[DAG] canCreateUndefOrPoison - remove isGuaranteedNotToBeUndefOrPoison check for insert/extract vector element indices (#146514)

No longer necessary now that #146490 has landed

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 4e4e701..6df21b6 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -5640,12 +5640,8 @@
     // Ensure that the element index is in bounds.
     EVT VecVT = Op.getOperand(0).getValueType();
     SDValue Idx = Op.getOperand(Opcode == ISD::INSERT_VECTOR_ELT ? 2 : 1);
-    if (isGuaranteedNotToBeUndefOrPoison(Idx, DemandedElts, PoisonOnly,
-                                         Depth + 1)) {
-      KnownBits KnownIdx = computeKnownBits(Idx, Depth + 1);
-      return KnownIdx.getMaxValue().uge(VecVT.getVectorMinNumElements());
-    }
-    return true;
+    KnownBits KnownIdx = computeKnownBits(Idx, Depth + 1);
+    return KnownIdx.getMaxValue().uge(VecVT.getVectorMinNumElements());
   }
 
   case ISD::VECTOR_SHUFFLE: {