[llvm] [DAGCombiner] Add support for scalarising extracts of a vector setcc (PR #116031)

[Matt Arsenault via llvm-commits]

================
@@ -3334,6 +3334,10 @@ class TargetLoweringBase {
     return false;
   }
 
+  /// Try to convert an extract element of a vector setcc operation into an
+  /// extract element followed by a scalar operation.
+  virtual bool shouldScalarizeSetCC(SDValue VecOp) const { return false; }
----------------
arsenm wrote:

I don't see why this needs a special case hook. We already do this for extractelement other_op for the hasOneUse case 

https://github.com/llvm/llvm-project/pull/116031