[llvm] [SelectionDAG] Add an ISD node for for get.active.lane.mask (PR #139084)

[Kerry McLaughlin via llvm-commits]

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@@ -5731,21 +5739,24 @@ static inline SDValue getPTrue(SelectionDAG &DAG, SDLoc DL, EVT VT,
                      DAG.getTargetConstant(Pattern, DL, MVT::i32));
 }
 
-static SDValue optimizeIncrementingWhile(SDValue Op, SelectionDAG &DAG,
+static SDValue optimizeIncrementingWhile(SDNode *N, SelectionDAG &DAG,
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kmclaughlin-arm wrote:

I've moved the `isBeforeLegalize` check to before where `optimizeIncrementingWhile` is called from `performActiveLaneMaskCombine`.

https://github.com/llvm/llvm-project/pull/139084