[llvm] [SelectionDAG] Add initial plumbing for the disjoint flag. (PR #76751)

[Matt Arsenault via llvm-commits]

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@@ -381,6 +381,7 @@ struct SDNodeFlags {
   bool NoUnsignedWrap : 1;
   bool NoSignedWrap : 1;
   bool Exact : 1;
+  bool Disjoint : 1;
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arsenm wrote:

I thought this was unioned with the wrap flags. I guess we don't have enough of these bits to matter yet 

https://github.com/llvm/llvm-project/pull/76751