[llvm] [DAGCombine] Fold setcc_eq infinity into is.fpclass (PR #67829)

[Matt Arsenault via llvm-commits]

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@@ -5064,6 +5064,20 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
       }
     }
 
+    if (isOperationLegalOrCustom(ISD::IS_FPCLASS, N0.getValueType()) &&
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arsenm wrote:

Can you add a DAG comment with the pattern, as is done in most places?

https://github.com/llvm/llvm-project/pull/67829