[llvm] [DAG] computeKnownFPClass - add ISD::EXTRACT_VECTOR_ELT handling (PR #190307)

[Matt Arsenault via llvm-commits]

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@@ -6076,6 +6076,21 @@ KnownFPClass SelectionDAG::computeKnownFPClass(SDValue Op,
     }
     break;
   }
+  case ISD::EXTRACT_VECTOR_ELT: {
+    SDValue Src = Op.getOperand(0);
+    auto *CIdx = dyn_cast<ConstantSDNode>(Op.getOperand(1));
+    EVT SrcVT = Src.getValueType();
+    if (SrcVT.isFixedLengthVector() && CIdx &&
+        CIdx->getAPIntValue().ult(SrcVT.getVectorNumElements())) {
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arsenm wrote:

For this you can just return fcNone for the known class 

https://github.com/llvm/llvm-project/pull/190307