[llvm] [ValueTracking][X86] Compute KnownBits for phadd/phsub (PR #92429)

[Simon Pilgrim via llvm-commits]

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@@ -36953,6 +36934,34 @@ static void computeKnownBitsForPSADBW(SDValue LHS, SDValue RHS,
   Known = Known.zext(64);
 }
 
+static KnownBits computeKnownBitsForHorizontalOperation(
+    const SDValue Op, const APInt &DemandedElts, unsigned Depth,
+    unsigned OpIndexStart, const SelectionDAG &DAG,
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RKSimon wrote:

Do we still need OpIndexStart?

https://github.com/llvm/llvm-project/pull/92429