[llvm] [TableGen] New tblgen Instruction bit to disable DAGISel pattern imports (PR #88382)

[Matt Arsenault via llvm-commits]

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@@ -777,6 +777,10 @@ class Instruction : InstructionEncoding {
   /// SelectionDAG can.
   bit FastISelShouldIgnore = false;
 
+  /// Should DAGISel ignore this instruction. In cases where lowering may
+  /// be done elsewhere or is unneeded, DAGISel may skip over them.
+  bit DAGISelShouldIgnore = false;
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arsenm wrote:

It probably belongs with Pat, I think this is where I got stuck last I looked at doing this

https://github.com/llvm/llvm-project/pull/88382