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

[Han-Kuan Chen via llvm-commits]

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@@ -1948,6 +1948,9 @@ class BoUpSLP {
 
     /// A vector of operand vectors.
     SmallVector<OperandDataVec, 4> OpsVec;
+    /// When VL[0] is IntrinsicInst, Arg_size is CallBase::arg_size. When VL[0]
+    /// is not IntrinsicInst, Arg_size is User::getNumOperands.
+    unsigned Arg_size;
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HanKuanChen wrote:

For `IntrinsicInst` with more than 2 operands, `VLOperands::appendOperandsOfVL` stores the first two operands but `TreeEntry::setOperandsInOrder` stores all of the operands.
Only the first two operands should be reorder. But all of the operands can be passed into `buildTree_rec`.
If we don't use a new data member (`Arg_size`), either reorder swap non-swappable operands or we need to keep `TreeEntry::setOperandsInOrder`.

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