[llvm] [DAG] Support saturated truncate (PR #99418)

[via llvm-commits]

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@@ -804,6 +804,9 @@ enum NodeType {
 
   /// TRUNCATE - Completely drop the high bits.
   TRUNCATE,
+  /// TRUNCATE_[SU]SAT - Truncate for saturated operand
+  TRUNCATE_SSAT,
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ParkHanbum wrote:

@RKSimon should add that ISD? is it not necessary for unsigned input to signed input?

https://github.com/llvm/llvm-project/pull/99418