasNoUnsignedWrap(), MulAcc->hasNoSignedWrap(),