[llvm] [SLP] Partially revert #224931 for alternate nodes (PR #228659)

[Alexey Bataev via llvm-commits]

================
@@ -17908,10 +17908,9 @@ BoUpSLP::getEntryCost(const TreeEntry *E, ArrayRef<Value *> VectorizedVals,
           for (unsigned Idx : seq<unsigned>(1, E->getNumOperands())) {
             TTI::OperandValueInfo ColInfo = getOperandInfo(E->getOperand(Idx));
             if (!RunningInfo.isConstant() || !ColInfo.isConstant())
-              Cost += TTIRef.getArithmeticInstrCost(
-                  Opcode, VecTy, CostKind, RunningInfo, ColInfo, {},
-                  Opcode == E->getOpcode() ? E->getMainOp() : E->getAltOp(),
-                  TLI);
+              Cost += TTIRef.getArithmeticInstrCost(Opcode, VecTy, CostKind,
+                                                    RunningInfo, ColInfo, {},
+                                                    /*CxtI=*/nullptr, TLI);
----------------
alexey-bataev wrote:

```suggestion
                                                    /*CtxI=*/nullptr, TLI);
```

https://github.com/llvm/llvm-project/pull/228659