[llvm] [WIP][SelectionDAG] Add support for the 3-way comparison intrinsics [US]CMP (PR #91871)

[Nikita Popov via llvm-commits]

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@@ -1246,6 +1251,14 @@ SDValue DAGTypeLegalizer::PromoteIntRes_SADDSUBO(SDNode *N, unsigned ResNo) {
   return Res;
 }
 
+SDValue DAGTypeLegalizer::PromoteIntRes_CMP(SDNode *N) {
+  EVT PromotedResultTy =
+      TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0));
+  SDValue Result = DAG.getNode(N->getOpcode(), SDLoc(N), PromotedResultTy,
+                               N->getOperand(0), N->getOperand(1));
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nikic wrote:

Can directly return here, no need to store in a variable first.

https://github.com/llvm/llvm-project/pull/91871