[llvm] [SelectionDAG] Simplify vselect true, T, F -> T (PR #100992)

[Simon Pilgrim via llvm-commits]

================
@@ -3260,26 +3260,10 @@ static SDValue extractBooleanFlip(SDValue V, SelectionDAG &DAG,
   if (V.getOpcode() != ISD::XOR)
     return SDValue();
 
-  ConstantSDNode *Const = isConstOrConstSplat(V.getOperand(1), false);
-  if (!Const)
+  if (!isConstOrConstSplat(V.getOperand(1), false))
----------------
RKSimon wrote:

Move this after the isBoolConstant() check (which does something similar)? It looks like you only need it for the `if (Force)` case now.

https://github.com/llvm/llvm-project/pull/100992