[llvm] [SLP] NFC. Make InstructionsState more constant. (PR #118609)

[Alexey Bataev via llvm-commits]

================
@@ -8133,13 +8145,14 @@ void BoUpSLP::buildTree_rec(ArrayRef<Value *> VL, unsigned Depth,
   // a load), in which case peek through to include it in the tree, without
   // ballooning over-budget.
   if (Depth >= RecursionMaxDepth &&
-      !(S.MainOp && isa<Instruction>(S.MainOp) && S.MainOp == S.AltOp &&
+      !(S.getMainOp() && isa<Instruction>(S.getMainOp()) && !S.isAltShuffle() &&
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alexey-bataev wrote:

```suggestion
      !(S.getMainOp() && !S.isAltShuffle() &&
```


https://github.com/llvm/llvm-project/pull/118609