[llvm] DAG: Gracefully diagnose missing FMA and ppcf128 expansion libcalls (PR #228094)

[Simon Pilgrim via llvm-commits]

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@@ -1646,16 +1649,29 @@ void DAGTypeLegalizer::ExpandFloatRes_ConstantFP(SDNode *N, SDValue &Lo,
   Hi = DAG.getConstantFP(APFloat(Sem, C.extractBits(64, 0)), dl, NVT);
 }
 
+// Diagnose a missing libcall and produce a poison expanded pair.
+void DAGTypeLegalizer::ExpandFloatRes_NoLibcall(SDNode *N, SDValue &Lo,
+                                                SDValue &Hi) {
+  DAG.getContext()->emitError(Twine("no libcall available for ") +
+                              N->getOperationName(&DAG));
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RKSimon wrote:

any chance we can get the type in the error message as well?

https://github.com/llvm/llvm-project/pull/228094