[llvm] [X86]: Reassoc demorgan rule for ANDN (PR #163789)

[via llvm-commits]

kper wrote:

At the moment, there is an infinity loop with `Andnp` for some tests.

```
/// Do target-specific dag combines on X86ISD::ANDNP nodes.
static SDValue combineAndnp(SDNode *N, SelectionDAG &DAG,
                            TargetLowering::DAGCombinerInfo &DCI,
                            const X86Subtarget &Subtarget) {
...

// Folds for better commutativity:
  if (N1->hasOneUse()) {
    // ANDNP(x,NOT(y)) -> AND(NOT(x),NOT(y)) -> NOT(OR(X,Y)).
    if (SDValue Not = IsNOT(N1, DAG))
      return DAG.getNOT(
          DL, DAG.getNode(ISD::OR, DL, VT, N0, DAG.getBitcast(VT, Not)), VT);

// ...
```

Once the demorgan is applied and we have an `ANDNP`, it tries to revert it.
@RKSimon I suppose that I can remove this, right?

https://github.com/llvm/llvm-project/pull/163789