[llvm] [SelectionDAG] Add expansion for llvm.convert.to.arbitrary.fp (PR #193595)

[Dmitry Sidorov via llvm-commits]

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@@ -7194,6 +7194,48 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
                              SemConst));
     return;
   }
+  case Intrinsic::convert_to_arbitrary_fp: {
+    // Extract format metadata and convert to semantics enum.
+    EVT DstVT = TLI.getValueType(DAG.getDataLayout(), I.getType());
+    Metadata *MD = cast<MetadataAsValue>(I.getArgOperand(1))->getMetadata();
+    StringRef FormatStr = cast<MDString>(MD)->getString();
+    const fltSemantics *DstSem =
+        APFloatBase::getArbitraryFPSemantics(FormatStr);
+    if (!DstSem) {
+      DAG.getContext()->emitError(
+          "convert_to_arbitrary_fp: not implemented format '" + FormatStr +
+          "'");
+      setValue(&I, DAG.getPOISON(DstVT));
+      return;
+    }
+    APFloatBase::Semantics SemEnum = APFloatBase::SemanticsToEnum(*DstSem);
+
+    Metadata *RoundMD =
+        cast<MetadataAsValue>(I.getArgOperand(2))->getMetadata();
+    StringRef RoundStr = cast<MDString>(RoundMD)->getString();
+    std::optional<RoundingMode> RoundMode = convertStrToRoundingMode(RoundStr);
+    if (!RoundMode || *RoundMode == RoundingMode::Dynamic) {
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MrSidims wrote:

Indeed, replaced with assertion (though, may be, even the assertion can be removed).

https://github.com/llvm/llvm-project/pull/193595