[llvm] [DAG] ISD::matchUnaryPredicate / matchUnaryFpPredicate / matchBinaryPredicate - add DemandedElts variant (PR #183013)

[Simon Pilgrim via llvm-commits]

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@@ -3457,7 +3457,10 @@ namespace ISD {
   }
 
   /// Attempt to match a unary predicate against a scalar/splat constant or
-  /// every element of a constant BUILD_VECTOR.
+  /// every element of a constant BUILD_VECTOR. 
+  /// The DemandedElts argument 
+  /// allows us to only collect the  known bits that are shared by the requested 
+  /// vector elements.
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RKSimon wrote:

  /// Attempt to match a unary predicate against a scalar/splat constant or
  /// every element of a constant BUILD_VECTOR.  The DemandedElts argument 
  /// allows us to only collect the  known bits that are shared by the requested
  /// vector elements.

https://github.com/llvm/llvm-project/pull/183013