[llvm] [SLP] NFC. Replace TreeEntry::setOperandsInOrder with VLOperands. (PR #113880)

[Han-Kuan Chen via llvm-commits]

================
@@ -8497,20 +8488,13 @@ void BoUpSLP::buildTree_rec(ArrayRef<Value *> VL, unsigned Depth,
                                    ReuseShuffleIndices);
       LLVM_DEBUG(dbgs() << "SLP: added a vector of un/bin op.\n");
 
+      VLOperands Ops(VL, *this);
       // Sort operands of the instructions so that each side is more likely to
       // have the same opcode.
-      if (isa<BinaryOperator>(VL0) && isCommutative(VL0)) {
-        ValueList Left, Right;
-        reorderInputsAccordingToOpcode(VL, Left, Right, *this);
-        TE->setOperand(0, Left);
-        TE->setOperand(1, Right);
-        buildTree_rec(Left, Depth + 1, {TE, 0});
-        buildTree_rec(Right, Depth + 1, {TE, 1});
-        return;
-      }
-
-      TE->setOperandsInOrder();
-      for (unsigned I : seq<unsigned>(0, VL0->getNumOperands()))
+      if (isa<BinaryOperator>(VL0) && isCommutative(VL0))
+        Ops.reorder();
----------------
HanKuanChen wrote:

I don't think it is a good idea. Current `reorder` usage is
```
      if (cast<CmpInst>(VL0)->isCommutative()) {
        // Commutative predicate - collect + sort operands of the instructions
        // so that each side is more likely to have the same opcode.
        assert(P0 == CmpInst::getSwappedPredicate(P0) &&
               "Commutative Predicate mismatch");
        Ops.reorder();
```
```
      if (isa<BinaryOperator>(VL0) && isCommutative(VL0))
        Ops.reorder();
```
```
      if (isCommutative(VL0))
        Ops.reorder();
```
```
      auto *CI = dyn_cast<CmpInst>(VL0);
      if (isa<BinaryOperator>(VL0) || CI) {
        if (!CI || all_of(VL, [](Value *V) {
              return cast<CmpInst>(V)->isCommutative();
            })) {
          Ops.reorder();
```
They use `reorder` when VL0 is commutative. But the last one determine the condition in another way.
Move `reorder` into other place does not make the code neater (the last one still exist).

https://github.com/llvm/llvm-project/pull/113880