[llvm] [SelectionDAG] Add preliminary plumbing for `samesign` flag (PR #112354)

[Matt Arsenault via llvm-commits]

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@@ -3652,6 +3652,10 @@ void SelectionDAGBuilder::visitICmp(const ICmpInst &I) {
     Op2 = DAG.getPtrExtOrTrunc(Op2, getCurSDLoc(), MemVT);
   }
 
+  SDNodeFlags Flags;
+  Flags.setSameSign(I.hasSameSign());
+  SelectionDAG::FlagInserter FlagsInserter(DAG, Flags);
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arsenm wrote:

This was committed so can do this 

https://github.com/llvm/llvm-project/pull/112354